Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
159 AM EST Sun Feb 27 2022
Valid 12Z Wed Mar 02 2022 - 12Z Sun Mar 06 2022
...Overview...
Expect a significant change in the upper level pattern over the
course of the period, with a western U.S. ridge/broad eastern
trough as of Wednesday transitioning toward an amplified northern
Plains through western U.S. trough/eastern ridge configuration by
next weekend. As this evolution occurs, precipitation over the
Pacific Northwest and northern Rockies will spread across more of
the West, to be followed by a broad area of various precipitation
types developing over the central U.S. as low pressure tracks
through the Plains and Upper Great Lakes. Early in the period a
northern tier wave may spread some snow across areas from the
Upper Midwest into the Northeast. Western/central states will see
a pronounced cooler trend in temperatures, from well above normal
to below normal, while above normal temperatures over the southern
half or so of the East should expand northward next weekend. Far
northern tier areas will tend to be colder than normal on most
days.
...Guidance Evaluation/Predictability Assessment...
The latest cycles of guidance maintain the recent theme of better
than average agreement for the large-scale pattern evolution but
continued differences for some details. Subtle differences in
evolution of southern Canada energy flowing into/through the
eastern North America mean trough continue to produce greater than
average spread for the specifics of a surface wave that may track
from the Midwest through the Northeast from Wednesday into early
Thursday. CMC/UKMET runs have consistently been on the stronger
and northern side of the model spread for this wave. The notable
change in the past day has been with the 00Z GFS/GEFS mean
trending to a slower/weaker version of the CMC/UKMET scenario,
extending a modest trend from the 18Z cycle. This leaves the 12Z
ECMWF still the new 00Z run on the weak and suppressed side of the
spread. The preferred solution adjusted the wave's track somewhat
northward from previous cycle given relative support from the
means but maintained a fairly weak depiction due to the
considerable spread.
Meanwhile guidance is still in the process of refining the
forecast of upper troughing that moves into the West. 00Z runs so
far are adding support to the idea of a slightly slower/sharper
lead shortwave reaching the West Coast, leaving the 12Z
ECMWF/ECMWF mean a bit on the faster side. The new 00Z ECMWF has
adjusted slower. This energy should ultimately cross the West and
eject through the Plains, supporting a Plains through Upper Great
Lakes surface system from late week through the weekend.
Consistent with trends seen farther west, this system has adjusted
a little slower over the past day. Low-predictability trailing
energy dropping into the mean trough (as eastern Pacific ridging
steadily builds) continues to complicate the forecast of the
leading impulse to some degree. Still, there is better than
average agreement regarding the fairly deep trough forecast to be
over the West as of day 7 Sunday.
The 12Z/18Z operational model blend used for the first half of the
period provided the desired adjustment for the eastern U.S. wave
while representing an intermediate solution for the shortwave
entering the West. Then a trend toward more even weight of models
and ensemble means later in the period accounted for the good
pattern agreement but uncertainty in some of the details.
...Weather Highlights/Threats...
Rain and high elevation snow from the Pacific Northwest/northern
California into northern Rockies as of midweek will spread across
more of the West later in the week, while trending lighter along
the West Coast, as an upper trough moves into and through the
region. Continued progression of this energy should support a
central Plains into Upper Great Lakes surface low and frontal
system late week into the weekend, with a corresponding broad area
of precipitation over the central U.S. Best potential for wintry
precipitation types will extend from the northern half of the High
Plains into the Upper Great Lakes and eventually New England, with
a band of significant snow possible to the northwest of the
surface low track. Rainfall of varying intensity will be possible
over the rest of the central/east-central U.S. Well ahead of this
system, a northern tier wave may spread snow across an area from
the Upper Midwest into New England from Wednesday into Thursday.
Thus far guidance has not been agreeable with details of the
surface wave so coverage and amounts of snow have lower than
average confidence. A lower-probability scenario could lead to a
somewhat farther southward axis.
A majority of the lower 48 will see above normal temperatures on
Wednesday, with areas along the central/eastern Canadian border as
well as the western Gulf Coast being the main exceptions. Then
the West and northern-central Plains will trend steadily cooler
with time while above normal readings over the southern half of
the East expand northward by next weekend. Expect the warmest
anomalies of plus 20-25F or so for highs to be over the central
Plains Wednesday through Thursday or Friday. Other warm areas may
see plus 10-20F anomalies with some locally higher readings
possible. Northern Plains into Rockies locations may see highs
10-15F below normal by next Sunday.
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