Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 290956
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
256 AM PDT FRI MAY 29 2015

.DISCUSSION...THUNDERSTORM ACTIVITY SHOULD PICK UP SIGNIFICANTLY
AS CONTINUED SOUTHERLY LOW LEVEL FLOW CONTINUES TO FEED MOISTURE
INTO THE REGION. INSTABILITY SHOULD BE OVER MOST OF THE ARE AS
FAR WEST AS THE EASTERN FRINGES OF THE COASTAL RANGE THIS
AFTERNOON WITH A WEAK SHORT WAVE MOVING THROUGH AROUND MAX
HEATING. WITH GOOD 850 THETA E CONVERGANCE EXTENDING FROM WESTERN
SISKIYOU COUNTY UP THE EAST SIDE JUST EAST OF THE CASCADES AND
DOWN SOUTHEASTWARD INTO SOUTHERN LAKE COUNTY THIS SHOULD BE THE
AREA OF BEST POSSIBLE THUNDERSTORM DEVELOPMENT ACCORDING TO THE
MODELS. HOWEVER...WITH THE WEAK SHORTWAVE MOVING OVER THE CASCADES
NEARING MAX HEATING WHEN THE UPVALLEY FLOW SHOULD BE FIRST
REACHING THE CASCADES AROUND THE SAME TIME HAVE INCLUDED THE
WESTERN CASCADE FOOTHILLS IN THE AREA OF POSSIBLE THUNDERSTORM
DEVELOPMENT. THIS PATTERN REPEATS ON SATURDAY WITH INCREASED
NUMBER OF STRONGER SHORTWAVES CYCLING THROUGH...BUT WILL LEAVE THE
CHANCES TO SLIGHT CHANCE OF THUNDERSTORMS AT THIS TIME. A CHANGE
IN THE PATTERN FINALLY MOVES IN SUNDAY AS A COLD FRONT APPROACHES
THE COAST. SOUTHERLY FLOW INCREASES CONSIDERABLY AHEAD OF THIS
SYSTEM WITH VERY STRONG 850 CONVERGANCE INDICATED OVER THE WEST
SIDE AS THE FRONT MOVES INLAND THROUGH THE DAY. THIS MOVES TO THE
CASCADES AND EAST SIDE INTO THE EVENING...BUT THERE IS GOOD
UNCERTAINTY TO THE AMOUNT OF INSTABILITY AS THE TIMING OF THE
SYSTEM COULD EITHER ALLOW FOR GOOD SURFACE HEATING WITH THE
CURRENT INDICATED TIMING...OR LOW INSTABILITY IF THE TIMING IS
SOONER WITH EARLY CLOUD COVER INHIBITING HEATING. SVEN

&&

.AVIATION...FOR THE 29/06Z...
LOW CLOUDS AND FOG ALONG AND NEAR THE COAST WILL BE IN THE IFR TO
LIFR RANGE TONIGHT THROUGH FRIDAY MORNING, IMPROVING TO A MIX OF IFR
AND MVFR FRIDAY AFTERNOON. WHILE MVFR CLOUDS COULD MAKE IT INTO THE
WESTERN UMPQUA BASIN AFTER 12Z, SUSPECT THESE WILL GET HUNG UP IN
THE COAST RANGE AND WEST OF ROSEBURG. FRIDAY AFTERNOON AND EVENING A
LOW PRESSURE IMPULSE WILL RESULT IN CONVECTIVE CLOUDINESS FROM THE
SISKIYOUS AND MARBLE MOUNTAINS NORTHEASTWARD WITH A POSSIBILITY OF
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ALONG AND NEAR THESE
MOUNTAINS, THE CASCADES, AND INTO NORTHERN KLAMATH AND LAKE
COUNTIES. THE RISK OF THUNDERSTORMS WILL BE GREATEST FROM THE
CASCADES EASTWARD. THESE STORMS COULD HAVE SMALL HAIL AND MODERATELY
GUSTY OUTFLOWS. VALLEY CLOUD CONDITIONS SHOULD BE MOSTLY VFR.
PARTIAL TERRAIN OBSCURATIONS ARE POSSIBLE WITH SHOWERS AND STORMS
FRIDAY AFTERNOON AND EVENING WITH ISOLATED MVFR VISIBILITIES IN RAIN
IN THE NEARBY VALLEYS. BTL

&&

.MARINE...UPDATED 830 PM PDT, THURSDAY, 28 MAY 2015... BOTH SWELL
AND WIND WAVE WILL SUBSIDE TONIGHT. RELATIVELY LIGHT SEAS ARE
EXPECTED THROUGH MID NEXT WEEK. LIGHT NORTH WINDS WILL PERSIST
THROUGH SATURDAY. WEAK LOW PRESSURE WILL MOVE INTO THE WATERS SUNDAY
AND MONDAY BRINGING VARIABLE WINDS AND SHOWERS. A THERMAL TROUGH IS
EXPECTED TO REDEVELOP LATER NEXT WEEK AND MAY BRING MODERATE NORTH
WINDS AND WIND DRIVEN SEAS BACK TO THE AREA. BTL/WRIGHT

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...NONE.

$$

SBN/SBN/SBN


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