Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 280347
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
847 PM PDT WED MAY 27 2015

.UPDATE...
AN UPDATE HAS BEEN SENT TO REMOVE THE THREAT OF THUNDERSTORMS FOR
THE REST OF THE EVENING. A SLIGHT CHANCE OF SHOWERS HAS BEEN LEFT
IN THROUGH 11PM PDT TO ACCOUNT FOR BUILD-UPS AND RADAR RETURNS
WEST OF SUMMER LAKE, OREGON AND OVER AND AROUND DAY, CALIFORNIA.
BTL

&&

.DISCUSSION...
NO LIGHTNING TODAY. JUST SOME CUMULUS BUILDUPS ACROSS MAINLY
PORTIONS OF THE EAST SIDE AND NORTHERN CALIFORNIA. PER RADAR,
SUSPECT THERE WERE SOME SHOWERS THIS AFTERNOON AND EVENING FROM
ABOUT MEDICINE LAKE TO DAY AND IN THE AREA BURNED LAST SUMMER BY
THE DAY FIRE. IT WILL BE A QUIET EVENING AND OVERNIGHT, WITH JUST
SOME STRATUS AND FOG TO KEEP AN EYE ON ALONG AND NEAR THE COAST.

THE WARMEST TEMPERATURES OF THE SPRING, THUS FAR, ARE EXPECTED
FRIDAY AND SATURDAY. SHOWERS AND THUNDERSTORMS ARE LIKELY TO BRING
WETTING RAINFALL TO MUCH OF THE AREA IN THE FRIDAY THROUGH MONDAY
TIME FRAME, WITH A COOL DOWN TO BELOW NORMAL TEMPERATURES EARLY
NEXT WEEK. BTL

&&

.AVIATION...FOR THE 28/00Z...STRATUS WITH IFR CIGS WILL PERSIST
ALONG THE IMMEDIATE COASTLINE NORTH OF CAPE BLANCO AND SOUTH OF GOLD
BEACH TONIGHT INTO AT LEAST THURSDAY MORNING. THE FLOW BECOMES EVEN
MORE ONSHORE LATER THURSDAY, SO STRATUS MAY NOT BREAK AT ALL IN
THESE LOCATIONS. ELSEWHERE, VFR CONDITIONS WILL CONTINUE FOR THE
NEXT 24 HOURS. -WRIGHT

&&

.MARINE...UPDATED 830 PM PDT, TUESDAY MAY 17, 2015...THE GENERAL
PATTERN OF OFFSHORE HIGH PRESSURE AND LOW PRESSURE OVER LAND WILL
CONTINUE THROUGH SATURDAY RESULTING IN PERSISTENT NORTH WINDS OVER
THE WATERS. PRESSURE GRADIENTS WILL WEAKEN THIS EVENING ALLOWING
WIND SPEEDS TO LOWER AND REMAIN RELATIVELY LIGHT THROUGH SATURDAY.
SEAS WILL TAKE A BIT LONGER TO COME DOWN, THUS SMALL CRAFT
ADVISORIES FOR CHOPPY SEAS REMAIN IN EFFECT THROUGH THURSDAY
EVENING. LOW PRESSURE WILL MOVE INTO THE WATERS SUNDAY INTO EARLY
NEXT WEEK. WINDS AND SEAS WILL REMAIN LIGHT, BUT SHOWERS CAN BE
EXPECTED. BTL/WRIGHT

&&

PREV DISCUSSION... /ISSUED 254 PM PDT WED MAY 27 2015/

DISCUSSION...VISIBLE SATELLITE SHOWS THE COASTAL STRATUS HUGGING
THE COAST AND CUMULUS BUBBLING UP OVER THE HIGHER TERRAIN WHILE
THE REST OF THE CWA REMAINS UNDER CLEAR SKIES. TEMPERATURES ARE
RUNNING ABOUT 5 TO 10 DEGREES WARMER THAN THIS TIME YESTERDAY.
THIS WARMING TREND WILL CONTINUE INTO THE WEEKEND WITH MANY AREAS
AWAY FROM THE IMMEDIATE COAST SEEING THE WARMEST TEMPERATURES OF
THE YEAR SO FAR. ASIDE FROM THE WARM TEMPERATURES, THERE WILL ALSO
BE A CHANCE OF THUNDERSTORMS IN THE AFTERNOONS, FIRST OVER THE
CASCADES THEN OVER THE SISKIYOUS AND PORTIONS OF THE EAST SIDE AS
INSTABILITY INCREASES THROUGH THE WEEK.

TEMPERATURES ON THURSDAY WILL FLIRT WITH THE 90 DEGREE MARK FOR THE
ROGUE VALLEY. INSTABILITY PARAMETERS LOOK MARGINAL AT BEST FOR
CONVECTION BUT STILL CAN`T RULE A THUNDERSTORM OR TWO OVER THE
CASCADES AND WESTERN SISKIYOU COUNTY. THE REST OF THE CWA SHOULD
SEE SUNNY SKIES WITH MAYBE SOME CUMULUS BUILDUPS AROUND ON THE
HIGHER TERRAIN AND COASTAL STRATUS WILL HUG THE COAST AGAIN.

THE WARMING TREND WILL PEAK ON FRIDAY AND SATURDAY AS THE RIDGE
ALOFT MOVES OVERHEAD. FORECASTED TEMPERATURES ARE IN THE LOW 90`S
FOR THE ROGUE VALLEY, UPPER 80`S TO LOW 90`S FOR NORTHERN
CALIFORNIA, AND UPPER 70`S TO LOW 80`S EAST OF THE CASCADES. THE
COAST WILL REMAIN NEAR NORMAL WITH THE MARINE LAYER AND COASTAL
STRATUS MODERATING TEMPERATURES THERE.

AS FAR AS THUNDERSTORMS GO, MODELS ARE CURRENTLY HIGHLIGHTING THE
SISKIYOUS AND THE CASCADES AS THE MOST FAVORABLE PLACES FOR
DEVELOPMENT ON FRIDAY. THE GFS INDICATES LI`S OF -4 TO -6 BUT LAPSE
RATES ARE MARGINAL AT 6.5 C/KM. THE QUESTION WILL BE MOISTURE AND
WILL THERE BE ENOUGH OF IT. CURRENTLY, MODELS ARE HIGHLIGHTING
BULLSEYES OF MID LEVEL MOISTURE IN THE SAME LOCATIONS AS THE BEST
INSTABILITY. THEREFORE, LEFT THE CHANCE OF THUNDERSTORMS IN THE
FORECAST. THE STEERING WINDS ALOFT ARE ABOUT 15 KT OUT OF THE
SOUTHWEST SO EXPECT ANY STORMS THAT DO DEVELOP TO MOVE IN A
NORTHEASTERLY DIRECTION. ANYTHING THAT DEVELOPS OVER THE SISKIYOUS
HAS THE POTENTIAL TO DRIFT OVER THE ROGUE VALLEY IF THE STORMS
HOLD UP.

EXPECT A REPEAT ON SATURDAY WITH THUNDERSTORMS AS INSTABILITY
PARAMETERS ABOUT THE SAME. MID LEVEL MOISTURE IS A BIT MORE
ABUNDANT AND LAPSE RATES ARE A BIT MORE STEEP SO THE CHANCE OF
THUNDERSTORMS EXPANDS IN COVERAGE. THE RIDGE SHIFTS EAST SATURDAY
NIGHT AND INSTABILITY CONTINUES TO INCREASE AS WE HEAD INTO THE
EXTENDED. -MND

LONG TERM...AS AN UPPER LOW APPROACHES THE COAST ON SUNDAY, EXPECT
AN INCREASE IN SHOWERS AND A CHANCE FOR THUNDERSTORMS OVER THE AREA,
ESPECIALLY FROM THE CASCADES WEST. EAST OF THE CASCADES,MODELS
INDICATE AN INCREASE IN SHOWER AND THUNDERSTORM CHANCES BY SUNDAY
EVENING AND INTO SUNDAY NIGHT. MODELS DIFFER SLIGHTLY IN THE TRACK
OF THE LOW AND HOW QUICKLY IT WILL PUSH INLAND. OVERALL THOUGH,
THERE IS AGREEMENT THAT THE LOW WILL PUSH INLAND ON MONDAY. AS IT
REMAINS CENTERED OVER THE AREA MONDAY, EXPECT MUCH COOLER
TEMPERATURES, WIDESPREAD SHOWERS OVER THE AREA AND A CHANCE FOR
THUNDERSTORMS FROM THE CASCADES EAST. A CHANCE FOR SHOWERS WILL
CONTINUE ON TUESDAY WITH THE LOW FORECAST TO GRADUALLY SHIFT EAST
OF THE AREA AROUND LATE TUESDAY AND TUESDAY NIGHT. A SLIGHT CHANCE
FOR THUNDERSTORMS IS ALSO EXPECTED ON TUESDAY, MAINLY OVER EASTERN
KLAMATH AND LAKE COUNTIES. THE ON WEDNESDAY EXPECT DIMINISHING
SHOWERS WITH A SHORTWAVE UPPER RIDGE FORECAST TO BUILD INTO THE
REGION FROM THE WEST. THE RIDGE WILL ALSO BRING A RETURN TO NEAR
OR ABOVE NORMAL TEMPERATURES. /CC

&&

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

CA...NONE.

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

$$

MND/CC/BTL


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