Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
254 AM EDT Mon Apr 11 2022
Valid 12Z Thu Apr 14 2022 - 12Z Mon Apr 18 2022
...Overview...
A strong springtime low pressure system will be exiting the Upper
Midwest as the period begins Thursday, as its attendant cold front
slides through the East. After Thursday/day 3, the pattern finally
appears to deamplify somewhat as a weaker shortwave/trough moves
into the West around Friday-Saturday. Guidance shows this trough
moving eastward with time eventually into the central Plains where
it could induce another low pressure system across the Midwest
next Monday. This could bring another round of precipitation into
the northern and eastern part of the country early next week,
although there's still plenty of uncertainty with respect to the
details.
...Guidance Evaluation/Predictability Assessment...
The latest models and ensembles finally seem to show some decent
agreement on the large scale evolution of the departing deep upper
low into Eastern Canada Thursday-Friday, which looks to
meander/weaken there as it gets blocked by amplified western
Atlantic ridging. Models show varying degrees of uncertainty
regarding shortwave energy rounding the base of this through the
Southeast, with secondary low pressure developing along the cold
front off the Northeast Coast next Friday. The ECMWF has both been
most consistent and strongest with this, which of course has
implications for how much precipitation lingers across the
Southeast/East Coast into next weekend. A general deterministic
model blend (with slight weighting towards the ECMWF for
continuity reasons) seemed to provide a good starting point for
days 3-4.
Out West, the models continue to show a lot of uncertainty
surrounding the next trough through the region. There's good
agreement on low pressure present near the coast on day 3, but
after that questions begin to arise regarding strength and timing
of the main trough axis through the Northwest. The ECMWF and UKMET
are strongest/most amplified with this trough and also downstream
ridging across the north-central U.S.. By day 6, the latest runs
of the ECMWF and GFS show pretty good agreement on timing of the
wave into the Central U.S., but poor run to run continuity on this
feature which tempers confidence quite a bit. The CMC is entirely
too weak/flat with this system and was not included in the blend
after day 4. The ECMWF continues to be notably stronger with the
wave into the Midwest on Monday/day 7, indicating a deep closed
low and well defined low pressure system at the surface. Prefer a
blend towards the better agreeable (and weaker) ensemble means for
the latter periods to help mitigate the harder to resolve
differences.
...Weather Highlights/Threats...
Some lingering snows are possible across the Upper Midwest at the
start of Thursday, but the heaviest should be rapidly coming to an
end as the deep low departs into Canada. Gusty winds are likely to
continue into Friday though creating blowing and drifting of snow
and possible hazardous travel conditions. Moderate to locally
heavy rainfall should be moving through the East ahead of the
attendant cold front on Thursday into Friday, with the best chance
for heavier totals across parts of the Southeast where the better
moisture and instability will be present. Rainfall across the
Southeast could linger into the weekend as the western edge of the
boundary tries to lift north as a warm front and weaken across the
Southeast. Out West, moderate to heavy rain/mountain snows are
possible across parts of California/Oregon with the next low
pressure system Thursday-Friday. Moisture should spread east into
the Intermountain West and northern Plains next weekend.
Significant uncertainty regarding low pressure into the Midwest
next week, but the latest guidance suggests decent probability for
another round of precipitation to affect the northern and eastern
states early next week.
The core of the below normal temperatures are likely across the
northern High Plains into early next week, with daytime highs
around 20-30 degrees below normal possible. Out West, below normal
temperatures should moderate back towards normal later in the
period as ridging tries to build over the region. Above normal
temperatures along the Eastern Seaboard initially should trend
back towards normal next weekend. Below normal temperatures will
spread south and east next Sunday-Monday into the Midwest with
some readings 10-20F possible.
Santorelli
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