Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 221549
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
949 AM MDT Wed Mar 22 2017

.UPDATE...

Weak upper level disturbance has exited the region this morning.
In its wake are a few areas of patchy fog and very isolated
mountain rain or snow showers. Satellite and webcams showing
patchy fog still lingering across Monida Pass and where Chouteau,
Blaine, and Fergus counties meet up. Continued patchy fog through
the morning, but feel it should dissipate quickly around noon.
Overall a fairly warm and dry day is expected today...with only a
few mountain showers. A mid level cold front will bring some weak
instability this afternoon and evening...possibly providing a few
isolated to scattered showers and maybe even a thunderstorm. Best
chances will be across southwest MT. Confidence is low for
thunderstorms. There is weak instability and modest lapse
rates...however...strong shear may actually hurt convection today.
Added an isolated mention to areas with the best, but still low,
chances for weak thunderstorms. Anglin

&&

.AVIATION...
Updated 1145z.
Light rain showers are moving northward through Central MT this
morning, with some patchy fog around the region. Expect clearing by
mid morning, with VFR conditions prevailing after late morning.
Mainly just some passing clouds overnight, with a small chance for
showers redeveloping by 12z Thu over the Rocky Mountain Front.
Brusda

&&

.HYDROLOGY...
Updated 400 AM.

No changes this morning to the current hydro highlights.

1. The flood warning for an ice jam on the Big Hole River around
Wise River continues. Some problems continue around Dickey Bridge.
This is a very unpredictable problem/impact with the latest river
observations in the vicinity still showing some erratic effects
from ice. Elsewhere on the Big Hole River, expect high flows over
the next few days, with the potential for additional ice jams.

2. The flood warning continues for Lodge Creek north of Havre. It
has been trending down over the past 36 hours, and it could take
until this evening or a bit later to fall below flood stage.

3. The flood warning continues for the Milk River near Harlem.
This gauge has fallen just below flood stage, but it has remained
nearly steady over the past 12 hours. Thus, a high amount of
water continues to flow through the system, and some minor
flooding impacts are likely to continue today for areas east of
Chinook through Fort Belknap.

Brusda

&&

.PREV DISCUSSION...
/ISSUED 545 AM MDT Wed Mar 22 2017/
Today through Friday...A surface warm front is moving northward
through the region this morning. Warm air as moved in aloft
already, with snow levels generally above 7000 feet. The light
showers generally affecting areas mainly east of a Helena to Ennis
line as of 345 AM. These showers will diminish quite a bit by
9 AM. Some freezing rain could mix in for areas along/north of
Highway 2 this morning with road temperatures near freezing, but
precipitation amounts will be light. Otherwise, warmer air moves
in at the surface for this afternoon, with highs climbing into the
60s. A southwest to westerly flow aloft will then reside over the
region from tonight through Friday. The storm system for
Thursday/Thursday night continues to look like most of
precipitation will stay south of our region, with mainly just the
West Yellowstone/ Big Sky area getting a passing shower.
Afternoon temperatures will cool a touch on Thursday into the
50s, only to rebound back into the 60s on Friday. There will be a
small chance for showers by late Friday afternoon over the front
range of the Rockies as the next upper level trof approaches the
region. Brusda

Friday Night through Wednesday...A large scale, but weakening
Pacific trough moves inland Friday night. Orographic precipitation
is likely to develop up to the Continental Divide by Saturday
morning, with snow levels dropping below about 6000 ft. Several
smaller shortwaves will move through this unsettled west-southwest
flow. Models are converging on a solution that would favor rain and
mountain snow across Southwest Montana Saturday afternoon. Some
solutions are wetter than others, but ensemble averages support
around one-tenth to one-quarter inch of liquid QPF and 2-4 inches of
snow above 7500 feet. Fair weather returns for Sunday as an upper
level ridge axis amplifies and crosses the state.  The overall
pattern remains progressive, with another large scale Pacific trough
spreading moisture across the intermountain west Monday or Tuesday.
Model solutions diverge widely late in the period, though favoring a
return to fair weather for Wednesday. Temperatures remain slightly
above average through the period. PN

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  60  36  56  32 /  10   0   0   0
CTB  54  34  51  27 /  10   0   0   0
HLN  57  35  54  31 /  10  10   0   0
BZN  56  34  52  29 /  20  10  10   0
WEY  40  25  40  20 /  40  20  20  10
DLN  55  33  51  29 /  20  10  10   0
HVR  62  36  57  29 /  20   0   0   0
LWT  59  35  52  30 /  10  10  10   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

weather.gov/greatfalls



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