Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 211629

Area Forecast Discussion...Updated
National Weather Service Billings MT
1029 AM MDT Sun May 21 2017

Northerly flow sharpening over Montana and this will send a
series of weak waves across the area through the day. Mainly
looking at isolated to scattered coverage of showers today, with
more coverage over the east. Winds were slightly stronger aloft
today, so showers should be a bit longer living compared to
yesterday, but with weak shear, convection should remain on the
weak side. Updated PoPs and sky grids a bit to match current radar
trends and latest short range high resolution guidance. TWH


.SHORT TERM...valid for Tdy and Mon...

Bands of light rain are ongoing from Bighorn County northward
into Treasure and Rosebud counties ahead of a surface front
pushing through the area from west ot east. Some mountain snow
showers which are still lingering over the Absarokas should come
to an end by morning. Front transitions east by the afternoon with
some light showers and isolated thunderstorms continuing over the
eastern zones. CAPE around 500 j/kg and shear of only 20 kts or
so will yield mainly pulse storms capable of producing brief wind
gusts above 40 mph and pea size hail over the Plains. Winds will
generally be breezier than they were yesterday afternoon with
gusts 20 to 30 mph out of the northwest.

Next frontal system arrives tonight which will push showers in
from the northeast. Rain will spread from north to south through
the area during the night and into Monday morning. Rain will
slowly push out Monday afternoon, with a tenth to over a quarter
inch of qpf expected across most of the area. Northwestern zones
around Wheatland and Golden Valley counties don`t look nearly as
wet with maybe a few hundredths possible through Monday.
Temperatures expected to stay near normal for the next few days
with Highs in the upper 60s to low 70s and Lows in the upper 30s
to low 40s. Walsh

.LONG TERM...valid for Tue...Wed...Thu...Fri...Sat...

Models have not changed much from the previous forecast so little
changes were made with this issuance. High pressure builds over
the forecast area Tuesday bringing dry weather. The upper low
that is currently over the central Plains will move into the Great
Lakes area while another upper low with strong vorticity will
move eastward across southwest Canada. Upper trough associated
with the low should push eastward toward our region late
Wednesday, so have added a slight chance of showers and
thunderstorms to the forecast Wednesday afternoon into the
evening. This pattern will result in high temperatures in the 70s
Tuesday and around 80 degrees Wednesday.

The upper low and trough then generally stall over the Pacific
Northwest and southern Canada in slow background flow for the
late week period. Disturbances embedded in the cyclonic flow in
this pattern should produce periods of showers Thursday through
Saturday. Thunderstorms are also possible during the afternoon
and evening hours. The air should be cool under this trough with
high temperatures generally in the 60s. RMS/Walsh



Partly sunny skies with VFR conditions will prevail throughout
the day. Scattered showers along with some isolated thunderstorms
will be possible once again. MVFR conditions will be possible
with any shower/thunderstorm. Widespread heavy activity is not
expected. The mountains will be obscured at times. Hooley



    Tdy Mon     Tue     Wed     Thu     Fri     Sat
BIL 069 049/067 045/073 051/082 048/066 045/064 044/066
    2/T 56/T    10/B    02/T    33/T    32/T    23/T
LVM 065 041/066 039/074 046/077 040/063 038/061 037/064
    2/T 35/T    10/B    02/T    34/T    44/T    43/T
HDN 069 049/068 042/073 047/084 047/069 044/067 043/068
    2/T 56/T    10/B    02/T    23/T    32/T    23/T
MLS 070 047/066 043/071 049/080 050/070 046/068 046/069
    2/T 45/T    10/U    02/T    22/T    22/T    23/T
4BQ 067 047/063 040/068 045/079 047/070 045/066 043/067
    3/T 56/T    20/U    02/T    22/T    23/T    33/T
BHK 066 043/061 038/065 042/074 046/067 043/065 041/066
    3/T 56/T    20/U    02/T    22/T    22/T    23/T
SHR 063 045/061 037/067 043/080 044/066 041/063 040/063
    3/T 36/T    20/U    02/T    24/T    43/T    33/T




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