Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 PM EDT Sun Mar 27 2022
Valid 12Z Wed Mar 30 2022 - 12Z Sun Apr 03 2022
...A rapidly deepening low pressure system presents a mid-late
next week heavy rain/severe weather threat focus across the South
while heavy snow/ice and high wind threat focus across the Upper
Midwest/Great Lakes...
...Guidance Evaluation/Predictability Assessment...
Model guidance this morning continues to indicate the likelihood
of a rapidly deepening cyclone to track from the central Plains
through the Great Lakes Wednesday-Thursday. Model consensus
appears to trend toward a faster progression of the cyclone center
through the Great Lakes in better agreement with earlier GFS runs.
In addition, there has been a gradual eastward shift in the
rainfall maximum across the Deep South with a slightly faster
eastward motion of the southern stream low. This eastward shift
might have ceased in the most recent couple of model cycles. The
faster southern stream low also resulted in a faster progression
of the cold front through the eastern U.S. Thursday-Friday.
Meanwhile, the next upper trough from the Pacific will come into
play by midweek as it reaches the Pacific Northwest. Models have
been showing difficulties in handling and resolving the timing and
evolution of this system as it heads downstream. It appears that
the consensus is for the system to generally glide southeastward
across the western U.S. late this week as the ECMWF and CMC have
adopted a less amplified solution compared with earlier runs.
This would favor frontal wave development by the weekend over the
central Plains as supported by the ECMWF. The timing of the
progression of the upper trough downstream is subject to large
uncertainty however. At present, the consensus supports a frontal
wave to move across the Southeast late this weekend after a
potential resurgence of Gulf moisture late next week across the
central and eastern Gulf Coast states north of a stationary
boundary.
A composite blend of 40% 00Z ECMWF/EC mean, 40% 06Z GFS/GEFS and
20% from the 00Z CMC/CMC mean was used to compose the Days 3-5
forecasts, transitioning to mostly a consensus of the ensemble
means by Day 7. The results compare well with WPC continuity.
The timing of the upper trough/frontal wave across the mid-section
of the country is the most uncertain part of the forecasts.
...Overview and Weather Highlights/Threats...
As a main surface low pressure system over the Plains strengthens
and tracks northeast, increasingly widespread rain with heavy
downpours and a threat for severe weather are forecast across the
South into Wednesday before spreading over the
Southeast/Mid-Atlantic Thursday. A "slight" risk area remains
depicted on the WPC experimental medium range excessive rainfall
outlook (ERO) for Wednesday given favorable system ingredients and
antecedent conditions. Meanwhile, rain and thunderstorms are also
expected farther north from the central Plains through the East
with wavy frontal progression across the region.
On the northern side of the precipitation shield, expect a swath
of heavy wintry mix and accumulating snows from the Upper Midwest
to the Great Lakes into Wednesday-Thursday given continued
excellent model consensus on developing a rather intense cyclone.
In addition, high winds appear likely near and well to the west of
the low track given the impressive rate of cyclogenesis. Some
wintry precipitation is also forecast for northern New England
ahead of and on the back side of this system.
Late week, additional upper trough energies forecast to dig with
some uncertainty southeastward from the Pacific Northwest through
the West could provide another opportunity for an enhanced round
of wintry weather, mainly for the northern to central
Intermountain West/Rockies to the High Plains. Potential system
amplitude and progression into next weekend would favor return
moisture flow into an increasingly wavy/lifting front. This may
support renewed heavy rainfall potential across the
central/eastern Gulf Coast states and Southeast next weekend.
Kong/Schichtel
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
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