000
FXUS65 KGGW 282101
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
301 PM MDT THU AUG 28 2008

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SATURDAY...
FLAT UPPER RIDGE WILL BE SLIDING ACROSS MONTANA OVER THE NEXT FEW
DAYS...WITH NORTHWEST FLOW ALOFT TODAY TRANSITIONING TO SOUTHWEST
BY SATURDAY. OVERALL EXPECT DRY AND WARMING CONDITIONS THROUGH THE
END OF THE WEEK.

WEAK SHORTWAVE SLIDING THROUGH THE NORTHWEST FLOW THIS AFTERNOON
PUSHING AN AREA OF CLOUDS OVER NORTHEAST MONTANA. LEE TROF
DEVELOPING ACROSS CENTRAL MONTANA WITH STRONG DOWNSLOPE WINDS TO
THE WEST OF THE TROF. WINDS NOT AS STRONG OVER NORTHEAST MONTANA
BUT WITH THE SHORTWAVE...MAY BE SLOW TO DECOUPLE THIS EVENING.

UPPER FLOW BECOME MORE WESTERLY ON FRIDAY AND WILL KEEP LEE TROF
IN POSITION AS WILL HIGH PRESSURE STRENGTHENING OVER THE DAKOTAS.
THIS WILL TURN THE WINDS TO THE SOUTHEAST BY FRIDAY NIGHT.

UPPER TROF MOVE ACROSS THE PACIFIC COAST ON SATURDAY...PUSHING
THERMAL TONGUE INTO EASTERN MONTANA. LOW LEVEL JET INCREASES
ACROSS THE DAKOTAS. AIRMASS EXPECTED TO BE QUITE DRY AHEAD OF COLD
FRONT PASSAGE LATE SATURDAY...AND CAPPED BY THE DEEP INFLUX OF HOT
AIR. THUS NOT EXPECTING PRECIPITATION SATURDAY AFTERNOON. EBERT

.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY...
MODELS ALL CONTINUE TO TRACK A VIGOROUS UPPER LOW ACROSS THE
NORTHERN ROCKIES EARLY NEXT WEEK...HOWEVER ENOUGH SPREAD STILL
EXISTS IN THE TRACK OF THIS LOW THEREBY REDUCING CONFIDENCE IN THE
LOCATION OF POTENTIALLY ROBUST RAINFALL TOTALS. UNLIKE THE GFS...THE
LATEST ECWMF DOES NOT INDICATE MUCH PHASING AT ALL OF THIS LOW
WITH A TROF IN THE NORTHERN STREAM...THEREFORE IT REMAINS SLOWER
AND FARTHER WEST WITH THE SYSTEM. NOT ENOUGH EVIDENCE WAS GAINED
FROM TODAY/S GUIDANCE TO SUPPORT SIGNIFICANT CHANGES...SO OUTSIDE
OF MINOR COLLABORATION EDITS THE ONLY NOTEWORTHY CHANGES WERE TO
INCREASE CLOUD COVER SOME ON TUESDAY WHILE LOWERING MONDAY/S HIGH
TEMPS CONSERVATIVELY GIVEN DEGREE OF EXPECTED LOW CLOUDS IN THE
POST-FRONTAL ENVIRONMENT. MCZ

PREVIOUS LONG TERM DISCUSSION...
00Z MODELS CONTINUE TO BRING A STRONG PACIFIC TROUGH INTO THE
INTERMOUNTAIN WEST LATE THIS WEEKEND AND EARLY NEXT WEEK.
UNCERTAINTY STILL EXISTS BETWEEN VARIOUS MODEL RUNS...WHICH WILL
IMPACT RAINFALL AMOUNTS AND TEMPERATURES. GFS AND ECMWF GIVE THE
LOCAL FORECAST AREA A GOOD CHANCE AT RAINFALL. HOWEVER...CANADIAN
CONTINUES TO BE FARTHER WEST WITH THE UPPER TROUGH. CLOSER
EXAMINATION OF THE SYNOPTIC FEATURES SUNDAY AND MONDAY REVEALS A
COLD FRONT...WHICH MOVES THROUGH THE CWA...AND THEN STALLS OVER
THE DAKOTAS AS A SURFACE WAVE DEVELOPS ALONG THE FRONT.
MEANWHILE...AN UPPER JET STREAK EXTENDS FROM WESTERN MONTANA INTO
CENTRAL CANADA. THERE IS A POSSIBILITY THAT RAIN DEVELOPS ALONG
THE COLD FRONT IN THE DAKOTAS...AND OVER CENTRAL MONTANA WITH THE
BEST DYNAMICS ASSOCIATED WITH THE RIGHT ENTRANCE REGION OF THE
UPPER JET. WITH THIS SCENARIO THE LOCAL FORECAST AREA COULD MISS
THE BEST MOISTURE. GIVEN THE UNCERTAINTY VERY FEW CHANGES WERE
MADE TO THE EXISTING POP GRIDS.

AS FOR TEMPERATURES...THE ENSEMBLE MOS NUMBERS SHOW SIGNIFICANT
STANDARD DEVIATION ON SUNDAY AND MONDAY...WITH VALUES OF 5 AND 6
RESPECTIVELY AT GGW. THE OPERATIONAL GFS IS AMONG THE COLDER MEMBERS
AND THE COLDEST SCENARIO WOULD BE HIGH TEMPERATURES IN THE 50S.
AGAIN WITH THE UNCERTAINTY VERY LITTLE CHANGES WERE MADE TO THE
EXISTING TEMPERATURE GRIDS.

BY THE MIDDLE OF NEXT WEEK...WEAK UPPER RIDGING
DEVELOPS...FOLLOWED BY ANOTHER TROUGH. AJZ

&&

.AVIATION...
VFR WITH SCATTERED TO BROKEN CLOUDS AROUND 9K FT AGL CLEARING OUT
THROUGH THIS EVENING. GUSTY WEST-NORTHWEST WINDS UP TO 25 KT WILL
REDUCE TO LESS THAN 10 KT AROUND SUNSET. MCZ

&&

.FIRE WEATHER...
NEAR CRITICAL FIRE WEATHER CONDITIONS ARE EXPECTED ON SATURDAY
WITH TEMPERATURES PUSHING INTO THE 90S AND RELATIVE HUMIDITY
FALLING BELOW 20 PERCENT AHEAD OF STRONG COLD FRONT. STRONG WINDS
ARE POSSIBLE WITH THE FRONTAL PASSAGE LATE SATURDAY AFTERNOON OR
EVENING. COOLER AND WETTER WEATHER WILL FOLLOW THE FRONTAL PASSAGE
FOR EARLY NEXT WEEK.

&&

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

&&

$$

WEATHER.GOV/GLASGOW

NWS GGW Office Area Forecast Discussion