Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
253 PM EDT Fri Jun 26 2026

Valid 00Z Sat Jun 27 2026 - 00Z Mon Jun 29 2026

...Numerous instances of flash flooding will remain a threat across the
Ozarks vicinity today amongst a broader flash flood threat through the
central/southern Plains to Ohio Valley through tomorrow...

...Scattered to widespread severe thunderstorms forecast tomorrow across
portions of the northern Plains...

...Critical to Extremely Critical fire weather conditions continue over
portions of the Intermountain West into the weekend...

...Heat begins to build over the South into Saturday before a more
widespread expansion into the Plains on Sunday as a dangerous central to
eastern U.S. heat wave begins...

An amplifying pattern will bring a variety of weather hazards across the
country heading into the weekend. Scattered to widespread thunderstorms
continue to develop along a meandering frontal boundary from the
central/southern Plains east through the Ohio/Tennessee Valleys and into
the Carolinas/Mid-Atlantic today (Friday), and will continue into the
weekend. Pooling moisture along the boundary will contribute to locally
heavy downpours with repeated development/movement parallel to the
boundary will support long-duration rainfall/high totals. There is a
Moderate Risk of Excessive Rainfall (ERO) (level 3/4) today across
portions of the MO/KS/AR/OK border region into the Ozarks where numerous
instances of flash flooding can be expected. A Slight Risk (level 2/4) for
more scattered to numerous instances of flash flooding extends westward
over northern Oklahoma and eastward into the Middle Mississippi/Ohio
Valleys. Sufficient instability and flow aloft will also bring the risk of
a few more robust thunderstorms capable of severe weather, with the Storm
Prediction Center (SPC) including a Slight Risk (level 2/5) for the threat
of damaging winds and a few tornadoes. Another Slight Risk ERO is in place
Saturday across portions of the Ohio/Tennessee Valleys where the risk for
scattered flash flooding will continue. There is also a Slight Risk of
severe weather for coastal North Carolina/the Virginia Tidewater as some
damaging wind gusts will be possible. Scattered storm chances will remain
in the forecast into Sunday but become increasingly less notable as an
upper-ridge begins to build overhead.

To the west, an unseasonably strong upper-trough has begun to dig into the
western U.S. bringing much cooler, unsettled weather throughout the
region. A leading upper-wave rounding the trough will lead to deep lee
cyclogenesis and the development/reinforcement of a surface frontal system
over the northern/central High Plains. Scattered thunderstorms are
expected with the SPC maintaining a Slight Risk of severe weather mainly
for some large hail and damaging wind gusts. Increasing upper-flow will
bring a greater threat of severe weather Saturday with an Enhanced Risk
(level 3/5) now in place for the threat of very large hail and significant
damaging wind gusts. The threat will spread further eastward into the
Upper Midwest Sunday with another Slight Risk in place. Locally heavy
rainfall and flash flooding will also be a concern and a Slight Risk ERO
is in place for portions of the northern Plains near the Canadian border
Saturday. Additional showers and thunderstorms are forecast throughout the
Pacific Northwest and into the northern Great Basin/Rockies under the
deepening upper-trough into the weekend. Forecast high temperatures are
upwards of 25-35 degrees below average, with mostly 60s throughout the
Pacific Northwest/coastal California and Interior West, with 80s through
central California and 90s to low 100s in the Desert Southwest. The
unseasonably cool nature of the pattern will even bring some moderate to
heavy snow (4-8"+ accumulations) to portions of the northern Rockies,
generally above 6500 feet. In addition, a dangerous fire weather pattern
will continue over portions of the Great Basin and Four Corners Region
where the SPC has outlooked an Extremely Critical Risk of fire weather
(level 3/3) today with at least a Critical Fire Risk remaining in place
both Saturday and Sunday. Gusty winds with the incoming trough, extremely
low humidity, and very dry antecedent conditions/fuels will contribute to
rapid growth of ongoing fires and the high threat of additional developing
fires.

Meanwhile, an upper-level ridge will begin to build first over the
southeastern U.S. before expanding more broadly over the central to
eastern U.S. this weekend and into early next week. The combination of
high temperatures in the 90s to low 100s and increasing humidity across
the southern Plains/Southeast will lead to expanding areas of Moderate to
Major HeatRisk (levels 2/3 of 4), levels of heat that begin to become a
threat to anyone without adequate access to air conditioning/hydration.
Then, as the ridge expands on Sunday, Moderate to Major HeatRisk will
spread northward across portions of the Plains and Missouri/Mississippi
Valleys. Unfortunately, this will only be the start of an expected
widespread, long-duration, and dangerous heatwave heading into the week
before the July 4th Holiday. Temperatures will be slower to increase north
of the frontal boundary across the Great Lakes/Ohio Valley into the
Northeast, where more pleasant below to around average highs in the 70s
and 80s are expected this weekend, ahead of the heat into next week.
Please see WPC's heat key messages for more details especially beyond the
current short-range forecast period. Elsewhere, scattered thunderstorm
chances are forecast over the southern High Plains and Florida the next
couple of days. Some showers and thunderstorms will remain possible across
New England into Friday night.

Putnam


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
307 PM EDT Fri Jun 26 2026

Valid 12Z Mon Jun 29 2026 - 12Z Fri Jul 03 2026


...Significant, dangerous heat wave expected next week for the
Central to Eastern U.S...


...Pattern Overview...

The pattern during the upcoming medium range looks to be highly
amplified with a strong upper high/ridge over the Eastern half of
the U.S. and a deep trough over the West. This trough will be
reinforced through the period by a series of shortwaves, with snow
possible at the highest elevations of the Northern Rockies
associated with one compact upper low early in the period. In the
East, a sprawling upper high will result in increasingly dangerous
heat and humidity through much of next week (and possibly beyond
into the July 4th Holiday weekend). Showers and thunderstorms will
be most likely across the Gulf Coast/Florida region, the southern
Rockies, and the Upper Midwest to Great Lakes/Northeast.


...Guidance/Predictability Assessment...

The latest guidance maintains good agreement with its depiction of
the large scale pattern through most of the medium range period.
The feature that will continue to have the most predictability is
the large and sprawling 594+dm mid/upper level ridge that will
initially be centered over the Mid-Mississippi Valley early in the
period before slowly shifting eastward into the central
Appalachians by the end of next week. Upstream of this ridge, a
mean mid/upper level trough will drive the pattern across the
Western U.S., with a series of relatively lower predictability
shortwaves reinforcing the trough through most of next week. Given
the above, the WPC forecast was derived using a blend of mostly
deterministic and machine learning guidance through Day 5 before
shifting more weight (60/40 split) to the EC and GEFS ensemble
means for Days 6 and 7. This approach limited the impacts of
smaller scale spatial and temporal differences (mainly with
troughing in the Western U.S.) later in the period while
maintaining continuity with the previous WPC forecast.


...Weather/Hazards Highlights...

The most impactful weather hazard during the medium range period
will be a long lasting heat wave affecting much of the central to
eastern U.S. beginning this weekend and lasting through next week,
and likely into the July 4th Holiday weekend as well. Widespread
temperatures into the 90s to low 100s, combined with high humidity,
will result in heat indices approaching or exceeding 105-110 in
many places. This equates to widespread Major HeatRisk across the
entire region, with areas of extreme HeatRisk in parts of the
Midwest and Ohio Valley underneath the core of the upper high.
Overnight lows will also be quite warm, with some record high
minimums possible, bringing little to no relief from the heat in
the nighttime hours.

Rain and mountain snow will be ongoing into Monday for much of the
Northern Rockies, with several inches of snow accumulation for the
highest mountain ranges. Ahead of this, rain and thunderstorms may
develop across parts of the Upper Midwest and Great Lakes into
Tuesday ahead/north of a lifting warm front through the region.
Some of this activity will likely make its way into parts of the
Northeast by midweek as it rounds the northern periphery of the
mid/upper level ridge. While much of this should be fairly
progressive, moisture anomalies and instability may support a
localized flash flood threat. WPC continues to highlight parts of
the Upper Midwest and the interior Northeast with marginal risks on
the Day 5/Tuesday Excessive Rainfall Outlook.

Elsewhere, moisture funneling between the western trough and the
eastern ridge should support showers and thunderstorms across parts
of the southern Rockies and southern High Plains for at least the
early part of the week. A Marginal Risk ERO has been introduced for
Day 4/Monday and maintained for Day 5/Tuesday to account for any
localized flash flooding concerns. Diurnally driven showers and
storms are also expected from the central Gulf Coast to Florida
with moisture increasing south of the upper ridge.


Santorelli/Miller


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 forecast, excessive rainfall outlook,
winter weather outlook probabilities, heat indices and Key Messages
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
https://www.wpc.ncep.noaa.gov/#page=ovw

Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
308 AM EDT Fri Jun 26 2026

Valid 00Z Sat 27 Jun 2026 - 00Z Sat 04 Jul 2026

The latest model suite remains consistent in showing surface high
pressure remaining centered to the northeast of the Islands
through the upcoming forecast period. There is not expected to be any
significant changes to the trade wind pattern on the south and
southwest side of this high across the Islands, with moderate
trades expected through the forecast period. PW values will
initially be below average through the weekend and into early next
week. Both the GFS and EC then show PW values increasing Tue and
remaining anomalous...2 to 3+ standard deviations above the
mean...through the remainder of next week. Through the forecast
period, climatological trade wind precipitation distribution
expected each day. With increasing PW values, precip values will
likely increase in the favored windward locations from previous
days, with locally heavy 7 day totals in the favored upslope
regions likely.

Oravec

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
419 PM EDT Fri Jun 26 2026
Day 1
Valid 16Z Fri Jun 26 2026 - 12Z Sat Jun 27 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL IN EFFECT FROM
NORTHEAST OKLAHOMA THROUGH SOUTH-CENTRAL MISSOURI...

...Southern Plains to the Mid-Atlantic...

16Z Update...Upgraded to Moderate for northeast Oklahoma, far
southeast Kansas, much of southern Missouri, and extreme northern
Arkansas.

Initial impulse over southeast MO this morning will continue
shifting east to the Mid-Atlantic through tonight. Earlier activity
south of a lingering stationary front has worked over southern
IN for the time being, so an upgrade from Slight is not necessary
there through central WV.

The next impulse is over the KS/CO border and cross KS through this
evening before crossing southern MO overnight. This is the concern
that warranted the upgrade to Moderate. Saturated soils, PW
increasing to around 2" on a robust LLJ tonight, and increasing
instability into the evening. 12Z CAMs are united in a risk for
3-5" rainfall in a few hours from organized activity through the
Moderate area.

Expanded the Marginal east again through the central Mid-Atlantic
where the presence of 70F dew points and maintained instability
overnight near a boundary is often sufficient for prolonged
overnight activity and at least localized flash flooding.

...Montana into North Dakota...

Deep low pressure center shifts from the British Columbia coast to
Washington through tonight with associated shortwave troughing
lifting through Montana. Strong steering flow will keep activity
progressive, but the environment for organized convection with
potential for training exists. Moisture looks sufficient with
precipitable water anomalies of 1.5 sigma above normal. Corridors
of 1-2" rainfall, locally 3" are likely over central MT through
central ND where the Marginal remains in place (expanded west just
a bit in MT).

...Central High Plains...

Increased troughing over the Great Basin promotes return flow up
the High Plains with evening convective activity off the Sangre de
Cristos and Front Range that spills onto the central High Plains
through the night. The risk for repeating cells in a moist
environment with precipitable water anomalies some 1.5 sigma above
climatological average which still warrants a Marginal Risk for
the central High Plains, now connecting to the farther east risk
over south-central KS/western OK.

...Northern New England...

Shortwave low moving through Quebec will allow a trough axis to
swing through New England through this afternoon. Sufficient
instability and mid-level forcing from the disturbance and diurnal
heating should lead to enhanced thunderstorms capable of producing
1-3" of rainfall across northern New England. Repeating activity
could allow localized flash flooding despite moisture being
limited. More of central VT/NH was added with less eastern Maine
based on the 12Z HRRR.

Jackson/Bann


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
419 PM EDT Fri Jun 26 2026
Day 2
Valid 12Z Sat Jun 27 2026 - 12Z Sun Jun 28 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE NORTHERN PLAINS AND A PORTION OF THE OHIO AND TENNESSEE VALLEYS...

...Mid-Mississippi Valley through Southern Appalachians...

Expansion of Slight Risk east to west and north given ongoing heavy
rain along the Mid-Miss/Ohio Valley frontal zone Saturday morning
that then persists into or through the afternoon. Low level
westerly flow remains parallel to this boundary, raising concerns
for repeating/training activity. The 18Z HRRR seems to have a
better handle on activity than the 12Z with final shape of the
Marginal and Slight areas adjusted for its 24hr QPF ending 12Z
Sunday. Decent consensus for areas of 3-5" rainfall near the KY/TN
border with some repeating activity east through the
southern/south-central Appalachians. Depending on progress of
activity, a localized Moderate may be warranted.

...Mid-Atlantic...

Frontal zone now looks to linger over the central Mid-Atlantic
through Saturday night rather than shifting shifting south to the
VA/NC border Saturday evening. This maintains warm sector enhanced
moisture and instability over the DC metros and DelMarVa in
addition to southeast VA and the Outer Banks of NC. The Marginal
Risk was expanded up to the PA/MD line and down through central NC
for waves of heavy thunderstorms expected across these areas
through Saturday night. This still looks to be a localized flash
flood threat, but a focused Slight Risk may be needed eventually.

...Northern Plains...

The upper low tracks over the interior Northwest on Saturday with
shortwave troughing ejecting across northern WY and eastern MT
by Saturday evening. Low level forcing east of the approaching wave
triggers repeating thunderstorms over eastern MT through ND
Saturday afternoon which continue through the evening. Increasing
LLJ that evening should enhance rainfall with the Slight Risk
maintained/expanded west a bit from northeast MT through northwest
ND. Activity should be fairly progressive, but the route of the
upper trough may pivot/allow repeating activity.

Jackson


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
419 PM EDT Fri Jun 26 2026
Day 3
Valid 12Z Sun Jun 28 2026 - 12Z Mon Jun 29 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL IN NORTHWEST
MONTANA AND PORTIONS OF THE UPPER MIDWEST...

...Montana...

Upper low center pivots over Montana Sunday with the surface low
stalling along the MT/Saskatchewan border (aka northeast MT). This
maintains comma head/deformation zone rain shifting into northwest
MT where terrain enhances rates. This is more of an areal flood
concern given a lack of instability, but localized rates may
warrant some rapid flooding concerns where precip bands are most
stagnant. 12Z consensus rainfall is 1-3" on ranges around Glacier
NP onto the adjacent high plains in northwest MT. A marginal risk
has been raised for this area.

...Upper Midwest...

The warm sector of this anomalous low over MT will shift east from
its position on Saturday. The sector will contain robust Gulf
moisture advection up the length of the Great Plains through the
Upper Midwest where a warm front will be lifting. Will hone in on
the main heavy rain threat area with time, but for now a marginal
risk is raised for much of northern MN and northwest WI which is
between the consensus of the better Day 3 sources of guidance, the
CMC regional (RDPS), EC-AIFS, and RRFS. For the 12Z cycle, the RDPS
was the most central of these solutions and was used to draw the
Marginal Risk area. PW anomalies through the Upper Midwest should
be 2 to 2.5 sigma above normal, so where low level convergence
meets the instability gradient a flash flood threat will be
warranted.

Jackson

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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
419 PM EDT Fri Jun 26 2026
Day 4 and Day 5

Valid 12Z Mon Jun 29 2026 - 12Z Wed Jul 01 2026

Day 4

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF WEST TEXAS...

A Marginal Risk was added across portions of West Texas -- from the
Big Bend northward into the Pecos Valley, including the Davis
Mountains. Model signal for at least isolated flash flooding
concerns has increased, with guidance showing deepening moisture
and mid-level energy lifting out ahead of a highly-amplified trough
in the west. While the deterministic models differ on the details,
many, including the GFS and ECMWF, show PW anomalies increasing to
at least 1.5 std dev above normal, along with a slow-moving, low-
amplitude shortwave lifting north out of Mexico. This will likely
raise the threat for at least isolated storms capable of producing
heavy rates and runoff concerns.

Pereira

Day 5

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE
SOUTHERN HIGH PLAINS, UPPER MISSISSIPPI VALLEY/UPPER LAKES REGION
AND ACROSS NORTHERN NY STATE INTO NORTHERN NEW ENGLAND...

2030Z Update...
Made only minor adjustments based on the 12Z guidance.

Pereira

...Northern New York State into Northern New England...
Westerly low level flow expected to strengthen into the frontal
boundary forecast to stretch northwest to southeast from eastern
Ontario into northern NY State and northern New England late Tue
afternoon into Tuesday night. There is potential for organized
convection in the 0000 to 1200 UTC July 1 period along and north of
this boundary. The GFS and EC both show PW values becoming very
anomalous along and just north of this front, with values 2.5-3+
standard deviation above the mean. While there is still a lot of
spread with qpf details at this time range, there is a model signal
for organized convection moving northwest to southeast resulting
in heavy rains and isolated runoff issues.

...Southern High Plains...
PW values expected to rise to 1 to 1.5+ standard deviations above
the mean in the broad southwest mid to upper level flow across the
Southern High Plains on the west side of the Lower MS closed upper
high. Embedded shortwaves in this southwest mid to upper level flow
will support increasingly scattered convection in this high PW
axis, with locally heavy rains and isolated runoff issues.

...Upper MS Valley...
Convection expected to become increasingly active late Tue
afternoon into Tue night/early hours of Wed along and ahead of the
surface front moving slowly across the Upper MS Valley. Favorable
right entrance region jet dynamics ahead of this front in an axis
of above average PW values will support potential for heavy rains
with organized convection along and ahead of this cold front with
isolated runoff issues possible.

Oravec

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
419 PM EDT Fri Jun 26 2026
Day 4 and Day 5

Valid 12Z Mon Jun 29 2026 - 12Z Wed Jul 01 2026

Day 4

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF WEST TEXAS...

A Marginal Risk was added across portions of West Texas -- from the
Big Bend northward into the Pecos Valley, including the Davis
Mountains. Model signal for at least isolated flash flooding
concerns has increased, with guidance showing deepening moisture
and mid-level energy lifting out ahead of a highly-amplified trough
in the west. While the deterministic models differ on the details,
many, including the GFS and ECMWF, show PW anomalies increasing to
at least 1.5 std dev above normal, along with a slow-moving, low-
amplitude shortwave lifting north out of Mexico. This will likely
raise the threat for at least isolated storms capable of producing
heavy rates and runoff concerns.

Pereira

Day 5

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE
SOUTHERN HIGH PLAINS, UPPER MISSISSIPPI VALLEY/UPPER LAKES REGION
AND ACROSS NORTHERN NY STATE INTO NORTHERN NEW ENGLAND...

2030Z Update...
Made only minor adjustments based on the 12Z guidance.

Pereira

...Northern New York State into Northern New England...
Westerly low level flow expected to strengthen into the frontal
boundary forecast to stretch northwest to southeast from eastern
Ontario into northern NY State and northern New England late Tue
afternoon into Tuesday night. There is potential for organized
convection in the 0000 to 1200 UTC July 1 period along and north of
this boundary. The GFS and EC both show PW values becoming very
anomalous along and just north of this front, with values 2.5-3+
standard deviation above the mean. While there is still a lot of
spread with qpf details at this time range, there is a model signal
for organized convection moving northwest to southeast resulting
in heavy rains and isolated runoff issues.

...Southern High Plains...
PW values expected to rise to 1 to 1.5+ standard deviations above
the mean in the broad southwest mid to upper level flow across the
Southern High Plains on the west side of the Lower MS closed upper
high. Embedded shortwaves in this southwest mid to upper level flow
will support increasingly scattered convection in this high PW
axis, with locally heavy rains and isolated runoff issues.

...Upper MS Valley...
Convection expected to become increasingly active late Tue
afternoon into Tue night/early hours of Wed along and ahead of the
surface front moving slowly across the Upper MS Valley. Favorable
right entrance region jet dynamics ahead of this front in an axis
of above average PW values will support potential for heavy rains
with organized convection along and ahead of this cold front with
isolated runoff issues possible.

Oravec

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
154 PM EDT Wed May 6 2026

Valid 00Z Thu May 07 2026 - 00Z Sun May 10 2026

...WPC Winter Weather Desk no longer routinely staffed until
late September, 2026...

Pending any significant winter weather, the WPC Winter Weather Desk
will not be staffed through the summer. The desk will resume
continuous staffing starting in the fall.

The WPC winter products will continue to be produced, however, and
all products except the heavy snow discussion (HSD) will be
available. This includes the Winter Storm Outlook (WSO), Winter
Storm Severity Index (WSSI), and Probabilistic Winter Precipitation
Forecasts (PWPF).


WPC

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
307 PM EDT Fri Jun 26 2026

Valid 12Z Mon Jun 29 2026 - 12Z Fri Jul 03 2026


...Significant, dangerous heat wave expected next week for the
Central to Eastern U.S...


...Pattern Overview...

The pattern during the upcoming medium range looks to be highly
amplified with a strong upper high/ridge over the Eastern half of
the U.S. and a deep trough over the West. This trough will be
reinforced through the period by a series of shortwaves, with snow
possible at the highest elevations of the Northern Rockies
associated with one compact upper low early in the period. In the
East, a sprawling upper high will result in increasingly dangerous
heat and humidity through much of next week (and possibly beyond
into the July 4th Holiday weekend). Showers and thunderstorms will
be most likely across the Gulf Coast/Florida region, the southern
Rockies, and the Upper Midwest to Great Lakes/Northeast.


...Guidance/Predictability Assessment...

The latest guidance maintains good agreement with its depiction of
the large scale pattern through most of the medium range period.
The feature that will continue to have the most predictability is
the large and sprawling 594+dm mid/upper level ridge that will
initially be centered over the Mid-Mississippi Valley early in the
period before slowly shifting eastward into the central
Appalachians by the end of next week. Upstream of this ridge, a
mean mid/upper level trough will drive the pattern across the
Western U.S., with a series of relatively lower predictability
shortwaves reinforcing the trough through most of next week. Given
the above, the WPC forecast was derived using a blend of mostly
deterministic and machine learning guidance through Day 5 before
shifting more weight (60/40 split) to the EC and GEFS ensemble
means for Days 6 and 7. This approach limited the impacts of
smaller scale spatial and temporal differences (mainly with
troughing in the Western U.S.) later in the period while
maintaining continuity with the previous WPC forecast.


...Weather/Hazards Highlights...

The most impactful weather hazard during the medium range period
will be a long lasting heat wave affecting much of the central to
eastern U.S. beginning this weekend and lasting through next week,
and likely into the July 4th Holiday weekend as well. Widespread
temperatures into the 90s to low 100s, combined with high humidity,
will result in heat indices approaching or exceeding 105-110 in
many places. This equates to widespread Major HeatRisk across the
entire region, with areas of extreme HeatRisk in parts of the
Midwest and Ohio Valley underneath the core of the upper high.
Overnight lows will also be quite warm, with some record high
minimums possible, bringing little to no relief from the heat in
the nighttime hours.

Rain and mountain snow will be ongoing into Monday for much of the
Northern Rockies, with several inches of snow accumulation for the
highest mountain ranges. Ahead of this, rain and thunderstorms may
develop across parts of the Upper Midwest and Great Lakes into
Tuesday ahead/north of a lifting warm front through the region.
Some of this activity will likely make its way into parts of the
Northeast by midweek as it rounds the northern periphery of the
mid/upper level ridge. While much of this should be fairly
progressive, moisture anomalies and instability may support a
localized flash flood threat. WPC continues to highlight parts of
the Upper Midwest and the interior Northeast with marginal risks on
the Day 5/Tuesday Excessive Rainfall Outlook.

Elsewhere, moisture funneling between the western trough and the
eastern ridge should support showers and thunderstorms across parts
of the southern Rockies and southern High Plains for at least the
early part of the week. A Marginal Risk ERO has been introduced for
Day 4/Monday and maintained for Day 5/Tuesday to account for any
localized flash flooding concerns. Diurnally driven showers and
storms are also expected from the central Gulf Coast to Florida
with moisture increasing south of the upper ridge.


Santorelli/Miller


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 forecast, excessive rainfall outlook,
winter weather outlook probabilities, heat indices and Key Messages
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
https://www.wpc.ncep.noaa.gov/#page=ovw