Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 011042
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
342 AM PDT WED JUL 1 2015

.DISCUSSION...JUNE HAS ENDED...SEE CLIMATE DISCUSSION BELOW FOR
DETAILS ON RECORD JUNE HEAT...AND JULY HAS PICKED UP WHERE JUNE
LEFT OFF WITH RECORD HEAT ACROSS INLAND LOCATIONS OF SOUTHERN
OREGON AND NORTHERN CALIFORNIA. A STRONG UPPER RIDGE OF HIGH
PRESSURE IS NUDGING CLOSER TO THE FORECAST AREA TODAY...BRINGING
WITH IT WIDESPREAD 100-DEGREE TEMPERATURES...FROM THE UMPQUA BASIN
TO THE ILLINOIS AND ROGUE VALLEYS...AND DOWN INTO THE KLAMATH
RIVER...SCOTT...AND SHASTA VALLEYS. WE HAVE MAINTAINED THE HEAT
ADVISORY FOR THESE VALLEYS AT NPWMFR. EVEN THOUGH WE`VE ALREADY
HAD 2 HEAT ADVISORIES THIS SUMMER...THE CURRENT EPISODE IS
HISTORICALLY SIGNIFICANT. WITH YESTERDAY`S HIGH TEMPERATURE OF
103...WE ARE ON PACE TO REACH 103 5 DAYS IN A ROW. THIS HAS ONLY
HAPPENED 7 TIMES BEFORE...SINCE 1911. THIS PLACES THE RETURN
INTERVAL FOR THIS TYPE OF EVENT AT ONCE EVERY 10 YEARS OR SO.
PLEASE TRY TO HEED THE GUIDELINES FOR STAYING SAFE IN THE
HEAT...AND PASS THE WORD ALONG.

THE HEAT SHOULD PEAK TODAY AND TOMORROW AS THE 595DM RIDGE
BASICALLY TAKES RESIDENCE OVERHEAD...OR JUST SLIGHTLY TO THE
EAST. THIS WILL LIMIT THE AMOUNT OF INSTABILITY...MOISTURE...AND
SHORTWAVE ACTIVITY OVER THE CWA...THUS KEEPING THUNDERSTORM
CHANCES IN THE SLIGHT CATEGORY...AND MAINLY OVER THE CASCADES AND
NORTHERN CALIFORNIA. IT WAS TEMPTING TO REMOVE THUNDERSTORM
CHANCES TODAY...BUT A BROAD VORTICITY MAXIMUMB EVIDENT ON WV
IMAGERY AND ALL MODELS...WILL PUSH THROUGH THE FORECAST AREA THIS
AFTERNOON...GIVING A SLIGHT CHANCE OF THUNDERSTORMS TO THE MOST
FAVORABLE LOCATIONS LIKE THE CASCADES NORTH OF CRATER LAKE.

TOMORROW...THERE IS LITTLE IN THE WAY OF TRIGGER...BUT MOISTURE IN
THE 500MB-700MB RANGE IS INCREASING...AS WELL AS INSTABILITY. SO WE
HAVE A BROAD AREA OF SLIGHT CHANCE IN THE SOUTHEASTERN PORTION OF
THE CWA.

CONDITIONS BECOME MORE FAVORABLE FOR THUNDERSTORMS BEGINNING ON
FRIDAY AND MORESO ON SATURDAY...AS THE UPPER RIDGE AXIS SHIFTS
ORIENTATION TO ALLOW FOR A FETCH OF SOUTHEASTERLY FLOW ALOFT FROM
THE SIERRAS INTO NORTHERN CALIFORNIA. WE FOCUS THUNDERSTORM CHANCES
IN SISKIYOU AND MODOC COUNTIES FRIDAY...AND THEN EXPAND THIS AREA
NORTHWARD ON SATURDAY...AND THEN FURTHER NORTH ON SUNDAY INTO MUCH
OF SOUTHERN OREGON. IF MODEL CONSISTENCY CONTINUES WITH THE
PROGRESSION OF MOISTURE...WE WILL PROBABLY INCREASE THUNDERSTORM
CHANCES MORE ON SATURDAY AND SUNDAY. OF NOTE ARE THE HIGH
PRECIPITABLE WATER VALUES BY SATURDAY AND SUNDAY...REACHING 1.3
INCHES IN WESTERN SISKIYOU COUNTY ON SUNDAY...THAT SUGGEST HEAVY
RAIN MAY ACCOMPANY STORMS THIS WEEKEND.

OPERATIONAL AND ENSEMBLE MODEL GUIDANCE SHOW A SIGNIFICANT TREND
TOWARDS NORMAL TEMPERATURES BEGINNING ON SUNDAY AS TEMPERATURES DIP
BELOW THE CENTURY MARK FOR WEST SIDE VALLEYS. THE LATEST MEX
GUIDANCE FOR MEDFORD ACTUALLY SHOWS NORMAL TEMPERATURES (86 FOR A
HIGH) NEXT WEDNESDAY. THE EC IS NOT AS ROBUST WITH THE COOLING
TREND...BUT ALSO SHOWS TEMPERATURES DECREASING. LOOKING AT THE
500MB GFS ENSEMBLE PLOT FOR WEDNESDAY...THE UPPER RIDGE SHIFTS TO NEW
MEXICO AND WEST TEXAS...WITH SOME UPPER TROUGHING MOVING INTO THE
FORECAST AREA. THIS GIVES US AT LEAST MODERATE CONFIDENCE THAT
WE`RE IN FOR CLOSER-TO-NORMAL TEMPERATURES BY THE MIDDLE OF NEXT
WEEK.


&&

.AVIATION...FOR THE 01/12Z TAF CYCLE...ALONG THE COAST...IFR CIGS
NORTH OF CAPE BLANCO AND ALONG THE SOUTH COAST NEAR BROOKINGS WILL
CLEAR TO VFR BY THIS AFTERNOON...BUT THE LOWER CIGS WILL REMAIN OVER
THE COASTAL WATERS.  THE LOWER CONDITIONS WILL RETURN TO THE SAME
AREAS LATE THIS AFTERNOON AND PERSIST THROUGH TONIGHT. OVER THE
REMAINDER OF THE AREA...VFR CONDITIONS WILL PREVAIL...BUT ISOLATED
AFTERNOON AND EVENING THUNDERSTORMS MAY DEVELOP OVER THE CASCADES
AND SISKIYOU COUNTY.

&&

.MARINE...UPDATED 200 AM PDT WEDNESDAY 1 JULY 2015...A STRONG
THERMAL TROUGH NEAR THE COAST WILL WEAKEN SLIGHTLY INTO
THURSDAY...BUT WILL PERSIST INTO THE WEEKEND. THE STRONGEST WINDS
AND STEEPEST SEAS WILL OCCUR SOUTH OF GOLD BEACH AND BEYOND 10 NM
OFFSHORE...WHERE GALE FORCE NORTHERLIES AND VERY STEEP SEAS WILL
PREVAIL THROUGH WEDNESDAY EVENING.


&&

.CLIMATE...THE PAST RECORD FOR WARMEST JUNE IN MEDFORD WAS
DESTROYED BY 4 DEGREES. CONSIDERING THAT ONLY ONE DEGREE SEPARATES
THE TENTH WARMEST JUNE AND THE SECOND WARMEST JUNE SINCE 1911...4
DEGREES IS AMAZING. 21 DAYS REACHED 90 DEGREES OR GREATER IN JUNE
2015...WITH 5 100-DEGREE DAYS AND 6 DAILY RECORDS
BROKEN...INCLUDING THE ALL-TIME HIGHEST OVERNIGHT LOW TEMPERATURE
OF 76 DEGREES. AT LEAST 8 OTHER LOCATIONS IN SOUTHERN OREGON AND
NORTHERN CALIFORNIA RECORDED THE HOTTEST JUNE ON RECORD.


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...HEAT ADVISORY FROM 1 PM THIS AFTERNOON TO 11 PM PDT FRIDAY FOR
     ORZ023.
     HEAT ADVISORY FROM 1 PM THIS AFTERNOON TO 11 PM PDT FRIDAY FOR
     ORZ024-026.

CA...HEAT ADVISORY FROM 1 PM THIS AFTERNOON TO 11 PM PDT FRIDAY FOR
     CAZ080-081.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM PDT FRIDAY FOR
     PZZ350-356-370.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT FRIDAY
     FOR PZZ350-356-370.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 AM PDT SATURDAY FOR
     PZZ376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 AM PDT SATURDAY
     FOR PZZ376.
     GALE WARNING UNTIL 11 PM PDT THIS EVENING FOR PZZ376.
     HAZARDOUS SEAS WARNING UNTIL 11 PM PDT THIS EVENING FOR PZZ376.

$$

NSK/NSK/MAS


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