Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
236 PM EDT Sun Apr 03 2022
Valid 12Z Wed Apr 06 2022 - 12Z Sun Apr 10 2022
...Overview...
The lower 48 will see an amplified upper pattern during the medium
range period (Wed-Sun). During the mid to late week time frame the
dominant features will be a deep east-central U.S. trough anchored
by an Upper Midwest into Great Lakes low, and a western U.S.
ridge. The upper low/trough and associated surface evolution will
produce a broad area of precipitation across the northern Plains
and eastern half of the country (with some pockets of locally
heavy totals possible) while the western ridge will support much
above normal temperatures, including potential for some record
highs/warm lows over California and vicinity. By the weekend
expect a Pacific trough to move into the West, leading to a
cooling trend and some precipitation, while progression of the
eastern trough to East Coast should favor drier weather over the
East.
...Guidance Evaluation/Predictability Assessment...
In the East, the 00z CMC and UKMET continued to be farther west
with it's track than consensus with the initial wave in the
Mid-Atlantic on Wednesday. Upstream, concerning the Midwest closed
low, the 00z UKMET is quickest to open up the low, leading to a
faster progression of the system as a whole. Later 12z runs of the
CMC and UKMET seem to show better consistency with the GFS and
ECMWF for both features. Later in the period, the trough in the
East should linger/become elongated as ridging amplifies into the
Central U.S.. There are some timing concerns for the front late
period, but mostly not until it's well off the coast.
Out West, plenty of uncertainty continues to surround the
evolution of troughing into the region by next weekend. Models
show an initial wave moving through on Friday, with a bigger
closed low dropping down from the Gulf of Alaska by Sunday.
Biggest outlier was the 00z CMC which was quite a bit
deeper/amplified with the first system resulting in another
building ridge over the West Coast next weekend and less
progressive Gulf of Alaska low. The GFS and ECMWF were a little
bit more in line, racing the initial shortwave off into central
Canada as the next low reached the coast by Sunday. This general
evolution was also better supported in the ensembles. The 12z run
however of the CMC has abandoned this idea and seems to have come
much more into line with the GFS/ECMWF and ensemble means. But
detail differences among model runs and ensemble members continue
to suggest lower predictability for this overall trough versus the
ridge/trough configuration farther east.
The WPC blend for today utilized a non-UKMET consensus for the
first half of the period in the East. Out West, the CMC was left
out in favor of increasing weighting towards the ensemble means to
help mitigate the Western U.S. uncertainties. This provided very
good continuity with the previous WPC forecast as well.
...Weather Highlights/Threats...
The deep-layer low tracking over the Upper Midwest into Great
Lakes, along with a leading triple point wave that may become the
primary system by the end of the week--plus the trailing cold
front--should support multiple areas of enhanced precipitation
mid-late week. Specifics for heaviest totals are still fairly
uncertain though. One area of focus may be for some combination of
rain and/or snow over or a little west/south of Lake Superior,
just north of the parent low's track. Meanwhile the wave expected
to track from the Mid-Atlantic northeastward may produce some
locally moderate to heavy rainfall. Far interior sections of New
England may see some wintry weather on the leading side of the
moisture. More localized pockets of enhanced rainfall are possible
farther south along the trailing cold front. The Storm Prediction
Center is monitoring potential for severe threats across the
southern tier. Check their latest outlooks for more information.
Expect lingering showery precipitation, possibly including some
snow from the Midwest into the Appalachians, under the cold upper
trough into Saturday. The upper trough pushing into the West by
the weekend should bring mostly light to moderate rain and high
elevation snow into the Northwest starting Friday or Saturday.
The upper ridge building into the West will spread a broad area of
well above normal temperatures across the region mid-late week.
Highest temperatures will likely be on Thursday-Friday when parts
of California and Oregon into the Great Basin could see readings
15-25F above normal. Some daily records for highs/warm lows will
be possible. The upper trough arriving from the Pacific will bring
a rapid cooling trend during the weekend, with much of the West
seeing near to below normal highs by Sunday. Farther east, highs
generally 5-15F or so below normal will progress from the northern
Plains/northern-central Rockies into the East during
Wednesday-Saturday under the deep upper trough. Expect
temperatures to moderate noticeably by next Sunday. Flow ahead of
the upper trough will bring a couple days of above normal readings
(especially for morning lows) to the East around
Wednesday-Thursday.
Santorelli/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, 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