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 $$