Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 311558
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
858 AM PDT FRI JUL 31 2015

.UPDATE...SHAPING UP FOR ANOTHER UNSTABLE DAY. AIR MASS OVER
SOUTHWEST OREGON WILL BECOME QUITE UNSTABLE THIS AFTERNOON. NAM
MODEL SOUNDING FOR MEDFORD AT 21Z GIVES ABOUT 1000 CAPE WITH A
CONDENSATION LEVEL AT 12000 FT AGL. SO LOOKING FOR DRY
THUNDERSTORMS. THE GRIDS WERE UPDATED TO INCLUDE THUNDER BUT NO
RAIN TODAY. BIG ITEM OF CONCERN IS A SHORT WAVE NEAR LAKE TAHOE AT
15Z THIS MORNING. GFS AND NAM BOTH SHOW IT WELL - EC IS MISSING
IT. THIS WILL COME TO SISKIYOU/MODOC COUNTIES THIS EVENING.
LOOKING FOR NOCTURNAL THUNDERSTORMS FROM IT. I NEED TO DO A BIT
MORE ANALYSIS TO SEE WHERE THE CLOUD BASES WILL BE. BELIEVE THEY
WILL BE PRETTY DRY. THE SHORT WAVE RUNS INTO A BIT OF A
DEFORMATION ZONE AROUND THE OR/CA BORDER WHICH SLOWS IT DOWN AND
STRETCHES IT. THE SHORT WAVE WILL STILL CROSS INTO SOUTHERN OREGON
TOWARDS MORNING SATURDAY. COULD BE ENOUGH OF A TRIGGER FOR
THUNDERSTORMS. JBL

&&

.AVIATION...FOR THE 31/12Z TAF CYCLE...STRATUS WITH IFR CIGS/VIS HAS
MOVED AS FAR NORTH AS CAPE BLANCO THIS MORNING. IT MAY BRIEFLY MOVE
INTO KOTH THIS MORNING, BUT IT IS BEING LIMITED BY HIGH CLOUD.
STRATUS SHOULD BURN OFF TO VFR ALONG THE COAST BY LATE MORNING.
INLAND, EXPECT VFR CONDITIONS THROUGH THE TAF PERIOD EXCEPT FOR
AREAS OF SMOKE FROM TWO WILDFIRES IN DOUGLAS COUNTY...WHICH WILL
BRING MVFR VISIBILITIES IN HAZE AND SMOKE THIS MORNING IN THE UMPQUA
VALLEY, INCLUDING KRBG. AREAS OF MVFR VISIBILITIES IN HAZE MAY ALSO
AFFECT THE ROGUE VALLEY, INCLUDING KMFR, IN THE AFTERNOON.  IN THE
AFTERNOON AND EVENING, EXPECT THUNDERSTORMS TO DEVELOP OVER THE
CASCADES WITH POSSIBLE GUSTY OUTFLOW WINDS. -CC/WRIGHT

&&

.MARINE...UPDATED 300 AM PDT FRIDAY 31 JULY 2015...A THERMAL TROUGH
NEAR THE COAST WILL CONTINUE TO BRING MODERATE TO STRONG NORTH WINDS
AND CHOPPY WIND-DRIVEN SEAS REACHING ADVISORY CRITERIA THROUGH
FRIDAY NIGHT...POSSIBLY INTO SATURDAY. CONDITIONS WILL GRADUALLY
LOWER SATURDAY INTO SUNDAY AS THE THERMAL TROUGH WEAKENS AND MOVES
INLAND. WINDS AND SEAS ARE EXPECTED TO GRADUALLY LOWER THIS
WEEKEND...BUT WILL REMAIN MODERATE THROUGH NEXT WEEK...WITH A
POSSIBLE RETURN TO ADVISORY CONDITIONS IN THE SOUTHERN OUTER WATERS
AS EARLY AS WEDNESDAY. -MSC

&&

.MARINE...UPDATED 400 AM PDT FRIDAY 31 JULY 2015...RED FLAG
WARNINGS HAVE BEEN ISSUED FOR HAINES 6 ON EXISTING FIRES FOR BOTH
THE CABLE CROSSING FIRE (FIRE WX ZONES 616) AND THE STOUTS FIRE
(STRADDLING THE BORDER OF 616/617). TO COMPLICATE MATTERS MORE,
ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED OVER THE EASTERN
PORTION OF 617 THIS AFTERNOON WHICH PROMPTED THE ISSUANCE OF A RED
FLAG WARNING FOR THAT ALSO.

ALL PARAMETERS LOOK SUFFICIENT TO KICK OFF ISOLATED TO SCATTERED
THUNDERSTORMS OVER THE CASCADES AND SISKIYOUS THIS AFTERNOON, AND
BASES WILL LIKELY BE QUITE HIGH AND STORMS WILL PRODUCE LITTLE RAIN.
THE DRY NATURE OF THE STORMS AS WELL AS THE ANTECEDENT FUEL
CONDITIONS CAUSED US TO UPGRADE THE WATCH TO A WARNING DESPITE THE
POSSIBILITY OF LESS THAN SCATTERED COVERAGE. THE STORMS ARE
EXPECTED TO REMAIN ANCHORED IN THE MOUNTAINS AND NOT DRIFT OUT
OVER THE VALLEYS WHERE CONDITIONS SHOULD REMAIN LARGELY CAPPED
TODAY. FIRE WEATHER WATCHES FOR TODAY WERE CANCELED ON THE WEST
SIDE AS A RESULT. THAT`S NOT TO SAY THAT IT`S IMPOSSIBLE FOR A
STORM TO DRIFT OFF THE MOUNTAINS, IT`S JUST NOT VERY LIKELY TODAY.

AS IF ALL THAT WEREN`T ENOUGH, IT WILL BE VERY DRY, HOT, AND BREEZY
OVER PORTIONS OF THE EAST SIDE THIS AFTERNOON. AREAS FROM FAR
EASTERN LAKE COUNTY THROUGH MODOC COUNTY WILL BE NEAR CRITICAL WIND
AND HUMIDITY, BUT WE FELT IT WASN`T WIDESPREAD ENOUGH TO WARRANT A
WARNING TODAY. WE WILL BE HEADLINING IT IN THE FIRE WEATHER
FORECAST.

ISOLATED TO SCATTERED STORMS ARE POSSIBLE OVER A MUCH WIDER AREA
SATURDAY, OWING TO INCREASING MOISTURE, INSTABILITY, AND THE
POSSIBILITY OF A GOOD TRIGGER ARRIVING THROUGH THE SOUTHERLY FLOW
ALOFT. STORMS WILL LIKELY START OFF DRY AND THEN TEND TO GET WETTER
THROUGH THE EVENING, ESPECIALLY OVER CALIFORNIA. FIRE WEATHER
WATCHES HAVE BEEN ISSUED OVER MUCH OF OUR FORECAST AREA TO HIGHLIGHT
THIS POTENTIAL. IT IS NOTEWORTHY THAT SOME GUIDANCE SHOWS THESE
STORMS CONTINUING THROUGH SATURDAY NIGHT ACROSS THE WEST SIDE OREGON
ZONES. -WRIGHT

&&

.PREV DISCUSSION... /ISSUED 447 AM PDT FRI JUL 31 2015/
WILDFIRE ACTIVITY HAS BEEN PICKING UP ACROSS THE FORECAST AREA
OVER THE LAST 24 HOURS. LAST EVENING THE STOUTS FIRE WAS REPORTED
TO BE AT LEAST 6,000 ACRES OVER SOUTHEASTERN DOUGLAS COUNTY
NEAR MILO AND TILLER AFTER REPORTEDLY STARTING AROUND 1PM PDT
YESTERDAY AFTERNOON. HAINES 6 CONDITIONS CAUSED THIS FIRE TO TAKE
ON THE FORM OF A THUNDERSTORM, CAUSING NUMEROUS CLOUD TO GROUND
LIGHTNING STRIKES AND HUNDREDS OF IN CLOUD RUMBLES. WITH HOT AND
DRY CONDITIONS PEAKING TODAY AND MORE THUNDERSTORMS EXPECTED
DURING THE NEXT SEVERAL DAYS, MORE IGNITIONS ARE NEARLY CERTAIN.
HAZE AND SMOKE HAS BEEN ADDED TO THE SHORT TERM FORECAST AS WE
BEGIN TO TRACK THIS INCREASING IMPACT.

THIS MORNING`S INFRARED SATELLITE IMAGERY SHOWS THE AREA OF SMOKE
ALOFT GENERATED BY YESTERDAY`S LARGE FIRE ACTIVITY IN DOUGLAS
COUNTY MOVING NORTHEASTWARD ACROSS THE COLUMBIA RIVER TOWARD
LEWISTON, IDAHO. SOUTH FLOW IS EVIDENT SEVERAL HUNDRED MILES WEST
OF THE CALIFORNIA COAST AS POCKETS OF INSTABILITY AND MOISTURE
MOVE NORTHWARD. THE CHALLENGE FOR THE NEXT SEVERAL DAYS WILL BE
PICKING UP ON THE LOCATION AND TIMING OF THESE FEATURES AND THEIR
RESULTANT SHOWER AND THUNDERSTORM ACTIVITY.

THE HEAT ADVISORY FOR MANY VALLEY LOCATIONS REMAINS IN EFFECT
UNTIL 11 PM PDT SATURDAY EVENING. WE EXPECT TEMPERATURES FOR THIS
HEAT WAVE TO PEAK TODAY. FOR PLACES SUCH AS ROSEBURG THERE IS AN
OUTSIDE POSSIBILITY THAT THE ALL TIME RECORD HIGH FOR THAT SITE
OF 109F SET ON JULY 20TH, 1946 MAY BE TIED OR EVEN BROKEN. FOR
MANY OTHER SITES, IT`S LIKELY TO BE THE HOTTEST TEMPERATURE
OBSERVED, THUS FAR, THIS YEAR AND BREAK THE CALENDAR DAY RECORD.

WE EXPECT SMOKE FROM THE FIRES IN DOUGLAS COUNTY TO MOSTLY REMAIN
IN THAT COUNTY THIS MORNING, BUT AFTERNOON AND EVENING WINDS ARE
LIKELY TO PUSH SOME OF IT SOUTHEASTWARD INTO THE ROGUE VALLEY
THIS AFTERNOON AND THEN SOUTHWESTWARD OVERNIGHT TONIGHT.

AS FAR AS THUNDERSTORMS GO, THERE IS A LOW PRESSURE DISTURBANCE
NEAR LAKE TAHOE THIS MORNING THAT WE WILL BE WATCHING. THIS
FEATURE AND SURFACE BASED INSTABILITY FROM AFTERNOON HEATING ARE
EXPECTED TO SPARK OFF ISOLATED TO SCATTERED DRY THUNDERSTORM
ACTIVITY IN THE OREGON CASCADES AND SISKIYOUS AND ISOLATED MOSTLY
DRY STORMS ACROSS SISKIYOU COUNTY THIS AFTERNOON. AFTERNOON AND
EVENING LOW LEVEL NORTHWEST WINDS ON THE OREGON WEST SIDE ARE
EXPECTED TO MOSTLY KEEP THUNDERSTORMS BOTTLED UP ALONG THE
CASCADES AND SISKIYOUS THIS AFTERNOON AND EVENING.

TONIGHT MODELS INDICATE A SLIGHT SURGE IN NORTHEAST WINDS ACROSS
THE CASCADES AND WEST SIDE AGAIN BETWEEN SHORTWAVE LOW PRESSURE
DISTURBANCES. SATURDAY CURRENTLY APPEARS TO BRING THE GREATEST
THREAT OF THUNDERSTORMS FOR AREAS WEST OF THE CASCADES. THE GFS
MODEL INDICATES A SIGNIFICANT THUNDERSTORM OUTBREAK ACROSS THE WEST
SIDE, ESPECIALLY IN AND EAST OF THE COAST RANGE SATURDAY
AFTERNOON AND EVENING, WHILE OTHER MODELS KEEP THIS ACTIVITY CLOSER
TO THE CASCADES AND SISKIYOUS. PRECIPITABLE WATER VALUES INCREASE
TO OVER AN INCH OVER MOST OF THE AREA WEST OF THE CASCADES
SATURDAY AFTERNOON AND EVENING, BUT WITH VERY DRY FUELS WE EXPECT
LIGHTNING EFFICIENCY TO BE VERY HIGH WHERE SIGNIFICANT RAINFALL
DOES NOT OCCUR. FIRE SPREAD WILL ALSO BE A CONCERN. ALL IN ALL,
GUIDANCE COLLECTIVELY INDICATES THUNDERSTORMS REACHING THE WEST
SIDE VALLEYS OF JACKSON AND JOSEPHINE COUNTIES. THE UNCERTAINTIES
MOSTLY LIE IN HOW FAR NORTHWEST THE THUNDERSTORMS WILL MAKE IT,
COVERAGE OF LIGHTNING, AND WHERE THE MOST RAIN WILL FALL. AT THIS
POINT, MAX RAINFALL LOOKS TO BE IN THE KLAMATH, SCOTT, AND SHASTA
VALLEY AREAS OF NW CALIFORNIA WHERE LOCALIZED 1 INCH AMOUNTS WILL
BE POSSIBLE.

SUNDAY THROUGH WEDNESDAY THERE STILL REMAINS A THREAT OF SHOWERS
AND THUNDERSTORMS OVER THE AREA. AS TEMPERATURES COOL AND THE
AIR MASS MODERATES AND MOISTENS, WE EXPECT THE NEW FIRE THREAT TO
GO DOWN AND MOST STORMS TO PRODUCE RAINFALL. BY ABOUT WEDNESDAY OF
NEXT WEEK IT`S MOST LIKELY THAT TEMPERATURES WILL FALL TO AT OR
BELOW NORMAL VALUES ACROSS THE FORECAST ARE WITH 80S RETURNING TO
MEDFORD FOR THE LATTER PORTION OF THE WEEK. BTL

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...FIRE WEATHER WATCH FROM SATURDAY AFTERNOON THROUGH SATURDAY
     EVENING FOR ORZ615>617-619-620-622.
     RED FLAG WARNING UNTIL 9 PM PDT THIS EVENING FOR ORZ616.
     HEAT ADVISORY UNTIL 11 PM PDT SATURDAY FOR ORZ023.
     RED FLAG WARNING FROM 2 PM THIS AFTERNOON TO 11 PM PDT THIS
     EVENING FOR ORZ617.
     RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR ORZ621-623.
     FIRE WEATHER WATCH FROM SATURDAY MORNING THROUGH SATURDAY
     EVENING FOR ORZ621-623.
     HEAT ADVISORY UNTIL 11 PM PDT SATURDAY FOR ORZ024-026.
     FIRE WEATHER WATCH FROM SATURDAY AFTERNOON THROUGH SATURDAY
     EVENING FOR ORZ624.

CA...FIRE WEATHER WATCH FROM SATURDAY AFTERNOON THROUGH SATURDAY
     EVENING FOR CAZ280-281-284.
     HEAT ADVISORY UNTIL 11 PM PDT SATURDAY FOR CAZ080-081.

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

$$



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