Prognostic Meteorological Discussion
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FXUS02 KWBC 241632
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1231 PM EDT FRI OCT 24 2014

VALID 12Z MON OCT 27 2014 - 12Z FRI OCT 31 2014

...THE POTENT EXTRATROPICAL LOW ASSOCIATED WITH TROPICAL STORM ANA
THREATENS BC AND THE NWRN US...

WPC MEDIUM RANGE GUIDANCE HAS BEEN PRIMARILY DERIVED FROM A BLEND
OF REASONABLY COMPATABLE GUIDANCE FROM THE 06 UTC GFS/GEFS MEAN
AND 00 UTC ECMWF/ECMWF ENSEMBLE MEAN MON INTO THU...BEFORE
TRANSITIONING TO MODESTLY HIGHER WEIGHTING OF THE 00 UTC ECMWF
ALONG WITH GFS/ECMWF ENSEMBLES LATER THU INTO NEXT FRI AT THE
EXPENSE OF THE DETERMINISTIC 06 UTC GFS.

THE LATEST MODELS AND ENSEMBLES ARE IN BETTER AGREEMENT WITH THE
APPROACH AND INLAND PUNCH INTO NORTH AMERICA OF THE POTENT
EXTRATROPICAL LOW ASSOCIATED WITH CURRENT PACIFIC TROPICAL STORM
ANA NOW LOCATED WELL NW OF THE HAWAIIAN ISLANDS. ANA HAS BEEN
AROUND FOR A WHILE AND IS FORECAST BY THE CENTRAL PACIFIC
HURRICANE CENTER TO APPROACH VANCOUVER ISLAND WITH 45 KT SUSTAINED
WINDS AND 55 KNOT GUSTS TUE. HIGHER TERRAIN ENHANCED GUSTS ARE
LIKELY INLAND BY TUESDAY WITH APPROACH. AN ASSOCIATED AND WELL
ORGANIZED HEAVY WIND/WAVE AND PCPN THREAT EXISTS INTO BC AND WITH
FRONTAL SURGE DOWN AND ACROSS THE NWRN US. THIS INCLUDES INLAND
ELEVATION HEAVY SNOW POTENTIAL OVER THE NRN ROCKIES INTO MIDWEEK
CONSIDERING AVAILABLE MOISTURE AS CURRENTLY FED INTO THE TROPICAL
SYSTEM AS PER BLENDED TPW LOOPS.

THIS LOW IS FORECAST TO TRACK INTO THE NRN PLAINS AND UPPER
MIDWEST THU AND THROUGH THE GREAT LAKES INTO THE NORTHEAST IN
ABOUT A WEEK. THIS OFFERS A THREAT FOR ENHANCED COLD ADVECTION
LAKE EFFECT PCPN IN THE WAKE OF THIS FEATURE. GUIDANCE BEGINS TO
DIFFER MORE IN ERNEST WITH THE SYSTEM AND THE TRANSLATION SPEED OF
A TRAILING COLD FRONT AND PROGRESSIVE MODEST PCPN IN THIS DAY 6/7
TIME FRAME AND THE WPC SOLUTION IS ON THE STRONGER/MORE AMPLIFIED
SIDE OF THE FULL ENVELOPE OF MODEL AND ENSEMBLE SOLUTIONS GIVEN
UPSTREAM FLOW AMPLITUDE TRENDS...BUT NOT AS STRONG AND COLD AS THE
00 UTC ECMWF THAT STILL DOES NOT HAVE SUFFICIENT ENSEMBLE SUPPORT.

OVERALL...THE 06 UTC GFS HAS TRENDED TOWARD THIS WPC SOLUTION
SIGNIFICANTLY COMPARED TO THE 00 UTC GFS RUN. THIS IS ESPECIALLY
EVIDENT WITH THE LESS PROGRESSIVE NATURE OF AMPLE ERN PACIFIC
MID-UPPER LEVEL TROUGHING INLAND INTO THE WRN US LATER NEXT WEEK
WITH DELAYED HEIGHT FALLS ONSHORE IN THE 06 UTC GFS MORE IN LINE
WITH THE ECMWF/ECMWF ENSEMBLES. THIS SEEMS A BETTER FIT
CONSIDERING THE AMBIENT DOWNSTREAM AMPLIFIED RIDGE POSITION BY
THEN BUILT OVER THE INTERIOR WEST.

SCHICHTEL



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