Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 151647
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1047 AM MDT Tue Aug 15 2017

.UPDATE...
1045 AM Update...
Updated forecast is out. Only tweaks were too temperatures. Fog is
burning off in the West Yellowstone area. Left border pops as is
for this afternoon...but most areas should be dry/sunny. Brusda

730 AM Update...
Updated morning forecast to remove rainfall over Southwest MT, as
it has moved eastward. Also tweaked the fog area and density, as
West Yellowstone reporting less than 1/4 mile visibility. Brusda

&&

.SYNOPSIS...
A west to northwest flow aloft is developing over the region. As a
result, expect several days with little to no precipitation.
Afternoon temperatures will be on the warm side...with highs
generally in the mid to upper 80s.

&&

.AVIATION...
Updated 1650Z.
VFR conditions will prevail over the region through the period.
The only exception will be that distant mountain/pass visibility
will be limited to less than 20 miles at times due to wildfire
smoke. Brusda

&&

.PREV DISCUSSION...
/ISSUED 520 AM MDT Tue Aug 15 2017/

Today through Wednesday...broad troughing over the Northern Rockies
and Northern High Plains will persist for the next 18-24 hours,
before near-zonal flow overspreads the region for the day on
Wednesday. Showers and thunderstorms will once again be possible
over Southwestern Montana and into portions of Central Montana,
however, areal coverage today is expected to be significantly lower
than yesterday. Believe that today`s shower/storm activity will be
more orographically focused despite continued cyclonic flow over
the region, mainly because the synoptic ascent and available
moisture is very weak/limited. High temperatures will remain below
normal for today, but should be a degree or two warmer than Monday.
Precipitation chances will gradually come to an end by the evening
hours, as the H700 and H500 flow becomes more zonal in nature. This
upper level pattern will continue into the day on Wednesday, which
should bring dry and warming conditions to all of North Central and
Southwest Montana. High temperatures will climb to and/or slightly
above normal for the day on Wednesday. With westerly flow present in
the mid levels, downsloping effects are expected across North
Central Montana, which will cause Minimum Relative Humidity values
to fall well below 20 percent. While winds will become brisk during
the afternoon as mixing occurs, am not currently expecting frequent
wind gusts in excess of 25 mph. None-the-less, elevated fire weather
concerns will exist for the day on Wednesday due to the very dry air
expected.

Wednesday night through Thursday...a quick moving shortwave is
expected to dive southeast from Canada during the late evening hours
on Wednesday/morning hours on Thursday. This disturbance is
generally expected to be dry in nature, however, will bring a
noticeable wind shift to the region. Current thinking is that a weak
surface front will begin to dive southeast across North Central
Montana during the late morning/early afternoon hours on Thursday,
which will cause westerly winds to turn to the northwest. Sustained
wind speeds of 10 to 15 mph and gusts approaching 25 mph are
currently expected during the afternoon hours on Thursday across
North Central Montana, which when combined with critical to near
critical relative humidity values, will lead to another day of at
least elevated fire weather concerns. - Moldan

Thursday Night through Monday...Generally dry conditions along with
moderating temperatures are expected for the remainder of the work
week. By the weekend, the pattern appears favorable for increasingly
breezy conditions, especially over the plains of central MT. This
may come after a warm/dry period and certainly bears watching for at
least elevated fire concerns. In addition, a wind shift with a cold
front may add to the concerns Saturday night and/or Sunday. Current
sky cover forecasts depict mostly favorable conditions for solar
eclipse viewing Monday with dry conditions expected across central
and southwest Montana, but this will continue to be monitored in the
hopes of achieving greater confidence as the event approaches.
MARTIN/CC

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  81  48  85  52 /   0  10   0   0
CTB  80  45  82  51 /   0  10   0   0
HLN  83  50  84  52 /   0  10   0   0
BZN  78  46  82  48 /   0  10   0  10
WEY  67  37  72  38 /  10  10  10  10
DLN  77  46  80  47 /   0  10   0   0
HVR  81  50  87  52 /   0  10   0   0
LWT  78  49  82  51 /   0  10   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

weather.gov/greatfalls



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