FXUS02 KWBC 061848
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
147 PM EST TUE JAN 06 2009

VALID 12Z FRI JAN 09 2009 - 12Z TUE JAN 13 2009

PATTERN CHANGE UNDERWAY TO A +PNA PATTERN THIS PERIOD OVER NOAM
BECOMING ESTABLISHED AROUND DAYS 4-5 SAT/SUN AS RIDGING BUILDS IN
THE ERN PAC AND A TROF FORMS OVER THE ERN HALF OF CONUS. TYPICAL
DIFFERENCES OCCUR BETWEEN MODEL SOLUTIONS HANDLING SHORTWAVE
ENERGY COMING INTO THE WEST COAST AND SWRN CONUS EARLY IN THE
PERIOD AND AGAIN LATER AS ENERGY COMES OVER THE TOP OF THE
EPAC/WRN CONUS RIDGE.

PLACEMENT OF THE MEAN TROF OVER THE ERN HALF TO THIRD OF CONUS
BECOMES UNCERTAIN AS THE EPAC/WRN CONUS RIDGE ESTABLISHES ITSELF.
THE POSITIVE HT ANOMALY LOCATION AND RIDGE AXIS BECOMES CRITICAL
AS TO THE LOCATION OF THE DOWNSTREAM TROF...CLOSER TO THE WEST
COAST THE MORE EWD THE DOWNSTREAM TROF. BY LATE PERIOD 00Z OP GFS
AMPLIFIES ITS DOWNSTREAM TROF ALONG 100W WITH ITS ENS MEAN CLOSER
TO 85W. OP 00Z ECMWF HAS ITS OP TROF ALONG 85W WHILE ITS ENS MEAN
IS CLOSER TO 90W. BUT THE 00Z ECMWF SHIFTS ITS EPAC RIDGE TO ALONG
THE CA COAST WHICH IS LOGICAL. AN OFFSHORE TELECONNECTION OF THE
RIDGE TO NR 50N 135W SUGGEST A MORE WWD MID NATION TROF AS PER 00Z
ECMWF ENS MEAN WHILE THE GFS ENS MEAN IS TOO FAR EAST. THIS ALL
REMAINS UNCERTAIN AND POSSIBLY JUST TRANSIENT AS THE LONGER TERM
MEANS BY DAYS 8-9 SUGGEST KEEPING THE RIDGING ALONG 130W WHICH
TELECONNECTS TO A MEAN TROF AXIS IN THE MS VALLEY ALONG 90W AND
BOTH GFS AND ECMWF ENS MEANS SUGGEST KEEPING THIS MEAN TROF IN
THIS AREA. THIS UNCERTAINTY LEADS US TO A USE OF THE OP 00Z ECMWF
FOR DAYS 3-5 BLENDING IN A SIG PORTION OF THE ECMWF 00Z ENS MEAN
DAYS 6 AND 7 MON/TUES.

12Z MODEL GUIDANCE GFS/CMC/UKMET VARY SIGNIFICANTLY ESPECIALLY
HANDLING NERN PAC ENERGY IN THE GLFAK AS 12Z GFS BODILY DRIVES THE
EPAC RIDGE AXIS UP ALONG THE CANADIAN/SERN AK COAST BY DAY 6 WHICH
SHARPENS THE RIDGE AND ALLOWS FOR A MORE N-S FLOW DRIVING ITS JET
AXIS DUE SWD THRU THE FOUR CORNERS REGION WHILE PICKING UP THE
SWRN CONUS SHORTWAVE AND TAKING IT NEWD INTO TX AND CARVING OUT
ANOTHER SEPERATE CLOSED LOW OVER NWRN MEXICO BY DAY 7....VERY
DIFFERENT FROM ITS PRIOR RUN. ITS 12Z GFS ENS MEAN ORIENTS ITS
DOWNSTREAM TROF FOR DAYS 6 AND 7 WELL WWD OF ITS PRIOR RUN AND WWD
OF THE 00Z ECMWF ENS MEAN BUT LEAVES ITS OFFSHORE RIDGE AXIS
CLOSER TO THE ORIENTATION OF PRIOR GFS AND ECMWF ENS MEANS.

UKMET LEAVES BACK ALTOGETHER THE CLOSED SWRN CONUS SHORTWAVE IN
THE NRN GLFCA WHILE KEEPING THE MAIN DOWNSTREAM TROF EWD ALONG 80W
BY DAY 6. CMC FOLLOWS ITS PRIOR CONTINUITY AND LOOKS SIMILAR TO
THE 12Z GFS THRU 144 HRS.

12Z ECMWF FOLLOWS ITS PRIOR RUN LEAVING BEHIND A SHEARED OUT MID
LEVEL TROF OVER NWRN MEXICO BY DAY 5 SUN.

NOT WILLING AT THIS TIME TO BUY OFF ON THE RADICAL CHANGE OF GFS
TOWARDS THE CMC SOLUTION OF SHORTWAVE PHASING IN THE SRN HIGH
PLAINS. WILL MAKE SOME MANUAL CHANGES TO SFC PROGS INCORPORATING
THE POTENTIAL OF HOLDING WWD THE MEAN CONUS TROF DAYS 6 AND 7 WITH
POSSIBLE GLFMEX SFC WAVE DEVELOPMENT.

AN ELONGATED AREA OF LOW PRESSURE IN THE NRN AND CENTRAL PLAINS
DAY 3 FRI WILL BECOME MORE CONSOLIDATED WITH A MEAN LOW TRACKING
EWD ACROSS SAT IL/IN/OH SAT EXITING OFF THE NY BIGHT/SRN NEW ENG
COAST SAT NIGHT LEAVING BEHIND A SWATH OF LT SNOW TO TEH NORTH OF
ITS TRACK.
A TRAILING COLD FRONT WILL MOVE EWD FROM THE SRN PLAINS TO THE
SERN SEABOARD SUN WHERE IT WILL SLOW AND AS PER RECENT ECMWF RUNS
HAVE ENOUGH EJECTING MID LEVEL IMPULSE IN THE BASE OF THE TROF TO
INDUCE A FRONTAL WAVE OR SERIES OF FRONTAL WAVES ALONG AND
OFFSHORE OF THE SOUTHEAST COAST SUN INTO TUES.

BUILDING EPAC/PAC NORTHWEST HTS END THE WET SPELL FOR THE PAC
NORTHWEST REGION BY SHIFTING IT NWD INTO B.C. PAC HIGH PRESSURE
WILL BUILD INTO THE LOWER GREAT BASIN SRN AND CENTRAL ROCKIES OVER
THE WEEKEND PROVIDING AN OFFSHORE FLOW EVENT/MODERATE SANTA ANA
OVER CENTRAL AND SRN CA.

FAIRLY STRONG COLD AIR SHORT DRIVES INTO THE PLAINS FRI AND SAT
AND EWD TO THE ERN SEABOARD BY SUNDAY. ANOTHER POTENTIALLY MUCH
STRONGER SURGE OF COLD AIR BEGINS TO NOSE SWD FROM WRN CANADA MON
INTO THE DAKOTAS DAY 7 TUES AND DEEPER PLUNGE MID WEEK AS MOST
GUIDANCE INDICATES AT LEAST A 1045 MB HIGH COMING SEWD OUT OF
CANADA.
ROSENSTEIN
$$