Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
207 AM EST Tue Feb 01 2022
Valid 12Z Fri Feb 04 2022 - 12Z Tue Feb 08 2022
...Heavy snowfall beginning to exit northern New England by the
start of the medium range period...
...Overview...
A positively tilted and reinforced mean trough aloft should hold
strong across much of the CONUS through the medium range period
(Friday-Tuesday), as strong upper riding builds over both the
western Atlantic and the eastern Pacific (and periodically
extending into parts of the west). On Friday, a shortwave moving
through the Northeast will drive a potent cold front off the East
coast, with potentially heavy wintry precip likely coming to an
end on the north side of this system. Meanwhile, the next
shortwave/possibly brief closed low will weaken as it moves over
the Southern Plains, and combine with energy to the north. This
weekend, uncertainty begins to increase over details of additional
shortwaves dropping down the east side of the ridge in the West
(with some guidance support for a Southwest closed low
Sunday-Tuesday) as well as a series of northern stream shortwaves
which should support a train of northern tier waves into early
next week. Troughing across the East by next Tuesday may induce
low pressure off the East Coast, but most guidance at this time
shows it tracking well enough east for avoid any impacts along the
coast.
...Guidance Evaluation/Predictability Assessment...
A general blend of 12z/18z model guidance from yesterday provided
a good representation of consensus for days 3-4 Friday-Saturday.
In this time frame, frontal waves along the cold front in the East
should consolidate into a single low that ultimately tracks away
from New England while a weak wave and frontal system reach the
northern tier. There remain some minor north-south differences in
cold frontal placement early Friday, but mostly just the typical
run-to-run model fluctuations. The GFS has been consistent the
past several runs in a little farther southward push of the
front/colder air, which ultimately would bring wintry
precipitation farther south into parts of the Mid-Atlantic on
Friday. The last few runs of the ECMWF (including the new 00z run
for today) has been shifting ever so slightly southward though as
well so even though the GFS seems to be a cold outlier right now,
it cannot be completely ruled out.
By this weekend, the greatest point of uncertainty continues to be
with a shortwave dropping into the Northwest and a potential break
off of southern stream energy ultimately resulting in a closed low
lingering over/near the Southwest. The GFS has been very
consistent with a much stronger/deeper closed low, while the rest
of the guidance supports a little bit more consolidation between
northern/southern stream energy through the Rockies into the
Central Plains. At this point, the GFS is a big outlier, but does
have support from some ensemble members (and older runs of the
ECMWF). WPC prefers the weaker solution as offered by the
deterministic ECMWF/CMC and ensemble means, leaning away from the
much too deep GFS.
For northern stream shortwaves/frontal waves, just mainly minor
timing differences through the weekend easily handled by a general
model blend. One point of concern is evolution/interaction of late
period northern/southern stream energy to induce surface low
development off the East Coast. The 12z/yesterday ECMWF brought
this low much closer to the East Coast than most other guidance,
but the 00z run seems to have trended farther offshore again, and
more inline with the ensemble means. Given the increasing late
period detail differences across the board, the WPC forecast
leaned fairly heavily on the ensemble means.
...Weather Highlights/Threats...
Troughing into the Ohio Valley/Northeast on Friday and a leading
wavy cold front through the East will continue the threat for
potentially significant snows across mainly northern New England
on Friday. There likely will be a band of moderate to heavy
sleet/freezing rain just to the south of this in the transition
zone as well, with lingering uncertainties on how far south it
extends (possibly into parts of the Mid-Atlantic). Heavy rainfall
across the South at the end of the short range period will mostly
have ended by Friday morning as the better moisture feed gets cut
off from the Gulf. Some lingering, moderately to locally heavy
showers, are still possible across parts of the Southeast along
the cold front.
Elsewhere, northern tier systems may produce a couple episodes of
light and scattered snowfall. Mostly light rain/mountain snow
should accompany a couple systems brushing the Pacific Northwest
and possibly extending into the northern Rockies. Significant
guidance differences with separate streams of energy aloft lead to
low confidence in the coverage and amounts of precipitation over
the South and East from the weekend into the start of next week.
Some precipitation type issues may come into play depending on how
far north the moisture shield extends.
Areas ahead of the eastern U.S. cold front will continue to see
above average (+10-15F) anomalies for highs, with more anomalous
overnight morning lows on Friday. Arctic high pressure settling
across the central U.S. and into the Midwest behind the front will
bring very cold temps to especially parts of the southern Plains
where daytime highs 20-25 degrees below normal are possible.
Points north and east should be slightly less extreme through
still areas of generally -10-20F highs. Temperatures should
moderate and slide eastward this weekend, with many places east of
the Plains back to near normal values by early next week. Upper
ridging trying to build across the northern/central Plains
Monday-Tuesday of next week could bring a period of much above
normal temperatures to this region. The West Coast states should
be near normal into weekend, trending slightly warmer the rest of
the period owing to amplified ridging across the East Pacific.
Santorelli
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