Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 031559
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
859 AM PDT THU SEP 3 2015

.DISCUSSION...THE LATEST VISIBLE IMAGE SHOWS A BAND OF CLOUDS
MOVING SOUTHWEST TO NORTHEAST IN SOUTHEAST KLAMATH, LAKE EASTERN
SISKIYOU AND MOST OF MODOC COUNTY. A FEW RAWS SITES IN THESE
LOCATIONS PICKED UP LIGHT RAINFALL WITH ANYWHERE BETWEEN 0.01 AND
0.10 OF AN INCH BETWEEN LAST NIGHT AND THIS MORNING. THE RADAR
IMAGE IS NOT SHOWING ANYTHING BECAUSE THE RAIN IS OCCURRING AT
LOWER LEVELS WHICH IS NOT BEING PICKED UP. MEANWHILE A ISOLATED
SHOWERS IN ASSOCIATION WITH A WEAK SHORTWAVE TROUGH WITHIN THE
MUCH LARGER UPPER LOW IS MOVING INLAND JUST NORTH OF OUR FORECAST
AREA. THESE ISOLATED SHOWERS SHOULD REMAIN TO OUR NORTH TODAY.

THE UPPER LOW WILL MOVE SOUTH TONIGHT AND MORE SHORTWAVE ENERGY
WILL ROTATE AROUND THE UPPER LOW WITH THE FIRST IN A SERIES
EXPECTED TO SWING INTO NORTHWEST CAL EARLY FRIDAY MORNING. COLD
AIR ALOFT WITH 500MB TEMPERATURES NEAR -23C WILL OVER THE MARINE
WATERS LATE TONIGHT SO COULD NOT RULE OUT AN ISOLATED THUNDERSTORM
OR TWO.

FRIDAY WILL BE THE MOST ACTIVE DAY IN THE PERIOD AS THE UPPER LOW
AND COLD AIR ALOFT MOVES OVERHEAD WITH SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS. IT`S POSSIBLE WE COULD HAVE MORE
THUNDERSTORM ACTIVITY FRIDAY AFTERNOON EAST OF THE CASCADES. IT`S
ALSO POSSIBLE SOME THUNDERSTORMS COULD PRODUCE GUSTY WINDS AND
SMALL HAIL. -PETRUCELLI

&&

.AVIATION...FOR THE 03/12Z TAF CYCLE...CONDITIONS WILL BE VFR
THROUGH THIS EVENING THEN ONSHORE FLOW WILL BRING MAINLY VFR CIGS
BUT LOCAL MVFR CIGS WITH MOUNTAIN OBSCURATION INTO SOUTHWEST OREGON
LATE TONIGHT INTO FRIDAY MORNING. /DW

&&

.MARINE...UPDATED 500 AM PDT THURSDAY 3 SEPTEMBER 2015...SMALL CRAFT
ADVISORY LEVEL NORTH WINDS AT THE LOW END OF CRITERIA WILL DEVELOP
SOUTH OF GOLD BEACH BEYOND 5 NM FROM SHORE LATE THIS MORNING. THESE
WINDS WILL REACH A PEAK IN THE EARLY EVENING THEN DIMINISH OVERNIGHT
BEFORE RETURNING TO ABOUT THE SAME STRENGTH FOR LATE FRIDAY MORNING
THROUGH FRIDAY EVENING. AFTER ANOTHER DECREASE IN WINDS LATE FRIDAY
NIGHT, WINDS WILL BECOME STRONGER DURING THE WEEKEND. WINDS WILL
STILL BE MODERATE SATURDAY BUT GALES ARE POSSIBLE IN THE SOUTHERN
OUTER WATERS WITH SMALL CRAFT WINDS ELSEWHERE SUNDAY INTO MONDAY.
WINDS ARE EXPECTED TO RETURN TO MODERATE STRENGTH BEYOND
MONDAY. /DW

&&

.PREV DISCUSSION... /ISSUED 351 AM PDT THU SEP 3 2015/

DISCUSSION...A COLD FRONT THAT MOVED THROUGH LATE WEDNESDAY HAS
LEFT MOST OF THE AREA 5 TO 10 DEGREES COOLER VERSUS THIS TIME VERSUS
YESTERDAY. EVENING SHIFT PUT UP A FROST ADVISORY FOR SOME OF THE
EAST SIDE. THE DAY SHIFT TODAY WILL NEED TO CONSIDER THE SAME FOR
TONIGHT AND FRIDAY NIGHT AS THE CENTER OF AN UNUSUALLY COLD UPPER
LOW DIVES IN OVERHEAD. THIS LOW WILL BRING THE COOLEST AIR OF THE
SEASON WITH A COLD CORE OF -25C AT 500 MILLIBARS. AS THE TROUGH
SWINGS EASTWARD AND SKIES CLEAR SATURDAY NIGHT INTO SUNDAY...
THERE WILL BE A THREAT FOR FREEZING MORNING TEMPERATURES ACROSS
MUCH OF THE LOWLANDS EAST OF THE CASCADES. A SPECIAL WEATHER
STATEMENT WILL COVER THIS UPCOMING POTENTIAL FOR FROST AND FREEZE
FOR AGRICULTURAL INTERESTS.

RAIN WITH THIS SYSTEM TODAY SHOULD REMAIN FAIRLY SLIM. THE 88D IS
CURRENTLY SHOWING SOME WEAK ECHOES STREAMING SOUTHWEST TO
NORTHEAST BETWEEN KLAMATH FALLS AND LAKEVIEW IN REGION OF COLDER
CLOUD TOPS BETWEEN -10 TO -15C IN THICKER CLOUD. PER THE RUC AND
HRRR FORECASTS, WE DID BUMP UP PROBABILITIES A BIT FOR A HUNDREDTH
OR TWO OUR THERE AROUND SOUTHERN LAKE COUNTY WITH SHORT WAVE
ENERGY OVERRIDING THE SLOWLY PROGRESSING FRONTAL ZONE. THIS SHOULD
TAPER OFF THIS EVENING WITH A FAIRLY UNEVENTFUL NIGHT IN STORE.

ACTIVITY WILL INCREASE FRIDAY WITH THE APPROACH OF THE DEEP UPPER
LOW FROM THE NORTH. FAIRLY STRONG SHORT WAVE ENERGY IS FORECAST TO
DIG THROUGH THE BASE OF THE TROUGH OVER SOUTHERN OREGON AND NORTHERN
CALIFORNIA FRIDAY AFTERNOON AND EVENING. WITH THE COLD AIR ALOFT,
NUMEROUS SHOWERS AND A SLIGHT CHANCE FOR THUNDERSTORMS WITH SOME
LOCALIZED MODERATE RAINS ARE IN STORE. THE BEST SHOT AT GOOD RAIN
WILL BE EAST OF THE CASCADES. DUE TO BUILDING CONFIDENCE BASED ON
SUPPORT FROM RECENT MODEL RUNS, HAVE ALSO BUMPED UP POPS A BIT
MORE IN THIS TIME FRAME.

SHOWERS WILL BE LINGERING INTO SATURDAY MORNING MAINLY FROM THE
CASCADES EAST. SNOW LEVELS EARLY SATURDAY SHOULD BOTTOM OUT BETWEEN
6000 AND 6500 FEET OVER THE CASCADES, AND MORE LIKE 7KFT IN
NORTHERN CALIFORNIA. SO, A LITTLE DUSTING ON THE HIGHER TERRAIN
LOOKS LIKELY. SOME UNCERTAINTY EXISTS FOR AREAS IN LAKE COUNTY
WHERE THE MORE SIGNIFICANT PRECIP WILL FALL. THE WARNERS INCLUDING
HART MTN AREA ABOVE 6500 FEET SHOULD BE AWARE OF THE POTENTIAL FOR
A LITTLE MORE SNOW THERE.

AS THE SYSTEM CLEARS OUT SATURDAY AFTERNOON AND NIGHT, THIS WILL
LEAVE SUNDAY MORNING WITH A FAIR POTENTIAL TO FREEZE IN MANY AREAS
OF WHAT LOOKS LIKE MAINLY LAKE AND MODOC COUNTIES. A WARMING TREND
LOOKS LIKELY THEREAFTER THROUGH LATE WEEK. STAVISH


&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 11 PM PDT THIS EVENING FOR
     PZZ356-376.
     SMALL CRAFT ADVISORY FROM 11 AM TO 11 PM PDT FRIDAY FOR PZZ376.

$$


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