606
FXUS02 KWBC 121903
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
302 PM EDT THU JUN 12 2008
VALID 12Z SUN JUN 15 2008 - 12Z THU JUN 19 2008
..FINAL MEDIUM RANGE DISCUSSION
HPC WILL REMAIN IN THE MIDDLE OF THE ENVELOPE OF 00Z MODEL
SOLUTIONS ON ALL THE MAJOR FEATURES PENDING UPCOMING MODEL RUNS.
ALTHOUGH IN GENERAL MODELS ARE STILL TRANSITIONING TO A NE PACIFIC
TROF/ROCKIES RIDGE/E COAST LONGWAVE TROF...THE NEW 12Z/12 GFS HAS
DESTROYED ITS OWN 00Z CONTINUITY ACROSS THE ENTIRE N PACIFIC THE
FIRST HALF OF NEXT WEEK. THE BOTTOM LINE OF THE GFS RUN TO RUN
CONTINUITY CHANGES IS THAT IT BECOMES CONSIDERABLY WEAKER WITH THE
MEAN TROF ALONG THE W COAST BY DAY 6...LIFTING THE MAIN VORTEX
THAT HAD BEEN FORECAST NEAR 50N/130W WED DAY 6 NEWD INTO SW
CANADA. THE 12Z/12 CANADIAN/UKMET BEHAVE SOMEWHAT LIKE THE NEW GFS
ACROSS THE PACIFIC DAYS 5-7. THOSE MODELS TOO MIGHT BE SUSPECT.
BUT IS OUR EARLY CONTINUITY RELIABLE? ONE THING ALL THE NEW 12Z
GUIDANCE IS DOING...INCLUDING THE 12Z/12 ECMWF...IS GOING FOR A
DEEPER TROF FARTHER W THAN 00Z GFS/ECMWF CONTINUITY DAYS 5-6 IN
THE WRN PACIFIC S OF KAMCHATKA. THIS CHANGE FAVORS THE DOWNSTREAM
TROF BEING CLOSER TO 140W DAY 6 INSTEAD OF ON THE PACIFIC NW
COAST...RESULTING IN HIGHER HEIGHTS DAYS 5-7 ALONG THE W COAST.
TIME WILL TELL. WOULD LIKE TO SEE MORE TREND IN UPCOMING RUNS
BEFORE CHANGING CONTINUITY.
..REGIONAL HIGHLIGHTS
..EAST OF THE ROCKIES
AGAIN TODAY...CONVECTION WILL BE ACTIVE ON THE LEADING EDGE OF THE
NEW LONGWAVE TROF THAT WILL BE DEVELOPING OVER THE ERN STATES.
FRONTAL AND PRE-FRONTAL CONVECTION ALONG THAT LEADING EDGE WILL BE
THE MAIN CONTRIBUTOR TO PCPN ABOVE LATITUDE 33N. BELOW THAT
LATITUDE MORE TYPICAL CONVECTION OVER THE SERN STATES AND GULF
COAST REGION WILL PREVAIL.
ONE COLD FRONT WILL DIE OUT OVER UPPER PORTIONS OF THE GULF STATES
AND THE CAROLINAS ON SUN DAY 3. THIS FRONT WILL SEPARATE SOMEWHAT
DRIER AIR TO THE N FROM TYPICAL HOT HUMID AIR TO THE S. THE USUAL
DIURNAL CONVECTIVE ACTIVITY WILL CONTINUE BELOW LATITUDE 33N
ESPECIALLY OVER THE S ATLANTIC/GULF COASTS AND FL.
A SECOND STRONGER COLD FRONT WILL PUSH S INTO THE ERN PORTIONS OF
THE NATION DAYS 4-6.
THIS FRONT WILL ENCOUNTER THE BEST MOISTURE RETURN FLOW IN THE
VCNTY OF OK/AR/SRN MO. DESPITE THE FACT THAT BOTH THE GFS AND
ECMWF QPFS COULD BE SHOWING EXCESSIVE FEEDBACK... SOME LOCALLY
HEAVY RAINS ARE REALISTICALLY POSSIBLE MON-TUE VCNTY OF THAT FRONT
AS IT SAGS S. BEHIND THE FRONT...UNSEASONABLY COOL AND DRY AIR
WILL DOMINATE THE ERN HALF OF THE LOWER 48 STATES.
..ROCKIES WWD
REBOUNDING TEMPS IN THE WAKE OF THE DEPARTING PRESENT COLD CLOSED
LOW NOW IN THE NWRN PLAINS WILL GRADUALLY YIELD TO ANOTHER COOLING
TREND FROM TUE ONWARD AS HEIGHT FALLS MOVE BACK INTO THE PACIFIC
NW COAST BY THU DAY 7. SHOWERS ASSOCIATED WITH COOLING ALOFT MAY
BEGIN OVER HIGHER TERRAIN OF THE CASCADES AND COASTAL RANGES AS
EARLY AS TUE. THESE AMOUNTS COULD INCREASE WED/THU AND BECOME
SIGNIFICANT OVER HIGHER TERRAIN OF WA/OR...ESPECIALLY IF AN UPPER
LOW MOVES BODILY INLAND FROM OFFSHORE.
ASIDE FROM THE PACIFIC NW PRECIP...THE REMAINDER OF THE WEST
SHOULD BE DRY WITH NO MONSOONAL PRECIP FOR THE SWRN STATES IN
VIEW.
FLOOD
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