Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 AM EST Wed Mar 02 2022
Valid 12Z Sat Mar 05 2022 - 12Z Wed Mar 09 2022
...Heavy snow potential over the Northern Plains through 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 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 snow 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...
Early in the period a blend of the 12Z/18Z operational models
provided a reasonable starting point for the forecast. 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 it reaches the Upper Great
Lakes early Sunday while maintaining decent continuity for track.
The 00Z CMC trended somewhat weaker than its 12Z run though.
Latest consensus seems to be holding onto better definition as it
continues northeastward. The trailing wave (or even two waves),
initially supported by the next upper low tracking out of the
West, still shows up in most guidance but it remains a complicated
forecast. Not only does flow immediately upstream have some
possible influence on the feature, but separate upper troughing
that drops into the northern Plains and vicinity could eventually
interact with it. Thus latest runs vary significantly for the
character and timing of the surface reflection (new 00Z ECMWF
trending notably slower for example), including differences in
strength and whether there is one consolidated wave or possibly
two waves. By early Monday the model blend and modest
incorporation of the 18Z GEFS/12Z ECMWF means accounted for the
uncertainty with this feature at that time. If anything,
north-south spread has widened in the new 00Z guidance.
Returning upstream later in the period, there is some relative
agreement that mid-period energy over the West should gradually
continue eastward (but with less effect on sensible weather) but a
lot more spread with a shortwave expected to round the Pacific
ridge and possibly drop into the Northwest. Ensemble means have
tended to agree upon a somewhat faster progression than the latest
ECMWF and especially CMC runs while the GFS and UKMET have been
closer to the means in principle. For continuity the forecast
ultimately trended a little more toward the ensemble means by next
Wednesday with a little more weight to the GFS relative to the
ECMWF for the lingering operational weight.
...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 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. 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.
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. Coverage of
record warm lows may be broader. After Monday, frontal progression
will increasingly confine the warmth to the Southeast.
Rausch/Tate
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