Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 260357
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
957 PM MDT Sat Mar 25 2017

UPDATED AVIATION SECTION

.UPDATE...

Forecast for the rest of tonight is in good shape. Isolated light
rain showers over portions of North-Central MT should dissipate
within the next few hours as the boundary layer stabilizes further
via nocturnal cooling. Otherwise, cannot rule out some additional
light rain and/or snow showers over higher terrain of Central and
Southwest MT due to westerly upslope flow and sufficient moisture
accompanying a passing weather disturbance. Per latest observed
temperature trends and model guidance, did not see the need to
adjust low temperatures.
Jaszka

&&

.AVIATION...
Updated 0357Z.

VFR conditions will continue over the forecast area through at least
Sunday evening. Weak high pressure aloft will keep some scattered to
broken mid level clouds over the mountains, while the plains remain
mostly clear. A weak disturbance will then bring increasing mid
level clouds and a few mountain showers after 00Z. Winds will remain
relatively light and out of the southwest.
Coulston

&&

.PREV DISCUSSION...
/ISSUED 520 PM MDT Sat Mar 25 2017/

Tonight through Monday...A disjointed upper level trough continues
to progress east across the western US and Canada with main
shortwave energy tracking across the 4-Corners region and SK this
evening while fairly weak energy moves across the northern Rockies
and MT. Enough instability is present late this afternoon for widely
scattered showers now developing over the western MT Mtns to track
east across portions of central and SW MT, primarily over the Mtns.
This activity should diminish fairly quickly later this evening as
the airmass stabilizes and shortwave ridging moves in from the west.
The ridge progresses east across MT Sunday for a period of dry
conditions across most of the forecast area with temperatures
remaining around 10 degrees above seasonal averages and relatively
light winds (less than 15 mph) making for a very pleasant spring
afternoon across all of north central and SW MT. Next Pacific
trough moves onto the west coast Sunday night and following the
trend of recent systems splits as it moves inland with the bulk of
the energy diving into the Great Basin Monday afternoon, while
weaker energy moves into the northern Rockies late Monday. An
inverted surface trough and weak front shift east into the
forecast area late in the day with best chance for showers across
SW MT and winds shifting to northwesterly. Hoenisch

Monday Night through Saturday...A progressive pattern will be in
place for much of the workweek. The northern piece of a splitting
trough exits the area Monday night into early Tuesday with lingering
mountain snow showers, mainly over the far southeastern areas. A
transitory upper ridge then builds over the area Wednesday. Beneath
this ridge, somewhat anomalous heights/temps and downsloping effects
should allow for a fairly mild day, potentially the mildest of the
week. Given these factors, went a bit above guidance for highs.

The ridge is then followed by a fast-moving yet digging upper level
system that will dive from the Northeast Pacific to the Southwest US
and close off into an upper low. This will bring unsettled weather
to our region in the late-week timeframe (ie THU/FRI) with the
potential for a more widespread precipitation event, especially
Southwest Montana and southern sections of central MT. Temperature
trends during this period have been warmer, indicating more of a
rain threat at lower elevations. Of note, a more widespread precip
combined with mild temperatures next week could lead to some
hydrology concerns, but it is too early to get too specific on this
threat, especially since the models could easily trend further
south/drier with the system. But, something to keep an eye on. By
next weekend, a drier/breezy pattern looks to develop along with
slightly cooler temperatures potentially.
Cassell/Martin

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  31  57  34  59 /  10   0  10  30
CTB  28  51  30  54 /   0   0  10  20
HLN  32  56  35  55 /  30   0  10  50
BZN  30  54  34  55 /  30  10  20  40
WEY  16  38  26  41 /  30  10  50  60
DLN  28  51  33  51 /  10   0  20  50
HVR  30  56  31  59 /   0   0   0  20
LWT  30  53  34  56 /  20  10  10  30

&&

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

$$

weather.gov/greatfalls



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