Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 PM 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 much 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. The period begins
Friday with good consensus for three primary shortwaves within the
broader western trough. The past few guidance cycles have
indicated that the leading southeasternmost one centered over
California Friday will likely 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). The second shortwave now has better consensus that it will
take the form of a closed low as it generally follows the track of
the first, moving through the West and then turning northeastward.
The third is most likely to track across southwestern Canada late
this week and shear out early next week, though with its energy
possibly combining with the initial shortwave as it reaches the
Great Lakes. Then the 00Z CMC was alone in showing another small
closed low diving south along the West Coast over the weekend,
which was not favored.
As the initial shortwave tracks into the Midwest/Great Lakes by
early Sunday, the 00Z and newer 12Z guidance seems to have
steadied in showing deeper solutions with this feature and the
associated surface low compared to some previous runs. 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. There is more uncertainty in position and
depth with this surface low, and the strongest model thus far is
the 12Z GFS. 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 overall trends for this forecast update for day 7
were a deeper trough rebuilding across the West, which is now seen
in the 12Z ECMWF and CMC as well, and a faster trend of the cold
front tracking farther offshore into the Atlantic.
The updated forecast started with primary emphasis on the 06Z
GFS/00Z ECMWF with lesser input from the 00Z 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 reasonably
good clustering in the overall pattern but with some greater
uncertainty with details of trailing flow led to some addition of
the ensemble means particularly by day 7, but still with a
majority deterministic model blend. This approach yielded
generally modest refinements to continuity other than the
aforementioned ones.
...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 Wasatch and
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 just to the northwest of the surface
low track, with increasing chances over the northern Plains and
continued chances over the Upper Midwest. 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. Embedded thunderstorms could be severe in the
Mid-Mississippi Valley on Saturday per the latest Storm Prediction
Center extended outlook. 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, particularly in terms of highs.
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.
Tate/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