Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 010115
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
615 PM PDT MON AUG 31 2015

.DISCUSSION...IT HAS BEEN AN EARLY FALL-LIKE DAY HERE IN THE
MEDFORD FORECAST AREA. BELOW NORMAL TEMPERATURES AND CLEAR SKIES
STAND IN STARK CONTRAST TO JUST A WEEK AGO, WHEN SMOKE COVERED
MUCH OF THE REGION AND HIGH TEMPERATURES WERE WELL ABOVE NORMAL.
SYNOPTIC MODELS DEPICT A PATTERN OF COOLER TEMPERATURES AND
INCREASED RAIN CHANCES, PERIODICALLY INTERRUPTED BY MORE SEASONAL
AND DRY CONDITIONS, CONTINUING THROUGH AT LEAST THE FIRST HALF OF
SEPTEMBER.

BROAD UPPER LEVEL CYCLONIC FLOW CONTINUES OVER THE PACIFIC
NORTHWEST, BUT AT THE SURFACE, HIGH PRESSURE IS ALLOWING
TEMPERATURES TO RISE TOWARDS, BUT NOT QUITE TO, MORE SEASONAL
VALUES. A WEAK SHORTWAVE WITHIN THE FLOW ALOFT WILL PRODUCE ONSHORE
FLOW TONIGHT INTO TOMORROW MORNING, AND THIS WILL HELP GIVE THE
MARINE LAYER A PUSH INLAND. EXPECT FOG/LOW CLOUDS ALONG THE COAST
AND INTO THE COASTAL VALLEYS AND UMPQUA BASIN, WITH A CHANCE FOR
SOME LIGHT DRIZZLE WHERE THE TERRAIN PROVIDES FOR MORE VERTICAL
MOTION. THE COOLER AIR EAST OF THE CASCADES COULD ALSO BRING A SHORT
PERIOD OF FROST TO THE CHEMULT, CRESCENT, AND BEATTY AREAS, BUT WE
ARE WELL PAST THE AVERAGE DATE OF FIRST FREEZE, SO NO HEADLINES WILL
BE ISSUED.

A SECOND MORE POTENT WAVE WILL MOVE ONSHORE TUESDAY AFTERNOON INTO
TUESDAY NIGHT AS THE PARENT TROUGH DIGS SOUTH ALONG THE COASTLINE.
THIS COULD BRING SHOWERS TOT HE COAST BY TUESDAY AFTERNOON. MODELS
HAVE BACKED OFF A BIT ON TIMING AND STRENGTH, SO HAVE ADJUSTED THE
FORECAST IN TURN, BRINGING THE BULK OF MOISTURE INTO THE AREA EARLY
WEDNESDAY MORNING. MOST RAINFALL SHOULD OCCUR ALONG AND WEST OF THE
CASCADES THROUGH WEDNESDAY AFTERNOON, BUT A STRAY SHOWER OR TWO MAY
MAKE IT TO THE EAST SIDE. RAINFALL AMOUNTS SHOULD BE LIGHT.

ANOTHER SHORTWAVE WILL PASS THROUGH THE AREA THURSDAY AS IT
CIRCULATES AROUND THE UPPER LEVEL LOW TO OUR NORTH. THERE APPEARS TO
BE A GENERAL LACK OF MOISTURE WITH THIS WAVE, BUT IT WILL PROVIDE
ENOUGH ENERGY TO PRODUCE A CHANCE OF SHOWERS OVER PORTIONS OF THE
AREA, BUT IN PARTICULAR, OVER THE EAST SIDE. THE TROUGH WILL THEN
RESIDE OVER THE REGION THROUGH THE WEEKEND, FINALLY SHIFTING TO THE
EAST LATE SATURDAY INTO SUNDAY MORNING. UNTIL THEN, EXPECT
TEMPERATURES WELL BELOW NORMAL, AND AN ONGOING CHANCE OF SHOWERS.
THIS SYSTEM WILL ALSO BRING THE COLDEST TEMPERATURES SINCE THE
BEGINNING OF SUMMER, AND THERE IS THE POTENTIAL THAT FROST/FREEZE
HEADLINES MAY BE NEEDED FOR THE AGRICULTURAL INTERESTS EAST OF THE
CASCADES AND IN NORTHERN CALIFORNIA, AND THERE MAY EVEN BE SOME
LIGHT SNOWFALL OVER THE HIGHER PEAKS OF THE CASCADES AND THE EAST
SIDE.

EARLY NEXT WEEK, MODELS ARE STILL PRODUCE A SHORT PERIOD OF RIDGING
ALOFT AND THE RETURN OF THE THERMAL TROUGH AT THE SURFACE, RESULTING
IN DRY AND MORE SEASONAL TEMPERATURES SUNDAY AND MONDAY. AGAIN, THIS
WILL BE SHORT LIVED, AS SEVERAL MORE TROUGHS LIE IN WAIT UPSTREAM IN
THE WESTERLIES, AND THESE SHOULD MAKE THEIR WAY INTO THE AREA LATER
NEXT WEEK. -BPN


&&

.AVIATION...FOR THE 01/00Z TAF CYCLE...VFR CONDITIONS ARE EXPECTED
THROUGH THE TAF PERIOD, EXCEPT ALONG AND NEAR THE COAST AND IN THE
UMPQUA BASIN WHERE MVFR AND IFR CONDITIONS ARE EXPECTED TO DEVELOP
OVERNIGHT. EXPECT MVFR ALONG AND NEAR THE COAST IN THE AFTERNOON AND
VFR ELSEWHERE. PARTIAL TERRAIN OBSCURATIONS WILL OCCUR ON THE COAST
RANGE AND UMPQUA DIVIDE TONIGHT THROUGH TUESDAY. BTL

&&

.MARINE...UPDATED 230 PM PDT MONDAY, AUGUST 31ST, 2015... TODAY INTO
TUESDAY WINDS WILL REMAIN FAIRLY LIGHT WITH MODERATE SEAS DOMINATED
BY WEST SWELL. THESE SEAS WILL BE VERY NEAR ADVISORY LEVELS THROUGH
THIS EVENING NORTH OF CAPE BLANCO, LIKELY AROUND 9 FEET AT A
DOMINANT PERIOD OF 11 SECONDS. A COLD FRONT WILL MOVE THROUGH LATE
TUESDAY BRINGING RAIN SHOWERS THAT ARE LIKELY TO LINGER INTO
WEDNESDAY AS WELL AS A BIT OF AN INCREASE IN NORTHWEST SWELL. NORTH
WIND AND SEAS MAY INCREASE AS EARLY AS THURSDAY OR AS LATE AS THIS
WEEKEND. NUMERICAL MODELS HAVE BEEN UNCERTAIN ON THE TIMING AND
MAGNITUDE OF THIS NORTH WIND INCREASE. AT THIS POINT, WHILE SMALL
CRAFT ADVISORY WINDS ARE POSSIBLE IN THE THURSDAY THROUGH SATURDAY
TIME FRAME, THEY ARE MORE LIKELY ON SUNDAY. GALES HAVE BEEN
INDICATED FOR AREAS SOUTH OF CAPE BLANCO FOR SUNDAY AFTERNOON AND
EVENING. BTL

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

CA...NONE.

PACIFIC COASTAL WATERS...NONE.

$$

BPN/TRW/BTL


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