Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 232215
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
315 PM PDT TUE SEP 23 2014

.DISCUSSION...AN ATMOSPHERIC RIVER...OR A LONG STRETCH OF DEEP AND
CONCENTRATED MOISTURE...IS AIMED AT THE NORTHERN CALIFORNIA AND
SOUTHERN OREGON COAST. THIS FEATURE COULD BRING SIGNIFICANT
IMPACTS TO THE FORECAST AREA ON WEDNESDAY. THESE IMPACTS INCLUDE
THE POTENTIAL FOR LIFE- AND PROPERTY-THREATENING FLASH FLOODING
AND DEBRIS FLOWS IN AND AROUND WILDFIRE BURN SCARS...AND TRAVEL
PROBLEMS FOR MOST OF THE FORECAST AREA WHEN OILS ON THE ROAD FROM
MONTHS OF MOSTLY DRY WEATHER MIX WITH WATER AND MAKE FOR VERY
SLIPPERY ROADS.

CURRENT SATELLITE-DERIVED PRECIPITABLE WATER IMAGERY SHOWS A PLUME
OF MOISTURE...WITH VALUES OF 1.6 INCHES...NEARING THE COASTLINE.
THIS REPRESENTS A MOISTURE FEED THAT ONLY OCCURS EVERY 5-10 YEARS OR
MORE DURING THE LATE SEPTEMBER TIMEFRAME. THIS WET FRONTAL SYSTEM
WILL BRING SIGNIFICANT RAINS TO THE COAST BY TONIGHT...AND AS THE
WINDS TURN TOWARD A MORE WESTERLY DIRECTION TONIGHT...LIFT OVER THE
MOUNTAINS OF CURRY COUNTY WILL BE ENHANCED AND AREAS LIKE RED MOUND
WILL LIKELY SEE RAINFALL RATES OF 1 INCH PER HOUR EARLY WEDNESDAY
MORNING. RIVERS WILL RISE SHARPLY WITH SUCH HEAVY RAIN.
HOWEVER...NO MAIN STEM RIVER FLOODING IS EXPECTED WITH THIS SYSTEM
BECAUSE OF THIS BEING THE FIRST WET SYSTEM OF THE FALL AND
ANTECEDENT RIVER LEVELS ARE VERY LOW.

THE FRONT AND ASSOCIATED HEAVY RAIN WILL REACH WILDFIRE BURN SCAR
AREAS IN SISKIYOU COUNTY WEDNESDAY MORNING AND CONTINUE THROUGH THE
AFTERNOON. MODELS ARE IN GOOD AGREEMENT ON THESE AREAS OF WESTERN
SISKIYOU COUNTY RECEIVING 1 TO 2 INCHES OF RAIN...WITH THE HEAVIEST
RAIN COMING WEDNESDAY MORNING INTO EARLY AFTERNOON.  A FLASH FLOOD
WATCH AT FFAMFR HAS BEEN ISSUED FOR THESE BURN SCARS...AND RESIDENTS
AND TRAVELERS IN THIS AREA SHOULD BE AWARE OF THE POTENTIAL FOR
FLASH FLOODING...MUDSLIDES...AND ROCKSLIDES. SOME OF THE ROADS IN
AND AROUND THE BURN SCARS INCLUDE HIGHWAY 96...SAWYERS BAR
ROAD...AND SCOTT RIVER ROAD.

ELSEWHERE...WETTING RAINS ARE LIKELY IN ALL LOCATIONS ALONG AND WEST
OF THE CASCADES...WITH ONE HALF INCH EXPECTED IN THE ROGUE
VALLEY...MORE THAN AN INCH IN THE CASCADES. LESSER RAIN AMOUNTS ARE
EXPECTED EAST OF THE CASCADES...WITH AROUND A QUARTER INCH IN
KLAMATH FALLS. GIVEN THAT THIS IS THE FIRST WIDESPREAD RAIN SINCE
LAST SPRING...THERE WILL BE TRAVEL CHALLENGES FOR DRIVERS ON
WEDNESDAY BECAUSE OF SLIPPERY ROADS. OILS BUILD UP OVER TIME AND
WILL BE RELEASED ONTO THE SURFACE TOMORROW AS RAIN HITS THE
ROADS...AND DRIVERS SHOULD ALLOW FOR MORE TIME TO GET TO THEIR
DESTINATION.

THIS SYSTEM IS ALSO BRINGING SIGNIFICANT SOUTH TO SOUTHWEST WINDS TO
THE REGION...AND THESE WINDS WILL CONTINUE THROUGH TOMORROW EAST OF
THE CASCADES. A RED FLAG WARNING AT RFWMFR HAS BEEN ISSUED FOR THESE
WINDS.

RAIN CHANCES WILL DIMINISH SIGNIFICANTLY ON THURSDAY BUT RAIN
CHANCES DO LINGER THROUGH SATURDAY AS UPPER TROUGHING IS SLOW TO
EXIT THE AREA. THE GFS SUGGESTS DRY WEATHER SUNDAY INTO EARLY NEXT
WEEK WHILE THE ECMWF BRINGS IN ANOTHER TROUGH AND RAIN BY SUNDAY
NIGHT INTO MONDAY. WE HAVE CHOSEN A COMPROMISE AND HAVE KEPT SLIGHT
CHANCE POPS FOR MOST OF THE AREA...FOCUSED FROM THE CASCADES
WEST...WITH THE MOST LIKELY AREAS TO SEE RAIN BEING THE UMPQUA BASIN
AND COAST.



&&

.AVIATION...WIDESPREAD MVFR WITH LOCAL IFR WILL PERSIST ALONG THE
COAST THE REST OF THIS AFTERNOON THROUGH WEDNESDAY MORNING. RAIN
WILL GRADUALLY INCREASE THROUGH THIS EVENING, THEN A PERIOD OF
HEAVY RAINFALL IS EXPECTED TO MOVE ONSHORE LATER TONIGHT INTO
WEDNESDAY MORNING WITH A STRONG COLD FRONT. A PERIOD OF GUSTY
WINDS WILL ALSO LIKELY ACCOMPANY THE FRONTAL PASSAGE. TERRAIN
OBSCURATIONS WILL BE TOTAL. THE HEAVY RAINFALL WILL MOVE INLAND TO
THE CASCADES BY MIDDAY WEDNESDAY...THEN SPREAD TO THE EAST SIDE
WEDNESDAY AFTERNOON AND NIGHT. MVFR WILL OVERSPREAD MOST OF THE
WEST SIDE BY AFTERNOON WITH TERRAIN BECOMING FULLY OBSCURED. VFR
WILL PREVAIL EAST OF THE CASCADES THE REST OF TODAY THROUGH
WEDNESDAY MORNING, BUT IT WILL BE WINDY AT TIMES LEADING TO THE
POSSIBILITY OF LOW LEVEL TURBULENCE AND ISOLATED LOW LEVEL WIND
SHEAR. PRECIPITATION WITH MVFR CIGS WILL OVERSPREAD THE EAST SIDE
WEDNESDAY AFTERNOON AND NIGHT. SPILDE


&&

.MARINE...UPDATED 300 PM PDT TUE 23 SEP 2014...SOUTH WINDS WILL
CONTINUE TO INCREASE THROUGH EARLY EVENING AHEAD OF A COLD
FRONT...WHICH WILL BRING PERIODS OF RAIN...STRONG WINDS...AND
HEAVY SEAS TO THE COASTAL WATERS. GALES AND VERY STEEP AND
HAZARDOUS SEAS ARE EXPECTED OVER MUCH OF THE COASTAL WATERS
THROUGH EARLY WEDNESDAY MORNING. WINDS WILL DIMINISH AND STEEP TO
VERY STEEP WIND DRIVEN SEAS WILL SUBSIDE LATE TONIGHT...BUT HEAVY
WEST SWELL WILL BUILD ON WEDNESDAY KEEPING SEAS STEEP INTO
THURSDAY NIGHT. UNSETTLED WEATHER IS LIKELY THROUGH THE END OF THE
WEEK. BTL/WRIGHT


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...RED FLAG WARNING UNTIL 11 PM PDT WEDNESDAY FOR ORZ624-625.

CA...RED FLAG WARNING UNTIL 11 PM PDT WEDNESDAY FOR CAZ285.
     RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR CAZ281-284.
     FLASH FLOOD WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY
     NIGHT FOR CAZ080-081-083.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 AM PDT WEDNESDAY FOR
     PZZ350-356.
     HAZARDOUS SEAS WARNING UNTIL 5 AM PDT WEDNESDAY FOR
     PZZ350-356-370-376.
     GALE WARNING UNTIL 2 AM PDT WEDNESDAY FOR PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT THURSDAY
     FOR PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM PDT THURSDAY FOR
     PZZ370-376.

$$

NSK/NSK/MAS






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