Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
329 AM EDT Wed Sep 18 2024

Valid 12Z Wed Sep 18 2024 - 12Z Fri Sep 20 2024

...Very heavy rainfall and flash flooding possible in Montana today...

...Severe thunderstorms possible in the northern and central Plains and
Upper Midwest today and Thursday...

A strong occluded low will bring hazardous weather to Montana today as it
lingers over the state. Strong upslope flow along the northern Rockies 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. 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 and 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 Northwest this
morning, then to the Great Basin and California later today 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 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 temperatures with southerly flow ahead
of the Plains system. Highs over the next few days will only be in the 60s
and 70s for much of the West, while highs in the Plains and Midwest reach
the 80s and 90s. A few near-record high temperatures will be possible in
the southern Plains where highs will approach 100 degrees. Above average
temperatures will also be observed in the Northeast under an upper level
ridge, and near to slightly below normal temperatures will be observed in
the Mid-Atlantic and Southeast.


Dolan


Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php