Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 221617
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1015 AM MDT Tue Jul 22 2014

.UPDATE...
Current forecast in good shape; only made a few minor tweaks to
increase precipitation coverage of the showers currently over
northern Judith Basin and northern Fergus counties.  Still expect
the line of showers from Lincoln-to-Monarch-to-Lewistown to move
gradually northward, with scattered showers and few embedded
pulse-type thunderstorms developing over north central counties this
aftn/eve.  Second area of showers/storms will also develop later
over southwest MT as moisture pushes north from Idaho.
Waranauskas

&&

.DISCUSSION...
Tuesday through Thursday...An active weather pattern will continue
through the short term as an upper level low continue to exert its
influence as it moves down the Canadian coast towards Washington,
and then Montana. A series of shortwave troughs will move into the
area ahead of this system the weaker of the two should impact the
area Today bringing an enhanced potential for strong thunderstorms
and showers across the region. The stronger impulse will move over
the area on Wednesday and has a better chance of enhancing
thunderstorms strong enough to produce damaging hail and wind. It
currently appears that the best combination of sheer and instability
for Wednesday exists across the high plains of Central
Montana...extending west over the Rocky Mountain Front. Dry air near
the surface should allow for strong outflows, possibly damaging, to
develop from these storms. Decent lapse rates should allow for
strong updrafts in storms that organize in the sheared environment.
Hail growth will be limited by the high freezing level, but any
storm strong enough to maintain its height in this environment
should be able to produce a decent amount of small hail and possibly
hailstones larger than an inch in diameter. By Thursday the low
pressure system will move quickly across the area bringing strong
gusty winds to at least the Northern Rocky Mountain Front and
adjacent high plains. Have issued a high wind watch for this area
beginning Thursday morning and continuing through the day Thursday.
The greatest potential for damaging winds appears to be over by late
Thursday night. Suk

Thursday night through Monday...The main message during the period
will be warming temperatures and dry conditions as a strong ridge
aloft develops over the western United States. Thursday evening
will start off with an upper low over southern Alberta. Associated
cool air could bring some very light snow to the mountains of
Glacier Park.At this time snow levels could range between 7500 and
8000 feet. Also Thursday evening strong westerly flow aloft
associated with the upper low could result in high winds over
Glacier..Toole..and Pondera Counties. Dry westerly flow aloft is
expected Friday with highs near 80. Over the weekend into Monday
the development of the strong ridge will occur. Even as
temperatures warm...a relatively dry airmass and the upper ridge
should result in no precipitation over the weekend. Early next
week monsoonal moisture will move into the forecast area but
models differ on its timing. At this time have opted to keep the
weather warm and dry on Monday though isolated showers and
thunderstorms are not out of the question for far southwest
Montana. Blank



&&

.AVIATION...
UPDATED 1125Z.
VFR conditions will prevail through the next 24 hours. Scattered
showers will affect central Montana this morning impacting mainly
KLWT. The main problem with the taf forecasts was figuring out how
showers and thunderstorms will play out this afternoon and evening
as forecast models have differing scenarios. Confidence that showers
and thunderstorms will be mainly confined to the 21z-03z time frame
is high but confidence in picking out a specific period when showers
and thunderstorms could occur at any particular point is low. Keep
in mind that wind gusts near 40 kts and/or MVFR conditions in
heavier rain will be possible with thunderstorms this afternoon and
evening. Showers with an outside threat of a thunderstorm should
affect KHLN late tonight but also could possibly get near KGTF and
KLWT.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  84  62  89  60 /  40  30  60  50
CTB  81  55  86  54 /  40  30  50  70
HLN  88  61  92  59 /  40  40  50  40
BZN  86  54  92  54 /  30  30  30  20
WEY  78  43  82  43 /  10  10  20  10
DLN  83  54  88  53 /  40  20  40  30
HVR  88  59  92  59 /  20  20  40  60
LWT  85  58  92  58 /  50  40  50  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WATCH from Thursday morning through Thursday evening
Eastern Glacier...Eastern Pondera...Toole.

HIGH WIND WATCH from late Wednesday night through Thursday
evening Northern Rocky Mountain Front.

&&

$$

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