Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
152 PM EST Wed Jan 05 2022
Valid 12Z Sat Jan 08 2022 - 12Z Wed Jan 12 2022
...General Pattern Overview...
An amplified but progressive upper level pattern should prevail
into the start of next week with a deep trough tracking from the
Rockies to the East Coast and a ridge axis moving into the western
U.S. from the eastern Pacific. By early-mid week the pattern
should transition somewhat as eastern Pacific shortwave energy
splits around the western U.S. ridge--leading to a possible
southern stream trough reaching the southwestern U.S. and far
northwestern Mexico--and a flatter trend to the mean flow across
the eastern half of the country. The main precipitation event
during the period will be an area of locally moderate to heavy
rainfall over parts of the South/Tennessee Valley this weekend,
aided by moist flow ahead of a cold front. Another surge of cold
air will spread across the northern Plains through the Upper
Midwest Sunday into the first part of next week, followed by a
warmer trend over the central U.S.
...Guidance/Predictability Assessment...
Guidance continues to be well-behaved in terms of agreement and
continuity for about the first half of the period when the Pacific
into western U.S. upper ridge and downstream trough are dominant
and large-scale features. Likewise forecasts for the cold front
ahead of the upper trough are fairly consistent. A blend of
00Z/06Z operational models reflected consensus well for this part
of the forecast. Then models and ensemble members continue to
vary for specifics of how eastern Pacific shortwave energy may
split as it nears the West Coast. These differences ultimately
affect flow over/near the Southwest as well as locations east of
the Rockies, with northern stream flow determined in part by how
Pacific energy goes around the western U.S. ridge and southern
tier flow influenced by the pattern to the west. For this more
uncertain part of the forecast, transitioning to a blend of models
and GEFS/ECMWF means helped to keep the overall evolution fairly
stable with only modest refinements in detail.
...Hazards/Sensible Weather Highlights...
Gulf moisture advecting northward ahead of a developing
Plains/Midwest cold front will support increasing coverage of
showers and thunderstorms from eastern Texas and the central Gulf
Coast to the Ohio Valley and Mid-Atlantic region this weekend,
with lighter rainfall expected farther north. There will likely
be some embedded heavier rainfall across portions of the Deep
South where convection is persistent. Areas from the upper Great
Lakes to the Northeast could see wintry weather, with the best
snowfall prospects over northern New England and northern New
York. Freezing rain and/or sleet may be among the hazards over
and near parts of the northern half of the Appalachians for a time
as moisture overruns cold air at the surface. Parts of the Great
Lakes may see lake effect snow behind the passing front. Dry
conditions will likely prevail over a majority of the lower 48
during the first half of next week. Exceptions include some
showers and mountain snow over western Washington and Oregon as
one or more systems brush the region and some precipitation
spreading into the Southwest and southern Plains. Precipitation
amounts will be sensitive to the exact details of the upper trough
approaching/reaching the Southwest.
On Saturday the Plains/Midwest will see some moderation of the
severe cold before the next arctic surge reaches into the northern
tier states by Sunday into Tuesday morning. The second surge may
not be quite as intense as what is expected for the end of this
week, but temperatures could still be 10-25F below normal from
eastern Montana to Wisconsin. The cold air will eventually reach
the East Coast as well, bringing highs down to 10-25F below normal
from the Mid-Atlantic through New England on Tuesday. From
Saturday into Sunday above normal temperatures will progress from
the southern Plains to the Deep South and Southeast U.S. Greatest
anomalies should be for overnight lows 15-25 degrees above normal
across the central Gulf Coast region Sunday morning. The
northern-central Plains will trend warmer next week, reaching
10-15F or so above normal over some locations by
Tuesday-Wednesday. Seasonably cold conditions are likely west of
the Continental Divide with readings generally within 10 degrees
of climatological averages.
Rausch/Hamrick
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