Preliminary Forecasts
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FXUS02 KWNH 220700
PREEPD

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

VALID 12Z SAT NOV 25 2017 - 12Z WED NOV 29 2017

...GUIDANCE/UNCERTAINTY ASSESSMENT AND PATTERN/WEATHER THREAT
HIGHLIGHTS...

AN ACTIVE PATTERN REMAINS IN PLACE FOR THE PACIFIC NORTHWEST/NRN
CA AND THE NRN INTERMOUNTAIN WEST/ROCKIES AS A SERIES OF ERN
PACIFIC IMPUSLES LIFT INLAND INTO AN AMPLIFIED/WARMING LEAD
W-CENTRAL US MID-UPPER LEVEL RIDGE POSITION. A LEAD CLIPPER SYSTEM
WILL ALSO DELIVER A MIX OF RAIN AND SNOW TO THE UPPER
MIDWEST/GREAT LAKES ON FRIDAY/SATURDAY...WITH SNOW LINGERING
ACROSS THE LOWER GREAT LAKES AND INTERIOR NEW ENGLAND BY THE END
OF THE WEEKEND. THE FOCUS OF ACTIVE WEATHER BY CYBER MONDAY WILL
BE WITH AN AMPLIFIED TROUGH THAT REACHES THE WEST COAST. UNSETTLED
WEATHER WORKS ACROSS THE WRN US/ROCKIES EARLY NEXT WEEK THEN WITH
HEIGHT FALLS INTO THE CENTRAL THEN E-CENTRAL US INTO NEXT
MIDWEEK...SPAWNING SURFACE SYSTEM GENESIS AND ADDITIONAL MODEST
PCPN FOCUS. FARTHER SOUTH...FL WILL FINALLY BE WANING OFF A WET
PATTERN IN TIME FOR THIS WEEKEND AS A FRONTAL LOW LIFTS OFFSHORE.

MODELS AND ENSEMBLES ARE IN GOOD AGREEMENT WITH THE SYNOPTIC
PATTERN EVOLUTION OVER THE NEXT WEEK. THERE ARE LINGERING
DIFFERENCES WITH TIMING AND AMPLITUDE WITH THE EMBEDDED SMALL
SCALE SYSTEMS...BUT ASSOCIATED SURFACE SYSTEM REFLECTIONS AND
WEATHER FOCUS ARE BETTER CLUSTERED NOW. FORECAST SPREAD HAS
DECREASED COMPARED TO THE LAST FEW DAYS AND THE WPC MEDIUM RANGE
PRODUCT SUITE IS MAINLY DERIVED FROM A COMPOSITE BLEND OF THE
REASONABLY COMPATABLE 18/00 UTC GFS/GEFS MEAN AND THE 12 UTC
ECMWF/ECMWF ENSEMBLES.

SCHICHTEL

$$





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