Hail in Montana, May 19, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
213 PM MDT SAT MAY 19 2007

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH MONDAY...
WATER VAPOR CONTINUING TO SHOW UPPER TROUGH PUSHING INTO BRITISH
COLUMBIA AND THE PACIFIC NORTHWEST THIS AFTERNOON. THIS HAS HELPED
TO TOUCH OFF THUNDERSTORMS OVER NW WY NORTH INTO SOUTHERN ALBERTA.
LAPS DATA CONTINUING TO SHOW ATMOSPHERE DESTABILIZING MAINLY OVER
CENTRAL AND SOUTH-CENTRAL MONTANA WHILE A VERY COOL AIRMASS IS
KEEPING THINGS MORE STABLE NORTH AND EAST.

THUNDERSTORMS ARE THE MAIN THREAT THIS EVENING WITH MUCH OF THEM
BEING HELPED ALONG BY LIFT AT THE MID LEVELS. SURFACE-BASED
CONVECTION IS EXPECTED TO MAINLY REMAIN SOUTH OF THE CWA WITH
ELEVATED ELEMENTS HELPING THINGS OUT IN OUR AREA. RIGHT NOW KEPT
SEVERE MENTION IN THE SW ZONES...WHICH INCLUDES SW PHILLIPS GARFIELD
AND PETROLEUM COUNTIES.

SUNDAY AND SUNDAY NIGHT...THE UPPER TROUGH AXIS MOVES ONTO THE
PACIFIC NORTHWEST COAST SO ANOTHER UNSETTLED DAY IS EXPECTED.
HOWEVER THE MODELS ARE EXPECTING COLDER AIR TO SETTLE INTO WESTERN
AND NORTH-CENTRAL MONTANA WITH A SURFACE LOW TO SETTLE NEAR NE WY
WITH A SURFACE TROUGH TO EXTEND NORTH INTO THE EASTERN ZONES. SPC/S
EXPANSION OF A SLIGHT RISK INTO THE SOUTHEASTERN ZONES LOOKS GOOD AS
THIS TYPE OF PATTERN CAN PRODUCE STORMS WITH GOOD HAIL. CAPES LOOK
TO POOL IN THIS AREA WITH VALUES REACHING 2000 J/KG. ACTIVITY
DOESN/T LOOK TO DIMINISH ALL THAT QUICK DURING THE EVENING AS A
NORTHERN PLAINS RIDGE WILL BE HOLDING TOUGH.

ON MONDAY...SURFACE LOW EVENTUALLY MOVES EAST INTO THE DAKOTAS AS
THE UPPER TROUGH AXIS SWINGS INTO THE ROCKIES. THIS WILL PROVIDE A
COOLER DAY TO THE AREA...BUT HOW MUCH IS DEPENDENT ON AMOUNT OF
CLOUDINESS AND PRECIPITATION. RIGHT NOW IT LOOKS LIKE THE BEST
CHANCE OF SHOWERS WILL BE CLOSE TO THE UPSLOPE AREAS IN
SOUTH-CENTRAL MONTANA. MAYBE PEEKS OF SUN OVER NORTHEAST MONTANA
WHICH MAY ALLOW TEMPS TO REACH THE LOWER TO MID 60S. JAMBA

.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...
RECENT ECMWF AND GFS IN REASONABLE AGREEMENT WITH UPPER LOW TRACK
ACROSS THE REGION EARLY IN THE PERIOD. INCREASED SKY AND POPS A
TAD OVER SOUTHEASTERN ZONES TUESDAY INTO EARLY WEDNESDAY FOR THIS
FEATURE. ECMWF OPENS THIS LOW UP AND BECOMES MORE PROGRESSIVE BY
MID-WEEK WHEREAS THE GFS MAINTAINS A SLOW-MOVING UPPER LOW. LOW
CONFIDENCE REMAINS UNCHANGED WITH ANY SOLUTION AT THE
MOMENT...INCLUDING ENSEMBLES...SO NO FURTHER CHANGES WARRANTED AT
THE MOMENT. MCZ

PREVIOUS LONG TERM DISCUSSION...
AN UPPER LOW NOW SEVERAL HUNDRED MILES OFF THE BRITISH COLUMBIA
COAST WILL BE THE MAIN FEATURE TO IMPACT OUR LOCAL WEATHER NEXT
WEEK. IT WILL BRING UNSEASONABLY COOL AND UNSETTLED WEATHER EARLY
IN THE WEEK.  AS IT SLOWLY PUSHES EAST OF THE AREA THE PATTERN
BECOMES DRIER WITH MODERATING TEMPERATURES TOWARD NEXT WEEKEND.

MON NIGHT & TUESDAY...THE PERIOD STARTS WITH A STRONG UPPER TROUGH
THAT WILL SLOWLY INCH ACROSS THE AREA MONDAY NIGHT INTO TUESDAY.
THIS WILL KEEP THE AREA UNSETTLED AND QUITE COOL FOR THE LATER PART
OF MAY. MOST OF THE CWA WILL NOT GET OUT OF THE 50S...AND A FEW
SPOTS MAY STRUGGLE TO GET OUT OF THE 40S IF THERE IS A DENSE ENOUGH
OVERCAST AND ENOUGH RAIN AROUND.

WEDNESDAY & THURSDAY...AS THE UPPER TROUGH CONTINUES TO SLOWLY PUSH
EAST OF THE AREA THE UPPER FLOW WILL TURN INTO THE NORTHWEST.
HEIGHTS AND THICKNESS VALUES REMAIN ON THE LOW SIDE WITH
TEMPERATURES REMAINING BELOW AVERAGE. IT LOOKS LIKE THE TYPE OF
PATTERN WHERE A SHORTWAVE IN THE FLOW COULD COMBINE WITH STRONG
LATE MAY HEATING TO GENERATE AN AFTERNOON OR EARLY EVENING SHOWER
IN A FEW SPOTS...BUT THIS FAR OUT NOT WORTHY OF A BROAD-BRUSH OF 20
POPS AS COVERAGE OF SHOWERS LIKELY TO BE SMALL. THE BEST CHANCE
OF A FEW SHOWERS WOULD PROBABLY BE THURSDAY AS MANY OF THE MEDIUM
RANGE MODELS BRING A STRONGER WAVE ACROSS THE AREA. WOULD PREFER
TO MONITOR FOR ANOTHER DAY OR TWO BEFORE BEEFING UP POPS.

FRIDAY & SATURDAY...THE UPPER TROUGH CONTINUES TO SLIDE OFF TOWARD
THE GREAT LAKES WITH SOME UPPER RIDGING TO SLOWLY BUILD IN FROM THE
WEST.  THIS IS TYPICALLY A DRY PATTERN...AND TEMPERATURES SHOULD
RETURN TO MORE SEASONABLE LEVELS.  MODELS AND ENSEMBLES NOT IN THE
BEST OF AGREEMENT ON HOW PROGRESSIVE THE UPPER TROUGH TO OUR EAST
WILL BE...NOR ARE THEY IN GREAT AGREEMENT ON THE NEXT PACIFIC TROUGH
AND DOWNSTREAM RIDGING...SO CONFIDENCE IS BELOW AVERAGE...BUT BASED
ON THE PATTERN OF LATE WOULD TEND TO FAVOR A DRIER AND WARMER PERIOD
BY NEXT WEEKEND. CB

&&

.AVIATION...
ANY LEFTOVER IFR CEILINGS WILL IMPROVE TO MVFR THROUGHOUT THE REMAINDER
OF THE AFTERNOON WITH MOST CEILINGS SCATTERING OUT IN COVERAGE.
SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP WELL TO THE
SOUTHWEST OF THE TAF SITES THIS AFTERNOON AND TRACK NORTHEASTERLY
ENTERING THE REGION THIS EVENING. ACTIVITY SHOULD MOVE OUT OF THE
AREA BY EARLY SUNDAY MORNING WITH IFR AND MVFR CEILINGS IN ITS
WAKE. BREEZY EAST WINDS WILL TAPER OFF BY EARLY SUNDAY MORNING AS
WEAK LOW PRESSURE PASSES THROUGH. MCZ

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY UNTIL 7 PM MDT THIS EVENING FOR FORT PECK
LAKE.

&&

WEATHER.GOV/GLASGOW

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE GLASGOW MT
244 PM MDT SAT MAY 19 2007

MTZ017-021>023-200400-
CENTRAL AND SOUTHERN VALLEY-PETROLEUM-GARFIELD-MCCONE-
244 PM MDT SAT MAY 19 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST
MONTANA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SCATTERED THUNDERSTORMS ARE EXPECTED THIS EVENING WITH SOME
POSSIBLY BEING SEVERE. THIS MEANS THAT SOME OF THESE STORMS MAY
CONTAIN LARGE HAIL AND DAMAGING WINDS. THE STRONGEST STORMS ARE
EXPECTED TO BE SOUTH OF FORT PECK LAKE. A LAKE WIND ADVISORY ALSO
IN EFFECT FOR FORT PECK LAKE UNTIL 7 PM. SOUTHEAST WINDS OF 20 TO
30 MPH ARE EXPECTED TO DIMINISH TO LESS THAN 20 MPH THIS EVENING.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

NO HAZARDOUS WEATHER EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

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