Flash Flooding in Montana, March 15, 2003

NORTHEAST MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
238 AM MST SAT MAR 15 2003

.SHORT TERM...SATURDAY THRU MONDAY
SHORTWAVE MOVING THROUGH EASTERN MONTANA BRINGING SOME SHOWERS TO
THE SE PART OF THE FORECAST AREA. THIS WAVE WILL EXIT MONTANA BY
15Z. SW FLOW ALOFT WILL CONTINUE ACROSS MONTANA OVER THE WEEKEND
WITH CLOSED LOW OVER THE GULF OF ALASKA AND UPPER RIDGE TO THE
EAST.

A SHORTWAVE RIDGE IN THE SW FLOW WILL MOVE ACROSS EASTERN MONTANA
THIS AFTERNOON AND EVENING BRINGING ANOTHER WARM DAY. THEN A COMPLEX
WEATHER PATTERN STARTS DEVELOPING TONIGHT AS A SHORTWAVE MOVES
ACROSS CALIFORNIA AND NEVADA AND A SURFACE LOW MOVES INTO MONTANA
FROM THE WEST. WHILE THE MODELS WEAKEN THE MONTANA SURFACE LOW ON
SUNDAY...ANOTHER LOW DEVELOPS OVER THE CENTRAL PLAINS. AN UPPER
TROUGH STARTS DIGGING OVER THE CENTRAL ROCKIES SUNDAY NIGHT AND
BECOMES A CLOSED LOW ON MONDAY. MEANWHILE...AN INVERTED SURFACE
TROUGH EXTENDS FROM THE CENTRAL PLAINS SURFACE LOW INTO EASTERN
MONTANA.

THIS INVERTED TROUGH BECOMES THE FOCUS OF PRECIPITATION FOR EASTERN
MONTANA SUNDAY NIGHT AND MONDAY. VERY STRONG LIFT WITH PLENTY OF
MOISTURE...ESPECIALLY ON MONDAY. EXPECT PRECIPITATION TO START OUT
AS RAIN. HOWEVER...THE COMBINATION OF DYNAMIC COOLING AND COLD AIR
ADVECTION WILL EVENTUALLY CHANGE THE PRECIP TO SNOW...MOST LIKELY ON
MONDAY. WILL HAVE CHANCE POPS SUNDAY NIGHT AS ETA AND GFS DIFFER ON
TIMING OF THE PRECIPITATION DEVELOPING FOLLOWED BY RAIN AND SNOW
LIKELY ON MONDAY. THE EXCEPTION IS THE WESTERN ZONES WHICH WILL BE
ON THE FRINGES OF THE PRECIP BAND...WILL FORECAST A CHANCE POPS
THERE. IF QPF IS ANYWHERE NEAR THE GFS FORECAST IN FUTURE MODEL
RUNS...A WINTER STORM WATCH MAY BE NEEDED FOR MONDAY. WILL ISSUE A
SPS HIGHLIGHTING THE POSSIBILITY OF HEAVY SNOW MONDAY AND TUESDAY.
FORRESTER

.LONG TERM...MONDAY NIGHT THROUGH FRIDAY
DEEPENING LOW OVER THE CENTRAL PLAINS MONDAY NIGHT INTO TUESDAY
LOOKED TO FAR TO OUR EAST AND TOO PROGRESSIVE YESTERDAY TO PRODUCE
ANY PRECIPITATION IN NE MONTANA.  MODELS NOW LOOK TO BE IN DECENT
AGREEMENT AND ARE SLOWER AND FURTHER WEST.  PRECIPITATION (POSSIBLY
HEAVY) LOOKS TO BE A THREAT ACROSS NE MONTANA.  AVN IS WETTER AND
WARMER THAN THE ETA...AND THE CANADIAN LOOKS TO BE IN REASONABLE
AGREEMENT WITH THE AVN.  WILL BE MAKING SOME BIG CHANGES TO THE
GRIDS THIS MORNING AND WILL BE GOING WITH LIKELY POPS MONDAY NIGHT
INTO TUESDAY FOR WRAP AROUND PRECIPITATION.  WILL INCLUDE A BUFFER
ZONE OF CHANCE POPS IN OUR WESTERN ZONES WHERE PRECIP CHANCES LOOK
TO BE A LITTLE LOWER.  ALSO PLANNING TO LOWER TEMPERATURES QUITE A
BIT WITH THE ADDITION OF PRECIP TO THE FCST.  ALTHOUGH THERE IS NO
REAL SOURCE OF COLD AIR...THE STORM IS DYNAMIC ENOUGH TO GENERATE
ENOUGH LIFT AND COOLING THAT A HEAVY WET SNOW IS POSSIBLE.  GFS
ACTUALLY RETROGRADES THE SYSTEM BACK TO THE WEST INTO EASTERN
NEBRASKA WEDNESDAY.  I WILL KEEP CHANCE POPS GOING INTO THE DAY
WEDNESDAY...ALTHOUGH WILL TAPER BACK POPS FROM WEST TO EAST DURING
THE DAY.  SYSTEM LOOKS TO LIFT OUT THURSDAY AS THE NEXT TROUGH
BEGINS TO MOVE INTO THE WEST COAST.  WILL DRY IT OUT WEDNESDAY NIGHT
AND GO WITH A DRY AND SEASONABLE DAY THURSDAY (ALTHOUGH TEMPERATURE
COULD NEED TO BE LOWERED IF WE GET MAJOR SNOWSTORM).  UPPER TROUGH
WEAKENS AS IT MOVES THROUGH FRIDAY AND WILL NOT MAKE ANY CHANGES TO
INHERITED FORECAST WHICH HAS A CHANCE OF RAIN OR SNOW SHOWERS.  CB

KGGW BWO /054 032/051 031/045 79003366
     SSEW 027/035 024/034 026/040 025/042 024/ 9265300030
KGDV BWO /057 034/053 032/043 79003466
     SSEW 027/036 026/035 025/040 024/042 023/ 9265430030

.GGW...NONE.

MTZ016>027-059>062-161300-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GLASGOW MT
554 AM MST SAT MAR 15 2003

.DAY ONE...

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...

A WINTER STORM IS EXPECTED TO DEVELOP OVER THE NORTHERN PLAINS ON
MONDAY AND REMAIN IN THE AREA THROUGH TUESDAY NIGHT. THE
PRECIPITATION IS FORECASTED TO BEGIN AS A MIX OF RAIN AND SNOW
EITHER SUNDAY NIGHT OR MONDAY AND CHANGE TO ALL SNOW BY MONDAY
NIGHT. LOOK FOR THE SNOW TO CONTINUE INTO WEDNESDAY MORNING BEFORE
DIMINISHING. THE BEST CHANCE FOR HEAVY SNOW FROM THIS STORM WILL BE
EAST OF GLASGOW AND JORDAN.

THE TRACK OF THIS STORM IS UNCERTAIN AT THIS TIME. STAY TUNED TO
NOAA WEATHER RADIO AND OTHER LOCAL MEDIA OUTLETS FOR FURTHER DETAILS
OR UPDATES ON THIS POTENTIAL WINTER STORM.

.SPOTTER INFORMATION STATEMENT...

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

CB

MTZ016>027-059>062-152200-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GLASGOW MT
310 AM MST SAT MAR 15 2003

...HEAVY SNOW POSSIBLE FOR NORTHEAST MONTANA MONDAY AND TUESDAY...

AFTER A FEW WARM DAYS WITH MELTING SNOW...A WINTER STORM IS EXPECTED
TO DEVELOP OVER THE NORTHERN PLAINS ON MONDAY AND REMAIN IN THE AREA
THROUGH TUESDAY NIGHT. THE PRECIPITATION IS FORECASTED TO BEGIN AS A
MIX OF RAIN AND SNOW EITHER SUNDAY NIGHT OR MONDAY AND CHANGE TO ALL
SNOW BY MONDAY NIGHT. LOOK FOR THE SNOW TO CONTINUE INTO WEDNESDAY
MORNING BEFORE DIMINISHING. THE BEST CHANCE FOR HEAVY SNOW FROM THIS
STORM WILL BE EAST OF GLASGOW AND JORDAN.

THE TRACK OF THIS STORM IS UNCERTAIN AT THIS TIME. STAY TUNED TO
NOAA WEATHER RADIO AND OTHER LOCAL MEDIA OUTLETS FOR FURTHER DETAILS
OR UPDATES ON THIS POTENTIAL WINTER STORM.

FORRESTER