Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 202117
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
217 PM PDT SAT SEP 20 2014

.DISCUSSION...A SIGNIFICANT CHANGE IS COMING TO THIS AREAS WEATHER
BY MIDWEEK. AN UPPER LEVEL CLOSED LOW OVER THE CENTRAL CALIFORNIA
COAST WILL GET EJECTED TO THE NORTHEAST AS A DEEP GULF OF ALASKA
LOW APPROACHES. WHEN THIS CLOSED LOW KICKS OUT...IT WILL ROTATE A
LITTLE BIT OF MOISTURE TO AREAS EAST OF THE CASCADES. THIS WILL
BRING A SLIGHT CHANCE OF THUNDERSTORMS SUNDAY AFTERNOON TO HIGHER
TERRAIN FROM CASCADES EASTWARD. GOING INTO MONDAY...THE CLOSED LOW
IS OUT OF THE PICTURE WITH WEAK HIGH PRESSURE RIDGING OVER THE
AREA. A WEAK COLD FRONT WILL PUSH INTO THIS RIDGE AND FALL APART
NOT AFFECTING THE AREA.

THE GULF OF ALASKA LOW APPROACHES THE COAST TUESDAY NIGHT INTO
WEDNESDAY. WINDS WILL INCREASE ACROSS THE AREA TUESDAY ESPECIALLY ON
THE RIDGES OF NORTHERN CALIFORNIA AND EAST OF THE CASCADES. THERE IS
A SLIGHT TIMING DIFFERENCE BETWEEN THE GFS AND EURO MODELS WITH THE
ASSOCIATED COLD FRONT. THE EURO BRINGS THE FRONT TO THE COAST AROUND
MIDNIGHT TUESDAY NIGHT WHILE THE GFS MAKES LANDFALL AT SUNRISE
WEDNESDAY. CURRENT FORECAST TIMING LEANS TO THE EURO SOLUTION. THE
ENSEMBLE MEMBERS FROM BOTH THE EURO AND GFS FOR WEDNESDAY HAVE A
SMALL SPREAD WHICH MEANS THAT BOTH ARE RATHER CONFIDENT IN THEIR
SOLUTIONS...SO I HAVE NO COMPLELLING REASON MAKE A CHANGE AT THIS TIME.

AFTER THE FRONT PASSES OVER...A LARGE POOL OF COOL UNSTABLE AIR WILL
COVER THE AREA. HIGH TEMPERATURES WILL DROP FROM 15 DEGREES ABOVE
NORMAL TODAY TO 15 DEGREES BELOW NORMAL BY THURSDAY. WIDESPREAD
FROST/FREEZE CAN BE EXPECTED EAST OF THE CASCADES. JBL

&&

.AVIATION...BASED ON THE 20/18Z TAF CYCLE...ALONG THE COAST...A
SOUTHERLY SURGE OF IFR CIGS/VSBYS WILL CONTINUE TO MOVE UP THE COAST
LATE IN THE AFTERNOON THEN SPREADING TO ALL OF THE SOUTHERN OREGON
COAST AND INTO THE COASTAL VALLEYS INCLUDING THE NORTHWEST PORTION
OF THE UMPQUA VALLEY THIS EVENING AND PERSISTING INTO SUNDAY MORNING
WITH CONDITIONS BEGINNING TO IMPROVE AFTER 16Z SUNDAY. HOWEVER, IFR
WILL PERSIST IN AREAS AT THE IMMEDIATE COAST INTO SUNDAY AFTERNOON.
INLAND...VFR CONDITIONS WILL PREVAIL THROUGH SUNDAY MORNING...EXCEPT
FOR LOCAL MVFR VSBYS IN SMOKE NEAR WILDFIRES IN JOSEPHINE COUNTY AND
THE WESTERN PORTION OF SISKIYOU COUNTY. /SVEN

&&

.MARINE...UPDATED 300 PM PDT SAT 20 SEP 2014...NORTHERLY WINDS WILL
BECOME SOUTHERLY FROM SOUTH  TO NORTH THROUGH THIS EVENING, AS THE
THERMAL TROUGH WEAKENS AND HIGH PRESSURE BUILDS INTO THE AREA. WIND
WAVES HAVE DIMINISHED TODAY, BUT MODERATE NORTHWEST SWELL HAS KEPT
SEAS AT JUST BELOW 10 FEET. WINDS AND SEAS WILL DIMINISH TONIGHT
THROUGH MONDAY NIGHT, AND BEGINNING TUESDAY, A SERIES OF FRONTS WILL
BEGIN TO IMPACT THE AREA WITH INCREASED WINDS AND STEEP TO VERY
STEEP HEAVY SEAS TROUGH THE REST OF THE WEEK. -BPN

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...NONE.

$$







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