Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 AM EST Fri Jan 07 2022
Valid 12Z Mon Jan 10 2022 - 12Z Fri Jan 14 2022
...Overview...
The medium range period will begin on Monday with an amplified
upper flow pattern with a trough stemming southward from a deep
upper low over east-central Canada and ridging across the western
U.S. and Canada. A split flow pattern is likely to develop across
the eastern Pacific and West, as a southern stream low drops
southward just west of California through the early part of the
workweek. Meanwhile in the East, the pattern may deamplify
somewhat but rounds of shortwave energy will likely track through
the broader trough axis.
...Guidance/Predictability Assessment...
Reasonably good predictability exists early in the period as model
guidance has remained consistent and agreeable with the deep upper
trough across the East and ridging across the West. Guidance from
the 12Z/18Z (yesterday) cycle also agrees fairly well with the
existence of energy dropping southward through the Pacific and
forming a closed southern southern stream upper low, with
generally similar timing to the previous forecast cycle with it
migrating slowly and staying west of Baja California through early
Wednesday. The incoming 00Z model guidance also shows a similar
idea, though the 00Z CMC has the low staying open for longer. The
upper low/trough may finally get kicked out by Thursday as
additional Pacific energy approaches. However, the evolution of
this energy and additional narrow ridging coming in behind remain
uncertain with quite a bit of ensemble spread, though the recent
GEFS and EC ensemble means do show hints of this shortwave energy
now. At this point, the 12Z ECMWF and CMC and the 18Z GFS (rather
than the 12Z GFS) seemed to have the best agreement with these
features, but with low confidence. Additionally, northern stream
impulses moving through the mean cyclonic flow in the East show
some differences in strength and position especially during the
second half of the week.
Thus for the WPC medium range forecast, used a blend of the
deterministic 12Z ECMWF/CMC and 18Z GFS for the early part of the
period, then phased in some 18Z GEFS and 00Z EC ensemble mean
gradually to about 40% (60% operational models) by the end of the
period. This served to minimize individual forecast differences
but maintain some strength of systems, and provided good
continuity with the previous forecast on days 3-6.
...Weather Highlights...
Drier conditions are likely over much of the contiguous U.S. for
the early part of next workweek as large surface highs influence
the Intermountain West to the central U.S. behind a cold front.
Showers could linger over Florida on Monday as the front passes
through, while generally westerly flow causes lake effect snow
downwind of the Great Lakes especially on Monday, but with the
possibility for additional rounds as the week progresses. The
Pacific Northwest should see periods of precipitation as fronts
approach the area, with higher totals over typical upslope areas
of the Olympics and Cascades. Then moisture may spread ahead of
the upper low in the eastern Pacific into the Southwest.
Precipitation totals are expected to be light in the Southwest,
but could increase into the Southern Plains and Lower Mississippi
Valley by Wednesday and Thursday as the low tracks eastward and
also draws moisture from the Gulf of Mexico. However, confidence
in the details of rainfall amounts is somewhat low and will likely
be refined in future forecast updates.
The next round of arctic air will be in place across the Northern
Plains and Upper Midwest on Monday, with temperatures of 10-25F
below normal and maximum temperatures staying below 0F in some
areas. By Tuesday this chilly air will spread into the
Northeast/Mid-Atlantic in modified form, with high temperatures
10-30F below average for one of the coldest days of the season
thus far. Then, te central U.S. will see a pronounced warming
trend next week with expanding coverage of max/min temperatures
10-20F above normal Tuesday onward with some locally warmer
readings possible on some days. Expect most of the West to see
temperatures within 10F on either side of normal through the
period.
Tate
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