Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 280903

Area Forecast Discussion
National Weather Service Billings MT
303 AM MDT Wed Jun 28 2017

.SHORT TERM...valid for Tdy and Thu...

Upper level low pressure over Saskatchewan and Alberta today digs
into northeast Montana on Thursday. This brings colder air aloft
to the region with moderate flow aloft but the boundary layer will
be cooler. Stage will be set for additional thunderstorms and
upper level forcing looks stronger so higher confidence in seeing
storms. Convective indices are lower so think severe weather is
less likely but with cold air aloft and relatively quick storm
movement small hail and strong wind gusts are again a possibility.
Do think storm initiation today will be driven in two areas.
Southeast Montana will see a push of isentropic lift move across
this afternoon which will help trigger storms but lapse rates are
not as steep in these areas. A sector of jet divergence will move
over western areas later this afternoon and this will yield the
stronger storms and 700mb flow becoming northwesterly will add an
upslope component over the mountains. Expect the upslope to allow
activity to fill in late after and evening hours so likely pops
over the mountains look good. Will be a cooler day with highs in
the mid to upper 70s.

Tonight a cold front moves through the area and initial drying
should curtail shower activity expect for upslope areas but
surface low pressure moving across the northern part of the state
pulls moisture around itself and remoistens the airmass over
southern Montana on the backside. Presence of this moisture and
cyclonic flow aloft behind the exiting upper low moving into North
Dakota support additional shower and thunderstorm activity but
weaker CAPE and higher shear limits the potential for strong
updrafts and do not expect a lot of moisture from the storms.
Thursday will be the coolest day of the week with highs in the
lower to mid 70s. borsum

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

No major changes to the extended forecast with models in decent
agreement with overall pattern. Did dry out Friday as the jet is
shifting E out of the area during the day and the airmass was dry.
Temperatures will be seasonable in the 70s. Brief upper ridging on
Fri. night into Sat. gives way to a shortwave moving E through the
region Sat. night through Sun. evening. Kept some PoPs W and S of
KBIL ahead of the approaching wave Sat. afternoon and spread them
a bit further E Sat. evening. Went mainly dry late Sat. night
through Sun. morning, then kept PoPs E of KBIL Sun. afternoon and
evening as the wave departs the area. Airmass moderates for the
weekend, bringing temperatures in the 80s. Will have a dry WSW
flow over the area Monday through Tuesday with 700 mb temperatures
climbing to around +14 degrees C. Went above guidance with high
temperatures, which should reach the lower to mid 90s in many
areas. A shortwave passes N of the forecast area on Wed. which
will suppress the warmer air S a bit for a slightly cooler day.
Otherwise the dry airmass continues over the region. Arthur



Isolated to scattered showers and a few thunderstorms will move
across the area this morning. Conditions will remain VFR with
areas of mountain obscuration. Thunderstorms will become more
widespread this afternoon, especially from KLVM to KBIL S. Expect
MVFR/IFR conditions in thunderstorms. Scattered thunderstorms will
gradually decrease from N to S tonight. There will be areas of
mountain obscuration tonight. Surface winds will shift to the NNW
mainly after 06Z tonight behind a cold front. Arthur



    Tdy Thu     Fri     Sat     Sun     Mon     Tue
BIL 078 055/074 051/079 054/084 058/087 059/092 061/092
    5/T 32/T    11/B    11/U    21/B    00/U    00/U
LVM 072 046/071 043/078 046/082 049/084 051/089 052/089
    5/T 32/T    11/B    12/T    21/U    00/U    11/U
HDN 081 056/075 048/080 053/086 057/089 058/095 059/095
    5/T 33/T    11/B    11/U    21/B    00/U    00/U
MLS 080 056/075 049/077 052/084 059/089 061/094 063/095
    3/T 42/W    21/U    11/U    21/B    00/U    00/U
4BQ 077 055/074 049/076 051/083 056/087 059/091 061/094
    3/T 52/T    21/U    11/U    12/T    10/U    00/U
BHK 077 056/073 047/072 046/079 053/085 057/089 060/091
    2/T 22/W    21/B    11/U    12/T    20/U    00/U
SHR 074 051/069 045/074 048/081 053/084 053/088 055/090
    6/T 44/T    21/B    12/T    12/T    00/U    00/U




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