THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


EXTENDED FORECAST DISCUSSION




EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1201 PM EDT TUE JUL 29 2014

VALID 12Z FRI AUG 01 2014 - 12Z TUE AUG 05 2014

...OVERVIEW...

THE HIGHLY AMPLIFIED TROUGH/RIDGE PATTERN BRINGING COOLER AIR INTO
THE EAST SHOULD BE WEAKENING BY THE WEEKEND... BUT WILL STILL BE
EVIDENT. MORE CLOUDS AND QPF SHOULD RETURN TO PARTS OF THE EAST AS
THE MEAN TROUGH SHIFTS WESTWARD SETTING UP MORE OF AN EASTERLY
FETCH WITH HIGH PRESSURE HEADING NORTHEASTWARD INTO THE NORTH
ATLANTIC AND A NEARLY STATIONARY FRONT SLOWLY BACKING UP TOWARD
THE EAST COAST.  A MEAN UPPER RIDGE NEAR 55 W IN THE SHORT TERM
SHOULD RETROGRADE WESTWARD BETWEEN 60 AND 70 W IN THE MEDIUM
RANGE.

...GUIDANCE PREFERENCES...

IN THE MEANS...THE GUIDANCE IS QUITE SIMILAR THROUGH DAY 5/SUNDAY
WITH A GRADUAL LOSS OF AMPLITUDE OF THE EASTERN TROUGH.  AFTER DAY
5...THE MAIN DIFFERENCES START TO GROW IN THAT THE OVERNIGHT
EUROPEAN ENSEMBLES/OPERATIONAL RUN MAINTAINS A MORE PRONOUNCED
RIDGE/TROUGH PATTERN ACROSS THE WEST/EAST THAN THE GEFS/NAEFS
MEANS WITH THE MAIN IMPLICATION THAT THE THE EUROPEAN...AND TO A
LESSER EXTENT THE CANADIAN...WILL HAVE A MORE PROGRESSIVE COLD
FRONT DIVING SOUTHEASTWARD FROM CANADA ON DAY 6 INTO 7.  THE
GEFS/NAEFS HAS A FLATTER MORE ZONAL FLOW ACROSS THE NATION ON DAYS
6 AND 7.

WITHOUT MUCH SUPPORT FOR EITHER SOLUTION HAVE TRIED TO GO
SOMETHING IN BETWEEN...BUT STILL WITH THE ECMWF SUGGESTION THAT
THE TROUGH/RIDGE PATTERN OF LATE WILL CONTINUE TO HOLD BUT NOT
WITH THE AMPLITUDE SEEN IN RECENT DAYS. 


...SENSIBLE WEATHER HIGHLIGHTS...

THE RETROGRESSION OF THE EASTERN TROUGH COULD SPELL A LENGTHY
PERIOD OF MOISTENING IN THE EAST FOLLOWING DAY 3...BUT IT DOES
APPEAR THAT EVEN THE MODEL ENSEMBLE MEANS ARE STILL SUGGESTIVE OF
A MORE PROGRESSIVE STREAM ACROSS THE NORTHEAST WHICH COULD MEAN
THAT THE MOISTENING ALONG THE EAST COAST COULD BE TEMPORARY
ESPECIALLY ACROSS THE NORTHEAST BY DAY 5 WITH A FRONT PUSHING
FARTHER EASTWARD INTO THE ATLANTIC ON DAYS 6 AND 7.  UNSTABLE HOT
AND THUNDERSTORMS WILL CONTINUE ACROSS THE SOUTHEAST THROUGH THE
PERIOD.  MONSOONAL MOISTURE STILL SEEMS TO PLAY A SIGNIFICANT ROLE
IN THE QPF OUT WEST THROUGH THE PERIOD EVEN THOUGH THE AMPLITUDE
OF THE WESTERN RIDGE DOES APPEAR TO DWINDLE TOWARDS THE LATTER
HALF OF THE FORECAST.  IN ADDITION...THE AXIS OF QPF THAT MAKES IT
FROM THE WEST TOWARD THE CENTRAL US WILL LIKELY DEPEND ON IF THE
FLOW REMAINS FLATTER AS PER THE GEFS/NAEFS SOLUTIONS OR THE MORE
AMPLIFIED SOLUTION OF THE ECMWF...WHICH HAS A BETTER DEFINED FRONT
MOVING ACROSS THE MIDWEST INTO THE NORTHEAST.

KOCIN





Last Updated: 1201 PM EDT TUE JUL 29 2014