340
FXUS65 KTFX 081822
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1220 PM MDT Wed May 8 2024

Aviation Section Updated

.SYNOPSIS...
Rain and snow will decrease somewhat today over North Central
Montana, but warming air from the northeast may help some
scattered showers and thunderstorms to develop east of Interstate
15. Precipitation will continue off and on over and near the
Central Montana mountains and into Southwest Montana. Winds will
continue to be gusty into the overnight period as well. Overall,
high pressure aloft will help decrease precipitation tonight into
Thursday, bringing a warming and drying period for Friday through
the weekend.

&&

.UPDATE...

11:53 AM:

All Winter Weather Advisories have been cancelled. -IG


9:30 AM:

Rain is falling over the lower-elevations of North-central and
Central Montana. The Winter Weather Advisories along and north of
the Highway 200 Corridor were cancelled as a result. Snow continues
to fall along the Rocky Mountain Front and South- central and
Southwestern Montana. The rest of the Winter products remain the
same. See the TFX WATCHES/WARNINGS/ADVISORIES section below for
details. Across the lower-elevations of Southwestern Montana this
snow will continue through the morning hours before it will
transition to rain showers this afternoon. Patchy dense fog has
formed in Northern and Central Fergus County and will continue for
at least the next two hours. As a result a Special Weather Statement
was issued.

Pops were adjusted to better reflect current radar and satellite
trends. Dewpoints were increased to better reflect current
observations. Wind gusts were decreased to better reflect current
observations and trends. The rest of the forecast is on track.
-IG

&&

.AVIATION...
1220 PM MDT Wed May 8 2024 (08/12Z TAF Period)

Widespread rain and snow will affect Central ad Southwest MT into
the evening hours. IFR or lower conditions will also occur.
Conditions slowly improve overnight, as the showers become more
scattered. However, with any clearing, there is the possibility that
some fog could develop. Overall, mostly VFR conditions are expected
by 18z Thu for most areas. Mountains/passes will be obscured through
late Thu morning. Brusda

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

&&

.PREV DISCUSSION...
/ISSUED 543 AM MDT Wed May 8 2024/

Key Points:

- Main adjustment was to add Rocky Mountain Front plains and
  Meagher County valleys to Winter Weather Advisory

- Precipitation will continue through today then decrease
  overnight into Thursday

- High pressure aloft will bring a warmer and drier period
  starting this Friday

Today through Thursday... Widespread rain and snow is starting to
decrease somewhat from the northeast early this morning. However,
evaporative / dynamic cooling from the heavier precipitation has
caused snow levels to fall to the surface on the plains adjacent
to the Rocky Mountain Front, on the north facing slopes of the
Central Montana mountains, and into the valleys of Meagher County.
Additional accumulating snow of mostly 2 to 5 inches with the
persistent gusty northerly winds will continue difficult driving
conditions across these areas this morning, so have expanded the
Winter Weather Advisory to include all of these areas. The
northerly winds are showing signs of decreasing, but gusts mostly
in the 40 to 50 mph range continue across the area, so will leave
the High Wind Warning in effect until 6 am today. Otherwise,
warmer low- to mid- level air is being advected into the area in a
northeast flow aloft between the low pressure trough exiting the
area to the southeast and a building high pressure ridge to the
northwest. This has resulted in a rising of the snow level over
Blaine, Hill, Chouteau, and northern Fergus Counties. This warming
should help weakly destabilize the airmass there this afternoon,
bringing the threat for some weak thunderstorms. However, the
moisture will continue to move over the area, keeping the threat
for additional measurable snowfall in the mountains, so will allow
the Winter Warnings and Advisories continue there into this
evening. Overall, precipitation and wind should decrease from the
northwest overnight into Thursday as the high pressure ridge
continues building into Montana. This should also help warm
temperatures back closer to normal on Thursday.

Friday through next Wednesday... Ensemble guidance in good
agreement with having the Pacific high pressure ridge remaining
the dominant weather feature for this period. Temperatures are
forecast to warm back above normal on Friday and up to 15 degrees
above normal for the weekend. Much of the period should remain
mostly dry, but a disturbance riding over the ridge may bring a
few showers and thunderstorms on Sunday. A shortwave trough is
then forecast to gradually break down the ridge Tuesday into
Wednesday, helping to cool temperatures a bit and bring an
increasing chance for showers and thunderstorms. -Coulston

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  44  38  57  35 / 100  80  30   0
CTB  43  33  60  33 / 100  20  10   0
HLN  45  40  58  37 / 100  70  20   0
BZN  44  33  55  31 / 100  80  40  10
WYS  45  30  53  25 /  80  40  20   0
DLN  47  36  57  34 /  90  50  10   0
HVR  57  41  65  38 /  70  50  20   0
LWT  41  34  50  32 / 100  90  60  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until midnight MDT tonight for Big Belt,
Bridger and Castle Mountains-East Glacier Park Region-Gallatin
and Madison County Mountains and Centennial Mountains-Snowy and
Judith Mountains-Southern Rocky Mountain Front.

Blizzard Warning until midnight MDT tonight for Little Belt and
Highwood Mountains.

Flood highlights are in effect for portions of the CWA.

&&

$$

http://www.weather.gov/greatfalls