…Heavy rainfall and snowmelt bring flooding concerns to portions of the
northern High Plains of Montana today…
…Outbreak of severe weather, including strong tornadoes, expected for
portions of the Midwest/Plains Monday…
…Threat of potentially significant flash flooding returns to portions of
the southern Plains Tuesday…
…Warm, well above average conditions to start the week for much of the
central/eastern U.S….
Our ongoing Spring weather pattern across the U.S. will bring increasingly
active weather into the mid-section of the country as we head into the new
week. A deep, upper-level trough over the western U.S. continues to bring
unsettled weather and cool conditions to portions of the West. Ongoing
showers and some thunderstorms as well as higher elevation snow across the
Sierra Nevada and central Great Basin should begin to taper off through
tonight and into the early morning hours Monday. Some snow may mix in with
the showers at lower elevations, though accumulations are not expected.
Further east, moist, southerly return flow across the Plains as well as
increasing upper-level support as the upper-trough begins to overspread
the region will bring the risk of some isolated afternoon thunderstorms
today along the High Plains. Strong CAPE supported by the boundary layer
moisture as well as sufficient upper- and low-level shear given strong
wind fields with the approaching trough will bring the threat of some
severe weather. A Slight Risk (level 2/5) has been issued by the Storm
Prediction Center for the chance of very large hail, damaging winds, and a
few tornadoes. More widespread storms along portions of the northern High
Plains of Montana have prompted a Slight Risk of Excessive Rainfall (level
2/4) as locally heavy rainfall rates supported by the very moist, upslope
flow in combination with snowmelt over terrain sensitive areas, including
burn scars, may lead to some scattered instances of flash flooding.
Additional, more isolated instances of flash flooding will be possible as
storms over the northern High Plains grow upscale into a complex and move
eastward through the Dakotas during the overnight hours. The potent
upslope flow will bring heavy snow to higher mountain elevations of
southern Montana and northern Wyoming, with winter weather-related
advisories in place for some significant accumulations as much as 1-3
feet.
Then, on Monday, as the upper-level trough shifts further eastward across
the Plains and over portions of the Midwest, another day of moist return
flow as well as the very strong wind fields will support the development
of widespread, intense thunderstorms and a potentially significant severe
weather outbreak. The Storm Prediction Center has issued a Moderate Risk
(level 4/5) over portions of the Upper Mississippi Valley as supercells
possible ahead of an approaching cold front will be capable of producing
strong tornadoes, very large hail, and damaging winds. An Enhanced Risk
(level 3/5) extends southwestward along the cold front through the Middle
Missouri Valley with a Slight Risk southwestward through the southern
Plains as additional storms along the cold front will bring an
increasingly more isolated but still notable threat for very large hail,
damaging winds, and a few tornadoes. Locally heavy rainfall may also lead
to some isolated instances of flash flooding as well. On Tuesday, the cold
front will begin to slow and stall with southwestward extend over the
southern Plains as leading upper-level energy quickly lifts northeastward.
Repetitive rounds of storms in vicinity of the stalling boundary over an
already sensitive region given recent rainfall has resulted in a Moderate
Risk of Excessive Rainfall (level 3/4) for portions of southwest Oklahoma
and northwest Texas with scattered to numerous instances of flash flooding
possible. A broader Slight Risk extends northeastward towards the Middle
Mississippi Valley and southwestward into the Texas Big Country for
additional scattered instances of flash flooding. More generally,
scattered to widespread storms are expected along the cold front from the
interior Northeast southwestward through the Ohio/Middle Mississippi
Valley and southern Plains. The Storm Prediction Center has included a
Slight Risk of severe weather along the length of the front as some storms
will be capable of large hail and damaging winds.
Elsewhere, very dry conditions as well strong, gusty winds have prompted
an Extremely Critical Risk of fire weather (level 3/3) from the Storm
Prediction Center for portions of New Mexico through the rest of today,
with Elevated conditions (level 1/3) remaining in place Monday. A
quasi-stationary frontal boundary across portions of the Southeast will
bring some shower and thunderstorm chances on Monday. A Pacific system
will bring increasing precipitation chances to the Pacific Northwest
Monday evening and then inland through the northern Great Basin and
Rockies into Tuesday. An upper-level ridge building over much of the
central/eastern U.S. will bring well above average conditions to start the
week. Forecast highs in the 70s and 80s will be common, including for more
northern locations like the Midwest and Northeast. After a cool, well
below average weekend, temperatures will begin to return back closer to
average over the West Monday and especially into Tuesday, with highs
generally ranging in the 60s and 70s, with 80s into the Desert Southwest.
Putnam
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php
