895
FXUS65 KGGW 230924
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
224 AM MST Mon Dec 23 2024

.DISCUSSION...

KEY MESSAGES:

 - Freezing fog this morning along the Hi-Line. Fog will partially
   clear from west to east this afternoon. But then return to the
   same river valleys tonight.

 - Stretch of above normal temperatures continues for several days
   through next weekend


WEATHER PATTERN OVERVIEW:
Model fog this morning is suggesting that fog will quickly fill
in along the Milk and Missouri River Valleys and then north of
these locations along the Hi-Line. Satellite data at this time
appears to be a much slower burn as GOES night time microphysics
suggest these areas are primed, but is showing a slower fill in
process than anticipated by the model data. CAMs and DESI data is
also suggesting that there will be some clearing from the west to
east, but that it may not make it all the way to KGGW and
certainly won`t make it KOLF keeping fog in place for most of the
day when it begin to backfill up the Milk and Missouri Rivers
tonight. Unfortunately , most Hi-Res data doesn`t go beyond 24-36
hours and currently am unaware as to how fast it will exit Tuesday
morning. This all being the case issued a Dense Fog advisory
across the Hi-Line for tonight lasting into 4PM this afternoon in
order to allow the day shift a stab at it when the newer data
flows in later today for Tonight.

A warm upper ridge will be the main weather player through early
this week making for warm temperatures (especially just off the
surface). Temperatures will remain above normal all week into the
weekend. The upper ridge flattens somewhat on Christmas Day with
another disturbance pushing through, however with this disturbance
most of the energy stays well to the south. A warm SW flow aloft
is expected Thursday and Friday.


FORECAST CONFIDENCE & DEVIATIONS:
Confidence is high for freezing fog this morning through today
over Hi-Line, but low to medium for continuing fog through
Tuesday morning. Confidence is high on above normal temps with
little to no precipitation for the next several days.

Used a "Majority Rules" CAM blend for Visibility through the next
48 hours instead of GLAMP/NBM. Sky had an NBM optimizing tool run
over it to improve baseline NBM (allow overcast and SKC) and then
Sky was raised to match Visibility in locations with fog via
another local tool to correct for poor low NBM Sky grids where
fog was expected to fill in for TAFs.

GAH


&&

.AVIATION...

LAST UPDATED: 0830Z

FLIGHT CAT RANGE: VFR - Airport Shutdown

DISCUSSION: FREEZING FOG is expected to move into the Hi-Line
impacting Malta(KM75), KGGW, KOLF, Poplar(KP01), and
Plentywood(KPWD). These locations are most likely to experience
airport shutdown over the cycle. While KSDY may only be slightly
impacted (min IFR/MVFR) and KGDV should not be touched at all and
remain VFR. Around 18Z-19Z fog and low stratus should begin
slowly clearing from west to east, but is not expected to make it
to KOLF. Fog will again return tonight to the Milk and Missouri
River Valleys though the extent of this is currently is question.

WIND: Light and variable through Noon. Becoming W to SW this
afternoon. increasing to 5 to 15 kts this evening through tonight.

LLWS: There is a chance(20-40%) for Low level wind shear this
evening from 02-06Z at KGGW and KOLF.

GAH


&&

.GGW WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 4 PM MST this afternoon for Central and
Southeast Phillips-Central and Southern Valley-Daniels-Eastern
Roosevelt-Northern Phillips-Northern Valley-Richland-Sheridan-
Western Roosevelt.


&&

$$

weather.gov/glasgow