Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
222 PM EST Wed Mar 02 2022
Valid 12Z Sat Mar 05 2022 - 12Z Wed Mar 09 2022
...Heavy snow potential over the Northern Plains through Upper
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...
Guidance maintains the forecast of a positively tilted mean trough
from Canada into the western U.S., between a strong ridge over the
eastern Pacific and another ridge that meanders over or near the
southeastern Gulf of Mexico. This configuration will support an
active weather pattern, with a couple episodes of precipitation
over parts of the West and likely one or more areas of significant
rain and snow over some areas of the central and eastern U.S. The
system having highest confidence will track northeastward from the
central Rockies/Plains into the Upper Great Lakes this weekend
with a corresponding band of snow from the north-central High
Plains through the Upper Great Lakes and possibly northern New
England. A trailing upper low reaching the West should ultimately
produce another surface wave, along the first system's cold front,
that takes a somewhat farther southeast track but whose details
are otherwise less certain. This evolution may support an area of
heavy rainfall over parts of the east-central U.S. late weekend
into early next week and possibly some wintry weather on the cold
side of the second wave. Below normal temperatures initially over
the West and northern Plains will expand into the rest of the
central U.S. while frontal progression will gradually trim the
western extent of much above normal temperature anomalies over the
central/eastern states.
...Guidance Evaluation/Predictability Assessment...
After some significant variability and spread in recent days,
guidance over the past day appears to be stabilizing within the
stronger half of the prior envelope for strength as the initial
surface low and shortwave reach the Upper Great Lakes early Sunday
while maintaining decent continuity for track, with just a bit of
east/west spread. Consensus continues to show better definition of
the initial low as it continues northeastward into the Canadian
Maritimes by Sunday morning, along with a slight shift of the
shortwave and cold front southward overall compared to the
previous cycle. The pattern remains complex behind the leading
wave, as a likely closed upper low in the West over the weekend
ejects east early in the workweek, but is muddled by shortwave
energy dropping into the West immediately behind it and also
separate upper troughing that drops into the northern Plains and
vicinity. While a cold front is likely ahead of the mean trough,
guidance continues to waffle with placement of waves of low
pressure along it. The 00Z ECMWF and 06Z GEFS means showed a
position for the low near the Indiana/Ohio border early Monday,
with more variability in position among deterministic models, but
the newer 12Z models have started to cluster better approximately
in that location. Then upstream, there are ample differences in
the details of the pattern by Tuesday-Wednesday given multiple
interacting low predictability shortwaves. The ECMWF and CMC have
been persistent in holding troughing back across the Southwest in
a very positively tilted form, while GFS runs have showed more
progressive troughing. The 00Z EC/CMC pattern is almost outside
the envelope of ensemble members with this Southwest trough. Thus
somewhat preferred the GFS solutions along with the "middle
ground" EC mean. Newer 12Z guidance shows a faster trough in the
EC/CMC and slower in the GFS, so perhaps a consensus is being
reached, at least temporarily.
Early in the period a blend of the 00Z/06Z operational GFS, ECMWF,
and CMC models provided a reasonable starting point for the
forecast. The 00Z UKMET was an outlier with portions of the
pattern, with a slightly eastern track of the main closed upper
low in the West compared to consensus, but more so with much
stronger upstream energy coming into western Canada and
suppressing the eastern Pacific ridge by Monday. The ensemble
means did have a hint of this, and the 00Z GFS was most like them,
but not to the extreme of the UKMET. The UKMET seemed reasonable
across the East though. Then as the period progressed, introduced
and increased weighting of the ensemble means, particularly the EC
mean that showed a deeper trough in the Southwest but not to the
extreme of the operational EC and CMC.
...Weather Highlights/Threats...
Across the West, the leading system emerging into the Plains may
produce some central Rockies snow early in the weekend while the
system immediately behind it spreads rain and higher elevation
snow primarily from the Sierra Nevada into the Wasatch and central
Rockies. Expect generally light to moderate totals but with some
locally heavier totals possible. There is continued potential for
another system to spread mostly light to moderate precipitation
into the Northwest/northern Rockies during the first half of next
week but with less than ideal confidence in the details.
To the east of the Rockies, the leading system forecast to track
from the central Plains through Upper Great Lakes during the
weekend should spread wintry precipitation from the north-central
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. The storm may be strong
enough to produce some brisk winds, with specifics to be resolved
in coming days. 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 and the Lower Mississippi
Valley on Sunday per the latest Storm Prediction Center extended
outlook. Guidance is still showing potential for heavier rainfall
within an area from the southeastern Plains into the
Ohio/Tennessee Valleys by Saturday night/Sunday into early next
week, and there is a Slight Risk of excessive rainfall in place in
WPC's newly experimental Day 5 outlook. 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 one or more waves 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 which will take additional time to
resolve. One change with this forecast cycle was model guidance
taking the bulk of the rainfall eastward rather than southward as
the cold front progresses, so trended down with QPF over the Gulf
Coast states, but this is still subject to change.
Colder air initially over the western U.S. and northern Plains and
spreading over the rest of the central U.S. into early next week
should yield a broad area of temperatures that are 5-15F below
normal. Best potential for locally colder anomalies, especially
for highs, will be over the northern/central High Plains. Leading
warm sector air, initially focused over the central-southern
Plains and southern two-thirds of the East on Saturday, will
become more pronounced over the East by Sunday-Monday when plus
10-25F above normal anomalies for highs and localized higher
anomalies for morning lows may challenge daily records for
highs/warm lows. Highest concentration of record highs may be over
the Southeast with a few record highs elsewhere, such as the
Mid-Atlantic. Coverage of record warm lows may be broader. After
Monday, frontal progression will increasingly confine the warmth
to the Southeast, with record warmth remaining possible in Florida.
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