Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
350 PM EDT Fri Aug 12 2022

Valid 00Z Sat Aug 13 2022 - 00Z Mon Aug 15 2022

...Monsoonal moisture to increase the threat for localized heavy rainfall
and flash flooding across parts of the Southwest and Intermountain West...

...Tropical moisture likely to bring heavy rainfall to parts of south
Texas this weekend...

...Much above normal temperatures expected from the northern High Plains
to the central Plains...


What feels like never ending monsoonal moisture, combined with some
embedded upper level impulses, will continue the threat for diurnal
showers and thunderstorms across the Southwest and into the central Great
Basin and northern/central Rockies the next couple of days. Locally heavy
rainfall is possible and WPC has a rather expansive slight risk area on
the Excessive Rainfall Outlooks into Monday across this region. Soils in
some of the area are already overly saturated so its these areas, along
with burn scars and urban communities, that will be most vulnerable to
flash flooding and/or debris flows. To the north, this monsoonal moisture
may also interact with a weak upper level shortwave into the Northwest
today to produce a threat for strong to severe thunderstorms and SPC has a
small slight risk highlighted through tonight across north-central Idaho
and far western Montana.

Elsewhere, a surface low and associated front will drop from the upper
Midwest on Saturday and into the western Ohio Valley on Sunday. Showers
and thunderstorms will accompany this system, with some localized heavy
rainfall possible. Tropical moisture into the Gulf Coast along with a
stationary boundary will allow for daily showers and storms across much of
the Gulf Coast states and into the Southeast. Additionally, a tropical
disturbance in the western Gulf of Mexico will produce enhanced to
potentially heavy rainfall across parts of coastal and south Texas this
weekend.

Upper level ridging will hold strong across the Plains and into the
northern Rockies/interior Northwest resulting in widespread above normal
temperatures. The hottest conditions are expected from northern Montana
into the central Plains where daytime highs Saturday and Sunday could be
in the upper 90s to near 100. Clouds and moisture in the Southwest and
renewed troughing across the East will keep temperatures near or below
normal for this time of the year across those areas into early next week.


Santorelli

Graphics are available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
442 PM EDT Fri Aug 12 2022

Valid 12Z Mon Aug 15 2022 - 12Z Fri Aug 19 2022

...Monsoonal moisture/rainfall threat continues for the Southwest
and Intermountain West/Rockies...

...Heavy rain/Flash Flooding possible across portions of the
Central Plains/Middle Mississippi Valley next Tuesday/Wednesday...

...Excessive heat threat across the South-Central U.S. and
Northwest next week...


...Overview...

An amplified upper flow pattern for next week will feature troughs
over the northeast Pacific and east-central U.S. sandwiched around
a ridge over the West. The ridge will build northward through the
Northwest and western Canada, leading to a threat of excessive
heat, as the northeast Pacific trough shifts slowly eastward
toward the coastline. The ridge and embedded shortwave impulses
will also continue to support widespread monsoonal moisture
streaming underneath into a wet and unsettled Southwest,
Intermountain West, and Rockies through next week. The downstream
digging of shortwaves/height falls to the lee of the ridge will
periodically reinforce upper diffluent flow over a hot
south-central U.S. before feeding into a slow to dislodge
east-northeast U.S. closed low. This low along with modest coastal
low development should support multiple days of rainfall in the
Northeast and allow a break from summer temperatures down through
roughly the eastern half of the nation as a cooling front settles
far down through the east-central U.S. to the South to provide a
multi-day focus for convection with locally heavy rains.


...Guidance Evaluation/Predictability Assessment...

The overall synoptic pattern was captured reasonably well by the
current guidance with some areas of uncertainty. The
trough-ridge-trough setup will tilt farther west as the central
CONUS ridge expands and lifts into the Northwest. This was
resolved fairly well by the suite of deterministic guidance
through day 5 before the 00z EC introduces an anomalous shortwave
trough over the California coast on days 5 and 6, prompting a more
ensemble-centric approach through the rest of next week. A general
model blend of deterministic EC/GFS/UKMET/CMC being used and the
00z EC/UKMET being favored with greater weighting due to their
emphasis on an impactful shortwave impulse rotating through the
Central Plains. This same blend was continued through day 4 before
being diluted a bit with the 00z EC/CMCE and 06z GEFS to help
signal a closed low in the East that was missing in the 00z EC.
Ensembles and the 06z GFS were used on day 6 before ending with
00z ECE favored ensemble blend on day 7. GEFS 06z GEFS members
struggled to agree with the rest of the 00z/06z guidance with
respect to the eastern trough early next week and the
east-northeastern Pacific trough later in next week, as it was
generally a bit deeper.

...Weather/Hazards Highlights...

Portions of the West have seen persistent monsoonal moisture over
the past couple of months, and next week will continue that
pattern as anomalously high moisture streams into the Southwest,
Great Basin, and Rockies in conjunction with small-scale shortwave
energy to produce rain and thunderstorms, particularly in the
afternoon and evening hours. Collaborated WPC experimental Slight
Risks of excessive rainfall are in place for the Central Rockies
for early next week, where there is a viable guidance signal for
heavy convective rainfall rooted by digging shortwave energy/upper
diffluence and terrain lift. The heavy rain focus looks to shift
slowly southward mid-later next week into the Southern Rockies.

There are increasing chances for organized clusters of convection
with heavy downpours to spread through parts of the
Central/Southern Plains and mid-lower Mississippi Valley as the
week progresses. A slight risk of excessive rainfall is in effect
for parts of central-southeastern Missouri next Tuesday.
Elsewhere, the Gulf Coast and into Florida could see scattered
storms with a moist airmass and frontal boundaries. Then as a
surface low is currently forecast to track across the Ohio Valley
through the Mid-Atlantic to the Northeast, organized rains are
forecast for those areas. There's increasing confidence in a
multi-day rain event occurring for much of the coastal Northeast,
from New Jersey up to Maine through mid-week under closed upper
low influence and with near shore track of a coastal frontal low.

Very warm to hot temperatures around 10-15F above average, though
mainly not to record-breaking levels, are forecast across the
Central Plains Sunday into Monday, with a gradually moderating
trend Tuesday onward yielding below normal highs. As the upper
ridge expands into the Northwest, this will warm up temperatures
there and cause highs 10-20F above normal for Tuesday-Thursday.
Meanwhile, below normal highs are expected in the east-central
U.S. behind the cold front, with the most persistent cooler than
average weather in the Ohio and Tennessee Valleys toward the
Mid-Atlantic. Given the rainfall and cloudiness over the Southwest
and Great Basin into the Rockies, highs are likely to be several
degrees below normal there through much of next week.

Kebede/Schichtel

Hazards:
- Heavy rain across portions of the Central Plains, the
Mid-Atlantic, the Lower Mississippi Valley, the Central Great
Basin, the Northern Plains, the Tennessee Valley, the Northern
Rockies, the Central Rockies, the Middle Mississippi Valley, the
Northeast, the Northern Great Basin, the Southern Plains, and the
Ohio Valley, Mon-Tue, Aug 15-Aug 16.
- Heavy rain across portions of the Central Plains, the Central
Rockies, the Central Great Basin, the Southern Rockies, the
Southern Plains, and the Southwest, Mon-Fri, Aug 15-Aug 19.
- Heavy rain across portions of the Southeast, the Lower
Mississippi Valley, the Southern Plains, and the Tennessee Valley,
Wed-Thu, Aug 17-Aug 18.
- Heavy rain across portions of the Northeast, Tue-Wed, Aug 16-Aug
17.
- Flooding occurring or imminent across portions of the Upper
Mississippi Valley.
- Flooding occurring or imminent across portions of the Upper
Mississippi Valley.
- Excessive heat across portions of the Southern Plains, the Lower
Mississippi Valley, the Pacific Northwest, the Northern Rockies,
and the Northern Great Basin, Tue-Fri, Aug 16-Aug 19.
- Excessive heat across portions of the Central Plains, the Middle
Mississippi Valley, the Lower Mississippi Valley, and the Southern
Plains, Mon-Tue, Aug 15-Aug 16.

Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, experimental excessive rainfall
outlook, winter weather outlook probabilities and heat indices are
at:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml

Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
335 AM EDT Fri Aug 12 2022

Valid 00Z Sat Aug 13 2022 - 00Z Sat Aug 20 2022

Guidance overall indicates that the combination of a Pacific
surface high well to the north of Hawaii and a tropical
disturbance passing to the south tightened up the recent pressure
gradients over the state to produce windy trades. This plus a
relatively dry pattern with normal to below normal moisture levels
led to the recent issuance of Red Flag Warnings for leeward
portions of many of the islands and offshore small craft
advisories. As the tropical low pressure moves west and the
surface high weakens into the weekend, trade winds are forecast to
moderate. The relatively dry pattern is forecast to last through
early next week, limiting shower coverage, but some windward and
mauka showers are possible under a general weakness aloft. There
is some chance for tropical moisture to increase by
Tuesday/Wednesday that could fuel a bit more activity, but drier
trade flow may re-emerge later next week.

Schichtel

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
856 PM EDT Fri Aug 12 2022

Day 1
Valid 01Z Sat Aug 13 2022 - 12Z Sat Aug 13 2022

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHWEST, EASTERN GREAT BASIN, AND NORTHERN ROCKIES...

...01Z Update...

The Southwest U.S remains the main focus of concern for excessive
rainfall into the late evening and early-overnight hours given the
persistent deep monsoon remaining in place...with the risk of
excessive rainfall elsewhere across portions of the Great Basin
and Northern/Central Rockies lingering into the evening before
fading with the loss of daytime heating. Rainfall rates have been
greatest from portions of southern Nevada into Arizona given the
best overlap of instability and deepest moisture...and this is the
aread where the risk of excessive rainfall lasts the longest. In
terms of shortterm guidance, the 12/22Z HRRR seems to have a
better handle on the Southwest U.S. convection than previous HRRR
runs. arther to the north and east...the RAP and some higher
resolution guidance suggest 1000 J per kg of CAPE linger into the
03Z to 05Z time frame before diminishing with a corresponding
decrease in the excessive rainfall risk. Felt it was too early to
make too many significant changes.

From the Southeast U.S. along the Gulf Coast, realigned the
northern boundary of the Marginal area to fit latest trends in
radar and satellite imagery. Flash flood guidance in the 1- and
3-hour time frames was 2.5 inches or greater suggesting an
isolated flash flooding threat. The coverage of showers and
thunderstorms over the Lower Gulf coast has the added support of a
weak disturbance...so did not remove the previously issued
Marginal Risk even though the expectation is that convection will
be waning quickly over inland areas.

Across the Upper Midwest...removed portions of the Marginal Risk
area where has already moved out but maintained the risk in parts
of Wisconsin given model-signals for additional rainfall later
tonight. One-hour flash flood guidance in the area is general 1.5
inches and greater...and 3-hour glash flood guidance is generally
2 inches. Rainfall amounts in most areas should fall short of
these thresholds...so little more than a few pockets of excessive
rainfall are expected.

Bann

--16Z Update--

The daytime update includes primarily minor adjustments based on
latest QPF trends from CAM and global guidance. In coordination
with PSR, have expanded the Slight Risk farther west as a
700-500mb inverted trough traverses the Lower Colorado River
Basin. 12Z PSR sounding measured a PW value of 1.86", which is
well above the 90th climatological percentile and in line with the
climatological max moving average. Storm motions will also be
quite slow with forward motions ranging between 5-10 knots. The
latest 12Z HREF 6-hr QPF > 10-year ARI probabilities between
18-00Z this afternoon were as high as 60-70% in some cases along
the Mogollon Rim, highlighting the potential for excessive
rainfall totals in parts of the region. In addition to the endless
supply of anomalous moisture mentioned from overnight, soil
moisture percentiles remain remarkably high throughout the Lower
Colorado River Basin on north into the Great Basin and up to the
Great Salt Lake. NASA SPoRT-LIS 0-40cm soil moisture percentiles
were >98%, indicating soils will struggle to absorb much, if any,
rainfall and lead to instances of rapid runoff. Areas most at risk
for flash flooding are within these overly saturated soils, as
well as within burn scars, slot canyons, dry washes, and urbanized
communities. Elsewhere, backed off the Marginal Risk in southeast
Georgia as CAMs and global guidance have come in drier than
previous forecast cycles.

Mullinax

Previous Discussion...

...Southwest, eastern Great Basin, and northern Rockies...
Little change is expected in the upper pattern, with a strong high
remaining centered over the central High Plains as a upper
low/trough lingers along the Northwest coast. Deep southerly flow
between the two features will support an axis of anomalous
moisture extending from portions of the Southwest through the
eastern Great Basin, into parts of the northern Rockies, with PWs
2-4 standard deviations above normal across the region. This will
continue to fuel daily shower and thunderstorm development and the
potential for heavy amounts. Shortwave energy lifting north along
the western periphery of the ridge is expected to interact with
this moisture, supporting areas of organized convection and
heavier precipitation. This includes areas that have already seen
repeating days of active monsoon convection. Overall, the Slight
and Marginal Risk areas remain largely unchanged from the previous
Day 2 Outlook, with only relatively minor adjustments made to
their footprints based on trends shown by the overnight guidance.

...Gulf Coast to the eastern Carolinas...
Deep moisture ahead of cold front dropping across the Southeast
will continue to support diurnal convection and the potential for
locally heavy amounts today. Across the eastern Carolinas, an
amplifying upper trough and right-entrance region upper jet
forcing is expected to raise the threat for organized
precipitation and heavy amounts. While this area has been quite
dry recently, overnight heavy rains across portions of the area,
along with the potential for additional heavy amounts may warrant
an upgrade to Slight Risk later today. Along the Gulf Coast, deep
moisture (PWs 1-3 standard deviations above normal) and weak
steering flow will continue to support slow-moving storms, capable
of producing heavy rains. Given the wet antecedent soil
conditions that exist from southeastern Louisiana to the Florida
Panhandle, flash flooding will remain a concern across this area.

...Upper Midwest...
Shortwave energy moving off of the top of the ridge is expected to
initiate elevated showers and storms that are forecast to spread
southeast across portions of the region. An initial round
currently developing over eastern North Dakota is forecast to move
across central into southeastern Minnesota later this morning,
with some potential for training and locally heavy amounts. A
second round is forecast to develop tonight into Saturday morning,
impacting areas farther to the east across Wisconsin, with the
models once again showing some signal for training and the threat
for locally heavy amounts.

Pereira



Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
413 PM EDT Fri Aug 12 2022

Day 2
Valid 12Z Sat Aug 13 2022 - 12Z Sun Aug 14 2022

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHWEST, EASTERN GREAT BASIN, INTO THE NORTHERN ROCKIES...

--20Z Update--

Minor adjustments were made to the Marginal and Slight Risk areas
to account for latest 12Z CAMs and global guidance. The Southwest
and Intermountain West look to remain active as 500mb impulses on
the western periphery of an upper level ridge atop the Central
Plains act as a catalyst for widespread thunderstorm development.
AHPS 14-day precipitation totals have ranged as much as 400-600%
of normal from the Lower Colorado River basin on north through he
eastern Great Basin and into northern Utah and western Wyoming.
Farther south, one area of interest is an 850mb low taking shape
in the northwest Gulf of Mexico that should lead to increased
areal extent of thunderstorms in South Texas. There does remain
some spread in guidance regarding timing and rainfall totals, so
have maintained the Marginal Risk inherited from overnight.

Mullinax

Previous Discussion...

...Southwest, eastern Great Basin, and northern Rockies...
Relatively little change is expected in the overall upper pattern
with deep southerly flow continuing to channel both ample moisture
and energy from the Southwest through the eastern Great Basin into
the portions of the northern Rockies. PW anomalies are likely to
remain high across this region (2-4 standardized anomalies above
normal), fueling another day of diurnal convection across the
region as mid-level energy supports areas of enhanced organization
and heavy amounts. With little change in the pattern, the
Marginal and Slight Risk footprints are quite similar to those on
Day 1.

...Gulf Coast to the Carolina Coast...
Boundary dropping in from the north is expected to stall along the
central and eastern Gulf Coast, providing some additional focus
for shower and storm development. With ample moisture remaining
in place and the steering flow weak, the threat for slow-moving
heavy rainfall producers will persist. A few of the overnight
guidance members are quite bullish in the development of an
easterly wave moving across the northwest Gulf, with some models
bring heavy rains onto the lower Texas coast during the period.

...Upper Great Lakes into the Ohio Valley...
Elevated convection developing late in the Day 1 period is
expected to continue into the early part of Day 2, with training
convection moving from northern Wisconsin into northwestern lower
Michigan Saturday morning. While differing on the axis of heavier
amounts, most of the guidance is presenting some signal for
training/backbuilding convection across lower Michigan, raising
the threat for at least locally heavy amounts the potential for
flash flooding across the region on Saturday.

Pereira

Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
414 PM EDT Fri Aug 12 2022

Day 3
Valid 12Z Sun Aug 14 2022 - 12Z Mon Aug 15 2022

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHWEST, EASTERN GREAT BASIN, AND NORTHERN ROCKIES...

--20Z Update--

Contemplated introducing a Slight Risk to South Texas as guidance
as come in wetter compared to recent forecast cycles. Euro ENS
precipitable water percentiles were >90th percentile from Corpus
Christi on south to the Rio Grande and global models showed
improved southerly 850mb moisture flux aimed at the far south
Texas coast. After coordinating with BRO and CRP, opted to wait at
this time due to higher FFGs and AHPS 14-day rainfall around
10-50% of normal. Should consensus in heavier rainfall totals
increase and soils become increasingly saturated after two days of
rainfall, a Slight Risk may be needed in future forecast cycles.
Also contemplated a Slight Risk upgrade in parts of the Ohio
Valley and central Appalachians, but enough spread in guidance was
present to hold off on any Slight Risk upgrade this forecast cycle.

Elsewhere, an almost carbon-copy forecast for Excessive Rainfall
continues in the Southwest and Intermountain West. Euro ENS
precipitable water percentiles remain firmly above the 90th
percentile from the Desert Southwest into the central/northern
Rockies. With rounds of thunderstorms preceding Sunday in these
areas, soils will remain overly saturated throughout much of the
at-risk region. Areas most at risk for flash flooding will be near
burn scars, in rugged terrain, slot canyons, and dry washes.

Mullinax

Previous Discussion...

...Southwest to the northern High Plains...
The story remains much the same into Day 3. With the pattern
remaining largely unchanged, the ERO footprint is largely similar
to the previous days, with the expectation that a persistent axis
of anomalous moisture and energy will support yet another day of
shower and storm development and the potential for heavy amounts
across the highlighted areas.

...Gulf Coast...
Deep moisture accompanying an easterly wave may bring at least
some locally heavy amounts farther west across South Texas this
period. Meanwhile, drier air east of the system is expected to
reduce the threat for heavy rains for some portions of
west-central Gulf Coast. However, farther to the east, easterly
flow will help to maintain deeper moisture and a greater threat
for locally heavy rains from the east-central Gulf Coast into
Florida into Sunday.

...Ohio Valley to the central Appalachians...
Energy originating over the Upper Midwest/Great Lakes on Day 2
will continue to drop south, amplifying an upper trough over the
region. Increasing easterly flow ahead of the associated frontal
boundary is expected to support increasing moisture and the threat
for showers and storms. While widespread heavy amounts are not
expected at this time, locally heavy amounts are possible,
including across some areas that have been recently impacted by
heavy amounts and where soil conditions remain quite moist.

Pereira

Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
309 PM EDT Tue May 10 2022

Valid 00Z Wed May 11 2022 - 00Z Sat May 14 2022

***Regularly scheduled Heavy Snow/Ice Discussions have ended for
the 2021-2022 season from WPC***

--This discussion may be updated over the summer months should the
forecast warrant--

~~Discussions will resume on or around October 1, 2022~~

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
442 PM EDT Fri Aug 12 2022

Valid 12Z Mon Aug 15 2022 - 12Z Fri Aug 19 2022

...Monsoonal moisture/rainfall threat continues for the Southwest
and Intermountain West/Rockies...

...Heavy rain/Flash Flooding possible across portions of the
Central Plains/Middle Mississippi Valley next Tuesday/Wednesday...

...Excessive heat threat across the South-Central U.S. and
Northwest next week...


...Overview...

An amplified upper flow pattern for next week will feature troughs
over the northeast Pacific and east-central U.S. sandwiched around
a ridge over the West. The ridge will build northward through the
Northwest and western Canada, leading to a threat of excessive
heat, as the northeast Pacific trough shifts slowly eastward
toward the coastline. The ridge and embedded shortwave impulses
will also continue to support widespread monsoonal moisture
streaming underneath into a wet and unsettled Southwest,
Intermountain West, and Rockies through next week. The downstream
digging of shortwaves/height falls to the lee of the ridge will
periodically reinforce upper diffluent flow over a hot
south-central U.S. before feeding into a slow to dislodge
east-northeast U.S. closed low. This low along with modest coastal
low development should support multiple days of rainfall in the
Northeast and allow a break from summer temperatures down through
roughly the eastern half of the nation as a cooling front settles
far down through the east-central U.S. to the South to provide a
multi-day focus for convection with locally heavy rains.


...Guidance Evaluation/Predictability Assessment...

The overall synoptic pattern was captured reasonably well by the
current guidance with some areas of uncertainty. The
trough-ridge-trough setup will tilt farther west as the central
CONUS ridge expands and lifts into the Northwest. This was
resolved fairly well by the suite of deterministic guidance
through day 5 before the 00z EC introduces an anomalous shortwave
trough over the California coast on days 5 and 6, prompting a more
ensemble-centric approach through the rest of next week. A general
model blend of deterministic EC/GFS/UKMET/CMC being used and the
00z EC/UKMET being favored with greater weighting due to their
emphasis on an impactful shortwave impulse rotating through the
Central Plains. This same blend was continued through day 4 before
being diluted a bit with the 00z EC/CMCE and 06z GEFS to help
signal a closed low in the East that was missing in the 00z EC.
Ensembles and the 06z GFS were used on day 6 before ending with
00z ECE favored ensemble blend on day 7. GEFS 06z GEFS members
struggled to agree with the rest of the 00z/06z guidance with
respect to the eastern trough early next week and the
east-northeastern Pacific trough later in next week, as it was
generally a bit deeper.

...Weather/Hazards Highlights...

Portions of the West have seen persistent monsoonal moisture over
the past couple of months, and next week will continue that
pattern as anomalously high moisture streams into the Southwest,
Great Basin, and Rockies in conjunction with small-scale shortwave
energy to produce rain and thunderstorms, particularly in the
afternoon and evening hours. Collaborated WPC experimental Slight
Risks of excessive rainfall are in place for the Central Rockies
for early next week, where there is a viable guidance signal for
heavy convective rainfall rooted by digging shortwave energy/upper
diffluence and terrain lift. The heavy rain focus looks to shift
slowly southward mid-later next week into the Southern Rockies.

There are increasing chances for organized clusters of convection
with heavy downpours to spread through parts of the
Central/Southern Plains and mid-lower Mississippi Valley as the
week progresses. A slight risk of excessive rainfall is in effect
for parts of central-southeastern Missouri next Tuesday.
Elsewhere, the Gulf Coast and into Florida could see scattered
storms with a moist airmass and frontal boundaries. Then as a
surface low is currently forecast to track across the Ohio Valley
through the Mid-Atlantic to the Northeast, organized rains are
forecast for those areas. There's increasing confidence in a
multi-day rain event occurring for much of the coastal Northeast,
from New Jersey up to Maine through mid-week under closed upper
low influence and with near shore track of a coastal frontal low.

Very warm to hot temperatures around 10-15F above average, though
mainly not to record-breaking levels, are forecast across the
Central Plains Sunday into Monday, with a gradually moderating
trend Tuesday onward yielding below normal highs. As the upper
ridge expands into the Northwest, this will warm up temperatures
there and cause highs 10-20F above normal for Tuesday-Thursday.
Meanwhile, below normal highs are expected in the east-central
U.S. behind the cold front, with the most persistent cooler than
average weather in the Ohio and Tennessee Valleys toward the
Mid-Atlantic. Given the rainfall and cloudiness over the Southwest
and Great Basin into the Rockies, highs are likely to be several
degrees below normal there through much of next week.

Kebede/Schichtel

Hazards:
- Heavy rain across portions of the Central Plains, the
Mid-Atlantic, the Lower Mississippi Valley, the Central Great
Basin, the Northern Plains, the Tennessee Valley, the Northern
Rockies, the Central Rockies, the Middle Mississippi Valley, the
Northeast, the Northern Great Basin, the Southern Plains, and the
Ohio Valley, Mon-Tue, Aug 15-Aug 16.
- Heavy rain across portions of the Central Plains, the Central
Rockies, the Central Great Basin, the Southern Rockies, the
Southern Plains, and the Southwest, Mon-Fri, Aug 15-Aug 19.
- Heavy rain across portions of the Southeast, the Lower
Mississippi Valley, the Southern Plains, and the Tennessee Valley,
Wed-Thu, Aug 17-Aug 18.
- Heavy rain across portions of the Northeast, Tue-Wed, Aug 16-Aug
17.
- Flooding occurring or imminent across portions of the Upper
Mississippi Valley.
- Flooding occurring or imminent across portions of the Upper
Mississippi Valley.
- Excessive heat across portions of the Southern Plains, the Lower
Mississippi Valley, the Pacific Northwest, the Northern Rockies,
and the Northern Great Basin, Tue-Fri, Aug 16-Aug 19.
- Excessive heat across portions of the Central Plains, the Middle
Mississippi Valley, the Lower Mississippi Valley, and the Southern
Plains, Mon-Tue, Aug 15-Aug 16.

Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, experimental excessive rainfall
outlook, winter weather outlook probabilities and heat indices are
at:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml