Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
132 PM EST Sat Feb 26 2022
Valid 12Z Tue Mar 01 2022 - 12Z Sat Mar 05 2022
...Overview...
Latest guidance continues to show an upper pattern consisting of a
western ridge and broad eastern mean trough through midweek,
followed by a transition toward a mean trough settling into the
western U.S. while upper heights rise farther to the east. The
primary precipitation focus early in the period will be over the
Pacific Northwest and northern Rockies ahead of the eastern
Pacific trough that eventually moves into the West. Progression
of this trough later in the week into next weekend will spread
precipitation over other parts of the West and then bring a
variety of precipitation types to the central U.S. as low pressure
emerges over the Plains. Ahead of this system, expect most
precipitation east of the Rockies to be confined to a couple
episodes of snow across northern areas with associated surface
waves. The pattern evolution will favor above normal temperatures
over a majority of the western/central U.S. through Wednesday or
Thursday and then a cooler trend over the West and warmer readings
over the East.
...Guidance Evaluation/Predictability Assessment...
Overall, the latest 00z/06z suite of models and ensembles
continued to be relatively agreeable on the large scale flow
evolution during the medium range period. There remains some
questions on timing of a few clipper systems within the broader
Eastern U.S. trough. Bigger uncertainties lie with a couple of
incoming shortwaves into the West and then how that trough opens
and broadens over the West late period. The 00z ECMWF is a hair
faster with an initial shortwave into the Pacific Northwest on
Thursday (and also late period with developing low pressure over
the Plains), while the CMC is more amplified. More uncertainty
upstream from this initial wave arise, mainly in the details of
possible compact and embedded closed lows and timing. In general,
the 06z GFS seemed to be the most stable and agreeable to the
ensemble means as the mean trough comes into play across the West.
The WPC blend for todays updated progs used a multi-model
deterministic blend for days 3-4, slowly increasing contribution
from the ensemble means later in the period. Was able to maintain
60 percent deterministic even out to day 7, though with more
weighting on the GFS compared to the ECMWF and CMC. This approach
helps to mitigate the harder to resolve small scale differences
and maintains good continuity from the previous WPC forecast.
...Weather Highlights/Threats...
Moist flow ahead of the upper trough initially over the eastern
Pacific should continue a Pacific Northwest atmospheric river
event already in progress at the start of the period early
Tuesday. Amounts during Tuesday-Wednesday should be somewhat
lower than in the short range at the start of the week but could
still be meaningful at some locations. Some of this moisture will
extend into the northern Rockies. Progression of the upper trough
into the West after midweek should lead to a lighter trend along
the West Coast and spread precipitation into central California
and some other parts of the West, mostly with light to moderate
amounts of rain and higher elevation snow. Expect precipitation
to expand across the central U.S. late week into the weekend as
western trough energy reaches far enough east to support Plains
low pressure. Best potential for some wintry weather will be over
the northern third of the Plains into the Upper Midwest. Areas
from the Upper Midwest into Northeast may see a couple periods of
snow Tuesday-Thursday in association with clipper systems, the
first one fairly well forecast but the second having much greater
uncertainty for strength/track details. Thus confidence is a lot
lower for coverage and amounts of snow with the second system.
Above normal temperatures will prevail over a majority of the
western and central U.S. Tuesday-Wednesday. Progression of the
initial eastern Pacific upper trough will promote a cooler trend
over the West after midweek and then favor northward expansion of
above normal temperatures (plus 10-15F or so anomalies) from the
South across a greater portion of the eastern U.S. Plus 10-20F
anomalies will be possible for max and/or min temperatures for one
or more days over the Great Basin/Southwest through midweek and
parts of the Rockies/Plains into later in the week. Central
Plains locations could exceed plus 20F anomalies for highs. Areas
from the Upper Midwest to the Northeast will tend to be moderately
below normal and colder air filtering into Montana/North Dakota
could bring highs down to 10-20F below normal by next Saturday.
Santorelli/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