091
FXUS02 KWBC 191930
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
330 PM EDT THU JUN 19 2008
VALID 12Z SUN JUN 22 2008 - 12Z THU JUN 26 2008
..FINAL MEDIUM RANGE DISCUSSION
THE LONGWAVE PATTERN OVER THE NEXT WEEK WILL BE IN THE PROCESS OF
READJUSTMENT FROM AN ANOMALOUSLY DEEP COLD TROF OVER THE ERN CONUS
TO ONE MORE TYPICAL FOR EARLY SUMMER. IN ABOUT A WEEK...THE E
COAST TROF SHOULD BE MOSTLY FILLED...LEAVING A VERY BROAD TROF IN
THE ERN PACIFIC AND A RIDGE OVER THE NRN PLAINS.
THE 12Z/19 GFS AND ECMWF HAVE REVERSED ROLES FROM THEIR 00Z RUNS
CONCERNING THE POSSIBLE CLOSING OFF SYS ALONG/OFFSHORE THE LOWER
MID ATLANTIC COAST FOR WED/THU DAYS 6-7. THE 12Z GFS IS NOW THE
SLOW CLOSED OFF OUTLIER IN THIS REGARD. NEITHER THE CANADIAN NOR
UKMET...NOR EVEN THE NEW 12Z/19 ECMWF...ARE NOW GOING FOR A CLOSED
OFF SYS. ACROSS THE REST OF THE MAP...LATEST 12Z GUIDANCE IS IN
REASONABLE AGREEMENT THRU DAY 5....AND FAIR AGREEMENT THEREAFTER.
12Z MODELS DAY 6-7 IN THE NE PACIFIC AND GULF OF ALASKA ARE
SUGGESTING THAT LOWER PREDICTABILITY WILL BE SPREADING EWD INTO
THE LOWER 48 AFTER WED.
TODAYS PRELIM RELEASE HAD NOTED A FEW 00Z ECMWF AND NCEP ENSEMBLE
MEMBERS SHOWING A SHARP TROF...POSSIBLY A MID-LEVEL CYCLONE...DAYS
6-7 OFF THE MID ATLANTIC OR NC COAST. OTHERWISE THERE WAS NO
SUPPORT FOR THIS EXTREME E COAST SOLUTION AMONGST THE VARIOUS NCEP
ENSEMBLE MEMBERS OR OTHER OPERATIONAL GUIDANCE. THE FLOW UPSTREAM
DID NOT APPEAR TO BE AMPLIFIED ENOUGH TO LEAD TO SUCH AN AMPLIFIED
SOLUTION...AND THIS ALSO APPEARS TRUE OF 12Z GUIDANCE. HPC WILL
REMAIN IN THE MIDDLE OF THE MAJORITY OF MODEL AND ENSEMBLE
SOLUTIONS OVER MOST OF THE MAP.
REGIONAL HIGHLIGHTS
..AREA AFFECTED BY THE COLD UPPER ERN TROF
A TEMPORARY RETROGRESSION OF THIS TROF BACK TO THE MS VLY ON DAY 3
WILL ALLOW MORE TYPICAL EARLY SUMMER MOISTURE AND 65+TDS/1.5"PWS
TO SURGE BACK NW INTO THE E COAST DAYS BY DAY 3. THIS COULD BE A
SETUP FOR WIDESPREAD CONVECTION SUN THRU THE E COAST STATES AS
INCREASING MOISTURE DESTABILIZES THE LOWER LEVELS UNDER LINGERING
COOL UPPER TEMPS ALOFT. THE ASSOCIATED UPPER SYS WILL BE STRONG
ENOUGH TO SWEEP MOST OF THE DEEP MOISTURE OFFSHORE MON WITH
ANOTHER DEEP SLY PENETRATION OF UNSEASONABLY COOL DRY AIR. EVEN IN
THE DRY AIR...THE INTENSE JUNE SUN MON WILL DESTABILIZE THE AIR
UNDER COOL TEMPS ALOFT AND GENERATE SOME LINGERING SHOWERS N OF
THE MAIN UPPER JET.
BY TUE...THE INTERLUDE OF ANOMALOUS UPPER TROFFING OVER THE E
COAST STATES WILL BEGIN TO WANE. AS UPPER HEIGHTS RISE...THERE
WILL BE DEEP LAYERED WARMING AND DECREASING SHOWER ACTIVITY.
..CENTRAL STATES
THE KEY TO WEATHER HERE WILL BE AT LEAST A TEMPORARY FLATTENING OF
THE UPPER RIDGE IN THE PLAINS STATES...ALLOWING MCS ACTIVITY TO
WORK PROGRESSIVELY FARTHER AND FARTHER E AWAY FROM THE HIGH
PLAINS. THE CENTRAL AND SRN HIGH PLAINS HIGH PLAINS OF SHOULD BE
ACTIVE ON SUN DAY 3. BY MON DAY 4...THE BEST MCS GENERATION AREA
WILL SHIFT EWD INTO NRN OK/CENTRAL KS MON AND EXTEND FARTHER N
INTO THE DAKOTAS. FOR TUE DAY 5...THE REGION FROM MN TO OK LOOKS
PRIMED FOR CONVECTIVE ACTIVITY. AS THE UPPER RIDGE CONTINUES TO
FLATTEN...THE MAIN MCS THREAT WILL SPREAD TO THE LOWER OH AND MID
MS VLYS BY THU DAY 7. CONCERNING THE FLOODED AREA AROUND IA...THE
HIGHEST RISK OF EXCESSIVE RAINFALL SEEMS TO BE AROUND DAY 5.
..WEST
PRETTY QUIET IN THIS PART OF THE WORLD AFTER A FEW SHOWERS AFFECT
HIGHER ELEVATIONS OF WA AND NRN ID SUN DAY 3. OTHERWISE DRY AND
WARM.
FLOOD
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