Area Forecast Discussion
Issued by NWS Great Falls, MT

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054
FXUS65 KTFX 220429
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1028 PM MDT Fri Apr 21 2017

UPDATED AVIATION

.UPDATE...

10 pm update...Fog grids have been updated as clearing is beginning
in our northwest areas and poised to extend southeast through the
remainder of our region through tonight. This clearing combined
with light winds should result in at least patchy fog which could
be quite dense at times locally. Cassell


708 pm update...Issuing an early update to raise PoPs/QPF a bit
in accordance with latest observed trends. Mainly utilized the
SREF as it seems to have the slowest downward trend in
precipitation coverage. There are no other significant changes
with any other weather parameters, though we will continue to
monitor for fog potential later tonight. Cassell

&&

.AVIATION...
Updated 0428Z.

A weather disturbance continues exiting to the east, as a high
pressure ridge builds-in from the west. Mainly VFR should prevail
over Southwest MT, but KHLN may experience occasional MVFR CIGS
through about 08Z/Sat. For North-Central MT, MVFR to occasionally
IFR CIGS and resulting mountain obscuration are expected to finally
dissipate between roughly 15Z and 18Z/Sat. Patchy, dense fog may
occur through 16Z/Sat, but confidence in fog formation at any North-
Central MT terminal remains low. Where fog forms, LIFR or VLIFR
VSBY/CIGS are not out of the question.
Jaszka

&&

.PREV DISCUSSION...
/ISSUED 525 PM MDT Fri Apr 21 2017/

Rest of Today through Saturday Night...Latest water vapor imagery
shows a weak mid-level low over central/southwestern at this
time. Lift and convergence within this low is keeping areas of
generally light rain/snow going across part of the area at this
time. However, there has been a noticeable decrease in the
coverage of precip over the past several hours and this trend
should continue as the mid level low shifts SE tonight. In its
wake, high pressure will build in at the surface with decreasing
winds. With lingering moisture and light winds tonight, the main
concern will be low clouds/fog. Low clouds may tend to limit fog
development, but any area that clears out could see patchy dense
fog quickly develop with visibility reduced to less than a mile at
times, especially from Midnight through early Saturday morning
and primarily in areas that saw heavier precip amounts over the
past 24-36 hrs. For now, we`ll hold off any dense fog products,
but this will be closely monitored tonight. In the mountains,
additional very light snow accumulations are likely through early
this evening, but significant impacts are not expected. Martin

Sunday through Friday...Overall an unsettled weather pattern will
reside over the region through much of next week. Precipitation
chances will increase once again on Sunday/Monday as the next
upper level disturbance moves across the Intermountain West. For
Tuesday and Wednesday, a stronger upper level disturbance will
move through the region during the afternoon hours on both days,
resulting in a fairly good chance for scattered showers,
especially over Southwest MT. During the overnight hours, the rain
could change to snow, especially for elevations above 5500 feet.
For Thursday and Friday, an upper level trof will still be over
the region. The chances for precipitation will be lower, but can`t
be ruled out at this point. In terms of temperatures, generally
seasonable to slightly below normal afternoon temperatures are
expected through the week. Brusda/Moldan


&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  34  61  38  56 /  60  20  10  60
CTB  29  57  38  56 /  20   0  20  40
HLN  31  63  40  58 /  40  10  10  50
BZN  29  61  37  58 /  50  20  10  50
WEY  20  48  29  50 /  30   0  10  40
DLN  28  58  39  57 /  10   0  10  50
HVR  37  58  38  58 /  50  20  10  50
LWT  32  56  38  57 /  80  30  10  60

&&

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

$$

weather.gov/greatfalls



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