Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 290618 AAA
AFDMFR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MEDFORD OR
1015 PM PST FRI NOV 28 2014

UPDATED AVIATION SECTION.

.DISCUSSION...THE COLD FRONT WAS MOVING THROUGH NW DOUGLAS COUNTY
ALONG THE LINE DOWN TO CAPE BLANCO AS OFF 8 PM THIS EVENING. THE
FRONT PRODUCED HEFTY AMOUNT OF RAIN IN COOS BAY WITH ONE SPOTTER
REPORTING JUST OVER 2 INCHES OF RAIN IN THE LAST 24 HOURS. THE
FRONT IS EXPECTED TO CROSS THE UMPQUA DIVIDE AROUND MIDNIGHT WITH
RAIN SPREADING INTO THE ROGUE VALLEY IN THE SECOND HALF OF
TONIGHT. SNOW LEVEL SOUTH OF THE UMPQUA DIVIDE WILL BE 5500-6000
FEET. BY EARLY SATURDAY MORNING SNOW LEVEL IS EXPECTED TO LOWER TO
AROUND 4000 FEET ACROSS THE CASCADES AND THIS WILL HAVE SOME
IMPACT ON HWY 140. SNOW LEVEL ACROSS THE SISKIYOU SUMMIT IS
EXPECTED TO BE AROUND 5000 FEET BUT BY MID MORNING MOST
PRECIPITATION WILL BE SOUTH OF THE PASS IN SOUTHERN HALF OF
SISKIYOU COUNTY. WITH MORNING TEMPERATURES FORECAST TO BE IN THE
LOWER TO MID 30S ANY SNOWFALL OVER THE SISKIYOU PASS IS NOT
EXPECTED TO ACCUMULATE. HOWEVER TRAFFIC ACROSS THE CASCADES FROM
HIGHWAY 140 NORTHWARD COULD BE IMPACTED ESPECIALLY NEAR CRATER
LAKE WHERE 4 TO 6 INCHES OF SNOW IS EXPECTED.

ELSEWHERE WINDS A 50KT WIND AT 700MB WILL CONTINUE TO IMPACT THE
SECTION OF HWY 31 BETWEEN SUMMER LAKE AND PAISLEY AND I HAVE
EXTENDED THE WIND ADVISORY OVERNIGHT. /FB

&&

.AVIATION...BASED ON THE 29/06Z TAF CYCLE...A COLD FRONT WILL PUSH
INTO THE UMPQUA DIVIDE AROUND MIDNIGHT. IFR CIGS AT KOTH WILL
GRADUALLY IMPROVE TO MVFR AFTER MIDNIGHT WITH VFR BY DAYBREAK.
BREEZY NORTH TO NORTHWEST WINDS ARE EXPECTED AT THE COAST BY EARLY
AFTERNOON.

AS THE FRONT MOVES SOUTH BANDS OF MODERATE SHOWERS WILL ACCOMPANY
THE FRONT AND WIDESPREAD MVFR CIGS/VIS WILL CONTINUE IN THE UMPQUA
VALLEY WITH MOUNTAINS OBSCURED. AHEAD OF FRONT IN THE ROGUE VALLEY
LOCAL MVFR WILL OCCUR. EXPECT THE FRONT TO BRING RAIN AND WIDESPREAD
MVFR CIGS/VIS TO THE ROGUE VALLEY. KMFR COULD SEE OCCASIONAL LAPSE
DOWN TO IFR CIGS AT TIMES IN PERIODS OF MODERATE SHOWERS. EXPECT THE
FRONT TO PUSH SOUTH OF THE SISKIYOU MOUNTAINS AROUND NOON WITH
CONDITIONS IMPROVING TO VFR.
EAST OF THE CASCADES...THE FRONT IS EXPECTED TO SPREAD RAIN AND MVFR
CIGS TO KLMT CLOSER TO 4 AM PST. MVFR CIGS WILL BE INTERMITTENT AND
DEPENDENT MAINLY ON MODERATE SHOWERS. BY EARLY AFTERNOON THE FRONT
WILL HAVE PUSHED INTO SOUTHERN SISKIYOU COUNTY WITH CLEARING ACROSS
SOUTHERN OREGON. HOWEVER THE SOUTHERN END OF THE CASCADES IN THE
MOUNT SHASTA AREA WILL BE OBSCURED WITH MVFR CIGS/VIS FROM LATE
SATURDAY MORNING THROUGH MOST OF THE DAY. /FB

&&

.MARINE...UPDATED 300 PM PST FRI NOV 28 2014...ISOLATED
THUNDERSTORMS ARE EXPECTED THROUGH EARLY THIS EVENING. SOUTH WINDS
AND WIND WAVES HAVE PEAKED AND WINDS WILL DIMINISH SOME TONIGHT.
THOUGH SEAS WILL DROP A BIT THIS EVENING...SMALL CRAFT CONDITIONS
FOR SEAS WILL CONTINUE FOR THE WATERS BEYOND 10 NM FROM SHORE
THROUGH THE WEEKEND...WHILE A COUPLE COLD FRONTS WILL MOVE THROUGH
FROM NORTH TO SOUTH...MAINTAINING LIGHT TO MODERATE NORTH TO
NORTHEAST WINDS THROUGH THE WEEKEND.

A LOW PRESSURE SYSTEM WILL APPROACH FROM THE SOUTHWEST SUNDAY INTO
EARLY NEXT WEEK...AND THERE IS SOME UNCERTAINTY REGARDING HOW STRONG
THE SOUTH WINDS GET ASSOCIATED WITH THE LOW. THE CURRENT FORECAST
REFLECTS THE THINKING THAT GENERALLY LIGHT SOUTH TO SOUTHEAST WINDS
WILL OCCUR MONDAY WITH THE LOW REMAINING WELL OFFSHORE.

&&

.PREV DISCUSSION... /ISSUED 300 PM PST FRI NOV 28 2014/

DISCUSSION...SHORT TERM. MODELS ARE COMING MORE IN LINE THAN
YESTERDAY WITH THE GFS AND THE ECMWF SHOWING CLOSE SOLUTIONS
THROUGH TUESDAY MORNING. THE HEAVIER BAND OF RAIN HAS MADE ITS WAY
INTO MODOC COUNTY WITH THE AXIS OF THE +100 KT JET. ANOTHER
STRONGER JET IS BEHIND THIS AND IS BRINGING ANOTHER ROUND OF
SHOWERS INTO THE WET SIDE AT THIS TIME. THESE SHOWERS WILL
CONTINUE AS THE JET AXIS SLOWLY MIGRATES THROUGH THE REGION
OVERNIGHT. IN THE SOUTHERLY WARM CONVEYOR FLOW SNOW LEVELS REMAIN
HIGH AND ABOVE PASS LEVELS...BUT WITH STRONGER SHOWERS SNOW LEVELS
MAY DROP BRIEFLY TO THE HIGHER PASS LEVELS. HOWEVER...WITH THE
GENERALLY WARM ROAD TEMPS...ANY SNOW THAT FALLS SHOULD MELT
RELATIVELY QUICKLY. A COOLER AIR MASS MOVES IN BEHIND THE FRONT AND
LIGHT SNOW AMOUNTS ARE POSSIBLE ON THE LOWER PASSES TOMORROW
MORNING. THE UPPER LOW WILL BE WELL OFFSHORE WITH CONVERGENCE
SETTING UP ALONG STATIONARY FRONT THAT SITS ROUGHLY ALONG THE CA/OR
STATE LINE THROUGH SUNDAY. THE UPPER LOW THEN MAKES ITS WAY BACK
INTO THE REGION BEFORE OPENING...BRINGING THE PRECIP BACK NORTH AS
THE FRONT IS NUDGED BACK NORTHWARD MONDAY INTO TUESDAY.

LONG TERM...TUESDAY THROUGH FRIDAY. A CLOSED UPPER LOW IS FORECAST
TO WEAKEN AS IT APPROACHES THE CENTRAL CALIFORNIA COAST ON TUESDAY.
THE UPPER LOW WILL WEAKEN AND BECOME AN OPEN WAVE AS IT HEADS
NORTHEAST INTO NORTHERN CALIFORNIA TUESDAY NIGHT INTO WEDNESDAY.

THE GFS AND ECMWF SOLUTIONS DIVERGE BEHIND THIS SYSTEM LATE
WEDNESDAY THROUGH FRIDAY BUT NEITHER MODEL SHOWS A SIGNIFICANT STORM
THURSDAY AND FRIDAY. THE GFS SHOWS A COUPLE OF WEAK UPPER TROUGHS
PASSING THROUGH THE REGION WHILE THE ECMWF SHOWS A RIDGE BUILDING
WITH A STRONGER UPPER TROUGH WELL OFFSHORE.

HEAVIER PRECIPITATION WOULD BE FOCUSED MORE ACROSS NORTHERN
CALIFORNIA TUESDAY INTO WEDNESDAY WITH THE APPROACH OF THE LOW. SNOW
LEVELS WOULD LIKELY BE ABOVE I-5 PASS LEVELS DURING THE HEAVIEST
PRECIPITATION. THEN THE PATTERN MAY BE A MOIST ONSHORE FLOW WITH A
LOT OF CLOUD COVER AND LIGHT PRECIPITATION AT TIMES. TEMPERATURES
WILL PROBABLY BE ABOVE NORMAL FOR EARLY DECEMBER. /SANDLER

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...WIND ADVISORY UNTIL 3 AM PST SATURDAY FOR ORZ030-031-624-625.

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 AM PST SATURDAY
     FOR PZZ350-356.
     SMALL CRAFT ADVISORY FOR WINDS FROM 7 PM SATURDAY TO 10 AM PST
     SUNDAY FOR PZZ370.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 PM PST SUNDAY
     FOR PZZ370-376.
     SMALL CRAFT ADVISORY FOR WINDS FROM 1 PM SATURDAY TO 10 AM PST
     SUNDAY FOR PZZ376.

$$

FJB/RES/NSK


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