FXUS66 KMFR 030434
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
834 PM PST WED DEC 2 2009
.DISCUSSION...NO CHANGES ARE NECESSARY THIS EVENING. SEE
PREVIOUS DISCUSSION. MTS
&&
.AVIATION...IFR/LIFR CIGS WILL CONTINUE AT KRBG AND KMFR AND THE
REMAINDER OF THE WEST SIDE VALLEYS TONIGHT. LIFR VISIBILITY WILL
CONTINUE KMFR...THOUGH FOG SEEDING EFFORTS ARE EXPECTED. THE LOW
CIGS AND VIS WILL CONTINUE THROUGH TOMORROW, PERHAPS WITH MINOR
IMPROVEMENTS TOMORROW AFTERNOON. PATCHY IFR CIGS WILL DEVELOP OVER
THE EAST SIDE TONIGHT, BUT WILL BE MAINLY FROM KLMT NORTHWARD. VFR
CONDITIONS ARE EXPECTED ELSEWHERE, INCLUDING AT KOTH.
&&
.PREV DISCUSSION... /ISSUED 304 PM PST WED DEC 2 2009/
SYNOPSIS...HIGH PRESSURE ALOFT WILL CONTINUE TO BUILD JUST OFF THE
OREGON COAST TONIGHT, THEN SHIFT INLAND TOMORROW. A NORTHERN BRANCH
JET STREAM DISTURBANCE WILL DIG SOUTHWARD INTO THE PACIFIC NORTHWEST
FRIDAY THEN DEVELOP A CLOSED LOW OVER EASTERN OREGON/IDAHO FRIDAY
NIGHT INTO THIS WEEKEND. AT THE SAME TIME, STRONG RIDGING WILL OCCUR
OVER THE NORTH PACIFIC/ALASKA. ANOTHER DISTURBANCE ROTATING AROUND
THE CLOSED LOW OVER OR/ID WILL DROP SOUTHWARD SUNDAY PROBABLY JUST
OFFSHORE. ON SUNDAY NIGHT AND MONDAY, MOISTURE FROM A SYSTEM IN THE
SOUTHERN BRANCH OF THE JET MAY GET DRAWN FAR ENOUGH NORTH TO PRODUCE
MORE SIGNIFICANT PRECIPITATION...ESPECIALLY OVER NORTHERN CALIFORNIA
WITH THE POTENTIAL FOR LOW ELEVATION SNOW. BEYOND THAT, THE REST OF
NEXT WEEK LOOKS UNSETTLED WITH SEVERAL STORM SYSTEMS AFFECTING THE
WEST COAST.
SHORT TERM...LOW CLOUDS AND FOG HELD STRONG AGAIN TODAY OVER THE
WEST SIDE VALLEYS PREVENTING TEMPERATURES FROM GETTING OUT OF THE
30S IN MANY AREAS, INCLUDING MEDFORD. ON THE FRINGES ON THE FOG AND
AT ELEVATIONS ABOVE 2000 FEET MSL, TEMPERATURES ROSE INTO THE UPPER
40S AND 50S. LOW CLOUDS WERE ALSO A FACTOR FOR AWHILE TODAY OVER THE
EAST SIDE, BUT SOME DRYING HAS OCCURRED AND MOST OF THE CLOUDS HAVE
SCOURED OUT RESULTING IN A SUNNY AFTERNOON. HIGH PRESSURE BUILDING
JUST OFFSHORE WILL MAINTAIN THE STAGNANT WEATHER PATTERN ACROSS THE
CWA THROUGH MOST OF FRIDAY, SO EXPECT MORE CLOUDS AND FOG FOR THE
WEST SIDE VALLEYS, WITH NICER CONDITIONS OVER THE HIGHER ELEVATIONS
AND IN NORTHERN CALIFORNIA. EAST SIDE AREAS MAY HAVE A FEW LOW
CLOUDS REDEVELOP TONIGHT, BUT THEY SHOULD BURN OFF TOMORROW MORNING.
BY FRIDAY NIGHT, THE PATTERN BEGINS TO CHANGE. A POTENT DISTURBANCE
WILL DROP SOUTHWARD FROM WESTERN CANADA INTO THE PACIFIC NORTHWEST.
THE LEADING EDGE OF THE COLDER AIR ASSOCIATED WITH THIS SYSTEM WILL
REACH THE CWA BY SATURDAY MORNING. WHILE THIS SYSTEM DOES NOT HAVE
MUCH MOISTURE WITH IT, IT MAY PRODUCE A FEW SNOW SHOWERS OVER THE
HIGHER ELEVATIONS SATURDAY. SINCE THE WEST SIDE VALLEYS HAVE BEEN
MIRED IN THE FOG AND LOW CLOUDS THE LAST FEW DAYS, THE COLDER
AIR MASS ARRIVING THIS WEEKEND WILL BE MOST NOTICEABLE OVER THE
HIGHER TERRAIN, THE EAST SIDE AND ALONG THE COAST. DAYTIME
TEMPERATURES THERE THIS WEEKEND WILL LIKELY BE 10-20 DEGREES LOWER
THAN THEY HAVE BEEN. BY SUNDAY, MOST OF THE CWA WILL BE IN A COLD,
DRY NORTHERLY FLOW. BUT, BY SUNDAY NIGHT, MORE CHANGES ARE ON THE
WAY. SPILDE
LONG TERM...ALL OF THE MODELS POINT TO AN INCREASE IN MOISTURE
ACROSS THE AREA SUNDAY NIGHT. THE ECMWF AND CANADIAN SUGGEST THERE
IS CONCERN FOR LOW ELEVATION SNOW TO DEVELOP LATE SUNDAY NIGHT AND
LASTING INTO MONDAY MORNING. THIS CONCERN IS DUE IN PART TO A DRY
AND COLD AIR MASS THAT WILL BE IN PLACE OVER THE WEEKEND ALONG WITH
INCREASING AND OVERRUNNING MOISTURE PROJECTED TO MOVE IN FROM THE
SOUTHWEST. THE ECMWF AND CANADIAN SHOW A SHORTWAVE THAT DROPS IN
FROM THE NORTH AND EVOLVES INTO AN UPPER LOW OVER THE WATERS
SUNDAY. THIS WILL PINCH OFF THE UPPER LEVEL RIDGE AND ALLOW
MOISTURE TO INCREASE FROM THE WEST. AT THE SAME TIME A SURFACE LOW
IS EXPECTED TO DEVELOP AND MOVE TOWARDS SOUTHWEST OREGON SUNDAY
NIGHT. RIGHT NOW...IT LOOKS LIKE THE WINDOW OF OPPORTUNITY FOR LOW
ELEVATION SNOW FOR SOUTHWEST OREGON AND NORTHWEST CALIFORNIA WILL
BE OVERNIGHT SUNDAY INTO MONDAY MORNING. EVEN THE ROGUE VALLEY
COULD BE FLIRTING WITH A RAIN WET SNOW MIX. THIS WILL HAVE TO BE
LOOKED AT MORE CLOSELY IN THE DAYS TO COME BEING THAT THIS EVENT
IS STILL 4-5 DAYS OUT. THE ONE THING TO NOTE IS THAT THE GFS
APPEARS TO BE THE OUTLIERS SUGGESTING A DRY AND COLDER SOLUTION
THROUGH EARLY NEXT WEEK.
AFTER MONDAY...A PROGRESSIVE PATTERN IS IN THE WORKS FOR MOST OF
NEXT WEEK WITH A MOIST WEST TO SOUTHWEST FLOW OVER THE CWA. MOST OF
THE PRECIPITATION WILL BE CENTERED ALONG AND WEST OF THE CASCADES
WITH THE MOST SIGNIFICANT QPF OVER NORTHERN CALIFORNIA AND SOUTHWEST
OREGON. AT THIS TIME...THE HEAVIEST PRECIPITATION WILL BE DIRECTED
IN CENTRAL CALIFORNIA AND SIERRAS. PETRUCELLI
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...AIR STAGNATION ADVISORY UNTIL NOON PST FRIDAY FOR ORZ024-ORZ026-
ORZ029-ORZ030-ORZ031.
CA...NONE.
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM
10 AM THURSDAY TO 10 PM PST FRIDAY FOR PZZ350-PZZ356-PZZ370-
PZZ376.
$$
