Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 131119
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
515 AM MDT Sun Jul 13 2014

AVIATION SECTION UPDATED

.DISCUSSION...
Today through Tuesday...High pressure will gradually shift east
later Sunday before a shortwave trough from the Pacific heads
towards MT Monday. Expect an increased chance for more widespread
showers and thunderstorms Monday and Tuesday afternoon and
evening, especially along the Continental Divide. Temperatures
will remain close to 90 in many locations Sunday, before cooling
about 5 to 10 degrees for Monday and Tuesday. Winds may be breezy
out of the east ahead of the incoming trough Monday.

Tuesday Night through Sunday...Current forecast model runs for this
period show some marked improvement in continuity and agreement over
the wildly varying solutions mentioned in yesterday`s discussion.
Period begins with the shortwave trof that will bring scattered
precipitation on Tues gradually exiting into northern Wyoming by
Tues night. Weak high pressure will fill in behind the departing
trof, resulting in dry conditions for Wed. By late Wed night,
another upper-level trof swings through southwest Canada with the
southern end of the trof extending into central and southwest MT.
Both the ECMWF and GFS models indicate fairly widespread showers and
thunderstorms will develop ahead of/along the trof axis and its
associated surface cold front from Thurs aftn through Fri eve.
However, there is some concern that the models may be overplaying
the amount of Pacific moisture that will accompany the trof, and
hence, also overestimating the resulting precipitation amounts and
coverage. The wild card in this portion of the forecast is the
contribution of any monsoonal moisture that may push northward into
our region just ahead of the trof axis.  Right now, models don`t
indicate a significant monsoonal effect, though it may help increase
precipitation chances and amounts over portions of central MT from
Helena to Lewistown on Fri aftn/eve.  The trof heads into ern MT by
midday Sat, setting up westerly winds aloft that will result in
down-slope winds and dry conditions for Sun.
Waranauskas

&&

.AVIATION...
UPDATED 1115Z.
Strong, broad high pressure ridge will keep skies mostly clear with
light winds across central and southwest MT today.  Scattered clouds
and a few -SHRA/-TSRA should develop over the higher terrain near
KBZN and KHLN this afternoon, but forecast confidence for VCTS at
those terminals is too low to include its mention in TAFs at this
point.
Waranauskas


&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  90  57  84  57 /   0   0  10  20
CTB  87  53  82  51 /   0   0  20  30
HLN  94  60  88  58 /   0   0  30  30
BZN  88  53  83  51 /  10  10  30  30
WEY  81  43  79  43 /  10   0  40  40
DLN  88  55  84  54 /  10  10  40  30
HVR  89  53  82  52 /   0   0   0  10
LWT  88  52  81  52 /   0   0  10  20

&&

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

$$

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