FXUS66 KMFR 041158
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
358 AM PST FRI DEC 4 2009

.SHORT TERM...TODAY THROUGH MONDAY...

TODAY:
SHORT TERM CONCERN FOR THIS MORNING IS DENSE FOG CONDITIONS FOR
THE ILLINOIS AND ROGUE VALLEY. THE LOW LEVEL TEMPERATURE INVERSION
HAS STRENGTHENED SINCE 12Z YESTERDAY IN COMPARING YESTERDAYS KMFR 
RAOB WITH THE JUST RELEASED KMFR RAOB THIS MORNING. THIS MAKES
SENSE SINCE THE OFFSHORE RIDGE CONTINUES TO BUILD NORTHWARD OVER
THE NORTHEAST PACIFIC WITH 500 HPA HEIGHTS INCREASING IN THE LAST
24 HOURS AS WELL. AS A RESULT OF THE METEOROLOGICAL VARIABLES
ABOVE...HAVE ISSUED A DENSE FOG ADVISORY FOR THE VALLEYS OF ORZ24
AND ORZ26 UNTIL 17Z THIS MORNING FOR ELEVATIONS BELOW 2000 FEET.
VISIBILITIES ARE EXPECTED TO IMPROVE AOA 1/4 MILE BY MID MORNING
ALTHOUGH TODAY SHOULD REMAIN MOSTLY FOGGY FOR THE VALLEYS FOR A
GOOD PORTION OF THE DAY WITH SOME EROSION OF THE FOG LAYER LATE
THIS AFTERNOON.

SATURDAY:
THERMODYNAMIC PROFILES INDICATE A COOLING OF THE ATMOSPHERIC
COLUMN AS AN UPPER LEVEL TROF DIGS SOUTHWARD ACROSS THE NORTHERN
ROCKIES. THIS SHOULD HELP TO ERODE THE LL TEMPERATURE INVERSION
WITH VENTILATION INDEX VALUES INCREASING VIA INCREASED LL MIXING.
THERE IS JUST A SLIGHT CHANCE OF PRECIPITATION SATURDAY...HOWEVER
EXPECT MOST OF THE MOISTURE TO REMAIN EAST OF THE FA.

SUNDAY AND MONDAY:
CONTINUED COLD AIR ADVECTION IS EXPECTED SUNDAY AND MONDAY AS
ANOTHER VORTMAX ROTATES OVER THE PACIFIC NORTHWEST FROM THE NORTH.
SNOW LEVELS WILL CONTINUE TO DECREASE THROUGH THIS PERIOD...HOWEVER
THE GOOD NEWS IN THAT THE MOISTURE IS STILL EXPECTED TO REMAIN
SOUTH AND EAST OF THE FA SO AM NOT EXPECTING ADVISORY CRITERIA
SNOW AMOUNTS AT THIS TIME.

.LONG TERM...TUESDAY THROUGH NEXT FRIDAY...
NO SIGNIFICANT CHANGES TO THE EXTENDED AS THERE IS STILL A BIT OF
DISAGREEMENT BETWEEN GFS AND ECMWF. BOTH MODELS DO INDICATE
TEMPORARY 500 HPA RIDGING AHEAD OF THE NEXT SYSTEM TUESDAY WITH
THE GFS SLIGHTLY MORE AMPLIFIED. WEDNESDAY ONWARD CONTINUES TO
LOOK WET AS THE 250 HPA SUBTROPICAL JET INTENSIFIES AND MOVES
CLOSER TO THE FA WITH MOST OF THE IMPACTS GEARING TOWARDS THE
STATE OF CALIFORNIA.

&&

.AVIATION...
LIFR CONDITIONS ARE EXPECTED TODAY FOR THE ILLINOIS AND ROGUE
VALLEY AS WELL AS THE UMPQUA BASIN AT LEAST UNTIL 18Z AND PROBABLY
CONTINUING LATER TOWARDS 20-21Z AS A TEMPERATURE INVERSION REMAINS
OVER THE AREA. SLIGHT VISIBILITY IMPROVEMENTS CAN BE EXPECTED LATE
THIS AFTERNOON WITH CONDITIONS QUICKLY DETERIORATING AGAIN BY
05.00Z TONIGHT.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...AIR STAGNATION ADVISORY UNTIL 10 AM PST SATURDAY FOR ORZ024-
     ORZ026-ORZ029-ORZ030-ORZ031.
     DENSE FOG ADVISORY UNTIL 9 AM PST THIS MORNING FOR ORZ024-ORZ026.

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS 
     UNTIL 10 PM PST SATURDAY FOR PZZ350-PZZ356-PZZ370-PZZ376.
     SMALL CRAFT ADVISORY FOR WINDS FROM 7 PM THIS EVENING TO 10 PM 
     PST SATURDAY FOR PZZ370-PZZ376.

$$

SHORT=CC/KS
LONG/FIRE=MO