538
FXUS02 KWBC 271832
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
230 PM EDT FRI JUN 27 2008
VALID 12Z MON JUN 30 2008 - 12Z FRI JUL 04 2008
TELECONNECTIONS WITH A HIGH AMPLITUDE RIDGE WITH ITS APEX OVER THE
YUKON AND A POSITIVE ANOMALY OVER NORTHERN GREENLAND FAVOR ENERGY
UNDERCUTTING THE NORTHWESTERN NORTH AMERICA RIDGE AT THE LATITUDE
OF SOUTHERN BRITISH COLUMBIA...AND A DEEP CYCLONE MOVING THROUGH
EASTERN CANADA NEAR THE 60TH PARALLEL. THE MODELS GENERALLY SHOW
THESE IDEAS...AND ON THE WHOLE ARE IN BETTER THAN AVERAGE
AGREEMENT. THE 00Z CANADIAN IS A QUICK OUTLIER WITH A SYSTEM
MOVING THROUGH THE EASTERN PACIFIC...AND IS OCCASIONALLY MORE
SOUTHERLY WITH THE SYSTEM MOVING THROUGH EASTERN CANADA...SO DID
NOT USE ITS FIELDS FOR THE PRESSURES/500 HPA HEIGHTS. THE 06Z GFS
AND 00Z ECMWF SPLIT THE DIFFERENCE BETWEEN THE 00Z NCEP ENSEMBLE
MEAN AND 00Z ECMWF ENSEMBLE MEAN...SO COMPROMISED BETWEEN THE 06Z
GFS AND 00Z ECMWF FOR PRESSURES. AS FOR DAYS 4-5 QPF...THE
MORNING VERSION USED A BLEND OF YESTERDAYS CONTINUITY AND THE 00Z
ECMWF ENSEMBLE MEAN.
PLAINS/MIDWEST...
THE 00Z ECMWF/12Z GFS SOLUTIONS SHOW A MORE SOUTHERN FRONTAL
SOLUTION THAN THE 06Z GFS...MAINLY BECAUSE OF DIFFERENCES SEEN IN
SHORTWAVE EVOLUTION NEAR THE PACIFIC NORTHWEST AND SOUTHWEST
CANADA LATE IN THE PERIOD /IF A SHORTWAVE MOVES THROUGH THE
WESTERN US/CANADIAN BORDER THE FRONTAL POSITION WOULD END UP BEING
FARTHER NORTHWARD/. SINCE THE MODELS SHOW THE SOUTHERN LIMIT OF
THE HEIGHTS FALLS WITHIN EASTERN NEBRASKA AND IOWA...NO CHANGES
WERE MADE TO CONTINUITY REGARDING THE FRONTAL POSITION...WHICH WAS
THE BIGGEST DIFFERENCE SEEN DURING THE MEDIUM RANGE PERIOD. SINCE
THERE IS A SPLIT SEEN IN THE UPPER PATTERN NEAR
KANSAS/MISSOURI/ARKANSAS...THUNDERSTORM COMPLEXES ARE ANTICIPATED
WITHIN THAT REGION...PARTICULARLY WHEN THE COLD FRONT DROPS DOWN
INTO THE CENTRAL PLAINS/MID-MISSISSIPPI VALLEY TOWARDS THE END OF
THE PERIOD.
CENTRAL APPALACHIANS/TENNESSEE VALLEY...
EARLY IN THE PERIOD...500 HPA HEIGHT ANOMALIES APPROACH 3 STANDARD
DEVIATIONS BELOW NORMAL AS AN UPPER VORTEX MOVES FROM THE GREAT
LAKES NORTHEAST INTO QUEBEC. COOLING ASSOCIATED WITH THE UPPER
TROUGH WILL BE SHORT LIVED THOUGH DUE TO LACK OF A STRONG SURFACE
HIGH AND 500 HPA HEIGHTS REBOUNDING RAPIDLY ACROSS THE REGION BY
WEDNESDAY...AHEAD OF A SHORTWAVE ROUNDING THE VORTEXS SOUTHWEST
PERIPHERY.
FLORIDA...
DIURNAL CONVECTION WILL REIGN SUPREME THIS PERIOD...WITH THE FOCUS
EXPECTED TO LIE ALONG AN AXIS FROM JACKSONVILLE THROUGH CENTRAL
FLORIDA INTO THE EVERGLADES DUE TO THE ORIENTATION OF THE WARM
CORE RIDGE AXIS WHICH NOSES NORTHWARD INTO SOUTHERN SECTIONS OF
THE SUNSHINE STATE LATE IN THE PERIOD. LOCAL AMOUNTS OF 5 OR MORE
INCHES ARE POSSIBLE DURING THE MEDIUM RANGE PERIOD.
ROTH
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