Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 290848
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
248 AM MDT Fri Mar 29 2024

.DISCUSSION...
A broad trough of low pressure will remain across the western US
and Northern Rockies today, while the best dynamics, moisture, and
precipitation focus across California. Nonetheless, another round
of convective showers will develop across the area by the early
afternoon. Activity will generally focus across mountain areas and
along the divide. Snow levels will climb to 4,000-4,500 feet,
with valleys seeing a mix of rain, snow, and/or graupel showers.
The primary impact to travelers will be periodic visibility
reductions, particularly across mountain passes. Mild surface
temperatures will limit any accumulations on roadways at pass
level, reducing impacts and the need for winter highlights.

The broad trough will amplify into far southern California this
weekend. The backside of the trough will provide enough moisture
and lift to keep shower activity going within northwesterly flow.
Activity will focus across mountain ranges in west-central
Montana and north-central Idaho. This system will lack moisture;
therefore, only light precipitation amounts are expected. This is
supported by NBM 48-hr probabilities for 0.10” or more of
precipitation in the 30-50% range across mountain areas.
Probabilities for 0.25” of precipitation decrease to 10-15% in the
mountains.

Model ensemble guidance continues to highlight a strong ridge of
high pressure building across the PacNW and Northern Rockies
Monday into Tuesday. This warm and dry period will send
temperatures into the 60s and 70s by Tuesday afternoon. This ridge
will be short-lived; however, as a broad trough digs
southeastward across the Gulf of Alaska into the western US by
mid-week. The timing of the ridge breakdown remains a forecast
challenge, with 60 percent of model clusters bringing the Pacific
trough and surface cold front into the Northern Rockies by
Wednesday PM. The other 40 percent have a slower frontal passage,
with precipitation and colder temperatures arriving on Thursday.
This uncertainty can be visualized within NBM guidance as the low
end (25th percentile) high temperature forecast for Missoula on
Wednesday is 51F, while the high end (75th percentile) is 70F.
Stay tuned for updates on this period as the forecast comes into
focus! /Lukinbeal

&&

.AVIATION...Convective showers will develop across area after
29/1900Z, with activity generally focusing over the higher
terrain and along the divide. Snow levels will climb above 4,000
feet, with valley areas seeing a mix of rain, snow, and graupel.
Showers will be capable of producing periodic visibility
reductions and terrain obscurations. A 30 percent probability
exists for a shower to cause IFR visibility reductions at KBTM
between 29/2000-2400Z. Generally light surface winds (<10kts) will
develop this afternoon from the west-northwest. /Lukinbeal

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$


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