439
FXUS02 KWBC 111823
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
220 PM EDT WED JUN 11 2008
VALID 12Z SAT JUN 14 2008 - 12Z WED JUN 18 2008
FINAL PROGS SUBSTITUTED WERE MOSTLY UNCHANGED FROM UPDATED
PRELIMS. THE 12Z/11 GFS WAS SIMILAR ENOUGH TO ITS 00Z CONTINUITY
THAT OUR REASONING FOLLOWS THE SAME LINE OF THOUGHT AS IN THE
UPDATED PRELIMS. NEW 12Z/11 MODEL GUIDANCE ALSO SUPPORTED OUR
EARLIER REASONING.
A PATTERN CHANGE IS INDICATED ACROSS THE NATION DURING THE MEDIUM
RANGE PERIOD. THERE WILL BE ALMOST A REVERSAL OF THE PRESENT
LONGWAVE PATTERN TO A NE PACIFIC TROF/WRN NOAM RIDGE/E COAST TROF
PATTERN. MODEL AND ENSEMBLE MEANS...ALBEIT TIMING DIFFERENCES IN
SHORTWAVES...ARE ALL HEADED TOWARDS THE SAME LARGE SCALE LONGWAVE
PATTERN AS THE 00Z/11 GEFS MEAN...WHICH WAS THE FORERUNNER IN
HERALDING THE NEW LONGWAVE PATTERN.
I SAID EARLIER THAT THE 00Z/11 GFS RUN WAS NOT
UNREASONABLE...MOSTLY IN SYNC WITH THE DAILY PATTERNS OF THE
00Z/11 ECMWF. THE SAME CAN BE SAID FOR THE 12Z/11 GFS...WHICH HAS
FAIR CONTINUITY FROM ITS 00Z RUN EXCEPT THAT IT HAS DEAMPLIFIED
ITS DAY 5 SHORTWAVE OVER THE MIDWEST. HOWEVER...THAT DAY 5 12Z/11
GFS CONTINUITY CHANGE LEADS TO ONLY MINIMAL 00Z TO 12Z DIFFERENCE
ALONG THE E COAST STATES FOR TUE/WED DAYS 6-7. THE 12Z
GFS/CANADIAN/UKMET ALL POINT TO THE CENTER OF THE ENVELOPE OF
SOLUTIONS CONCERNING THE TROF ALONG THE E COAST DAYS 5-6. THE
UPPER TROF SHOULD BE LESS AMPLIFIED THAN THE 00Z/11 GFS WAS OVER
THE NERN STATES ON DAY 6...YET STILL ANOMALOUSLY DEEP AND COOL FOR
MID JUNE.
HPC NOW PREFERS THE MIDDLE OF THE ROAD TO VERIFY THE BEST NEXT
WEEK WITHIN THE ENVELOPE OF ENSEMBLE SOLUTIONS. OVERALL...GOOD 12Z
MODEL AGREEMENT ON ALL THE MAIN SYNOPTIC MEAN UPPER FEATURES: THE
CLOSED LOW OFF THE BC COAST...THE ROCKIES RIDGE...AND THE TROF
ALONG THE E COAST STATES.
..REGIONAL HIGHLIGHTS
..EAST OF THE ROCKIES
THE DEVELOPMENT OF A NEW LONGWAVE TROF OVER THE ERN CONUS BODES
FOR AN ACTIVE CONVECTIVE PERIOD. FRONTAL AND PRE-FRONTAL
CONVECTION WILL CONTRIBUTE TO MOST OF THE PRECIP ABOVE LATITUDE
33N. RAINFALL MAXIMA WILL BE FAVORED DYNAMICALLY ON THE E SIDE OF
THE NEW LONGWAVE TROF AND OROGRAPHICALLY NEAR THE APPALACHIANS.
ANOTHER MAXIMUM AREA WILL BE VCNTY OF OK/AR. LINGERING CONVECTION
ON SAT DAY 3 ALONG A WEAKENING BOUNDARY THERE WILL BE FOLLOWED BY
MORE ORGANIZED CONVECTION ALONG A STRONG COLD FRONT AROUND DAY 5.
ALTHO BOTH THE GFS AND ECMWF QPF FORECASTS THERE APPEAR TO SUFFER
FROM CONVECTIVE FEEDBACK...IT IS NOT OUT OF THE QUESTION THAT MCS
DEVELOPMENT SOMEWHERE IN OK OR AR COULD YIELD SOME EXCESSIVE
RAINFALL TOTALS MON. EXPECT THE USUAL DIURNAL RECIP OVER THE SERN
STATES...ESP THE GULF COAST.
..ROCKIES WESTWARD
THE BUILDING OF A NEW LONGWAVE RIDGE OVER THE WRN CONUS WILL LEAD
TO A WARMER REGIME MOST PLACES. OVER ALMOST ALL THE NRN ROCKIES
AND PACIFIC NW...IT WILL BE DRIER AS WELL AS WARMER. THE UPPER
DYNAMICS AND COLD AIR ALOFT OFF THE VANCOUVER/BRITISH COLUMBIAN
COAST MAY BRING A FEW SHOWERS TO HIGHER TERRAIN OF THE WA COASTAL
RANGES. NO SIGN OF ANY MONSOON YET FOR THE SWRN STATES.
FLOOD
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