319
FXUS02 KWBC 221930
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
329 PM EDT SUN JUN 22 2008
VALID 12Z WED JUN 25 2008 - 12Z SUN JUN 29 2008
..UPDATED PRELIM MEDIUM RANGE DISCUSSION
12Z/22 FINAL GRAPHICS WERE MOSTLY UNCHANGED FROM THE EARLIER
UPDATED PRELIM.
THE NEW 12Z/22 GFS FOLLOWS THE GENERAL THEME OF OUR PRELIM PROGS
BUT MAY BE OVERDEVELOPING A SHORTWAVE MOVING ACROSS THE NE BORDER
STATES INTO A CLOSED UPPER LOW OVER FAR SE CANADA BY SUN DAY 7.
THE HIGHER AMPLITUDE OF THE GFS WITH THIS SYS CANNOT BE IGNORED
ALTOGETHER SINCE IT HAS SOME SUPPORT FROM THE 12Z/22 CANADIAN AND
UKMET. HOWEVER THE HIGHER AMPLITUDE SOLUTIONS ARE TEMPERED BY THE
NEW 12Z/21 GEFS MEAN WHICH IS SOMEWHAT SLOWER AND LESS AMPLIFIED
THAN ALL THE NEW OPERATIONAL MODEL SOLUTIONS WITH THE TROF OVER
THE NERN QUADRANT OF THE CONUS SAT DAY 6. THE NEW 12Z/22 ECMWF
FOLLOWS ITS OWN CONTINUITY QUITE WELL OVER THE CONUS THRU THE
MEDIUM RANGE BUT BEGINS TO HAVE PROBLEMS IN THE CENTRAL PACIFIC BY
DAY 7.
UPSTREAM OF THIS NE CONUS TROF...MODELS ARE IN DECENT AGREEMENT ON
A STRONG GULF OF ALASKA/NE PACIFIC SYS THRU DAY 5...BUT BEGIN TO
DIVERGE OVER MOST OF THE NE PACIFIC BY NEXT WEEKEND. IN LIGHT OF
UNCERTAINTY OF FCST DETAILS FROM THE PACIFIC ACROSS THE NRN CONUS
AND SRN CANADA...WE PREFER TO MAINTAIN A SOLN WHICH IS TOWARD THE
MIDDLE OF THE MODEL/ENSEMBLE SPREAD...DOWNPLAYS SMALLER SCALE
FEATURES...AND YIELDS FEW CONTINUITY CHANGES.
..REGIONAL HIGHLIGHTS
..PLAINS/MS VLY
AGAIN TODAY...WE SEE THE PLAINS AND MS VLY UNDER THE GUN AS LOW
PREDICTABILITY MESOSCALE VORT FEATURES MOVE THRU A FLAT MEAN UPPER
RIDGE OVER THE ROCKIES INTO THE NATIONS MIDSECTION. ACTIVITY WILL
BE WELL UNDERWAY IN THE SHORT RANGE WITH MOIST S-SW LOW LEVEL FLOW
IN PLACE THRU MOST OF THE PLAINS AT THE BEGINNING OF THE MEDIUM
RANGE PERIOD. THOUGH SCTD CONVECTION COULD OCCUR ALMOST ANYWHERE
IN THE PLAINS...A BROAD WARM ADVECTION SIGNATURE...COMBINED WITH
MESOSCALE FORCING THAT COULD HELP BREAK ANY CAP...FAVORS THE N
CENTRAL PORTIONS OF THE PLAINS/MS VLY FOR STORMS WED-FRI UNTIL A
WEAK COLD FRONTAL PASSAGE SOMETIME NEXT WEEKEND. UNFORTUNATELY
THIS SETUP PUTS FLOODED AREAS OF IA AND MO AT RISK FOR MORE
EXCESSIVE RAINFALL THIS WEEK. THE GFS SHOWS AN AREA OF HIGH
INSTABILITY DEVELOPING NW IA/SE SD ON WED THAT HANGS AROUND AT
LEAST INTO FRI WHILE EXPANDING EWD INTO IA AND SRN WI/NRN IL.
..TX GULF COAST/FL
FAIRLY TYPICAL CONVECTION IS EXPECTED OVER PENINSULAR FL THIS
WEEK. A SUBTLE WEAKNESS ALOFT MAY HELP FOCUS SHOWERS/TSTMS ALONG
THE TX /A COAST THU INTO SAT. THE GFS AND ECMWF SUGGEST THAT THE
CENTRAL GULF COAST REGION MAY BECOME MORE ACTIVE NEXT WEEKEND AS
THEY AIM HIGHER PWS TOWARDS THAT AREA.
..WEST
WARM AND DRY THIS WEEK WITH PERHAPS A FEW WIDELY SCTD SHOWERS OVER
THE HIGHER TERRAIN OF WA/OR/MT WED WITH THE PASSAGE OF A WEAK
SHORT WAVE.
FLOOD
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