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Area forecast discussion 
National Weather Service Great Falls Montana
305 PM MDT Tuesday Jul 7 2015

Discussion...

Tonight through Thursday...a cold front spread across north
central Montana Tuesday afternoon. A band of light rain organized
behind the front. Afternoon temperatures were around 5 to 10
degrees below forecast highs with the frontal passage, so lowered
evening temperatures across the north Central Plains. Isolated
thunderstorms were developing over southwest Montana where the
environment remained warmer and therefore favorable for brief
heavy rain and gusty winds near these thunderstorms. Severe storms
are not expected. Wednesday will remain dry for our County Warning Area with
stable surface high pressure in place. Thunderstorm activity
returns to southwest Montana on Thursday as a vorticity maxima
leads a stream of subtropical moisture associated with an upper
level cut off low moving inland over California. At present the
NAM model depicts subsidence and dry middle level air over the north
Central Plains where relative humidity should drop below 20
percent on Thursday afternoon. Light winds as forecast would
mitigate fire weather concerns but may need to be monitored for
changes. Nutter

Thursday night through Tuesday...monsoonal moisture ahead of an
upper low over California will have worked its way into southwest
Montana by Thursday evening and scattered showers and
thunderstorms from Thursday afternoon will linger into Thursday
night. Friday the upper low will weaken as it moves into southern
Idaho and Wyoming during the afternoon and into Montana Friday
night. Model runs differ on the details of the remnants of the
upper low and their associated precipitation patterns. Due to
these differences have decided to continue with the inherited
forecast of scattered showers and thunderstorms over southwest
Montana as well the Rocky Mountain front with shower and
thunderstorm activity expected to be isolated over the northern
plains. Saturday the European model (ecmwf) model run develops an upper ridge over
western Montana while the GFS model run has the area still being
affected by the remnants of the upper low. Even with these
differences both model runs have precipitation forecasts in line
with the inherited forecast of scattered showers and thunderstorms
mainly over the Rocky Mountain front and southwest Montana. Sunday
through Tuesday the GFS and European model (ecmwf) model runs have southwest flow
aloft with some embedded moisture. The inherited forecast was
pretty dry during this period so have increased the chances of
precipitation to at least have a mention of precipitation. Blank

&&

Aviation...
updated 1800z.
Scattered showers and isolated
thunderstorms will affect kgtf...kctb and khvr terminals this
morning and have kept vcsh through midday. A brief shower is
possible at these sites...but heavier precipitation will primarily be
along the Rocky Mountain front. These showers should diminish by
early this afternoon. Additional showers and thunderstorms are
possible this afternoon with gusty erratic winds the primary
threat. The best chance for thunderstorms will be between 22z and
03z. Overall...VFR conditions will prevail...however local MVFR
ceilings/visible are possible in heavier rain and thunderstorms. Afternoon
and evening thunderstorms will dissipate after 03z with clearing
skies after 03z. Smoke from wildfires across the Pacific northwest
and Canada will also persist above 20kft. Late tonight into early
Wednesday morning...forecast models hint at some low clouds at
khln and kbzn...however did not add fog due to low forecast
confidence but will continue to monitor. Mlv

&&

Preliminary point temps/pops...
gtf 50 81 52 88 / 30 10 0 0
ctb 47 81 47 87 / 20 0 0 0
hln 57 83 57 89 / 30 10 0 10
bzn 51 79 50 83 / 30 10 0 40
wey 42 69 42 70 / 20 50 30 50
dln 52 77 53 78 / 20 20 10 50
hvr 49 84 51 91 / 10 0 0 0
lwt 51 78 52 86 / 20 20 0 0

&&

Tfx watches/warnings/advisories...
none.
&&

$$

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