Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 202053
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
253 PM MDT Wed Aug 20 2014

.DISCUSSION...

Tonight through Friday...A deepening upper-level trough of low
pressure will bring a period of widespread, prolonged
precipitation across the area beginning late tonight through
Friday. The Canadian surface cold front remains north of the
International Border and is expected to cross the border between 5
pm and 8 pm this evening. Instability and Pacific moisture ahead
of the front will lead to scattered showers and thunderstorms this
afternoon and evening. Some thunderstorms could produce gusty
winds up to 30 mph, small hail and heavy rain. This activity will
diminish after sunset before steadier rainfall develops behind
the frontal passage. The first period of rainfall will occur late
tonight into Thursday morning, then there should be a break from
midday Thursday through Thursday evening before the next round of
widespread precipitation occurs Thursday night into Friday. The
airmass will cool further Thursday night with snow levels lowering
to around 8000 feet in Glacier National Park. The coolest period
will be Friday night into Saturday morning as snow levels lower to
6500 feet in Glacier National Park. Total precipitation through
Friday will be near one inch, however an additional inch of
precipitation is possible through Sunday morning. High
temperatures will be 20 to 30 degrees below seasonal averages with
highs in the 60s Thursday and Friday. MLV

Friday Night through Wednesday...Medium range models are in good
agreement that wetter and much cooler conditions will prevail
through the weekend. Objective guidance temperatures continue to
trend cooler keeping high temperatures in the 50s and 60s Saturday
and Sunday. Overnight lows will be cold enough to support minor snow
accumulations over the highest elevations of Glacier Park, but it
does not appear that any significant impacts should be expected.
Models are in better agreement for the Monday through Wednesday
period with upper level troughing remaining over the Northern
Rockies through Tuesday. Unsettled conditions will keep isolated to
scattered showers and thunderstorms in the forecast but temperatures
are expected to warm back toward the 70s. By Wednesday the trough
will finally progress eastward allowing shortwave ridging to build
over Montana and temperatures to trend back toward seasonal
averages. mpj

&&

.AVIATION...
UPDATED 1751Z.
As low pressure develops over the Northern Plains, a cold front will
push southward through the forecast area this aftn and tonight.
Chances for sct SHRA/TS will increase into this evening and tonight.
Periods of MVFR/IFR are possible mostly after 06z/Thursday as
ceilings lower. Foltz/Uttech

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  55  66  51  64 /  80  80  60  90
CTB  51  58  47  57 /  80  80  60  90
HLN  54  72  51  67 /  70  80  60  90
BZN  50  73  49  70 /  50  80  60  70
WEY  43  63  42  59 /  50  50  50  40
DLN  47  73  45  66 /  50  50  50  70
HVR  57  66  53  67 /  80  80  60  80
LWT  54  65  50  61 /  70  70  60  80

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

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