Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
205 PM EST Fri Jan 21 2022
Valid 12Z Mon Jan 24 2022 - 12Z Fri Jan 28 2022
...Overview...
A strong eastern Pacific ridge will help to maintain a broad mean
trough across a majority of the lower 48 through the middle of
next week. Later in the week guidance suggests the overall
pattern may begin to shift a little eastward as Pacific energy
finally nudges the ridge into the western U.S. This pattern will
favor temperatures that are slightly above normal over the West,
variable over the Plains, and mostly below average over the East.
A southern stream wave should produce an area of locally moderate
to heavy rain along/north of the Gulf Coast early in the week
while lighter precipitation spreads across the rest of the eastern
U.S. Otherwise expect precipitation coverage and intensity to be
fairly modest over most of the lower 48.
...Guidance Evaluation/Predictability Assessment...
The primary forecast uncertainties involve shortwave details
within the lower 48 mean trough, and by late in the week specifics
of Pacific energy pushing into the ridge that drifts into the
western U.S. The southern stream shortwave emerging into the
southern Plains early in the week is fairly similar in the
guidance, quickly shearing as it becomes embedded within fast
flow. Some fine-scale surface details that have lower
predictability 4-5 days out in time will still take some time to
be resolved. Meanwhile guidance has been differing for specifics
of one or more shortwaves dropping into the Great Basin/Rockies by
Tuesday onward, with a blend approach looking best given
persistent differences among the models and between consecutive
runs. An intermediate solution appears ideal along the West Coast
by Thursday-Friday. Recent GFS runs through 06Z have been on the
slower/closed side with the Pacific energy (as was the 12Z CMC)
and thus keep more ridging over the West, in contrast to the ECMWF
that has been on the fast/open side with the shortwave. Their
respective ensemble means are less extreme but with a tilt to
their models' relative timing. The means have trended toward a
stronger and faster shortwave over the past couple days, which
would at least favor leaning away from the slow side of the
spread. The new 12Z GFS/CMC have remained slower and closed while
the new 00Z ECMWF has trended slower (albeit straying to the
amplified side of the spread by early Friday), ultimately leading
to better clustering for now.
A 00z/06z operational model blend was effective for most of the
period. Some weighting was offered to the ensembles by day 5 due
to uncertainties with the Southwest shortwave. This weighting was
increased to 60 percent by the end of the period to account for
spread in the deterministics with respect to the incoming Pacific
shortwave.
...Weather Highlights/Threats...
A southern stream system tracking near the Gulf Coast Monday into
Tuesday should produce an area of locally moderate to heavy
rainfall across the far southern tier. Highest totals are likely
be from around eastern Texas into the Lower Mississippi Valley
during Monday-Monday night with a lighter trend farther eastward.
Also early in the week a separate wave/front crossing the East
will spread mostly light to moderate snow from the Great Lakes
into the Northeast. Moisture in the northern periphery of the
southern system interacting with the front may lead to some snow
from the Ohio Valley into central Appalachians and could provide
some enhancement farther northeast as well. Some lake effect snow
will be possible after the system passes by. Another frontal
system reaching the Great Lakes late in the week could bring some
light snow to the region. Aided by low level upslope flow as high
pressure builds into the central U.S., an area of snow will drop
southward through the Rockies and High Plains during the first
half of the week. The rest of the West should be dry except for
possibly some light precipitation reaching the Pacific Northwest
late in the week.
Within the generally cold pattern over the eastern half of the
country, the East Coast will start out chilly on Monday with
Florida and the Northeast most likely to see min and/or max
temperatures at least 10F below normal. The next Arctic surge
will bring readings down to 15-25F below normal over the
Midwest/Upper Mississippi Valley Tuesday into early Wednesday
while well below normal readings spread south and east through the
Plains and eastern U.S. into Thursday with some moderation over
the East by late week. The Plains will see a warming trend
Wednesday-Friday with increasing coverage of plus 10F or greater
anomalies from northern into central areas. Expect the West to
see moderately above normal temperatures next week. Isolated
locations could see plus 10F or so anomalies.
Kebede/Rausch
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