The Weather Prediction Center

College Park, MD


Extended Forecast Discussion




Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
353 PM EDT Sat May 28 2022

Valid 12Z Tue May 31 2022 - 12Z Sat Jun 04 2022

...Multiple rounds of heavy rainfall/convection focus across
south-central Plains near a stationary front next week...

...Overview...

The medium range period will likely begin with an amplified trough
and a low pressure system exiting the northern Plains into
south-central Canada next Tuesday.  The associated trailing cold
front will gradually push east and southeast across the northern
tier states and further into the Plains against a warm ridge over
the eastern U.S. forecast to be gradually eroded by the front
through the end of next week.  Mountain snows initially over the
northern Rockies and gusty winds/convection over the northern
Plains will give way to rounds of thunderstorms over
central/southern Plains where the front is forecast to become
nearly stationary.  Meanwhile, thunderstorms should progress
through the mid-Mississippi and Ohio Valleys, the Great Lakes, and
then into the Northeast as the week progresses.  Farther south,
tropical moisture can be expected to increase across southern
Florida through the medium-range period as a subtropical jet is
forecast to interact with moisture coming up from tropical cyclone
Agatha currently located in the eastern Pacific.


...Model Guidance Evaluation/Preferences...

The abrupt model trend in the past couple days toward a more
amplified upper trough over the northern Plains for early next
week has stabilized, although the most recent model runs still
tend toward a more closed off system, with the associated lead
front pushing faster toward the east across the upper Midwest. 
The GFS and GEFS show their typically faster solutions with
subsequent eastward progression of the front across the Northeast
by next Thursday.  By late next week, deterministic model
solutions begin to diverge regarding the timing and amplitude of a
frontal wave near New England coast.  Meanwhile, models indicate
reasonably agreeable timing of the arrival of the next wave of
Pacific moisture into the Northwest later next week despite quite
a bit of model spread with the latitude of the associated offshore
upper low.  Over Florida, models are now more consistent with
bringing tropical moisture northeastward from the eastern Pacific
where tropical cyclone Agatha is currently located.  The GFS again
favors faster solutions with this tropical moisture feed whereas
the ECMWF and CMC indicate a slower and more consolidated cyclonic
gyre moving across Central America.

Thus the WPC medium range forecast was based on a multi-model and
ensemble blend of 40% from the 06Z GFS/GEFS, 40% from the 00Z
ECMWF/EC mean, and 20% from the 00Z CMC/CMC mean, transitioning to
mostly the ensemble means by Day 7.


...Sensible Weather/Threat Highlights...

The surface low pressure system lifting into central Canada
beginning Tuesday will send a cold front across the north-central
U.S. and across the northeastern quadrant through the latter part
of the workweek. Rain is possible first across North Dakota and
the Upper Midwest to Great Lakes along this front Tuesday and then
shifting eastward across the Ohio Valley and into the
Northeast/Mid-Atlantic by Thursday, after some initial showers in
parts of the Northeast Tuesday-Wednesday near a backdoor front.
However, the back end of the main front is forecast to move more
slowly through central and southern parts of the Plains and
Mississippi Valley, and will provide a focus for rain and
thunderstorms for multiple days around Tuesday-Thursday. Flash
flooding is possible especially where storms repeat over the same
area, which at this point appears most likely to occur around
Kansas, Oklahoma, and Missouri, but with uncertainty in the
details beyond that.

Elsewhere, there is increasing forecast agreement for tropical
cyclone Agatha over the eastern Pacific to turn northeastward and
move across Central America over the next few days.  Scattered
showers and thunderstorms are expected to become more frequent and
widespread across southern Florida later next week although the
specifics are not clear at this time.  Factors that influence the
timing and amounts of rainfall will include (a) the interaction of
a subtropical jet with tropical moisture coming from Agatha, and
the cyclone's subsequent track and intensity after crossing
Central America, (b) the proximity of an upper low forecast to
gradually gain tropical characteristics near and northeast of the
Bahamas midweek, and (c) possible interaction with a tropical wave
moving into the western Caribbean Sea.

The eastern U.S./Mississippi Valley upper ridge will promote above
average temperatures by 10-20F over the Midwest/Ohio Valley and
parts of the Northeast/Mid-Atlantic Tuesday-Wednesday, with some
daily record high maximum and minimum temperatures possible. The
backdoor front reaching New England and possibly as far south as
the northern Mid-Atlantic would bring a cooler trend to these
areas though. Meanwhile upper troughing will bring very cool
temperatures to areas from the Intermountain West through
northern/central Plains through midweek with highs forecast to be
10-20F or below normal. The flattening pattern aloft will push the
initial Plains cold front eastward while leading to a moderating
trend for below normal temperatures over the central U.S., with
mostly single-digit negative anomalies by Thursday-Friday, though
around 10F below normal in rain-cooled Kansas and Oklahoma. The
East should see shrinking coverage of warm temperatures on
Thursday and especially Friday-Saturday. The West Coast and into
the Great Basin could flip back to warmer than normal temperatures
by around 5-15F Wednesday and beyond, followed by a modest cooling
trend on Friday-Saturday along the immediate West Coast with the
arrival of a Pacific front.


Kong/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

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Last Updated: 353 PM EDT SAT MAY 28 2022