788
FXUS65 KBYZ 090842
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
242 AM MDT Sun Jun 9 2024

.DISCUSSION...
Today through Monday Night...

Satellite imagery indicated weak NW flow over our region with a
building ridge over the intermountain west. Weak perturbations
were evident under the building ridge and were producing some weak
showers and isolated thunder across northern Wyoming in the early
morning hours. Some of these little perturbations within the
building ridge will traverse into our east this morning into the
early afternoon. A few CAM`s indicate this may produce some
convection over our eastern border counties during this time.
Nothing to strong...but some isolated showers and maybe local
thunder is possible.

Our focus then turns to the west this afternoon. As the winds
aloft back to the SW with an approaching trough, we will have
some energy move into our mountains with an increasing chance of
showers/thunderstorms. CAPE and shear is modest in our west, but
may be capable of producing some locally strong winds and small
hail. In the meantime, surface winds out of the east will advect
high PWAT values across our eastern sections by late afternoon.
Ensembles are currently showing PWAT values of greater than 1 inch
across the region with values exceeding 1.25 inches for some
locations by this evening. Rosebud County and east will also get
a good low level jet developing this evening and through the night
increasing bulk shear values.

So a weak perturbation ejecting over our region ahead of the main
trough today and this evening, will have some decent ingredients
to work. Thus there is a chance of some strong thunderstorms
capable of strong winds and perhaps an isolated marginally severe
hailstorm. The best ingredients and forcing are in sync from NE
Yellowstone/Treasure Counties to NE WY early this evening (5-9pm)
where shear and MUCAPE up to 1000 J/kg co-exist. Heavy rainfall
is also possible with PWATS so high, even though the forcing is
not all that great. We anticipate lingering showers and some
thunderstorms after midnight across the CWA as the upper trough
moves into Montana. This will produce better forcing, but
instability will be limited of course in the overnight hours.

The actual trough axis moves across our CWA Monday morning with
low level winds shifting to the west behind it. This will push
most of the higher dewpoints to the east by max heating in the
late afternoon. Thus, while there is a chance of some deeper
convection (strong thunderstorms) developing in our far eastern
sections Monday afternoon, models indicate the best ingredients
will likely coincide with max heating to our east in the Dakotas.
Thus, the risk of severe storms is highest in the Dakotas. Look
for a decreasing chance of showers/thunder Monday afternoon with
breezy NW winds. Things totally dry out by Monday evening with
decreasing wind.

Based on the aforementioned favorable ingredients for strong
thunderstorms, the Storm Prediction Center currently has the
region in a general to marginal severe thunderstorm risk later
today through the evening.

Hydro concerns...Locations in the higher terrain have a 60-70%
chance of getting 0.25 inches. With snowpack above 8,500 ft
possibly receiving 0.25-0.5 or more of rainfall, a rain on snow
scenario could lead to rapid rises along streams and rivers. We
continue to have a flood watch out for the Clarks Fork near Edgar
and Belfry where river levels may approach flood stage early
Monday if heavy rain falls within the basin. However, due to the
fluctuating and uncertain nature of convective precipitation all
folks living and recreating near water ways in the mountains and
foothills should use caution and be alert for heavy rainfall in
the area. BT

Tuesday through Sunday...

SREF and Clusters agreed that upper ridging would move into the
forecast area on Tuesday and zonal flow would overtake the area on
Wednesday. Had some 20-30% PoPs for showers and thunderstorms Tue.
night due to a cold frontal passage. Highs will be in the 80s both
days. Will have RH`s in the teens across the northern tier of the
forecast area on Wednesday with some gusty winds in the W. Fosberg
index was in the 50s in the W. Will keep an eye on Wed. for any
fire weather concerns.

Clusters showed zonal flow or weak ridging for Thursday. It will
be dry with slightly lower temperatures. PoPs increase from W to E
across the area late Friday through Friday night for showers and
thunderstorms. PoPs were generally in the 30s. Will have plenty of
moisture, as PWAT`s climb to 0.75 to 1 inch. Clusters were in
general agreement with SW flow moving into the region through
Saturday ahead of a Pacific trough. Saturday had low (20s) PoPs.
On Sunday, most Clusters had continued SW flow. There were some
20% PoPs mainly in the W in the afternoon. Temps will be in the
80s on Fri., then there will be a cooling trend for the weekend.

Probabilities were quite low for .25 inches of precipitation
through the period. Arthur

&&

.AVIATION...

There will be a slight chance for showers and thunderstorms from
KMLS E and SE this morning. Cannot rule out a morning shower in
the KSHR area as well. MVFR/IFR and possibly lower conditions will
occur with the precipitation. Low chances for showers and storms
continue E and S of KBIL this afternoon, while shower and
thunderstorm chances increase from the SW mountains (60%) to KBIL
(15%). Expect gusty E surface winds in KLVM today. Showers and
thunderstorms will become more numerous across the area this
evening. MVFR/IFR and likely lower conditions will occur with the
precipitation this afternoon and evening. A gusty wind shift to
the N is possible in KSHR around 00Z. Arthur

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Mon     Tue     Wed     Thu     Fri     Sat
-------------------------------------------------------
BIL 078 058/081 055/085 058/085 053/081 054/085 060/083
    2/T 54/T    00/U    10/U    00/U    11/U    22/T
LVM 074 053/077 047/083 051/082 047/081 049/083 052/080
    3/T 75/T    00/U    11/N    00/U    12/T    22/T
HDN 082 058/082 053/086 057/085 054/082 053/089 058/083
    1/B 53/T    10/U    20/U    10/U    11/U    32/T
MLS 078 060/080 052/083 058/083 053/081 052/085 060/083
    2/W 74/T    10/U    30/U    10/U    11/U    42/W
4BQ 080 062/080 054/084 059/084 056/081 053/087 061/083
    2/T 33/T    10/U    20/U    10/U    11/U    32/W
BHK 075 056/078 050/081 054/081 050/079 048/081 055/081
    3/W 46/T    10/U    20/U    10/U    11/U    43/T
SHR 081 055/078 051/083 054/085 052/081 051/087 056/081
    3/T 43/T    10/U    10/U    10/U    11/U    32/T

&&

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

&&

$$
weather.gov/billings