Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 312146
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
246 PM PDT FRI JUL 31 2015

.DISCUSSION...AIR MASS OVER THE FORECAST AREA HAS BECOME QUITE
UNSTABLE THIS AFTERNOON. CONVECTION IS POPPING OVER ALL OF
NORTHERN CALIFORNIA AND AREAS EAST OF THE CASCADES. THE 12Z NAM
MODEL SOUNDING FOR MEDFORD AT 21Z GIVES ABOUT 1000 CAPE WITH A
CONDENSATION LEVEL AT 12000 FT AGL. JUST NOW STARTING TO SEE
CONVECTION NORTH OF THE SISKIYOUS. LOOKING FOR THESE THUNDERSTORMS
TO BE PRETTY MUCH DRY EVERYWHERE. BIG ITEM OF CONCERN IS A SHORT
WAVE MOVING NORTH ACROSS NORTHERN CALIFORNIA. GFS AND NAM BOTH
SHOW IT WELL. THIS WILL COME TO SISKIYOU/MODOC COUNTIES THIS
EVENING. LOOKING FOR NOCTURNAL THUNDERSTORMS FROM IT AND THEY
SHOULD ALSO 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.

THE UPPER RIDGE OVER THE AREA BEGINS TO BREAK DOWN AND SHIFT EAST
MONDAY. AS IT BREAKS DOWN, THE THUNDERSTORM THREAT DECREASES IN SW
OREGON BUT REMAINS FOR NORTHERN CALIFORNIA AND EAST OF THE
CASCADES INTO TUESDAY. LATER IN THE WEEK, THE UPPER FLOW TURNS
SOUTHWEST AND TAKES THE ATMOSPHERIC MOISTURE TO THE EAST OF THE
AREA. THE SOLUTIONS FROM THE GFS AND EC MODELS HAVE SOME
DIFFERENCES FROM MIDWEEK ON. THE GFS PUTS THE AREA UNDER A VERY
WEAK FLOW BETWEEN A CUTOFF LOW WEST OF 130W AND A SHORTWAVE IN
BRITISH COLUMBIA. THE EC HAS A MORE SUBSTANTIAL LOW ALONG THE
PACNW COAST. THE END RESULT IS PRETTY SIMILAR...COOLER DRY
WEATHER.


&&

.AVIATION...FOR THE 31/18Z TAF CYCLE...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...NORTHERN
CALIFORNIA AND PORTIONS EAST OF THE CASCADES WITH POSSIBLE GUSTY
OUTFLOW WINDS.
-SVEN

&&

.MARINE...UPDATED 245 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 THIS
EVENING. THE MODELS CONTINUE TO SHOW BORDERLINE SMALL CRAFT FOR
WINDS TONIGHT INTO SATURDAY FOR THE OUTER WATERS, BUT SUSPECT IT MAY
BE OVERDONE. FOR NOW WE`LL GO WITH THE IDEA OF WINDS AND SEAS
LOWERING TONIGHT INTO SATURDAY GIVEN THE THERMAL TROUGH IS EXPECTED
TO WEAKEN AND MOVE 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. -PETRUCELLI

&&

FIRE WEATHER...UPDATED 1030 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.
IN ADDITION EXTENSIVE ACCAS FIELD IN NORTHERN CALIFORNIA WITH A
SHORT WAVE APPROACHING FROM THE SOUTH THAT WILL MOVE INTO THE AREA
AROUND MAX HEATING...HAVE ADDED THAT AREA TO THE RED FLAG WARNING
FOR THIS AFTERNOON AND EVENING. THE DRY NATURE OF THE STORMS AS
WELL AS THE ANTECIDENT 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/SVEN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR
     ORZ621-623>625.
     RED FLAG WARNING FROM 2 PM TO 11 PM PDT SATURDAY FOR ORZ624.
     FIRE WEATHER WATCH FROM SUNDAY AFTERNOON THROUGH LATE SUNDAY
     NIGHT FOR ORZ621>625.
     RED FLAG WARNING FROM 2 PM TO 11 PM PDT SATURDAY 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 UNTIL 11 PM PDT THIS EVENING ABOVE 500 FEET FOR
     FOR ORZ617.
     RED FLAG WARNING FROM 11 AM TO 11 PM PDT SATURDAY FOR
     ORZ621-623.
     HEAT ADVISORY UNTIL 11 PM PDT SATURDAY FOR ORZ024-026.

CA...RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR
     CAZ280-281-284-285.
     FIRE WEATHER WATCH FROM SUNDAY AFTERNOON THROUGH LATE SUNDAY
     NIGHT FOR CAZ280>282-284-285.
     RED FLAG WARNING FROM 2 PM TO 11 PM PDT SATURDAY FOR
     CAZ280-281-284.
     HEAT ADVISORY UNTIL 11 PM PDT SATURDAY FOR CAZ080-081.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 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.

$$

JBL/MND/SBN



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