814
FXUS65 KMSO 242018
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
218 PM MDT Fri May 24 2024

.DISCUSSION...Current radar trends this afternoon have depicted an
increase in showers across northwest Montana. The meso-analysis
portrays up to 100 J/kg of CAPE instability, which could be enough
juice to cause a shower to grow tall enough to produce a lightning
strike. There is a 40 to 50 percent probability for lightning
occurrence with one of the showers through 7 pm, generally across
northwest Montana.

Another area that will need to be watched is over in north-central
Idaho. The lightning occurrence probabilities range from 20 to 40
percent generally from Grangeville and points south and west from
5 to 11 pm PDT. So if you are recreating on the Snake River or
along US-95, have a safe place in mind before you go. These
showers could also produce wind gusts in excess of 30 mph (25%
probability).

The incoming upper trough will be much different than the heavy
snow-producing system from Thursday. Ensemble means suggest that
this will be more of an open wave moving quickly across the region
Saturday into Sunday morning. Total precipitation ranges in the
western Montana valleys go from nothing to several hundredths in
the lower range, and up to 0.10 to 0.20" in the upper range. The
mountains of north-central Idaho range from 0.10 to 0.50" and the
western Montana mountains could range from a few hundredths up to
a couple of tenths. Snow levels could be as low as 5000 feet, but
probabilities for an inch or greater are mainly confined to the
passes along the Idaho/Montana border including Lost Trail Pass.

As the trough exits the region Sunday, a drying trend will start,
but it will end up being a breezy afternoon across the region. The
mean wind speeds will range from 10 to 25 mph across western
Montana.

Temperatures will rebound into the 70s and 80s by Monday and
Tuesday. Ensembles show around a 70 percent probability that the
cold front on Tuesday will be into north-central Idaho by evening
time...55% northwest Montana. There is an 80% probability that the
wind shear will be greater than 35 knots in these areas. And
lastly the mean instability values are around 500 J/kg which could
be enough to trigger a few strong thunderstorms along this cold
frontal boundary. Any thunderstorm could be capable of producing
gusty winds over 40 mph, hail, lightning and heavy rain.

&&

.AVIATION...Instability showers have begun to pop up this
afternoon, especially across northwest Montana. There is a roughly
30 percent chance that these showers could produce a lightning
strike through 25/0300z, mainly from Flathead Lake northward to
the Canadian border. Another area of showers and thunderstorms
will be possible through north central Idaho, including
Grangeville and the Camas Prairie after 25/0000z. Winds will be
relatively light overall across western Montana and north central
Idaho but gusts of 15-25 kts will occur near showers/storms.
Precipitation will become more widespread through central Idaho
into western Montana late tonight into Saturday with relatively
widespread obscurations of the higher terrain anticipated.

&&

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

$$