Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 191219
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
615 AM MDT Sat Aug 19 2017

...UPDATED AVIATION SECTION...

.SYNOPSIS...
A northwest flow aloft will continue hazy skies with a few clouds
over the region through the remainder of the weekend. A Canadian
cold front will move south over the plains today, shifting winds
more northerly, with strong gusts for an hour or two after frontal
passage. Winds will not shift until this evening across southwest
Montana, and they will not be quite as strong. However, this wind
shift should help disperse some of the smoke at lower elevations
across the entire region. Overall, winds will become lighter for
the rest of the weekend, as temperatures remain slightly below
normal.

&&

.DISCUSSION...

Today through Monday...A band of mid and high level clouds ahead
of a broad shortwave trough kept overnight temperatures quite
mild over much of the forecast area. However, a Canadian cold
front with gusty northerly winds has just crossed the
international boundary as of early this morning. Winds were
already gusting to around 40 mph at the Sweet Grass port of entry.
Similarly gusty northerly winds will accompany the frontal passage
and linger for a couple hours after passage as it moves south over
the plains of north central Montana this morning into this
afternoon. This change in wind direction will help mix out some of
the smoke over this area. The front will not make it into
southwest Montana until this evening, allowing gusty westerly
winds to mix down to the surface during the afternoon. As lower
and mid level winds shift more northerly this evening, some of the
smoke will be dispersed there as well. Areas of mid and high
clouds will pass over the area into the evening as the main
shortwave energy passes over the area. A drier northwest flow
aloft on the back side of the shortwave trough will help clear out
skies on Sunday. Another disturbance will move through the flow to
bring areas of mid and high clouds to the forecast area again
Sunday night into Monday morning, but it appears that these clouds
will mostly exit the area in time for the solar eclipse around
noon on Monday. Overall, winds will be light tonight through
Monday with slightly below normal temperatures.
Coulston

Monday Night through Saturday...A high pressure ridge aloft will
traverse the CWA from west to east Monday night through
Wednesday, resulting in warmer temperatures and primarily dry
weather. Somewhat cooler temperatures, along with scattered
showers and thunderstorms, remain possible next week Thursday and
Friday due to an upper-level trough digging southward and
eastward from British Columbia. Drier conditions and slightly
warmer temperatures may return by Saturday of next weekend, as
another high pressure ridge aloft builds-in from the south and
west. Low and high temperatures are still expected to be near or
slightly above-normal during the period. The warmest readings
will likely occur Tuesday and Wednesday, when the first of the
two aforementioned high pressure ridges is overhead.
Jaszka

&&

.AVIATION...
Updated 1215Z.

VFR conditions will mostly continue across north central and
southwest Montana through at least 12Z Sunday. However, wildfire
smoke may reduce visibility to high MVFR levels at times through 18Z
or so, mainly along and south of a KGTF-KLWT line. Otherwise, a
Canadian cold front has already moved south of a KCTB-KHVR line, and
it will continue to move south of a KGTF-KLWT line by 18Z. Gusts of
25 to 35 kt have been common with the frontal passage and for an
hour or two afterward. The front will not move into southwest
Montana until after 00Z, and by then, strong wind gusts will be
unlikely. Mid level clouds will also spread south over the plains
behind the front, but they will likely dissipate between 20Z and 02Z.
Coulston

&&

.FIRE WEATHER...

A Canadian cold front will continue to bring gusty northerly winds
with good humidity recovery to the plains this morning, so have
allowed the Red Flag Warning there to expire.

However, these more northerly winds with cooler and less dry air
will not make it into southwest Montana until this evening.
Before then, winds will become gusty out of the west once again
across much of this area this afternoon. Winds of 10 to 20 mph
with gusts to 30 mph at times will be likely, as relative
humidity percentages fall into the teens once again. Have
therefore issued a Red Flag Warning for fire zone 116 due to
ongoing fires there for the Noon to 9 pm MDT time frame. NWS
Missoula also has a Red Flag Warning in effect for fire zone 110
(Deer Lodge/western Beaverhead National Forest), valid until 9 pm
MDT as well.

Additional fire weather highlights are possible again early next
week, as it will remain warm and dry with low humidity and
potentially gusty winds at times.
Coulston

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  79  50  81  50 /  10   0   0   0
CTB  73  44  77  46 /  10  10   0  10
HLN  84  52  83  53 /  10   0   0   0
BZN  85  48  83  49 /   0   0   0   0
WEY  76  36  76  38 /  10  10   0   0
DLN  83  45  81  47 /   0   0   0   0
HVR  77  50  82  51 /   0   0   0  10
LWT  78  50  80  50 /   0  10   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon today to 9 PM MDT this evening Eastern
Beaverhead National Forest...Lincoln Ranger District of the Helena
National Forest.

Red Flag Warning until 9 PM MDT this evening Deerlodge/Western
Beaverhead National Forest.

&&

$$

weather.gov/greatfalls


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