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Area forecast discussion...updated 
National Weather Service Billings Montana
854 am MDT Wednesday Sep 17 2014


Updated forecast to add slight chance of showers this morning as
a weak disturbance interacts with good middle level moisture and
instability. Looks like this activity will dissipate over the next
few hours as disturbance shifts east of the area. Another
disturbance will arrive late this afternoon bringing a few
thunderstorms to western zones...drifting across the area tonight
as the disturbance propagates through the area. Overall a nice
late Summer day across the region with highs in the middle to upper
80s and partly cloudy skies. Cold front still on track for late
Thursday arrival with a better chance for showers and
thunderstorms Thursday afternoon through early Friday. Chambers


Short term...valid for today and Thursday...

Thermal ridge axis shifts over the forecast area today...and will
easily bring the warmest temperatures of the week. For
today...forecast 850 and 700 mb temperature anomalies are running
about +2 Standard deviations above normal for this time of year.
This translates to high temperatures reaching the upper 80s to
around 90 based on climatology of +2sd days. Given that we
over achieved on temperatures yesterday even with some cloud
cover around...have no problem raising forecast high temperatures
for today. One exception will be far eastern Montana where low-
level southeasterly will keep the inversion in place.

Thursday will be another very warm day across the area...with
locations from Miles City to Baker experiencing their warmest day
this week as low- level southeasterly flow finally gets shunted
off into the Dakotas as a weak surface trough passes. Slightly
cooler air will trickle into the central and western zones...but
the main cold front still lags well back into western
Montana...and will likely not make its push across the area until
late Thursday night/Friday morning.

Mainly dry conditions are expected again today...with the
exception being some isolated showers/thunderstorms in the
mountains with increasing middle-level moisture. By Thursday night
into Friday...approaching Pacific trough will pull monsoonal
moisture into northern Wyoming and southern Montana. This will
result in our best chance of precipitation across the area. The
main problem remains the splitting nature of the Pacific trough
leaves US with little dynamic forcing to work with. Despite the
weak forcing...precipitable water values will be abnormally high for this time of
year...approaching 1 inch...and should be sufficient to spark some
scattered showers and thunderstorms with the trough/frontal
passage. These showers/thunderstorms could produce localized heavy
rainfall...but any organized large scale rain event is not


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

Medium range guidance in good agreement. Upper trough will push
through the area on Friday before shifting east with a dry
northwest flow taking over beginning Friday night. Have maintained
precipitation chances during the day on Friday...but did return to a dry
forecast for Friday night behind the trough. Weekend will remain dry
as upper ridge builds in. Some uncertainties develop into next
week as upper low spinning off the California coast drifts under this
ridge into the Great Basin Sunday...advertised to lift into
Wyoming for late Monday into Tuesday. Always plenty of uncertaintywith
tracks of these systems cut off from main flow. Current models are
consistent with potential convection into Wyoming Monday night into
Tuesday...possibly having a minor affect on our mountains. Have
introduced isolated storms into the forecast for this period for
the mountains. Things look to dry out then again by Wednesday.



VFR conditions will prevail into this evening with mainly scattered-broken
middle and high level cloudiness. Although...there will be isolated
showers and storms in and near the mountains. Frieders


Preliminary point temp/pops...

Today Thursday Friday Sat sun Monday Tuesday
bil 089 059/084 057/078 050/074 048/076 047/078 052/077
2/west 12/T 33/T 10/u 00/u 00/u 00/u
lvm 090 053/083 050/076 041/075 042/077 042/078 045/079
2/T 13/T 33/T 10/u 00/u 01/u 11/u
hdn 093 054/087 055/080 049/076 047/078 046/079 048/078
2/west 11/b 33/T 10/u 00/u 00/u 00/u
mls 088 056/089 058/080 050/075 046/076 047/078 048/078
2/west 01/b 23/T 10/u 00/u 00/u 00/u
4bq 090 055/091 058/079 050/074 046/076 046/078 047/078
1/b 11/b 23/T 10/u 00/u 00/u 00/u
bhk 083 052/088 056/078 049/074 043/073 044/076 045/075
2/west 01/b 23/T 10/u 00/u 00/u 00/u
shr 088 053/089 054/077 046/073 043/075 041/078 043/078
2/west 12/T 24/T 20/u 00/u 00/u 00/u


Byz watches/warnings/advisories...



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