Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 270922

Area Forecast Discussion
National Weather Service Billings MT
322 AM MDT Tue Jun 27 2017

.SHORT TERM...valid for Tdy and Wed...

Active weather day expected with intensity the biggest question as
a disturbance will move through the area with the ridge axis
already moving out of Montana. Core of this disturbance over
southwest Idaho and it fills a bit as it approaches the western
zones this morning. Most of the forecast area has seen a cold
front pass through overnight though front likely to be hung up
over Carter and Fallon counties into the morning hours. Main jet
is passing south of the area so strongest lift moves across
Wyoming and that is where strongest thunderstorm activity will be
expected. Expect multiple rounds of storms today with one set
having a relatively early timing today. The early storms will be
fighting lower CAPE and initial dryness in the atmosphere but
they do help moisten the atmosphere for later storms. Models show
PWs increasing through the day so despite relatively weak shear
afternoon storms could produce small hail and gusty winds. This
lines up with marginal risk posted by SPC along the Montana
Wyoming border. Temperatures will be cooler today by 7-10 degrees
with southeast Montana still seeing a few upper 80s.

A bit of shortwave ridging overnight lowers chances for
thunderstorm activity but Wednesday sees cyclonic develop as
another wave slides southward through Alberta. Airmass is slightly
drier and the boundary layer is cooler so while instability will
support thunderstorm development expect storms to be less numerous
and not as wet. Flow becomes even more cyclonic Wednesday night
as the wave begins to swing through southern Saskatchewan which
pushes a cold front through the area. This supports nocturnal
shower and thunderstorm activity but drying behind the front will
continue the trend of storms being less wet. borsum

.LONG TERM...valid for Thu...Fri...Sat...Sun...Mon...

Didn`t make any significant changes to the going extended
forecast. Continued isolated to scattered PoPs for Thursday with
cyclonic flow over the area and vorticity moving through the flow.
Airmass dries out Thu. night and Friday for minimal PoPs. Did keep
the western PoPs on Friday as GFS continued to show vorticity
streaming through this area. The GEFS plumes for Thu. were in the
60s and 70s, and blended guidance gave highs a bit below normal
which looked good. Friday will have similar highs to Thursday.

More vorticity approaches the west on Saturday for chances of
afternoon and evening thunderstorms W of KBIL. There will be a low
chance of thunderstorms over the eastern zones Sun. afternoon as
the energy moves through this area. Sat. and Sun. will be warmer
with highs in the 80s. Upper ridging and drier air will bring dry
and warmer conditions Monday and Tuesday. Went a couple of degrees
above blended guidance to get highs around 90 based on 700 mb
temperatures around +14 degrees C. Arthur



A cold front will push E through the eastern part of the area
today. Expect a shift to gusty NNW surface winds at KBIL and KSHR
around 16Z, and at KMLS around 19Z. Outflow from thunderstorms
could bring earlier winds shifts. Scattered thunderstorms will
overspread the area from W to E through the day. Some storms will
contain gusty winds and small hail. Chances for storms will
decrease from N to S tonight. MVFR to IFR conditions will
accompany the thunderstorms. Expect at KSHR until mid-morning.



    Tdy Wed     Thu     Fri     Sat     Sun     Mon
BIL 081 056/078 055/075 052/077 053/082 057/086 061/091
    5/T 42/T    23/T    11/B    11/U    11/U    00/U
LVM 074 049/074 046/072 043/076 045/080 049/083 051/087
    5/T 33/T    33/T    11/B    12/T    21/U    11/U
HDN 083 054/082 053/076 051/079 052/084 056/089 060/093
    5/T 43/T    32/T    11/B    11/U    11/U    00/U
MLS 084 053/083 055/078 049/077 050/083 057/088 063/093
    3/T 32/T    32/T    11/B    11/U    11/B    10/U
4BQ 085 053/081 054/076 050/077 050/082 056/086 061/091
    3/T 43/T    43/T    11/B    11/U    12/T    10/U
BHK 087 051/081 053/075 047/072 046/079 052/083 058/088
    2/T 31/U    23/T    21/B    11/U    12/T    10/U
SHR 079 053/076 050/072 047/075 048/080 053/083 055/089
    4/T 54/T    43/T    12/T    11/U    11/B    11/U




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