FXUS66 KMFR 042223
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
223 PM PST THU DEC 4 2008

.SHORT TERM...AN UPPER RIDGE IS OVER THE REGION THIS AFTERNOON
WITH A THERMAL TROUGH ALONG THE COAST. THE THERMAL TROUGH IS
BRINGING DRY OFFSHORE EAST TO NORTHEAST FLOW TO THE AREA. THE
OFFSHORE FLOW HAS ERODED THE FOG AND LOW CLOUDS OVER THE AREA WITH
THE EXCEPTION OF AREAS OF LOW CLOUDS AND PATCHY FOG IN THE
ROGUE...ILLINOIS..AND UMPQUA VALLEYS.

STRONG HIGH PRESSURE CONTINUES TONIGHT INTO FRIDAY WITH A STABLE
INVERSION PATTERN EXPECTED. TONIGHT THE THERMAL TROUGH CONTINUES TO
PERSIST ALONG THE COAST WITH THE GRADIENT WEAKENING LATE FRIDAY
MORNING. THIS WILL ALLOW CONTINUED OFFSHORE EASTERLY WINDS OVER
THE HIGHER TERRAIN ACROSS MUCH OF THE AREA. EXPECT FOG TO
REDEVELOP IN VALLEYS WEST OF THE CASCADES TONIGHT AND TOMORROW
MORNING...HOWEVER EASTERLY WINDS MAY LIMIT DEPTH OF THE FOG LAYER
AND KEEP THE FOG COVERAGE DOWN A BIT. EXPECT FOG TO CLEAR IN
MOST VALLEYS TOMORROW EXCEPT FOR SOME AREAS OF LOW CLOUDS
LINGERING IN THE ILLINOIS...ROGUE...AND PORTIONS OF THE UMPQUA
VALLEY.

THEN...LATE FRIDAY INTO SATURDAY THE RIDGE WEAKENS SLIGHTLY AS A
FRONTAL SYSTEM MOVES INTO BRITISH COLOMBIA AND PORTIONS OF
WASHINGTON...HOWEVER HIGH PRESSURE REMAINS OVER SOUTHWEST OREGON
BRINGING A CONTINUED PATTERN OF AREAS OF OVERNIGHT AND MORNING VALLEY
FOG FOR LOCATIONS WEST OF THE CASCADES WITH MOSTLY CLEAR SKIES
ELSEWHERE.


.LONG TERM...A SHORTWAVE WILL MOVE NORTH OF THE CWA ON
SUNDAY. THE GFS IS WEAKER AND IS TRACKING IT FURTHER NORTH COMPARED
TO THE ECMWF. FOR NOW HAVE LEANED TOWARDS THE ECMWF SOLUTION WHICH
IS LEANING MORE WETTER AND COOLER. THE RIDGE NUDGES BACK TOWARDS THE
CWA MONDAY WITH DRY AND STABLE CONDITIONS RETURNING. THE ECMWF
BRINGS ANOTHER SHORTWAVE NORTH OF THE CWA TUESDAY AFTERNOON WHILE
THE GFS HAS THE RIDGE AXIS OVER THE REGION. EITHER WAY...IT LOOKS
LIKE DRY AND STABLE CONDITIONS WILL CONTINUE WITH THE RETURN OF LOW
CLOUDS AND FOG IN THE VALLEYS AND PARTLY CLOUDY SKIES OVER THE
RIDGES FOR THE FIRST HALF OF NEXT WEEK. HAVE LEANED TOWARDS THE
ECMWF FOR THE SECOND HALF SUGGESTING A HIGHER POTENTIAL FOR
UNSETTLED CONDITIONS.

&&

.AVIATION...COAST...VFR AREAWIDE...WITH ISOLATED MVFR IN FOG
POSSIBLE LATE TONIGHT THROUGH EARLY FRIDAY MORNING NORTH OF CAPE
BLANCO. INLAND...VFR EXCEPT AREA OF MVFR CIGS AND VSBY OVER THE
VALLEYS OF JACKSON...JOSEPHINE...AND DOUGLAS COUNTIES INCLUDING
THE ROGUE...ILLINOIS AND UMPQUA VALLEYS. PARTIAL CLEARING WILL
CONTINUE FOR THESE VALLEYS THIS AFTERNOON THEN EXPECT VALLEY FOG
TO REDEVELOP OVER INLAND VALLEYS WEST OF THE CASCADES TONIGHT
PERSISTING THROUGH FRIDAY MORNING.


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...AIR STAGNATION ADVISORY UNTIL 8 AM PST SUNDAY FOR ORZ024-ORZ026-
ORZ029.

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS
UNTIL 10 PM PST THIS EVENING FOR PZZ350-PZZ356-PZZ370.
SMALL CRAFT ADVISORY FOR WINDS UNTIL 10 PM PST THIS EVENING FOR
PZZ356-PZZ370.
SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 AM PST FRIDAY FOR PZZ376.
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 AM PST FRIDAY
FOR PZZ376.

$$

CC



Back to Main Forecast Discussion Page