Preliminary Forecasts
Issued by NWS

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FXUS02 KWNH 010713
PREEPD

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
213 AM EST SUN MAR 01 2015

VALID 12Z WED MAR 04 2015 - 12Z SUN MAR 08 2015

...GUIDANCE ASSESSMENT AND PATTERN/SENSIBLE WEATHER HIGHLIGHTS...

AN AMPLIFIED MID-UPPER LEVEL TROUGH AND FAR SOUTHWARD PLUNGE OF A
VERY COLD LOWER ATMOSPHERIC AIRMASS WITH RECORD TEMP POTENTIAL
SHOULD SUPPORT LINGERING SNOWS OVER THE S-CENTRAL ROCKIES/HIGH
PLAINS AS AIDED BY UPSLOPE FETCH THAT LINGERS PAST MIDWEEK. THIS
OCCURS WITH NRN/SRN STREAM INTERACTION/PHASING AS IMPULSES DIG TO
THE LEE OF A AMPLIFIED ERN PAC/AK RIDGE. THIS LEADS INTO AN
OVERALL TRANSLATION OF A MAIN TROUGH ALOFT AND ANOMALOUSLY COLD
HIGH PRESSURE SPREADING WELL OVER THE S-CENTRAL THEN ERN STATES
LATE WEEK INTO NEXT WEEKEND. EXPECT A LEAD AND WAVY FRONT WILL
POOL MOISTURE AND FOCUS A POTENTIALLY LARGE SWATH OF MODERATE TO
HEAVIER PCPN ACROSS THE CENTRAL THEN ERN US BOTH IN ADVANCE OF THE
BOUNDARY AND ALSO WRAPPING BACK INTO THE TRAILING/MERGING ARCTIC
AIRMASS...ALL WITH QUITE FAVORABLE RIGHT ENTRANCE REGION UPPER JET
SUPPORT. THIS OFFERS YET ANOTHER SIGNIFICANT AND WIDESPREAD WINTER
PCPN THREAT ON THE NRN PERIPHERY OF THE OVERALL PCPN SHIELD WITH
LEAD AND SECONDARY FRONTAL WAVES ALONG WITH SOME HEAVY WARM SECTOR
RAINS FUELED BY INCREASED GULF INFLOW/CONVERGENCE.

MODELS AND ENSEMBLES CONTINUE TO VARY WITH AMPLITUDE AND TIMING OF
THE WEATHER FEATURES IN THIS NOW DAY 3/4 TIME FRAME. PREFER A
SOLUTION SOMEWHAT ON THE MORE AMPLIFIED AND LESS PROGRESSIVE SIDE
OF THE FULL ENVELOPE OF SOLUTIONS CONSIDERING UPSTREAM FLOW
AMPLITUDE THAT IS WELL SUPPORTED BY LATEST PACIFIC WATER VAPOR
LOOPS. ACCORDINGLY...THE WPC MEDIUM-RANGE PRODUCT SUITE WAS
PRIMARILY DERIVED FROM A COMPOSITE BLEND OF THE 18 UTC GEFS
MEAN...12 UTC NAEFS MEAN...WPC CONTINUITY...AND YESTERDAYS 00 UTC
ECMWF ENSEMBLE MEAN THAT WAS LESS PROGRESSIVE AND MORE AMPLIFIED
THAN THE 12 UTC ECMWF/ECMWF ENSEMBLE MEAN. THE LATEST 00 UTC ECMWF
HAS TRENDED MORE BACK IN LINE WITH THE WPC SOLUTION.

THIS ENSEMBLE MEAN FORECAST BLENDED FORECAST APPROACH SHOULD
CONTINUE TO WORK WELL AS THE PATTERN BECOMES MORE BENIGN AND DRY
FOR MUCH OF THE NATION FOR THE REST OF THE MEDIUM-RANGE FORECAST
PERIOD LATE WEEK INTO NEXT WEEKEND.

SCHICHTEL

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