839
FXUS65 KTFX 090249
AFDTFX

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

.SYNOPSIS...

Snow and rain will end from northeast to southwest by Thursday
morning. Across North-central and Central Montana patchy dense fog
is possible this evening through Thursday morning in areas where
skies clear. North-central, Central, and Southwestern Montana
will dry out and warm up Thursday afternoon through the weekend.
By the middle of next week the weather pattern could change.

&&

.UPDATE...

With this update, some adjustments were made to the precip to
better reflect the latest trends in observations and model data.
Patchy fog was also added across portions of the hi-line and
central Montana for tonight and tomorrow night. Widespread, major
visibility reductions are not expected, however, some patches of
dense fog are possible overnight along the US-2 and US-87
corridors.

-thor

&&

.AVIATION...
600 PM MDT Wed May 8 2024 (09/00Z TAF Period)

North-central Montana (KCTB, KHVR): VFR conditions will prevail
through the TAF period with some vicinity rain showers near KHVR
possible through 09/09Z. Otherwise, the precipitation will continue
progressing southward away from the hi-line. Gusty winds are
expected to continue through around 09/03Z before tapering off below
15kts.

Central Montana (KGTF, KHLN, KLWT): MVFR conditions are expected to
prevail at KGTF and KHLN through at least Thursday morning with the
possibility of IFR or lower in passing rain showers. Mountains and
passes will be obscured through much of the TAF period. Meanwhile at
KLWT, fog and low clouds are expected to prevail through at least
Thursday morning with IFR or lower expected during this time. There
is a possibility of fog developing around KGTF, however, at this
time confidence was not high enough to include it in the TAFs.

Southwest Montana (KBZN, KEKS, KWYS): Rain and snow showers are
expected to impact KBZN and KEKS through most of the TAF period with
IFR or lower possible through the period. KWYS will generally stay
dry and fluctuate between VFR and MVFR through the TAF period.
Mountains and passes will be obscured through at least Thursday
afternoon.

-thor

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

&&

.PREV DISCUSSION...
/ISSUED 600 PM MDT Wed May 8 2024/

This afternoon through Thursday... Rain/snow will
continue through the evening along the Highway 200 Corridor and
south. Precipitation will end from northeast to southwest by
Thursday morning. There will also be isolated rain showers across
North-central Montana through this evening. Snow will continue
along the Southern Rocky Mountain front through this evening.
Patchy dense fog has formed in Northern and Central Fergus County
and will continue through Thursday morning. At times visibility
will be reduced to a quarter mile or less. Patchy dense fog could
form in other locations of Central and North-central Montana if
skies clear overnight due to all the moisture from this system. A
Winter Weather Advisory has been issued for the Madison River
Valley and Gallatin Valley until midnight due to snowfall reducing
visibility down to a half mile at times. The Blizzard Warning for
the Little Belts and Highwood Mountains has been downgraded to a
Winter Storm Warning due to the strong winds and wind gusts having
ended. The snow has ended for the Highwood Mountains. The Winter
Storm Warning along the Northern Rocky Mountain front has been
cancelled due to the snow having ended. The Winter Storm Warning
along the Southern Rocky Mountain Front has been downgraded to a
Winter Weather Advisory. For more details see the TFX
WATCHES/WARNINGS/ADVISORIES section below. On Thursday an upper-
level trough begins to move out of the area. This will begin to
warm up and dry out North-central, Central, and Southwestern
Montana.

Friday through Sunday... On Friday an upper-level ridge begins to
move over North-central, Central, and Southwestern Montana. This
will warm temperatures up to about seasonal averages across the
area. This upper-level ridge will stay in place above North-central,
Central, and Southwestern Montana through the weekend which will
keep temperatures dry and allow temperatures to warm up to above
seasonal averages across the area through the weekend. Isolated
locations of North-central and Central Montana and the Helena Valley
have a 50 - 65% chance for having temperatures of 80 degrees or
warmer.

Monday through next Wednesday... On Monday cluster analysis
indicates that there will be upper-level zonal flow over North-
central, Central, and Southwestern Montana. This will keep the
area`s weather about the same on Monday as Sunday. On Tuesday three
clusters (86% of ensemble members) have a week upper-level trough
over North-central, Central, and Southwestern Montana. One of the
clusters (14% of ensemble members) has an upper-level ridge over
North-central, Central, and Southwestern Montana. This indicates
that the weather pattern could change on Tuesday. Next Wednesday the
ensembles begin to diverge and so the weather over North-central,
Central, and Southwestern Montana is uncertain at this time. -IG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  34  56  33  64 /  70  40   0   0
CTB  31  59  31  70 /  20   0   0   0
HLN  39  56  36  70 /  70  30   0   0
BZN  33  51  31  64 /  80  50  10   0
WYS  28  51  25  61 /  40  30   0   0
DLN  35  55  33  66 /  70  20   0   0
HVR  40  64  38  70 /  50  20   0   0
LWT  32  48  31  58 / 100  50  10   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until midnight MDT tonight for Gallatin
Valley-Madison River Valley-Southern Rocky Mountain Front.

Winter Storm Warning until midnight MDT tonight for Big Belt,
Bridger and Castle Mountains-Gallatin and Madison County
Mountains and Centennial Mountains-Little Belt and Highwood
Mountains-Snowy and Judith Mountains.

&&

$$

http://www.weather.gov/greatfalls