Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 200934
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
334 AM MDT Sat Sep 20 2014

.DISCUSSION...

Today through Monday...The current gusty west winds across north
central Montana, especially along the Rocky Mountain Front, will
decrease today as a shortwave trough aloft and an accompanying
weak surface boundary both move east out of the area. Otherwise,
high pressure aloft will build into the area in the wake of the
shortwave, which will steadily warm temperatures. Highs around 5
degrees above normal today will warm to between 10 and 15 degrees
above normal by Monday. The subsidence from the high pressure
will also keep most of the area dry through the period. However, a
cut off low pressure area, currently along the California coast,
will be lifted northeast by large upper level trough approaching
the Pacific coast. This cut off low will move into southern Idaho
Sunday night then east into Wyoming on Monday. This system will
drag Pacific moisture from off the Mexican coast north into
Montana, bringing a good chance of showers and thunderstorms to
southern Montana Sunday night into Monday. Instability is moderate
at best, so strong thunderstorms with small hail are possible but
uncertain at this time. However, moisture may be significant
enough to cause brief heavy rainfall with storms.
Coulston

Monday Night through Saturday...Remnants of the weakening cut-off
low drift away to the east as an upper level ridge begins to
amplify over the Intermountain west. This will result in fair and
warmer conditions through early Thursday. The upper ridge axis
moves east of the region on Thursday as heights begin to fall
ahead of a broad synoptic trof advancing through the Pacific
Northwest. Isolated showers and thunderstorms will begin to
develop Thursday evening with decreasing stability over the higher
terrain of western and southwest Montana.

Models maintain overall good consistency through Friday. The GFS
moves the trof axis a bit faster than the ECMWF. Ensemble means and
extended guidance from NWS WPC tends to favor the GFS guidance for
the end of the forecast period. In general the forecast reflects
temperatures returning to seasonal averages with above average
chances for precipitation.
Nutter

&&

.AVIATION...
UPDATED 0450Z.
Dry northwest flow aloft will continue overnight as well as Saturday
as high pressure builds over the western U.S. Winds will remain
generally light. VFR conditions prevail.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  73  46  77  49 /   0   0   0   0
CTB  71  42  76  43 /   0   0   0   0
HLN  77  46  79  49 /   0   0   0  10
BZN  74  41  75  46 /   0   0   0  20
WEY  70  33  71  38 /   0   0  10  50
DLN  75  45  77  51 /   0   0  10  20
HVR  74  44  78  45 /   0   0   0   0
LWT  71  45  75  47 /   0   0   0  10

&&

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

$$

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