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Area forecast discussion 
National Weather Service Great Falls Montana
540 am MDT Sat Aug 1 2015

Updated aviation discussion

Discussion...
today through Monday night...an upper ridge will be developing
over the Pacific northwest today and will gradually move east and
by Monday should be over central Montana. A weather disturbance
aloft will develop over the Great Basin Sunday and will move
towards southwest Montana on Monday. It will then move through
southwest Montana Monday evening and be over central Montana by
late Monday night. Monsoonal moisture ahead of the disturbance
will move into southwest Montana Sunday night and spread over the
remainder of the forecast area Monday. The approach of the
disturbance combined with weak instability will lead to scattered
thunderstorms over southwest Montana through the Rocky Mountain
front Monday afternoon. Then scattered showers and a few
thunderstorms will spread over the remainder of the forecast area
ahead of the disturbance Monday night. Until the monsoonal
moisture moves into the forecast area expect no precipitation and
there will be some near record high temperatures. A Canadian
airmass will move into the north late this afternoon and tonight
and should provide a few degrees of cooling in that region Sunday.
Blank

Tuesday through Saturday...there should be a southwest flow aloft
until late in the week with a few embedded weather disturbances.
The GFS and European model (ecmwf) differ with details of the associated
precipitation so will continue with the isolated to scattered
thunderstorm forecast idea. Towards the weekend there are indications
that a drier westerly to northwesterly flow aloft could develop.
Did lower the inherited chances of precipitation forecast slightly
for Friday but did not remove the mention of precipitation.
Temperatures will be quite a bit cooler than those of this
weekend with highs in the upper 70s to lower 80s by Wednesday. Blank



&&

Aviation...
updated 1140z.

There will be VFR conditions with generally clear skies. Surface
winds will remain light through this morning with west to northwest
winds of 10 to 15 kts this afternoon except for southwest Montana.
The position of a Canadian cold front will affect forecast wind
directions tonight over the plains with some guidance keeping it NE
of a kctb-kgtf-klwt line while other guidance has it SW of that
line. Confidence at this point is higher in the latter solution than
the former solution. Blank

&&

Fire weather...
hot and dry conditions will continue over the region through
Sunday with warmest temperatures and lowest afternoon humidity
over the plains expected to peak Saturday afternoon. Overnight
humidity recovery will be poor at middle-slope to Ridgetop locations
as overnight inversions/thermal belts persist. A very weak
weather disturbance aloft and deep mixing will bring a period of
breezy winds Saturday afternoon and early evening. Westerly winds
over the Rocky Mountain front and nearby plains should reach at
least 15 miles per hour with gusts of 20-25 miles per hour. This combined with extremely
low relative humidities in the 5 to 10 percent range will lead to
critical fire weather conditions and have upgraded the Fire
Weather Watch there to a red flag warning. Farther east winds will
be out of the northwest and more in the range of 10 to 15 miles per hour.
However with very low relative humidities of 5 to 15 percent have
decided to also upgrade the region to a red flag warning. A weak
weather system moving into the region from the SW will bring a
chance for thunderstorms late Monday and the increase in lightning
and potential for gusty thunderstorm winds following this period
of very warm and dry conditions may lead to additional fire
weather concerns on Monday. Hoenisch/blank

&&

Preliminary point temps/pops...
gtf 97 56 93 58 / 0 0 0 0
ctb 94 49 90 54 / 0 0 0 0
hln 98 56 98 57 / 0 0 0 0
bzn 94 52 94 54 / 0 0 0 10
wey 84 41 86 43 / 0 0 10 10
dln 92 51 92 55 / 0 0 10 10
hvr 94 56 91 57 / 0 0 0 0
lwt 92 56 90 57 / 0 0 0 0

&&

Tfx watches/warnings/advisories...
red flag warning from noon today to 9 PM MDT this evening for
mtz112>115-117.

&&

$$

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