Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 192033
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
233 PM MDT Sat Jul 19 2014

.DISCUSSION...

Tonight through Monday...Strong winds aloft and a tight surface
pressure gradient will keep brisk winds across the northern portions
of the region through the evening. A high wind warning has been
issued for the Northern Rockies and several wind-prone areas are
seeing some gusts in excess of 60 mph. A pair of shortwaves aloft
will cross the Rockies this evening and a weak, associated cold
front will push south across the Canadian border Sunday. This front
will be weak and the main effect will be to cool the air mass across
the northern half of the CWA. The winds aloft will weaken during the
day Sunday and the current timing on the high wind warning, expiring
at 6 pm, seems fine. The jet will move east Sunday night but another
weak shortwave will cross the region Monday. This shortwave will
move through moist, southwest flow aloft and will help destabilize
an air mass that is already unsettled. Most of the forecast area
will see afternoon convection develop although the northwest zones,
including the Northern Rockies, should remain stable. Zelzer

Monday night through Saturday...The medium range period begins with
a closed upper low approaching British Columbia. Southwest flow
aloft resulting from this feature will bring moisture and
instability to the area with scattered thunderstorms developing over
the mountains of southwest Montana and then spreading north and east
over the plains Monday night. The upper low remains quasi-stationary
Tuesday offshore British Columbia. Diffluent southwest flow aloft
will contribute to thunderstorms again developing during the
afternoon and evening. By Wednesday, both the GFS and ECMWF models
begin to push the low inland. The airmass over the area will remain
unstable with afternoon convective activity again a possibility. The
models move the closed upper low across southern Canada on Thursday
with the ECMWF faster in pushing said feature east. With the low
centered further north than previously thought, the main
precipitation shield will remain in Canada with only isolated
thunderstorms over North Central Montana. By Friday, the GFS places
the low over southern Saskatchewan while the ECMWF has it over
central Manitoba. Westerly flow aloft will be over the area with
little to no precipitation the result. Upper ridging builds over the
area in the wake of the low`s passage Saturday with dry but cooler
conditions. Temperatures will be near seasonal averages to start the
period but will drop below seasonal averages by week`s end.

&&

.AVIATION...
UPDATED 1800Z.
Areas of smoke will continue to reduce visibility to MVFR at times
as westerly flow aloft persists. As surface winds continue to
increase this afternoon, conditions should improve, however
mountains will remain obscured through the period. Wind gusts along
the Rocky Mountain Front and adjacent plains, including KCTB could
gust up to 40kts this afternoon. Elsewhere across the plains, wind
gusts up to 35kts are expected. Winds should increase in the
southwest valleys this afternoon as well with wind gusts up to 20kts
possible at KHLN and KBZN. An isolated thunderstorm is possible this
afternoon in the higher terrain along the Rocky Mountain Front and
International Boundary, otherwise dry and VFR conditions will
prevail through the forecast period. MLV

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  60  85  57  81 /   0  10  10  30
CTB  55  79  52  80 /  10  10  10  20
HLN  60  89  60  81 /   0  10  10  40
BZN  52  88  55  77 /   0  10  10  50
WEY  42  79  44  70 /  10  10  30  60
DLN  52  87  55  74 /   0  10  20  50
HVR  61  86  55  86 /  10  10  10  20
LWT  57  88  55  81 /  10  10  20  40

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING until Midnight MDT Sunday Night Northern Rocky
Mountain Front.

&&

$$

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