Prognostic Meteorological Discussion
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000
FXUS02 KWBC 020648
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
247 AM EDT TUE JUN 02 2015

VALID 12Z FRI JUN 05 2015 - 12Z TUE JUN 09 2015

...OVERVIEW...

PRIMARY FOCUS OVER THE WEST WILL BE ON THE UPR LOW EXPECTED TO
LINGER OVER/NEAR CALIFORNIA FROM LATE THIS WEEK INTO THE WEEKEND
BEFORE FINALLY DRIFTING NEWD INTO THE GRTBASIN... AND TO WHAT
EXTENT FLOW BTWN THIS FEATURE AND A SRN PLAINS/NERN MEXICO RIDGE
WILL BRING ERN PAC TROPICAL MSTR INTO THE SOUTHWEST AND/OR
ROCKIES.  ONE OR MORE SHRTWV IMPULSES EJECTING FROM THE OVERALL
WRN TROUGH AND ROUNDING THE PLAINS RIDGE WILL ENCOURAGE EPISODES
OF CONVECTION WHILE FARTHER N/E THE GUIDANCE CONTINUES TO POINT
TOWARD AMPLIFICATION OF THE ERN NOAM MEAN TROUGH WHICH OVER THE
PAST COUPLE DAYS HAS HAD TELECONNECTION SUPPORT RELATIVE TO THE
CORE OF POSITIVE HGT ANOMALIES FCST TO BE OVER SRN BC TOWARD THE
END OF THE PERIOD.


...GUIDANCE EVALUATION/PREFERENCES...

00Z UKMET/CMC RUNS STILL OFFER SOME DIFFERING IDEAS BUT OVER THE
PAST DAY GFS/GEFS AND ECMWF/ECMWF MEAN RUNS HAVE CONVERGED QUITE
WELL REGARDING THE EVOLUTION OF THE CA UPR LOW FOR MOST OF THE
PERIOD... WITH GFS TRENDS BRING THE FEATURE FROM AN OFFSHORE TRACK
TO ALONG THE COAST AND ECMWF TRENDS BEING MODESTLY IN THE OPPOSITE
DIRECTION.  AT THE SAME TIME THERE IS DECREASING SPREAD IN HOW
MUCH MSTR FROM WEAKENING TROPICAL CYCLONE ANDRES REACHES THE SWRN
STATES AS 18Z/00Z GFS RUNS SHOW LESS MSTR REACHING SRN CA THAN IN
EARLIER RUNS.  THE MSTR FEED FROM BLANCA MAY END UP BEING MORE
SIGNIFICANT GIVEN A CURRENT TRACK FCST HEADING TOWARD EXTREME SRN
BAJA CALIF AND STRONGER FLOW ALOFT EXTENDING INTO THE WRN STATES
FROM THIS SYSTEM.  THROUGH THE 18Z CYCLE THE 18Z GFS/GEFS MEAN AND
12Z ECMWF/ECMWF MEAN/NAEFS MEAN OFFERED A GOOD CONSENSUS SOLN FOR
MOST OF THE PERIOD OVER THE WEST.  CONSULT NHC PRODUCTS FOR LATEST
INFO REGARDING ANDRES AND BLANCA.

FROM FRI INTO THE WEEKEND GUIDANCE IS FAIRLY AGREEABLE WITH THE
COLD FRONT PUSHING SEWD THROUGH THE ERN STATES AHEAD OF SERN
CANADA/NEW ENGLAND HIGH PRESSURE.  MULTI-DAY TRENDS HAVE BEEN TO
SUPPRESS ANY FRONTAL WAVES BUT THE RECENT CMC RUNS AND NOW THE 00Z
UKMET OFFER POTENTIAL THAT SHRTWV ENERGY EJECTING FROM THE INITIAL
WRN TROUGH IN THE SHORT RANGE COULD STILL LEAD TO A FARTHER NWD
SFC WAVE.  FOR NOW PREFER THE MORE SUPPRESSED MAJORITY GIVEN
AFOREMENTIONED TRENDS AND UPR PATTERN THAT APPEARS MORE SUPPORTIVE
OF THAT SCENARIO.

AMONG OPERATIONAL RUNS THE 18Z GFS/12Z ECMWF GENERALLY OFFER THE
BEST COMPARISON TO THE ENSEMBLE MEANS FOR THE HANDLING OF WRN
CANADA/NRN ROCKIES SHRTWV ENERGY THAT WILL SUPPORT SRN CANADA LOW
PRES AND TRAILING FRONT THAT WILL EXTEND INTO THE CONUS.  ENSMEANS
HAVE TRENDED STRONGER WITH THIS SYSTEM OVER THE PAST DAY...
ALLOWING FOR ENOUGH CONFIDENCE TO INCORPORATE SOME OPERATIONAL
DATA TO A RECOMMENDED BLEND.

DETAILS ALONG AND OFFSHORE THE EAST COAST CONTINUE TO SHOW SOME
VARIABILITY IN RESPONSE TO THE DIFFUSE NATURE OF THE INITIAL ERN
TROUGH... WITH ONE BUNDLE OF ENERGY BEING EJECTED AS UPSTREAM MS
VLY ENERGY FEEDS INTO THE MEAN TROUGH.  OF LATE THE CMC HAS BEEN
MOST ENTHUSIASTIC WITH WRN CARIBBEAN INTO WRN ATLC TROPICAL
DEVELOPMENT WITH GFS/GEFS SOLNS TENDING TO BE MORE DEFINED THAN
REMAINING SOLNS.  THE 00Z GFS/GEFS MEAN HAS TRENDED WEAKER.

THE MANUAL FCST STARTED WITH A BLEND OF THE 12Z ECMWF/ECMWF
MEAN/NAEFS MEAN THAT REPRESENTED THE BEST MODEL/ENSEMBLE CLUSTER
FOR FEATURES OF INTEREST.  THE 18Z GFS COULD ALSO BE ADDED OVER
THE CONUS BUT WAS ULTIMATELY EXCLUDED FROM THE BLEND DUE TO LACK
OF CONFIDENCE IN ITS DETAILS OFF THE EAST COAST.


...SENSIBLE WEATHER HIGHLIGHTS...

COMBINATION OF THE CALIFORNIA UPR LOW AND LEADING FLOW SHOULD
BRING PERIODS OF ENHANCED RNFL FROM PARTS OF NRN-CNTRL CA ACROSS A
LARGER PORTION OF THE WEST GOING EWD INTO THE ROCKIES.
SIGNIFICANT UNCERTAINTIES REMAIN WITH THE SPECIFICS OF ERN PAC
TROPICAL MSTR THAT MAY FLOW INTO THE WEST AND SUPPORT HEAVIER
RNFL.  CURRENTLY BEST POTENTIAL FOR SOME INFLUENCE FROM THIS MSTR
SHOULD BE OVER THE FOUR CORNERS REGION AND SRN-CNTRL ROCKIES BUT A
SUBTLE SHIFT IN FLOW ALOFT COULD ALTER THIS TARGET.  MEANWHILE A
COUPLE ERN CONUS FRONTS EXTENDING BACK INTO THE PLAINS ALONG WITH
ONE OR MORE SHRTWV IMPULSES ROUNDING THE PLAINS RIDGE ALOFT SHOULD
HELP TO FOCUS AREAS OF CONVECTION FROM THE CNTRL HALF OF THE HIGH
PLAINS INTO PORTIONS OF THE EAST.  THE DIFFUSE UPR TROUGH OVER THE
EAST SHOULD ALSO PROMOTE SOME DIURNALLY FAVORED CONVECTION
ESPECIALLY FRI-SUN.  THE PATTERN ALOFT WILL PROMOTE VERY WARM
TEMPS OVER THE NWRN STATES WITH MULTIPLE DAYS OF PLUS 10-20F
ANOMALIES.  SOME DAILY RECORDS ARE POSSIBLE... CURRENTLY MORE
LIKELY TO BE FOR WARM LOWS VERSUS DAYTIME HIGHS.  ELSEWHERE TEMPS
SHOULD BE FAIRLY MODERATE. CNTRL-SRN PARTS OF THE WEST SHOULD TEND
TO SEE BELOW NORMAL HIGHS WHILE MOST AREAS ACROSS THE CONUS SHOULD
LEAN ABOVE NORMAL FOR MORNING LOWS. CNTRL-ERN CONUS HIGHS WILL
DEPEND ON SYSTEM/FRONTAL PROGRESSION AND TIMING OF CONVECTION/RNFL.

RAUSCH

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