Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 011511
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
811 AM PDT SAT AUG 1 2015

.UPDATE...MADE A QUICK UPDATE THIS MORNING TO ADD A SLIGHT CHANCE
OF THUNDER ASSOCIATED WITH ISOLATED CELLS STRETCHING ACROSS FAR
SOUTHWEST OREGON FROM CURRY COUNTY TO WESTERN JACKSON COUNTY
(MAINLY FROM MEDFORD WEST). MOST OF THESE ARE NOT PRODUCING
RAINFALL. THE REST OF THE FORECAST IS UNCHANGED. SPILDE

&&

.DISCUSSION...THUNDERSTORMS ARE THE MAIN THREAT ACROSS THE AREA
TODAY AS AN UPPER LEVEL LOW PRESSURE SYSTEM SPINS OFF THE
CALIFORNIA COAST. THE RESULTANT SOUTH TO SOUTHEAST FLOW ALOFT IS
BRINGING DEEPER MOISTURE INTO THE AREA, MAINLY AT THE MID AND
UPPER LEVELS. STRONG SURFACE HEATING AGAIN WILL BE THE MAIN DRIVER
OF THUNDERSTORMS LATER THIS MORNING THROUGH THIS EVENING. BUT WITH
PROFILES SHOWING A SIGNIFICANT DRY LAYER AT THE LOW LEVELS
(BELOW CLOUD BASE), WE EXPECT MOST OF THE THUNDERSTORMS THAT DO
OCCUR TO BE DRY. RED FLAG WARNINGS ARE IN EFFECT AT RFWMFR. A HEAT
ADVISORY AT NPWMFR REMAINS IN EFFECT THROUGH THIS EVENING. A
STRONGER SHORT WAVE WILL MOVE NORTHWARD LATER TONIGHT AND SUNDAY,
WITH A BETTER CHANCE OF SHOWERS AND THUNDERSTORMS ALONG WITH
DEEPENING MOISTURE PROFILES. THESE STORMS SHOULD BE WETTER THAN
TODAY, BUT SOME STILL COULD PRODUCE LIGHTNING OUTSIDE RAIN CORES.
WE`LL BE EVALUATING THIS MORE THROUGHOUT THE DAY. SPILDE

&&

.AVIATION...FOR THE 01/12Z TAF CYCLE...ALONG THE COAST...AREAS OF
IFR CIGS/VSBYS ALONG THE COAST WILL CLEAR TO VFR BY LATE
MORNING...BUT THE IFR CIGS WILL REMAIN OFFSHORE. THE LOWER
CONDITIONS WILL MOVE BACK ONSHORE LATE THIS AFTERNOON AND EVENING.
INLAND FROM THE COAST, ISOLATED TO SCATTERED AFTERNOON AND EVENING
DRY THUNDERSTORMS WILL BRING GUSTY WINDS, BUT CONDITIONS WILL REMAIN
VFR. THE EXCEPTION WILL BE AREAS OF MVFR VIS IN SMOKE DOWNWIND OF
THE FIRES IN THE UMPQUA. THIS INCLUDES KMFR. -WRIGHT

&&

.MARINE...UPDATED 4 AM PDT SATURDAY 1 AUGUST 2015...LIGHT NORTHERLY
FLOW AND LIGHT CHOP ARE EXPECTED TO CONTINUE OVER THE WATERS FOR THE
NEXT SEVERAL DAYS AS A WEAK THERMAL TROUGH REMAINS INLAND FROM THE
COAST. OFFSHORE HIGH PRESSURE STRENGTHENS AND A THERMAL TROUGH
REDEVELOPS ALONG THE COAST LATER TUESDAY AT WHICH POINT SMALL CRAFT
ADVISORY WINDS AND SEAS ARE EXPECTED TO RETURN. WINDS AND SEAS
INCREASE THROUGH THE REMAINDER OF THE WEEK AS THESE FEATURES
STRENGTHEN. -WRIGHT

&&

.PREV DISCUSSION... /ISSUED 436 AM PDT SAT AUG 1 2015/

DISCUSSION...
APPROXIMATELY 200 DRY CLOUD TO GROUND LIGHTNING STRIKES OCCURRED
ACROSS THE FORECAST AREA YESTERDAY AFTERNOON AND EVENING. MOST OF
THESE WERE IN SISKIYOU COUNTY AND OREGON CASCADES AND SISKIYOUS.
THE ONLY DEFINITIVE RAINFALL REPORT ACROSS THE AREA WAS 0.06" NEAR
HAPPY CAMP AT THE DUTCH INDY RAWS. A QUICK LOOK THROUGH REPORTS
FROM THE FIRE AGENCIES INDICATES AT LEAST 10 NEW FIRE STARTS IN
THE LAST 24 HOURS ACROSS THE FORECAST AREA.

SMOKE, MAINLY FROM THE STOUTS FIRE AND THE CABLE CROSSING FIRE, HAS
BECOME A SIGNIFICANT CONCERN IN THE LAST 12-24 HOURS, AS AFTERNOON
NORTHWEST WINDS BROUGHT THIS SMOKE SOUTHEASTWARD OF THOSE FIRES
AND INTO THE ROGUE VALLEY AS HAD BEEN EXPECTED, THOUGH QUITE
THICK AT GROUND LEVEL. 24 HOUR AIR QUALITY INFORMATION FROM THE
OREGON DEPARTMENT OF ENVIRONMENTAL QUALITY INDICATES MEDFORD MOVED
INTO THE VERY UNHEALTHY CATEGORY AND SHADY COVE UNHEALTHY LAST
EVENING. DURING THE PAST HOUR CONDITIONS HAVE IMPROVED SOME WITH
THE WORST CONDITIONS BEING REPORTED IN MEDFORD AT UNHEALTHY FOR
SENSITIVE GROUPS. IT APPEARS THAT THE SMOKE WILL REMAIN IN THE
AREA THIS MORNING, THOUGH SOME EAST WIND IS HELPING TO DISPERSE
IT. IT SHOULD SHOULD LIFT SOME THIS AFTERNOON AND MOVE EASTWARD TO
THE OREGON CASCADES. TONIGHT WINDS WILL BE LIGHT ACROSS THE AREA,
SO AREAS THAT SEE SMOKE THIS EVENING WILL LIKELY HAVE IT STICK
AROUND UNDER THE NOCTURNAL INVERSION. HOW IMPACTING THE SMOKE IS
WILL DEPEND ON HOW ACTIVE THE FIRES GET TODAY AS WELL AS WHERE ANY
NEW FIRES ARE AND HOW SIGNIFICANT THEY BECOME.

RED FLAG WARNINGS ACROSS THE AREA HAVE BEEN EXTENDED FROM LATE
THIS MORNING THROUGH SUNDAY EVENING. THE LOWER LEVELS OF THE AIR
MASS IN PLACE WILL CONTINUE TO HAVE A DIFFICULT TIME MOISTENING
AS LOW PRESSURE REMAINS WELL OFFSHORE OVER THE NEXT 24 HOURS.
FORCING FOR THUNDERSTORMS TODAY IS LIKELY TO AGAIN BE DRIVEN BY
SURFACE HEATING UNDER SOUTHEAST FLOW, MUCH AS IT WAS ON FRIDAY.
HOWEVER, THE FLOW THIS AFTERNOON AND EVENING WILL BE LESS EASTERLY
AND MORE SOUTHERLY THAN YESTERDAY AND STRENGTHENING WITH TIME.
THIS WILL INCREASE THE POSSIBILITY THAT LIGHTNING WILL PUSH OUT OF
THE MOUNTAINS THIS AFTERNOON AND EVENING AND MOVE INTO SOME VALLEY
AREAS. PRIMARY CONCERNS ARE FOR SISKIYOU, JACKSON, AND JOSEPHINE
COUNTIES, WHERE CONFIDENCE IS MODERATE THAT STORMS WILL AFFECT THE
SOME PORTIONS OF THE VALLEYS WITH LIGHTNING AND OUTFLOW WINDS.
UNFORTUNATELY, DESPITE PWATS EXCEEDING 1 INCH THIS AFTERNOON AT
THE MEDFORD AIRPORT AND MUCH OF THE WEST SIDE, THE ELEVATED
NATURE OF THE MOISTURE IN THE ATMOSPHERIC PROFILE MEANS MOST
THUNDERSTORMS WILL STILL REMAIN DRY. COVERAGE WILL BE MOSTLY
ISOLATED TODAY OUTSIDE OF THE CASCADES, SISKIYOUS, AND SISKIYOU
COUNTY, WHERE IT WILL BE SCATTERED.

TONIGHT THROUGH SUNDAY THE PRIMARY NAM12 AND GFS20 MODELS INDICATE
SHORTWAVE TROUGH ENERGY FROM THE LOW OFFSHORE AND MONSOONAL
CONVECTION OVER THE GREAT BASIN COMBINING OVER THE FORECAST AREA
TO BRING A SIGNIFICANT THREAT OF THUNDERSTORMS. IN TERMS OF
LIGHTNING, THIS TIME PERIOD LOOKS AS IF IT WILL BE THE MAIN EVENT
OF THIS THUNDERSTORM PERIOD FOR NORTHERN CALIFORNIA AND FROM THE
OREGON CASCADES AREAS WESTWARD TO THE COAST. WHILE SOME RAINFALL
IS EXPECTED WITH SOME OF THE STORMS, WE EXPECT MANY NEW FIRE
STARTS DUE TO BOTH LIGHTNING ABUNDANCE AND ANTECEDENT CONDITIONS.

MONDAY AND TUESDAY A COOLING AND GENERAL DRYING TREND IS EXPECTED,
THOUGH THERE WILL STILL BE A SHOWER AND THUNDERSTORM THREAT MAINLY FROM
THE CASCADES EASTWARD. BTL

AVIATION...FOR THE 01/12Z TAF CYCLE...ALONG THE COAST...AREAS OF
IFR CIGS/VSBYS ALONG THE COAST WILL CLEAR TO VFR BY LATE
MORNING...BUT THE IFR CIGS WILL REMAIN OFFSHORE. THE LOWER
CONDITIONS WILL MOVE BACK ONSHORE LATE THIS AFTERNOON AND EVENING.
INLAND FROM THE COAST, ISOLATED TO SCATTERED AFTERNOON AND EVENING
DRY THUNDERSTORMS WILL BRING GUSTY WINDS, BUT CONDITIONS WILL REMAIN
VFR. THE EXCEPTION WILL BE AREAS OF MVFR VIS IN SMOKE DOWNWIND OF
THE FIRES IN THE UMPQUA. THIS INCLUDES KMFR. -WRIGHT

MARINE...UPDATED 4 AM PDT SATURDAY 1 AUGUST 2015...LIGHT NORTHERLY
FLOW AND LIGHT CHOP ARE EXPECTED TO CONTINUE OVER THE WATERS FOR THE
NEXT SEVERAL DAYS AS A WEAK THERMAL TROUGH REMAINS INLAND FROM THE
COAST. OFFSHORE HIGH PRESSURE STRENGTHENS AND A THERMAL TROUGH
REDEVELOPS ALONG THE COAST LATER TUESDAY AT WHICH POINT SMALL CRAFT
ADVISORY WINDS AND SEAS ARE EXPECTED TO RETURN. WINDS AND SEAS
INCREASE THROUGH THE REMAINDER OF THE WEEK AS THESE FEATURES
STRENGTHEN. -WRIGHT

FIRE WEATHER...UPDATED 355 AM PDT SATURDAY 1 AUGUST 2015...AN UPPER
TROUGH WILL REMAIN OFFSHORE AND CONTINUE TO PUMP MID LEVEL MOISTURE
AND INSTABILITY OVER OUR AREA THROUGH SUNDAY EVENING. THERE WILL BE
SEVERAL DISTURBANCES MOVING OVER THE AREA AS WELL. TIMING AND
LOCATION OF THE INDIVIDUAL DISTURBANCES WILL BE IMPORTANT, BUT
DIFFICULT AS WELL CONSIDERING HOW THE MODELS HAVE NOT DONE
PARTICULARLY WELL OVER THE LAST COUPLE OF DAYS. HOWEVER, ON THE
01/00Z AND 01/06Z RUNS, THE MODELS HAVE STARTED TO FOCUS ON A
SHORTWAVE SATURDAY NIGHT AND THEN ANOTHER SUNDAY AFTERNOON AS THE
MORE POTENT DISTURBANCES.

IN ADDITION, THE LOW LEVELS WILL REMAIN VERY DRY SO ANY STORMS ARE
EXPECTED TO BE DRY AND PRODUCE LITTLE IF ANY RAIN AT THE GROUND. THE
GREATEST THREAT FOR STORMS WILL BE DURING THE AFTERNOON AND EVENING
HOURS, HOWEVER, STORMS MAY CONTINUE OVERNIGHT IN MANY LOCATIONS.

GIVEN THAT THE THREAT WILL PERSIST TONIGHT AS WELL, WE DECIDED TO
EXTEND TODAY`S RED FLAG WARNING THROUGH SUNDAY EVENING. THIS COVERS
TONIGHT (SATURDAY NIGHT) AND EFFECTIVELY UPGRADES THE SLEW OF
WATCHES WE HAD FOR SUNDAY TO WARNINGS AS WELL. IT LOOKS LIKE STORMS
WILL REMAIN ISOLATED IN ZONE 625 (LAKE COUNTY) UNTIL SUNDAY
AFTERNOON, SO WE DIDN`T START THE WARNING UNTIL SUNDAY THERE.
HOWEVER, THE SOUTHERN PART OF THE ZONE MAY START EARLIER. STORMS
WILL TREND WETTER LATER SUNDAY INTO SUNDAY NIGHT AS THE COLUMN
MOISTENS FROM SOUTH TO NORTH.

WHILE NOT ALL LOCATIONS WILL GET THUNDERSTORMS DURING ALL THE
PERIODS, JUST ABOUT EVERYWHERE COULD SEE A LIGHTNING OUTBREAK AT
SOME POINT BETWEEN NOW AND SUNDAY NIGHT. -WRIGHT

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...RED FLAG WARNING FROM 11 AM SUNDAY TO 5 AM PDT MONDAY FOR
 ORZ625.
 RED FLAG WARNING FROM 2 PM THIS AFTERNOON TO 11 PM PDT
 SUNDAY FOR ORZ615>617-619-620-622.
 HEAT ADVISORY UNTIL 11 PM PDT THIS EVENING FOR ORZ023.
 RED FLAG WARNING FROM 11 AM THIS MORNING TO 11 PM PDT SUNDAY FOR
 ORZ621-623.
 HEAT ADVISORY UNTIL 11 PM PDT THIS EVENING FOR ORZ024-026.
  RED FLAG WARNING FROM 2 PM THIS AFTERNOON TO 5 AM PDT MONDAY FOR
 ORZ624.

CA...RED FLAG WARNING FROM 2 PM THIS AFTERNOON TO 11 PM PDT SUNDAY
     FOR CAZ280-281-284.
     HEAT ADVISORY UNTIL 11 PM PDT THIS EVENING FOR CAZ080-081.
     RED FLAG WARNING FROM 2 PM THIS AFTERNOON TO 11 PM PDT SUNDAY
     FOR CAZ285.

PACIFIC COASTAL WATERS...NONE.

$$

MAS/BTL/TRW



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