Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 302320
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
520 PM MDT Tue Sep 30 2014

Updated Aviation Discussion

.DISCUSSION...

Tonight through Thursday...Watching two shortwave trofs that will
affect our weather through Thursday. The first...presently over
Idaho...will cause rain showers tonight over the N-central plains
associated with a surface trof pulling away from the Rocky
Mountain Front. Winds have shifted to the northwest behind this
front and will remain breezy tonight. A piece of this NW shortwave
is splitting south. Snow levels drop to around 6000 ft MSL early
Wednesday, so rain will change to snow mainly over the southwest
Mountains with up to 2.5 inches snow at the highest elevations of
the Madison Range. The NAM is an outlier in carrying an additional
patch of showers through the southwest Wednesday morning with the
upper level trof axis. All precipitation clears the CWA by
Wednesday afternoon and evening. The next shortwave trof arrives
on a strengthening northwest flow early Thursday. Precip moves
across the international border with the cold front Thursday
morning. Snow levels drop to the surface along the Rocky Mountain
Front. This activity moves through central Montana during the day
on Thursday and clears Thursday night. Nutter

Thursday night through Tuesday...An upper level ridge of high
pressure will gradually build over the Northern Rockies from Friday
through Sunday. This will be a weak upper level ridge...but
never the less drier and warmer air should move back into much of
the region. Afternoon highs will be near/slightly above seasonal
normals from Friday through Tuesday. The chances for precipitation
look to be minimal through the weekend...but an isolated shower
will be possible over the Rocky Mountain Front. Early next
week...the GFS tries to break down the ridge quicker than the EC
model. As a result...the GFS has precipitation over the northern
portions of the region...mainly north of Highway 2. For now...I
did introduce some very low pops in this region by Tuesday...but
confidence is low right now in how much precipitation might
actually fall. Brusda

&&

.AVIATION...
UPDATED 2320Z.
A moist and somewhat unstable NW flow aloft will persist over the
Northern Rockies and MT through Wednesday morning with the airmass
drying/stabilizing Wednesday afternoon. Numerous showers will
continue through early this evening, bringing brief precipitation
and short duration MVFR ceilings and mtn obscuration. Expect
coverage of showers to diminish after sunset but widely scattered
showers will continue into Wednesday morning. Drier air behind the
exiting upper level disturbance will bring clearing Wednesday
afternoon. Surface winds will remain from the NW tonight, becoming
W/SW Wednesday afternoon. Hoenisch

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  42  58  36  48 /  40  20  30  40
CTB  39  57  33  47 /  60  10  50  30
HLN  42  59  38  56 /  30  20  10  30
BZN  36  54  32  54 /  50  40  10  10
WEY  25  46  21  52 /  50  30  10  10
DLN  33  55  33  58 /  20  20  10  10
HVR  43  62  38  49 /  50  20  40  20
LWT  40  56  36  47 /  50  30  10  40

&&

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

$$

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