Hail in Montana, August 26, 2013

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
250 PM MDT MON AUG 26 2013

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH WEDNESDAY...

WATER VAPOR IMAGERY AND 500 MB HEIGHT FIELD REVEALS THE VERY
PERSISTENT BATTLE BETWEEN THE HIGH PRESSURE FROM THE CENTRAL
PLAINS REGION AND THE LOW PRESSURE JUST WEST OF BRITISH COLUMBIA.
BOTH OF THESE SYSTEMS ARE FUNNELING THEIR RESPECTIVE MOISTURE
PLUMES...AND A NEGLIGIBLE DRY SLOT BETWEEN THEM THROUGH THE
NORTHERN ROCKIES AND NORTHERN HIGH PLAINS REGIONS.

A FEW FORECAST CHALLENGES PRESENT THEMSELVES IN THE SHORT TERM.
FIRST...DETERMINISTIC MODELS ARE SHOWING INCONSISTENCIES RUN TO RUN.
ENOUGH TO LESSEN MY CONFIDENCE IN THEM. I HAVE TRIED TO HEDGE MY
BETS WITH THEM BY PAINTING MORE OF AN OCCASIONAL SPRINKLE HERE AND
THERE. SECOND...A SLIGHTLY MORE ORGANIZED PERIOD OF THUNDERSTORMS
SEEM POSSIBLE FOR THE WEDNESDAY AFTERNOON AND EVENING
PERIODS...BUT YET AGAIN...EXACT TIMING AND AMOUNT AND PLACEMENT IS
STILL UNCERTAIN THANKS TO REPEATED MODEL DISAGREEMENTS. FOR
EXAMPLE...THE GFS WANTS TO KEEP OUR CWA ALMOST ENTIRELY ALL DRY
WHILE THE EC...NAM...AND SREF ARE GOING WITH A MUCH WETTER
SOLUTION. THIS ALL OBVIOUSLY DEPENDS ON THE WAXING AND WANING
STRENGTH OF A SHORT WAVE DISTURBANCE PROGGED TO MOVE OVER US
WITHIN THE SOUTHWESTERLY FLOW ALOFT.

TEMPERATURES WILL REMAIN 10 TO 15 DEGREES ABOVE NORMAL WITH
DAYTIME HIGH REACHING WELL THROUGH THE 90S THANKS TO THE STRONG
INFLUENCE OF THE HIGH PRESSURE SYSTEM OVER THE CENTRAL PLAINS
REGION. BMICKELSON

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...
THE VERY PERSISTENT SYNOPTIC PATTERN OF A STRONG BROAD HIGH OVER
THE CENTRAL AND SOUTH-CENTRAL PRAIRIE WILL CONTINUE INTO THE
EXTENDED PERIOD. AN UPPER LEVEL TROUGH OFF THE WEST COAST WILL
KEEP PUMPING PACIFIC MOISTURE INTO THE SOUTHWEST FLOW ALOFT. THIS
FLOW WILL FIND A VERY WARM NORTHEAST MONTANA. A SURFACE TROUGH IN
THE LEE OF THE ROCKY MOUNTAINS WILL PROVIDE AN UNSTABLE
ENVIRONMENT...RESULTING IN ISOLATED TO SCATTERED THUNDERSTORMS.
CHANCES FOR STORMS WILL IMPROVE SLIGHTLY FRIDAY NIGHT AS AN UPPER
DISTURBANCE IN CANADA SENDS A FRAGMENTED COLD FRONT SOUTH OVER
NEMONT. THE RIDGE WILL REESTABLISH ITSELF FOR THE WEEKEND AS A
STRONG STORM SYSTEM LURKS OFF THE PAC-NW COAST AND SQUEEZES UP THE
RIDGE OVER MONTANA.

THE QUESTION ASKED IS WHEN WILL THIS MAIN PATTERN BREAK. WHAT
HAPPENS FOR THE BEGINNING OF NEXT WEEK...JUST BEYOND THE
EXTENDED PERIOD...BECOMES MORE MURKY. THERE ARE HINTS...AS
FOLLOWS. THE 12Z GFS PLOWS THAT STORMS SYSTEM INTO THE INTER-
MOUNTAIN WEST...SENDING A COLD FRONT AND LOTS OF MOISTURE OUR WAY
AROUND MONDAY. THE 00Z EC ON THE OTHER HAND DOES NOT SEEM TO HAVE
THE STRENGTH TO KNOCK OUR RIDGE DOWN. THE 12Z EC CAME IN LATE
BUT IT DOES NOT MUCH CHANGE IN HOW IT TREATS THE NORTHWEST LOW.
THAT QUESTION WILL REMAIN UNTIL THERE IS MORE MODEL AGREEMENT AS
THE TIME PERIOD BECOMES CLOSER. NO CHANGES WERE MADE LATE IN THE
PERIOD. SCT

PREVIOUS DISCUSSION...
HOT AND MAINLY DRY WEATHER CONTINUES AS UPPER RIDGE OVER THE
CENTRAL CONUS AND TROF OFF THE WEST COAST DOMINATES THE PATTERN
FOR MOST OF THE EXTENDED PERIOD. MODELS HAVE BACKED OFF ON
POTENTIAL PATTERN SHIFT WITH BREAK DOWN OF THE RIDGE NEXT WEEKEND.
CURRENT MEDIUM RANGE MODELS TRENDING TOWARD A SLIGHT LOWERING OF
HEIGHTS ACROSS THE NORTHERN PLAINS AS THE WEST COAST TROF DEVELOPS
INTO A CLOSED LOW OFF OR OVER THE PACIFIC NORTHWARD.

THROUGH THE END OF THE WEEK SOUTHWEST FLOW INTO MONTANA WILL
CONTINUE TO PUMP VERY HOT AIR NORTHWARD RESULTING IN WELL ABOVE
NORMAL TEMPERATURES. MOISTURE AVAILABILITY CONTINUES TO BE
DEPENDENT ON THE PROXIMITY OF MONSOONAL PLUME...AND LACK UPPER
IMPULSES WILL LIMIT CONVECTIVE DEVELOPMENT. EXCEPTION WILL MAINLY
BE LATE WEDNESDAY WHEN A WEAK SHORTWAVE LIFTS ACROSS THE STATE.
AFTER THAT THE FOCUS WILL SHIFT TO THE WEEKEND WITH SHORTWAVES
EJECTING OUT OF THE PACIFIC TROF. HOWEVER GIVEN THE DAILY CHANGES
TO THE MODEL SOLUTIONS...CONFIDENCE IS VERY LOW FOR ANY PARTICULAR
SOLUTION. EBERT

&&

.AVIATION...
VFR.

HIGH PRESSURE OVER THE CENTRAL AND SOUTHERN PRAIRIE WILL MAINTAIN
A SOUTHWEST FLOW ALOFT OVER NORTHEAST MONTANA THROUGH THE TAF
PERIOD. UNSTABLE SURFACE CONDITIONS COULD RESULT IN ISOLATED
THUNDERSTORMS TONIGHT AND TUESDAY.

EXPECT WIND TO BECOME LIGHT AND VARIABLE TONIGHT AND TUESDAY.

SCT

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

WEATHER.GOV/GLASGOW

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GLASGOW MT
329 PM MDT MON AUG 26 2013

MTZ019-262230-
SHERIDAN-
329 PM MDT MON AUG 26 2013

THE NATIONAL WEATHER SERVICE IN GLASGOW HAS ISSUED A

SIGNIFICANT WEATHER ADVISORY FOR...
  NORTHWESTERN SHERIDAN COUNTY IN NORTHEAST MONTANA...

UNTIL 430 PM MDT.

AT 327 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 6 MILES NORTH OF REDSTONE...MOVING EAST AT 15
MPH.

HAIL UP TO ONE-HALF INCH IN DIAMETER IS EXPECTED WITH THIS STORM...
ALONG WITH HEAVY RAIN AND FREQUENT DANGEROUS LIGHTNING.

LOCATIONS IN THE ADVISORY INCLUDE...
   REDSTONE...

IF THREATENING WEATHER APPROACHES YOUR AREA...TAKE SHELTER IN A
STURDY BUILDING.

LAT...LON 4870 10446 4872 10503 4885 10504 4891 10504
      4892 10505 4900 10506 4900 10448
TIME...MOT...LOC 2129Z 270DEG 12KT 4891 10498

GFF
WEATHER.GOV/GLASGOW