Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
159 AM EST Tue Mar 01 2022
Valid 12Z Fri Mar 04 2022 - 12Z Tue Mar 08 2022
...Heavy snow potential over the Upper Midwest/Great Lakes and
possibly into northern New England during the weekend...
...Heavy rainfall potential from the Mid-Lower Mississippi Valley
into Tennessee/Ohio Valleys late weekend into early next week...
...Overview...
Models and ensemble means continue to show the establishment of a
positively tilted mean trough aloft from Canada into the western
U.S., between a building eastern Pacific ridge and another ridge
that migrates across the Gulf of Mexico into the Bahamas. A
leading impulse reaching the West by the start of the period early
Friday and another feature arriving close behind will bring
precipitation to portions of the West, followed by a broad area of
precipitation to the east of the Rockies as two potential systems
track into the Great Lakes/Ohio Valley. The first system should
bring greater snowfall potential to the Upper Midwest/Upper Great
Lakes and to some degree northern New England. Most guidance
shows a second system developing along the trailing front whose
slow movement due to alignment with southwesterly mean flow aloft
late weekend into early next week could make it a focus for
significant rainfall farther south. Below normal temperatures
will settle over much of the western and central U.S. while above
normal readings from the central/southern Plains into the
Southeast late this week become more pronounced over the East.
...Guidance Evaluation/Predictability Assessment...
Within what continues to be a consistently agreeable pattern from
a multi-day mean perspective, operational models continue to show
some spread and variability for details and are still in the
process of refining some of the specifics up to 5-6 days out in
time. There are some common themes though. Latest runs are
suggesting that the leading shortwave reaching the West by Friday
may be in the form of a compact closed low that crosses California
and then ejects rapidly northeastward (with mixed signals for
being open or closed at various valid times). Then current
consensus shows the next piece of energy dropping into the mean
trough as a closed low that also tracks through the West and
continues northeastward. Models and ensembles have maintained
reasonable continuity in having the leading shortwave support
Plains into Upper Great Lakes low pressure from late Friday into
Sunday but with a lot of variability for strength in the Great
Lakes. Over the past couple days there had been some significant
waffling in the GFS/ECMWF between stronger and weaker solutions
but latest runs including those from the 00Z cycle are in the
middle to deeper half of the envelope. Guidance still signals
potential for some weakening beyond the Great Lakes as the energy
aloft may shear out to some degree. Latest GFS/ECMWF runs and
their means indicate that the second ejecting western impulse may
lead to another wave that reaches the Great Lakes or Ohio Valley
on a track farther southeast than the first one and only about a
day behind. Such a wave is less defined in the 00Z CMC. Details
of energy behind the second feature become increasingly uncertain,
as seen in differences among the operational models as well as
broadening spread among ensemble members.
The updated forecast started with primary emphasis on the 18Z
GFS/12Z ECMWF with lesser input from the 12Z CMC/UKMET for about
the first half of the period, to reflect an intermediate solution
among the general clustering that existed for the two primary
upper systems and corresponding surface reflection. The greater
uncertainty with details of trailing flow led to trending the
blend toward half models/half means by day 7 Tuesday. This
approach yielded generally modest refinements to continuity.
...Weather Highlights/Threats...
The sequence of two upper systems moving into and through the West
from late this week through the weekend should spread rain and
higher elevation snow across the region. Most activity should be
light to moderate but some locally heavier totals will be
possible, primarily from the Sierra Nevada into the central
Rockies. With much lower confidence, another system that may drop
southeastward into the Northwest early next week may produce some
light to moderate precipitation.
Meanwhile weather will become more active across many areas to the
east of the Rockies from the end of this week into early next
week. The first western feature should generate surface low
pressure that tracks from the central Plains through Upper Great
Lakes during the weekend. The best potential for wintry
precipitation types still extends from the northern half of the
High Plains into the Upper Great Lakes and eventually New England
(where a changeover to rain may occur). Highest probability of
significant snowfall remains over the Upper Midwest, just to the
northwest of the surface low track. Latest guidance suggests the
storm could be strong enough to produce some brisk winds but model
behavior thus far offers potential for additional changes in the
forecast. Rainfall of varying intensity will be possible over the
rest of the central/east-central U.S. ahead of the trailing cold
front. Then there is a continued signal for heavier rainfall
potential generally within an area from the southeastern Plains
into the Ohio/Tennessee Valleys by Saturday night/Sunday into
early next week. This threat corresponds to slower progression of
the trailing front as it becomes more aligned with flow aloft,
interaction with low level Gulf moisture, and the possibility of
another wave that would provide added rainfall focus. The
northwestern fringe of this moisture shield should contain some
wintry weather, likely along an axis somewhat southeast of the
first episode. Specifics will depend on lower-confidence wave
details.
Colder air overspreading the western and central U.S. late this
week into the weekend and persisting through at least early next
week should yield a broad area of temperatures that are 5-15F
below normal. Some pockets of colder anomalies are possible over
the northern/central High Plains. Leading warm sector air,
initially focused over the central Plains and then becoming more
pronounced over the East, will contain readings that are 10-25F
above normal with localized higher anomalies possible for morning
lows. Numerous locations over the Southeast may challenge daily
record highs from the weekend into early next week, while record
warm lows may extend farther northward.
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