Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Mon May 16 2022
Valid 12Z Thu May 19 2022 - 12Z Mon May 23 2022
...Persistent record-breaking heat is likely in the south-central
U.S. through this week with anomalous heat expanding into the East
by the weekend...
...Overview...
A digging trough over the West and rising heights across the East
late this week will result in a more amplified pattern across the
lower 48 yielding cooler temperatures and lowering snow levels in
the West and a continued hot regime for the South and East. A
closed low across the northern tier Thursday-Friday and a strong
cold front shifting East will chances for heavy rainfall and
severe weather for some from the upper Mississippi Valley/Great
Lakes into the East. The upper trough will dig into the central
and eastern U.S. next weekend as height rise again out West.
Tropical moisture will also increase rain/thunderstorm chances
across Florida late this week and into the weekend.
...Guidance Evaluation/Preferences...
Model guidance has trended stronger with a closed low across the
northern High Plains into the Upper Mississippi Valley Thursday
and Friday, but show relatively good agreement on this feature,
with mainly just some minor timing differences as the low lifts
into central Canada and the amplified trough slides into the Ohio
Valley/Northeast on Saturday. For the first half of the period, a
general model compromise worked well. After this, model guidance
begins to show much more uncertainty surrounding a couple of
shortwaves through the West Sunday/Monday. The ECMWF is stronger
with an initial shortwave dropping down behind the eastern trough
tending to amplify this feature more than the other guidance
resulting in a stronger ridge over the West. Meanwhile, the GFS
and the CMC are weaker with this first shortwave which allows for
a weakness to round the top of a Pacific upper high and slide into
the West. The WPC blend trended towards the ensemble means which
seemed to side more with the GFS and CMC vs the ECMWF, but still
incorporated some minor amounts of the ECMWF and GFS for added
flow definition.
...Weather/Threat Highlights...
Initial ridging across the southern Plains and rising heights
farther east over the Deep South will continue to promote a broad
area of heat across much of the southern U.S. during the period.
The greatest and most lasting anomalies through the period should
be over Texas (persisting from the short range time frame) where
some locations could see highs up to 15-25F above normal, with
numerous daily record highs likely. The heat across Texas should
finally begin to moderate by next weekend as troughing presses
through the West. However, warm to hot temperatures are also
forecast for the southeastern quadrant of the U.S. with potential
for daily record highs, and warmer than average temperatures by
10-20F should expand in coverage across the Ohio Valley to Eastern
Seaboard by later in the week.
A warm front lifting through the Mid-Mississippi Valley and Ohio
Valley will provide a focus for multiple areas of showers and
storms/convective complexes during the middle to latter part of
the week. The ingredients are in place for heavy rainfall, though
the specifics of coverage and amounts are uncertain, but at least
a localized flood threat is likely especially if heavy rain falls
in areas that are sensitive to additional rainfall. Then organized
rainfall, heavy at times, is likely along a frontal boundary
through the north-central U.S. around Thursday with potential for
at least localized flood and flash flood threats given wet
antecedent conditions across that region. Storms that could be
severe are forecast to shift from the Upper Midwest into parts of
the Ohio and Mississippi Valleys along this front Thursday into
Friday. Additionally, tropical moisture increasing across the
Florida peninsula late this week could lead to a more rainy
pattern for the Sunshine State.
After a couple of initial fronts crossing the Northwest, the main
well-defined front ahead of the deepening trough will bring
unseasonably cool temperatures to the Northwest and expanding into
the northern Rockies and High Plains by late week. This will also
provide support for a notable round of precipitation, with
lowering snow levels in the Cascades to Northern Rockies as the
week progresses, with some chance of snow even into northern parts
of the High Plains, though with very low confidence at this point.
Santorelli/Tate
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