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000
FXUS65 KTFX 222113
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
313 PM MDT Wed May 22 2013

.DISCUSSION...

Tonight through Friday...The airmass is slightly unstable and some
good shear is available from Southwest Montana up towards Lewis and
Clark county. Scattered showers and thunderstorms are expected into
early evening. The main threat from these thunderstorms are strong
winds...hail should remain small. A closed upper level low will
rotate over the Pacific Northwest tonight and bring a period of
widespread precipitation centered over the Northern Rockies through
Friday morning. A jet will move through the flow aloft and develop
strong diffluence over central and north central Montana tonight
into Thursday morning. Snow levels show most of the snow to be above
6000 feet and the current watch will be changed to a winter weather
advisory. Elsewhere, all but the northwest zones will be slightly
unstable Thursday and the extreme southwest zones will be the most
unstable. The jet aloft will move across the zones again Thursday
afternoon, and the pattern should once again develop strong
diffluence over the zones. Winds will switch from the southeast to
southwest Thursday night and hasten the end of precip east of the
Rockies Friday...although higher elevations along the Divide will
remain very moist.  Zelzer

&&

.AVIATION...
UPDATED 1800Z.
VFR conditions prevail with the exception of MVFR conditions from
KLWT to KHVR that will slowly lift this afternoon. The airmass will
become unstable after 21z with scattered showers and thunderstorms
developing first over Southwest Montana before spreading north and
east during the afternoon and early evening. Best chance for
thunderstorms will be from West Yellowstone to Helena and south.
East to southeast surface winds will remain gusty through this
evening. Expect more widespread steady rain to move into the region
through the night with most impact along the terrain of the
Continental Divide. Widespread terrain obscuration due to low
ceilings and precipitation is expected after 00z and will continue
through the 24 hour TAF period. Widespread MVFR conditions will be
possible after 06z with the increase in shower activity.

&&

.HYDROLOGY...Widespread rain and high elevation snow will
develop tonight along the Rocky Mtn Front and continue through
Thursday morning with additional precipitation expected Thursday
and Thursday night. Heaviest precipitation is expected late
tonight through Thursday morning with precipitation amounts
locally exceeding an inch along the continental divide. Snow
levels should lower enough to lessen the impact of moderate
precipitation on the remaining mtn snowpack in these areas,
however local streams and rivers could see delayed rises through
the upcoming weekend. Persons living near or planning activities
near the mentioned areas during the holiday weekend should be
alert for rising river levels and increased stream flows.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  41  55  40  64 /  90  70  70  40
CTB  40  54  38  62 / 100 100  70  50
HLN  40  58  39  63 /  80  70  70  40
BZN  42  63  37  66 /  70  60  60  30
WEY  38  61  34  59 /  50  30  40  10
DLN  38  59  35  62 /  70  50  60  30
HVR  49  68  45  69 /  20  60  80  70
LWT  45  63  41  65 /  50  60  90  50

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY from Midnight tonight to Noon MDT Friday
FOR ELEVATIONS ABOVE 5500 FEET FOR Northern Rocky Mountain
Front...Southern Rocky Mountain Front.

&&

$$

weather.gov/greatfalls