Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 192111

Area Forecast Discussion
National Weather Service Billings MT
311 PM MDT THU MAY 19 2016

.SHORT TERM...valid for Fri and Sat...

Upper diffluence has moved into western zones this afternoon and
has generated some showers and thunderstorms. Capes have risen to
around 1000j/kg over the forecast area. Effective bulk shear was
weak at this time, less than 35kts. The strongest shear was just
west of Livingston and moving east. Shear spreads east this
evening as shortwave energy rotates around a deepening upper
trough over Washington/Oregon. Kept high pops west of Billings
with scattered pops over central zones. Storms could be strong
this afternoon and evening west of Billings with high capes but
with limited shear and ascent from a weak wave, am not expecting
much severe weather. A near severe storm is more likely than a
severe one at this time.

Heights fall Saturday as the upper trough moves east with the
northern part of the trough cutting off an upper low and shifting
it into northwest Montana. Surface low pressure forms over the
forecast area with continued strong south to southeast inflow into
southeast Montana. Will continue to see very warm temperatures
over the southeast with 850mb temperatures rising to around 26c.
Western and central zones will be cooler, but should warm to
levels near, if not warmer, than Friday with a low level westerly
wind. The main threat of showers and thunderstorms will be over
the southeast with capes near 1500j/kg near the border. Storms may
end up developing just over the eastern portions of Fallon and
Carter counties, and then shift into the Dakotas. Will linger low
pops over central and western zones with height falls and surface
convergence around the low. TWH

.LONG TERM...valid for Sun...Mon...Tue...Wed...Thu...

Extended period looked a little drier early next week so have
lowered pops a bit...otherwise unsettled weather with showers and
thunderstorms will be the theme for the forecast.

Models were in good agreement in bringing an upper low east along
the MT/Canadian border on Sunday. Some jet divergence will
accompany the system due to the jet moving around the eastern side
of the low. Area will be under westerly flow as a weak cold front
moves through the region. The best precipitation chances will be
over and near the mountains. Model B+ supported thunder across the
area. Went a bit above Superblend guidance for high temperatures
based on expected mixing and westerly flow. Highs will range from
the lower 60s west to the mid 70s east. Another cold front will
sink south into the area Sunday night keeping just a slight chance
of showers over the area.

The departing low to the north of the area will leave cyclonic
flow with shortwave energy in it/s wake on Monday. Kept scattered
showers over most of the region with a slight chance of
thunderstorms. Energy continues to move across the area Tuesday
and Wed. with low chances of showers and thunderstorms. A split
trough will keep showers and thunderstorms in the forecast for
Thursday. Temperatures will be near normal Mon. and Tuesday, then
will warm into the 70s for the rest of the period. Arthur



Showers and thunderstorms will increase over the area, mainly
west of KBIL late this afternoon. Thunderstorms will contain
surface wind gusts to around 40 kt. The precipitation will
continue to spread east this evening, affecting KBIL by 00Z.
MVFR/IFR conditions will accompany the thunderstorms. Scattered
showers will continue overnight through Fri. morning from KBIL
west. Showers and thunderstorms will increase west of KBIL again
Fri. afternoon, with MVFR/IFR or lower conditions.
Elsewhere, expect isolated to scattered showers and storms. Expect
widespread mountain obscurations over the Beartooths, Absarokas
and Crazy mountains with areas of obscuration over the NE
Bighorns through the period. Arthur



    Fri     Sat     Sun     Mon     Tue     Wed     Thu
BIL 051/074 052/077 048/069 045/067 045/068 046/071 049/073
    54/T    53/T    33/T    24/T    42/T    22/T    22/T
LVM 043/066 043/066 040/061 038/060 038/062 038/066 040/070
    66/T    64/T    35/T    34/T    43/T    33/T    33/T
HDN 048/080 050/082 047/073 042/069 042/070 044/073 046/076
    32/T    33/T    33/T    23/T    32/T    22/T    22/T
MLS 054/084 058/087 053/075 047/070 045/070 047/074 050/077
    22/T    22/T    32/T    22/T    22/T    22/T    22/T
4BQ 049/085 054/086 051/076 044/070 043/070 044/073 047/075
    12/T    22/T    33/T    22/T    22/T    22/T    22/T
BHK 049/079 053/082 051/075 043/069 042/069 043/070 045/073
    02/T    22/T    44/T    32/T    22/T    22/T    33/T
SHR 045/081 048/079 044/068 040/065 040/067 041/069 043/071
    22/T    22/T    33/T    33/T    33/T    33/T    33/T




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