Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 111100
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
500 AM MDT Fri Aug 11 2017

Updated Aviation Discussion

.SYNOPSIS...

An approaching disturbance across southern Canada will introduce
the potential for isolated showers and thunderstorms across the
region this afternoon and evening. By the weekend, we begin to see
a shift in the weather pattern with the next storm system
approaching the region from the west. Showers and thunderstorms
will be possible Saturday and Sunday evening, with the better
chance of widespread showers and storms Sunday afternoon and
evening. Unsettled weather may extend into the early part of next
week with temperatures remaining near-average through the time
period.


.DISCUSSION...

Today through Sunday... Latest water vapor satellite imagery across
the region this morning illustrates a rather well-defined shortwave
trough across parts of southern Saskatchewan and Alberta. This
shortwave is progressing southward along a persistent northwesterly
flow aloft across the state. At the surface, high-resolution model
data suggests ongoing showers and thunderstorms for northern and
eastern areas of the CWA this morning, with the potential for
further development this afternoon and evening. Additionally,
elevated thunderstorms look possible across the Rocky Mountain
Front due to a developing surface upslope flow. Conditions turn
tranquil overnight tonight as the shortwave trough exits the area.
Saturday should be mainly dry areawide with the exception of more
isolated elevated thunderstorms along the higher terrain of the
Rocky Mountain Front. The next storm system approaches our area
from the west Sunday afternoon and evening which will aid in the
development of widespread showers and storms for central and
western areas. Impacts from these storms include the potential for
strong gusty winds in any stronger storm and brief heavy
downpours. Dangerous lightning will also pose a risk for new fire
starts due to ongoing drought conditions. KLG

Sunday night through Friday... Look for ongoing convective activity
into the night on Sunday with widespread showers, and a few strong
thunderstorms across most central and northern areas of the CWA.
Latest model guidance suggests the pattern to remain rather
unsettled into the day on Monday with showers and storms to
continue, mainly for central and southwestern areas of the state. We
return to a zonal upper level flow pattern by mid-week and into late
in the week with only a limited chance of seeing a spotty shower or
two. Temperatures will maintain rather seasonal through this time
period with no sign of any extreme heat in the foreseeable future
KLG

&&

.AVIATION...
Updated 1100z.

A potent disturbance will push a front south across the plains and
into central and southwest Montana by this evening. This will bring
-SHRA and -TSRA beginning this morning to the Hi-Line (including
KCTB and KHVR) and then extending south through the rest of the
terminals through the remainder of the afternoon and evening hours.
Expect VFR conditions except for MVFR or IFR in the heaviest
showers/storms. The primary impact from the storms will be gusty and
erratic winds, with frequent lightning also a threat. Area wildfires
will continue to filter in smoke and haze across the region through
the period, generally affecting terminals along and south of a KHLN
to KBZN line. Some slight reductions of visibility to around 6SM at
times will be possible due to these hazy conditions. Moldan/CC

&&

.FIRE WEATHER...

Continued northwest flow along with a weather front will bring
slightly higher RH values. Unstable conditions will keep chances
for afternoon and evening showers and thunderstorms...with the
main threats again being gusty winds and lightning. Saturday looks
to see warming temperatures with lowering RH. A few thunderstorms
are also possible...mainly along the Rocky Mountain Front and the
southwest. There are indications a pattern shift is possible
Sunday into early next week. This may bring increased westerly
winds with some scattered showers and thunderstorms. Anglin/CC

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  81  52  85  54 /  20  20  10  10
CTB  79  51  84  51 /  20  20  10  10
HLN  85  56  88  56 /  20  20  10  10
BZN  84  52  85  51 /  20  20  10  10
WEY  73  42  77  40 /  30  30  20  20
DLN  82  50  84  51 /  20  20  10  10
HVR  81  53  85  54 /  30  20  10   0
LWT  80  52  81  51 /  30  20  10   0

&&

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

$$

weather.gov/greatfalls



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