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Extended Forecast Discussion
 
(Latest Discussion - Issued 1558Z Nov 21, 2017)
 
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Abbreviations and acronyms used in this product
 
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1058 AM EST TUE NOV 21 2017

VALID 12Z FRI NOV 24 2017 - 12Z TUE NOV 28 2017

...OVERVIEW/GUIDANCE PREFERENCES...

THE PRIMARY FEATURES OVER THE NEXT WEEK WILL BE A TROUGH OVER THE
EAST COAST WITH A STRONG RIDGE OVER THE WEST COAST. THIS RIDGE
WILL EVENTUALLY BREAK DOWN BY THE BEGINNING OF NEXT WEEK AS A
TROUGH MOVES OVER THE WEST COAST. FOR MOST OF THE MEDIUM RANGE
PERIOD...AN ACTIVE PATTERN WILL BE IN PLACE FOR THE PACIFIC
NORTHWEST... INTERMOUNTAIN WEST...IN ADDITION TO NORTHERN
CALIFORNIA. FARTHER SOUTH...FLORIDA WILL FINALLY BE WANING OFF A
WET PATTERN IN TIME FOR THE WEEKEND.

THE MODELS AND ENSEMBLES CONTINUE TO BE IN GOOD AGREEMENT WITH THE
SYNOPTIC PATTERN OVER THE NEXT WEEK...BUT THERE WERE DIFFERENCES
WITH TIMING AND AMPLITUDE WITH THE SMALL SCALE SYSTEMS. THE
BIGGEST CONFLICT WAS THE TIMING OF THE TROUGH COMING INTO THE WEST
COAST BETWEEN SUNDAY AND MONDAY AND HOW IT EVOLVES MOVING INTO THE
PLAINS BY TUESDAY.  THE OPERATIONAL ECMWF AND EVEN THE GFS HAS
ALTERNATED BETWEEN A DISTURBANCE MOVING ACROSS THE PLAINS TO A
RIDGE BEING IN PLACE.  HOWEVER...THEIR ENSEMBLES HAVE BEEN
CONSISTENT WITH THE SLOWER SOLUTION.  FOR THE BEGINNING OF THE
MEDIUM RANGE PERIOD...HAD AN EVEN SPLIT BETWEEN THE 06Z GFS/00Z
ECMWF AND A SLIGHT WEIGHT TO THEIR ENSEMBLES.  BY DAYS 5-7
(SUN-TUE)...MUCH LESS WEIGHT WAS GIVEN TO THE OPERATIONAL
GFS/ECMWF AND PUT MORE WEIGHT TOWARD THE 00Z ECENS/NAEFS WITH SOME
GEFS AS THE NAEFS WAS ALSO CONSISTENT WITH THE EVOLUTION OF THE
FRONTAL SYSTEM MOVING INTO THE PLAINS BY MIDWEEK. 

...WEATHER HIGHLIGHTS...

AS A COLD FRONT PUSHES SOUTHWARD ACROSS FLORIDA ON FRIDAY AND INTO
SATURDAY...HEAVY RAINFALL WILL PERSIST ON FRIDAY AND COMPLETELY
CLEARING OUT BY SATURDAY.  DEPENDING ON HOW CLOSE THE SURFACE LOW
MOVES ALONG THE EAST COAST...THE CAROLINAS COULD SEE SOME LIGHT TO
MODERATE RAINFALL.  A CLIPPER SYSTEM WILL ALSO DELIVER A MIX OF
RAIN AND SNOW TO THE UPPER MIDWEST/GREAT LAKES ON
FRIDAY/SATURDAY...WITH SNOW LINGERING ACROSS THE LOWER GREAT LAKES
AND INTERIOR NEW ENGLAND BY THE END OF THE WEEKEND. THE FOCUS OF
ACTIVE WEATHER SHIFTS TO THE WEST COAST BY THE BEGINNING OF NEXT
WEEK AS THE TROUGH APPROACHES THE WEST COAST.  HEAVY RAINFALL
ALONG WITH HIGHER ELEVATION SNOW WILL INCREASE ACROSS THE PACIFIC
NORTHWEST AND INTERMOUNTAIN WEST ON SUNDAY...AND WILL CONTINUE
INTO MONDAY WHILE SPREADING FARTHER SOUTH ACROSS CALIFORNIA.  BY
TUESDAY...MOST OF THE WEST COAST WILL DRY OUT WITH THE EXCEPTION
OF THE NORTHERN PORTIONS OF THE PACIFIC NORTHWEST WITH YET ANOTHER
ROUND OF RAINFALL ALONG WITH HIGHER ELEVATION SNOW. THE BULK OF
PRECIPITATION WILL BE IN THE NORTHERN PLAINS/UPPER MIDWEST...WITH
A MIX OF RAIN/SNOW/WINTRY PRECIPITATION WILL BE POSSIBLE.

IN TERMS OF TEMPERATURES...ABOVE AVERAGE TEMPERATURES WILL BE
PRESENT ACROSS THE CENTRAL AND WESTERN PORTIONS OF THE U.S.
THROUGH MOST OF THE WEEKEND. IN CONTRAST...BELOW AVERAGE
TEMPERATURES WILL BE PRESENT ACROSS THE EASTERN AND SOUTHEASTERN
U.S. THROUGHOUT THE WEEKEND.  BELOW AVERAGE TEMPERATURES WILL
CREEP IN ACROSS THE WEST COAST BY MONDAY AND BE PRESENT INTO
TUESDAY. 


REINHART