Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 300359
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
859 PM MST Thu Jan 29 2015

.UPDATE...

An upper level ridge of high pressure extending north through the
interior western US will maintain a dry NW flow aloft over the
region tonight. Mid-high level clouds associated with a very weak
disturbance moving east through the upper ridge should move off to
the east of the region later tonight. So far this evening,
temperatures have been somewhat slow to cool over much of
central/SW MT, however with decreasing cloud-cover have opted not
to update minimum temperatures tonight as additional cooling is
anticipated. Potential fog development is still expected in the
Milk River Valley, including Havre and Chinook where temp/dewpoint
spread is small and winds will remain fairly light. Forecast
handles this well with no updates planned this evening. Hoenisch

&&

.AVIATION...
UPDATED 2334Z.
Central Montana will remain underneath high pressure aloft through
Friday and the airmass will remain dry with light surface winds. Fog
will likely develop again along portions of the Hiline, including
KHVR, towards midnight. Local IFR cigs and vsbys are possible until
mid-morning. Elsewhere VFR conditions will prevail for the next 24
hours.

&&

.PREV DISCUSSION...
/ISSUED 436 PM MST Thu Jan 29 2015/

Tonight through Saturday...A weak, split northwesterly flow aloft
will maintain fair weather over North-central and southwest Montana
through Friday. Temperatures remain above seasonal averages.
Persistent freezing fog was noted along the Hi-Line this morning.
Conditions will persist overnight, so have added patchy freezing
fog overnight. Ridging amplifies over the Pacific Northwest on
Saturday. A weak shortwave trof moving quickly through this flow
will trail a cold front into north-central Montana Saturday
morning. Temperatures will drop below average on Saturday behind
the front. Shallow upslope precipitation will develop behind this
front. Moisture is limited in the northwest flow, so snowfall
amounts will be generally one-half to two inches. Winter weather
headlines are not warranted at this time, but will continue to
monitor. Dry weather persists in the southwest will near normal
temperatures. Nutter

Saturday Night through Thursday...Light snow showers will
continue Saturday night as an upper-level disturbance continues
to move through the area. Additional snow accumulations Saturday
night into Sunday morning will be less than an inch. Beginning on
Sunday, the flow aloft becomes west-northwesterly as a Pacific
weather system pushes into the Northern Rockies. Increasing
Pacific moisture and milder airmass associated with this system
will move over a cooler airmass at the surface across north-
central and southwest Montana with the possibility for mixed
precipitation on Monday morning, however forecast confidence
remains low. Models also coming into better alignment for Tuesday.
Shortwave energy looks stronger and have raised precipitation
chances. Also, the surge of colder air into the area late Tuesday,
combined with the expected snow, has resulted in colder
temperatures for Wednesday morning.

Though long-range forecast models indicate that an active weather
pattern may persist through the remainder of the week, there
remains a lot of uncertainty regarding temperatures, precipitation
coverage and amounts. The ECMWF is the colder and wetter solution,
while the GFS keeps drier, yet unsettled northwest flow over the
Treasure State with temperatures near seasonal averages. Given
these differences, have kept PoPs near climo and temperatures
slightly cooler than seasonal averages. MLV

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  28  45  24  30 /   0   0  10  50
CTB  25  44  22  24 /   0   0  20  50
HLN  21  40  20  35 /   0   0  10  30
BZN  18  39  17  35 /   0   0  10  20
WEY  10  36   7  35 /   0   0   0  10
DLN  21  43  21  44 /   0   0   0  10
HVR  22  40  22  25 /   0   0  20  70
LWT  25  42  21  30 /   0   0  10  60

&&

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

$$

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