Prognostic Meteorological Discussion
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000
FXUS02 KWBC 211559
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1158 AM EDT MON JUL 21 2014

VALID 12Z THU JUL 24 2014 - 12Z MON JUL 28 2014

...GENERAL OVERVIEW...

AN EXPANSIVE UPPER RIDGE WILL REMAINED ANCHORED OVER THE FOUR
CORNERS REGION LATE THIS WEEK AND INTO EARLY NEXT WEEK.  VIGOROUS
CLOSED ENERGY ALOFT WILL LIFT FROM THE NORTHWESTERN U.S. TO
ALBERTA/SASKATCHEWAN THURSDAY AND FRIDAY...BEFORE SQUEEZING
EASTWARD BETWEEN THE RIDGE OVER THE FOUR CORNERS AND A HIGH
BUILDING IN OVER NORTH CENTRAL CANADA THIS WEEKEND.  THE ENERGY/OR
A PORTION OF IT SHOULD DIVE SOUTHEASTWARD INTO THE UPPER
MIDWEST/GREAT LAKES EARLY NEXT WEEK AND HELP REINFORCE TROUGHING
IN PLACE OVER THE EASTERN U.S..  ALSO BY EARLY NEXT WEEK...ANOTHER
CLOSED LOW IS EXPECTED TO DROP SOUTH FROM THE GULF OF ALASKA WHILE
THE UPPER RIDGE OVER THE FOUR CORNERS BUILDS NORTHWARD INTO THE
NORTHERN ROCKIES/INTERMOUNTAIN WEST.

THE PRONOUNCED WRN RIDGE/ERN TROUGH PATTERN HAS MADE FEW
APPEARANCES DURING THE JULY/AUG TIME FRAME IN RECENT YEARS BEFORE
2014.  HOWEVER COMPOSITE ANALOGS BASED ON SOME OF THE D+8
MULTI-DAY MEANS VALID AT THE START OF NEXT WEEK REVEAL MULTIPLE
INSTANCES OF A SIMILAR PATTERN IN JULY AND/OR AUG OF EARLIER
YEARS.  IN REVERSE CHRONOLOGICAL ORDER THESE INCLUDE
2003..2000..1996..1994..1993..1990 AND 1989.  AFTER A LENGTHY GAP
THE YEARS 1969..1967..1962 AND 1956 ALSO FEATURED THIS TYPE OF
PATTERN AT SOME POINT IN JULY AND/OR AUG. -RAUSCH


...GUIDANCE EVALUATION/MODEL PREFERENCES...

MODELS ARE IN VERY GOOD AGREEMENT WITH THE MEAN FLOW PATTERN OVER
THE CONUS FOR THE DAY 3-7 FORECAST...BUT STILL APPEAR TO BE
WORKING OUT THE DETAILS WITH THE EVOLUTION OF THE ENERGY SQUEEZING
BETWEEN THE RIDGE IN THE FOUR CORNERS AND NORTH CENTRAL CANADA
THIS WEEKEND.  THIS RESULTS IN VARYING SOLUTIONS FOR HOW THE
ENERGY DIVES DOWN INTO UPPER MIDWEST/GREAT LAKES AND REINFORCES
THE MEAN EASTERN U.S. TROUGH EARLY NEXT WEEK.  THE 00Z GFS/ECMWF
BOTH SHIFTED TO A MORE PROGRESSIVE SOLUTION...LEADING TO A TROUGH
AXIS FARTHER EAST THAN THEIR PAST FEW RUNS.  HOWEVER...THE 06Z GFS
REVERTED BACK TO A SLIGHTLY SLOWER/MORE HELD BACK SOLUTION.  WITH
NO CLEAR INDICATION OF A TREND...THE WPC FORECAST WAS WEIGHTED
HEAVILY TOWARDS THE SIMILAR 00Z GEFS/ECMWF ENSEMBLE MEAN GUIDANCE.



GERHARDT

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