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321
FXUS65 KMSO 180959
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
359 AM MDT Thu Apr 18 2019

.DISCUSSION...It will be a delightful spring day in the Northern
Rockies today as high temperatures rise into the 60s in western
Montana and low 70s in central Idaho. Missoula has only
experienced a 60 degree day once this spring on April 2,
Kalispell hasn`t seen 60 since October 24 and the last time Butte
saw 60 or greater was October 28 of last year. COOP data wasn`t
available for some of the central Idaho locations, but looking at
the observations from the Idaho County Airport in Grangeville, it
hasn`t been above 60 degrees there since Oct. 26.

The timing of the next weather system has slowed down a little
bit. This means that the chance for showers has lowered tonight
into Friday. Also another artifact of the slower front progression
for this forecast update has been to raise high temperatures
especially across west- central/southwest Montana. If this slower
trend keeps up, several locations may clip 70 degrees for the
first time this year! The chance for thunderstorms has also been
added for Missoula and a few locations over northwest Montana. The
best chance for any stronger thunderstorms still exists from Idaho
County and points east Friday afternoon and evening. These storms
will be moving pretty fast to the northeast at about 35 mph and
will produce heavy rain and lightning, small hail and gusty
winds. There is also the chance for isolated wind damage. So those
who are planning to be in the southern Clearwater Mountains,
Bitterroot and Sapphire mountains and surrounding valleys should
plan to seek a "safe place" if a storm approaches from the west.

The heaviest rainfall is expected over central Idaho, continuing
rockslide/mudslide threats and swollen small streams, Friday
evening and night. One area in particular that could be under the
gun with heavy precipitation between 5 pm and 10 pm PDT extends
from Highway 95 Grangeville to Slate Creek east and north to
Lowell.

Models are trending toward a relatively mild and dry pattern over
the Northern Rockies Sunday through the middle of next week. The
pattern returns to active thereafter, with a series of weak storm
systems moving over the region. No one of these systems appears
significant for precipitation, however there is a wide spread in
model solutions depicted for the latter half of next week.
Temperatures will likely cool a bit during this active period.

&&

.AVIATION...Mostly dry conditions will exist across the Northern
Rockies air space throughout the next 24 hours. One exception to
the dry conditions will be along the Canadian border, where a few
rain showers may develop after 19/0300Z. Terrain will be obscured
at times across northwest Montana in response to the rain showers.
Otherwise, breezes will develop at area terminals for a times
this afternoon.

&&

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

$$