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Area forecast discussion...updated 
National Weather Service Billings Montana
815 PM MDT Tuesday Apr 21 2015


Weak...isolated and diurnally-driven showers around the mountains
are dissipating quickly with sunset and that will leave US with a
quiet and uneventfull night. All we did for this update was drop
lows a few degrees in spots using recent MOS guidance and out of
respect to relatively dry air even with easterly low-level flow.


Short term...valid for Wednesday and Thursday...

The forecast becomes a little more unsettled the next couple of
days as the area loses northwest flow aloft. The flow aloft backs
and weakens tonight and Wednesday as a small scale ridge slides
into the forecast area. Some weak energy and moisture slides
underneath the ridge and combines with a bit of instability for a
few showers Wednesday afternoon and evening over the west. Enough
instability present for isolated thunderstorms. The upper trough
works across the forecast area for Thursday and will spread
scattered probability of precipitation into central and eastern zones. Temperatures will
be warmer despite low level easterly flow as 850mb temperatures
rise to around 18c. Twh

Long term...valid for Friday...Sat...sun...Mon...Tue...

No big changes to the going forecast this afternoon. Transitioning
into a more active pattern by late in the week with a strong
Pacific jet orienting itself to bring Pacific moisture across the
area this weekend. Flow is fast though which will prevent any
strong storm systems from developing thus while there will be a
series of weak systems moving through precipitation chances will
be held in check. Currently looking at broadbrush 20 to 40 probability of precipitation
across the area Friday into Monday. With the predominant pattern
being off the Pacific...some downslope influence will persist
across the area through the extended resulting in above normal
temperatures into next week. Chambers



VFR conditions and light winds are expected tonight and Wednesday
morning. The same will be true in most areas Wednesday afternoon.
However...a few showers and possibly a thunderstorm may develop
over western parts of south central Montana around klvm by late in the
day Wednesday. Schultz


Preliminary point temp/pops...

Wednesday Thursday Friday Sat sun Monday Tuesday
bil 040/073 045/071 045/068 042/065 042/068 043/072 044/069
00/u 02/T 33/west 33/west 32/west 21/b 12/west
lvm 034/074 039/069 039/068 039/063 036/066 039/070 039/068
02/T 23/T 33/west 44/west 32/west 22/west 22/west
hdn 036/075 039/075 039/070 036/067 038/070 038/074 035/072
00/b 02/T 33/west 24/west 32/west 11/b 12/west
mls 033/070 038/070 038/070 039/068 039/070 040/072 039/073
00/u 01/b 32/west 24/west 32/west 11/b 12/west
4bq 032/070 037/071 037/069 039/068 039/068 039/072 037/074
00/b 02/T 33/west 35/west 52/west 11/b 12/west
bhk 026/064 032/065 036/066 034/065 036/066 036/069 033/071
00/u 01/b 32/west 33/west 42/west 11/b 12/west
shr 033/070 039/070 039/065 038/064 038/066 038/070 038/070
00/b 13/T 35/west 34/west 32/west 21/b 12/west


Byz watches/warnings/advisories...



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