Flash Flood in Oregon, August 10, 2013

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
221 PM PDT SAT AUG 10 2013

.DISCUSSION...THE UPPER LOW CONTINUES TO SPIN OVER SOUTHWEST
OREGON WITH SEVERAL SHORTWAVES MOVING THROUGH TODAY. THUNDERSTORMS
ARE ALREADY BLOWING UP ALONG THE CASCADES AND EASTERN DOUGLAS
COUNTY. MEANWHILE THE MID LEVEL CLOUD SHIELD IN WESTERN SISKIYOU
COUNTY IS ERODING...SO IT COULD BE A TIMING ISSUE AS TO HOW MUCH
THUNDERSTORM ACTIVITY DEVELOPS IN NORTHERN CAL...JOSEPHINE AND
JACKSON COUNTIES. FURTHER NORTH THUNDERSTORMS WILL CONTINUE TO
INCREASE IN COVERAGE THROUGH EARLY THIS EVENING WITH SOME THAT COULD
BE MODERATE TO SEVERE PRODUCING MODERATE TO HEAVY RAIN...HAIL AND
GUSTY OUTFLOW WINDS. MODIFIED THE MORNING SOUNDING FOR THAT IT'S
EXPECTED TO LOOK LIKE THIS AFTERNOON AND IT'S SHOWING CAPE VALUES
NEAR 1400 J/KG AND PRECIPITABLE WATER VALUES NEAR AN INCH AND LIFTED
INDICES NEAR -6. THE RAP 13 AND LOCAL HRRR MODELS PUT MOST OF THE
QPF ALONG AND WEST OF THE CASCADES AND HAVE THUS INCREASED POPS AND
QPF IN THESE AREAS. HOWEVER MID LEVEL MOISTURE WILL INCREASE IN
NORTHERN KLAMATH AND LAKE COUNTIES WITH AT THE SAME TIME SHORTWAVES
ARE APPROACHING. SO EXPECT THIS AREA TO SEE INCREASED ACTIVITY AS
WELL.

RIGHT NOW...NOT MUCH IS GOING ON IN MODOC AND SOUTHERN LAKE
COUNTY...BUT WERE GETTING CUMULUS DEVELOPMENT AND EXPECT SOME
ACTIVITY THERE LATE THIS AFTERNOON.

THE UPPER LOW WILL MOVE INTO THE NORTHWEST PART OF THE FORECAST AREA
TONIGHT WITH A SOUTHWEST FLOW ALOFT DEVELOPING. THUNDERSTORMS SHOULD
DECREASE LATER THIS EVENING...THEN THE FOCUS FOR STORMS TONIGHT IS
EXPECTED TO SHIFT OVER THE NORTHERN CASCADES...NORTHERN LAKE AND
KLAMATH COUNTIES.

THE UPPER LOW FINALLY MOVES NORTH OF THE AREA SUNDAY AND WE'LL GET
INTO A SOUTHWEST FLOW ALOFT. THE CASCADES...EASTSIDE AND PARTS OF
THE SISKIYOUS HAVE THE BEST CHANCE OF GETTING THUNDERSTORMS IN THE
AFTERNOON AND EARLY EVENING...BUT IT'S POSSIBLE ISOLATED STORMS
COULD DEVELOP ALONG THE SISKIYOUS.

THE UPPER LOW CONTINUES TO MOVE NORTH AND WEAKEN MONDAY WITH A
CONTINUED SOUTHWEST FLOW OVER THE AREA. THE HIGHEST CHANCE FOR
THUNDERSTORMS WILL BE ALONG THE CASCADES INTO NORTHERN LAKE AND
KLAMATH COUNTIES. EVEN THEN WERE NOT EXPECTING ANYTHING SIGNIFICANT.
THE EC AND GFS SHOW ANOTHER UPPER LOW SETTING SHOP WEST OF THE GULF
OF ALASKA WITH A CONTINUES SOUTHWEST FLOW OVER THE AREA. THIS WILL
RESULT IN DRY CONDITIONS WITH TEMPERATURES NEAR NORMAL. WHILE I
CANNOT RULE OUT ANY CHANCE OF PRECIPITATION EAST OF THE
CASCADES...THE ODDS ARE LOW THAT WE'LL GET ANYTHING. -PETRUCELLI

&&

.AVIATION...BASED ON THE 08/18Z TAF CYCLE.

MAIN CONCERN THROUGH THIS EVENING WILL BE SCATTERED THUNDERSTORMS
FOR INLAND LOCATIONS. SOME OF THESE STORMS COULD BECOME SEVERE
PRODUCING GUSTY OUTFLOW WINDS IN THE VICINITY OF STORMS AND HAIL.
THERE IS ALSO A CHANCE FOR BRIEF MVFR CIGS AND REDUCTION IN VIS IN
HEAVIER STORMS BETWEEN 22-03Z. STORMS MOVEMENT WILL GENERALLY MOVE
FROM EAST TO WEST AFFECTING THE WESTSIDE TERMINALS.

AT THE COAST...EXPECT IFR CIGS TO RETURN BETWEEN 2-3Z AND CONTINUE
INTO SATURDAY MORNING. THERE IS A CHANCE FOR SOME ELEVATED
CONVECTION TO BE IN THE VICINITY OF KOTH BETWEEN 22-2Z.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR
     ORZ023>026-028-029.
     RED FLAG WARNING UNTIL 11 PM PDT SUNDAY FOR ORZ027-030-031.

CA...RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR CAZ080.

PACIFIC COASTAL WATERS...NONE.