Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 202050
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
250 PM MDT Thu Jul 20 2017

.DISCUSSION...The hot, dry and windy conditions are expected to
continue into this evening, with even breezy winds likely to
remain well into tonight as the cold front pushes slowly east.
Fortunately, Friday will bring a welcome return, albeit brief, to
normal temperatures. But still, dry remains the theme.

Temperatures will be rather quick to rebound this weekend, rising
to some 10 degrees above normal yet again. Low temperatures this
weekend will quickly warm throughout the terrain and mid-slopes,
but still decent overnight cooling expected in the valleys.
Sunday is likely to be the hottest day in this stretch with many
central Idaho and western Montana valleys experiencing
temperatures well into the 90s and some of the lowest elevations
in Idaho near the Oregon border eclipsing the century mark. At the
same time, however, mid level monsoonal moisture will be slowly
seeping into Lemhi County and far SW Montana. Cumulus development
seems likely and there may even be a dry thunderstorm or two.
Monday appears to be nearly as warm, but with a little bit more
atmospheric moisture. So we anticipate better chances for
afternoon/evening thunderstorms, though they may still remain
somewhat isolated in coverage. These storms are likely to be quite
dry as all data would suggest vast dewpoint depressions and a
classic inverted-V sounding profile; a key marker for a gusty wind
threat with any storms.

By Tuesday forecast models are showing the potential for an
impressive area of monsoonal moisture tracking towards the
Northern Rockies. While the ECMWF remains somewhat tempered with
it`s moisture fields, keeping the deep monsoonal feed more so over
Idaho and Wyoming, the GFS shows a rapid increase in moisture that
would result in widespread showers and thunderstorms. In fact, the
GFS times this moisture quite nicely with an ejecting wave that
should be lingering off the California coast this weekend and
ultimately creates a favorable environment for potentially severe
thunderstorms and a heightened risk of flash flooding.
Accordingly we have pushed PoPs upwards, especially across SW
Montana where models all agree convection should be present by
Tuesday. The threat for convection could prove to be present on
Wednesday and even Thursday as SW flow aloft maintains an active
moisture feed over the region. We maintain climatological chances
for precipitation through Thursday, but the details for this time
frame remain hazy due to model inconsistency.

&&

.AVIATION...Breezy westerly winds will continue for TAF sites
through sunset, with sustained winds of 15-20 kts and gusts to
25-30 kts. Few to scattered mid-level cumulus and smoke/haze due
to surrounding wildfires will also continue today. Hazy conditions
and occasional breezy winds are possible for the night.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Red Flag Warning until 9 PM MDT this evening East Lolo.

     Red Flag Warning until 9 PM MDT this evening Deerlodge/West
     Beaverhead...East Beaverhead.

ID...&&

$$


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