Prognostic Meteorological Discussion
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000
FXUS02 KWBC 011600
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1059 AM EST SUN FEB 01 2015

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

...OVERVIEW AND PREFERENCES...

LATEST SOLNS MAINTAIN REMARKABLY GOOD AGREEMENT AND CONTINUITY
WITH THE EXPECTED MEAN FLOW THROUGH THE PERIOD... LEADING TO ABOVE
AVG CONFIDENCE IN THE LARGE SCALE FCST.  A FAIRLY STRONG RIDGE
MOVING INTO THE WEST WILL SUPPORT ERN CONUS TROUGH AMPLIFICATION
WED-FRI.  BY SAT-SUN A BUNDLE OF ERN PAC ENERGY REACHING THE WEST
IS FCST TO BROADEN THE WRN RIDGE BRIEFLY BEFORE AMPLIFYING INTO
THE E-CNTRL CONUS BY THE END OF NEXT WEEKEND.  ANOTHER ERN PAC
SHRTWV MAY APPROACH THE WEST COAST LATE SUN AS WELL.  IN SPITE OF
THE AGREEABLE/CONSISTENT MEAN FCST THERE ARE LINGERING
MEDIUM-SMALLER DETAIL UNCERTAINTIES.  THESE ARE BEST RESOLVED BY A
00Z MODEL/ENSEMBLE BLEND DAYS 3-5 WED-FRI... WITH A 40/40/20 BLEND
OF THE 00Z NAEFS MEAN/ECMWF MEAN/ECMWF HELPING TO MAINTAIN
CONTINUITY DAYS 6-7 SAT-SUN.


...GUIDANCE EVALUATION...

TO THE WEST OF THE ROCKIES THE PRIMARY FCST ISSUES ARISE FRI-SUN
AS ERN PAC SHRTWV ENERGY APPROACHES AND PASSES THROUGH/AROUND THE
WRN CONUS MEAN RIDGE.  AMONG LATEST GUIDANCE THE 06Z GFS SEEMS
PARTICULARLY AGGRESSIVE WITH ITS SHRTWV FROM DAY 5 FRI ONWARD...
WITH A RESULTING STRONGER SFC GRADIENT ALONG THE PAC NW COAST ON
FRI.  ANOTHER FEATURE IS FCST TO TRACK OFF THE PAC NW COAST DAY 7
SUN WITH THE 06Z GFS FASTER THAN CONSENSUS FOR THE ASSOC SFC
REFLECTION.  THE PREFERRED 00Z GFS/ECMWF AND ENSMEAN CONSENSUS
WED-FRI AND ECMWF/NAEFS-BASED BLEND SAT-SUN REPRESENTS THE MOST
COMMON ASPECTS OF GUIDANCE... STAYING AWAY FROM THE LESS CONFIDENT
ASPECTS OF THE 06Z GFS.

FARTHER EWD THERE ARE TWO SIGNIFICANT FCST CHALLENGES.  THE FIRST
COVERING WED-FRI IS THE COMBINED UNCERTAINTY OF UPR TROUGHING
HEADING INTO THE EAST AND LEADING TROUGH/UPR LOW EJECTING FROM
NEAR THE RIO GRANDE VLY.  THE SECOND... FRI-SUN... INVOLVES THE
SFC PATTERN FROM THE NRN PLAINS SEWD AS INFLUENCED BY SRN CANADA
FLOW AND THEN ERN PAC ENERGY AMPLIFYING INTO THE E-CNTRL CONUS.

MODEL/ENSEMBLE SPREAD AND RUN TO RUN DIFFS ARE STILL CONSIDERABLE
WITH THE SFC EVOLUTION FROM THE GULF OF MEXICO/SRN CONUS INTO THE
WRN ATLC... RELATED TO SENSITIVITY IN HANDLING ERN CONUS TROUGHING
AND LEADING EJECTING SRN STREAM FEATURE.  TO SOME DEGREE THE
LATEST GFS/ECMWF RUNS HAVE SWITCHED PLACES VS YDAY IN TERMS OF
WHICH TRACKS THE INITIAL GULF OF MEXICO SFC WAVE FARTHER NWWD.  AS
WAS THE CASE 24 HRS AGO THE 00Z UKMET/CMC SHOW THE FARTHEST NWWD
TRACK AMONG OPERATIONAL SOLNS.  CONFIDENCE IN ANY SPECIFIC SOLN IS
FAIRLY LOW AT THIS TIME AS EVOLUTION ALOFT WILL DEPEND IN PART ON
HOW MUCH INTERACTION THERE MAY BE BTWN NRN STREAM FLOW AND ENERGY
AMPLIFYING INTO THE SRN STATES.  THE LATTER ORIGINATES FROM
WEAK/DIFFUSE ENERGY WITHIN FLAT FLOW REACHING THE WEST COAST
AROUND TUE SO THERE IS A RISK THAT THIS PART OF THE FCST MAY
REMAIN UNRESOLVED FOR AT LEAST ANOTHER 2-3 DAYS.

BY THE LATTER HALF OF THE PERIOD MAJOR DIFFS DEVELOP WITH THE POSN
OF SRN CANADA HIGH PRES AND FRONTAL BNDRY/SFC LOW TO THE S.  WITH
THE SFC LOW THAT SHOULD GAIN DEFINITION BY DAY 7 SUN AS UPSTREAM
ENERGY ALOFT BEGINS TO AMPLIFY... ENSEMBLE SPREAD AS OF 12Z SUN
RANGES FROM THE MID MS VLY N/NW TO THE CANADIAN BORDER.  THE PAST
TWO ECMWF RUNS HAVE SETTLED UPON A FAIRLY SUPPRESSED SCENARIO
AFTER TWO WILDLY DIFFERENT RUNS WHILE THE PAST 2-3 ECMWF MEANS
HAVE DRIFTED A LITTLE SWD CLOSE TO WHERE THE 00Z ECMWF IS NOW.
THE 06Z GEFS MEAN ADJUSTED SOMEWHAT SWD FROM THE 00Z-06Z GFS/00Z
GEFS CLUSTER SO THERE IS GRADUALLY INCREASING SUPPORT FOR A FAIR
DEGREE OF SUPPRESSION.  THE PREFERRED BLEND INCORPORATING THE
NAEFS/ECMWF MEANS AND A SMALL AMT OF 00Z ECMWF YIELDS GOOD
CONTINUITY GIVEN SOMEWHAT MORE CONFIDENCE IN THIS IDEA THAN ANY
ALTERNATIVE SOLN.


...SENSIBLE WEATHER HIGHLIGHTS...

OVER THE WEST... AFTER ONE PCPN EVENT TAPERS OFF OVER THE NRN HALF
OF THE ROCKIES AT THE START OF THE PERIOD THE MAIN FOCUS WILL BE
ON THE POTENTIAL FOR PERIODS OF ENHANCED PCPN FROM NRN CA AND THE
PAC NW INTO THE NRN ROCKIES THU ONWARD.  GUIDANCE CONTINUES TO
SHOW THAT SOME SUPPORTING MSTR SHOULD ORIGINATE FROM THE TROPICAL
PACIFIC SO HVY TOTALS ARE PSBL ESPECIALLY FROM NRN CA INTO THE PAC
NW.  TIMING/EXACT LOCATION OF HEAVIEST AMTS WILL DEPEND ON SMALLER
SCALE SHRTWV DETAILS THAT WILL TAKE SOME TIME TO RESOLVE.  THERE
IS LOWER CONFIDENCE IN NRN ROCKIES SPECIFICS... WITH GFS RUNS
STILL TENDING TO BE STRONGER WITH SHRTWV ENERGY ROUNDING THE MEAN
RIDGE AND THUS HEAVIER WITH AMTS.  TELECONS RELATIVE TO STABLE HGT
ANOMALY CNTRS CONTINUE ONLY TO HINT AT A SECONDARY PCPN MAX IN THE
NRN ROCKIES VERSUS PRIMARY EMPHASIS ALONG THE WEST COAST.  TEMPS
SHOULD BE ABOVE NORMAL WITH PLUS 10-20F ANOMALIES MULTIPLE DAYS
OVER THE INTERIOR WEST/ROCKIES.

LOCATIONS ALONG THE GULF COAST AND OVER FL MAY SEE A PERIOD OF
LOCALLY MDT-HVY RNFL DURING THE FIRST HALF OF THE PERIOD... WITH
CONTINUED UNCERTAINTY ABOUT WHETHER THE MSTR SHIELD COULD EXTEND A
LITTLE FARTHER NWWD INTO THE SOUTHEAST.  AT THE SAME TIME A BAND
OF PCPN MAY ACCOMPANY THE FRONT DROPPING SEWD FROM THE
GRTLKS/S-CNTRL PLAINS.  AN AREA OF SNOW MAY DROP INTO THE NRN
TIER/GRTLKS FRI ONWARD WITH A FRONT DROPPING INTO THE REGION AND
LOW PRES FCST TO REACH THE E-CNTRL CONUS BY SUN.  CHILLY AIRMASS
CROSSING THE ERN HALF OF THE CONUS WED-FRI SHOULD BRING 10-20F
BELOW NORMAL READINGS FOR A LEAST A DAY... WITH A COLD HIGH OVER
SRN CANADA BRINGING SIMILAR ANOMALIES INTO THE UPR GRTLKS/NEW
ENGLAND NEXT SUN.  THE NRN-CNTRL PLAINS WILL BE QUITE WARM WITH
SOME READINGS PSBLY NEARING DAILY RECORD VALUES.

RAUSCH

$$




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