912
FXUS65 KBYZ 131901
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
101 PM MDT Mon May 13 2024

.DISCUSSION...
Through Tuesday Night...

Satellite imagery shows a distinct shortwave moving thru ID and
western MT in a zonal flow aloft. There is a trailing wave along
the BC coast that is pushing to the southeast in a developing NW
flow aloft behind the initial trof. Both of these features will
keep our weather active from this afternoon through Tuesday.
Surface analysis shows 200-500 j/kg of MLCape at 18z but with CIN.
As you`d expect, weak convection developing over the high terrain
is diminishing as it tracks off the foothills. This will no doubt
change as synoptic scale forcing increases in our west between now
and 00z.

Convection today and tomorrow will be non-severe, based on
limited instability and poor shear, but it may produce small hail
and localized erratic wind gusts (especially today w/ warmer
temps and steep low level lapse rates). Though storms won`t be
severe, the very changeable weather should be watched if you have
outdoor plans.

Still expecting multiple rounds of showers and embedded t-storms
thru tonight, as upstream wave won`t reach the Dakotas border
until ~12z early Tuesday. After what will be a very brief lull,
ascent arrives from the NW tomorrow morning. The forcing and low
convective temps will result in an early onset of showers on
Tuesday (between 15-18z). Greatest coverage and heaviest precip
tomorrow will be in southern upslope areas per the NW flow.

Freezing levels fall tonight behind a Pacific cold front. Snow
levels in the high country should fall to about 9000ft elevation,
which will continue through Tuesday and may fall to near 8000ft
Tuesday night (as precip tapers off late).

After temps in the 70s to lower 80s today, we will see highs in
the 60s to lower 70s on Tuesday, with mixed/breezy northerly winds
gusting 20-30 mph.

A couple of precipitation probabilities for the next 36 hours:
0.50" of precip:  60-80% mtns, 50% fthls, 20-35% lower elevations
3+" of snow above 9000ft:  50%

JKL

Wednesday through Monday...

For Wednesday, as the shortwave exits the region, a weak wave of
energy will push through to provide weak forcing mainly over the
mountains. The highest peaks (above 9000 ft) could pick up a few
inches of snow, with less than a tench of an inch of rain likely
for lower elevations. NW flow will build in for Thursday while a
shortwave focused over northern MT dips SE to provide a chance of
precip for the eastern half of MT. Ensembles are differing on just
how far south that energy will go. For now, the NBM has PoPs of
around 20-30% for Thursday afternoon. This uncertainty with the
pattern continues into Friday, but with consensus on NW flow
continuing, PoPs are forecasted to be in the 20s for Friday.
Ensembles and clusters are in decent agreement that larger scale
troughing will move in for the weekend with continued chances for
precipitation and slightly cooler temperatures. High temperatures
will be in the 60s Wednesday, warming to the 70s by Thursday,
then cooling into the 60s for the weekend and Monday. TS

&&

.AVIATION...

Expect occasional showers and some embedded non-severe
thunderstorms late this afternoon through Tuesday as a couple of
disturbances and Pacific cold front move through the region. VFR
will prevail, but any heavier showers have the potential to
produce brief MVFR-IFR, small hail and erratic wind gusts to
~30kts. Mountains will be obscured at times tonight and tomorrow
as snow levels fall to near 9000ft agl.

TS potential timing through tonight at our TAF sites:
BIL:  21-06Z
LVM:  20-05Z
MLS:  21-08Z
SHR:  19-06Z

JKL

&&

.PRELIMINARY POINT TEMP/POPS...

    Tue     Wed     Thu     Fri     Sat     Sun     Mon
-----------------------------------------------------------
BIL 051/066 047/069 050/076 051/078 049/063 043/065 043/070
    58/T    54/T    22/W    22/T    34/W    33/W    23/W
LVM 045/064 043/068 046/076 050/078 044/064 039/064 040/068
    68/T    53/W    12/W    12/W    24/T    34/T    23/W
HDN 051/068 045/069 047/076 047/079 048/063 042/067 042/071
    78/T    44/W    22/W    32/W    33/W    33/W    23/W
MLS 053/070 046/069 049/073 049/075 048/063 043/065 043/071
    54/T    22/W    32/W    32/W    32/W    23/W    22/W
4BQ 052/068 046/067 047/073 049/076 048/064 043/066 043/069
    67/T    32/W    21/B    21/U    32/W    33/W    22/W
BHK 049/070 042/067 044/071 046/075 044/064 039/063 038/068
    55/T    22/W    22/W    22/W    32/W    23/W    22/W
SHR 047/065 042/065 043/073 047/079 045/064 040/064 038/069
    79/T    65/T    22/T    22/W    23/W    43/T    33/W

&&

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

&&

$$
weather.gov/billings