Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 010439
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1038 PM MDT Tue Sep 30 2014

Updated Aviation Discussion

.UPDATE...

Cluster of showers moving through the central forecast area
warranted an early update to the forecast grids through tonight.
Increased PoPs accordingly...primarily over eastern Cascade,
southern Chouteau, northern Meagher, Judith Basin, and Fergus
Counties through 06Z/Wednesday...the heaviest rain showers will
likely impact the region prior to 04Z. Showers over the entire CWA
look to become much less organized during the 06z-12z/Wednesday
period as a weak vorticity max moves east and the lower atmosphere
stabilizes. Uttech

&&

.AVIATION...
UPDATED 0438Z.
Upper level trough moving across the Northern Rockies and MT will
maintain scattered showers across most of Central and Southwest MT
tonight. Short duration MVFR ceilings and mtn obscuration are
expected in most areas with some lower ceilings and more persistent
shower activity affecting areas to the immediate north of the Little
Belt and Big Snowy Mtns, including areas between the KGTF and KLWT
terminals. Drier and more stable airmass moves in behind the exiting
upper level disturbance Wednesday morning, bringing clearing skies
Wednesday afternoon with VFR conditions prevailing at most locations
after 16Z Wed. Surface winds will remain from the NW tonight,
becoming W/SW Wednesday afternoon. Hoenisch

&&

.PREV DISCUSSION...
/ISSUED 520 PM MDT Tue Sep 30 2014/

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  42  58  36  48 /  50  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 /  40  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 /  80  30  10  40

&&

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

$$

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