Prognostic Meteorological Discussion
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FXUS02 KWBC 230646
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
245 AM EDT WED JUL 23 2014

VALID 12Z SAT JUL 26 2014 - 12Z WED JUL 30 2014

...OVERVIEW AND GUIDANCE EVALUATION/PREFERENCES...

GUIDANCE CONTINUES TO SUGGEST WELL ABOVE AVERAGE CONFIDENCE IN THE
DEVELOPMENT OF A VERY AMPLIFIED WRN RIDGE/ERN TROUGH PATTERN.
MOST MODEL/ENSEMBLE MEAN RUNS SHOW AN AREA OF MID LVL HGT
ANOMALIES EXCEEDING 2 STDEVS BELOW NORMAL SETTLING INTO THE OH
VLY/CNTRL APLCHNS REGION FOR AT LEAST A PART OF THE LATTER HALF OF
THE PERIOD.  HGT ANOMALIES IN THE SRN PART OF THE UPR HIGH FCST TO
BE CNTRD OVER THE SRN ROCKIES MAY EXCEED 2 STDEVS ABOVE NORMAL AS
WELL.

WHILE THERE IS REMARKABLY GOOD AGREEMENT IN THE RESULTING MEAN
PATTERN BY THE LATTER HALF OF THE PERIOD... SOME QUESTION MARKS
REMAIN IN THE ROUTE TAKEN TO GET THERE.  IN PARTICULAR THERE IS
STILL NOTABLE TIMING SPREAD IN THE SEWD PROGRESSION OF ENERGY
ASSOC WITH THE COMPACT UPR LOW JUST N OF THE NRN PLAINS AS OF THE
START OF THE PERIOD EARLY SAT.  ON THE POSITIVE SIDE THERE APPEARS
TO BE SOME CONVERGENCE TOWARD THE IDEA OF MAINTAINING REASONABLE
DEFINITION TO THE ENERGY AS IT DROPS SEWD TOWARD THE GRTLKS VERSUS
HAVING IT SHEARED AS SPORADICALLY FCST BY SOME PRIMARILY NON-GFS
MODEL RUNS.  GFS RUNS HAVE TENDED TO BE IN THE FASTER PART OF THE
ENVELOPE AND THE ECMWF SLOWER.  AS AMPLIFICATION TAKES PLACE IN
THE FIRST HALF OF THE PERIOD THE SFC PATTERN MAY BE SOMEWHAT
AMORPHOUS WITH MULTIPLE SFC LOWS THOUGH FAVORING BEST DEFINITION
OVER THE GRTLKS.  LOW PRESSURE IS EXPECTED TO
CONSOLIDATE/STRENGTHEN AS IT LIFTS NEWD FROM THE GRTLKS MON-WED.
PREFER AN EVEN WEIGHTING OF OPERATIONAL MODEL DETAIL AND AGREEABLE
LARGER SCALE EVOLUTION OF THE ENSEMBLE MEANS.  INITIAL TIMING OF
THE 18Z GFS IS LESS EXTREME THAN THE 12Z RUN SO THE 18Z GFS/12Z
ECMWF SOLNS ARE BLENDED WITH THE 18Z GEFS/12Z ECMWF MEANS.  THE
NEW 00Z GFS/UKMET/CMC FALL IN THE MIDDLE TO FASTER HALF OF THE
SPREAD WITH THE INITIAL UPR LOW AND COMPARE FAIRLY WELL TO
ESTABLISHED CONSENSUS BY DAY 5 MON.

GIVEN STRENGTH OF THE WRN CONUS-CNTRL CANADA RIDGE... SLOWER STILL
LOOKS BETTER WITH THE UPR LOW DRIFTING OVER THE NERN PAC.
BLENDING THE ENSEMBLE MEANS WITH THE 18Z GFS/12Z ECMWF HELPS TO
TONE DOWN HGT FALLS NEARING THE PAC NW COAST DAY 7 WED IN THE
LATTER SOLNS.  STILL THEY ARE MUCH CLOSER TO THE MEANS THAN THE
VERY PROGRESSIVE 12Z GFS.


...SENSIBLE WEATHER HIGHLIGHTS...

EXPECT COOLER TEMPS TO SPREAD SEWD FROM THE NRN TIER DURING THE
PERIOD... LEAVING MUCH OF THE ERN 2/3 OF THE CONUS WITH BELOW
AVERAGE READINGS BY THE MIDDLE OF NEXT WEEK.  IN GENERAL MAX TEMPS
SHOULD BE SOMEWHAT FARTHER BELOW NORMAL THAN THE MINS THOUGH IN
MOST CASES LIKELY NOT AS EXTREME AS WITH THE PREVIOUS SURGE OF
COOL AIR.  AHEAD OF THIS COOLING TREND ONE OR MORE SFC
LOWS/FRONTAL SYSTEMS WILL SUPPORT AREAS OF RNFL/TSTMS OVER THE ERN
THIRD OF THE CONUS FROM THE WEEKEND INTO EARLY NEXT WEEK...
SETTLING TOWARD THE SERN/GULF COAST THEREAFTER.  SOME LINGERING
ACTIVITY MAY CONTINUE FOR A TIME IN THE VICINITY OF THE GRTLKS
NEAR THE CORE OF THE UPR TROUGH.  MEANWHILE LOW LVL UPSLOPE FLOW
BEHIND THE TRAILING PART OF THE MAIN SFC FRONT MAY INCREASE
POTENTIAL FOR LOCALLY HVY RNFL OVER PORTIONS OF CO/NM.  OVER THE
INTERIOR WEST... TEMPS SHOULD BE NEAR TO ABOVE NORMAL WITH HIGHEST
ANOMALIES TENDING TO BE OVER THE NORTHWEST.  GUIDANCE EXPECTS MOST
CONVECTION TO BE ON THE LGT/SCT SIDE BUT THE COMBINATION OF AN
IMPULSE INITIALLY TO THE S OF THE UPR HIGH ALONG WITH ERN PAC
ENERGY COULD ENHANCE ACTIVITY AT SOME LOCATIONS.

RAUSCH

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