Prognostic Meteorological Discussion
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000
FXUS02 KWBC 211622
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1221 PM 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 AN UPPER HIGH
CLOSING OFF OVER NORTH CENTRAL CANADA THIS WEEKEND.  THE ENERGY/OR
A PORTION OF THE ENERGY 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 CONTINUITY AND THE SIMILAR 00Z GEFS/ECMWF ENSEMBLE
MEAN GUIDANCE.

ALSO OF NOTE...THE 00Z ECMWF RESOLVES THE NEXT CLOSED LOW DROPPING
DOWN FROM THE GULF OF ALASKA SLIGHTLY DIFFERENT THAN OTHER
DETERMINISTIC GUIDANCE...AND HAS BEEN HAVING RUN TO RUN CONTINUITY
ISSUES WITH THIS FEATURE...SO THE DETERMINISTIC ECMWF WAS
ELIMINATED FROM THE FORECAST BLEND.


...SENSIBLE WEATHER HIGHLIGHTS...

SHOWERS AND THUNDERSTORMS WILL LIGHT UP ALONG/AHEAD OF A STRONG
COLD FRONT CROSSING THE APPALACHIANS AND CLEARING THE
NORTHEAST/MID-ATLANTIC COAST LATE THIS WEEK.  HIGH PRESSURE
SPREADING IN BEHIND THE FRONT SHOULD BRING BELOW NORMAL
TEMPERATURES ACROSS THE MID-WEST...GREAT LAKES...AND OHIO VALLEY.
THE TAIL END OF THE BOUNDARY IS EXPECTED TO LINGER OVER THE
SOUTHERN TIER BEFORE SURGING NORTH AS A WARM FRONT.  THE
RETREATING FRONT...IN COMBINATION WITH ANOTHER STRONG COLD FRONT
PUSHING OUT OF THE NORTH CENTRAL U.S. COULD LEAD TO HEAVY RAIN AND
THUNDERSTORMS ACROSS THE UPPER MIDWEST/MIDDLE MISSISSIPPI VALLEY
THIS WEEKEND...SHIFTING TO THE TENNESSEE VALLEY/NORTHERN
MID-ATLANTIC REGION EARLY NEXT WEEK.

OUT WEST...ABOVE NORMAL TEMPERATURES WILL PERSIST BENEATH THE
RIDGE ANCHORED OVER THE FOUR CORNERS REGION.  AS THE RIDGE BUILDS
NORTHWARD EARLY NEXT WEEK...THE POSITIVE ANOMALIES WILL SPREAD
NORTH INTO THE NORTHERN ROCKIES/INTERMOUNTAIN WEST.


GERHARDT

$$





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