Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 221113
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
513 AM MDT Thu Jun 22 2017

Aviation Section Updated

.SYNOPSIS...

Near to below normal temperatures will continue across the region
through the first half of the weekend, but will be followed by a
warming trend late in the weekend and into early next week. A few
showers and perhaps a thunderstorm will move through central
Montana at times over the next few days. Drier conditions are
expected by Sunday and Monday.

&&

.DISCUSSION...

Today through Friday Night...Satellite and radar imagery this
morning show a few lingering showers moving across central Montana
associated with residual mid level moisture and weak lift. As the
shortwave responsible for the showers pulls away from the area,
there should be a gradual decrease in clouds/showers for a brief
time this morning. However, a stronger shortwave upstream in
central Alberta will quickly drop south, reaching the Hiline
early this afternoon, then progressing through the remainder of
the area through tonight. Despite the drier air in place at this
time, there appears to be a modest amount of moisture in Canada
which should advect into our forecast area this afternoon. Models
have been struggling with shower activity lately, and I feel they
are once again under-doing POPs/QPF with this wave. For this
reason, I upped POPs across central Montana where the best combo
of moisture/lift/convergence is expected. Later forecasts may need
to adjust POPs up even more if confidence increases.

On Friday, another round of showers may develop, especially near
GNP, thanks to a redeveloping low level upslope/moist flow.
Showers could extend east out over the plains, but wasn`t
confident enough to go with higher POPs for now. Unseasonably
strong SFC highs will build in tonight and again Friday night.
Clouds should tend to limit how cool it gets across central
Montana, but clear skies in the SW should allow good radiational
cooling, especially valleys. For this reason, I lowered min temps
the next couple of nights there. The coldest valleys could see
low-mid 30s. MARTIN

Saturday through Wednesday...Area remains under a NW flow aloft
Saturday as the large scale upper level trough progresses east across
the N-central CONUS. Though models are pretty limited in terms of
precip/coverage on Saturday, opted for at least slight chance pops
Saturday as embedded shortwave and upper jet energy combined with
somewhat unstable and cyclonic NW flow aloft should support some
afternoon shower and isolated thunderstorm development. Heights rise
Sunday and Monday as an upper level ridge briefly amplifies and
shifts east across the Northern Rockies and MT ahead of the next
trough from the NE Pacific approaching the West Coast. Afternoon
temperatures still slightly below seasonal averages Saturday warm to
above average by Monday and Tuesday of next week. Still a fair
amount of variability among models with the progression of the
Pacific trough inland by the middle of next week. However in any
case the upper ridge looks to weaken or be replaced by a weak trough
with an influx at at least limited moisture and shortwave energy
from the west/southwest for an increase in cloud-cover and potential
for afternoon shower/thunderstorm development. Hoenisch

&&

.AVIATION...
Updated 1113Z.

Clouds and SHRA over central MT should diminish over the next few
hours. After a brief break, clouds will push back into the area from
Alberta as a stronger shortwave drops south through the area. This
wave will likely bringing at least isolated SHRA to central MT. SHRA
should be light enough to not cause significant reductions in VIS,
but it may bring lower, but still VFR, CIGS. Off and on SHRA may
continue into tonight. Across SW MT terminals, no precip is expected
at this time. It will be breezy at all terminals, especially this
afternoon, before high pressure builds in tonight with decreasing
winds. MARTIN

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  67  41  68  44 /  20  20  10  10
CTB  62  41  66  43 /  20  20  20  20
HLN  71  44  72  45 /  10  10  10  10
BZN  72  38  71  44 /   0   0   0  10
WEY  68  32  67  35 /   0   0   0   0
DLN  71  38  72  43 /   0   0   0   0
HVR  66  42  71  44 /  20  20  10  10
LWT  65  39  65  40 /  10  20  10  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

weather.gov/greatfalls


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