FXUS66 KMFR 200941
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
241 AM PDT SAT SEP 20 2008
.DISCUSSION...CURRENT WATER VAPOR IMAGE SHOWS THE UPPER LEVEL LOW
CENTERED NEAR SISKIYOU COUNTY WITH MOST OF THE CONVECTION HAVING
SHIFTED NORTH AND EAST OF THE CWA. THE UPPER LEVEL LOW WILL
CONTINUE TO MOVE NORTHEAST THIS MORNING AND EXIT THE CWA THIS
AFTERNOON. ANY SHOWERS EARLY THIS MORNING WILL BE IN NORTHEAST
LAKE COUNTY AND ENDING BEFORE 11 AM. ELSEWHERE...CONDITIONS WILL
BE DRY WITH MORNING CLOUDS FOLLOWED BY AFTERNOON CLEARING WITH 
COOLER TEMPERATURES. A WEAK SURFACE HIGH WILL BUILD INTO THE
REGION TONIGHT WHICH WILL LEAD TO DECREASING CLOUD COVER EAST OF
THE CASCADES. IF THERE IS ENOUGH CLEARING...THEN THERE IS THE
POTENTIAL FOR MINS TO DROP TO NEAR OR BELOW FREEZING WHICH MAY
NECESSITATE A FROST ADVISORY FOR OVERNIGHT TONIGHT INTO SUNDAY
MORNING.
THE GFS...ECMWF AND NAM SHOW A WEAK SHORTWAVE APPROACHING THE
OREGON COAST SUNDAY AFTERNOON AND NIGHT. THE NAM IS WEAKER WITH
THIS FEATURE COMPARED TO THE GFS AND ECMWF AND TRACKS IT FURTHER
SOUTH. FOR NOW HAVE KEPT A SLIGHT CHANCE OF RAIN OVER NORTHERN
COOS AND NORTHWEST DOUGLAS COUNTIES SUNDAY AFTERNOON...WITH THE
POTENTIAL FOR SHOWERS SHIFTING SOUTH AND EAST...BUT REMAINING
MAINLY NORTH OF THE UMPQUA DIVIDE...ALONG THE COAST AND NORTHERN
CASCADES.
WEAK RIDGING WILL MOVE INTO THE AREA SUNDAY NIGHT WITH SKIES
CLEARING OUT. THIS ALONG WITH LONGER NIGHTS WILL LEAD TO
TEMPERATURES DROPPING BELOW FREEZING EAST OF THE CASCADES. THIS
WOULD BE A STRONGER ARGUMENT FOR A FROST ADVISORY OR FREEZE
WARNING...BUT THERE IS STILL TIME TO ASSESS THIS. 
5H HEIGHTS RISE MONDAY THROUGH TUESDAY WITH A WESTERLY FLOW. THIS
WILL KEEP CONDITIONS DRY WITH MILDER TEMPERATURES IN THE AFTERNOON
AND COOL AT NIGHT. THE GFS AND ECMWF SHOW ANOTHER FRONT
APPROACHING THE CWA WEDNESDAY BRINGING RAIN TO THE COAST FOLLOWED
BY POST FRONTAL SHOWERS WEDNESDAY AFTERNOON ALONG AND WEST OF THE
CASCADES. 
MODELS DIFFERENCES EXIST THURSDAY AND BEYOND. MOST NOTABLY...THE
ECMWF SUGGEST AN UPPER LEVEL LOW WILL DIG DOWN INTO NORTHWEST
OREGON AND BRING ANOTHER ROUND OF POTENTIAL RAIN BY NEXT SATURDAY.
ON THE OTHER HAND...THE GFS SHOWS A WEAK RIDGE. THE ENSEMBLE MEAN
DOES HINT AT A WEAK TROUGH MOVING THROUGH SATURDAY. FOR NOW HAVE
MADE LITTLE CHANGE TO THE EXTENDED BEYOND WEDNESDAY DUE TO MODEL
INCONSISTENCIES.
&&
.AVIATION...LIFR CONDITIONS WILL CONTINUE NEAR KOTH UNTIL 8 AM
WITH CIGS BELOW 1000 FEET. VISIBILITY WILL BE BELOW 4 MILES...BUT
WILL OCCASIONALLY FALL BELOW 1 MILE THROUGH EARLY THIS MORNING.
CONDITIONS WILL IMPROVE TO VFR WITH LOCAL MVFR CONDITIONS BY MID
MORNING INTO THE AFTERNOON. CIGS WILL COME UP TO AROUND 4000 FEET
BY MID MORNING AND AFTERNOON. OVC TO BKN SKY COVER IS EXPECTED
ALONG AND NORTH OF THE UMPQUA DIVIDE UP TO KRBG WITH CIGS ABOVE
6000 FEET...THEN WILL BREAK UP WITH SCT CONDITIONS IN THE
AFTERNOON. VFR CONDITIONS ARE EXPECTED NEAR KMFR AND KLMT TODAY.
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
CA...NONE.
PACIFIC COASTAL WATERS...NONE.
$$
PETRUCELLI