000
FXUS65 KTFX 240002
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
600 PM MDT Thu May 23 2013

.DISCUSSION...

Tonight through Saturday...A deep closed low pressure system will 
remain over the Pacific tonight and another shortwave will rotate 
around the low tonight. This will produce good lift across most of 
the forecast area for widespread showers. At lower levels, a surface 
low pressure trof will move into eastern Montana winds will become 
westerly after midnight. This will help dry the airmass across the 
plains Friday as the low pressure system weakens. Elsewhere, low 
level moisture will be available and the airmass will become 
slightly unstable during the afternoon, mainly across Southwest 
Montana. However the airmass will be capped at higher levels and 
thunderstorms should be shallow. Zelzer

Saturday night through Thursday...The period begins with a closed 
upper low quasi-stationary as it fills over southwest Canada. 
Circulation around this feature will continue to bring moisture and 
instability to the area with scattered showers and/or thunderstorms 
remaining a possibility through Sunday. The airmass will remain 
unstable Monday as an upper trof remains over the west coast. 
Diffluent flow aloft will aid in another round of scattered showers 
and thunderstorms. The models begin to diverge with their solutions 
on Tuesday. Though the airmass will remain unstable, drier air will 
move into northern Montana while afternoon showers and thunderstorms 
will continue to develop over southwest Montana. Unsettled and wet 
conditions will continue Wednesday and Thursday as the west coast 
upper trof rotates across the area. Showers and thunderstorms will 
become widespread across the central and northern portions of the 
county warning area. Temperatures will remain above seasonal 
averages through the period. 

&&

.AVIATION...
UPDATED 0000Z.
An upper disturbance will move northeast through the area late 
tonight and Friday morning. Expect showers/rain ahead of the 
disturbance. Most locations will see a period of MVFR ceilings and 
possibly MVFR visibilities in the precipitation though have low 
confidence in how long the MVFR conditions will last. The most 
favored area for seeing at least several hours of MVFR conditions 
will be the plains and in particular the east slopes of the Rocky 
Mountains. Along with the MVFR conditions expect areas of mountain 
obscurement. Conditions will improve to scattered clouds after the 
passage of the upper disturbance and gusty downslope winds will 
develop over the plains. As for thunderstorms there will be a small 
threat at KLWT and KBZN this evening but think the threat is low 
enough that thunderstorms were not mentioned in the tafs. Blank

&&

.HYDROLOGY...Widespread rain and high elevation snow will continue
at times through Friday morning. 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  64  40  68 / 100  30  10  10 
CTB  38  60  35  65 / 100  30  10  10 
HLN  38  63  38  69 /  90  30  10  20 
BZN  34  65  35  72 /  80  50  10  20 
WEY  30  57  33  66 /  40  10   0  10 
DLN  32  61  34  69 /  80  30  10  30 
HVR  47  68  42  73 /  90  60  10  10 
LWT  42  65  39  68 / 100  50  10  20 

&&

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

&&

$$

weather.gov/greatfalls