Good Chance - Stormy Holiday Weekend
Posted by
JAC on 12/19/2010, 2:33 pm
PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
900 AM EST SUN DEC 19 2010
VALID 12Z THU DEC 23 2010 - 12Z SUN DEC 26 2010
THE FORECAST SPREAD/SOLUTION ENVELOPE REMAINS SMALLER THAN NORMAL
AS MODELS AND ENSEMBLES AGREE QUITE WELL WITH DEVELOPMENT AND
EVOLUTION OF AN AMPLIFIED AND STEADILY PROGRESSIVE MID-LATITUDE
FLOW PATTERN FROM THE ERN PACIFIC ACROSS THE LOWER 48 OVER THE
COMING HOLIDAY WEEK. THIS STORMY PATTERN WILL BE HIGHLIGHTED BY
THE INLAND SURGE OF DYNAMIC/COOLING/DESTABILILZING SHORT RANGE ERN
PACIFIC TROUGH ENERGY ALOFT OUT FROM THE INTERMOUNTAIN
WEST/ROCKIES THU OVER/THROUGH A MID-UPPER LEVEL MEAN RIDGE
POSITION BEFORE DIGGING/AMPLIFYING SEWD ACROSS THE CENTRAL US AND
INTO AN ERN SEABOARD BY CHRISTMAS. THIS SETS THE STAGE FOR
POTENTIAL FOR A SIGNIFICANT SWATH OF WINTER PCPN ACROSS THE NATION
AND LEADING TO WELL ORGANIZED HOLIDAY WEEKEND EAST COAST WINTER
STORM CYCLOGENESIS. UPSTREAM FLOW ACROSS THE CENTRAL THEN ERN
PACIFIC BY THEN BECOMES MORE OF A MESS HOWEVER WITH INCREASING
SOLUTION SPREAD...SO FORECAST CONFIDENCE DECREASES RAPIDLY WITH
TIME THERE AND INLAND INTO THE WRN US EVEN THOUGH THE BULK OF
GUIDANCE DOES ALLOW ANOTHER POTENT MID-UPPER LEVEL TROUGH TO REACH
THE WEST COAST CHRISTMAS WEEKEND WITH A RENEWED THREAT FOR MORE
HEAVY PCPN/UNSETTLED WEATHER SLAMMING INLAND.
OVERALL...WHILE GUIDANCE DOES OFFER SOME DIFFERENCES AN OVERALL
SOLUTION CLOSE TO THAT SIMILARILY PROVIDED BY RECENT GFS/ECMWF AND
GFS/ECMWF ENSEMBLE MEANS SEEMS REASONABLE AND RUN TO RUN
CONSISTENT. THE MANUALLY ADJUSTED UPDATED HPC PRELIM GUIDANCE
PACKAGE MAINTAINED CLOSE CONTINUITY WITH ONLY SOME MINOR TWEAKS
FROM OUR EARLIER ISSUANCE. HEAVY SENSIBLE WEATHER FOCUS IS OFTEN
MORE FICKLE AS PER IMPORTANT SMALLER SCALE DIFFERENCES AND
INTERACTIONS THAT STILL FALL WITHIN NOISE LEVELS AT MEDIUM RANGE
TIME SCALES...BUT THE FLOW REGIME CERTAINTY SUPPORTS A BUSY/STORMY
HOLIDAY PERIOD.
CISCO/SCHICHTEL
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GFS Christmas 12" Indiana -
JAC,
12/19/2010, 1:10 pm Post A Reply
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