Prognostic Meteorological Discussion
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FXUS02 KWBC 010630
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
230 AM EDT WED OCT 01 2014

VALID 12Z SAT OCT 04 2014 - 12Z WED OCT 08 2014

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

FOR MOST OF THE PERIOD THERE IS LITTLE CHANGE IN THE FCST OF AN
AMPLIFIED WRN RIDGE/ERN TROUGH MEAN PATTERN THAT SHOULD HAVE ABOVE
AVG PREDICTABILITY IN THE LARGE SCALE.  HOWEVER SOME UNCERTAINTY
CONTINUES TO ARISE REGARDING HOW MUCH UPSTREAM PAC ENERGY MAY
BEGIN TO FLATTEN THE PATTERN BY THE MIDDLE OF NEXT WEEK.  WITHIN
THE ERN MEAN TROUGH THERE ARE SMALLER SCALE SHRTWV DETAIL ISSUES
THAT LEAD TO DIFFICULTY IN RESOLVING ASSOC FRONTAL SYSTEMS
MID-LATE PERIOD.  WITH SOME DETAIL DIFFS PRESENT EVEN DURING THE
WEEKEND AND A COMPROMISE STILL LOOKING BEST FOR RESOLVING
AMPLITUDE DIFFS LATE... PREFER TO START WITH AN EVEN BLEND OF THE
18Z GEFS/12Z ECMWF MEANS THROUGH THE DAYS 3-7 SAT-WED TIME FRAME.


LATE IN THE PERIOD THE ECMWF MEAN HAS TRENDED SOMEWHAT SHARPER/WWD
WITH ITS MODEST TROUGHING THAT DEVELOPS OVER THE NORTHWEST.
GEFS/CMC MEANS HAVE TENDED TO HOLD ONTO HIGHER HGTS OVER THIS AREA
DURING THE PAST COUPLE DAYS.  THE FULL ENSEMBLE SPREAD OVER THE
ERN PAC/WRN NOAM BECOMES FAIRLY WIDE BY NEXT TUE-WED SO CONFIDENCE
IS NOT ESPECIALLY GREAT.  TELECONNECTIONS RELATIVE TO D+8 MEANS
SHOWING A STRONG CORE OF NEGATIVE HGT ANOMALIES OVER THE CNTRL PAC
SUGGEST THAT ENERGY REACHING THE NORTHWEST SHOULD FALL INTO A
POSITIVELY TILTED MEAN TROUGH SOMEWHAT DOWNSTREAM FROM THE 12Z
ECMWF MEAN... FAVORING AT LEAST HALF WEIGHTING OF THE GEFS IDEA.
THE 12Z ECMWF AND ITS PRIOR RUN OFFER YET ANOTHER IDEA WITH A DEEP
CLOSED LOW OVER THE NERN PAC.

FARTHER EWD... THERE HAS BEEN A DEEPER TREND WITH THE CORE OF THE
TROUGH ALOFT NEAR THE START OF THE PERIOD WITH SOME HGTS FCST TO
BE AT LEAST 3-4 STDEVS BELOW NORMAL ON SAT.  ANOMALIES SHOULD
BECOME SOMEWHAT LESS EXTREME THEREAFTER BUT WITH THE MEAN TROUGH
REMAINING AMPLIFIED INTO EARLY NEXT WEEK.  THE 18Z GFS BECAME
QUITE AMPLIFIED IN THE EAST BY NEXT WEEK WHILE THE 00Z RUN AGREES
BETTER WITH THE ENSEMBLE MEANS.


...SENSIBLE WEATHER HIGHLIGHTS...

THE GREATEST COVERAGE OF PCPN SHOULD BE OVER THE NERN QUADRANT OF
THE CONUS... EXTENDING FOR A TIME INTO THE TN VLY.  AT FIRST A
LEADING COLD FRONT NEAR THE EAST COAST WILL FOCUS RNFL INTO NEW
ENG WHILE COLD AIR ALOFT WITHIN THE SUPPORTING UPR TROUGH SHOULD
ENCOURAGE SHOWERY WEATHER OVER THE GRTLKS.  DEPTH OF THE UPR
SYSTEM COULD BE SUFFICIENT TO GENERATE A LITTLE SNOW AT SOME
LOCATIONS NEAR THE UPR GRTLKS DURING THE WEEKEND.  ONE OR MORE
TRAILING UPSTREAM IMPULSES/SFC SYSTEMS SHOULD ALSO BE ACCOMPANIED
BY AREAS OF RNFL.  ELSEWHERE RNFL SHOULD BE CONFINED TO FL AS THE
INITIAL E COAST FRONT STALLS JUST S OF THE STATE... EXTREME SRN
TX... AND TO THE NRN PAC NW WHICH MAY SEE LGT AMTS.  EXPECT QUITE
CHILLY DAYTIME TEMPS OVER THE MIDWEST EARLY IN THE PERIOD WITH
READINGS 10-20F BELOW NORMAL.  READINGS SHOULD TREND CLOSER TO
NORMAL BY THE MIDDLE OF NEXT WEEK.  MEANWHILE THE EVOLUTION ALOFT
WILL SUPPORT VERY WARM TEMPS OVER THE WEST INTO THE START OF NEXT
WEEK BEFORE A COOLING TREND... WITH ABOVE NORMAL READINGS
EXTENDING INTO THE CNTRL-SRN PLAINS BY THE LATTER HALF OF THE
PERIOD.

RAUSCH

$$




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