Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 180554
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1155 PM MDT Sat Aug 17 2019

...AVIATION SECTION UPDATED...

.UPDATE...

Only minor adjustments to the overnight forecast. A few lingering
rain showers will continue to move over the mountains of Central
Montana this evening, but they should diminish by midnight and not
produce much additional rainfall. Otherwise, have increased
overnight relative humidity somewhat. The recent rainfall will
likely keep low level moisture fairly high, allowing cooling
overnight temperatures to cause some patchy fog development in
some valleys and low lying areas (such as river valleys). Am not
confident that the fog potential will be widespread, as persistent
high cloudiness over the area, along with breezy southwest winds
along the east slopes of the Rockies after midnight, should limit
significant fog development. Otherwise, the cool overnight lows in
the forecast appear to be on track.  Coulston

&&

.SYNOPSIS...

Except for a few lingering showers over the Central Montana
mountains this evening, a northwest flow aloft will keep areas of
mid and high level cloudiness over the region tonight, with patchy
fog possible in some valleys and low lying areas. Overnight
temperatures will be somewhat below seasonal averages and in the
40s for many locations. Much warmer and drier conditions develop
Sunday and persist through much of the upcoming week as a high
pressure ridge gets re-established across the western United
States.

&&

.AVIATION...
Updated 1155 PM MDT Sat Aug 17 2019 (18/06Z TAFs)

All precip has moved out of the CWA, along with low clouds. Expect
light winds and clearing skies overnight into Sun AM. Gusty SW-W`ly
winds will develop late morning or early afternoon for all sites,
with the strongest winds expected from Helena north into the north-
central plains. VFR conditions prevail thru the period, outside of
any patchy fog Sun AM. -Kredensor

&&

.FIRE WEATHER...

A warming and drying trend will begin on Sunday with warmer than
average temperatures and lower afternoon humidity persisting
through much of the upcoming week under a building upper level
ridge. Weak weather disturbances moving through the ridge will
bring some periods of breezy winds late Sunday and again Monday,
mostly to north-central MT, as well as a slight chance of
isolated thunderstorm development, particularly over SW MT Monday
and Tuesday. Potential exists for a dry cold front passage late
Wednesday or Thursday as the upper level ridge weakens.
Warmer/drier and breezy conditions will accelerate the drying of
fuels this week with increasing fire weather concerns expected by
Wednesday and Thursday.

&&

.PREV DISCUSSION...
/ISSUED 525 PM MDT Sat Aug 17 2019/

Tonight...Upper level trough and emebedded shortwave disturbance
shift east of the area this evening for clearing skies overnight.
Surface high pressure also drifts SE across eastern MT for
generally light winds. Upper level ridging builds into the
Northern Rockies and MT Sunday for a quick rebound in
temperatures with most locations returning to seasonally warm
conditions by Sunday afternoon.

Monday through next Saturday...The ridge amplitude appears to
peak on Wednesday, before flattening and giving way to a westerly
flow in the mid-levels for the remainder of the week. Expect
warming temperatures through Wednesday, when highs will approach
the 90 degree mark for many areas. Near normal temperatures are
then forecast from Thursday into the weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  48  82  53  85 /   0   0   0   0
CTB  47  79  50  80 /  10   0   0   0
HLN  47  85  53  88 /  20   0   0  10
BZN  43  87  49  90 /  10   0   0   0
WEY  36  79  40  84 /  10   0   0   0
DLN  43  84  49  87 /   0   0   0   0
HVR  46  83  53  85 /   0   0   0   0
LWT  42  80  51  84 /   0   0   0  10

&&

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

$$

http://www.weather.gov/greatfalls


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