FXUS63 KBIS 221108 CCA
AFDBIS
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE BISMARCK ND
508 AM CST TUE DEC 22 2009
.SHORT TERM...TODAY THROUGH THURSDAY NIGHT...
ALL FOCUS IN THE SHORT TERM IS IN REGARDS TO THE EVER INCREASING
MAJOR WINTER STORM SLATED WEDNESDAY THROUGH FRIDAY. WITH THE HIGH
VOLUME OF CHRISTMAS TRAVEL AND INCREASING CONFIDENCE AMONG THE
MODELS...HAVE DECIDED TO ISSUE A WINTER STORM WATCH FOR ALL OF
WESTERN AND CENTRAL NORTH DAKOTA. THE WINTER STORM WATCH BEGINS
WEDNESDAY MORNING FOR WESTERN AND MOST OF CENTRAL NORTH DAKOTA.
BEGAN THE WINTER STORM WATCH FOR THE FAR EASTERN ZONES WEDNESDAY
EVENING. GOOD COLLABORATION AND AGREEMENT AMONG NEIGHBORING OFFICES.
THE 00Z ECMWF...LIKE LAST NIGHT...HAS CHANGED SLIGHTLY IN TRYING
TO MOVE THE PRECIPITATION OUT OF WESTERN AND PORTIONS OF CENTRAL
NORTH DAKOTA FASTER THAN THE GFS. THE MAIN REASON IS THE ECMWF IS
HAVING TROUBLE FULLY MERGING A NORTHERN STREAM UPPER LOW...WHICH
IS NOW OVER NORTHERN BRITISH COLUMBIA...INTO A STRONG SOUTHERN
STREAM UPPER LOW NOW BEGINNING TO DEVELOP OVER THE SOUTHWEST. THE
WHOLE SYSTEM IS FORECAST TO MOVE INTO THE UPPER MIDWEST THURSDAY
AND FRIDAY. THE PREVIOUS RUNS OF THE ECMWF WERE MERGING THE LOWS
TOGETHER BUT RECENTLY THERE HAS BEEN SOME FLIP-FLOPPING EVERY OTHER
MODEL RUN. THE GFS CONTINUES TO MERGE THE LOWS AND HENCE PRODUCES
THE MOST SNOW. STILL SOME UNCERTAINTY ON THIS BUT BOTH MODELS
FOCUS THE HEAVIEST SNOWFALL TOTALS OVER OUR FAR EAST CENTRAL ZONES
WHERE A FOOT OR MORE OF SNOW IS POSSIBLE BY SATURDAY MORNING. THE
REST OF WESTERN AND CENTRAL NORTH DAKOTA AT PRESENT CAN EXPECT
BETWEEN 6 AND 10 INCHES OF SNOW BY FRIDAY MORNING. EXPECT THIS TO
BE REFINED A BIT AS WE GET CLOSER. ANOTHER ASPECT OF THIS STORM IS
BOTH THE GFS AND ECMWF DEVELOP STRONG NORTHWEST WINDS OVER THE
AREA BEGINNING THURSDAY AND CONTINUING INTO FRIDAY. EXPECT
NORTHWEST WINDS OF 20 TO 35 MPH WITH GUSTS BETWEEN 35 AND 40 MPH.
THEY MAY BE HIGHER DEPENDING ON THE EXACT TRACK OF THE STORM. BUT
BLOWING AND DRIFTING SNOW ALONG WITH NEAR BLIZZARD CONDITIONS IS
CERTAINLY POSSIBLE DURING THE MIDDLE AND LATE STAGES OF THE STORM.
SO WILL NEED TO CONSIDER THIS IN MORE DETAIL LATER TODAY AND
TONIGHT.
AS FAR AS TODAY IS CONCERNED...NAM BUFR SOUNDINGS SHOW POTENTIAL
FOR PATCHY FREEZING DRIZZLE OR SOME OCCASIONAL LIGHT SNOW...BUT
OVERALL NO WHERE NEAR AS ACTIVE AS MONDAY. THINGS BEGIN TO COME
TOGETHER LATER TONIGHT AND WEDNESDAY AS MENTIONED ABOVE.
.LONG TERM...
EXTENDED PERIOD BEGINS WITH THE LARGE VERTICALLY STACKED STORM
SYSTEM SLOWLY MAKING ITS WAY ACROSS THE CENTRAL US. MODELS ARE IN
GOOD AGREEMENT WITH THE TRACK OF THE STORM AS IT LIFTS NORTHEAST
OVER THE GREAT LAKES INTO SUNDAY AND FINALLY EXITING THE COUNTRY
MONDAY. NORTH DAKOTA WILL RESIDE ALONG THE NORTHWEST PERIPHERY OF
THE STORM FRIDAY AND SATURDAY...WITH WRAP-AROUND MOISTURE PROVIDING
A GOOD CHANCE FOR SNOW AND A GOOD CHANCE FOR SIGNIFICANT
ACCUMULATIONS. A FURTHER CONCERN WILL BE THE POSSIBILITY OF HIGH
WINDS ON FRIDAY AND FRIDAY NIGHT DUE TO A TIGHT PRESSURE GRADIENT
ALONG THE WESTERN SIDE OF THE LOW. ALTHOUGH CONFIDENCE IS RELATIVELY
GOOD WITH THESE RESULTING CONDITIONS...IT IS STILL A BIT TOO FAR OUT
TO DETERMINE WHEN AND WHICH HEADLINES MAY BE NEEDED. NWS WILL
CONTINUE TO MONITOR FURTHER MODEL RUNS AND UPDATE THE FORECAST AS
NEEDED.
ONCE THE SYSTEM IS OUT OF OUR AREA...STRONG NORTHWEST FLOW WILL
LIKELY DEVELOP ALOFT...AND CONTINUE THROUGH THE REST OF THE TERM.
THERE IS A SLIGHT CHANCE OF SOME SNOW DEVELOPING IN ASSOCIATION WITH
FAST MOVING IMPULSES WITHIN THIS FLOW...BUT CONFIDENCE REMAINS TOO
LOW TO PLACE WITHIN THE FORECAST AT THIS TIME. WILL THEREFORE KEEP
THE FORECAST DRY FROM SATURDAY ON THROUGH THE END OF THE PERIOD.
TEMPERATURES SHOULD REMAIN BELOW NORMAL THROUGH THE TERM. STRONG
NORTHERLY WINDS BEHIND THE STORM SYSTEM SHOULD BRING A REINFORCING
SHOT OF COLD CANADIAN AIR OVER THE WEEKEND...WITH COLD ADVECTION
LIKELY TO REMAIN OVER THE AREA FOR THE DURATION OF THE FORECAST.
&&
.AVIATION...
NUMEROUS AVIATION ISSUES TODAY WITH HIGH CLOUD MASKING MVFR TO IFR
CONDITIONS OVER TAF SITES. HOWEVER WILL TEMPO THIS PRESENT WEATHER
WITH GENERALLY DETERIORATING CONDITIONS AS WE GO FURTHER OUT IN TIME.
APPROACH OF STRONG CENTRAL CONUS SYSTEM MAY SEE IFR CONDITIONS IN
PRECIPITATION BY END OF PERIOD OVER WESTERN TAFS.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH FRIDAY
AFTERNOON FOR NDZ001>004-009>012-017>022-031>035-040>046.
WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH LATE FRIDAY
NIGHT FOR NDZ005-013-023-025-036-037-047-048-050-051.
&&
$$
KS/BPN/HW
