THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


EXTENDED FORECAST DISCUSSION




EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1046 AM EST TUE MAR 03 2015

VALID 12Z FRI MAR 06 2015 - 12Z TUE MAR 10 2015

...OVERVIEW AND GUIDANCE EVALUATION/PREFERENCES...

GUIDANCE OFFERS BETTER THAN AVG AGREEMENT FOR LARGE SCALE FLOW.  A
MEAN RIDGE OVER THE WEST COAST/ERN PAC WILL SUPPORT A DOWNSTREAM
TROUGH OF MODERATE AMPLITUDE FOR MOST OF THE PERIOD.  THE RIDGE
SHOWS SIGNS OF SOME EWD PROGRESSION BY DAY 7 TUE WITH D+8
MULTI-DAY MEANS HINTING AT SPLIT FLOW OVER THE CONUS WITH THE
COMBINATION OF THIS RIDGE AND SRN ROCKIES/PLAINS INTO NRN MEXICO
TROUGHING.  ASSOC SFC FEATURES WILL PRIMARILY BE A SERIES OF
FRONTS CROSSING SRN CANADA/CNTRL-ERN CONUS AND A MEAN FRONTAL
BNDRY EXTENDING FROM THE WRN ATLC ACROSS THE FL PENINSULA AND SWWD
THROUGH THE GULF OF MEXICO.  THIS PATTERN SHOULD LEAD TO LOWER
THAN AVG COVERAGE OF PCPN OVER THE LOWER 48.

DURING DAYS 3-5 FRI-SUN A BLEND OF THE 06Z GFS/GEFS MEAN AND 00Z
ECMWF/ECMWF MEAN REPRESENTS CONSENSUS WELL.  THERE ARE SOME SHRTWV
DETAIL DIFFS WITH ENERGY EJECTING FROM THE SRN ROCKIES/PLAINS AS
WELL AS WITHIN THE NRN STREAM BUT EFFECTS AT THE SFC APPEAR
MINIMAL EXCEPT OVER THE WRN ATLC BY EARLY DAY 5 SUN.

THE PREFERRED BLEND ADJUSTS TO AN EVEN WEIGHTING OF THE 06Z
GEFS/00Z ECMWF MEANS FOR DAYS 6-7 MON-TUE WITH DECREASING
CONFIDENCE IN OPERATIONAL RUNS.  THE 00Z ECMWF... WHICH FORMS A
CLOSED LOW ALOFT OVER THE SRN PLAINS EARLY NEXT WEEK... IS QUITE
DIFFERENT FROM PREVIOUS RUNS AND ITS OVERALL TROUGH AXIS IS FASTER
THAN MOST MODELS/ENSMEANS.  THAT RUN ALSO BECOMES FLATTER THAN
CONSENSUS WITH THE NERN TROUGH BY LATE MON.  THE 06Z GFS IS
SOMEWHAT STRONGER THAN MOST OTHER SOLNS WITH ENERGY OVER/NEAR CA
AROUND MON.  FINALLY BY DAY 7 TUE SOME TIMING DIFFS ARISE WITH THE
UPR RIDGE COMING INTO THE NORTHWEST.  THE 00Z ECMWF MEAN IS A
LITTLE ON THE SLOWER SIDE RELATIVE TO THE FULL GUIDANCE SPREAD BUT
THE 06Z GFS/GEFS MEAN HAVE TRENDED SLOWER FROM THEIR 00Z RUNS.  IT
MAY TAKE UNTIL LATE IN THE PERIOD FOR THE UPR LOW NEAR 150W TO
BEGIN RESPONDING TO AMPLIFYING FLOW TO THE N SO TIMING IN THE
SLOWER HALF OF THE SPREAD SEEMS REASONABLE AT THIS TIME.  HOWEVER
NOTE THAT CURRENT DIFFS ARE WITHIN THE TYPICAL ERROR RANGE FOR A
DAY 7 FCST. 


...SENSIBLE WEATHER HIGHLIGHTS...

AN AREA COVERING MOST OF THE ERN CONUS THROUGH THE SRN HALF OF THE
MS VLY INTO THE SRN PLAINS SHOULD SEE WELL BELOW NORMAL TEMPS ON
FRI.  THE COLD AIR MAY BE RATHER STUBBORN OVER THE SRN PLAINS
AFTER FRI BUT ELSEWHERE MODERATION SHOULD OCCUR MORE QUICKLY.  ON
FRI MORNING THE COMBINATION OF NEW SNOW AND SFC HIGH PRES MAY LEAD
TO LOWS OF 20-40F BELOW NORMAL FROM NEAR ARKANSAS NEWD INTO THE
GRTLKS AND NRN MID ATLC.  SUCH READINGS MAY BREAK DAILY RECORD
LOWS AT SOME LOCATIONS AND PSBLY CHALLENGE RECORD LOWS FOR THE
MONTH OF MARCH.  EXPECT DAYTIME HIGHS ON FRI TO BE 15-25F BELOW
NORMAL OVER THE EAST/SOUTH.  MEANWHILE EXPECT CONTINUED WARMTH
OVER THE WEST WITH TEMPS MOSTLY 5-15F ABOVE NORMAL.  SOME OF THIS
WARM AIR SHOULD ALSO EXTEND THROUGH THE NRN PLAINS WHERE ANOMALIES
MAY REACH PLUS 10-20F EARLY NEXT WEEK. 

THE ONE AREA BEING MONITORED FOR HEAVIER PCPN POTENTIAL IS ALONG
AND INLAND FROM THE GULF COAST/SOUTHEAST COAST WHERE THERE IS A
FAIR AMOUNT OF SPREAD OVER THE NWD EXTENT OF RNFL.  LOW
PREDICTABILITY OF IMPORTANT SHRTWV DETAILS TEMPERS CONFIDENCE IN
SPECIFICS BUT AN AGREEABLE FCST OF AN UPR TROUGH REACHING THE SRN
PLAINS/NRN MEXICO SHOULD AT LEAST PROMOTE AN INCREASE OF MSTR. 
FARTHER NWD AREAS OF MOSTLY LGT SNOW MAY PROGRESS FROM THE EXTREME
NRN PLAINS THROUGH THE GRTLKS/NEW ENG IN ASSOC WITH A SERIES OF
SFC FRONTS.  OVER THE WEST... PARTS OF THE ROCKIES MAY SEE A
LITTLE LGT PCPN IN THE FIRST HALF OF THE PERIOD AND THE ERN
PERIPHERY OF AN ERN PAC MSTR SHIELD MAY REACH THE WEST COAST BY
EARLY NEXT WEEK.

RAUSCH





Last Updated: 1046 AM EST TUE MAR 03 2015