Prognostic Meteorological Discussion
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000
FXUS02 KWBC 301558
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1057 AM EST FRI JAN 30 2015

VALID 12Z MON FEB 02 2015 - 12Z FRI FEB 06 2015

...OVERVIEW...

GUIDANCE STILL ADVERTISES THAT THE MEAN PATTERN WILL SETTLE INTO A
MORE AMPLIFIED ERN TROUGH... WEST COAST RIDGE DRIFTING A LITTLE
INLAND... AND BROAD ERN PAC TROUGH.  CONFIDENCE IN THE LARGE SCALE
FLOW IS ABOVE AVG GIVEN MULTIPLE DAYS OF D+8 CHARTS BEING
REMARKABLY AGREEABLE AND CONSISTENT WITH ASSOC HGT ANOMALY CENTERS
FROM WRN NOAM BACK THROUGH THE EXTREME NWRN PACIFIC.  WITHIN THIS
PATTERN THERE ARE STILL SOME DETAILS THAT HAVE GREATER UNCERTAINTY
THOUGH.


...GUIDANCE EVALUATION AND PREFERENCES...

FROM DAY 3 MON INTO DAY 4 TUE A GENERAL CONSENSUS BLEND OF THE 06Z
GFS/00Z ECMWF AND THEIR CORRESPONDING ENSEMBLE MEANS REPRESENTS
THE MOST AGREEABLE IDEAS OF GUIDANCE OR BEST INTERMEDIATE SOLN AS
THE CASE MAY BE.  SOLNS CONTINUE TO VARY FROM RUN-RUN AND/OR
DAY-DAY REGARDING THE SYSTEM FCST TO TRACK FROM THE EAST COAST
INTO THE WRN ATLC DURING THE DAY MON.  ON A MULTI-DAY BASIS TRENDS
HAVE BEEN FROM WEAK/FAST TO SLOWER/STRONGER BACK TO WEAK/FAST AND
NOW TO MODERATELY STRONG/SLOW BUT NOT QUITE TO THE POINT OF THE
MAJORITY CLUSTER FROM MON NIGHT THROUGH TUE NIGHT RUNS.
SUPPORTING ENERGY IS POISED TO REACH WRN CANADA SHORTLY SO
HOPEFULLY MODEL SOLNS WILL BEGIN TO STABILIZE OVER THE NEXT 12-24
HRS.  MEANWHILE GUIDANCE IS SLOWLY COMING INTO BETTER AGREEMENT
WITH TRACKING AN ERN PAC WAVE TO OR N OF VANCOUVER ISLAND WITH A
MERE FRONT REACHING THE PAC NW... IN CONTRAST TO EARLIER ISOLD
SOLNS THAT HAD TRACKED A WAVE FARTHER SWD.  FINALLY THE FAVORED
BLEND YIELDS A GOOD COMPROMISE BTWN THE NWD 00Z ECMWF AND SWD GFS
RUNS FOR THE WAVE/FRONT OVER THE NRN PLAINS.  CONSULT THE MODEL
DIAGNOSTIC DISCUSSION PMDHMD FOR UPDATED PREFS INCORPORATING NEW
12Z GUIDANCE THROUGH 00Z TUE.

DAYS 5-7 WED-FRI START WITH A 60/40 BLEND OF THE 00Z ECMWF
MEAN/00Z GEFS MEAN TO RESOLVE MULTIPLE FCST UNCERTAINTIES FOR
WHICH OPERATIONAL SOLNS ARE QUITE DIVERSE.  AS WITH THE EARLY EAST
COAST SYSTEM... THERE HAVE BEEN SOME MULTI-DAY OSCILLATIONS WITH
HOW MUCH ERN PAC ENERGY FILTERS THROUGH THE WEST COAST MEAN RIDGE
EARLY-MID PERIOD WHICH IN TURN AFFECTS THE SEWD PROGRESSION OF THE
WAVE/FRONT AND TRAILING HIGH PRESSURE OVER THE CNTRL CONUS AS OF
DAY 4 TUE... WITH LATEST GUIDANCE SHOWING A LITTLE MORE FLATTENING
OF THE RIDGE THAN 24 HRS AGO BUT MORE SIMILAR TO SOME EARLIER
GUIDANCE.  THIS ADJUSTMENT RESULTS IN CNTRL-ERN CONUS FRONTAL
TIMING SLOWER THAN PRIOR CONSENSUS.  AHEAD OF THIS FRONT IS
ONGOING UNCERTAINTY OF TRACK/TIMING OF SFC WAVINESS ASSOC WITH THE
UPR LOW EJECTING FROM MEXICO.  OPERATIONAL MODELS ARE STILL
SHOWING A STRONG ENOUGH SIGNAL TO SUPPORT DECENT POTENTIAL FOR A
WELL DEFINED WAVE BUT THUS FAR SUFFICIENTLY POOR
CONTINUITY/AGREEMENT TO PRECLUDE USE OF ANY OPERATIONAL SOLN.  THE
PREFERRED BLEND PROVIDES A GOOD CONSERVATIVE STARTING POINT WITH
SOME WAVINESS FROM THE GULF OF MEXICO INTO WRN ATLC.  ALONG THE
NRN HALF OF THE WEST COAST SOLNS ARE FAIRLY SIMILAR IN SHOWING A
STRENGTHENING SFC GRADIENT REGARDLESS OF EXACT DETAILS OF DEEP LOW
PRESSURE TRACKING CLOSE TO 140W BY LATE NEXT WEEK.


...SENSIBLE WEATHER HIGHLIGHTS...

WITH THE SYSTEM PASSING OFF THE EAST COAST ON MON HEADING INTO THE
SHORT RANGE TIME FRAME... HEAVIEST PCPN DURING THE PERIOD WILL BE
FOCUSED ON OPPOSITE SIDES OF THE LOWER 48.

AREAS FROM THE PAC NW INTO THE NRN ROCKIES SHOULD SEE AT LEAST A
COUPLE PERIODS OF LOCALLY ENHANCED PCPN PRIMARILY DURING MON-WED
AS ENERGY PASSES THROUGH/AROUND THE WEST COAST MEAN RIDGE.  INLAND
AREAS SHOULD THEN TREND DRYER AS THE RIDGE AXIS DRIFTS EWD.  THIS
EWD DRIFT IN THE RIDGE WILL INCREASE SWLY FLOW ALOFT INTO THE
CNTRL-NRN WEST COAST BY THU-FRI AND LEAD TO INCREASED PCPN FROM
NRN CA NWD.  CURRENT GUIDANCE SUGGESTS SOME OF THE MSTR MAY
ORIGINATE FROM THE TROPICAL PACIFIC SO THERE IS POTENTIAL FOR HVY
RNFL NEAR THE COAST.  IN GENERAL SNOW LVLS OVER THE WEST SHOULD
RISE WITH TIME AS THE MEAN RIDGE GRADUALLY BUILDS WWD.

SOME LOCATIONS FROM THE WRN GULF COAST THROUGH THE SOUTHEAST/EAST
COAST MAY SEE ENHANCED RNFL FROM THE UPR LOW EJECTING FROM MEXICO
AND ASSOC SFC WAVE.  CONFIDENCE REMAINS LOW IN SPECIFICS DUE TO
HIGH GUIDANCE SPREAD BUT THERE IS GREATER CONFIDENCE IN THE
GENERAL OCCURRENCE OF AN ENHANCED EVENT DURING THE TUE-THU TIME
FRAME.  IT STILL APPEARS TO BE A CLOSE CALL AS TO WHETHER THE MSTR
SHIELD WILL EXTEND FAR ENOUGH NWWD TO YIELD SOME WINTRY PCPN...
WITH PROBABILITIES REMAINING LOWER THAN 50 PCT AT THIS TIME.
FARTHER INTO THE COLDER AIR EXPECT PERIODS OF LAKE EFFECT ACTIVITY
PLUS ONE OR TWO PERIODS OF LGT TO LCLY MDT SNOWFALL NRN PLAINS EWD.

TEMPS OVER THE WEST SHOULD BE ABOVE NORMAL DURING THE PERIOD WITH
GREATEST ANOMALIES OF PLUS 10-20F LIKELY CNTRD OVER/NEAR THE
GRTBASIN.  THE PLAINS WILL BE MORE VARIABLE WITH WARMEST DAYS
BEING MON-TUE AND FRI OVER NRN-CNTRL LOCATIONS.  THE EAST WILL SEE
TWO SEPARATE COLD AIRMASSES... ONE EARLY IN THE WEEK AND ANOTHER
PROGRESSING FROM THE MS VLY INTO THE EAST THU-FRI.  IN BOTH CASES
THERE SHOULD BE DECENT COVERAGE OF MINUS 10-20F ANOMALIES WITH
GREATER EXTREMES PSBL.

RAUSCH

$$





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