Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 161511 AAA

Area Forecast Discussion...UPDATED
National Weather Service Glasgow MT
911 AM MDT Wed Aug 16 2017

.SHORT TERM...for northeast through Fri...

Satellite imagery this morning shows low stratus/fog over the
Richland County river valleys. KSDY reports fog. This should all
lift within about an hour or so. Otherwise, with the departing
upper trough, skies are clear, except for thin smoke from the BC
wild fires. With stable conditions expected today, wx/pop grids
are clear. Therefore, grid adjustments were minor, based on near
term guidance.


Previous discussion -
Shortwave ridge will be over Montana today in nearly zonal flow
aloft with a surface high over Eastern Montana. This will allow
for dry and warmer weather over the forecast area. Patchy fog is
possible early this morning near the North Dakota border where RH
will be near 100 percent around sunrise.

Dry weather will continue tonight with the shortwave ridge
remaining over the forecast area.

Surface low develops over Central Montana tonight while shortwave
trough moves inland from the Pacific across British Columbia. The
wave will enter Western Montana early Thursday morning. The
surface low will move through Eastern Montana around midday on
Thursday with a cold front. The shortwave trough follows Thursday
afternoon. With little or no moisture expected, it looks like it
will be a dry cold front. Temperatures will be in the 80s with RH
between 15 and 25 percent Thursday afternoon. NW winds behind the
cold front may be high enough to create critical fire weather
conditions. See fire weather discussion for more details.

The wave moves to the east Thursday Night and an upper ridge
builds into the area on Friday. Look for dry and warm weather.

.LONG TERM...Fri night through Wed...

Friday night through Monday afternoon, a hot, western states ridge
of high pressure will give way locally to a dry cold front and a
large-scale upper-level low pressure trough and more zonal flow.
Fire weather concerns might be heightened with the passage of
those gusty frontal winds on Saturday. Only chances for precip are
isolated at best Sunday morning through Monday morning due to
embedded disturbances within this zonal flow.

Beginning Monday evening, the western states ridge of high
pressure builds back in through our region, giving us warmer and
drier conditions through at least Wednesday morning.




Synopsis: A very moist surface layer lingers over our eastern CWA
edge. Enough in fact to allow fog and low clouds to persist there
through this early morning hours. Compared to yesterday, this
round will be less extensive as the low pressure trough continues
to move further eastward and drier air filters in from the west.

Flight Conditions: VFR, except KSDY is expected to deteriorate
down to LIFR/VLIFR into airport minimums from 09Z through around
16Z. VFR conditions should return thereafter.

Winds: Generally light and variable, with some slight easterly or
south-easterly component from time to time.




Dry cold fronts are expected on Thursday and Saturday. Both of
them will bring gusty northwest winds in the afternoon and
evening. On Thursday, highs will be in the 80s with min RH 15 to
25 percent. NW winds around 15 mph behind the cold front on
Thursday may create critical fire weather conditions over parts of
Northeast Montana. Given the recent tendency for models to under
forecast winds especially behind cold front and the extremely dry
conditions, will issue a Fire Weather Watch for Thursday
afternoon and evening to highlight the possibility of critical
fire weather conditions.

On Saturday, highs will be near 90 in most areas with min RH 15 to
25 percent. NW winds behind the cold front will be around 15 mph
which could create critical fire weather conditions again.


Fire Weather Watch from Thursday afternoon through Thursday
evening for MTZ120-122-134>137.


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