Prognostic Meteorological Discussion
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000
FXUS02 KWBC 281559
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1058 AM EST WED JAN 28 2015

VALID 12Z SAT JAN 31 2015 - 12Z WED FEB 04 2015

...OVERVIEW...

LATEST GUIDANCE IS AGREEABLE AND CONSISTENT WITH THE IDEA OF
MAINTAINING A MEAN RIDGE NEAR THE WEST COAST... WITH ONLY BRIEF
FLATTENING AROUND MID-PERIOD AS SOME PACIFIC ENERGY FILTERS
THROUGH AND HEADS INTO A BROADENING CONUS MEAN TROUGH.  THE CONUS
MEAN TROUGH SEEN IN MOST SOLNS BY THE MIDDLE OF NEXT WEEK HAS
BETTER THAN AVG CONFIDENCE IN LIGHT OF CONSISTENCY WITH
TELECONNECTIONS RELATIVE TO A CORE OF POSITIVE HGT ANOMALIES NEAR
KAMCHATKA AND NEGATIVE HGT ANOMALIES IN THE E-CNTRL PAC AS SEEN IN
D+8 MULTI-DAY MEAN CHARTS.  AHEAD OF THIS EVOLUTION HOWEVER...
MODEL/ENSEMBLE SPREAD SUGGESTS CONTINUED LESS THAN AVG CONFIDENCE
WITH THE PARTICULARS OF A SYSTEM AFFECTING AREAS FROM THE FOUR
CORNERS/PLAINS INTO THE EAST SAT-MON.

...GUIDANCE/UNCERTAINTY EVALUATION AND PREFERENCES...

THERE CONTINUE TO BE VARIOUS SOURCES OF UNCERTAINTY FOR THE SYSTEM
EXPECTED TO AFFECT THE CNTRL-ERN STATES FROM THE WEEKEND INTO THE
START OF NEXT WEEK.  SUPPORTING ENERGY AMPLIFYING INTO THE PLAINS
DURING THE WEEKEND ORIGINATES FROM A COMBINATION OF FLAT FLOW
HEADING INTO BC AND SHEARED ENERGY OVER ALASKA IN THE SHORT RANGE.
 THESE IMPULSES DO NOT REACH WRN CANADA UNTIL LATE FRI SO IT MAY
TAKE UNTIL AT LEAST THEN TO GET A REASONABLE ANALYSIS OF THIS
ENERGY.  BEYOND THIS ISSUE IS THE QUESTION OF NRN STREAM TROUGH
AMPLITUDE OVER THE CONUS AND HOW MUCH INTERACTION THERE IS WITH
THE TROUGH OVER THE SWRN CONUS/NRN MEXICO.  GREATER NRN STREAM
AMPLITUDE/MORE INTERACTION AS PER 00Z GFS/CMC RUNS LEAD TO A
SLOWER/NWWD SFC SYSTEM IN CONTRAST TO THE FLAT NRN STREAM
SHRTWV/WEAK AND FAST SFC WAVE OF THE 00Z UKMET.  THE UKMET/CMC
HAVE ESSENTIALLY SWITCHED PLACES RELATIVE TO THE SOLN ENVELOPE
COMPARED TO 24 HRS AGO.  MEANWHILE THE FULL ARRAY OF ENSEMBLE SFC
LOWS BY LATE SUN ONWARD IS QUITE BROAD WITH LITTLE CLUSTERING
ASIDE FROM SUGGESTING THE BEST PROBABILITY WOULD BE FOR THE SYSTEM
TO BE JUST OFF THE NERN COAST BY 00Z TUE.  ON THE POSITIVE SIDE...
TAKEN AS A WHOLE THE PAST 24 HRS OR SO OF GUIDANCE HAS STABILIZED
ON A SLOWER/STRONGER EVOLUTION THAN SEEN IN EARLIER CONSENSUS.
FOR THIS UPDATE ULTIMATELY PREFER TO EMPHASIZE A BLEND OF THE 06Z
GFS/00Z ECMWF/00Z GEFS MEAN WITH LESS WEIGHTING ON THE FLATTER 00Z
ECMWF MEAN.  THIS SOLN YIELDS A GOOD INTERMEDIATE SFC TRACK WHICH
COMPARES WELL WITH LAGGED AVG FCSTS INCORPORATING RECENT GFS/ECMWF
RUNS... FROM THE OH VLY 00Z MON TO THE DELMARVA/SERN PA 12Z MON TO
JUST OFF THE NRN NEW ENGLAND COAST 00Z TUE.  THE FAVORED BLEND
REPRESENTS CONSENSUS WELL OVER THE WRN STATES WHERE RIDGING ALOFT
WILL FLATTEN AS WEAK ENERGY ALOFT COMES INLAND.

GUIDANCE HAS BEEN OSCILLATING SOMEWHAT REGARDING AT WHAT POINT
THIS INCOMING ERN PAC ENERGY AMPLIFIES UPON PASSING THE MEAN RIDGE
AXIS.  24 HRS AGO GUIDANCE HAD BEEN TRENDING TOWARD EARLIER
AMPLIFICATION OVER THE WEST BUT NOW THOSE TRENDS HAVE REVERSED TO
A FARTHER DOWNSTREAM CONSENSUS FROM A COUPLE DAYS AGO.  FROM THE
MULTI-DAY MEAN PERSPECTIVE EITHER OPTION COULD END UP LEADING TO
THE TELECONNECTION-FAVORED CONUS TROUGH.  GOOD AGREEMENT AMONG
LATEST GEFS/ECMWF/CMC MEANS WOULD FAVOR AN ENSEMBLE MEAN EMPHASIS
LATE IN THE PERIOD... WITH THE 06Z GFS PSBLY BECOMING TOO
AMPLIFIED WITH WRN TROUGHING AND 00Z ECMWF SOMEWHAT SLOWER/SHARPER
WITH ITS SRN CANADA/NRN TIER CONUS TROUGH.

ONE FINAL ISSUE THAT WILL HOPEFULLY GAIN CLARITY IN UPCOMING
CYCLES IS THE ULTIMATE EVOLUTION OF WHAT ENERGY REMAINS FROM THE
INITIAL SWRN CONUS/NWRN MEXICO TROUGH-UPR LOW.  RECENT GFS/ECMWF
RUNS SUGGEST EJECTION OF THIS FEATURE MAY AFFECT EXTREME SRN TX
AND PARTS OF THE SOUTHEAST.  INDIVIDUAL MODEL RUNS ARE CURRENTLY
TOO DIVERSE TO DEPICT A WELL DEFINED FEATURE BY LATE IN THE PERIOD
BUT AT LEAST THE ENSEMBLE MEANS DO DEPICT THE PCPN POTENTIAL OVER
THE AFOREMENTIONED AREAS.


...SENSIBLE WEATHER HIGHLIGHTS...

WINTRY PCPN AND STRONG WINDS OVER NEW ENGLAND SHOULD BE TAPERING
OFF EARLY IN THE PERIOD WITH THE DEPARTURE OF A VIGOROUS SYSTEM
FCST TO BE JUST E OF MAINE AS OF EARLY SAT.  SPECIFICS REMAIN
UNCERTAIN BUT IN GENERAL CONTINUE TO EXPECT A BROAD SHIELD OF PCPN
TO SPREAD FROM THE FOUR CORNERS THROUGH THE PLAINS AND INTO THE
EAST SAT-SUN... MOST LIKELY CLEARING MOST OF THE EAST EARLY NEXT
WEEK.  HIGHEST PROBABILITY OF MEANINGFUL SNOW/WINTRY PCPN SHOULD
BE ALONG AN AXIS FROM THE SRN ROCKIES THROUGH THE OH VLY/SRN
GRTLKS INTO NEW ENGLAND WITH MULTIPLE PCPN TYPES/CHANGEOVER PSBL
JUST S OF THIS AREA.  SOME AREAS OF ENHANCED PCPN ARE PSBL IN BOTH
THE COLD AND WARM SECTORS OF THIS SYSTEM.  THEN EXPECT A DRYING
TREND ASIDE FROM A PERIOD OF LAKE EFFECT SNOW... AND PSBLY SOME
RNFL FROM EXTREME SRN TX INTO PARTS OF THE SE IN ASSOC WITH UPR
ENERGY EJECTING FROM MEXICO.  MEANWHILE AN AREA OF MSTR WILL
SPREAD INTO THE NORTHWEST AROUND SUN AND PUSH EWD/SEWD WITH TIME.
IN GENERAL AMTS SHOULD BE MODERATE BUT LOCALLY ENHANCED TOTALS IN
FAVORED TERRAIN MAY BE PSBL.  THE LARGE SCALE PATTERN SHOULD FAVOR
NEAR TO ABOVE NORMAL TEMPS OVER THE WEST AND COLDER THAN AVG
READINGS CNTRL-ERN AREAS.  MOST EXTREME ANOMALIES SHOULD BE AT
LEAST 10-20F ON THE NEGATIVE SIDE... OVER THE NORTHEAST SAT AND
WITHIN ANOTHER COLD AIRMASS PROGRESSING FROM THE PLAINS INTO THE
EAST SUN-TUE.

RAUSCH

$$





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