Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 242030
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
230 PM MDT Thu Apr 24 2014

.DISCUSSION...
Tonight through Saturday...Increasing clouds with a chance of
showers this afternoon as upper level energy and Pacific moisture
move across the region. Conditions dry up overnight before a
large low pressure system digs into the Western US Friday and
Saturday. Flow aloft turns to the SW ahead of the trough on Friday
with moisture and instability increasing by Friday afternoon. The
first showers and possibly a few isolated thunderstorms develop
over SW MT Friday afternoon, evolving into more widespread
precipitation across Central and North Central Montana Friday
night. A brief period of little activity is expected Saturday
morning before a second wave moves through the region later on
Saturday. Many locations look to get around hone half inch of
liquid with higher terrain and Southwest Montana maybe getting an
inch of liquid, some in the form of overnight snow. Temperatures
remain warm Friday but will cool Saturday. Winds will be breezy,
starting out westerly Friday before shifting easterly Saturday.

Saturday night through Thursday...Medium range models are in good
agreement for the early portion of the forecast period. Southern
portion of an upper level trough over the western USA is expected to
move slowly east-northeast Saturday night through Monday night and
gradually forms a cutoff low over the Great Plains. However, the
northern portion of this trough remains anchored along the British
Columbia coast forming a negative tilt trough that keeps the
Northern Rockies in an unsettled northwesterly flow aloft. This
pattern is expected to keep temperatures generally near seasonable
averages with showers lingering over the forecast area. Have updated
the forecast to increase pops for Saturday night and Sunday then
kept isolated to scattered pops in place through Tuesday. By Tuesday
night models begin to inch the closed low further east and build a
positive tilt ridge into the Northern Rockies. This is similar to
what was shown by the ECMWF for early to mid week last night but
models are now showing more of a dry northeast flow transitioning
into a better likelihood for western Montana to come under the
influence of the ridge axis. Have gone with a somewhat drier
forecast for Tuesday night through Thursday with model guidance in
better agreement in a slow warming trend. mpj

&&

.AVIATION...
UPDATED 1721Z.
VFR conditions will prevail through the forecast period. Showers
will obscure the mountains at times through Friday as a moist
southwest flow develops over the region. A few showers will move
into the plains and valleys this afternoon but will diminish this
evening with mainly scattered high cloudiness after midnight.
Langlieb

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  35  58  38  52 /  10  60  90  80
CTB  32  57  34  48 /  10  20  90 100
HLN  37  56  37  55 /  20  70  80  60
BZN  35  60  35  54 /  20  70  70  80
WEY  32  49  31  45 /  50  80  60  70
DLN  36  55  36  50 /  30  70  60  60
HVR  34  63  39  57 /  20  10  70  90
LWT  33  57  37  52 /  20  60  90  70

&&

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

$$

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