Hail and Damaging Winds in Montana, August 24, 2006

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
248 AM MDT THU AUG 24 2006

.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH SATURDAY...
THE COLD FRONT THAT PASSED THROUGH THE FORECAST AREA THIS MORNING
WILL HAVE MOVED ON BEFORE NOON. EXPECT GUSTY NORTHWEST WINDS TO
FOLLOW THE FRONT DURING THE MORNING THEN DIMINISH DURING THE
EARLY EVENING. EXPECT GOOD COUPLING OF UPPER WINDS TO THE SURFACE
SO WILL GO AHEAD AND SET LAKE WIND ADVISORY STARTING MID MORNING
AND GO UNTIL SUNSET. EASTERN ZONES THIS MORNING A BIT UNSTABLE
WITH SHORTWAVE DISTURBANCE MOVING THROUGH SO WILL KEEP SLIGHT
CHANCE POPS IN THROUGH NOON...THEN DIMINISH FROM THE WEST THROUGH
AFTERNOON AND EVENING. TODAY MAIN UPPER LEVEL TROUGH ENERGY AND
AREAS OF INSTABILITY MOVE INTO CANADA...NORTH DAKOTA AND POSSIBLY
EASTERN ZONES BY AFTERNOON. ATMOSPHERE VERY UNSTABLE JUST OVER THE
BORDER IN NORTH DAKOTA TODAY. SOME OF THAT INSTABILITY COULD BACK
INTO THE EASTERN ZONES. COOLER TEMPERATURES AND HIGHER RELATIVE
HUMIDITIES ARE EXPECTED TODAY WITH HIGHS TO BE SEASONAL. SURFACE
LOW WILL MOVE OFF TO THE SOUTHEAST FOR NORTHWEST WINDS OVER THE
AREA TODAY...THEN VEERING NORTH BY LATE EVENING.

ANOTHER UPPER SHORTWAVE TROUGH APPROACHING THE NORTHERN ROCKIES
WILL SLOWLY MOVE SOUTH OF EAST...BUT TAKE MOST MOISTURE AND ENERGY
SOUTH OF THE AREA FRIDAY AND SATURDAY. HOWEVER WITH AREA UNDER AN
UPPER TROUGH...SMALL CHANCES FOR CONVECTION CONTINUE THROUGH THE
SHORT TERM. HOWEVER LIKELIHOOD FOR PRECIPITATION FALLS LESS THAN
SLIGHT CHANCE BEGINNING FRIDAY EVENING AND CONTINUES THROUGH
SATURDAY. MAXIMUM TEMPERATURES WILL DROP EVEN FURTHER ON FRIDAY
WITH HIGHS SLIGHTLY BELOW SEASONAL NORMS.

SATURDAY WILL SEE CLOUD COVER DECREASING AND THICKNESS VALUES BEGIN
TO RISE AGAIN WITH QUASI-ZONAL FLOW...SO WILL SEE A SLIGHT
RECOVERY OF TEMPERATURES WITH HIGHS AGAIN APPROACHING SEASONAL
NORMS. SCT

.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY...
MEDIUM RANGE MODELS APPEARED TO BE IN DECENT AGREEMENT THROUGH THE
PERIOD. CWA STARTS OUT BETWEEN TWO SYSTEMS SATURDAY NIGHT (ONE TO
OUR NORTH...THE OTHER TO OUR SOUTH) WITH BOTH MOVING EAST. 500 MB
HEIGHTS THEN BEGIN RISING A BIT AS UPPER RIDGE MOVES INTO MONTANA
BY MONDAY. A SYSTEM THEN IS PROGGED TO MOVE THROUGH THE GULF OF
ALASKA AND ONTO THE BRITISH COLUMBIA COAST BY TUESDAY. THIS SHOULD
HELP TO PUSH THE RIDGE INTO THE PLAINS BY MIDWEEK. SOUTHWEST FLOW
ALOFT HELPS TO DEVELOP A SURFACE LOW OVER EASTERN MONTANA BUT MUCH
OF THE MOISTURE AND DYNAMICS REMAIN TO THE NORTHWEST UNDER THE
UPPER TROUGH. THIS MEANS THAT CONDITIONS LOOK TO BE HOT AND DRY
BEGINNING LATE MONDAY AND LASTING PROBABLY INTO THURSDAY. RAISED
MAX TEMPERATURES DURING THIS PERIOD AS 90S A POSSIBILITY FOR MANY
AREAS BY TUESDAY. RELATIVE HUMIDITIES LOOK LOW BUT WINDS LOOK
LIGHT SO FIRE WEATHER DOES NOT APPEAR TO BE A PROBLEM AT THE
MOMENT.

UPPER TROUGH PASSAGE DOES NOT LOOK CLEAR AS MODELS CONTINUE TO
DELAY IT/S ARRIVAL. ECMWF LOOKS REASONABLE WITH TIMING NOT TILL
NEXT WEEKEND. -TFJ

&&

.AVIATION...
UNSETTLED CONDITIONS EXPECTED THE NEXT 12 TO 18 HOURS...ESPECIALLY
AT KSDY AND KGDV. SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED
TO AFFECT VISIBILITIES AND CEILINGS...BUT MVFR CONDITIONS ARE NOT
EXPECTED. NORTHWEST WINDS ARE EXPECTED TO BE BREEZY AT ALL
LOCATIONS BY THIS AFTERNOON. -TFJ

&&

.FIRE WEATHER...
THERE WILL BE A WIND SHIFT THIS MORNING WITH THE PASSING OF A SURFACE
COLD FRONT. WIND SHOULD GO NORTHWEST MOST LOCATIONS. GENERALLY
EXPECTING 15 TO 25 MPH WITH SOME GUSTS IN THE 30S BRIEFLY WITH THE
PASSAGE OF THE FRONT...THEN A BIT OF A DECREASE BEFORE THEY
INCREASE AGAIN LATER THURSDAY MORNING AS THE UPPER TROF COMES
THRU. SOME SHOWERS OF THUNDERSTORMS ARE POSSIBLE...BUT A LOT OF
RAINFALL IS NOT ANTICIPATED AND THE CHANCES OF A WETTING RAIN ARE
NOT VERY HIGH. WHEN WIND SHIFT OCCURS RELATIVE HUMIDITIES SHOULD
AT LEAST BE ABOVE 30 TO 50 PERCENT AND LIGHTNING ACTIVITY SHOULD
BE MINIMAL. TEMPERATURES WILL BE SIGNIFICANTLY COOLER OVER THE
NEXT FEW DAYS. MINIMUM RH VALUES SHOULD RANGE FROM 25 PERCENT IN
THE SOUTHWEST ZONES TO ABOUT 40 PERCENT IN THE NORTHEAST ZONES.
THEREFORE DO NOT PLAN FOR ANY HEADLINES TODAY. SCT

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY FROM 9 AM THIS MORNING TO 8 PM MDT THIS
EVENING FOR FORT PECK LAKE.

&&

WEATHER.GOV/GLASGOW