Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
222 AM EDT Tue Apr 19 2022
Valid 12Z Fri Apr 22 2022 - 12Z Tue Apr 26 2022
***Threat of winter storm increasing for portions of the Northern
Plains this weekend***
...Weather Pattern Overview...
The upper level pattern over the continental U.S. becomes more
amplified by the end of the week 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 High Plains by Friday night. This low will then track across
the Upper Midwest through early Sunday, with a trailing front
across the Mississippi River Valley that will fuel showers and
storms. Meanwhile, a downstream ridge axis builds across the
eastern U.S. and results in a considerable warming trend for the
weekend. Another Pacific trough approaches the northwestern U.S.
by the beginning of next week.
...Model Guidance Evaluation...
The 00Z model guidance suite appears to have above average
agreement on the main synoptic scale features through early
Saturday, with just some minor differences in the timing of the
upper trough evolution over the western states. The GFS is not as
progressive as earlier runs with the axis of the main trough axis
across the central/northern Plains, although the CMC is slower in
lifting the trough/closed low out of the region. By early next
week, the models are in good agreement on the depiction of another
storm system over the northeast Pacific Ocean, but model
differences still exist with the degree of upper level ridging
ahead of that feature across the Intermountain West. A nearly
multi-deterministic model blend was incorporated as a starting
point for Friday and Saturday, and then more of the ECMWF/ECENS
was used going forward into early next week along with some of the
GFS and GEFS mean.
...Sensible Weather/Threats...
The threat of a noteworthy winter storm is increasing with time
for western North Dakota and portions of eastern Montana for the
upcoming weekend on the backside of the intensifying surface low,
where a well-defined deformation zone will likely exist. This
will likely be coupled with strong northerly winds owing to the
tight pressure gradient that will be in place, and this could
result in blizzard conditions for some areas if these model trends
continue. Moderate to heavy snow is also likely for the northern
Rockies through early Saturday, and this will also include the
higher terrain of northern Utah and central Colorado.
Heavy showers and thunderstorms could also make weather headlines
on Sunday and going into early Monday across the central U.S. as a
deep surge of Gulf moisture advects northward and interacts with a
slow moving surface cold front with multiple shortwave
perturbations moving overhead. This will likely be in the form of
multiple mesoscale convective complexes with repeating rounds of
convection, and some strong to severe storms are also possible.
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/cold air damming for the Mid-Atlantic and
Northeast U.S. this weekend, with potentially a big contrast over
a relatively short distance near the front. It will likely remain
uncomfortably cold from Montana to North Dakota and northern
Minnesota with near-freezing highs running 15 to 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