FXUS66 KMFR 252207
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
207 PM PST WED NOV 25 2009
.SHORT TERM...TONIGHT THROUGH SATURDAY...
TONIGHT:
DRY WEATHER WILL CONTINUE TONIGHT AS A 500 HPA RIDGE AXIS PUSHES OFF
TO THE EAST ACROSS THE NORTHERN ROCKIES. IN THE MEANTIME...AN UPPER
LEVEL TROF WILL MOVE CLOSER TO THE FA DURING THE OVERNIGHT HOURS.
AREAS OF FOG WILL BE LIKELY AGAIN TONIGHT AND TOMORROW MORNING ACROSS
THE VALLEYS AND BASINS AS A RATHER STRONG TEMPERATURE INVERSION NOTED
ON THE 12Z MFR RAOB IS STILL EXPECTED TO HOLD ITS OWN THROUGH THE
NEXT 18 TO 24 HOURS OVER THE REGION.
THANKSGIVING:
THE UPPER LEVEL TROF WILL PUSH A COLD FRONT THROUGH THE PACIFIC
NORTHWEST LATE TOMORROW NIGHT INTO EARLY FRIDAY MORNING. THE GOOD
NEWS IS THAT MOST OF THE DAY WILL BE DRY...PARTICULARLY AROUND
TURKEY TIME. THE VALLEY FOG COULD DELAY HEATING SO I DECREASED
TOMORROWS MAXIMUM TEMPERATURES A LITTLE BIT. THE FRONT HAS GOOD
UPPER LEVEL DYNAMICS WITH IT SO AM EXPECTING MOST AREAS TO SEE
RAINFALL LATE THURSDAY NIGHT INTO FRIDAY MORNING. WENT WITH THE GFS
IN THE TIMING OF THE FRONT AS THE NAM SOLUTION SEEMS ANOMALOUS AND
HPC NOTED THIS AS WELL. THERE HAS BEEN A SLOWING TREND IN THE FROPA
SO HAVE ADJUSTED POPS ACCORDING TO MATCH THE SLOWER 12Z FRONTAL
PASSAGE SOLUTION.
FRIDAY:
SNOW LEVELS START TO COME DOWN FRIDAY WITH 1000-700 HPA THICKNESSES
SUPPORTING SNOW LEVELS AROUND 3500-4500 FEET FRIDAY. DO NOT
ANTICIPATE MUCH IN THE WAY OF SNOW ACCUMULATIONS AS THE MOISTURE IS
LIMITED BY THE TIME COLD AIR ADVECTION AND RESULTANT LOWER SNOW
LEVELS KICK IN BEHIND THE MAIN TROF AXIS. STILL THINK THERE WILL BE
A FEW POST FRONTAL SHOWERS VIA COLD AIR ADVECTION...HOWEVER...HAVE
DECREASED POPS TO REFLECT THE 12Z GFS SOLUTION OF QUICKLY BUILDING A
RIDGE IN THE WAKE OF THE SYNOPTIC SYSTEM WITH THE HIGHEST POPS
ACROSS THE CASCADE MOUNTAINS.
THE WEEKEND:
THE WEEKEND DRIES OUT UNDERNEATH A BUILDING UPPER LEVEL RIDGE AXIS.
TEMPERATURES WILL REMAIN MILD TO COOL UNDERNEATH THIS RIDGE WITH
COLD MORNING LOWS. VALLEY AND BASIN FOG WILL BE LIKELY AGAIN AS
ANOTHER TEMPERATURE INVERSION BUILDS OVER THE REGION.
.LONG TERM...SUNDAY THROUGH NEXT WEDNESDAY...
ECMWF AND ENSEMBLE MEAN SHOW THE
LONGWAVE PATTERN IN A SPLIT FLOW REGIME FROM SUNDAY INTO MOST OF
NEXT WEEK. HOWEVER THERE ARE DIFFERENCES WITH RESPECT TO THE TIMING
OF WHEN EACH TROUGH MOVES INTO THE CWA. EITHER WAY...IT LOOKS LIKE A
RATHER QUIET PATTERN AHEAD WITH DRY CONDITIONS PREVAILING MOST DAYS.
THE ONLY EXCEPTION WILL BE MONDAY. THE GFS SHOWS A WETTER SOLUTION...
BUT GIVEN THE TRACK OF THE SHORTWAVE SUSPECT THE QPF SUGGESTED BY THE
GFS MAY BE A BIT OVERDONE. THE ECMWF TRACKS THE TROUGH FARTHER NORTH
AND THUS MORE DRY. FOR NOW HAVE KEPT A SLIGHT CHANCE TO CHANCE POPS
WEST OF THE CASCADES AND DRY EAST MONDAY NIGHT.
&&
.AVIATION...
THE MAIN CONCERN FOR TONIGHT INTO THURSDAY MORNING WILL
BE THE POTENTIAL FOR VALLEY FOG IN THE ROGUE VALLEY...UMPQUA AND
KLAMATH BASIN. THE BEST CHANCE FOR FOG TO DEVELOP WILL BE BETWEEN 5
AND 6Z STARTING WITH REDUCED VISIBILITY AND PATCHY FOG FOLLOWED BY
1/2 MILE OR LESS WITH CIGS AROUND 100 FEET BETWEEN 9 AND 11Z AND
WILL CONTINUE UNTIL 19-20Z BEFORE BREAKING UP IN THE AFTERNOON.
MEANWHILE AT THE COAST THERE IS EVIDENCE THAT MARINE STRATUS WILL
MOVE ALONG THE COAST THIS EVENING...THEN INTO KOTH AFTER 6Z WITH
REDUCED CIGS AND VIS. CIGS AND VIS SHOULD IMPROVE AT KOTH AFTER
16Z.
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH SURF ADVISORY FROM 1 AM THURSDAY TO 4 PM PST FRIDAY FOR
ORZ021-ORZ022.
CA...NONE.
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS FROM 10 AM
THURSDAY TO 10 AM PST FRIDAY FOR PZZ350-PZZ356-PZZ370-
PZZ376.
HAZARDOUS SEAS WATCH FROM THURSDAY EVENING THROUGH FRIDAY
AFTERNOON FOR PZZ350-PZZ356-PZZ370-PZZ376.
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 10 PM THIS EVENING
TO 10 PM PST THURSDAY FOR PZZ356.
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 10 PM PST THURSDAY
FOR PZZ350-PZZ376.
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 10 PM PST THURSDAY
FOR PZZ370.
$$
SHORT=KS
LONG/FIRE=MP
MARINE=DW
