Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 291744
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
1044 AM PDT SAT AUG 29 2015

.AVIATION...FOR THE 29/18Z TAF CYCLE...ISOLATED SHOWERS MAY BRING
BRIEF MVFR CONDITIONS TODAY, AND OCCASIONAL MOUNTAIN OBSCURATIONS
ARE EXPECTED. OTHERWISE, CONDITIONS WILL BE VFR THROUGH THIS
AFTERNOON. GUSTY SOUTHWEST WINDS WILL CREATE MOUNTAIN WAVE
TURBULENCE AND BUMPY RIDES INTO AREA TERMINALS THROUGH THE
AFTERNOON. A FRONT WILL BRING LIGHT RAIN AND MVFR CONDITIONS TO
THE COAST AND UMPQUA LATE THIS EVENING AND OVERNIGHT. -WRIGHT

&&

.PREV DISCUSSION... /ISSUED 838 AM PDT SAT AUG 29 2015/

UPDATE...THE SURFACE LOW TRACK HAS MOVED ABOUT 100 TO 150 MILES
FURTHER NORTH THAN PREVIOUSLY FORECAST, AND ALTHOUGH WINDS HAVE
NOT QUITE REACHED THE STRENGTH EXPECTED ALONG THE COAST, WINDS
ELSEWHERE ARE RIGHT ON TRACK. PRECIPITATION WAS SLIGHTLY LESS
INLAND, BUT AREAS ALONG THE COAST AND COASTAL RANGES, AS WELL AS
IN THE UMPQUA AND ALONG THE NORTHERN CASCADES, HAVE MET
EXPECTATIONS. REPORTS THIS MORNING HAVE CONFIRMED THAT ALL MAJOR
WILDFIRES IN THE FORECAST AREA HAVE RECEIVED A WETTING RAIN, AND
MUCH OF THE SMOKE HAS FINALLY BEEN SWEPT OUT OF THE REGION. HAVE
MADE ONLY SLIGHT ADJUSTMENTS TO THE FORECAST FOR TODAY, MAINLY TO
BRING THINGS IN LINE WITH CURRENT OBSERVATIONS. OTHERWISE, NO
CHANGES WERE NECESSARY. SEE THE PREVIOUS DISCUSSION BELOW FOR MORE
INFORMATION. -BPN

MARINE...UPDATED 830 AM PDT SATURDAY 29 AUGUST 2015... THE
SURFACE LOW HAS MOVED SLIGHTLY FARTHER NORTH THAN PREVIOUSLY
ANTICIPATED. THUS, WINDS AND SEAS WILL NOT BE AS STRONG AS
FORECAST. HOWEVER, CONDITIONS WILL REMAIN VERY HAZARDOUS, WITH
GALES AND VERY STEEP SEAS CONTINUING THROUGH THE MORNING AND
AFTERNOON. WITH GOOD VERTICAL MOTION INDICATED IN THE HEAVIER
RAIN, SOME ISOLATED STORM FORCE GUSTS ARE STILL POSSIBLE, BUT DUE
TO THE MORE NORTHERLY TRACK, HAVE DROPPED THE STORM WARNING.
SOUTHERLY SEAS WILL REACH WARNING CONDITIONS FOR MOST OF THE AREA
EVEN WITH THE SLIGHTLY WEAKER THAN EXPECTED WINDS, WITH VERY STEEP
WIND DRIVEN SEAS LIKELY PEAKING IN THE 14 TO 17 FOOT RANGE FROM
GOLD BEACH NORTHWARD. SOUTH WINDS AND ELEVATED SEAS WILL BEGIN TO
SUBSIDE THIS AFTERNOON INTO THIS EVENING. SHOWERS AND LIGHTER
WINDS ARE EXPECTED SUNDAY. -BPN/CC

FIRE WEATHER...UPDATED 400 AM PDT SATURDAY 29 AUGUST 2015...A
FRONTAL SYSTEM WILL MOVE INLAND OVER THE AREA THIS MORNING WHILE A
STRONG SURFACE LOW PRESSURE WILL TRACK NORTH OFF THE SOUTHERN OREGON
COAST THIS MORNING. THIS WILL WILL SHIFT NORTH DURING THE AFTERNOON.
THIS LOW WILL BRING STRONG WINDS TO THE COAST, MOUNTAINS, SHASTA
VALLEY AND EAST SIDE TODAY, WITH BREEZY CONDITIONS ELSEWHERE. LIGHT
TO MODERATE RAIN IS EXPECTED THIS MORNING.  WETTING RAIN LIKELY
ALONG THE COAST AND IN THE CASCADES WITH A CHANCE OF WETTING RAIN
FOR INLAND AREAS, MAINLY WEST OF THE CASCADES.

WHILE WE WILL GET RAIN OVER MANY OF OUR ONGOING FIRES, THERE REMAIN
CONCERNS ABOUT THIS STORM WITH RESPECT TO THOSE FIRES AND THE
PERSONNEL MANNING THEM. THERE IS THE POTENTIAL FOR MODERATE TO
LOCALLY HEAVY RAIN OVER ALL FIRE AREAS IN  THE CASCADES AND COASTAL
AREAS. THIS IS EXPECTED TO BE A GENTLE SOAKING RAIN RATHER THAN
CONVECTIVE, HIGH INTENSITY RAIN, SO BURN SCAR FLOODING AND DEBRIS
FLOWS ARE NOT A HUGE CONCERN. BUT IT IS SOMETHING TO THINK ABOUT.
ALSO, SNAGS, BURNED TREES, AND OTHER MATERIAL THAT HAVE BEEN
WEAKENED OVER THE SUMMER HAVE THE POTENTIAL TO COME DOWN FROM WIND,
THE ADDED WEIGHT OF RAINFALL, OR A COMBINATION OF BOTH. FIREFIGHTERS
SHOULD REMAIN VERY AWARE OF THEIR SURROUNDINGS THIS WEEKEND,
ESPECIALLY ON OR AROUND EXISTING FIRES AND BURN SCARS.

CONDITIONS WILL DRY AND WINDS DECREASE BY THIS EVENING. A SECONDARY
FRONT IS THEN EXPECTED TO BRING ADDITIONAL RAIN SHOWERS FROM THE
CASCADES WEST LATE TONIGHT AND SUNDAY.  GENERAL TROUGHINESS WILL
REMAIN OVER THE PACNW THROUGH THE UPCOMING WEEK, SO COOLER AND MORE
HUMID THAN NORMAL WEATHER IS EXPECTED. RAIN WILL BE POSSIBLE AGAIN
MID WEEK AS ANOTHER FRONT MOVES THROUGH. /CC

PREV DISCUSSION... /ISSUED 446 AM PDT SAT AUG 29 2015/

DISCUSSION...UNUSUALLY STRONG WINDS WILL BE THE MAIN IMPACT TODAY AS
A VERY DEEP LOW PRESSURE TROUGH OFFSHORE FROM OREGON MOVES TO THE
WASHINGTON COAST. ITS ASSOCIATED COLD FRONT IS FAST-MOVING, AND HAS
ALREADY MOVED INLAND. WITH SUCH A STRONG FRONT, ITS POSITION IS
READILY APPARENT FROM EITHER THE SATELLITE IMAGERY OR THE NARROW BAND
OF INTENSE RAINFALL. WINDS WILL REACH PEAK STRENGTH THIS MORNING AS
THE FRONT PASSES, BUT THE LOW LEVEL PRESSURE GRADIENT IS EXPECTED
TO PRODUCE STRONG WINDS THROUGH THE AFTERNOON. MOUNTAIN AND EAST
SIDE WIND GUSTS ARE ALREADY AT 25 TO 40 MPH AND WILL LIKELY REACH
35 TO 55 MPH EXCEPT LOCALLY AS HIGH AS 70 MPH AT EAST SIDE RIDGES
AND ALONG HIGHWAY 31 BETWEEN PAISLEY AND SILVER LAKE IN LAKE
COUNTY. WEST SIDE VALLEY WIND GUSTS WILL NOT BE AS STRONG AT 20
TO 30 MPH...EXCEPT TO 40 MPH NEAR WEED, BUT THERE WILL LIKELY BE
DOWNED BRANCHES WITH DROUGHT STRESSED TREES STILL FULL OF LEAVES.

RAINFALL WILL OCCUR MAINLY EARLY THIS MORNING WITH IMPRESSIVE
AMOUNTS IN EXCESS OF HALF AN INCH LIMITED TO CURRY COUNTY, AND
THE WESTERN PORTIONS OF JOSEPHINE AND SISKIYOU COUNTIES. AN INCH
TO AN INCH AND A QUARTER HAS BEEN MEASURED DURING THE PAST FEW
HOURS IN THE CURRY COUNTY MOUNTAINS...AND THAT WILL BE THE BULK OF
THE COASTAL RAINFALL AS THE FRONT HAS MOVED EAST OF COOS AND CURRY
COUNTIES. RAIN WILL BE MAINLY LIGHT, LOCALLY NOT JUST MODERATE BUT
HEAVY ON THE WEST SIDE THROUGH AROUND 8 AM. THE WEST SIDE VALLEYS
ALONG AND EAST OF INTERSTATE 5 ARE EXPECTED TO RECEIVE AROUND ONE
TO TWO TENTHS OF AN INCH OF RAIN...MAINLY TOWARD THE LOW END OF
THAT RANGE. THE FRONT WILL WEAKEN AS IT REACHES THE EAST SIDE
WITH THE HIGHEST PROBABILITY OF MEASUREABLE RAIN IN NORTHERN
KLAMATH COUNTY THROUGH THIS MORNING. POST-FRONTAL SHOWERS WILL BE
SPARSE, LIGHT, AND MAINLY OVER THE COASTAL RANGE.

THOUGH THIS IS A FAST MOVING SYSTEM, THIS CHANGE TO AN ACTIVE, COOLER,
ONSHORE WEATHER PATTERN WILL PERSIST THROUGH THE NEXT WEEK. THE
UPPER LOW WILL TRACK NORTHEAST INTO WASHINGTON LATE TODAY THEN
ANOTHER BROAD LOW WILL MOVE FROM THE GULF OF ALASKA INTO THE
PACIFIC NORTHWEST. WINDS WITH THIS NEXT SYSTEM WILL NOT BE NEARLY
AS STRONG AS THE CENTER OF THIS LOW WITH THE COLDEST AIR/STRONGEST
PRESSURE GRADIENT WILL REMAIN WELL NORTH OF OUR AREA. BUT, IT WILL
BRING ANOTHER PERIOD OF MAINLY WEST SIDE RAINFALL LATE TONIGHT
INTO SUNDAY MORNING. THE GFS AND ECMWF HAVE TRENDED WETTER WITH
THIS SYSTEM. THE NAM REMAINS THE WEAKEST OF THE MODELS WITH THE
AMOUNT OF MOISTURE BUT CANNOT BE DISCOUNTED AS IT HAS INITIALIZED
VERY WELL WITH TODAY`S STORM. AS A RESULT, I RAISED THE WEST SIDE
RAINFALL AMOUNTS BUT SHAVED A BIT OFF OF THE GFS INDICATED
AMOUNTS. RAINFALL OF MORE THAN A TENTH OF AN INCH STILL LOOKS TO
BE LIMITED TO THE COAST AND DOUGLAS COUNTY. SHOWERS WILL GRADUALLY
TAPER OFF SUNDAY AFTERNOON INTO SUNDAY EVENING.

MONDAY WILL BE COOL WHILE OUR AREA REMAINS IN A LONGWAVE TROUGH
PATTERN. BUT NO RAIN IS EXPECTED AS THE STORM TRACK REMAINS AIMED
AT CANADA AND WASHINGTON. THE NEXT FRONT WILL KEEP ITS FOCUS WELL
NORTH OF US ON TUESDAY BUT THE SOUTHERN END OF THE FRONT HAS A
CHANCE OF BRINGING VERY LIGHT RAIN TO SOUTHWEST OREGON...
ESPECIALLY THE COAST AND DOUGLAS COUNTY LATE TUESDAY INTO TUESDAY
NIGHT.

IT WILL BE THE SAME STORY BUT WITH A BIT MORE UNCERTAINTY IN THE
DETAILS OF TIMING AND STRENGTH WITH ANOTHER FEW ADDITIONAL
DISTURBANCES POSSIBLE IN THE WESTERLY FLOW ALOFT WEDNESDAY INTO
FRIDAY. BY NEXT WEEKEND AND INTO LABOR DAY, THE GFS MAY BE TOO
PROGRESSIVE AND STRONG WITH RIDGING BUT THERE LOOKS TO BE A MODEST
DRYING AND WARMING TREND.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WARNING UNTIL 2 PM PDT THIS AFTERNOON FOR ORZ021-022.
     HIGH SURF ADVISORY UNTIL 5 PM PDT THIS AFTERNOON FOR ORZ021-022.
     HIGH WIND WARNING UNTIL 5 PM PDT THIS AFTERNOON FOR ORZ030-031.
     WIND ADVISORY UNTIL 5 PM PDT THIS AFTERNOON FOR ORZ029.

CA...HIGH WIND WARNING UNTIL 5 PM PDT THIS AFTERNOON FOR CAZ085.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS FROM 2 PM THIS
     AFTERNOON TO 11 PM PDT THIS EVENING FOR PZZ370.
     GALE WARNING UNTIL 2 PM PDT THIS AFTERNOON FOR
     PZZ350-356-370-376.
     HAZARDOUS SEAS WARNING UNTIL 11 PM PDT THIS EVENING FOR
     PZZ350-370.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM PDT THIS EVENING FOR
     PZZ350.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 5 PM PDT THIS AFTERNOON FOR
     PZZ356-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 5 PM THIS AFTERNOON
     TO 11 PM PDT THIS EVENING FOR PZZ356-376.
     HAZARDOUS SEAS WARNING UNTIL 5 PM PDT THIS AFTERNOON FOR
     PZZ356-376.

$$


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