Area Forecast Discussion
Issued by NWS Medford, OR

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532
FXUS66 KMFR 060024
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
424 PM PST FRI FEB 5 2016

.UPDATED FOR MARINE AND AVIATION...


.PREV DISCUSSION... /ISSUED 243 PM PST FRI FEB 5 2016/

SHORT TERM...THE COLD FRONT IS MOVING INSIDE LONGITUDE 130W THIS
AFTERNOON. THIS FRONT IS EXPECTED TO BRING GUSTY SOUTHWEST WINDS
TO THE HIGHER TERRAIN THIS EVENING. WE ARE CONTINUING THE WIND
ADVISORY FOR PARTS OF KLAMATH/LAKE/MODOC COUNTIES. SHORT TERM
GUIDANCE BRINGS RAIN TO THE COOS COUNTY COAST BETWEEN 4-5 PM THIS
AFTERNOON WITH MODERATE SHOWERS INTO SOUTHERN CURRY COUNTY AROUND
6 PM. EXPECT BETWEEN 020-0.25" OF RAIN AT THE COAST WITH AREAS OF
HALF INCH NEAR CAPE BLANCO AND GOLD BEACH. RAIN IS EXPECTED TO
SPREAD INTO THE UMPQUA BASIN LATER THIS EVENING AND WE EXPECT
AROUND 0.20" IN THE ROSEBURG AREA. RAIN WILL FOLLOW THE FRONTAL
BAND CLOSELY INTO THE ROGUE VALLEY SHORTLY BEFORE MIDNIGHT AND
ALMOST 0.10" IS FORECAST FOR THE MEDFORD AREA. WESTERLY FLOW COULD
WRING OUT MORE PRECIPITATION OVER THE CASCADES BUT OTHERWISE NOT
MUCH PRECIPITATION IS EXPECTED TO CROSS THE CASCADES EXCEPT AROUND
0.05" IN NORTHERN KLAMATH COUNTY.

ON SATURDAY A WARM WILL PASS TO THE WEST OF SOUTHERN OREGON COAST
WITH NO PRECIPITATION INLAND. THE WEATHER PATTERN WILL THEN CHANGE
TO THE STRONG RIDGING FROM SATURDAY NIGHT INTO MOST OF NEXT WEEK.
THIS WILL BE THE FIRST TIME DURING THIS WET SEASON THAT WE SEE
PERSISTENT RIDGING...SOMETHING WE WERE MORE ACCUSTOMED TO SEEING
DURING THE LAST 2 YEARS. THE MAIN EFFECT FROM THIS RIDGING IS VERY
WARM AND DRY AIR ALOFT AND STRONG INVERSION AT NIGHT. IF THIS
PATTERN HAD HAPPENED EARLIER IN THE SEASON LIKE DECEMBER OR
JANUARY..WE WOULD EXPECT FOG AND LOW CLOUDS TO BE MORE PERSISTENT
DURING THE DAY. SINCE WE ARE MOVING INTO FEBRUARY..THE GRADUALLY
HIGHER SUN ANGLE SHOULD HELP BURN OFF THE FOG BY MID MORNING AND
WARM DAYTIME TEMPERATURES CAN BE EXPECTED.

IN SPITE OF THE WARM AFTERNOON TEMPERATURES..WE ARE STILL
CONCERNED WITH MIXING. FORECAST SOUNDINGS AT MEDFORD AND OTHER KEY
STATIONS SHOW VERY WARM LAYER ALOFT THAT WILL LIMIT MIXING TO JUST
2000 FEET OR SO. HOWEVER WE MAY SEE AFTERNOON WINDS WHICH WOULD
INCREASE THE BURNING INDEX A BIT. THE NEXT SHIFT WILL HAVE TO TAKE
A CLOSER LOOK AT WHETHER WE WILL SEE PERSISTENT AIR STAGNATION
DURING THE EARLY PART OF NEXT WEEK.

OFFSHORE FLOW IS EXPECTED ON SATURDAY NIGHT THROUGH SUNDAY NIGHT
WHICH WILL LEAD TO VERY WARM NIGHT AT BOTH BROOKINGS AND NORTH
BEND. THE OFFSHORE WINDS WEAKEN A BIT AFTER SUNDAY NIGHT BUT THE
AIR MASS IS SO WARM AT H850 THAT OVERNIGHT TEMPERATURES AT THE
COAST AND IN THE COASTAL RANGE WILL REMAIN WARM INTO MOST OF NEXT
WEEK.

ANOTHER FORECAST CHALLENGE IS THE VERY COLD OVERNIGHT TEMPERATURES
FOR THE KLAMATH/TULELAKE BASIN AS WELL AS THE GOOSE LAKE BASIN.
BOTH THE GFS AND THE ECMWF ARE FORECASTING LOWS IN THE 15-20 DEG
RANGE FOR THE KLAMATH/TULELAKE AND GOOSE LAKE BASINS WITH THE
POTENTIAL FOR STRATUS LOW CLOUDS THAT COULD LINGER THROUGH EARLY
AFTERNOON. /FB

LONG TERM...WEDNESDAY THROUGH FRIDAY...CONFIDENCE IS HIGH THAT THE
STRONG RIDGE THAT WILL BE OVER US THROUGH EARLY NEXT WEEK WILL BEGIN
TO BREAK DOWN AND THIS WILL ONCE AGAIN OPEN THE DOOR FOR STORM
SYSTEMS TO REACH THE PACIFIC NORTHWEST. AS OFTEN IS THE
CASE...HOWEVER...CONFIDENCE IN THE DETAILS...LIKE TIMING AND
STRENGTH OF THESE SYSTEMS...REMAINS LOW. MODEL DEPICTIONS ARE FAIRLY
CONSISTENT IN SHOWING THE FIRST DISTURBANCE MOVING IN LATE WEDNESDAY
OR WEDNESDAY NIGHT WITH THE ECMWF FASTEST AND STRONGEST. OFTEN THE
FIRST FRONT TO DISPLACE THE RIDGE IS FAIRLY WEAK...OR AT THE VERY
LEAST...ENDS UP WEAKENING AS IT RUNS INTO THE RIDGE. THE
GFS/CANADIAN MODELS SHOW A WEAKER SYSTEM MOVING ONSHORE DURING THIS
TIME FRAME. HAVE GONE WITH A BLEND HERE WITH SLIGHT CHANCE TO CHANCE
POPS MAINLY FROM THE CASCADES WEST WITH SNOW LEVELS MOSTLY ABOVE
8000 FEET. THERE SHOULD BE A BREAK AT SOME POINT THURSDAY AS ANOTHER
STRONGER TROUGH UPSTREAM DEEPENS OFFSHORE. THIS SYSTEM WILL BRING A
BETTER CHANCE FOR PRECIPITATION ACROSS THE AREA THURSDAY NIGHT
THROUGH FRIDAY NIGHT. SNOW LEVELS AROUND 7000 FEET THURSDAY NIGHT
WILL LOWER TO 4000-5000 FEET FRIDAY NIGHT. SPILDE

AVIATION...FOR THE 06/00Z TAF CYCLE... A COLD FRONT WILL BRING
RAIN AND GUSTY WINDS TO THE COAST THIS EVENING. RAIN WILL DEVELOP
BY LATE THIS AFTERNOON ALONG THE COAST, THEN MOVE INLAND TO THE
CASCADES TONIGHT.

EXPECT MVFR CIGS AND WIDESPREAD TERRAIN OBSCURATION. MVFR IS LIKELY
TO CONTINUE IN VALLEYS BEHIND THE FRONT. IFR PROBABLY DEVELOPS IN
FOG AND LOW CLOUDS AT ROSEBURG AND KLAMATH FALLS,  HOWEVER THE
SOUNDINGS AT MEFORD DON`T SUGGEST ENOUGH MOISTURE TO DEVELOP FOG.
STILL THE MOISTURE FROM THE RAIN AND CLEARING SKIES SHOULD ALLOW
IFR RULES FOR THE MAJORITY OF THE VALLEYS SATURDAY MORNING.

-SMITH

MARINE...UPDATED 400 PM PST FRI FEB 6 2016... BUOYS CURRENTLY
SHOWING 16 FEET WITH GALES IN THE OUTER WATERS AHEAD OF THE COLD
FRONT. EVENTUALLY, THIS FRONT WILL MOVE THROUGH THE WATERS AND
GALES WILL SUBSIDE. STILL EXPECTING STEEP SEAS BEHIND THIS FRONT,
SO A SMALL CRAFT FOR HAZARDOUS SEAS WILL CONTINUE INTO SATURDAY AS
THE WINDS DIE DOWN.

PAST SATURDAY,  MODELS ARE SHOWING HIGH PRESSURE BUILDING WITH VERY
WEAK OFFSHORE FLOW.  THE ONLY CONCERN WILL BE STEEP SEAS ENTERING
THE WATERS TUESDAY AND THURSDAY.

-SMITH

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...WIND ADVISORY UNTIL 7 AM PST SATURDAY FOR ORZ030-031.

CA...WIND ADVISORY UNTIL 7 AM PST SATURDAY FOR CAZ085.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 7 PM PST THIS EVENING FOR
     PZZ350-356-376.
     GALE WARNING UNTIL 7 PM PST THIS EVENING FOR PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 PM PST SATURDAY
     FOR PZZ350-356-370-376.

$$

FJB/MAS/CZS



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