Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 050243
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
843 PM MDT Tue Aug 4 2020


.SYNOPSIS...

A ridge of high pressure moving east across the northern Rockies
and Montana will maintain mostly dry conditions across the region
through Wednesday. Temperatures warm on Wednesday and Thursday
with a better chance for showers and thunderstorms on Thursday
before somewhat cooler but breezy conditions return for Friday and
Saturday.

&&

.UPDATE...

The evening update has been published. Isolated thunderstorm
activity over Southern Beaverhead County will continue to wind
down and end this evening as daytime heating diminishes. High
pressure builds in tonight and will keep skies mostly clear and
winds light. Low temperatures will mostly be in the 40s and 50s,
though some of the normally cooler basins may see some 30s.
Wednesday still looks to begin mostly clear but a weak disturbance
is expected to move into the region from the southwest and bring
a chance for some isolated shower and thunder activity for
portions of Central and Southwest Montana, especially over higher
terrain. Highs should warm back to the 80s and lower 90s for most
lower elevation locations. RCG

&&


.AVIATION...
Updated 541 PM MDT Tue Aug 4 2020 (05/00Z TAF Period)

VFR conditions are expected for this TAF period, with light winds
and mostly clear skies. There are a few thunderstorms developing this
evening along the MT/ID border but they are not expected to impact
the terminals. A weak weather system is expected to move in from the
southwest by Wednesday afternoon and will bring an increase of mid -
to high level cloudiness. Some isolated showers and thunderstorms
will be possible over parts of the central and southwest but left
the mention of thunder out due to low confidence in any impacts to
the terminals. RCG

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

NOTE: Amendments not scheduled for Ennis (KEKS) due to ongoing
runway closure.

&&

.PREV DISCUSSION...
/ISSUED 250 PM MDT Tue Aug 4 2020/

Tonight through Friday...

Upper level ridge and surface high continues to shift east across
the region tonight, for mainly clear and dry conditions as well as
light winds. Some cumulus is developing this afternoon across the
higher terrain of the central MT mtns and along the mtns near the
Idaho border and cannot rule out an isolated thunderstorm in
areas near the ID border. Flow aloft turns south to southwesterly
again Wednesday, allowing some limited moisture to move north into
the region ahead of a weak upper level system moving into the
Great Basin. Expect at least isolated thunderstorms to develop
over the higher terrain of SW MT with heating Wednesday afternoon
with some of this activity lifting north into central MT Wednesday
evening. The upper level disturbance in the Great Basin lifts
north through MT Thursday ahead of a larger scale trough moving
into the Pacific NW for a more widespread coverage of showers and
thunderstorms across the forecast area Thursday afternoon and
evening. There is some potential for strong to isolated severe
storms late Thursday with better wind shear likely ahead of the upper
level system and a cold front moving into the region Thursday
night. Main uncertainty is related to the degree of instability
and level moisture return into the region from the east by late
Thursday as well as the amount of higher level cloudiness that
could be present. Surface cold front and upper level trough move
across the region by Friday morning with breezy to windy but
cooler conditions likely through Friday afternoon. Hoenisch

Friday night through Tuesday...

As the upper level trough pushes off to the east Friday night, zonal
flow will set up shop for the weekend. Though winds will be slightly
weaker than they were on Friday as the trough passed through, it
will still be quite gusty. With winds near the top of the mixing
layer around 25-35 mph, wind gusts will reach around 25-30 mph along
the Northern Rocky Mountain Front, with wind gusts reaching 20-25
knots on the adjacent plains to the east. The forecast for Sunday is
a little less certain, as a weak trough passes to the north of the
region. While previous ensemble runs were to bring the trough closer
to the area, it appears as if the trend has been to take it a little
further to the north on the last few runs. This more northerly track
should result in Sunday being less breezy than Saturday, and the
winds have been adjusted to show this idea. Upper level ridging
looks to build into the area early next week, which will allow for
a gradual warming trend as we head into early next week. Ludwig

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  54  90  59  91 /   0   0  10  30
CTB  51  88  54  89 /   0   0   0  20
HLN  54  91  58  91 /   0  10  20  40
BZN  51  90  54  91 /   0  10  10  30
WYS  38  83  42  83 /   0  10  10  30
DLN  49  86  53  86 /   0  20  20  40
HVR  53  92  60  96 /   0   0  10  10
LWT  51  86  56  90 /   0   0  10  30

&&

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

$$

http://www.weather.gov/greatfalls


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