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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0706Z Oct 29, 2014)
 
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Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


EXTENDED FORECAST DISCUSSION...CORRECTED TYPO PARAGRAPH 5
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
306 AM EDT WED OCT 29 2014

VALID 12Z SAT NOV 01 2014 - 12Z WED NOV 05 2014

...ACTIVE WEATHER PATTERN FOR THE LOWER 48...

...OVERVIEW...
TWO DEEP AND ORGANIZED UPPER-LEVEL TROUGHS WILL MIGRATE ACROSS THE
LOWER 48...WITH EACH DELIVERING WINDY...WET AND UNSETTLED
CONDITIONS IN THEIR PATH.

...UNCERTAINTY ASSESSMENT...
THE 28/12Z ECENS/GEFS AND NAEFS MEANS WERE IN DECENT AGREEMENT
THROUGH DAY 4 WITH THE AMPLITUDE AND WEST TO EAST PROGRESSION OF
THE UPPER-LEVEL TROUGHS ALONG THE EAST AND WEST COASTS. HEADING
INTO DAY 5...THE GEFS/NAEFS IS A SLIGHTLY FASTER SOLUTION EJECTING
ENERGY OUT OF THE CENTRAL ROCKIES AND DOWNSTREAM INTO THE LOWER
HALF OF THE MISSOURI VALLEY. MUCH OF THE DIFFERENCE CONTINUES TO
RESULT FROM THE JET-LEVEL WIND PROGS AND THE STRUCTURE OF THE FLOW
MOVING OUT OF THE SOUTHERN ROCKIES.

THESE DIFFERENCES IMPACT THE ORIENTATION OF THE SURFACE FRONT FROM
THE TX/OK BORDER TO THE WESTERN OHIO VALLEY FOR DAYS 6-7 AND THE
ABILITY OF THE FRONT TO ERODE THE WESTERN FLANKS OF THE SURFACE
RIDGE IN THE SOUTHEAST AND EAST CENTRAL STATES.   

...MODEL PREFERENCES...
THE MEANS CONTINUE TO CAPTURE THE PRIMARY SENSIBLE WEATHER
FEATURES DURING THIS PARTICULAR DAY 3-7 PATTERN---AND COMPRISED A
GREAT DEAL OF THE MASS FIELD FORECASTS.

IN THE EAST...THE 'CAROLINAS' CLOSED LOW SOLUTION HAS 'RE-EMERGED'
AS A POSSIBILITY---AFTER A BRIEF ABSENCE---AND SUPPORTS A
SECONDARY MOISTURE-GENERATION SOURCE WITHIN AND ABOVE...THE
COLDER/DRY CANADIAN SURFACE HIGH IN PLACE ACROSS THE EAST CENTRAL
US ON DAY 3. THE DIFFERENCES---WHICH HAVE BEEN A STAPLE OF THE
MEDIUM RANGE FORECAST FOR 4-5 DAYS NOW...FOCUSES ON THE LEADING
EDGE OF THE COLD FRONT...PARALLEL TO AND DRIFTING EAST OF 70W
LONGITUDE ON SATURDAY. THE SECONDARY SURFACE CYCLOGENESIS REGION
CONTINUES TO BE ALONG THE COLD FRONT IN THE WESTERN ATLANTIC...AND
KEEPS NEW ENGLAND...THE GULF OF MAINE AND ATLANTIC CANADA IN THE
BEST UPGLIDE AND WRAP-AROUND PRECIPITATION. AND THE PRESENCE OF A
CLOSED LOW...SIMPLY PROVIDES A SECONDARY SOURCE OF INSTABILITY AND
VORTICITY FOR SHOWERS TO OCCUR IN WHAT WOULD NORMALLY BE A VERY
DRY BUT COLD AIRMASS. OVER THE SOUTHERN APPALACHIANS INTO DAY 4
AND THE NORTHERN APPALACHIANS OF NEW ENGLAND INTO DAY 5...THIS
MEANS SNOW SHOWERS! DID USE THE 28/12Z DETERMINISTIC GFS/ECMWF TO
CAPTURE SOME OF THE SURFACE GRAPHIC DETAIL OFF THE EAST COAST.
AFTER A QUICK LOOK AT THE 29/00Z RUNS...A GENERAL CONSENSUS WILL
WORK AS THE CLOSED LOW QUICKLY WRAPS UP AND ARCS COUNTER-CLOCKWISE
TOWARDS DOWNEAST MAINE AND NEW BRUNSWICK.

IN THE WEST AND ACROSS THE PLAINS STATES...THE DETERMINISTIC
GFS/ECMWF BEGIN TO DIVERGE ON DAY 4 IN THE NORTHERN ROCKIES...THE
SOUTHERN PLAINS ON DAY 5 AND OVER THE MID-MISSISSIPPI VALLEY ON
DAY 6. MUCH IF NOT ALL THE SPREAD APPEARS TO BE DIRECTLY RELATED
TO THE JET-LEVEL WINDS...ROUNDING THE BASE OF THE TROUGH IN THE
SIERRA ON DAY 3-4...AND AS THE UPPER-LEVEL TROUGH MIGRATES INTO
THE CENTRAL AND SOUTHERN CONTINENTAL DIVIDE...FOR DAYS 4-5. PREFER
TO HOLD CLOSER TO A 50/50 BLEND OF THE GEFS/ECENS MEANS FOR DAY
4-6. SUSPECT THE SOUTHERN END OF THE TROUGH WILL BE SLOWER THROUGH
TIME...BUT HOW MUCH SLOWER IS DIFFICULT TO DISCERN.  

...SENSIBLE WEATHER HIGHLIGHTS...
APPRECIABLE EARLY-NOVEMBER SNOWFALL ACCUMULATIONS IN THE
APPALACHIANS AND LEE OF THE EASTERN GREAT LAKES IS LOOKING MORE
AND MORE LIKELY---GIVEN THE INITIAL AND SECONDARY SURGES OF
CANADIAN AIR MOVING THROUGH THE NORTHEAST QUARTER OF THE NATION
BETWEEN DAY 3 AND DAY 5. TEMPERATURES FOR DAYS 3-4 WILL BE A GOOD
10F-15F BELOW NORMAL. 

WINDY CONDITIONS IN THE PLAINS FOR DAYS 4 AND 5...WILL BE
ACCOMPANIED BY A THREAT FOR DEEP CONVECTION IN THE SOUTHERN PLAINS
AS A STRONG JET STREAK EJECTS FROM THE SOUTHERN ROCKIES ON SUNDAY
AND GLIDES NORTHEASTWARD ALONG THE COLD FRONT---INTO THE CENTRAL
MIDWEST ON MONDAY AND TUESDAY.

VOJTESAK