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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0518Z Jul 26, 2014)
 
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Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
118 AM EDT SAT JUL 26 2014

VALID 12Z TUE JUL 29 2014 - 12Z SAT AUG 02 2014

...AMPLIFIED PATTERN TO DELIVER ANOTHER EARLY FALL-LIKE AIRMASS TO
THE CENTRAL/EASTERN STATES...


...OVERVIEW...

DEEP TROUGH WILL BE OVER THE EASTERN THIRD OF THE CONUS TO START
THE MEDIUM RANGE PERIOD BUT THE LONGWAVE RIDGE/TROUGH ORIENTATION
WILL STAY IN PLACE INTO NEXT WEEKEND. RIDGING VIA A STRENGTHENING
UPPER HIGH MOVING NORTHWARD THROUGH THE NW ATLANTIC TOWARD
NEWFOUNDLAND WILL HELP MAINTAIN THE FAMILIAR PATTERN WITH A
WESTWARD RETROGRESSION LIKELY BY SAT AUG 2. OVER THE WEST...
RIDGING WILL STAY IN PLACE UNTIL LOWER HEIGHTS OVER THE NE PACIFIC
SLOWLY PUSH INTO BRITISH COLUMBIA... SHORTENING THE WAVELENGTH
ACROSS THE CONUS.


...GUIDANCE PREFERENCES...

THE DETERMINISTIC MODELS HAVE BEEN PERFORMING WELL SYNOPTICALLY
WHILE WAVERING A BIT ON THE DETAILS... BUT OVERALL A CONSENSUS
BLEND AMONG THE 18Z GFS/GEFS AND 12Z ECMWF/ECENS MEAN HAS PROVEN
TO BE A SOLID STARTING POINT. THE UKMET/CANADIAN EMPHASIZED A
SECOND SHORTWAVE MOVING THROUGH MICHIGAN AROUND THU THAT MAY BE
TOO STRONG IN LIGHT OF THE ENSEMBLE MEMBERS. BY FRI-SAT/D6-7 IN
THE WEST... THE ECMWF AND ITS ENSEMBLE MEMBERS ARE A BIT QUICKER
TO LOWER HEIGHTS THROUGH BRITISH COLUMBIA AND INTO THE PAC NW THAN
THE GFS AND THE GEFS MEMBERS. OPTED TO SIMPLY SPLIT THE
DIFFERENCE... WHICH WAS NOT MUCH BY DAY 7 STANDARDS... GIVEN THE
RELUCTANCE OF THE PATTERN TO MOVE MUCH AT ALL.


...SENSIBLE WEATHER HIGHLIGHTS...

WITH A SIMILAR SETUP TO THE LAST COOL AIR EVENT... AROUND JULY
14-18... MUCH OF THE SAME EFFECTS SHOULD OCCUR... THE CAVEAT BEING
THAT THIS WILL NOT BE QUITE AS STRONG AS THE LAST EVENT BUT STILL
IMPRESSIVE IN ITS OWN RIGHT. MAX TEMPS SHOULD BE NEAR 10F BELOW
CLIMO IN THE EAST BEHIND THE FRONT AND 10-20F BELOW CLIMO IN THE
SOUTHERN PLAINS MIDWEEK AFTER THE FROPA IN THE OVERRUNNING PRECIP
AREA. IN ADDITION... NW FLOW ALOFT WILL SUPPORT THE CHANCE FOR
MCV-LIKE THUNDERSTORM COMPLEX TO TRAVEL SOUTHEASTWARD THROUGH
OK/TX INTO LA/AR WED-THU. THE WEST WILL REMAIN WARM/HOT... BUT
WITH A TREND TOWARD CLIMO BY NEXT WEEKEND. COLD FRONT THAT WILL
BRING THE COOLER AIRMASS TO THE EASTERN TWO THIRDS OF THE CONUS
WILL NOT MAKE IT FAR INTO THE WESTERN ATLANTIC AS RIDGING STOPS IT
FROM MOVING EAST. ENSEMBLES ALL SHOW UPPER RIDGING PUSHING BACK
WESTWARD NEXT FRI-SAT WHICH SHOULD ALLOW THE FRONT TO MOVE WEST AS
A WARM FRONT CLOSER TO THE COAST... INCREASING THE CHANCE OF RAIN
FROM THE SOUTHEAST UP INTO NEW ENGLAND.


FRACASSO