Prognostic Meteorological Discussion
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FXUS02 KWBC 270659
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
258 AM EDT TUE JUN 27 2017

VALID 12Z FRI JUN 30 2017 - 12Z TUE JUL 4 2017

***PATTERN OVERVIEW***

THE MEDIUM RANGE PERIOD ON FRIDAY WILL BEGIN WITH A BROAD RIDGE
ALOFT OVER THE EASTERN U.S., A TROUGH OVER THE NORTH-CENTRAL
STATES, AND A RIDGE OVER THE WEST COAST.  AN ELONGATED FRONTAL
ZONE WITH MULTIPLE WAVES OF LOW PRESSURE ALONG IT IS EXPECTED
ACROSS THE CENTRAL PLAINS TO THE UPPER MIDWEST, AND EXTENDING
EASTWARD TO NEW ENGLAND.  THE UPPER TROUGH IS FORECAST TO SLOWLY
LIFT OUT INTO CANADA ALONG WITH ITS ACCOMPANYING SURFACE LOW BY
SUNDAY NIGHT, WITH QUASI-ZONAL FLOW ACROSS MOST OF THE NATION TO
BEGIN NEXT WEEK.  A FRONT MOVING ACROSS THE PACIFIC NORTHWEST
LATER IN THE FORECAST PERIOD SHOULD BE ACCOMPANIED BY AN UPPER
LEVEL TROUGH BUILDING OVER SOUTHWEST CANADA.


***MODEL PREFERENCES***

FOR THE MOST PART, MODELS AND ENSEMBLES ARE IN RELATIVELY GOOD
AGREEMENT AT THE BEGINNING OF THE FORECAST PERIOD WITH RESPECT TO
THE UPPER LEVEL PATTERN.  SIMILAR TO YESTERDAY, THE GFS REMAINS A
MORE AMPLIFIED SOLUTION ACROSS THE CENTRAL U.S. WITH RESPECT TO
THE TROUGH FROM SOUTHERN CANADA, AND IS ALSO HINTING AT A WEAK
UPPER LOW FORMING NEAR SOUTHERN CALIFORNIA.  REGARDLESS OF WHETHER
THIS FEATURE DEVELOPS, THE SENSIBLE WEATHER IMPACTS WOULD BE
NEGLIGIBLE.  THE CMC IS FASTER IN LIFTING THE TROUGH OUT OF THE
GREAT LAKES REGION SATURDAY NIGHT, WHEREAS THE ENSEMBLE MEANS ARE
CLOSER TO THE GFS AND ECMWF.  IN TERMS OF MODEL PREFERENCES, A
BLEND OF THE OPERATIONAL UKMET, GFS, AND ECMWF WAS INCORPORATED
FOR THE FIRST HALF OF THE FORECAST PERIOD.  INCREASING PERCENTAGES
OF THE GEFS AND EC MEANS WERE USED FOR NEXT WEEKEND WHEN
UNCERTAINTIES RELATED TO MESOSCALE DETAILS BECOME MORE SIGNIFICANT.


***SENSIBLE WEATHER***

WITH THE EAST COAST RIDGE AND MIDWEST TROUGH, A COLD FRONT WILL
BECOME NEARLY STATIONARY FROM THE GREAT LAKES DOWN ACROSS THE
MIDWEST AND THE CENTRAL PLAINS AS THE BERMUDA HIGH BUILDS AND
KEEPS THE FRONT FROM MAKING SIGNIFICANT EASTWARD PROGRESS.  THIS
WILL CONCENTRATE SHOWERS AND THUNDERSTORMS ALONG AND AHEAD OF THE
FRONT, WITH THE POSSIBILITY OF HEAVY RAIN FROM OKLAHOMA TO THE
GREAT LAKES REGION THROUGH EARLY SUNDAY.  BY MONDAY AND INTO EARLY
TUESDAY, SHOWERS AND THUNDERSTORMS SHOULD BECOME MORE SCATTERED IN
NATURE ACROSS THE EASTERN HALF OF THE COUNTRY.  THE GREATEST
COVERAGE IS LIKELY ACROSS THE UPPER MIDWEST AND EXTENDING EASTWARD
TO SOUTHERN MICHIGAN BASED ON THE LATEST MODEL GUIDANCE.  IN TERMS
OF TEMPERATURES, EXPECT HOT AND DRY CONDITIONS TO CONTINUE FOR THE
LOWER ELEVATIONS OF THE SOUTHWEST, BUT NOTHING RECORD BREAKING IS
CURRENTLY ANTICIPATED.  AFTER A FEW DAYS OF COOLER WEATHER, EXPECT
HOT AND HUMID CONDITIONS FOR MOST OF THE EAST COAST REGION IN TIME
FOR THE WEEKEND.

HAMRICK

$$




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