194
FXUS65 KBYZ 091621
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
1021 AM MDT Thu May 9 2024

.UPDATE...
Upslope snow showers have recently become much more scattered
along the northeast slopes of the Beartooth-Absaroka and Crazy
Mountains, so have canceled the Winter Storm Warning for these
areas. However, occasional snow showers (some heavy w/ a little
accumulation) will continue in upslope areas this afternoon and
into the evening.

Otherwise, there remains enough low-mid level moisture and
instability for more rain showers across our lower elevations
today. Scattered activity exists now (including at Billings) but
this will become more numerous in the afternoon with just a
little surface heating. Convective temps are quite low. Temps
today should warm to the mid 50s to mid 60s (warmest NE per driest
air). High res models not suggesting fog tonight, and the light
downslope winds work against fog potential, but boundary layer
moisture seems to be too high to avoid at least localized fog late
tonight. Something to watch.

JKL

&&

.DISCUSSION...
Today through Friday Night...

Satellite imagery showed deep northeasterly flow over our region
rotating around a large upper low over the NE/SD border extending
SW into Utah. Currently some drier air had infiltrated over our
eastern zones and fog was developing due to the rich moisture in
the lower boundary layer. Scattered to numerous showers continued
over our western zones flowing into our mountains.

Our current precipitation is being driven by warm air advection
circulating around the weather system, and aided by associated jet
dynamics and of course deep upslope flow. This is all creating
strong moisture convergence from Yellowstone County southwestward
into the Beartooths.

Models indicate a continued stream of moisture and lift into our
western zones today...and as instability picks up this afternoon
we will see shower coverage increase again over our eastern zones
as well. PoPs generally range from 100% over our north facing
slopes to 20% in Fallon County. The main focus of precip will
almost certainly be in areas from Billings south and southwest.
Cross sections do indicate omega weakens and moisture becomes
more shallow this afternoon. Thus, intensity of snowfall and other
precip should continue, but be decreasing later today (high Pop
and lower QPF scenario).

Tonight...upper support for ascent will continue to weaken from
north to south with precip coverage decreasing in similar
fashion...and lingering over just our mountains by late tonight.
Clouds will be decreasing as well and with plenty of low level
moisture in the boundary layer, we expect to see areas of fog
develop by Friday morning.

After any fog burns off Friday...high pressure aloft will prevail
leading to a pleasant spring day with highs warming into the 60s
for most locations.

Snowfall...Our winter storm warnings are valid through noon
today. There is still several more inches possible through the
rest of tonight and this morning. (prob of >6 additional inches
up to 65%), but the snowfal rates and intensity should be notably
lower by afternoon.

Hydro Issues...Despite the relatively prolific widespread
precipitation we have received...rivers are behaving themselves.
The rise on the Tongue at Miles City is now down to 5 ft after
peaking at 7.35 ft (flood stage 10 ft) and others are trending
down as well. BT

Saturday through Thursday...

High pressure building into the region will bring warmer and
mainly dry conditions for the weekend, with highs in the 70s
through Monday. Confidence is high for above normal temperatures,
with a greater than 70% chance of exceeding 70 degrees Saturday
through Monday. Weak energy causing the ridge to flatten some on
Sunday will bring low chances (15-30%) for afternoon showers. A
shortwave dropping into the area from the northwest is progged for
the second half of Monday, continuing through Tuesday. Showers
and thunderstorms are possible (currently 30-50% chance), greatest
near the foothills. Cyclonic flow will keep the potential for
showers/thunderstorms through the middle of the week, along with
cooler temperatures.

The upcoming warmer temps will melt much of the wet snow that is
currently falling at elevations between 6000-8000 feet. At this
time we do not see a flood risk, but rivers/streams emerging from
the foothills will likely see some rises this weekend. STP

&&

.AVIATION...

Occasional showers and mountain snowfall will continue to affect
the area today, w/ the greatest shower coverage west of KMLS and
near the mountains and foothills. Showers will decrease this
evening. MVFR to IFR can be expected with the showers (poorest
flying conditions along the foothills). Mountains will remain
obscured due to snow, especially the northeast aspects. Drying
will finally arrive late tonight into Friday, but localized
visibility reductions due to fog are possible.  JKL

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Fri     Sat     Sun     Mon     Tue     Wed
-------------------------------------------------------
BIL 059 041/066 044/075 048/077 051/078 050/069 046/069
    6/W 40/U    00/U    12/T    12/T    35/T    34/T
LVM 053 036/064 038/071 044/074 046/074 045/069 042/067
    6/W 20/U    00/U    01/U    12/W    25/T    33/T
HDN 061 040/067 039/076 045/078 048/078 048/070 044/069
    6/W 50/U    00/U    12/T    13/T    45/T    34/T
MLS 064 042/068 042/075 047/076 050/078 050/069 043/069
    3/W 20/U    00/U    12/T    12/T    34/W    22/T
4BQ 061 043/066 041/075 047/076 049/077 048/069 043/068
    5/W 30/U    00/U    01/U    12/T    44/T    22/T
BHK 064 038/067 041/074 045/076 047/077 046/067 040/066
    2/W 10/U    00/U    02/T    13/T    34/W    22/W
SHR 056 039/065 036/072 042/074 045/075 045/067 042/066
    6/W 61/B    00/U    02/T    13/T    56/T    44/T

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.

&&

$$
weather.gov/billings