Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 AM EST Thu Nov 07 2019
Valid 12Z Sun Nov 10 2019 - 12Z Thu Nov 14 2019
...Rockies to East Arctic Outbreak Includes a Heavy Snow/Ice
Threat...
...Pattern Overview and Guidance/Predictability Assessment...
The larger scale flow pattern is expected to reamplify next week
with a U.S. West Coast to Alaska ridge and downstream trough over
the central/eastern CONUS. The latest GFS/ECMWF and GEFS/ECMWF
ensemble mean solutions now cluster fairly well for much of the
medium range period, bolstering larger scale flow evolution
confidence.
...Weather Highlights/Threats...
Arctic-sourced high pressure and lead cold front will surge south
from Canada to produce much colder than normal temperatures over
the eastern 3/4 of the lower 48 states this weekend into next
week. The surface high pressure center will tracks from the
Canadian Prairies southeastward to the eastern U.S. next week.
Expect a broad coverage of maximum temperatures 15-25F below
normal and a risk of widespread record cold temperatures will
spread across the central and eastern U.S.
A lead weekend clipper system and trailing cold cyclonic flow will
bring mostly snow to the Great Lakes/Northeast with snows
prolonged into next week by lake effect. Meanwhile, locations
along the eastern slopes of the northern-central Rockies will see
periods of enhanced snows as the trailing Arctic front digs
southward resulting in upslope flow. Organized waves of low
pressure along the front are expected to track along a profound
baroclinic zone from the southern Plains to off the East Coast
Mon-Wed. These will produce a swath of moderate rainfall
along/south of the boundary from across the South and
Southeast/Mid-Atlantic, but also a threat of snow/ice north of the
front in the cold air from the s-central Plains northeastward from
the Mid-South to the OH
Valley/Appalachians/Mid-Atlantic/Northeast. Snows may be
additionally enhanced over the Northeast by coastal storm
development, although there remains uncertainty with coastal
proximity and full extent of wintry onshore impacts. This risk is
depicted in the WPC Winter Weather Outlook probabilities.
There is guidance variance with respect to the handling of
upstream trough energy/heights falls to work through western
Canada and the Northwest U.S. Tue-Thu through an ambient mean
upper ridge. A composite suggests the systems offer modest
precipitation potential focusing over favored terrain of the
Northwest to snowy Rockies.
Schichtel
Additional 3-7 Day Hazards information can be found on the WPC
medium range hazards 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