367 
FXUS65 KTFX 150313
AFDTFX

SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
915 PM MDT MON APR 14 2003

WILL UPDATE ZONES AND STATE FORECAST

.SHORT TERM...SIGNIFICANT UPDATES NEEDED FOR TONIGHTS FORECAST. UPPER
LEVEL TROUGH OVER THE WEST COAST ROTATES INLAND TONIGHT...BECOMING
NEGATIVELY TILTED FROM BRITISH COLUMBIA TO THE CENTRAL ROCKIES BY
TUESDAY AFTERNOON. WATER VAPOR IS SHOWING AN IMPRESSIVE PLUME OF
PACIFIC MOISTURE EXTENDING FROM SOUTHERN CALIFORNIA ALL THE UP TO
WESTERN MONTANA. THIS PLUME WILL SURGE OVER THE STATE AS THE UPPER
TROUGH CONTINUES TO DIG. A BROAD AREA OF SURFACE LOW PRESSURE
CURRENTLY EXTENDING FROM THE SOUTHERN GREAT BASIN INTO WYOMING AND
THE CENTRAL PLAINS WILL STRENGTHEN OVER THE NEXT 24 HOURS. BY TUESDAY
EVENING A STRONG SPRING STORM WILL BE CENTERED OVER THE COLORADO-
NEBRASKA BORDER WITH A LOW PRESSURE TROUGH EXTENDING NORTHWEST INTO
CENTRAL MONTANA. MODELS ARE SHOWING A POTENT COMBINATION OF SURFACE
MOISTURE CONVERGENCE...UPPER LEVEL DIVERGENCE AND MOIST ISENTROPIC
LIFT OVER LARGE PORTIONS OF CENTRAL AND SOUTHWEST MONTANA. THE NO-
BRAINER IS THAT THERE WILL BE SIGNIFICANT PRECIPITATION BEGINNING
LATE TONIGHT AND CONTINUING THROUGH TUESDAY NIGHT. THE HARD PART AT
THIS POINT IS DETERMINING HOW LOW SNOW LEVELS WILL GO AND HOW MUCH
WILL STICK TO THE GROUND. ANALYSIS OF BUFKIT FORECAST SOUNDINGS
INDICATES THAT SNOW WILL REACH VALLEY FLOORS IN SOUTHWEST MONTANA.
TEMPERATURES WILL BE WARMER OVER THE PLAINS...BELIEVE ISLAND RANGE
MOUNTAINS WILL RECEIVE IMPRESSIVE SNOW AMOUNTS...BUT LOWER
ELEVATIONS WILL LIKELY SEE MOSTLY RAIN. HAVE DECIDED TO ISSUE A
WINTER STORM WARNING FOR MY FAR SOUTHWEST ZONES BEGINNING TONIGHT
AND CONTINUING THROUGH TUESDAY. FURTHER NORTH WILL ISSUE A WARNING
ONLY FOR THE MOUNTAINS ABOVE 5000 FEET. WILL KEEP THE FLOOD WATCH IN
PLACE FOR THE CAVE GULCH BURN AREA AND WILL LET SUBSEQUENT SHIFTS
DECIDE IF A WARNING IS NEEDED. MPJ

.EXTENDED...NO SIGNIFICANT CHANGES TO THE EXTENDED FORECAST.
GENERALLY DRY WESTERLY FLOW ALOFT FRIDAY AND SATURDAY WITH ANY
PRECIPITATION CONFINED TO THE MOUNTAINS. INCREASING BACKING FLOW
ALOFT SUNDAY AS AN UPPER TROF MOVES ONSHORE THE WEST COAST. WILL
INTRODUCE CHANCE POPS FOR MONDAY AS SOUTHWEST FLOW ALOFT STRENGTHENS
AND CONVECTIVE SHOWERS BECOME A POSSIBILITY.

.CCF NUMBERS
GTF OB 033/042 030/050 031 17698
    BBBBB 054/032 055/034 055/039 055/034 053 20200000003
CTB EB 031/043 028/048 028 17343
    BBBBB 050/029 054/031 053/036 053/031 051 20200000003
HLN OB 037/045 031/053 029 17397
    BBBBB 056/030 055/032 058/037 058/034 056 10200000003
BZN OB 033/042 030/051 028 17897
    BBBBB 054/029 055/031 057/036 057/033 055 00200000003
WEY SB 028/038 021/040 021 17+94
    BBBBB 046/022 048/024 048/029 048/027 046 02233002224
DLN SB 032/046 027/051 026 17664
    BBBBB 052/027 055/029 053/034 052/031 050 01200000003
HVR OB 034/043 030/048 030 17398
    BBBBB 055/031 054/033 057/036 056/035 054 20100000003
LWT OB 033/037 028/044 029 17698
    BBBBB 052/030 053/032 054/037 054/034 052 20100000003

.TFX...WINTER STORM WARNING LATE TONIGHT THROUGH TUESDAY FOR
       BROADWATER...MEAGHER...BEAVERHEAD...MADISON AND GALLATIN
       COUNTIES.
    ...WINTER STORM WARNING ABOVE 5000 FEET TUESDAY FOR CASCADE...
       JUDITH BASIN...FERGUS AND CHOUTEAU COUNTIES.
    ...FLOOD WATCH CONTINUES FOR THE CAVE GULCH BURN AREA.

$$