Winter Storm in Montana, May 22 to 24, 2004

SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MONTANA
845 PM MDT SAT MAY 22 2004

.DISCUSSION...

MINOR UPDATES TO ZONES. NO UPDATE FOR STATE FORECAST PRODUCT.

UPDATE...GOING FORECAST APPEARS TO BE ON TRACK WITH THE LARGE STORM
SYSTEM ROTATING INTO THE NORTHERN ROCKIES OVERNIGHT. NORTHERLY FLOW
AT THE SURFACE AND MOIST SOUTHWEST FLOW ALOFT ARE ALREADY IN PLACE
AND RADAR IS BEGINNING TO FILL IN ACROSS CENTRAL MONTANA. UPDATE
WILL ADDRESS WINDS OVER NORTH CENTRAL MONTANA BEING SLIGHTLY
STRONGER THAN FORECAST AND AN EXPECTED WIND SHIFT AFTER MIDNIGHT
THAT IS NOT MENTIONED IN THE ZONES. MPJ

&&

.PREVIOUS DISCUSSION...

SHORT TERM...MODELS AGREE ON BIG PICTURE BUT DIFFER IN SMALLER
DETAILS. BIG PICTURE IS THAT A LARGE AND POWERFUL UPPER LOW WILL MOVE
THROUGH THE NORTHERN ROCKIES TONIGHT AND SUNDAY BRINGING AMPLE
PRECIPITATION TO THE CWA. THIS STORM IS DYNAMIC ENOUGH TO HELP LOWER
SNOW LEVELS THROUGH ITS OWN COOLING. WITH CONFIDENCE IN THE TRACK OF
THE MAIN LOW...HAVE OPTED TO ISSUE WINTER STORM WARNINGS FOR ROCKY
MOUNTAIN FRONT FOR TONIGHT...THE SOUTHWEST FROM MIDNIGHT TONIGHT
THROUGH SUNDAY AFTERNOON AND FOR JUDITH BASIN AND FERGUS COUNTIES
ABOVE 5000 FEET SUNDAY AFTERNOON THROUGH MIDMORNING MONDAY. UPSLOPE
FROM THE SURFACE THROUGH 700MB WILL HELP WITH SNOW OVER ROCKY
MOUNTAIN FRONT TONIGHT THEN THE MAIN EVENT STARTS IN EARNEST OVER THE
SOUTHWEST AROUND MIDNIGHT WITH APPROACH OF MAIN LOW. SURFACE LOW TO
DEVELOP OVER WYOMING WITH GOOD CONVERGENCE AND ISENTROPIC LIFT ALSO
ENHANCING PRECIPITATION ACROSS SOUTHWEST MT. FINALLY...AS LOW PULLS
EAST AND UPSLOPE BEGINS CRANKING...SNOW WILL FLY ABOVE 5000 FEET OVER
THE LITTLE BELTS AND SNOWY MOUNTAINS OF JUDITH BASIN AND FERGUS
COUNTIES FROM NOON SUNDAY THROUGH 10 AM MONDAY. WIDESPREAD
PRECIPITATION AMOUNTS SHOULD BE GREATER THAN ONE INCH ACROSS MOST OF
CWA WHICH SHOULD PROVIDE ENOUGH RUNOFF TO ACTUALLY REFLECT ON RIVER
GAGES BY MONDAY. SHOWERS TO REMAIN MONDAY WITH CONTINUED WELL BELOW
SEASONAL AVERAGE TEMPERATURES. DITTMANN

MONDAY NIGHT THROUGH SATURDAY...MAIN FORECAST PROBLEMS WILL CONTINUE
TO REVOLVE AROUND THE UPPER LEVEL PATTERN OVER THE WESTERN UNITED
STATES. MODELS CONTINUE TO STRUGGLE WITH THE ENERGY OFF THE
CALIFORNIA COAST. STILL PREFER THE UPPER LEVEL ENERGY TO HANG OFF THE
COAST LONGER THAN THE GFS IS ADVERTISING...WITH THE CANADIAN AND
ECMWF LOOKING REASONABLE. THIS WOULD KEEP MONTANA IN A NORTHWESTERLY
FLOW THROUGH MIDWEEK. EXPECT A DISTURBANCE OR TWO TO RIDE DOWN IN THE
FLOW...SO WILL KEEP LOW POPS GOING THROUGH TUESDAY NIGHT. THINK THE
FLOW WILL THEN BEGIN TO BACK TO MORE WESTERLY BY LATER WEDNESDAY INTO
THURSDAY. WILL THEREFORE CONFINE LOW POPS TO THE WESTERN MOUNTAINS...
ALONG WITH INCREASING WINDS. BY LATER IN THE WEEK...THE OVERALL
PATTERN WILL BECOME MORE PROGRESSIVE...WITH THE ENERGY OFF THE
CALIFORNIA COAST COMING ONSHORE. THIS SHOULD LOWER HEIGHTS OVER THE
WESTERN STATES...PUTTING MONTANA INTO MORE OF A SOUTHWESTERLY FLOW.
WILL THEREFORE INCREASE POPS OVER THE MOUNTAINS FOR THIS PERIOD.
TEMPERATURES THROUGH THE PERIOD WILL GRADUALLY WARM TO NEAR NORMAL
VALUES BY MIDWEEK...WITH NEAR NORMAL TEMPERATURES THEN EXPECTED INTO
SATURDAY. SCHAUMANN

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF WB 037/045 031/049 035 02987
    BBBBB 060/039 066/043 067/043 066/041 066 32210000001
CTB WB 032/042 029/048 034 02975
    BBBBB 058/039 064/041 063/040 063/041 064 322200000--
HLN WE 040/045 035/050 038 02+95
    BBBBB 062/042 067/046 068/046 067/045 067 3221-112211
BZN WB 037/043 034/049 032 02+98
    BBBBB 059/035 063/038 064/039 064/039 064 3221-101211
WEY JB 029/037 027/044 023 02986
    BBBBB 049/026 052/029 055/029 053/028 052 32212211211
DLN WE 035/043 032/050 032 02+94
    BBBBB 060/038 066/040 065/040 062/039 063 32111221111
HVR WB 040/047 033/053 038 02986
    BBBBB 062/040 068/044 070/044 067/044 068 22220000000
LWT WE 037/045 033/046 032 02898
    BBBBB 058/037 062/040 064/040 063/040 062 3222000000-

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING TONIGHT FOR ENTIRE ROCKY MOUNTAIN FRONT.
WINTER STORM WARNING MIDNIGHT TONIGHT THROUGH SUNDAY AFTERNOON
FOR ALL OF SOUTHWEST MONTANA.
WINTER STORM WARNING ABOVE 5000 FEET FROM NOON SUNDAY THROUGH 10 AM
MONDAY FOR JUDITH BASIN AND FERGUS COUNTIES.

&&

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE GREAT FALLS MT
1248 PM MDT SAT MAY 22 2004

MTZ008>015-044>055-231110-
BEAVERHEAD-NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER-HILL-CASCADE-
CHOUTEAU-CENTRAL AND SOUTHERN LEWIS AND CLARK-MADISON-TOOLE-
LIBERTY-EASTERN PONDERA-BLAINE-SOUTHERN ROCKY MOUNTAIN FRONT-
EASTERN TETON-JUDITH BASIN-FERGUS-JEFFERSON-BROADWATER-MEAGHER-
GALLATIN-
1248 PM MDT SAT MAY 22 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL AND SOUTHWEST MONTANA

.DAY ONE...TODAY

A WINTER STORM WARNING HAS BEEN ISSUED FOR THE ROCKY MOUNTAIN FRONT
FOR TONIGHT...AND SOUTHWESTERN MONTANA FOR LATE TONIGHT. PLEASE REFER
TO GTFWSWTFX FOR FURTHER DETAILS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

A WINTER STORM WARNING HAS BEEN ISSUED FOR THE ROCKY MOUNTAIN FRONT
THROUGH 6 AM SUNDAY...FOR SOUTHWEST MONTANA ON SUNDAY...AND CENTRAL
MONTANA ABOVE 5000 FEET FOR SUNDAY. PLEASE REFER TO GTFWSWTFX FOR
FURTHER DETAILS.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.