Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 300359
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
859 PM PDT TUE JUL 29 2014

.DISCUSSION...THIS EVENING SAW A FLURRY OF THUNDERSTORMS DEVELOP
FROM THE SISKIYOUS NORTHEASTWARD UP ALONG THE CASCADES TO NORTHERN
KLAMATH COUNTY...INCLUDING A LONG-LIVED LEFT-MOVING SUPERCELL THAT
HUGGED HIGHWAY 97 FROM JUST EAST OF CRATER LAKE TO CHEMULT...BEFORE
FINALLY DYING SOUTH OF CRESCENT. A PUBLIC REPORT NEAR THE
JUNCTION OF HIGHWAYS 138 AND 97 INDICATED HAIL COVERING THE
GROUND. SEE OUR FACEBOOK POST WHICH DETAILS THE SATELLITE`S VIEW
OF THE OVERSHOOTING TOP ASSOCIATED WITH THIS STORM. ANOTHER
NOTABLE CELL PRODUCED 0.20-0.40 OF AN INCH OF RAINFALL AROUND
ASHLAND IN ABOUT AN HOUR`S TIME. ACTIVITY SHOULD CONTINUE TO WANE
LATE THIS EVENING AND OVERNIGHT WITH THE LOSS OF INSTABILITY, BUT
WILL MAINTAIN A SLIGHT CHANCE OF THUNDERSTORMS EAST OF A LINE FROM
ABOUT DIAMOND/CRATER LAKE SOUTHEASTWARD TO MODOC COUNTY. EXPECT A
REPEAT PERFORMANCE ACROSS THE AREA WEDNESDAY AND A RED FLAG
WARNING IS ALREADY OUT FOR THAT AT RFWMFR. THE REST OF THE
FORECAST IS ON TRACK. SPILDE

&&

.AVIATION...BASED ON THE 30/00Z TAFS...

ALONG THE COAST...AREAS OF LIFR CIGS WITH MVFR VSBYS AND HIGHER
TERRAIN OBSCURED WILL PERSIST THROUGH WEDNESDAY MORNING...WITH SOME
AREAS CLEARING TO VFR IN THE AFTERNOON.  THE LOWER CONDITIONS WILL
RETURN BY WEDNESDAY EVENING.  ELSEWHERE...VFR CONDITIONS WILL
PREVAIL THROUGH WEDNESDAY EVENING...BUT THERE WILL BE AFTERNOON AND
EVENING THUNDERSTORMS...MOSTLY FROM THE CASCADES EAST AND SISKIYOUS
SOUTH. STOCKTON

&&

.MARINE...UPDATED 400 PM PDT 29 JULY 2014...

THE CURRENT PATTERN...WITH SOME SLIGHT DAY-TO-DAY VARIATION...WILL
PERSIST THIS WEEK. OFFSHORE HIGH PRESSURE  AND A THERMAL TROUGH OVER
NORTHERN CALIFORNIA WILL COMBINE TO MAINTAIN STEEP WIND WAVE
DOMINATED SEAS AND AREAS OF SMALL CRAFT ADVISORY WINDS INTO THE
WEEKEND...WITH THE STRONGEST WINDS AND STEEPEST SEAS FROM CAPE
BLANCO SOUTH IN THE AFTERNOONS AND EVENINGS.  WINDS MAY INCREASE TO
GALES WITH VERY STEEP SEAS LATE IN THE WEEK FOR AREAS SOUTH OF CAPE
BLANCO. STOCKTON

&&

.PREV DISCUSSION... /ISSUED 310 PM PDT TUE JUL 29 2014/

DISCUSSION...
BUREAU OF LAND MANAGEMENT LIGHTNING DETECTION HAD INDICATED ABOUT
100 LIGHTNING STRIKES SCATTERED ABOUT THE FORECAST AREA AS OF 246
PM PDT. WHILE STORM MOVEMENT HAS BEEN GENERALLY SLOW TO THE
NORTHEAST AT 10 MILES PER HOUR, MANY LIGHTNING STRIKES APPEAR TO
BE FALLING OUTSIDE OF RAIN CORES, LIKELY BECAUSE THE ANVILS OF THE
STORMS ARE BEING BLOWN AND SPREAD NORTHEASTWARD AT A FASTER SPEED
THAN THE LOWER PORTIONS OF THE STORMS, AROUND 30 KNOTS. ALSO,
STORMS HAVE BEEN FAIRLY PULSEY, IN THAT INDIVIDUAL CELLS ARE
COLLAPSING WITHIN ABOUT A HALF HOUR OF FORMING.

FOR THE REST OF THE AFTERNOON INTO THE EVENING EXPECT SCATTERED
THUNDERSTORMS TO CONTINUE ACROSS SISKIYOU COUNTY AND FROM THE
CASCADES EASTWARD. WHILE THUNDERSTORMS ARE STILL POSSIBLE IN THE
MOUNT SHASTA AREA AND OVER THE SISKIYOUS AND JACKSON COUNTY, THEY
ARE LIKELY TO REMAIN ISOLATED IF THEY DO INDEED OCCUR.
ADDITIONALLY, WHILE ISOLATED HAIL AND GUSTY WINDS ARE POSSIBLE,
THE MAIN THREAT FROM THE STORMS WILL CONTINUE TO BE FIRE STARTS
FROM LIGHTNING.

FIRE WEATHER WATCHES FOR WEDNESDAY HAVE BEEN UPGRADED TO WARNINGS
IN ALL AREAS EXCEPT THE MOUNT SHASTA FIRE WEATHER ZONE, WHERE
SOUTH FLOW IS LIKELY TO CAUSE STORM FORMATION TO BE DOWNWIND OF
THE VOLCANO AND OTHER PEAKS. A 500MB TROUGH, THOUGH SUBTLE, WILL MOVE
ACROSS THE FORECAST AREA FROM THE SOUTH AROUND THE TIME OF MAXIMUM
HEATING. DUE TO A BIT OF A JOG WESTWARD IN THE MID-LEVEL FLOW,
EXPECT THAT WEDNESDAY IS THE BEST CHANCE FOR THUNDERSTORMS IN THE
ROGUE VALLEY.

WATCHES HAVE BEEN ISSUED FOR THURSDAY, BUT ONLY IN AREAS WHERE
MODEL LIFTED INDICES ARE -3C OR LOWER. ALTOGETHER, SOME GUIDANCE
SUGGESTS THE THREAT OF STORMS WILL BEGIN TO SHIFT EASTWARD, THOUGH
THE EUROPEAN MODEL GUIDANCE INDICATES A THREAT MAY STILL EXIST ON
THE WEST SIDE THROUGH SATURDAY.

ALTOGETHER, IT APPEARS THE THREAT OF THUNDERSTORMS FROM
DISTURBANCES EMBEDDED IN THE BROAD SOUTH TO SOUTHWEST FLOW WILL
BEGIN TO DRIFT EASTWARD THIS WEEKEND. HOWEVER, DETAILS ARE STILL
UNCERTAIN. DURING THE ENTIRE PERIOD, TEMPERATURES WILL ONLY COOL
SLIGHTLY. IN OTHER WORDS, DAY TO DAY CHANGES WILL BE SUBTLE. BTL

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR
     ORZ617-621>625.
     RED FLAG WARNING FROM 2 PM TO 11 PM PDT WEDNESDAY FOR
     ORZ617-621>625.
     FIRE WEATHER WATCH FROM THURSDAY AFTERNOON THROUGH THURSDAY
     EVENING FOR ORZ617-623>625.

CA...RED FLAG WARNING FROM 2 PM TO 11 PM PDT WEDNESDAY FOR
     CAZ280-281-284-285.
     RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR
     CAZ280>282-284-285.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM PDT
     THURSDAY FOR PZZ356-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT THURSDAY
     FOR PZZ356-376.
     SMALL CRAFT ADVISORY FOR WINDS FROM 11 AM TO 11 PM PDT THURSDAY
     FOR PZZ350-370.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 11 AM TO 11 PM PDT
     THURSDAY FOR PZZ350-370.

$$

MAS/BTL/JRS/SBN





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