Tornado Warning 1, NWS Glasgow, MT

Area Forecast Discussion
National Weather Service Glasgow MT
314 PM MDT Thu Jun 1 2023

.DISCUSSION...

The stage is set for a multi-day heavy rain event (or series of
events) to impact most of northeast Montana tonight through
Saturday morning.

An overall stagnant flow pattern with higher pressure to the east
and lower pressure to our west will both combine to draw in
moisture transport from the Pacific Ocean AND the Gulf of Mexico.
These moisture sources will travel our directions and converge and
wrap up into NE and NC Montana, producing mulitple waves of heavy
rain amid scattered general thunderstorms. Given the lack of shear
in this environment, the main threat obviously with any of these
storms will be heavy rain and flooding. Minor threats would be
lightning and gusty winds.

Following the best model consensus for timing and amount of
rainfall, I felt it was best to update/expand the area of the
flood watch to now include another tier of zones eastward. For
more information, refer to the Hydrology discussion below.

From Saturday night moving forward, the stagnant flow pattern
remains, as we continued to be sandwiched between low pressure
from the west and high pressure from the east. Unusually humid air
will remain over our region for the foreseeable future. Models
show showers and thunderstorms nearly every day, but confidence is
average to below average for details on timing and amounts.

----BMickelson

&&

.AVIATION...

VFR mostly, with isolated MVFR directly in a thunderstorm later
this evening and through the remainder of the TAF cycle tomorrow.

After a day of mostly sunny skies today, more widespread and
intense rain showers with scattered thunderstorms will move into
the area from the south beginning this evening. Heavy rain will
become even more intense through the day on Friday. Expect
amendments and erratic gusty winds near the stronger storms.

Ahead of the storms, winds will be from the southeast at 10 to 15
kts.     ----BMickelson

&&

.HYDROLOGY...

The stagnant weather pattern and moisture laden atmosphere will
lend itself to efficient heavy rainstorms and scattered
thunderstorms, especially this evening through all day Friday.
Models are beginning to fall in line, showing heavy rainfall
accumulations most locations near and west of MT-Highway 13. When
the low pressure circulation strengthens over Wyoming this evening,
storm are expected to ramp up.

Near and west of a line from Scobey through Wolf Point through
McCloud, 2-day rainfall accumulations will be between 1 and 2
inches. Locally higher amounts may be possible. Near and east of
that line, expect less than 1 inch of rainfall.

Anyone planning outdoor activities should closely monitor the
latest forecasts and any possible flood warning that may be
issued. Alternate plans will need to be considered in order to
address public safety concerns.

----BMickelson

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
Flood Watch through late Friday night for Central and Southeast
Phillips...Central and Southern Valley...Daniels...Garfield...
McCone...Northern Phillips...Northern Valley...Petroleum...
Prairie...Southwest Phillips...Western Roosevelt.

&&

weather.gov/glasgow