Preliminary Forecasts
Issued by NWS

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FXUS02 KWNH 200638
PREEPD

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
238 AM EDT SUN APR 20 2014

VALID 12Z WED APR 23 2014 - 12Z SUN APR 27 2014

...GUIDANCE PREFERENCES/UNCERTAINTY ASSESSMENTS...

THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A
BLEND OF REASONABLY WELL CLUSTERED GUIDANCE FROM THE 18 UTC
GFS/GFS ENSEMBLE MEAN AND 12 UTC ECMWF AND ECMWF/NAEFS ENSEMBLE
MEANS DAYS 3-5/WED-FRI IN A PERIOD WITH OVERALL BELOW NORMAL
FORECAST SPREAD AND UNCERTAINTY. THIS WPC BLENDED SOLUTION IS NEAR
THE CENTER OF THE FULL ENVELOPE OF GUIDANCE SOLUTIONS AND FURTHER
INCORPORATES SOME WPC/NDFD CONTINUITY ALONG WITH SITUATIONAL
MANUAL ADJUSTMENTS BASED ON PATTERN RECOGNITION AND MODEL BIAS.  I
SEE MINIMAL COMPELLING REASON TO VEER MUCH FROM CONCENSUS DURING
THIS PERIOD.

PREFER A 12 UTC GFS/NAEFS/ECMWF ENSEMBLE MEAN MIXED WITH WPC/NDFD
CONTINUITY BASED FORECAST APPROACH BY DAYS 6/7/NEXT WEEKEND IN A
PERIOD WITH GROWING FORECAST SPREAD AND UNCERTIANTY.  THE
MID-UPPER LEVEL FLOW SOLUTION ASSOCIATED WITH THIS BLENDED
SOLUTION IS LESS PROGRESSIVE/MORE AMPLIFIED THAN THE 12 UTC
ECMWF...BUT NOT TO THE EXTENT OF RECENT GFS RUNS WHOSE MORE CLOSED
SPRING SYSTEM NATURES ARE POSSIBLE.  IT IS INTERESTING THOUGH AS
THE GFS USUALLY IS ON THE MORE PROGRESSIVE SIDE OF SOLUTIONS.

...PATTERN OVERVIEW AND SENSIBLE WEATHER HIGHLIGHTS...

POTENT MID-UPPER LEVEL TROUGH AND SURFACE SYSTEM ENERGIES WORK
THROUGH THEN OFF THE ERN/NERN US/CANADIAN MARITIMES WED/THU...WITH
MODEST PCPN IN ADVANCE AND DECENT POST-FRONTAL COOLING HIGH
PRESSURE.

MEANWHILE...ANOTHER AMPLIFIED MID-UPPER LEVEL TROUGH/POTENT HEIGHT
FALLS WORKS THROUGH THE INTERMOUNTAIN WEST AND WINTERY NRN ROCKY
STATES MIDWEEK BEFORE STEADILY CROSSING THE CENTRAL THEN
EAST-CENTRAL US THU-SUN. THIS SHOULD SET THE STAGE FOR A WELL
ORGANIZED LOW/FRONT TO DEVELOP AND INCREASINGLY FOCUS
MOISTURE/PCPN ALONG WITH POST-FRONTAL COOLING ACROSS THE REGION.
HEAVIEST PCPN POTENTIAL SHOULD BE CLOSER TO THE MAIN LOW TRACK
ACROSS NWRN US/NRN ROCKIES TERRAIN AND OUT ACROSS THE N-CENTRAL
US...BUT DYNAMIC SUPPORT AND INSTABILITY SHOULD ALSO OFFER A
CONVECTIVE SPARK FARTHER SOUTHWARD ACROSS THE WELL WARMED
S-CENTRAL AND E-CENTRAL US AS MOISTURE RETURNS FROM THE GULF OF
MEXICO.

UPSTREAM...YET ANOTHER DYNAMIC MID-UPPER LEVEL TROUGH AND SURFACE
SYSTEM WITH ENHANCED PCPN REACHES THE US WEST COAST FRI IN WPC
PROGS.  THIS SYSTEM IS KICKED INLAND ACROSS AN UNSETTLED/COOLING
WRN US BY ADDITIONAL ERN PACIFIC ENERGIES AND IS EXPECTED TO REACH
THE PLAINS NEXT SUN IN A DEVELOPING RETURN FLOW CONVECTIVE PATTERN.

SCHICHTEL

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