Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
248 AM EDT Mon Apr 18 2022
Valid 12Z Thu Apr 21 2022 - 12Z Mon Apr 25 2022
***Additional snow and cold weather likely for portions of the
Northern Plains this weekend, and heavy snow in the Sierra on
Thursday***
...Weather Pattern Overview...
A quasi-zonal flow pattern aloft will initially be in place across
much of the central and southern U.S. on Thursday, with a northern
stream shortwave and surface low crossing north of the Great
Lakes. The pattern becomes more amplified by Friday and into the
weekend as a large synoptic scale trough from the Pacific moves
inland across the Intermountain West, and this will spur surface
cyclogenesis across the Plains by Friday night with showers and
storms developing ahead of the trailing front. Meanwhile, a
downstream ridge axis builds across the eastern U.S. and results
in a considerable warming trend for the weekend.
...Model Guidance Evaluation...
The 00Z model guidance suite appears to have above average
agreement on the main synoptic scale features through Thursday
night, with just some minor differences in cold front timing
across the Great Lakes and Northeast. Similar to yesterday, the
the GFS remains more progressive with the axis of the main trough
axis across the central/northern Plains, and definitely stronger
by 12Z Saturday compared to the model consensus. Meanwhile, the
00Z CMC/ECMWF are in closer agreement and depict a closed low
evolving over the Dakotas by early Sunday, and this also has
support from the 00Z UKMET. The GFS/GEFS is also farther east
with the downstream upper ridge axis over the Eastern U.S., which
would have implications for the temperature forecasts. By early
next week, the models are in good agreement on the depiction of
another storm system over the northeast Pacific Ocean, but
considerable model spread is apparent across the Rockies and
western High Plains in the wake of the departing surface low over
the north-central U.S. A nearly multi-deterministic model blend
was incorporated as a starting point for Thursday, and then more
of the ECMWF/ECENS was used going forward into the weekend along
with some of the CMC and GEFS mean.
...Sensible Weather/Threats...
In the precipitation department, moderate to heavy rain along with
heavy snow in the Sierra will likely be ongoing on Thursday as the
deep upper trough moves inland. This spring event will deliver
some highly beneficial precipitation to drought-stricken areas of
California, with the potential for 1-2+ inches of rain in some
areas of central and northern California, and 1-3 feet of snow for
the higher elevations of the Sierra.
Another round of organized showers and storms are expected to
develop across the central U.S. and extending northward to the
Great Lakes for the end of the week as Gulf moisture is advected
northward ahead of the organizing storm system over the central
Plains. Additional moderate to heavy snow is also expected for
portions of the northern Rockies for Friday and into the weekend,
with an increasing threat for accumulating snow across the Dakotas
and eastern Montana/Wyoming next weekend, potentially affecting
the same areas that were hammered by the recent blizzard.
In terms of temperatures, a major warming trend is forecast for
much of the eastern half of the nation going into the weekend,
along with increasing humidity levels, in response to deep
southerly flow ahead of the central U.S. storm system. One of the
caveats in the temperature forecast will be the presence of a back
door cold front near the Mid-Atlantic and Northeast U.S. this
weekend, with potentially a big contrast over a relatively short
distance, so future changes in the forecast are likely. It will
likely remain uncomfortably cold from Montana to North Dakota and
northern Minnesota with highs running 15-25 degrees below normal.
Hamrick
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, experimental excessive rainfall
outlook, 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/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml