Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 252254 RRA
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
500 PM MDT Tue Sep 25 2018

...Updated Aviation Discussion...

.SYNOPSIS...

Fair weather persists through the day on Wednesday with high
temperatures rebounding to near-normal. A Canadian cold front
crosses the border Wednesday evening and clears the Montana/Idaho
border by Friday. This will allow cooler and unsettled weather to
return Wednesday evening through Friday.

&&

.DISCUSSION...

Rest of today through Friday...Fair weather persists through the day
on Wednesday as high pressure builds slightly from the west and
northwesterly flow persists over our CWA. This northwesterly flow
aloft continues Wednesday night through Friday as multiple, embedded
disturbances affect the region. At the surface, a Canadian cold
front should cross the international border Wednesday evening and
then stall along a line near Dillon to West Yellowstone by Friday
morning. Periods of rain and mountain snow are expected along and
especially behind this front Wednesday evening through Friday, with
the bulk of precipitation falling on Thursday. However, little or no
precipitation may fall south of the I-90 corridor due to the
expected evolution of this cold front. Initial snow levels of
about 8000-9000 feet fall to as low as 3000-4000 feet MSL behind
the front. Thus, rain may change to wet snow for a time late
Thursday evening/early Friday morning at locations on the plains
and some of our valleys. However, little or no snow accumulation
is expected for these locales. Preliminarily, snow totals look to
reach a coating to 4 inches in the mountains, above 5000 feet. In
general, liquid precipitation totals look to reach 0.10 to 0.50
inches, with the greatest totals in the mountains. Near-normal
temperatures through Wednesday cool to below-normal Wednesday
night through Friday.

Friday night through Tuesday...Primarily fair weather is expected
Friday night into Saturday as shortwave high pressure ridging builds-
in from the south and west. Models then continue to struggle with
the evolution of Pacific shortwave energy and associated unsettled
weather Saturday night into early next week. Thus, forecast
confidence remains low. At this time, Sunday has the best potential
for additional precipitation. Temperatures will trend below-normal
through this period.
- Hoenisch/Jaszka

&&

.AVIATION...
Updated 2300Z.

VFR conditions will persist with northwesterly flow aloft over the
next 24-hours as high pressure ridging builds from the west.
Multiple disturbances embedded in this flow will contribute to bring
variable mid- to high-level cloudiness. A cold front will drop south
out of Canada and begin to impact the Hi-Line toward the end of the
TAF period. In general, surface winds will trend light and variable
with loss of daytime heating around 01z-02z, but will become gusty
again between 18z and 20z Wednesday afternoon ahead of the
aforementioned cold front.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  39  66  40  48 /   0  10  20  50
CTB  38  65  38  47 /   0  10  30  60
HLN  36  68  43  60 /   0   0  10  20
BZN  32  67  40  63 /   0   0   0  10
WEY  21  60  29  63 /   0   0   0   0
DLN  30  67  38  67 /   0   0   0   0
HVR  40  63  42  49 /   0  10  40  50
LWT  37  63  39  46 /   0   0  20  50

&&

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

$$

http://www.weather.gov/greatfalls


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