Prognostic Meteorological Discussion
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FXUS02 KWBC 011523
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1122 AM EDT SAT AUG 01 2015

VALID 12Z TUE AUG 04 2015 - 12Z SAT AUG 08 2015

THE TROUGH/RIDGE/TROUGH PATTERN CONTINUES TO EVOLVE AS RECENTLY
ADVERTISED FOR THE MEDIUM RANGE PERIOD...ALTHOUGH SOME OF THE
DETAILS WERE MORE DIFFICULT TO ASSESS IN THE LATER TIME PERIODS
SINCE THERE WAS LESS MODEL AGREEMENT THAN OBSERVED YESTERDAY.  IT
STILL APPEARS THOUGH THAT THE MIDWEST AND NORTHEAST ARE IN STORE
FOR A SIGNIFICANT COOLDOWN AS EARLY AS DAY 3/TUESDAY AS COOLER AIR
WILL RESULT IN PLEASANT TEMPERATURES AND LOW HUMIDITIES FROM THE
MIDWEST THROUGH THE NORTHEAST.  A REINFORCING AREA OF RELATIVELY
COOL AIR WILL KEEP THE MIDWEST AND NORTHEAST AGAIN ON DAY
4/WEDNESDAY IN VERY PLEASANT TEMPERATURES FOR EARLY AUGUST.

IN GENERAL...THERE WERE NO SIGNIFICANT DIFFERENCES BETWEEN THE
OVERNIGHT ENSEMBLES AND THE OPERATIONAL RUNS THROUGH DAY 3 AND 4.
HOWEVER... THE 00Z ECMWF APPEARS TO BE ON THE MORE AMPLIFIED OF
THE SUITE OF SOLUTIONS IN BRINGING THE COOLER AIR SOUTHWARD ACROSS
THE MIDDLE ATLANTIC STATES ON DAYS 4 INTO 5/WEDNESDAY AND
THURSDAY...AND WAS NOT INCLUDED IN THE BLEND PAST DAY 4.  BOTH THE
OPERATIONAL RUNS OF THE GFS AND ECMWF HAVE BEEN NOT PARTICULARLY
CONSISTENT FROM RUN TO RUN SO IT IS DIFFICULT TO PUT MUCH FAITH IN
EITHER OF THE 2 MODELS.  HOWEVER...THE 00Z GFS APPEARED MORE
CONSISTENT WITH THE ENSEMBLE MEANS AND WAS USED IN A SMALLER
CAPACITY COMPARED TO THE MEANS ON DAYS 5 THROUGH 7/THURSDAY
THROUGH SATURDAY.  IN GENERAL...A COMBINATION OF THE 00Z EUROPEAN
AND GEFS MEAN WITH A SMALL CONTRIBUTION FROM THE GFS WAS USED FOR
THE DAY 6 FORECAST...WHILE THE DAY 7 FORECAST WAS MADE COMPLETELY
FROM THE EUROPEAN ENSEMBLE MEANS...WHICH SEEM TO HAVE THE MOST
CONSISTENCY OVER THE PAST FEW RUNS.

GIVEN THE DIFFERENCES IN THE OPERATIONAL RUNS...ANY SHORTWAVE
SYSTEMS MOVING THROUGH THE WESTERN RIDGE AND ACROSS THE
MISSISSIPPI AND OHIO VALLEYS TOWARD THE MIDDLE ATLANTIC STATES
APPEAR ALL OVER THE PLACE IN THE OPERATIONAL RUNS.
HOWEVER...BASED ON SOME CONTINUITY AND SOME CONSISTENT SIGNALS IN
THE ENSEMBLE MEANS...IN PARTICULAR THE EUROPEAN ENSEMBLE
MEANS...INDICATE THAT THE GREATEST POTENTIAL FOR PRECIPITATION
LIES ALONG THE SUBSIDING FRONT THAT SUBSEQUENTLY BECOMES
STATIONARY FROM THE PLAINS TO THE MISSISSIPPI VALLEY TO POSSIBLY
SOME LOW PRESSURE SYSTEMS THAT EMERGE EVEN FROM THE MEANS ALONG
THE OHIO VALLEY AND MID ATLANTIC STATES ON DAY 5/THURSDAY.  THE
POTENTIAL FOR HEAVY RAINFALL IS THERE FROM THE MID MISSISSIPPI
VALLEY ACROSS THE OHIO VALLEY AND MID ATLANTIC STATES THROUGH DAY
5. ON DAYS 6 AND 7/FRIDAY AND SATURDAY...THE MEANS SHOW THAT LOW
PRESSURE WILL CONSOLIDATE NEAR THE MID ATLANTIC COAST AND MOVE
OFFSHORE.  THIS IS THE PERIOD WHEN COOLER AIR BEHIND THE FRONT
APPEARS TO CONTINUE SOUTHWARD ACROSS THE SOUTH ATLANTIC AND EVEN
NORTHERN SOUTHEAST STATES.

AS THE TROUGH OVER THE NORTHWEST HEADS INLAND...THERE ARE
SIGNIFICANT NUMBER OF DISSIMILAR SOLUTIONS BUT THE NET EFFECT WILL
BE COOLING IN THE NORTHWEST WHILE THE HEAT CONTINUES ACROSS THE
SOUTHWEST/INTERMOUNTAIN WEST AND ACROSS THE SOUTHERN PLAINS.
WHILE DETAILS ARE NOT EASY TO COME BY...THE AREA ALONG THE
STATIONARY FRONT ACROSS THE CENTRAL PLAINS TOWARD MID MISSISSIPPI
VALLEY COULD BE A FOCUS FOR SIGNIFICANT CONVECTION THROUGH THE
PERIOD.

KOCIN

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