Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
159 AM 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 flooding 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...
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. In general GFS
runs have tended to be a little later/weaker with the upper low
while the 12Z ECMWF is somewhat on the earlier/deeper side. The
12Z ECMWF scenario brings the surface track back to the west for a
brief time, which a number of ECMWF ensembles have also been
doing. The 00Z CMC has a less pronounced and farther north
depiction of this idea. The new 00Z ECMWF has adjusted east with
the surface low toward the longer-term consensus due to a slightly
weaker upper low. This is a very fine-scale detail and the
supporting energy is still over northwestern North America so it
may take additional time to resolve specifics with reasonable
satisfaction.
For the upper trough moving into the West, the forecast of leading
energy has become more uncertain in the new 00Z cycle as models
show varying ways in which some of the energy in the shortwave may
get pulled off to the southwest--leading to meaningful differences
in amplitude as the remaining energy reaches the West Coast. On
the other hand, guidance from the 12Z cycle onward seems to have
come into better agreement for the pattern from the North Pacific
through Alaska and Siberia. This has in turn helped to narrow the
spread somewhat for the larger scale upper trough amplifying into
the West during the first half of the week.
Models are slowly improving their agreement with respect to the
weak upper trough/low moving into the Southwest during the weekend
and continuing along the southern tier before weakening as it
heads into a developing mean ridge in the East. General trends by
the time the feature reaches the Plains have been more in the
direction of the southern ECMWF versus some earlier northern GFS
runs.
The updated forecast started with a blend of 12Z models, with
minor manual enhancement of the western Atlantic storm. The 12Z
GFS compared slightly better in concept to other guidance versus
the 18Z run. Meanwhile the model blend accounted for the most
common ideas for the arriving western trough as of the 12Z/18Z
cycles. By later in the period an average of recent operational
model runs has fairly good support from the GEFS/ECMWF means for
the amplifying western trough, so even by days 6-7
Tuesday-Wednesday the forecast included only 30 percent total
ensemble mean weight.
...Weather Highlights/Threats...
Key Messages for January 28-30 (Friday-Weekend) Winter Storm:
Confidence is increasing that a significant winter storm will
create considerable impacts Friday through the weekend from the
Mid-Atlantic through the Northeast. Heavy snow is most likely in
parts of New England. Heavy snow is still possible farther south
along the East Coast, including the major I-95 metropolitan areas
from New York City to Washington D.C., but that is more uncertain
at this time. 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.
Please continue to monitor for updates, and check your local
forecast at weather.gov.
Other Weather Highlights:
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.
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 normal readings
over Texas and vicinity, much of the Plains will see above normal
temperatures from the weekend into next week with readings up to
10-20F or so above normal. 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 normal 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.
Rausch/Tate
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