Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 282005
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
105 PM PDT THU MAY 28 2015

.DISCUSSION...28/00Z NAM/GFS IN.

LOTS OF STRATUS PERSISTS ALONG THE COAST THIS AFTERNOON...AND SOME
CUMULUS IS POPPING OVER THE RIDGES. NO SHOWERS OR THUNDERSTORMS
YET.

A REX BLOCK REMAINS IN PLACE OFFSHORE WITH THE RIDGE ALONG THE
ALASKA/CANADA BOUNDARY AND THE LOW NEAR 40N 150W. THERE IS ANOTHER
WEAKER LOW OVER THE ALASKA PANHANDLE. HOWEVER...THE END IS IN
SIGHT. LOWS WILL BEGIN UNDERCUTTING THE RIDGE SATURDAY.

UNTIL THEN...A WEAKER UPPER LEVEL RIDGE WILL REMAIN IN PLACE ALONG
THE WEST COAST WITH NEARLY ZONAL FLOW ALOFT. THERE WILL BE
ISOLATED SURFACE HEATING DRIVEN THUNDERSTORM ACTIVITY IN THE
AFTERNOONS AND EVENINGS...MOSTLY OVER HIGHER TERRAIN. INLAND HIGH
TEMPERATURES WILL BE 10 TO 15 DEGREES ABOVE NORMAL OVER THE WEST
SIDE AND 5 TO 10 DEGREES ABOVE NORMAL EAST OF THE CASCADES
THROUGH SATURDAY.

THE PATTERN WILL CHANGE SUNDAY AS THE FIRST AND STRONGEST OF
SEVERAL TROUGHS UNDERCUTTING THE RIDGE ARRIVES. THIS WILL BRING
SOUTH TO SOUTHWEST FLOW ALOFT TO THE AREA. A STRONG SHORT WAVE
ROUNDING THE BOTTOM OF THE TROUGH WILL MOVE ONSHORE SUNDAY
AFTERNOON AND EVENING. THE COOLING ALOFT AND SHORT WAVE ACTIVITY
WILL ENHANCE THE POTENTIAL FOR CONVECTION...BUT IT WILL ALSO BE
QUITE A BIT COOLER AT THE SURFACE WITH THE INCREASED CLOUD COVER.
SHOWER ACTIVITY WILL BE A GIVEN. AT THIS TIME MODEL LIFTED INDICES
AND SOUNDINGS INDICATE THE BEST CHANCE OF THUNDERSTORMS SUNDAY
AFTERNOON WILL BE OVER WESTERN SISKIYOU COUNTY...THE SISKIYOUS AND
THE CASCADES. THE BEST AREA WILL MIGRATE A BIT TO THE EAST SUNDAY
EVENING.

THE OTHER CONCERN WITH THE SUNDAY SYSTEM IS WIND. IT WILL GET
QUITE BREEZY OVER THE RIDGES AND EAST OF THE CASCADES...BUT NOT AS
MUCH IN THE SHASTA VALLEY...AS THE GRADIENTS WILL BE PRETTY WEAK.

&&

.AVIATION...FOR THE 28/18Z TAF ISSUANCE...AREAS OF STRATUS WITH
IFR TO LIFR CIGS WILL PERSIST ALONG THE IMMEDIATE COASTLINE THIS
AFTERNOON THEN BECOME WIDESPREAD ALONG THE COAST AND INTO THE
COASTAL VALLEYS WITH LIFR/IFR CIGS AND MVFR/IFR VISIBILITIES THIS
EVENING THROUGH FRIDAY MORNING. AREAS OF MVFR ARE EXPECTED TO
SPREAD INTO THE UMPQUA BASIN TO ABOUT ROSEBURG LATE TONIGHT AND
FRIDAY MORNING. ELSEWHERE, VFR CONDITIONS WILL CONTINUE THROUGH
THE TAF PERIOD. /CC

&&

.MARINE...UPDATED 1050 AM PDT THURSDAY 28 MAY 2015...LIGHT TO
MODERATE NORTH WINDS WILL PERSIST OVER THE WATERS THROUGH
SATURDAY...WHILE STEEP CHOPPY SEAS ARE EXPECTED ONLY THROUGH
TONIGHT. WILL THEREFORE KEEP A SMALL CRAFT ADVISORY FOR STEEP SEAS
IN PLACE OVER PORTIONS OF THE SOUTHERN WATERS THROUGH THAT TIME. LOW
PRESSURE WILL MOVE INTO THE AREA SUNDAY AND MONDAY, BRINGING SHOWERS
WITH LIGHT AND VARIABLE WINDS. WINDS WILL SWITCH TO SOUTH TO
SOUTHWEST AT TIMES SUNDAY AFTERNOON THROUGH MONDAY...THEN WILL
RETURN TO A LIGHT WEST FLOW TUESDAY...BECOMING NORTH TO NORTHWEST
TUESDAY NIGHT.  WINDS AND SEAS WILL THEN REMAIN RELATIVELY CALM
THROUGH TUESDAY. THEN NORTH WINDS MAY INCREASE TO SMALL CRAFT
LEVELS, MAINLY SOUTH OF CAPE BLANCO, ON WEDNESDAY AND THURSDAY WITH
A THERMAL TROUGH BUILDING ALONG THE COAST.  /CC

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS
        UNTIL 11 PM PDT THIS EVENING FOR PZZ356-376.

$$

15/02/14


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