FXUS02 KWBC 262023
PMDEPD
 
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
322 PM EST WED FEB 26 2003
 
VALID 12Z SAT MAR 01 2003 - 12Z WED MAR 05 2003
 
PATTERN AND MODEL OVERVIEW...

MEANS...

BELOW NORMAL UPPER HEIGHTS AND COLD TEMPS WILL BE THE
WATCHWORD FOR MOST OF NOAM DURING THE NEXT 7 DAYS. 
A STRONG RIDGE IN THE GULF OF ALASKA WILL BECOME
RETROGRESSIVE BY D+8...SIGNALING A POSSIBLE PATTERN
CHANGE BY THAT TIME.  

EARLIER TODAY...WE FOLLOWED THE 00Z /06Z GFS FOR SAT DAY 3
AND SUN DAY 4. THE PATTERN REMAINS COMPLICATED
...DOMINATED BY FAST-MOVING SHORTWAVES RACING EWD
ACROSS THE SRN CONUS IN THE SUBTROPICAL JET.  WE STILL DO
NOT SEE ANY IMPULSE AMPLIFYING ENOUGH TO PULL WARM AIR UP
INTO THE CENTRAL/ ERN STATES. WE ACCEPTED THE NEW 12Z GFS 
WITH LOW CONFIDENCE. IT DID TREND MORE TOWARDS THE 00Z/26 
GFS ENSEMBLE MEAN FOR DAYS 6-7... DEPICTING A MUCH
WEAKER/COLDER SYS AFFECTING THE CENTRAL/ERN PORTION OF
THE COUNTRY.

...REGIONAL HIGHLIGHTS...

...E OF THE ROCKIES...

MARCH 2003 WILL CERTAINTY COME IN LIKE A LION FOR THIS PART
OF THE NATION...AND A SHIVERING LION AT THAT! 
IDENTIFYING/TRACKING SHORTWAVES MOVING THRU THE FAST
FLOW ACROSS THE SRN STATES REMAINS A PROBLEM IN OUR
LATEST RELEASE...JUST AS IT WAS THIS MORNING. SPOTTY LIGHT
PCPN IS POSSIBLE DURING THE WEEKEND OVER MUCH OF THE
SERN STATES...BUT HEAVY-VOLUME QPF SHOULD REMAIN OVER
THE GULF COAST REGION. BY  MON DAY 5...THE GFS DELIVERS A
RE-ENFORCING SHOT OF COLD AIR INTO THE NERN QUARTER OF
THE NATION BY MON DAY 5. AN ARCTIC BOUNDARY THEN DEVELOPS
FROM THE LOWER OH VLY EWD TO THE SRN MID ATLANTIC DAYS 6-
7....WITH ONE OR MORE WEAK WAVES LIKELY TO RIPPLE EWD
ALONG THE FRONT.  THICKNESSES APPEAR COLD ENOUGH FOR
STRIPES OF SNOW RIPPLING EWD THRU THE OH VLY/MID ATLANTIC
TO THE N OF THIS BOUNDARY TUE-WED. SURFACE PRES ARE 
A LITTLE LOWER DAY 7 THAN THE NEW 12Z/26 GFS TO ALLOW FOR
MORE SHORTWAVE ENERGY COMING OUT OF THE SWRN STATES
INTO THE PLAINS AT THAT TIME.  THERE MAY BE ADDITIONAL...HARD
TO TIME SURGES OF  PCPN ALONG THE GULF COAST REGION N OF
THE OLD POLAR FRONT MON DAY 5 INTO WED DAY 7...AND THESE
COULD BRING SIGNIFICANT PCPN. 

A NEW ARCTIC HIGH COULD BRING VERY COLD TEMPS BACK INTO
THE N CENTRAL STATES AND WRN GREAT LAKES DAYS 6-7...WITH
SOME OF THIS ARCTIC AIR SPILLING WWD ACROSS THE NRN
ROCKIES INTO ERN WA/OR. SOME UPSLOPE SN POSSIBLE ALONG
THE FRONT RANGE OF THE ROCKIES DAYS 6-7.     

...AK...

A STRONG UPPER RIDGE CENTERED IN THE GULF OF ALASKA THRU
MON DAY 5 WILL KEEP MILD MARITIME AIR DOMINATING THE SRN 3/4
OF THE STATE. REALLY BITTER ARCTIC AIR WILL BE CONFINED N OF
THE BROOKS RANGE. PERIODS OF HEAVY PCPN  WILL HARASS THE
SRN COASTAL AREA ALMOST DAILY...RIGHT INTO TUE DAY 6...
ORIGINATING FROM A SUBTROPICAL CONNECTION FARTHER S. 
FINALLY...IN ABOUT A WEEK...WITH BOTH THE GFS AND ECMWF D+8
SHOWING A TENDENCY FOR THE UPPER RIDGE TO REBUILD OVER
THE ALEUTIANS AND BERING SEA...THE OVERALL PATTERN SHOULD
BEGIN TO DRY OUT/CHILL DOWN OVER THE SRN 3/4 OF THE STATE. 

...WRN US/ROCKIES...

EXPECT COOL MAX TEMPS CONDS UNDER LOW HEIGHTS ALOFT
MOST OF THE NEXT 7 DAYS. EVEN COLDER CONDS ARE POSSIBLE
IN THE PACIFIC NW BY DAY 5...IF ARCTIC AIR SPILLS WWD OVER THE
NRN ROCKIES TOWARDS INTERIOR WA/OR AT THE BEGINNING OF
NEXT WEEK. SOME SN SHOWER ACTIVITY OVER THE CENTRAL
INTERMOUNTAIN REGION SAT DAY 3 WILL EXIT THAT AREA SUN DAY
4 WITH THE DEPARTURE OF A SHORTWAVE.

LATER DAY 4 INTO DAY 7...THE NEW 12Z/26 GFS MAKES A BIG
CONTINUITY CHANGE. IT DROPS SHORTWAVE ENERGY FARTHER W
THAN ITS PREVIOUS RUN INTO THE PACIFIC NW STATES BY MON
DAY 5...AND SWD DOWN THE COAST THEREAFTER. THIS NEW 12Z
GFS SCENARIO HAS SUPPORT FROM THE ECMWF...AND FROM THE
VERY STRONG UPPER RIDGE FORECAST TO BUILD UPSTREAM
OVER THE GULF OF ALASKA. WE ACCEPT MOST OF THIS
CHANGE...WHICH BRINGS MORE PCPN INTO THE NWRN STATES BY
MON DAY 5. WE THEN ALLOW THIS PCPN TO SINK SWD INTO CA AND
THE CENTRAL GREAT BASIN TUE DAY 6 AND WED DAY 7. THE NEW
GFS SCENARIO BRINGS SOME HEAVY PCPN INTO SRN CA BY THE
MIDDLE OF NEXT WEEK WHERE EARLIER RUNS HAD LITTLE
OR NOTHING. WE EXPECT COLDER TEMPS IN THE SWRN STATES TO
GO ALONG WITH LOWER HEIGHTS AND TEMPS. WE THINK THAT THE
UPPER LOW MAY NOT DIG QUITE SO FAR W OFFSHORE FROM CA BY
THE MIDDLE OF NEXT WEEK... AS SUGGESTED BY THE NEW 12Z/26
144HR UKMET.   

...FLOOD

GRAPHICS AVAILABLE ON THE WEB AT http://www.hpc.ncep.noaa.gov

$$