Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4
000
FXUS02 KWBC 200659
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
258 AM EDT WED AUG 20 2014

VALID 12Z SAT AUG 23 2014 - 12Z WED AUG 27 2014

.OVERVIEW...
THE MEDIUM RANGE FORECAST PERIOD FOCUSES ON A
PROGRESSIVE...LOW-AMPLITUDE FLOW PATTERN ALOFT MIGRATING SEVERAL
UPPER-LEVEL SYSTEMS THROUGH SOUTHERN CANADA AND THE NORTHERN TIER.
ACROSS THE SOUTHEAST...SOUTHERN PLAINS AND NORTHERN GULF OF
MEXICO...A BROAD SUBTROPICAL RIDGE AXIS PREVAILS ALONG 25N-30N
LATITUDE---ANCHORING HOT AND HUMID CONDITIONS OVER A LARGE PORTION
OF THE REGION THROUGH THE MEDIUM RANGE PERIOD.

.MODEL PREFERENCES/UNCERTAINTY ASSESSMENT...
THE 19/12Z ECENS/NAEFS CAPTURE THE GENERAL LOWER-AMPLITUDE WAVE
STRUCTURE  AND PROGRESSIVE FLOW ACROSS SOUTHERN CANADA. AND FOR
THE MOST PART...NOW IDENTIFY WITH THE THERMAL PATTERN ANTICIPATED
BENEATH THE MID-LEVEL RIDGE--AND ISOLATED POCKETS OF TRIPLE-DIGIT
READING IN THE OZARKS...OKLAHOMA AND TEXAS.

USING THE DETERMINISTIC GUIDANCE AND PINPOINTING THE MOST ACTIVE
WEATHER THIS MEDIUM RANGE PERIOD...THE 19/12Z GFS/ECMWF WERE IN
DECENT AGREEMENT THROUGH DAY 4 WITH SIGNIFICANT HEIGHT FALLS
ACROSS THE NORTHERN ROCKIES AND NORTHERN PLAINS PUSHING OUT ACROSS
THE NORTH CENTRAL PLAINS--SOUTH DAKOTA AND NEBRASKA--ON SUNDAY
MORNING. AHEAD OF THE COLD FRONT...A BROAD AREA OF 250MB-500MB
LAYER DIVERGENCE FANS OUT ACROSS THE HIGH PLAINS OF WYOMING AND
COLORADO...WITH THE 19/12Z ECMWF A SLIGHTLY FASTER/STRONGER
SOLUTION VS THE 19/12Z GFS WITH RESPECT TO SOUTHWESTERLY JET
ENERGY AND 500MB PVA STREAKING OUT OF THE CENTRAL DIVIDE AND
MIGRATING ACROSS THE UPPER- AND MID-MISSOURI VALLEY ON SUNDAY
AFTERNOON/EVENING. BY MONDAY MORNING...THIS JET STREAK AND THE
CONVECTION ASSOCIATED WITH IT SPINS UP A RATHER ENERGETIC SURFACE
CYCLONE INVOF WEST CENTRAL MINNESOTA WITH LOW-LEVEL COLD ADVECTION
SURGING EAST-SOUTHWARD INTO THE CENTRAL PLAINS. ON MONDAY...THE
TEMPERATURE CONTRASTS AHEAD AND BEHIND THE FRONT WILL BE CLOSE TO
30F...WITH MUGGY CONDITIONS IN THE LOWER THIRD OF THE MISSOURI
VALLEY ADVECTING--IN A MODIFIED AIRMASS--NORTHEASTWARD AHEAD OF
THE FRONT AND INTO THE CENTRAL GREAT LAKES. THIS CLASH OF
CONTRASTING AIRMASSES--ALONG THE FRONT--IS ANTICIPATED TO BE AN
ACTIVE WEATHER SCENARIO ACROSS THE UPPER MIDWEST/MISSISSIPPI
VALLEY FOR DAY 5...AS THE UPPER-LEVEL FLOW BEHIND THE COLD FRONT
SHIFTS TO MORE OF A WESTERLY COMPONENT AND SHEARS THE COLD FRONT
EASTWARD ACROSS THE OHIO VALLEY.

.SENSIBLE WEATHER HIGHLIGHTS...
VERY WARM AND HUMID CONDITIONS EXPECTED FOR THE SOUTH BENEATH THE
WESTERN ATLANTIC RIDGE---EXPANDING WEST AND WEST-NORTHWEST INTO
THE SOUTH PLAINS AND MID-MISSISSIPPI VALLEY THIS WEEKEND.

A BACKDOOR COLD FRONT IS ASSOCIATED WITH A WEAK TROUGHING IN THE
WESTERN ATLANTIC WILL PRODUCE HIGH PRESSURE AND AN EASTERLY FLOW
ALONG THE EAST COAST...SURGING SOUTHWARD INTO THE
PIEDMONT...COASTAL GEORGIA AND THE `FIRST COAST` AND `SPACE COAST`
OF FLORIDA. THE FRONT DOES WEAKEN EARLY NEXT WEEK...BECOMES A
STATIONARY FRONT AND A FOCUS FOR SHOWERS AND THUNDERSTORMS ACROSS
THE PENINSULA FOR NEXT TUESDAY AND WEDNESDAY.

VOJTESAK

$$





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