Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 271131
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
531 AM MDT Tue Jun 27 2017

...Update to Aviation...

.SYNOPSIS...

An upper level low pressure trough in Western Canada will drift
over Montana for cooler temperatures today through Thursday. An
unsettled airmass will settle in over the region for scattered
showers and thunderstorms through the short term period. Breezy
westerly winds today and Wednesday will veer to the north on
Thursday.

&&

.DISCUSSION...

Today through Thursday...A moist Pacific cool front moved through
the forecast area overnight bringing scattered showers and
thunderstorms. Unsettled conditions will continue today but
afternoon high temperatures will be 10 to 20 degrees cooler than
those of Monday. As a result, CAPE values will be correspondingly
lower today as well, along with the risk for strong to severe
storms. An upper level low currently over British Columbia will
move to central Alberta/Saskatchewan by late today then remains
quasi-stationary through Wednesday before deepening and drifting
southward. This will place the Great Falls CWA beneath a cool
northerly flow aloft with a Canadian surface cold front expected
to push into the state late Wednesday night or early Thursday
morning. Another round of scattered showers and thunderstorms will
accompany this system and Thursday high temperatures are expected
to fall another 5 to 10 degrees. Forecast precipitation amounts
through the short term period will range from about one tenth to
one quarter of an inch for much of the CWA. Unfortunately, my far
northeast zones, where drought conditions have taken hold will
likely receive less than one tenth of an inch. mpj

Thursday night through Monday night...The upper level pattern
will remain very progressive in nature, with no one single trough
or ridge remaining in place for more than 24 to 36 hours at a
time. High temperatures will warm each consecutive day through
Monday, with readings generally rising above climatological norms
by the weekend, and well above normal highs for the day on Monday.
While sporadic chances for showers/thunderstorms will be possible
through the first half of the long term (through Saturday
evening), precipitation amounts look to be very light (with the
exception of those areas that see a thunderstorm, which could
produce some marginal QPF amounts). The biggest concern in the
long term (at this time) will be the day on Monday, as upper level
ridging breaks down, dry/breezy downsloping winds develop, and
high temperatures climb into the 80s to low 90s. The combination
of unseasonably warm temperature, low minimum RHs, breezy
west/southwest winds, and the ongoing curing of fuels...will
create at least some elevated fire weather concerns (at this time)
for the day and into the evening hours on Monday (especially
across North Central Montana). Given that Monday will be the eve
of Independence Day, felt it was prudent to mention my concerns
for fire weather conditions, despite it being at the end of the
long term period. - Moldan

&&

.AVIATION...
Updated 1131Z.

Upper level low over British Columbia moves eastward to central
Alberta/Saskatchewan today. Moist and somewhat unsettled south to
southwest flow aloft over Montana will bring variable mid and high
level clouds with scattered showers and thunderstorms through 03Z
Wednesday. VFR conditions will prevail through the forecast period
with local MVFR possible in precipitation and areas mountain
obscurations. Surface winds will be westerly and breezy with gusty
and variable winds expected near thunderstorms. mpj

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  76  50  77  49 /  50  10  10  30
CTB  76  48  74  48 /  40  10  20  30
HLN  79  53  78  51 /  30  10  10  20
BZN  75  47  74  46 /  70  20  30  30
WEY  68  38  65  37 /  60  30  50  30
DLN  73  47  72  45 /  50  30  30  20
HVR  80  51  80  51 /  40  10  10  20
LWT  74  49  75  47 /  50  20  10  20

&&

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

$$

weather.gov/greatfalls



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