Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
238 PM EST Wed Jan 26 2022

Valid 00Z Thu Jan 27 2022 - 00Z Sat Jan 29 2022

...Bitter cold across much of the Northeast tonight before the next surge
of arctic air enters the Upper Midwest on Thursday...

...Snow showers to traverse the Great Lakes and Central Rockies/High
Plains on Thursday near an approaching cold front...

...An area of light snow is forecast to develop over the Mid-Atlantic and
Central Appalachians by Friday afternoon as a coastal storm begins to
organize off the Southeast Coast...

Under an area of high pressure, much of the Northeast and northern
sections of the Mid-Atlantic will be in for another cold night and start
to the day on Thursday. Lows are forecast to dip below zero and into the
single digits for most locations, with teens found farther south into the
Tennessee Valley and southern Virginia. Temperatures will also start below
average across parts of the Lower Mississippi Valley and Southern Plains,
where subfreezing lows are likely. Outside of the Southern Plains, these
temperatures are expected to warm slightly by the end of the week as the
aforementioned area of high pressure weakens and slides off the East
Coast. Meanwhile, the next shot of arctic air is lined up and expected to
drop out of south-central Canada on Thursday. This will lead to below
average temperatures throughout the Upper Midwest/Great Lakes on Friday.

This arctic cold front will also be responsible for scattered snow showers
between Thursday and Thursday night across the Great Lakes. Light snow may
impact parts of the Central Rockies and Central High Plains during this
time frame as well, thanks to a potent upper-level disturbance crossing
the region. However, minimal snow accumulations are forecast. This same
upper-level disturbance is forecast to round the base of a trough located
over the eastern U.S. and spawn a developing coastal storm east of the
Carolinas by Friday night. Light snow may break out across the central
Appalachians and Mid-Atlantic by Friday afternoon, leading to minor snow
accumulations. The majority of the impacts associated with this upcoming
winter storm will likely occur after Friday night.

Elsewhere, chances for scattered showers and thunderstorms will continue
for southern Florida as a stationary boundary linger overs this section of
the country. Light rain may also dampen southern Texas on Friday as a
fast-moving cold front progresses into northern Mexico to end the week.

Snell

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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 PM EST Wed Jan 26 2022

Valid 12Z Sat Jan 29 2022 - 12Z Wed Feb 02 2022

...Coastal winter storm threat from the Mid-Atlantic to especially
New England Friday into the weekend...


...Overview...

Early in the medium range period from Saturday into early Sunday,
a deep upper trough reaching the East Coast will likely close off
an embedded upper low that tracks near the New England coast. The
evolution aloft will support further deepening of strong low
pressure just off the East Coast and direct the system northward,
from east of the Mid-Atlantic coast into the Canadian Maritimes.
This strong coastal storm may cause heavy snow in the coastal
Mid-Atlantic region with higher confidence for heavy snow over the
Northeast, where high winds and coastal impacts are also likely
through the weekend. At the same time a weak eastern Pacific
trough/upper low will cut through the southern part of initial
ridging over the West. From late weekend into next week a more
potent upper trough will push into the West and steadily amplify,
ultimately flipping the upper pattern as a ridge axis reaches the
East Coast by Wednesday. This configuration should lead to a
pronounced increase of precipitation over the central U.S. by the
end of the forecast period.

...Guidance Evaluation/Predictability Assessment...

Model guidance for the most recent couple of cycles continues to
show a rapidly deepening (bomb) cyclone in the western Atlantic
over the weekend, but continues to waffle somewhat with its exact
track, and the relatively fine-scale wobbles can cause notably
different weather impacts. Latest guidance continues to favor an
intermediate/consensus approach for depicting the western Atlantic
storm during the weekend. A significant key to the forecast of the
surface low by late Saturday appears to be exactly when, where,
and how deeply the upper low within the overall trough closes off.
ECMWF runs have been reasonably persistent on the earlier/deeper
side with GFS runs at little later/weaker. Overall the forecast
position for the low on Saturday and Sunday was very similar to
the previous WPC forecast issuance, per the 00Z/06Z model
consensus and taking somewhat of an average position between the
slightly slower EC other faster models. However, incoming 12Z
guidance has shown a slightly eastward/more offshore trend
particularly on Saturday.

Models continue to improve their agreement with the small upper
trough/low moving from the Pacific into the Southwest over the
weekend and the Southern Plains early Monday before weakening as
it heads into a developing mean ridge in the East. However, more
model differences arise with the deeper upstream troughing
expected to dig during the first half of next week in the West.
The general trend in the 00Z/06Z model guidance was a slightly
faster trough axis moving eastward especially by
Tuesday-Wednesday, which pushed the cold front ahead of it faster
than the previous forecast. There is still considerable
uncertainty with the multiple pieces of energy serving to
create/dig this trough, which mainly stem from high
latitude/Pacific regions with low predictability. Of the 00Z model
cycle, the CMC showed some stream separation producing a southern
stream low diving off the coast of California Monday-Tuesday
unlike other guidance. This appeared to be somewhat of an outlier
based on consensus and most individual ensemble members, but the
new 12Z GFS ended up looking quite similar to that 00Z CMC, while
the 12Z CMC ended up without this pattern, closing off a southern
stream low well west in the Pacific as did the incoming 12Z ECMWF.
This is just an indication that though model guidance may indicate
agreement at times, there is still low confidence in the details,
and the forecast still may go through changes with the trough axis
and frontal timing.

A multi-model deterministic blend was used early in the medium
range forecast period, with the 00Z/06Z GFS runs and the 00Z
ECMWF, CMC, and UKMET. Gradually increased the incorporation of
the GEFS and EC ensemble means to about half by the end of the
period given increasing model differences and uncertainty.

...Weather Highlights/Threats...

To start the period Saturday, heavy snow is likely across the
Northeast with possibly some snow lingering in the coastal
Mid-Atlantic region. Latest forecasts show the highest confidence
in heavy snow amounts likely near coastal New England. Significant
coastal impacts are possible in the Northeast, including coastal
flooding and beach erosion. Additionally, strong winds may cause
blowing snow and some damage. Hazardous travel conditions are
likely in parts of the region. See the WPC website for updated Key
Messages on the system and check your local forecast at
weather.gov.

It still appears that the upper trough/low that may track into
California and the Southwest this weekend may be weak enough not
to produce much if any precipitation over that region. Its
strength and track thereafter will determine how much
precipitation may develop from the Gulf Coast northward by the
first part of next week. Over the past day guidance has started to
show some convergence toward the idea of at least some meaningful
rainfall along and north of the western half of the Gulf Coast by
Monday. Moisture ahead of a northeastern Pacific upper trough
should begin to move into the Northwest on Sunday and then
continue to spread across more of the West with time as the upper
trough moves inland and amplifies. Highest totals of rain/mountain
snow should be over the Pacific Northwest, but amounts do not
appear too significant at this time. Toward midweek the western
trough and leading surface front will interact with a healthy flow
of Gulf moisture to produce a rapidly expanding area of
precipitation, some of it potentially becoming moderate to heavy
in the south-central U.S. Lighter wintry precipitation will be
possible over northern latitudes. A series of waves/fronts may
bring episodes of light and scattered snow into parts of the Great
Lakes before the larger scale pattern changes.

The eastern U.S. will be quite chilly through the weekend with
broad coverage of temperatures 10-20F below normal, including
subfreezing lows extending into portions of Florida. Areas from
the Mississippi Valley to Appalachians should see a moderating
trend from west to east. Aside from some below average readings
over Texas and vicinity, much of the Plains will see above average
temperatures from the weekend into next week with readings up to
10-20F or so above normal, locally higher. This warmth will
progress into the eastern half of the country early-mid week with
the increase of Gulf moisture helping to raise min temperature
anomalies in particular by Wednesday. Moderately above average
temperatures over the West during the weekend will trend lower
next week with the arrival of an amplifying upper trough, and
5-15F below normal highs may extend from the Interior West into
the High Plains/northern tier by Tuesday-Wednesday.

Tate/Rausch


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, 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/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
243 AM EST Wed Jan 26 2022

Valid 00Z Thu Jan 27 2022 - 00Z Thu Feb 03 2022

Expect fairly light shower activity through the rest of the week
into the weekend as precipitable water values hover at near or
somewhat below normal levels. A high passing by to the
north/northeast will support moderate to brisk trades and
windward/mountain shower focus on Wednesday. Trades should weaken
later in the week as a front approaches/stalls to the north of the
state, with some potential for sea/land breeze influence on
showers, followed by a rebound over the weekend with passage of
the trailing high.

Some forecast specifics for the early-mid week period remain very
uncertain but at least the spread for potential rainfall amounts
has narrowed somewhat as the GFS/GEFS have trended lower with
moisture/rainfall over the past day. There is still a lot of
model and ensemble spread for exactly what will happen with the
upper trough approaching from the northwest Sunday-Monday, with
GFS runs and some GEFS members continuing to be on the amplified
side of the full envelope. The key today is that the
amplification/sharpening in the GFS is far enough east that the
front moving into the state has less moisture with it.
Interestingly the 00Z ECMWF has jumped to a less amplified version
of the GFS and even closes off a low to the north/northeast of the
islands, so now the ECMWF brings a front through the islands like
the GFS instead of keeping it northwest and maintaining trade
flow. On the other hand the GEFS mean has trended less amplified
aloft and keeps the front farther northwest than before, while the
CMC continues to hold the front to the northwest. So overall
today's mix of guidance has lowered confidence in whether the
front will stay northwest of the main islands or progress
into/through the area, with some intermediate solution favored.
On the other hand, confidence is now better that any increase in
rainfall should not be too extreme.

Rausch

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1002 AM EST Wed Jan 26 2022

Day 1
Valid 16Z Wed Jan 26 2022 - 12Z Thu Jan 27 2022

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

...16Z Outlook Update...
Morning models/CAMs continue to suggest a relatively focused area
of convective potential across south Florida during the day today.
Weak convergence along a east-west oriented frontal boundary will
likely allow for at least a few storms to materialize after about
19-20Z and persist through peak heating. Though convective
orientation relative to deep shear vectors favors some training,
subsidence aloft indicated in models/point forecast soundings and
latest objective analyses cast some doubt on overall storm
coverage. Localized areas of excessive runoff may occur where
downpours occur in sensitive areas, although the overall risk for
flash flooding remains below 5 percent.

Cook/Asherman

...Previous discussion...

A nearly stationary front will be draped across southern Florida
and will provide a focus for showers and thunderstorms throughout
the period. A steady plume of moisture (~1.75 inch PW values) will
return over this west-east boundary, and with diurnal heating, the
convection that does develop may result in locally training
convection possible due to steering flow aloft oriented parallel
to this boundary. With the lack of support of forcing aloft, the
coverage of the convection will be uncertain. Additionally, the
models are varying from about 0.25 inch to 2 inches of QPF over
this area. This trend has not changed much from the previous run.
There may be very isolated downpours that may results in flash
ponding, especially near sensitive areas.

Campbell

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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
314 PM EST Wed Jan 26 2022

Day 2
Valid 12Z Thu Jan 27 2022 - 12Z Fri Jan 28 2022

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Asherman/Campbell


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
314 PM EST Wed Jan 26 2022

Day 3
Valid 12Z Fri Jan 28 2022 - 12Z Sat Jan 29 2022

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Asherman/Campbell

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
327 PM EST Wed Jan 26 2022

Valid 00Z Thu Jan 27 2022 - 00Z Sun Jan 30 2022

...Central Rockies...
Day 1...

A shortwave will dig south out of Alberta Canada around an
amplified but short wavelength ridge centered along the Pacific
coast. This feature will sharpen as it dives towards the Four
Corners Thursday aftn, and will push a decaying front southward
into the Front Range and across the High Plains. The overlap of
height falls, fgen atop the weakening boundary, and modest LFQ
upper diffluence ahead of a polar jet streak will combine to
produce a swath of precipitation from southern WY through CO and
into northern NM. While moisture is somewhat limited, mid-level
deformation collocated with the saturated DGZ will help squeeze
out snowfall, which at times may be briefly heavy as noted by HREF
probabilities for 1"/hr as high as 30%. Total accumulation will be
limited, with WPC probabilities for 4+ inches less than 5%, but
the heavy rates could lead to some impactful accumulations of a
few inches, including along the I-25 corridor and the Palmer
Divide.


...Great Lakes/Northeast...
Days 1-2...

Broad cyclonic flow centered around a mid-level low over the
Hudson Bay will be reinforced by a cold front moving across the
Great Lakes Thursday accompanying a modest shortwave moving
overhead. This front will produce light precipitation along and
ahead of it, with the environment in its wake characterized by CAA
favorable for Lake Effect Snow (LES) in the typical N/NW snow
belts. On Friday, a secondary shortwave with greater intensity
will move across the Lakes driving amplification of the trough
leading to continued CAA but with a more northerly low-level wind
component. This will additionally produce LES, but in the more
northerly-favored belts.

For D1, the heaviest snowfall is likely across the U.P. and
northwest L.P. near Traverse City where WPC probabilities are high
for 2+ inches but low for more than 4 inches, limited by a
relatively shallow DGZ. By D2, LES will become more widespread,
extending downwind of Lake Ontario and Lake Erie, with more
impressive snowfall possible south of Lake Michigan near Gary, IN.
WPC probabilities for 4+ inches are moderate into the Tug Hill
Plateau east of Lake Ontario, as well as into NW Indiana where a
single convergent band may develop along Lake Michigan.


...Southern Appalachians through the Mid-Atlantic...
Days 2-3...

Shortwave energy rounding the expansive eastern CONUS trough will
dig out of the Northern Plains Friday, while southern stream
energy drops through the Four Corners region and towards West
Texas. These features will attempt to phase over the Southeast
Friday night, which when combined with increasing upper diffluence
within the RRQ of an intensifying jet streak arcing into New
England, will drive cyclogenesis off the SC/NC coast. This surface
low is then likely to explosively deepen in response to an
increasingly coupled upper jet structure and the mid-level trough
tilting negatively and closing off. While guidance still features
a wide array of timing/placement solutions, the trend with the
daytime guidance has been for a slightly more eastward track of
the surface low, likely due to a slower ejection of the southern
stream energy shifting out of New Mexico on Friday.

As the low consolidates late Friday into Saturday, moisture will
begin to advect northward as the WCB develops and spreads rich
theta-e air northward and up the coast. At the same time, a cold
front dropping southeast will produce enough ascent to create
light to moderate snowfall across the Appalachians and
Mid-Atlantic late Friday, with some upslope enhancement leading to
the greatest accumulations. WPC probabilities late Friday/Friday
night (D2.5) are 10-30% for 4+ inches in the Southern and Central
Appalachians. Thereafter, the precipitation will become
increasingly dependent on the track of the low with a large shield
of rain and snow shifting northward and westward around the
surface low. This will likely manifest as a corridor of heavy
snowfall within the warm conveyor belt across the eastern
Mid-Atlantic and into New England, with backside deformation
snowfall likely developing down the coast as far as NC in the wake
of the low. Snow rates will likely exceed 1"/hr at times in many
locations, with 2"/hr possible in eastern New England. WPC
probabilities are currently high for 6+" from the DelMarVa
Peninsula northeast through Long Island and into much of eastern
New England. More than 12 inches of snowfall is possible across
eastern MA and coastal ME, including Boston, MA and Portland, ME.
Additional heavy snow is likely beyond this forecast period across
much of Maine Saturday night into Sunday, with the heaviest likely
along the coast.

It should be noted that as well that here has been a shift
eastward today in the guidance, and the WPC PWPF may adjust lower,
especially across inland portions of the region with later updates.


For days 1-3, the probability of significant icing is less than 10
percent.

Weiss


~~~ Key Messages for Jan 28-30 East Coast Winter Storm ~~

- A winter storm is likely to create significant impacts across
New England Friday night through Sunday. Notable impacts may also
extend south along the East Coast through North Carolina.

- Across New England, heavy snow and strong winds are likely which
could lead to blowing snow, scattered power outages, and some
damage. Additionally, significant coastal impacts are possible,
including coastal flooding and beach erosion.

- Farther south from New York City through Washington, D.C., and
into northeast North Carolina, moderate to heavy snow is possible
which could create hazardous travel conditions.

- This forecast continues to evolve. Please check for updates and
your local forecast at weather.gov

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 PM EST Wed Jan 26 2022

Valid 12Z Sat Jan 29 2022 - 12Z Wed Feb 02 2022

...Coastal winter storm threat from the Mid-Atlantic to especially
New England Friday into the weekend...


...Overview...

Early in the medium range period from Saturday into early Sunday,
a deep upper trough reaching the East Coast will likely close off
an embedded upper low that tracks near the New England coast. The
evolution aloft will support further deepening of strong low
pressure just off the East Coast and direct the system northward,
from east of the Mid-Atlantic coast into the Canadian Maritimes.
This strong coastal storm may cause heavy snow in the coastal
Mid-Atlantic region with higher confidence for heavy snow over the
Northeast, where high winds and coastal impacts are also likely
through the weekend. At the same time a weak eastern Pacific
trough/upper low will cut through the southern part of initial
ridging over the West. From late weekend into next week a more
potent upper trough will push into the West and steadily amplify,
ultimately flipping the upper pattern as a ridge axis reaches the
East Coast by Wednesday. This configuration should lead to a
pronounced increase of precipitation over the central U.S. by the
end of the forecast period.

...Guidance Evaluation/Predictability Assessment...

Model guidance for the most recent couple of cycles continues to
show a rapidly deepening (bomb) cyclone in the western Atlantic
over the weekend, but continues to waffle somewhat with its exact
track, and the relatively fine-scale wobbles can cause notably
different weather impacts. Latest guidance continues to favor an
intermediate/consensus approach for depicting the western Atlantic
storm during the weekend. A significant key to the forecast of the
surface low by late Saturday appears to be exactly when, where,
and how deeply the upper low within the overall trough closes off.
ECMWF runs have been reasonably persistent on the earlier/deeper
side with GFS runs at little later/weaker. Overall the forecast
position for the low on Saturday and Sunday was very similar to
the previous WPC forecast issuance, per the 00Z/06Z model
consensus and taking somewhat of an average position between the
slightly slower EC other faster models. However, incoming 12Z
guidance has shown a slightly eastward/more offshore trend
particularly on Saturday.

Models continue to improve their agreement with the small upper
trough/low moving from the Pacific into the Southwest over the
weekend and the Southern Plains early Monday before weakening as
it heads into a developing mean ridge in the East. However, more
model differences arise with the deeper upstream troughing
expected to dig during the first half of next week in the West.
The general trend in the 00Z/06Z model guidance was a slightly
faster trough axis moving eastward especially by
Tuesday-Wednesday, which pushed the cold front ahead of it faster
than the previous forecast. There is still considerable
uncertainty with the multiple pieces of energy serving to
create/dig this trough, which mainly stem from high
latitude/Pacific regions with low predictability. Of the 00Z model
cycle, the CMC showed some stream separation producing a southern
stream low diving off the coast of California Monday-Tuesday
unlike other guidance. This appeared to be somewhat of an outlier
based on consensus and most individual ensemble members, but the
new 12Z GFS ended up looking quite similar to that 00Z CMC, while
the 12Z CMC ended up without this pattern, closing off a southern
stream low well west in the Pacific as did the incoming 12Z ECMWF.
This is just an indication that though model guidance may indicate
agreement at times, there is still low confidence in the details,
and the forecast still may go through changes with the trough axis
and frontal timing.

A multi-model deterministic blend was used early in the medium
range forecast period, with the 00Z/06Z GFS runs and the 00Z
ECMWF, CMC, and UKMET. Gradually increased the incorporation of
the GEFS and EC ensemble means to about half by the end of the
period given increasing model differences and uncertainty.

...Weather Highlights/Threats...

To start the period Saturday, heavy snow is likely across the
Northeast with possibly some snow lingering in the coastal
Mid-Atlantic region. Latest forecasts show the highest confidence
in heavy snow amounts likely near coastal New England. Significant
coastal impacts are possible in the Northeast, including coastal
flooding and beach erosion. Additionally, strong winds may cause
blowing snow and some damage. Hazardous travel conditions are
likely in parts of the region. See the WPC website for updated Key
Messages on the system and check your local forecast at
weather.gov.

It still appears that the upper trough/low that may track into
California and the Southwest this weekend may be weak enough not
to produce much if any precipitation over that region. Its
strength and track thereafter will determine how much
precipitation may develop from the Gulf Coast northward by the
first part of next week. Over the past day guidance has started to
show some convergence toward the idea of at least some meaningful
rainfall along and north of the western half of the Gulf Coast by
Monday. Moisture ahead of a northeastern Pacific upper trough
should begin to move into the Northwest on Sunday and then
continue to spread across more of the West with time as the upper
trough moves inland and amplifies. Highest totals of rain/mountain
snow should be over the Pacific Northwest, but amounts do not
appear too significant at this time. Toward midweek the western
trough and leading surface front will interact with a healthy flow
of Gulf moisture to produce a rapidly expanding area of
precipitation, some of it potentially becoming moderate to heavy
in the south-central U.S. Lighter wintry precipitation will be
possible over northern latitudes. A series of waves/fronts may
bring episodes of light and scattered snow into parts of the Great
Lakes before the larger scale pattern changes.

The eastern U.S. will be quite chilly through the weekend with
broad coverage of temperatures 10-20F below normal, including
subfreezing lows extending into portions of Florida. Areas from
the Mississippi Valley to Appalachians should see a moderating
trend from west to east. Aside from some below average readings
over Texas and vicinity, much of the Plains will see above average
temperatures from the weekend into next week with readings up to
10-20F or so above normal, locally higher. This warmth will
progress into the eastern half of the country early-mid week with
the increase of Gulf moisture helping to raise min temperature
anomalies in particular by Wednesday. Moderately above average
temperatures over the West during the weekend will trend lower
next week with the arrival of an amplifying upper trough, and
5-15F below normal highs may extend from the Interior West into
the High Plains/northern tier by Tuesday-Wednesday.

Tate/Rausch


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, 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/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml