Preliminary Forecasts
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FXUS02 KWNH 020627
PREEPD

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
226 AM EDT THU OCT 02 2014

VALID 12Z SUN OCT 05 2014 - 12Z THU OCT 09 2014

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

THE SUN-THU PERIOD WILL SEE A GRADUAL FLATTENING OF THE MEAN
PATTERN... WITH A TRANSITION FROM A STRONG WRN RIDGE/DEEP ERN
TROUGH TOWARD A POSITIVELY TILTED LOWER AMPLITUDE TROUGH ALIGNED
FROM THE NRN TIER INTO W-CNTRL STATES.  EXTRAPOLATION OF THIS
LATTER PATTERN BEYOND DAY 7 COMPARES WELL TO
TELECONNECTION-FAVORED FLOW RELATIVE TO A CORE OF NEGATIVE HGT
ANOMALIES OVER THE NRN PAC NEAR 180 LONGITUDE.  AS HAS BEEN THE
CASE IN PAST DAYS THERE ARE MEDIUM TO SMALLER SCALE DETAIL ISSUES
WITHIN THE AGREED UPON HIGHER AMPLITUDE FLOW EARLY IN THE FCST AND
THEN SOME INDIVIDUAL MODEL RUNS/ENSEMBLE MEMBERS BEGIN TO DIVERGE
WITH LARGER SCALE ASPECTS OF ERN PAC/WRN NOAM FLOW.  THE LIKELY
INCORPORATION OF RECURVING TYPHOON PHANFONE INTO NRN PAC FLOW MAY
PROVIDE AN ADDED COMPLEXITY LATE IN THE PERIOD.


DURING DAYS 3-5 SUN-TUE A BLEND OF THE 18Z GEFS/12Z ECMWF MEANS
WITH SLIGHTLY LESSER WEIGHTING OF THE 18Z GFS/12Z ECMWF PROVIDES A
GOOD OVERALL AVG OF SOLNS WHERE DIFFS EXIST BETWEEN THE MEANS AND
SOME OPERATIONAL MODEL RUNS... PARTICULARLY WITH THE POSN OF SFC
LOW PRESSURE MEANDERING BETWEEN THE GRTLKS AND HUDSON BAY.  THERE
IS REASONABLE AGREEMENT THAT THE UPR TROUGH SHOULD BECOME SHARPER
BY DAY 5 TUE WITH ECMWF/ECMWF MEAN RUNS SHOWING MORE STABILITY FOR
THIS ASPECT OF THE FCST.

BY DAYS 6-7 WED-THU... A SLIGHTLY FASTER/BROADER TREND FOR THE
DEVELOPING NRN TIER TROUGH IN THE ECMWF MEAN LEADS TO SIMILAR
SOLNS IN THE LATEST GEFS/ECMWF MEANS WITH THE 12Z CMC MEAN SIMILAR
AS WELL.  IN ADDITION ENSEMBLE MEAN AGREEMENT IS GOOD FOR EJECTION
OF THE ERN TROUGH.  THE PAST FEW ECMWF RUNS HAVE GENERALLY STRAYED
MORE FROM THE ENSEMBLE MEANS FOR NERN PAC/NWRN NOAM FLOW THAN GFS
RUNS.  BOTH STILL SHOW ENOUGH DIFFS TO RECOMMEND THE 18Z GEFS/12Z
ECMWF MEANS AS THE STARTING POINT FOR DAYS 6-7.

CONSULT NHC PRODUCTS FOR THE LATEST INFO REGARDING TROPICAL
DEPRESSION NINETEEN-E WHICH IS THE LATEST IN THE SERIES OF ERN PAC
SYSTEMS FCST TO TRACK W OF BAJA CALIF.  CURRENTLY ONLY A MINORITY
OF GUIDANCE BRINGS ANY MEANINGFUL MSTR N OF THE US-MEXICO BORDER
BUT TYPICAL GUIDANCE ERRORS AT THE MEDIUM RANGE TIME FRAME REQUIRE
MONITORING OF THIS SYSTEM.


...SENSIBLE WEATHER HIGHLIGHTS...

AT THE START OF THE PERIOD ON SUN EXPECT VERY WARM TEMPS OVER THE
WEST AND CHILLY READINGS OVER THE EAST WITH SOME ANOMALIES
REACHING AT LEAST PLUS/MINUS 10-15F FROM NORMAL RESPECTIVELY.
EVOLUTION OF THE PATTERN ALOFT WILL SHIFT THE WARMTH INTO THE
CNTRL-SRN PLAINS AND EVENTUALLY THE EAST TO SOME DEGREE... WHILE A
COLD FRONT DROPPING INTO THE NRN TIER MAY PUSH HIGHS 10F OR MORE
BELOW NORMAL OVER THE EXTREME NRN PLAINS BY NEXT THU.  EXPECT
SHOWERY CONDS OVER THE GRTLKS AND VICINITY SUN-TUE UNDER THE CORE
OF THE UPR TROUGH.  SHARPENING MID LVL ENERGY MAY PROMOTE WHAT
SHOULD BE A BRIEF AND MODEST INCREASE IN MSTR FROM THE GULF COAST
INTO THE OH VLY EARLY NEXT WEEK.  DEVELOPMENT OF THE NRN TIER
TROUGH ALOFT MAY BEGIN TO INCREASE THE COVERAGE OF RNFL OVER PARTS
OF THE PLAINS/MIDWEST BY NEXT THU.

RAUSCH

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