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Area forecast discussion 
National Weather Service Billings Montana
249 PM MDT Sat may 30 2015

Short term...valid for sun and Monday...

Active weather expected through the remainder of the weekend.
Water vapor imagery showing an upper low over British Columbia.
This low will eject a few disturbances across our forecast area
this afternoon/evening and again on Sunday as it slowly moves east
across southern Canada. The first of two disturbances is moving
across north central Montana and has triggered some showers and a
couple of thunderstorms. The second disturbance is moving across
Idaho into western Montana. A few showers and an isolated
lightning strike have developed across park and Sweet Grass
counties. Expect showers and thunderstorms to increase in coverage
across the west this afternoon moving east across the Billings
area by late afternoon into the evening hours. Have adjusted probability of precipitation
to reflect likely across all but the far eastern areas through the
evening and then the far east after midnight.

Any thunderstorm this afternoon/evening could be strong with an
isolated severe storm possible as shear is better than has been
the case the past week. Precipital waters are around an inch so
heavy rain will again be likely with any thunderstorm.
However...overall dynamics and lack of a strong triggering this time...looks to prevent any widespread severe

Sunday & Monday...weak ridging builds across the forecast area
Sunday. However...a few impulses will move across the area Sunday
afternoon/evening. Shear and dynamics will be similar to today
but overall forcing combined with a lack of strong triggering
mechanism should prevent any widespread severe weather.
However...thunderstorms will have the potential to be strong with
the possibility of an isolated severe thunderstorm. A much better
chance for severe thunderstorms arrives on Monday as an upper low
and trough move onto the Pacific northwest coast bringing a
diffluent flow aloft across our forecast well as several
disturbances within the flow. Shear is best from about Billings
eastward and this is also where the highest convective available potential energy around 1000 j/kg
will be located. As a result...I added the mention of
thunderstorms having the possibility of being severe during the
afternoon and evening for all areas but the western mountains and
adjacent foothills. Hooley

Long term...valid for Tuesday...Wed...Thu...Fri...Sat...

Upper level troughiness continues to be anchored along the West
Coast through the period leaving northern rockies under southwest
flow aloft which will provide opportunities for scattered showers
and thunderstorms through much of the Tuesday through Saturday
time frame. Timing specific shortwaves at this range will be
challenging so forecast reflects a bit of a broad brush approach
with scattered probability of precipitation throughout the period.

Gradual cooling trend begins on Tuesday and continues into the
weekend...with Tuesday being the warmest day with high
temperatures near 80...then cooling into low to middle 70s the rest
of the period...very near seasonal normals.

Some differences between the models late in the period...Friday
and Saturday...with handling of cutoff low prognosticated to settle over
Southern California. Possibility that this feature could open the
door for moisture to work northward across High Plains...wrapping
back into the northern rockies. Will bear watching for late in the
week and into next weekend. Meier



Showers and thunderstorms will overspread the area from west to east
this afternoon and evening. MVFR/IFR conditions will accompany the
precipitation...with lower conditions possible. VFR conditions
will return to the area after 06z with lingering MVFR/IFR possible
from kmls east and southeast. Areas of mountain obscuration this afternoon
and evening will decrease overnight. Meier


Preliminary point temp/pops...

Sun Monday Tuesday Wednesday Thursday Friday Sat
bil 052/080 058/085 053/078 052/073 051/072 052/071 050/071
63/T 23/T 43/T 32/T 43/T 34/T 44/T
lvm 051/078 053/080 049/070 046/068 044/069 046/069 046/068
64/T 34/T 45/T 44/T 34/T 44/T 45/T
hdn 051/081 056/087 054/080 053/075 053/076 052/075 052/074
63/T 23/T 42/T 22/T 43/T 33/T 44/T
mls 050/078 057/088 059/079 055/075 054/074 054/076 053/074
61/b 23/T 62/T 32/T 44/T 44/T 55/T
4bq 050/078 055/086 057/079 054/075 054/074 054/077 054/074
32/T 22/T 42/T 32/T 44/T 34/T 44/T
bhk 044/073 051/084 058/078 053/073 051/073 050/073 052/072
61/b 13/T 62/T 33/T 44/T 44/T 55/T
shr 050/078 051/085 054/076 050/071 049/071 049/073 050/070
33/T 22/T 33/T 23/T 44/T 44/T 56/T


Byz watches/warnings/advisories...



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