FXUS66 KMFR 301053 CCA
AFDMFR

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE MEDFORD OR
251 AM PST MON NOV 30 2009

.SYNOPSIS...PERSISTENT WEATHER PATTERN WILL CONTINUE THROUGH
FRIDAY WITH FOG IN THE WESTERN VALLEYS AND BRIEF PERIODS OF SUN IN
THE AFTERNOON...WITH NEAR-AVERAGE TEMPERATURES. THIS PATTERN CHANGES
TOWARDS THE WEEKEND AND A CHALLENGING FORECAST INVOLVES HOW
MOISTURE AND TEMPERATURE CHANGES WILL ACTUALLY PLAY OUT GIVEN A
MYRIAD OF FACTORS.

&&

.DISCUSSION...FOG IS SPREADING THROUGH PARTS OF THE I-5 CORRIDOR
FROM GRANTS PASS TO NORTH MEDFORD. WILL MONITOR PROGRESSION AND
COVERAGE OF FOG FOR POSSIBLE DENSE FOG ADVISORY. FOG WILL LIFT TO
LOW CLOUDS AND EVENTUALLY CLEARING SHOULD OCCUR AROUND 2PM IN
MEDFORD WHILE ROSEBURG CLOUDS MAY ONLY CLEAR BRIEFLY IN THE
AFTERNOON BEFORE FILLING BACK IN TONIGHT. THIS STABLE PATTERN WITH
COLD MORNINGS IN THE VALLEYS AND WARMER...SUNNY CONDITIONS IN THE
HIGHER ELEVATIONS...WILL CONTINUE THROUGH FRIDAY. AIR STAGNATION
ADVISORY MAY BE NEEDED TODAY AS LOW INVERSION AND LIGHT WINDS IN
THE WESTERN VALLEYS REMAIN THROUGH THURSDAY.

BY SATURDAY THINGS GET QUITE INTERESTING AS PERSISTENT UPPER RIDGE AND
ASSOCIATED SURFACE WEATHER PATTERN WILL LIKELY BEGIN TO CHANGE. IT
APPEARS THAT THE PIECES ARE COMING TOGETHER FOR A FORECAST OF
OPPORTUNITY. REVIEW OF AN IDEALIZED VIEW OF THE TRANSITION FROM A
STAGNANT TO AN ACTIVE PATTERN ALONG THE CENTRAL WEST COAST DUE TO
EFFECTS OF A MADDEN JULIAN OSCILLATION CROSSING THE INTERNATIONAL
DATELINE INDICATES THAT WE ARE LIKELY 7 TO 10 DAYS FROM A MAJOR
PATTERN TRANSITION. THE MADDEN JULIAN OSCILLATION CONVECTIVE
SIGNAL APPEARS TO BE CENTERED ON OR JUST WEST OF THE INTERNATIONAL
DATELINE. A TROUGH IN THE JET STREAM EXPECTED TO CROSS THE
HIMALAYAS AND THEN EASTERN CHINA EARLY TO MID NEXT WEEK IS WELL
AGREED UPON IN THE GLOBAL MODEL GUIDANCE. WHEN THIS TROUGH REACHES
THE WESTERN PACIFIC IT IS LIKELY THAT THE TROPICAL CONVECTION IN
THE WESTERN PACIFIC WILL INTERACT WITH IT RESULTING IN A
SIGNIFICANT ACCELERATION OF THE JET STREAM ACROSS THE WEST CENTRAL
PACIFIC OCEAN. THIS...TOO...IS NOW AGREED UPON BY THE MODELS. THIS
MAY HELP KICK THE MJO SIGNAL EASTWARD.

MODEL SOLUTIONS IN REGARDS TO WHAT KIND OF WEATHER IMPACTS
SOUTHERN OREGON AND NORTHERN CALIFORNIA THIS WEEKEND DIFFER
SIGNIFICANTLY. THE CANADIAN AND GFS SUGGEST BELOW AVERAGE
TEMPERATURES AND LIGHT PRECIPITATION WHILE THE ECMWF BRINGS
SIGNIFICANT PRECIPITATION TO THE AREA WHILE KEEPING TEMPERATURES
NEAR OR NORMAL FOR THIS TIME OF YEAR. IN THE FORECAST...HAVE
BUMPED UP POPS TO SLIGHT CHANCE WITH TEMPERATURES BELOW CLIMO ON
SUNDAY. THIS REPRESENTS A BALANCE OF PERSISTENCE...AND LEANS
TOWARDS GFS AND CANADIAN REGARDING COOLER TEMPERATURES AND LIGHT
PRECIPITATION. ECMWF SOLUTION...GIVEN IDEALIZED AND DOCUMENTED 
UNDERCUTTING OF RIDGES WITH RESPECT TO MJO SIGNAL ADVANCING
EAST...DOES NOT SEEM AS LIKELY. FUTURE MODEL RUNS AND SATELLITE
INTERPRETATION OVER THE NEXT FEW DAYS WILL LIKELY YIELD MUCH MORE
CONFIDENCE IN ANY UPCOMING PATTERN CHANGE.

&&

.AVIATION...FOG...GRADUALLY LIFTING TO LOW CEILINGS...WILL IMPACT RBG AND MFR
THROUGH LATE MORNING TO EARLY AFTERNOON HOURS. GIVEN EARLIER ONSET
AND LATER CLEARING TIMES OF RECENT DAYS...ONLY SEVERAL HOURS OF
VFR WEATHER MAY EXIST OVER PORTIONS OF THE WESTERN VALLEYS. ON THE
EAST SIDE AND OVER HIGHER TERRAIN...VFR CONDITIONS SHOULD CONTINUE THE
NEXT 24 HOURS. ALONG THE NORTHERN COAST NEAR OTH...SOME AFTERNOON LOW
CEILINGS MAY IMPACT TERMINALS THERE WITH STRATUS FIELD NOTED ON IR
IMAGERY AND WEAKENED OFFSHORE FLOW ALLOWING THESE CLOUDS TO REACH
LAND TOMORROW.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS 
     UNTIL 4 AM PST TUESDAY FOR PZZ350-PZZ356-PZZ370.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 4 AM PST EARLY THIS MORNING 
     FOR PZZ370-PZZ376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 PM PST TUESDAY 
     FOR PZZ376.

$$

KEENE/LUTZ