071
FXUS02 KWBC 021828
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
227 PM EDT MON JUN 02 2008
VALID 12Z THU JUN 05 2008 - 12Z MON JUN 09 2008
TELECONNECTIONS WITH A NORTHWEST/SOUTHEAST POSITIVE ANOMALY
DRIFTING BY 45N 145W FAVORS A CLOSED CYCLONE NEAR THE PACIFIC
NORTHWEST. A TROUGH EDGING EASTWARD THROUGH WESTERN CANADA IS
EXPECTED TO SHIFT THE STUBBORN DEEP CYCLONE INITIALLY IN NUNAVUT
EASTWARD INTO NORTHERN QUEBEC. THE MODELS THAT FIT THIS IDEA BEST
ARE THE 06Z GFS/06Z NCEP ENSEMBLE MEAN.
..NORTHERN PLAINS THROUGH THE EAST
EARLY THIS MORNING...ALL THE GUIDANCE EXCEPT THE 00Z/06Z NCEP
ENSEMBLE MEANS WERE IN GOOD AGREEMENT WITH THE MAIN CYCLONE
LIFTING THROUGH THE NORTHERN PLAINS INTO CANADA...BUT DIFFER
SIGNIFICANTLY REGARDING ITS WARM FRONT. THE 12Z GUIDANCE MUDDIED
UP THE PICTURE BY FORMING A LOW NEAR MICHIGAN WHICH IT TRACKED
THROUGH SOUTHEAST CANADA AHEAD OF THE MAIN CYCLONE. THE 12Z NCEP
ENSEMBLE MEAN DOES NOT FAVOR THIS EXTRANEOUS LOW...SEEN ON THE 12Z
GFS/CANADIAN/UKMET SOLUTIONS...SO DID NOT ADD IT INTO OUR PROGS
WHICH LEADS TO A MORE SOUTHERLY WARM FRONT ACROSS THE MID-ATLANTIC
AND NORTHEAST STATES. CONSIDERING HOW FAR WEST THE MAIN LOW TRACK
IS...THINK A BACKDOOR FRONT MOVING INTO/THROUGH PART OF THE
MID-ATLANTIC STATES SIMILAR TO THE 06Z GFS/00Z ECMWF COMPROMISE
APPEARS BEST.
..NORTHWEST AND GULF OF ALASKA
OUT WEST AND ACROSS THE GULF OF ALASKA...THINK THE 00Z UKMET/00Z
ECMWF/00Z CANADIAN ARE IN THE WRONG PLACE WITH THIS SYSTEM...WHICH
THEY MOVE SLOWLY OVER THE TOP OF A BUILDING RIDGE. THINK THE
SYSTEM WILL MOVE QUICKER OVER THE TOP OF THE RIDGE INTO WESTERN
CANADA/THE PACIFIC NORTHWEST SIMILAR TO THE 06Z GFS/06Z NCEP
ENSEMBLE MEAN DUE TO THE SUPERGEOSTROPHIC/QUICK FLOW NORMALLY
FOUND OVER THE TOP OF A WARM CORE RIDGE.
DUE TO ALL THE ABOVE...AS WELL AS TYPICAL VERIFICATION SCORES AND
INCREASING UNCERTAINTY AS WE APPROACH THE FORECAST FOR EARLY NEXT
WEEK...CHOSE A 06Z GFS/00Z ECMWF SOLUTION EARLY ON BEFORE GOING TO
A 06Z GFS/06Z NCEP ENSEMBLE MEAN BLEND DURING THE LATTER HALF OF
THE PERIOD. THE ONE EXCEPTION IS THE SYSTEM MOVING OUT OF THE
NORTHERN PLAINS THROUGH CANADA...WHERE A BLEND OF THE 06Z GFS/00Z
ECMWF SOLUTIONS WAS USED THROUGHOUT THE PERIOD.
..RAINFALL
THE HEAVIEST PRECIPITATION DURING THE MEDIUM RANGE PERIOD APPEARS
TO BE FOCUSED IN THE MIDWEST/GREAT LAKES/OHIO VALLEY WITHIN THIS
PREFERRED PATTERN. A CONVECTIVE PATTERN WITH GREATER/MORE TYPICAL
COVERAGE FOR JUNE IS EXPECTED ACROSS SOUTHERN PORTIONS OF THE
SUNSHINE STATE BY FRIDAY JUNE 6 SOUTH OF AN UPPER LEVEL
TROUGH...WHICH SHOULD BEGIN TO RELIEVE DRY SEASON CONDITIONS. THE
REMAINS OF ALMA/ARTHUR/NEW TROPICAL DISTURBANCE SOUTH OF THE
MEXICAN ISTHMUS SHOULD MOVE WEST TO WEST-NORTHWEST...MOVING
FARTHER INTO MAINLAND MEXICO AND DISSIPATING BY EARLY IN THE
MEDIUM RANGE PERIOD.
ROTH
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