Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 PM EST Sat Dec 02 2023

Valid 12Z Tue Dec 05 2023 - 12Z Sat Dec 09 2023

...Heavy rain expected for the Pacific Northwest with an
atmospheric river event continuing into Tuesday and Wednesday...

...Pattern Overview...

A primary concern into next week will be a strong Pacific jet
stream that will be accompanied by an atmospheric river event,
with heavy rainfall pattern expected to continue for the Pacific
Northwest. A building upper ridge axis is expected across the
Intermountain West and then across the Plains going into the
middle of the week with well above average temperatures expected.
Meanwhile, a broad upper trough is forecast to be in place from
the Great Lakes to the East Coast, with a departing storm system
followed by a clipper type system crossing the Upper Midwest and
reaching the Ohio Valley through Wednesday with some snow showers
accompanying it. A more zonal flow pattern aloft likely resumes
after this system exits the East Coast, followed by a potentially
organized storm system over the Southwest to central U.S. into
next weekend.

...Guidance Evaluation/Predictability Assessment...

Model and ensemble forecast spread has improved early-mid next
week in a pattern with seemingly above normal predictability.
Accordingly, the WPC medium range product suite was primarily
derived from a composite of the 06 UTC GFS and 00 UTC
ECMWF/UKMET/Canadian models along with the compatible 13 UTC
National Blend of Models (NBM) and WPC continuity for best detail
Tuesday into Thursday. Newer 12 UTC guidance remains mainly in
line and multi-center ensemble support remains very good in this
period.

Forecast spread increases later next week into next weekend. A
composite blend of best clustered guidance from the 06 UTC
GFS/GEFS mean and 00 UTC ECMWF/ECMWF ensemble mean was preferred
along with the NBM and WPC continuity to attempt to mitigate
growing embedded system differences over time. The most
significant guidance variance in this blend aloft was that the 06
UTC GFS and 00 UTC ECMWF models similarly showed a less
progressive and more amplified southern stream upper trough out
through the Southwest than the GEFS/ECENS means, albeit with a
subset of model matching individual ensemble members. The newer 12
UTC GFS/ECMWF models have now trended more progressive/less
amplified, more in line with the ensemble means.

...Weather/Hazards Highlights...

Out West, precipitation will be ongoing on Tuesday, with a series
of atmospheric rivers into the Northwest lasting into the middle
of the week with earnest, with rising creeks and river levels
expected. Given enhanced rainfall during the weekend and on
Monday, the soils will be more vulnerable and thus the potential
for greater run-off and flooding. Snow levels are initially
expected to be rather high, and therefore western facing slopes of
the Cascades may be subject to an additional risk of flooding due
to snow melt. Therefore, a Slight Risk area remains valid for
western slopes of the Washington Cascades on Tuesday, and also for
the Oregon Coastal Ranges on Tuesday (Day 4). With the
atmospheric river focus most likely weakening some and shifting a
bit more south into Oregon and northwest California on Wednesday,
a Marginal Risk is valid for the Day 5 outlook for far western
Oregon into extreme northwest California. Farther inland across
northern portions of the Intermountain West and Rockies, some
moderately heavy snow is expected into next midweek with the
passage of the next organized system. Some upslope snow showers
are also likely for the higher elevations of the central
Appalachians and vicinity going into midweek as the next low
pressure system passes by.

In terms of temperatures, much of the central and northern Plains
will enjoy late season warmth with highs possibly 20-30 degrees
above early December averages from northeast Colorado to the
Canadian border on Wednesday and into Thursday, with some record
highs within the realm of possibility. The same is expected to
hold true with overnight lows as well across much of the central
and western U.S., with the greatest positive anomalies across
Montana and the Dakotas. Conditions should be close to seasonal
averages for the eastern U.S. for much of the week with no major
arctic air intrusions expected.

Hamrick/Schichtel

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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
148 PM EST Sun Dec 03 2023

Valid 12Z Wed Dec 06 2023 - 12Z Sun Dec 10 2023

...Pattern Overview...

It remains the case tha an amplified upper ridge is expected to be
in place across the central U.S. for the middle of the week, along
with a departing upper trough along the East Coast. The ridge
axis is then expected to flatten out with a quasi-zonal flow
pattern commencing for a brief time across the central and western
U.S. on Thursday. Pacific shortwave energy reaching the West
Coast Thursday night will help build an upper trough across the
western U.S. to close out the work week, and this will now more
rapidly eject eastward across the Plains and spur surface
cyclogenesis into the weekend across the central to east central
U.S.. This will likely result in a well organized storm system
with increasing and enhancing rain and storm chances across the
broad region with frontal system advance/focus, with wrapping
wintry precipitation northwest of the main surface low track.

...Guidance Evaluation/Predictability Assessment...

Model and ensemble solutions seem overall reasonably well
clustered into mid-late week in a pattern with seemingly above
normal predictability. Accordingly, the WPC medium range product
suite was primarily derived from a composite of the best clustered
06 UTC GFS and 00 UTC ECMWF/UKMET/Canadian models along with the
compatible 13 UTC National Blend of Models (NBM) and WPC
continuity for best detail. Newer 12 UTC guidance remains mainly
in line and multi-center ensemble support remains very good in
this period. Forecast spread increases steadily heading into next
weekend, leaning a switch in preference to a blend of best
compatible 06 UTC GEFS/00 UTC ECMWF ensemble means in an effort to
mitigate variance consistent with predictability. WPC product
continuity has trended toward progression across the lower 48 and
vicinity at these long time frames.

...Weather/Hazards Highlights...

There continues to be some good news to report across the Pacific
Northwest with an abatement in the atmospheric river and lesser
rainfall totals going into Wednesday and through the remainder of
the week. There is still a Marginal Risk area of excessive
rainfall from extreme northwest California to the Oregon coastal
ranges and the western Oregon Cascades on day 4 (Wednesday) with
locally 1 to 2 inches of rainfall expected, but this is a
noteworthy improvement compared to the much heavier rainfall
expected during the short term forecast period. Even though
rainfall totals are expected to be lighter, the grounds will be
quite saturated by this time with elevated creeks and rivers, so
there may still be some instances of minor flooding for those
areas. Looking ahead to Day 5 (Thursday), further improvement is
expected for this region and therefore no risk areas are currently
warranted at this time.

A swinging of a now moderately amplified western U.S. trough by
the end of the week will bring moisture across the Intermountain
West and the Rockies, with moderate to heavy snow for
particularily the higher elevations and possible spilling a bit
into the adjacent High Plains with system progression. Farther
south in the warm sector of the low, increasing coverage of
showers and thunderstorms can be expected from the central Gulf
Coast to the Ohio Valley, along with breezy to windy conditions.
This activity looks to become quite expansive over next weekend
over the east-central U.S. and could result in runoff issues over
time.

Pleasantly mild conditions for early December are expected from
the central Plains to the Dakotas and Montana on Wednesday and
into Thursday, with temperatures running 20 to 30 degrees above
average in many cases. The mild conditions then reach the Midwest
by Friday and much of the eastern U.S. for the weekend with
widespread 10-20 degree above average temperatures likely, with
gradually cooling temperatures across the Plains. Colder weather
envelops much of the interior West and Rockies by the weekend in
response to the upper trough/low and increased cloud cover and
precipitation.

Hamrick/Schichtel

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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
202 PM EST Mon Dec 04 2023

Valid 12Z Thu Dec 07 2023 - 12Z Mon Dec 11 2023

...Pattern Overview...

The ridge axis that will be in place across the north-central U.S.
mid-week is expected to flatten out by Thursday while a ridge then
builds across the eastern U.S. to close out the week. Pacific
shortwave energy reaching the West Coast Thursday night will help
build an upper trough across the western U.S. Friday and into
Saturday, and this will then eject eastward across the Plains and
spur surface cyclogenesis over the weekend across the central
Plains. This will likely result in a well organized storm system
tracking northeast towards the Ohio Valley and Great Lakes, with
increasing rain and storm chances ahead of the cold front, and
wintry precipitation northwest of the surface low.

...Guidance Evaluation/Predictability Assessment...

The latest model guidance continues to be in good agreement with
the large scale pattern, allowing for a general model compromise
of the deterministic solutions as a starting point for the days
3-5 forecast. After Day 5/Saturday, there are some minor timing
and strength differences in the trough as it progresses through
the Midwest and East. The ECMWF has been most consistent in
wanting to close off an upper low over the Great Lakes by next
Monday. There are some differences with individual shortwaves
rouding the upper ridge as well, and the 00z CMC is faster and
becomes out of phase with the GFS/ECMWF concerning a shortwave
into the West on Saturday. To mitigate these differences,
incorporated 40 percent of the ensemble means into the blend along
with the GFS/ECMWF days 6-7. Overall, this maintains good
continuity with the previous WPC forecast as well.

...Weather/Hazards Highlights...

The next round of rainfall for the Pacific Northwest is expected
to be considerably lighter on Thursday compared to the ongoing
atmospheric river event in the short range forecast period, and
although some portions of the Oregon coastal ranges may get an
additional inch of rain, it does not appear the intensity nor the
overall totals are currently high enough to merit any excessive
rainfall concerns, although local rivers may still be running
high. Even less precipitation is expected here on Friday, before
the next round of Pacific moisture advects inland next weekend.

The developing western U.S. trough by the end of the week is
expected to result in moisture advecting inland across the
Intermountain West and the Rockies, with widespread moderate to
locally heavy snow for the higher elevations. There may also be
some snow for adjacent portions of the western High Plains as the
low exits the Rockies. Farther south in the warm sector of the
developing surface low, increasing coverage of showers and
thunderstorms can be expected from the central Gulf Coast to the
Ohio Valley, along with breezy to windy conditions. Heavy rainfall
is looking increasingly likely particularly across parts of the
mid-South on Saturday, with the Storm Prediction Center also
highlighting parts of this region for a severe thunderstorm
threat. This storm system should then reach the East Coast by late
Sunday into Monday with widespread rain from the Mid-Atlantic to
New England, with some snow behind the system across the central
and northern Appalachians.

Pleasantly mild conditions for early December are expected from
the central Plains to the Dakotas and Montana on Thursday, with
temperatures running 15 to 30 degrees above average in many cases.
The mild conditions then reach the Midwest by Friday and much of
the eastern U.S. for the weekend with widespread 10-20 degree
above average temperatures likely, with gradually cooling
temperatures across the Plains. Colder weather envelops much of
the interior West and Rockies by the weekend in response to the
upper trough/low.

Santorelli/Hamrick


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
159 PM EST Tue Dec 05 2023

Valid 12Z Fri Dec 08 2023 - 12Z Tue Dec 12 2023

...Pattern Overview...

Guidance shows broadly cyclonic mean flow setting up over the
lower 48 by the weekend into next week. Initially setting up this
pattern will be a vigorous shortwave emerging from the West late
this week, supporting a deepening surface low forecast to track
from the southern Plains through the Great Lakes. This system and
connecting fronts will likely produce significant precipitation
over the eastern third of the country plus a period of brisk to
strong winds from parts of the Rockies eastward. Upstream Pacific
energy feeding into North America, followed by an amplifying
eastern Pacific ridge, should help to reinforce the overall mean
trough early next week but with a more positive tilt that should
lead to more benign weather. Moisture ahead of the Pacific energy
and associated surface system will bring the potential for a brief
period of heavy precipitation over the Pacific Northwest around
Saturday.


...Guidance Evaluation/Predictability Assessment...

Models/ensembles agree in concept on the idea of the leading
trough emerging from the West helping to deepen Plains through
Great Lakes/Canada low pressure from the end of this week into
next Monday. However there is still considerable spread for the
surface low track from the Mississippi Valley onward. Recent GFS
runs and the 00Z UKMET represent the northern or northwestern side
of the spread (12Z UKMET adjusted closer to the middle) while the
12Z CMC now represents the southeastern side of the envelope. Some
ECMWF runs had been on the southern side of the spread but the 00Z
version and the fairly consistent ECens mean are closer to the
middle of the spread. GEFS means lean a bit north in deference to
the operational runs but are a bit less extreme at some forecast
hours. Given the lack of pronounced clustering so far, prefer to
maintain an intermediate solution that provides reasonable
continuity. Behind this system the guidance has made more
noticeable trends over the past day or so, toward a more amplified
eastern Pacific upper ridge by next Tuesday and more downstream
troughing. Also the latest consensus shows Pacific-origin low
pressure reaching the vicinity of the Great Lakes at that time.
The latest guidance through the 00Z/06Z cycles favored an
operational model composite for the first half of the period and
then a transition to include some 06Z GEFS/00Z ECens means by days
6-7 Monday-Tuesday.


...Weather/Hazards Highlights...

After the ongoing atmospheric river event ends in the Pacific
Northwest, there will be a brief break in heavy precipitation on
Friday before another surge of moisture reaches the coast on
Saturday. The region will be sensitive to additional rainfall
after the first event, so Day 5 Excessive Rainfall Outlook
introduced a Marginal Risk of Excessive Rainfall for western
Washington and Oregon into far northwestern California with an
embedded Slight Risk area along the coast. The updated ERO
issuance made only modest adjustment to these areas. In addition
to heavy rainfall, widespread moderate to locally heavy snow will
be possible in the higher elevations of the Cascades and northern
Rockies as moisture pushes inland. Precipitation should quickly
trend lighter after Saturday but with some uncertainty over
specifics.

The surface low that will deepen as it tracks from the southern
Plains into the Great Lakes late Friday into the weekend will
likely produce widespread rainfall from the Gulf Coast up through
the mid-Mississippi Valley and into the Ohio Valley and southern
Great Lakes region. Conditions will be favorable for thunderstorm
development on Saturday from the Gulf Coast to the mid-Mississippi
Valley, and the Storm Prediction Center has highlighted this area
for a severe thunderstorm threat. Meanwhile the Day 5 ERO has
introduced a Marginal Risk of excessive rainfall from parts of the
Lower Ohio Valley south to the Gulf Coast. Moisture anomalies and
instability allow for some enhancement of rainfall, and although
frontal progression may keep totals from becoming too extreme,
rain rates could still be intense for a time to yield the
localized totals that some models are producing. Specifics within
this area will still take time to be resolved though. As the low
pushes northeast on Sunday, precipitation will spread to the East
Coast and up into New England while thunderstorm chances will
decrease. The northern Mid-Atlantic into Northeast will see the
best potential for locally heavy rainfall on Sunday. Some snow
will be possible in the northwestern part of the precipitation
shield, but details are currently uncertain due to lack of
guidance agreement for surface low track. Probabilities for a
quarter inch of liquid in the form of snow are low on an absolute
basis, but what probabilities do exist cover parts of the Midwest
into the Great Lakes. Also some snow may fall after system
passage, mainly over the Great Lakes into Appalachians. Finally,
the gradient around this developing storm will produce a broad
area of brisk to strong winds. The greatest wind threats currently
appear to be behind the storm over portions of the Rockies, but
other areas as far east as the East Coast (including in the warm
sector) should also monitor forecasts for wind speeds. The eastern
U.S. will trend drier after Sunday as high pressure builds into
the South and Mid-Atlantic.

Expect well above normal temperatures in the warm sector ahead of
the developing Plains-Great Lakes system. From Friday into the
weekend, highs should be 10-20F above normal from the Plains into
the East with some morning lows even warmer versus average.
Frontal progression will bring temperatures closer to normal (or
even a little below normal over the southern Plains) over the
central U.S. by the weekend. Above normal readings should be
confined to the Northeast by next Monday. The Intermountain West
and central-southern Rockies will tend to see moderately below
normal highs through the period.

Rausch/Dolan


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
219 PM EST Wed Dec 06 2023

Valid 12Z Sat Dec 09 2023 - 12Z Wed Dec 13 2023

...Pattern Overview...

Guidance shows broad cyclonic mean flow aloft persisting over the
eastern two-thirds of the lower 48 through most of the medium
range period. Initially, a deep upper-level shortwave will emerge
from the West late this week, supporting a wavy surface front that
should cross the eastern half of the country during the weekend
into early Monday. Significant precipitation is likely from the
Gulf Coast to the Great Lakes and into the Northeast as this
system progresses, which could cause flooding concerns. Meanwhile,
the Pacific Northwest will be dealing with another surge of
Pacific moisture on Saturday that may result in scattered
instances of flooding. By next Monday-Wednesday, an amplifying
Pacific into Northwest U.S. ridge will help to reinforce the mean
trough over the East but with a positive tilt that will lead to
more benign weather over most areas. Incoming Pacific energy may
eventually form a trough or upper low over the southwestern states.


...Guidance Evaluation/Predictability Assessment...

The models and ensembles continue to show good general agreement
on the larger scale aspects of the forecast but differ on some
important details. During the weekend, recent guidance runs have
been changing the specifics of how shortwave energy is distributed
within the overall upper trough crossing the eastern half of the
country--leading to differences at the surface. Instead of prior
consensus that had depicted a dominant Plains through Great Lakes
into eastern Canada system, the latest clustering has toned down
the strength of the leading wave crossing the Great Lakes somewhat
but then shows additional frontal wave development over the
Appalachians into New England and southeastern Canada. The scale
of shortwave details involved is small enough to have low
predictability 4-5 days out in time so additional changes are
certainly possible. However the overall pattern evolution
maintains the idea that this system will produce of a broad area
of significant precipitation and potential for some brisk to
strong winds.

Farther upstream, recent trends (minus the 12Z CMC) have been less
amplified and/or farther north with energy that drops into
southern Canada by early next week, leading to a bit of a slower
trend with southward frontal progression over the central U.S. by
next Tuesday. Back toward the West Coast, the models vary
considerably with small-scale/low-predictability shortwave details
that will affect the duration and coverage of significant
precipitation over the Pacific Northwest during the weekend.
Latest CMC runs have been on the deep/slow side of the spread with
its primary shortwave. This leads into the middle of next week
when CMC runs are likewise farthest west with an upper low that
could form over the Southwest/California. Recent trends have been
leaning toward at least some degree of flow separation, though the
closed low has been new enough in the guidance not to go
completely to in the updated forecast based on 00Z/06Z runs. New
12Z guidance (including the GFS/GEFS, albeit with a slight timing
delay) maintains the closed low potential.

A composite of 00Z/06Z operational runs for the first half of the
period followed by incorporating some 06Z GEFS/00Z ECens means
again provides a good reflection of latest guidance ideas with a
combination of continuity or trends depending on the
feature/region. The blend excluded the 00Z CMC late due to greater
differences from consensus.


...Weather/Hazards Highlights...

Expect another surge of Pacific moisture to impact the Pacific
Northwest on Saturday, and the region will be particularly
sensitive to any additional rainfall after receiving significant
rainfall earlier in the week. The Day 4 Excessive Rainfall Outlook
continues to show a Marginal Risk of Excessive Rainfall for
western Washington and Oregon into far northwestern California
with an embedded Slight Risk area along the coast. However note
that most of the new 12Z guidance is reducing the heavy rain
potential in far northwest California. The outlook maintains the
aforementioned areas since this trend is not quite unanimous and
there has been some variability in heaviest axis thus far, but
persistence/consolidation of the trend in the next cycle would
favor a northward adjustment to the southern extent of risk areas.
In addition to heavy rainfall, widespread moderate to locally
heavy snow will be possible in the higher elevations of the
Cascades and northern Rockies as moisture pushes inland.
Precipitation will lighten up across the region thereafter but
with considerable uncertainty over how quickly. The majority of
guidance trends light enough on Sunday to preclude any risk area
for Day 5, but the heavy extreme (via stronger and slower upper
shortwave in the CMC) would have locally significant totals extend
into Sunday. Will continue to monitor guidance for any change to
the current lighter majority cluster.

Some of the wave details have been changing for the front crossing
the eastern half of the country this weekend, but there continues
to be a good signal for this overall system to spread a broad area
of moderate to heavy rainfall from the Gulf Coast to the Great
Lakes and eastward toward the East Coast. The Day 4 Excessive
Rainfall Outlook maintains a Marginal risk area from the Gulf
Coast to parts of the Mid-Mississippi and lower Ohio Valleys,
while Day 5 holds onto a Marginal Risk area from the Florida
panhandle through the Mid-Atlantic and into much of the Northeast.
Primary adjustment in this afternoon's update was to account for a
slightly faster trend in the guidance for both days. The
progressive nature of this system will help to limit rainfall
totals; however, anomalous moisture and sufficient instability
should still support rain rates high enough to produce some
flooding concerns. Current snow cover over parts of the Northeast
could also exacerbate any runoff issues whether it melts before or
during the rainfall event. In addition to potential flooding,
thunderstorms will likely threaten areas along the Gulf Coast and
the Lower Mississippi Valley on Saturday. The Storm Prediction
Center has highlighted an area centered on East Texas and the
Ark-La-Miss where severe thunderstorms are expected. Some snow
will be possible in the northwestern side of the precipitation
shield from the north-central Plains/Midwest into the Great Lakes,
but details remain uncertain due to guidance variability for
surface wave specifics. Some snow may also fall after system
passes, mainly over the Great Lakes into the Appalachians.
Finally, brisk to strong winds are likely to develop over portions
of the Rockies and Plains on Saturday as the pressure gradient
tightens between the wavy front and strong Interior West high
pressure. Strong winds will also be possible in the warm sector
along the Mid-Atlantic into New England coasts Sunday and perhaps
into Monday (northern areas).

Otherwise, parts of the southern Plains and far Southeast
(especially Florida) may see increasing rainfall toward midweek,
aided by moisture beginning to interact with a front and
establishment of moist easterly flow respectively. An approaching
frontal system may bring light precipitation into the Pacific
northwest by next Wednesday.

In terms of temperatures, much of the West will experience below
normal temperatures in the wake of the upper-level shortwave on
Saturday, followed by a rebound to near or slightly above normal
readings late weekend into early next work week and perhaps a
slight decline by midweek. Above to well above normal temperatures
will prevail in the warm sector ahead of the wavy front crossing
the eastern half of the country during the weekend, with
widespread plus 10-25 degree anomalies. A few locations over or
near the northern Mid-Atlantic could challenge daily record highs
on Sunday. Temperatures will return to near normal after the
system passes, aside from some below normal highs near the Gulf
Coast and moderately above normal readings over the
northern/central Plains early next week.

Rausch/Dolan


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