…Heavy rainfall and flash flooding possible in Montana through tonight…
…Severe thunderstorms possible in the northern/central Plains and Upper
Midwest through Thursday…
…Late-summer heat forecast throughout parts of the southern Plains…
A strong occluded low will bring hazardous weather to Montana through
tonight as it lingers over the state. Strong upslope flow along the
northern Rockies and central Montana ranges on the backside of the low
will result in showers and thunderstorms with very heavy rainfall totals.
A Slight Risk of Excessive Rainfall (level 2/4) is in effect for portions
of Montana where scattered flash flooding will be possible. Wintry
precipitation will also be possible in the high elevations of the northern
Rockies. In addition to precipitation hazards, a strong pressure gradient
in the vicinity of the central low will result in strong, gusty winds
across the region, including into parts of the northern Plains. High Wind
Watches and Warnings are in effect for portions of Montana and Wyoming
where winds are forecast to be 30-40 mph with gusts up 60 mph. The low
will gradually lift north into southern Canada Thursday and Friday, and
rain and winds will begin to relax.
The strong low pressure system will also push a cold front across the
Plains and Upper Midwest through Friday. A line of showers and
thunderstorms will move east ahead of the cold front, and the environment
will support the development of scattered severe thunderstorms. The Storm
Prediction Center has highlighted portions of the Plains and Upper Midwest
with a Slight Risk of Severe Thunderstorms (level 2/5) today and again on
Thursday. Potential severe storm hazards will include damaging wind gusts,
large hail, and a few tornadoes. Shower and thunderstorm coverage will
expand into the Great Lakes, Mid-Mississippi and Ohio Valleys on Friday as
the cold front continues to trek east.
Elsewhere, two coastal lows will sandwich the continental United States,
one moving south along the West Coast and one moving north along the East
Coast. The West Coast low will bring precipitation to the Great Basin and
California tonight into Thursday. Precipitation will fall mainly in the
form of showers and thunderstorms, but some wintry precipitation will be
possible in the Sierra Nevada. The low will weaken on Friday, and
precipitation will taper off. The East Coast low will gradually deepen
offshore of the Mid-Atlantic over the next few days with a slow-moving
frontal boundary extending southwest from the low. Showers and storms
capable of localized intense rainfall will be possible for the
Mid-Atlantic, coastal Northeast, Southeast, and Florida. This system will
also produce gusty winds over the coastal waters, which has prompted Small
Craft and Coastal Flood Advisories along the Mid-Atlantic Coast.
Temperature-wise, the West will experience well below average temperatures
in the wake of the strong frontal system in the Plains, while the Central
U.S. experiences well above average summer-like temperatures with
southerly flow ahead of the Plains system. A few near-record high
temperatures will be possible in the southern Plains where highs will
approach the upper 90s and near 100 degrees, including the Oklahoma City
metro region. Above average temperatures will also be observed in the
Interior Northeast under an upper level ridge, and near to slightly below
normal temperatures will be observed in the Mid-Atlantic and Southeast.
Dolan/Snell
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php
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