Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6

000
FXUS02 KWBC 191614
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1213 PM EDT WED JUL 19 2017

VALID 12Z SAT JUL 22 2017 - 12Z WED JUL 26 2017

...PATTERN OVERVIEW AND WEATHER HIGHLIGHTS...

MODEL GUIDANCE THIS MORNING IS IN GOOD AGREEMENT THAT A SHORTWAVE
TROUGH WILL PASS THROUGH THE GREAT LAKES AND THE NORTHEAST OVER
THE WEEKEND INTO EARLY NEXT WEEK AS THE DEEP-LAYER HIGH OVER THE
MID-MISSISSIPPI VALLEY RETROGRADES INTO THE CENTRAL PLAINS BY THE
MIDDLE OF NEXT WEEK.  A PERIOD OF UNSETTLED WEATHER IS EXPECTED IN
THESE AREAS BEFORE COOLER AND DRIER AIR ARRIVES BY THE MIDDLE OF
THE WEEK.  MEANWHILE...HEAT AND HUMIDITY WITH SCATTERED
THUNDERSTORMS SHOULD CONTINUE FROM THE CAROLINAS DOWN TO THE DEEP
SOUTH WITH SCATTERED THUNDERSTORMS THROUGH THE PERIOD.  THIS IS
ESPECIALLY TRUE IN THE DEEP SOUTH WHERE MODELS CONTINUE TO DEPICT
A COMPACT UPPER-LEVEL CUT-OFF LOW RETROGRADES FROM THE SOUTHEAST
U.S. COAST BACK TOWARDS THE CENTRAL GULF COAST.  IN THE WEST...AN
UPPER TROUGH SHOULD ENTER THE PACIFIC NORTHWEST EARLY NEXT WEEK
WITH COOLER CONDITIONS BUT LITTLE ASSOCIATED RAINFALL.  FARTHER
SOUTH...SCATTERED AFTERNOON SHOWERS AND THUNDERSTORMS WILL BE A
DAILY OCCURRENCE IN THE SOUTHWEST AND INTERMOUNTAIN WEST AROUND
THE BACKSIDE OF THE UPPER HIGH AND AHEAD OF UPPER-LEVEL TROUGH.


...GUIDANCE EVALUATION/PREFERENCES...

THE ENSEMBLE MEAN SOLUTIONS FOR THE SURFACE PRESSURE FIELD AGREE
QUITE WELL INITIALLY...BUT THERE WERE NOTABLE DIFFERENCES BETWEEN
THE 00Z EC MEAN AND THE 00Z AND 06Z GEFS MEANS OVER THE NORTHEAST
AND FROM THE NORTHERN PLAINS NORTHWARD INTO CANADA BY DAY 7.  THE
ECMWF AND ITS ENSEMBLE MEAN CONTINUE TO DEPICT A QUICKER EASTWARD
PROGRESSION REGARDING THE SHORTWAVE TROUGH IN THE NORTHEAST AS
WELL AS THE SUBSEQUENT EVOLUTION OF THE UPPER-LEVEL ENERGY
EJECTING OUT INTO THE NORTHERN HIGH PLAINS EARLY NEXT WEEK.  THE
ECMWF HAS BEEN TRENDING TOWARD MORE TROUGHING OFF NEW ENGLAND ON
DAY 7 IN BETTER AGREEMENT WITH THE GFS.  THIS WOULD SUPPORT SOME
DEGREE OF CYCLOGENESIS IN THAT AREA WITH THE CENTER OF THE HIGH
FURTHER BACK TOWARDS THE GREAT LAKES THAN WHAT THE 00Z EC MEAN
SHOWS.  THE LATEST GFS PARALLEL ALSO SUPPORTS A LOW OFF NEW
ENGLAND BY DAY 7...WHICH IS IN AGREEMENT WITH THE 00Z ECMWF.  THE
06Z GFS PARALLEL APPEARS TO HANDLE THE SHEARED LOW PRESSURE SYSTEM
OVER THE GREAT LAKES FROM DAY 3 TO 5 BETTER THAN THE 06Z GFS.
OVER THE NORTHERN PLAINS...THE GFS AND ITS PARALLEL REMAIN MORE
ENTHUSIASTIC WITH A SLOWER AND DEEPER CYCLONE EJECTING INTO
SOUTH-CENTRAL CANADA ON DAYS 6 AND 7.  A BLEND OF THE ECMWF AND
THE GFS SHOULD YIELD AN INTERMEDIATE SOLUTION WITH A TRAILING COLD
FRONT DOWN INTO THE NORTHERN HIGH PLAINS.  THUS...THE WPC GRID
FIELDS WERE DERIVED USING A 50-50 BLEND OF THE 00Z ECMWF AND 06Z
GFS PARALLEL WITH MORE ENSEMBLE MEANS INCORPORATED TOWARD DAY 7.

$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.