112
FXUS65 KTFX 302343
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
540 PM MDT Tue Apr 30 2024

UPDATED AVIATION SECTION

.SYNOPSIS...

A wintry spring storm brings periods of rain and snow to the area
through Friday morning. Temperatures cool to below normal values,
before warming, a bit, this weekend.

&&

.DISCUSSION...

420 pm Update...Have issued a High Wind Warning for the part of
North Central Montana covering portions of Toole, Pondera, Liberty,
Teton, Chouteau, and Hill Counties until 7 pm this evening. A
disturbance moving through the area is causing more widespread winds
of 30 to 40 mph gusting to 65 mph. Convective showers are helping to
translate strong mid-level winds from the disturbance down to the
surface. Will monitor the situation to see if further expansion of
the Warning will be necessary. -Coulston

Note: The forecast area for the National Weather Service Great
Falls Weather Forecast Office includes north central, central and
southwest Montana.

The next weather producer is upon us, offering below normal
temperatures and periods of rain/snow, into Friday. As of the
writing of this discussion, showery precipitation has begun, with
a few thunderstorms presenting across portions of the region.
Westerly winds flowing across The Northern Rocky Mountain Front
allow for some gusty winds to 40 mph. The Winter Storm Watch for
The Little Belt and Highwood Mountains has been upgraded to a
Winter Storm Warning. In this area, 7 to 13 inches of snow is
forecast at pass level. Please, see WATCHES/WARNINGS/ADVISORIES
section below for Winter Weather Highlights already in place.
- Fogleman

The larger scale closed upper level low moves east of the Rockies
tonight with its circulation shifting slowly across MT/AB/SK
through Thursday. Models are in general agreement and continue to
trend somewhat slower with the arrival of more widespread
precipitation circulating into the forecast area. Widespread
precipitation develops across southern AB/SK in association with a
TROWAL (trough of warm air aloft) and shifts southwest into areas
along the east side of Glacier NP by Wednesday morning. Colder
air aloft wraps into the circulation Wednesday with widespread
precipitation expanding south and east across much of north-
central MT by Wednesday afternoon with moist/cyclonic NW flow now
forecast to linger across the area through at least Thursday
afternoon. This has shifted the more impactful period of winter
precipitation for portions of central MT to late Wednesday through
Thursday, though precipitation amounts have not changed
significantly.

Winter storm warnings and advisories for The Glacier NP/Rocky Mtn
Front vicinity begin at midnight tonight with areas near the AB
border being initially impacted tonight before precipitation spreads
south on Wednesday. Winter weather advisories were added for the Big
Belt/Bridger and Snowy mountain ranges beginning Wednesday afternoon
with the Winter Storm Watch for the Little Belts continuing while
these highlights were extended through Thursday afternoon. There is
some potential for additional winter weather highlights across
portions of central MT adjacent to the Little Belts but considerable
uncertainty exists at these lower elevations due to marginal
temperatures with melting and compaction likely to limit
accumulation and impacts to roads. Still, the later onset of
precipitation towards Wednesday night and Thursday could allow for
some overnight accumulation and minor winter weather impacts to the
Thursday morning commute that will need to be watched.

Models continue to delay the exit of troughing from the area through
Friday though the bulk of the widespread precipitation should be
ending Thursday night. A brief period of ridging is possible early
this weekend before the next round of troughing arrives late this
weekend into early next week with models suggesting temperatures
remaining closer to seasonal averages for  this period. Hoenisch

&&

.AVIATION...
540 PM MDT Tue Apr 30 2024 (01/00Z TAF Period)

VFR conditions will mostly continue over North Central (KCTB KHVR),
Central (KLWT KGTF KHLN), and Southwest (KBZN KEKS) Montana through
at least 02/00Z.

A low pressure area will linger over southern Alberta and
Saskatchewan through around 16Z, continuing a westerly flow aloft
that will cause periods of mountain wave turbulence. A disturbance
moving through the flow will also cause gusty northwest winds across
much of the area through around 06Z. The strongest wind gusts (up to
45 kt) will occur over the plains of North Central Montana and with
scattered showers moving over the area. These showers may also cause
brief periods of MVFR/IFR in heavier precipitation and blowing snow.
Showers and winds should mostly decrease after 06Z. However, another
disturbance will swing around the low pressure center after 16Z,
bringing another round of westerly winds and scattered showers with
periods of MVFR conditions after 18Z as the airmass becomes weakly
unstable again. However, precipitation, MVFR conditions, and
mountain obscuration will likely be more widespread on the Hi-Line
as the Canadian low pressure area starts to drift south. -Coulston

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  29  51  32  45 /  10  70  80  90
CTB  29  46  32  43 /  30  80  80  80
HLN  32  53  36  51 /  10  50  50  70
BZN  26  48  29  50 /  50  50  40  60
WYS  22  40  19  43 /  40  60  40  50
DLN  25  45  28  50 /  30  40  10  30
HVR  29  54  33  48 /  20  60  70  80
LWT  27  48  28  41 /  10  50  60  80

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until 7 PM MDT this evening for Eastern
Pondera and Eastern Teton-Eastern Toole and Liberty-Hill County-
Western and Central Chouteau County.

Winter Storm Warning from midnight tonight to noon MDT Thursday
for East Glacier Park Region.

Winter Weather Advisory from midnight tonight to noon MDT
Thursday for Northern High Plains-Southern Rocky Mountain Front.

Winter Storm Warning from 6 AM Wednesday to 6 PM MDT Thursday
for Little Belt and Highwood Mountains.

Winter Weather Advisory from noon Wednesday to 6 PM MDT Thursday
for Big Belt, Bridger and Castle Mountains-Snowy and Judith
Mountains.

&&

$$

http://www.weather.gov/greatfalls