Preliminary Forecasts
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FXUS02 KWNH 220646
PREEPD

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
145 AM EST WED FEB 22 2017

VALID 12Z SAT FEB 25 2017 - 12Z WED MAR 01 2017

...OVERVIEW...

DURING THE FIRST HALF OF THE PERIOD THE STRONG SYSTEM AFFECTING
THE EAST WILL TRACK OUT OF THE GRTLKS WHILE THERE ARE STILL
LINGERING UNCERTAINTIES WITH ERN PAC LOW PRES THAT SHOULD TRACK
INTO THE WEST SUN-MON.  IN SOME RESPECTS GUIDANCE SHOWS A LITTLE
BETTER AGREEMENT BY THE LATTER HALF OF THE PERIOD AS LARGER SCALE
TROUGHING EVOLVES NEAR THE WEST COAST AND THEN EJECTS INLAND WHILE
THE SERN RIDGE STRENGTHENS... ANCHORED BY AN UPR HIGH OVER/NEAR
CUBA.


...MODEL EVALUATION/PREFERENCES...

TAKEN AS A WHOLE THERE IS A FAIR DEGREE OF CONTINUITY WITH THIS
WEEKEND`S ERN PAC/WEST COAST EVOLUTION FOR WHICH GUIDANCE HAS HAD
DIFFICULTY IN RECENT DAYS.  THE 12Z ECMWF WAS THE ONE EXCEPTION...
REVERTING BACK TO A FASTER EJECTION OF WEST COAST ENERGY SEEN IN
MOST GUIDANCE 2-3 DAYS AGO.  HOWEVER THE FULL SPECTRUM OF 12Z
ENSEMBLE GUIDANCE WAS ALMOST AS DIVERGENT AS IT WAS 24 HRS AGO
WITH A SPLIT BTWN PROGRESSIVE EJECTION AND WHAT HAS BECOME THE
MAJORITY CLUSTER REPRESENTED IN VARYING WAYS BY GFS/UKMET/CMC RUNS
AND THE ENSEMBLE MEANS.  THIS LARGER CLUSTER HAS THE ENERGY
INTERACTING WITH A SYSTEM FARTHER OFFSHORE AND BRINGING THE
OVERALL FEATURE INLAND BY LATE SUN-SUN NIGHT.  IT IS WORTH NOTING
THAT THERE WERE ENOUGH 12Z ECMWF ENSEMBLES THAT LEANED TOWARD THE
GFS CLUSTER THAT THE MEAN SHOWS SOME HINT OF THAT IDEA.  THE
CONTINUING SPREAD IN ENSEMBLES... AS WELL AS THIS BEING A TYPE OF
EVOLUTION THAT TENDS TO HAVE LOWER PREDICTABILITY... TEMPER
CONFIDENCE IN A SPECIFIC SOLN.  PREFER MAINTAINING CONTINUITY IN
PRINCIPLE WITH A FCST BTWN NON-12Z ECMWF SOLNS AND THE ENSEMBLE
MEANS.

BY SUN-MON THERE IS DECENT AGREEMENT ON HOW UPSTREAM ENERGY SHOULD
SERVE TO DEEPEN THE WEST COAST TROUGH.  THEN ENERGY REACHING THE
EXTREME NERN PAC SHOULD BEGIN HELPING TO PUSH THE TROUGH INLAND
WITH ASSOC LOW PRES TRACKING FROM THE PLAINS INTO THE GRTLKS
TUE-WED.  AT THIS LATTER TIME FRAME RECENT GFS RUNS WERE HOLDING
BACK THE DEVELOPING NERN PAC TROUGH RELATIVE TO MOST OTHER
GUIDANCE... LIKELY PLAYING A PART IN THE GFS STRAYING FASTER THAN
MOST OTHER SOLNS WITH SFC LOW PRESSURE THAT EMERGES OVER THE
PLAINS BY AROUND TUE.  TOWARD DAYS 6-7 TUE-WED THE 12Z ECMWF/CMC
AND 18Z GEFS/12Z ECMWF MEANS WERE SIMILAR IN PRINCIPLE WITH A TILT
MORE TOWARD THE MEANS PREFERRED GIVEN TYPICAL ERROR FOR FCSTS THAT
FAR IN ADVANCE.  THIS CLUSTER MAINTAINS REASONABLE CONTINUITY
ASIDE FROM SHOWING A MODESTLY SLOWER ADJUSTMENT WHICH HAS BEEN THE
TREND OVER RECENT DAYS.

CLUSTERING HAS IMPROVED FOR THE SYSTEM FCST TO BE OVER THE GRTLKS
AS OF 12Z SAT.  THERE IS ALSO A REASONABLE CONSENSUS TOWARD THE
IDEA OF THE SYSTEM LIFTING A LOWER LATITUDE WRN ATLC FEATURE TO
ERN MAINE/NOVA SCOTIA BY EARLY SUN.

THE UPDATED BLEND REFLECTS PREFS FOR THE ERN PAC/WRN U.S. DAYS 3-5
SAT-MON... INCLUDING THE 12Z-18Z GFS/12Z CMC AND 18Z GEFS/12Z
ECMWF MEANS.  THEN ASIDE FROM THE 12Z GFS STILL BEING ACCEPTABLE
AS A COMPONENT 12Z TUE... DAYS 6-7 REPLACE THE GFS WITH THE 12Z
ECMWF WHILE THE OTHER COMPONENTS ARE MAINTAINED.


...WEATHER HIGHLIGHTS/THREATS...

SYSTEM LIKELY TO TRACK INTO THE WEST FROM THE ERN PAC IN THE
LATTER HALF OF THE WEEKEND ALONG WITH THE LARGER SCALE TROUGH
ALOFT MOVING THROUGH THE WEST DURING THE FIRST HALF OF NEXT WEEK
WILL SPREAD A BROAD AREA OF RAIN AND HIGHER ELEV/INLAND SNOW
ACROSS THE SRN HALF TO 2/3 OF THE WEST.  EXPECT HIGHEST TOTALS
OVER FAVORED TERRAIN IN CALIFORNIA.  POTENTIAL STILL EXISTS FOR
THE ERN PAC SYSTEM TO BRING A PERIOD OF STRONG WINDS.  EWD
PROGRESSION OF THE UPR TROUGH WILL SUPPORT A DRYING TREND OVER
THESE AREAS BY MIDWEEK WITH PRIMARY FOCUS OF LGT/MDT PRECIP LIKELY
TO SHIFT TO THE PAC NW/NRN ROCKIES AT THAT TIME.  WHILE THE WEST
TRENDS DRIER THE ERN HALF OF THE LOWER 48 WILL SEE INCREASING
COVERAGE/INTENSITY OF PRECIP MON-WED AS LOW PRES TRACKS THROUGH
THE PLAINS INTO THE GRTLKS AND MSTR INTERACTS WITH A LEADING WARM
FRONT/TRAILING COLD FRONT.  THE BEST POTENTIAL FOR HVY RNFL EXISTS
OVER THE OH VLY/TN VLY/APLCHNS REGION.  MOST MEANINGFUL WINTRY
WEATHER SHOULD BE CONFINED TO FAIRLY NRN LATITUDES.  LEADING STORM
SYSTEM AFFECTING THE EAST EARLY IN THE PERIOD WILL LIKELY BRING
HEAVIEST RAIN TO THE NORTHEAST.

EXPECT MUCH OF THE WEST TO SEE PERSISTENTLY BELOW NORMAL TEMPS
WITH SOME AREAS SEEING MINUS 10-15F ANOMALIES FOR HIGHS ON
MULTIPLE DAYS.  MINS SHOULD BE LESS EXTREME CNTRL-SRN AREAS DUE TO
CLOUDS/PRECIP.  BELOW NORMAL READINGS MAY EXTEND INTO THE PLAINS
SAT BEFORE A WARMING TREND THAT COULD BE SLOWED DOWN BY SNOW COVER
OVER SOME N-CNTRL LOCATIONS.  EAST COAST STATES SHOULD SEE ONE
MORE WARM DAY SAT BEFORE NEAR/SLIGHTLY BELOW NORMAL TEMPS MOVE IN
FROM THE PLAINS/MS VLY.  SYSTEM LIKELY TO EMERGE FROM THE PLAINS
AND TRACK INTO THE GRTLKS NEXT WEEK WILL LIKELY BRING ANOTHER
SURGE OF WARMTH TO CNTRL-ERN AREAS.  MIN TEMPS MAY REACH 20-30F
ABOVE NORMAL FOR SOME DAILY RECORDS WHILE ANOMALIES FOR DAYTIME
HIGHS LOOK SOMEWHAT LESS EXTREME.

RAUSCH

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