Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
211 AM EST Tue Feb 02 2021
Valid 12Z Fri Feb 05 2021 - 12Z Tue Feb 09 2021
...Major Arctic Outbreak for the Central and Eastern U.S...
...Pattern Overview and Guidance/Predictability Assessment...
The latest medium range models and ensembles offer reasonably well
clustered mid-larger scale guidance. The upper pattern will
highlight an amplified ridge over the eastern Pacific/Alaska and
an amplified longwave trough over central North America. A series
shortwaves will dig to the lee of the ridge to reinforce the mean
trough position. This will allow for a significant intrusion of
Arctic air to overspread and hold a firm grip on much of the
central and eastern U.S.. Shortwave details often prove difficult
to pinpoint at medium range time scales, but offer multiple
opportunities to induce frontal waves and swaths of wintry
precipitation in the widespread cold airmass.
The WPC medium range product suite was accordingly derived from a
composite blend of the 18 UTC GFS/GEFS mean and the 12 UTC
ECMWF/Canadian and ECMWF ensemble mean along with the 01 UTC
National Blend of Models. This solution maintains good WPC
continuity and a composite of latest 00 UTC model and ensemble
guidance still seems in line.
...Weather/Threats Highlights...
A deepening low will organize and lift to the Great Lakes into
Friday. Enhanced snows are expected near and to the north of the
main cyclone track from the windy Midwest/Great Lakes to the
Northeast. A wavy trailing front will focus some showers and
thunderstorms down along the east coast. Meanwhile upstream,
expect a swath of heavy terrain snows from the Northwest to the
north-central Rockies as a potent shortwaves digs over the region.
This energy and subsequent systems will dive into an amplified
central U.S. upper trough position this weekend into next week and
produce periodic swaths of snows. This will correspond with two
main surges of a frigid arctic airmass with much below normal
temperatures with some record values fully southward through the
central then eastern U.S.. Trough and cold air reinforcement will
interact with the lingering wavy front over the Southeast/East to
favor Piedmont/coastal rains and inland snows from the OH
Valley/Appalachians to the Northeast, though there is much
uncertainty with possible coastal storm development from the
Mid-Atlantic to Northeast late in the weekend to early next week,
but the ingredients seem present. There is an emerging guidance
signal that later period energy progression dug into the base of
the mean upper trough early next week may offer potential for an
emerging system/inland precipitation signature out from the
south-central states that could offer a widespread threat of
overrunning snow/ice on the northern periphery of activity.
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, 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