Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 272057
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
257 PM MDT Sat Sep 27 2014

.DISCUSSION...

Tonight through Monday...Light rain will continue across
north-central and southwest Montana this evening, however some
forecast models hint that the precipitation coverage and amounts
will decrease after midnight. Already this afternoon, precipitation
has ended for areas south of line from Helena to White Sulphur
Springs, however water vapor satellite indicates another plume of
moisture pushing into central Idaho, which should move into
southwest Montana late this evening/tonight. Thus, have kept the
highest chance of pops across southwest Montana extending north into
areas east of I-15 and north of MT-200 through midnight. After
midnight, forecast confidence decreases regarding precipitation
amounts and coverage but have trended down as the best moisture
transport and upper-level low shifts farther south and east.
Precipitable water amounts will remain 3 to 4 standard deviations
above average. Have kept likely to categorical pops in the mountains
across central and southwest Montana as well as areas in Fergus and
Blaine counties with chance pops elsewhere tonight, then continue a
gradual decrease in pops/qpf from northwest to southeast on Sunday.
Additional precipitation amounts will range from 0.20 inches to 0.50
inches, with less than 0.20 inches for areas along and northwest of
a line from Helena to Great Falls and Havre. By Sunday night and
Monday, a chance of showers will remain in the mountains but overall
precipitation will have ended in the plains and valleys. At this
time, forecast models keep mostly cloudy to overcast sky cover on
Sunday night, but any clearing will allow for areas of fog to
develop. Temperatures will remain below seasonal averages on Sunday,
then around seasonal average on Monday as winds shift southerly. MLV

Monday night through Saturday...The weather pattern will remain a
bit unsettled over the region through Thursday...but then quiet and
fairly nice weather conditions should return by next weekend. A
slowly moving upper level low will affect the weather pattern for
Tuesday and Wednesday...as it pushes northward from the central
Rockies into the upper Midwest. Expect scattered showers to pass
through the region...but no organized areas of widespread rain are
expected. For Thursday...the flow aloft shifts to the
Northwest...and a fast moving upper level disturbance will slide
southeastward through the region. This disturbance will also produce
some scattered showers as it moves through. Then for Friday and into
next weekend...both the GFS/EC prog an upper level ridge of high
pressure to rebuild over the Northern Rockies. This will result in
mostly dry conditions...along with a return of mild/warm
temperatures. Thus afternoon highs will be in the 60s on
Tuesday...and then cool a bit for Wednesday/Thursday with highs in
the 50s. Afternoon temperatures will start to warm back into the 60s
on Friday...then continue to warm on Saturday...with 70s expected
for many areas. Brusda

&&

.AVIATION...
UPDATED 1759Z.
Periods of -RA/RA will affect areas south of KCTB and KHVR into this
evening with MVFR/IFR expected at times. Then, the heaviest rainfall
potential tonight exists at KBZN and KLWT where IFR is forecast with
possibly a brief period of LIFR with CIGS between 1-2 kft AGL and
visibilities down to 2-4 miles. Conditions will improve to MVFR/IFR
after 12z/Sunday. Uttech

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  44  54  42  64 /  90  40  20  20
CTB  40  53  40  62 /  40  30  20  20
HLN  46  59  42  67 /  90  40  20  20
BZN  42  53  38  64 / 100  60  60  20
WEY  34  54  30  54 / 100  80  70  40
DLN  42  55  41  62 /  90  60  50  40
HVR  43  57  41  62 /  80  30  30  40
LWT  42  51  40  62 / 100  80  70  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

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