Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 260603
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1150 PM MDT MON JUL 25 2016

Aviation Section Updated.

.UPDATE...

Shortwave weather disturbance in westerly flow aloft moving
across MT this evening with scattered thunderstorms. Bulk of the
Thunderstorm activity will be concentrated north of I90 and south
of Hwy 87 across central MT through midnight with a gradual
decreasing trend in coverage and intensity expected through then
as well. Precipitable water values have increased to between
0.75" to 1" and brief heavy rain is occurring with stronger storm
cells, in addition to small hail and wind gusts to around 40 mph.
Thunderstorm activity currently in SW Alberta will also track east
through the overnight with period and may approach far NE portions
of the forecast area by early Tuesday morning. Have made
adjustments to pop/wx grids through the rest of tonight to capture
these trends, otherwise forecast is in good shape. Hoenisch

&&

.AVIATION...
Updated 0550Z.

Weak weather disturbance moving east across central/SW MT will
produce isolated thunderstorms through around 09Z. VFR conditions
will prevail otherwise with generally light surface winds and
clearing skies overnight. Thunderstorm activity will increase again
Tuesday afternoon with more widespread coverage anticipated over
North-central MT. PN

&&

.PREV DISCUSSION...
/ISSUED 535 PM MDT MON JUL 25 2016/

Tonight through Wednesday...A shortwave trough embedded within
zonal flow aloft will move eastward over our CWA this afternoon
through Tuesday morning. Scattered showers and thunderstorms will
accompany this disturbance, especially before midnight tonight. The
best chance for this activity exists over and near higher terrain.
Strong wind gusts may accompany these storms.

On Tuesday and Wednesday, additional scattered showers and
thunderstorms are expected, especially in the afternoon and evening,
as two more eastward-moving shortwave troughs affect the region.
Convection will likely initiate over the higher terrain by early to
mid-afternoon of both days before moving generally eastward over the
nearby plains and valleys. Model soundings indicate moderate deep
layer shear, appreciable instability, and downdraft CAPE near 750-
1000 J/kg should yield some stronger storms capable of small hail
and strong to perhaps marginally severe wind gusts.

Most locations will have lows in the 50s and highs in the mid 80s
to lower 90`s tonight through Wednesday. Jaszka

Wednesday Night through Monday...Showers and thunderstorms look to
continue into Wednesday night as a strengthening LLJ brings fast
SE flow into eastern portions of our CWA. A decent jet aloft and
modest cape values could support a few isolated stronger storms
for Wednesday evening and into the early overnight hours. Wind and
perhaps some hail will be the main concerns. Weak troughing will
continue across the area for Thursday...bringing a weak cold
front...and perhaps producing more isolated to scattered
thunderstorm activity across the CWA during the afternoon and
evening hours. Shear and abundant moisture will be lacking with
this front...making severe storms hard to come by. NW flow
transitions to more of a westerly and dry flow on
Friday...bringing warming and dry conditions. Models starting to
hint at the return of more monsoonal moisture than recently
thought for this weekend. This could bring isolated to widely
scattered thunderstorm activity Saturday...mainly across sw
portions...and possibly into central MT. Another round of
thunderstorms looks to be possible Sunday across much of the CWA
as monsoonal moisture continues...and a weak front moves across
the area. This front could then bring dry conditions...and
elevated fire concerns early next week...especially across
northern and western portions...with some lingering moisture
possibly producing a few isolated thunderstorms in eastern and
southern portions. Slight chances for pops were added in for the
weekend...however...confidence remains low on exactly how abundant
this monsoonal moisture will be. Temps will begin to warm
Thursday...and should be in the 90s this weekend. Slightly cooler
conditions in the mid 80s are then possible early next week behind
Sunday`s front. Anglin

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  58  88  57  86 /  30  20  20  20
CTB  56  83  54  81 /  20  50  20  30
HLN  61  87  61  90 /  50  20  20  20
BZN  54  88  53  88 /  30  20  20  20
WEY  46  80  44  79 /  10  20  20  10
DLN  54  84  53  87 /  30  20  10  10
HVR  61  88  60  84 /  20  20  60  30
LWT  58  83  58  82 /  40  40  30  30

&&

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

$$

weather.gov/greatfalls


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