Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 042034
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
132 PM PDT SAT JUL 4 2015

UPDATED AVIATION

.DISCUSSION...ANOTHER DAY WITH WELL ABOVE NORMAL TEMPERATURES IS
FORECAST FOR THIS INDEPENDENCE DAY...WITH SOME THUNDERSTORM
CHANCES IN THE SOUTHEASTERN HALF OF THE FORECAST AREA.

SOUTHERN OREGON AND NORTHERN CALIFORNIA REMAIN UNDER A RELATIVELY
STAGNANT PATTERN...IN A COL AREA BETWEEN TROUGHING TO THE
SOUTHWEST AND NORTHEAST...AND RIDGING TO THE SOUTHEAST AND
NORTHWEST. MOISTURE AND INSTABILITY IS FOCUSED OVER NORTHERN
CALIFORNIA AND SOUTHERN LAKE AND KLAMATH COUNTIES...AND THAT IS
WHERE WE EXPECT THE BEST CHANCE OF THUNDERSTORMS TODAY. ONE NOTE
IS THE ADDITION OF THUNDERSTORM CHANCES IN KLAMATH FALLS TODAY
WITH THE MORNING UPDATE. THE LATEST RUN OF THE HOURLY HRRR MODEL
SHOWS SHOWERS AND SOME THUNDERSTORMS IN THE EASTERN
SISKIYOU...SOUTHERN KLAMATH...SOUTHERN LAKE...AND MODOC COUNTIES
FROM ABOUT 4PM-8PM.

WE ARE MAINTAINING A FIRE WEATHER WATCH FOR THE SOUTHEASTERN
PORTION OF THE FORECAST AREA...AND AS IS TYPICAL...ITS NOT A CUT
AND DRY SITUATION FOR THUNDERSTORM FORMATION TODAY INTO TOMORROW.
THE WATCH IS FOUND AT RFWMFR...AND PLEASE SEE THE LATEST FIRE
WEATHER DISCUSSION BELOW.

SOME HIGH CLOUDS WILL TRAVERSE THE FORECAST AREA...AND WITH A
GENERALLY COOLER AIR MASS IN PLACE...TEMPERATURES WILL BE A FEW
DEGREES COOLER THAN YESTERDAY. HOWEVER...WITH ALL THE OUTDOOR
ACTIVITIES EXPECTED TODAY...WE HAVE MAINTAINED AN IMPACT-BASED
HEAT ADVISORY FOR THE ROGUE...SHASTA...SCOTT...KLAMATH RIVER...AND
ILLINOIS VALLEYS. THE LATEST MODELS SUGGEST COOLING FOR THE
FORECAST AREA WILL BE VERY GRADUAL UNTIL THE MIDDLE OF NEXT WEEK
WHEN AN UPPER LOW MOVES THROUGH AND BRINGS TEMPERATURES TO NEAR OR
BELOW NORMAL. NOTE THIS COULD BE THE FIRST ROUND OF WIDESPREAD
BELOW NORMAL TEMPERATURES IN MORE THAN 30 DAYS.

&&

.AVIATION...FOR THE 04/18Z TAF CYCLE...ALONG THE COAST...VFR
CONDITIONS WILL PREVAIL ALONG THE COAST WITH AREAS OF MVFR/IFR
CIGS OFFSHORE. THE LOWER CONDITIONS WILL MOVE ONSHORE
TONIGHT...THEN BURN BACK TO THE COAST MID-MORNING SUNDAY. OVER THE
REMAINDER OF THE AREA...VFR CONDITIONS WILL PREVAIL THROUGH
SUNDAY...BUT ISOLATED TO SCATTERED AFTERNOON AND EVENING
THUNDERSTORMS WILL DEVELOP OVER NORTHERN CALIFORNIA AND THE
SOUTHERN PORTIONS OF LAKE AND KLAMATH COUNTIES SATURDAY. AFTERNOON
THUNDERSTORMS ON SUNDAY WILL BE MORE WIDESPREAD...GENERALLY FROM
THE CASCADES EAST AND SISKIYOUS SOUTH.

&&

.MARINE...UPDATED 300 AM PDT SATURDAY 4 JULY 2015...A THERMAL TROUGH
NEAR THE COAST WILL WEAKEN THROUGH THE WEEKEND. SMALL CRAFT ADVISORY
SEAS WILL PREVAIL INTO THIS AFTERNOON...WITH SMALL CRAFT
CONDITIONS FOR SEAS GENERALLY BEYOND 3NM FROM SHORE. SEAS WILL
GRADUALLY SUBSIDE LATER THIS EVENING AND WINDS AND SEAS WILL
REMAIN LIGHT THROUGH AT LEAST MIDWEEK. STRATUS AND FOG WILL
INCREASE IN COVERAGE AND AFFECT MOST OF THE COASTAL WATERS BY
SUNDAY.

&&

.FIRE WEATHER...UPDATED 830 AM PDT SATURDAY 4 JULY 2015...MOISTURE
FLOW WILL BE ENHANCED TODAY, AND ISOLATED TO SCATTERED THUNDERSTORMS
LOOK TO BE POSSIBLE OVER NORTHERN CALIFORNIA AND OREGON`S EAST SIDE.
MID LEVEL DRY AIR LOOKS LIKE IT WILL ALSO MOVE IN AND INHIBIT
THUNDERSTORM DEVELOPMENT WEST OF MEDICINE LAKE AND NORTH OF SUMMER
LAKE. THIS, TAKEN WITH THE MODEL INSTABILITY AND THE TRACKING OF
ENERGY FROM THE SOUTH, WOULD PLACE THE PRIMARY THREAT FOR SCATTERED
THUNDERSTORMS OVER MODOC COUNTY, EASTERN SISKIYOU COUNTY, AND
SOUTHERN LAKE AND KLAMATH COUNTIES BEGINNING SOMETIME LATE THIS
AFTERNOON AND INTO THE EVENING. MODEL SOLUTIONS DEPICT AREAS OF
INSTABILITY PERSISTING OVERNIGHT TONIGHT, AND DUE TO THIS, HAVE KEPT
A CHANCE FOR NOCTURNAL STORMS IN PLACE THROUGH SATURDAY NIGHT INTO
EARLY SUNDAY MORNING. SCATTERED THUNDERSTORMS ARE LIKELY TO DEVELOP
SUNDAY AFTERNOON AND EVENING AS DAYTIME HEATING INCREASES, AND
MOISTURE INFLOW REMAINS AIMED AT OUR AREA. WE ARE EXPECTING LOW
LEVELS OF THE ATMOSPHERE TO REMAIN DRY, AND ALTHOUGH MOST OF THE
STORMS SATURDAY AND SUNDAY SHOULD BE WET, THERE SHOULD BE ABUNDANT
LIGHTNING STRIKES OUTSIDE STORM CORES. THE DRY LOW LEVELS WOULD ALSO
INCREASE THE POTENTIAL FOR GUSTY AND ERRATIC WINDS IN THE VICINITY
OF THUNDERSTORMS. WITH THE POTENTIAL OF NUMEROUS NEW STARTS, INITIAL
ATTACK RESOURCES COULD BE STRETCHED THIN. FOR THESE REASONS, IT IS
POSSIBLE THAT THE CURRENT WATCHES WILL BE UPGRADED TO WARNINGS
DURING THE DAY, AFTER COORDINATING WITH LOCAL AGENCIES.

INCREASED MOISTURE AND THE PRESENCE OF AN UPPER LEVEL TROUGH WILL
KEEP AFTERNOON AND EVENING THUNDERSTORM CHANCES IN THE AREA THROUGH
THE NEXT WEEK. -BPN/SVEN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...FIRE WEATHER WATCH FROM 6 PM PDT THIS EVENING THROUGH SUNDAY
     EVENING FOR ORZ624-625.
     HEAT ADVISORY UNTIL 11 PM PDT THIS EVENING FOR ORZ024-026.

CA...FIRE WEATHER WATCH FROM 6 PM PDT THIS EVENING THROUGH SUNDAY
     EVENING FOR CAZ280-281-284-285.
     HEAT ADVISORY UNTIL 11 PM PDT THIS EVENING FOR CAZ080-081.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT THIS
     EVENING FOR PZZ350-356-370-376.

$$

NSK/BPN/JRS/SBN


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