Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 240741
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
141 AM MDT Thu Jul 24 2014

.UPDATE...
The severe thunderstorm watch is no longer in effect as strong
storms have moved east of the forecast area. Also lowered the
chances of precipitation and sky cover for the rest of tonight. Blank

&&

.AVIATION...
UPDATED 2331Z.
VFR conditions are generally expected. Strong thunderstorms will
move out of north central Montana shortly after midnight but until
then expect MVFR/IFR conditions in heavy rain. Otherwise expect
isolated showers or possibly thunderstorms the rest of tonight.
For Thursday expect isolated showers or thunderstorms in the far
east with scattered showers or thunderstorms over the mountains of
the Rocky Mountain Front. A cold front will sweep through the area
from west to east late tonight and Thursday morning and will bring
gusty westerly winds. Local wind gusts in excess of 50 knots will
be likely over the northern Rocky Mountain Front and possibly as
far east as Toole County.

&&

.FIRE WEATHER...
Fire Weather Watch for fire zone 115 (Chouteau/Fergus counties)
and the southern third of Blaine County remains in effect with no
changes at this time. Gusty winds, sustained at 20 to 30 mph with
gusts around 40 mph, are likely on Thurs with afternoon humidities
dropping down to 20 to 25 percent range. There is also concern
that lightning starts from thunderstorms this evening may hold
over and then spread as the strong winds develop tomorrow.
Waranauskas

&&

.PREV DISCUSSION...
/ISSUED 1207 AM MDT Thu Jul 24 2014/
FXUS65 KTFX 240607
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1207 AM MDT Thu Jul 24 2014

..UPDATE TO AVIATION...

UPDATE...
Have dropped the severe thunderstorm watch except for north
central Montana. Also went with a more agressive lowering of the
chances of precipitation for late tonight. Blank

&&

.PREV DISCUSSION...
/ISSUED 910 PM MDT Wed Jul 23 2014/
Update forthcoming. Have made minor adjustments to the POP and
Weather grids. Severe Thunderstorm Watch in effect until 3 AM for a
portion of North Central Montana. Radar indicates greatest
concentration of storms near Great Falls at this time. Storm
development over southwest Montana looks to be decreasing.
Temperatures look good.

&&

.PREV DISCUSSION...
/Issued 303 PM MDT Wed Jul 23 2014/

This Afternoon through Friday Evening...Quiet weather right now
across the region, but conditions still looking favorable for
strong-to-severe storms later this aftn/eve, mainly over the central
and Hiline counties.  Weather balloon launched at 1:30pm from Great
Falls indicated just a small piece of stable air (or "cap")
remaining from the stable airmass brought on by the rainfall this
morning.  The cap should erode over the next hour or so as surface
temperatures climb to near 90 degrees.  Once the cap breaks, high
amounts of instability (CAPE values over 1000 J/kg) should allow for
quick initial storm development, with the updrafts straightened by
good vertical wind shear already in place.  Further support should
come from the strong jet stream (80-100 mph) current oriented
southwest-to-northeast from the central Idaho into the center of
Montana.  Primary threats from these storms continues to be large
hail and damaging winds.  Still think storms will initially fire
over parts of southwest MT (Helena area and south), then track
northeastward into central MT this evening and up to the Hiline
during mid-late evening.  A few strong storms may occur north of US
Highway 2 after midnight, but most of serious convective activity
should dissipate by 10pm or so.

The weather system driving the activity is a large low pressure
system currently just off the WA/OR coast.  Forecast models still in
good agreement that the system`s central low pressure area will lift
northeast toward southern British Columbia tonight then track east
just north of the US/Can border on Thursday.  Forecast pressure
gradients remain strong both aloft and with the surface cold front
that should move across the region tomorrow morning, so widespread
gusty winds are still likely over the northern half of the forecast
area.  As such, the high wind warning for areas from Toole County
west to the Northern Rocky Mtn Front remains in effect starting late
tonight.  As the system heads into Saskatchewan on Fri, the
gradients should lessen, along with the winds. High pressure then
steadily builds into the region from the west, bringing dry
conditions and temperatures slightly below normal (mid-upper 70s)
for Friday.
Waranauskas


Friday night through Tuesday...Models are still on the same page in
developing a strong upper ridge over the western U.S. over the
weekend which will continue into early next week. Expect dry
conditions through the weekend. By Monday models forecast some
monsoonal moisture over the area as a weak weather disturbance moves
through the strong upper ridge. Models disagree on details with the
the weather disturbance and associated spotty precipitation. Will go
with isolated showers and thunderstorms over southwest Montana
Monday through Tuesday. Models have spotty precipitation farther
north but due to differences with the timing and placement of the
precipitation will hold for now in mentioning any isolated showers
or thunderstorms over central and northern Montana. Blank

.PRELIMINARY POINT TEMPS/POPS...
GTF  52  76  49  80 /  10  10   0   0
CTB  50  72  47  77 /  10  10  10  10
HLN  53  80  52  84 /  10   0   0   0
BZN  43  80  43  82 /  10   0   0   0
WEY  33  72  33  76 /   0   0   0   0
DLN  43  77  45  81 /  10   0   0   0
HVR  52  77  51  81 /  10  10  10  10
LWT  49  77  48  78 /  10  10   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
FIRE WEATHER WATCH from Noon MDT today through this evening
Blaine...Chouteau...Fergus.

HIGH WIND WARNING until Midnight MDT tonight Northern Rocky
Mountain Front.

HIGH WIND WARNING from 6 AM this morning to Midnight MDT tonight
Eastern Glacier...Toole.

&&

$$

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