Area Forecast Discussion
Issued by NWS Medford, OR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KMFR 280347
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
847 PM PDT SUN JUL 27 2014

.SHORT TERM...HIGH CLOUDS HAVE LINGERED OVER MUCH OF THE AREA AS A
SHORTWAVE LIFTS OUT OF THE AREA TO THE NORTH AND WEAKER SHORTWAVE
MOVES OVER SOUTHWEST OREGON. HIGH CLOUDS HAVE KEPT HEATING DOWN A
BIT AND HAS LIMITED ANY CONVECTIVE DEVELOPMENT THIS EVENING. A
FEW CUMULUS CLOUDS DEVELOPED IN WESTERN SISKIYOU COUNTY BUT DID
NOT GROW INTO THUNDERSTORMS. ELSEWHERE NO THUNDERSTORMS HAVE
DEVELOPED. WITH SUNSET AND DECREASED HEATING AS WELL AS NO STRONG
SHORTWAVES, DO NOT EXPECT AN THUNDERSTORMS FOR THE REMAINDER OF
THE EVENING. SO HAVE TAKEN THE ISOLATED THUNDERSTORMS OUT OF THE
FORECAST.

OTHERWISE, THE FORECAST REMAINS ON TRACK WITH SOME LIMITED
INSTABILITY, MOISTURE AND WEAK SHORTWAVE ACTIVITY MOVING INTO THE
AREA MONDAY AFTERNOON AND EVENING, MAINLY FROM THE CASCADES
EASTWARD IN OREGON AND OVER PORTIONS OF NORTHERN CALIFORNIA. THE
00Z NAM CONTINUES TO SHOW THAT THE CWA WILL BE ON THE NORTHERN EDGE
OF THE MONSOON MOISTURE. GIVEN THE LACK OF A STRONG SHORTWAVE
TRIGGER AND LIMITED MOISTURE, EXPECT ISOLATED THUNDERSTORM
DEVELOPMENT ON MONDAY. THUNDERSTORMS THAT DO DEVELOP MONDAY MAY
BE DRY. THEN ON TUESDAY, INCREASING MONSOON MOISTURE AND SHORTWAVE
ACTIVITY MOVING WILL BRING A HEIGHTENED CHANCE FOR THUNDERSTORMS
TO NORTHERN CALIFORNIA AND FROM THE CASCADES EAST IN OREGON. THE
CHANCE FOR THUNDERSTORMS WEST OF THE CASCADES LOOKS TO BE MORE
LIMITED IN OREGON ON TUESDAY GIVEN A SOUTH TO SSW STEERING FLOW
SHOWN IN THE NAM FORECAST. HOWEVER...THE 12Z AND 18Z GFS INDICATES
THE POTENTIAL FOR LIGHT SSE FLOW AND SHOWS THE POTENTIAL FOR
THUNDERSTORMS INTO AREAS OF THE WEST SIDE. WILL NEED TO MONITOR
THE DETAILS OF THIS SCENARIO WITH FUTURE MODEL RUNS.

&&

.AVIATION...BASED ON THE 28/00Z TAFS...

VFR CEILINGS WILL CONTINUE OVER THE AREA THIS EVENING WITH AREAS
OF HIGH CLOUDS, MAINLY FROM THE CASCADES EASTWARD. OVERNIGHT, THE
HIGH CLOUDS WILL DISSIPATE WHILE COASTAL IFR LOW CLOUDS AND FOG WILL
FORM ALONG MUCH OF THE COAST. ALSO, LOW LEVEL NORTHERLY WINDS THAT
ARE STRONG NEAR THE COAST (INCLUDING GUSTS TO 30 KT REPORTED AT
KOTH THIS AFTERNOON) WILL WEAKEN OVERNIGHT.

THE COASTAL IFR WILL DISSIPATE AROUND 16Z MONDAY MORNING BUT COASTAL
NORTHERLY WINDS WILL INCREASE AGAIN. MID-LEVEL MOISTURE WILL
INCREASE MONDAY AFTERNOON WITH A SLIGHT CHANCE OF THUNDERSTORMS
THROUGH MONDAY EVENING FROM SISKIYOU COUNTY NORTHEASTWARD ACROSS THE
SISKIYOU AND CASCADE MOUNTAINS AND SOUTH CENTRAL OREGON...INCLUDING
KLMT. /DW


&&

.MARINE...UPDATED 230 PM PDT 27 JULY 2014...

THE 12Z GFS AND NAM MODELS ARE IN AGREEMENT THAT THE CURRENT PATTERN
WITH SOME SLIGHT DAY-TO-DAY VARIATION WILL PERSIST THIS WEEK. HIGH
PRESSURE IS CENTERED OFFSHORE AND A THERMAL TROUGH IS OVER NORTHERN
CALIFORNIA WHICH WILL CONTINUE TO RESULT IN STEEP TO VERY STEEP WIND
WAVE DOMINATED SEAS. THE STRONGEST WINDS WILL OCCUR IN THE OUTER
WATERS SOUTH OF CAPE BLANCO AND DURING THE AFTERNOON AND EVENING
HOURS. BUT, WITH A VERY SLIGHT WEAKENING IN THE PRESSURE GRADIENT
TONIGHT THAT WILL PERSIST INTO TUESDAY NIGHT. WIND SPEEDS ARE
FORECAST TO HAVE A SLIGHT INCREASING TREND WEDNESDAY INTO FRIDAY.
/DW


&&

.PREV DISCUSSION... /ISSUED 253 PM PDT SUN JUL 27 2014/

SHORT TERM...A SHORT WAVE TROUGH IS MOVING NORTH INTO SW OREGON
THIS AFTERNOON. UNDER MOST CIRCUMSTANCE THIS WOULD CAUSE THE AIR
MASS TO BE VERY UNSTABLE BUT THERE WERE JUST TOO MUCH CLOUD COVER
DURING THE DAY. THE SHORT WAVE TROUGH IS EXPECTED TO MOVE INTO
EASTERN DOUGLAS COUNTY THIS EVENING WITH A WEAK TROUGH COMING UP
INTO SOUTHERN SISKIYOU COUNTY. SATELLITE IMAGERY SHOWS SOME
CLEARING AREA COMING UP FROM THE SOUTH. THIS COULD BE ENOUGH TO
GENERATE SOME THUNDERSTORM ACTIVITY, ESPECIALLY FROM THE MARBLE
MTNS NORTH INTO SOUTHERN OREGON CASCADES.

SOUTH TO SOUTHWEST FLOW AROUND THE WEST SIDE OF THE UPPER LEVEL
RIDGE WILL CONTINUE TO BRING A SERIES OF SHORT WAVE DISTURBANCE TO
OUR FORECAST AREA NEXT WEEK. SOUTHERN OREGON AND NORTHERN
CALIFORNIA WILL BE ON THE WESTERN EDGE OF THE CORE MONSOONAL
MOISTURE SO ANY STORMS WILL NOT PRODUCE A LOT OF RAIN. HOWEVER
LACK OF A STRONG SHORT WAVE SIGNATURE WILL PREVENT THUNDERSTORMS
FROM GENERATING MORE THAN ISOLATED COVERAGE ON MONDAY.

ON TUESDAY BOTH THE NAM AND THE GFS SHOW A MUCH STRONGER SHORT
WAVE SIGNATURE MOVING INTO NE CALIFORNIA. PRECIPITABLE WATER IS
ALSO HIGHER ON TUESDAY SO THERE IS GOING TO BE ENOUGH CAPE TO
GENERATE MORE THUNDERSTORMS. MODEL DYNAMICS AND OTHER LIGHTNING
FORECAST CHARTS POINT TO THE CASCADES MOUNTAINS EASTWARD INTO
KLAMATH/LAKE COUNTIES AS AREAS LIKELY TO SEE MOST LIGHTNING
STRIKES ON TUESDAY...ALTHOUGH TOTAL COVERAGE AREA ON TUESDAY
INCLUDE EASTERN DOUGLAS COUNTY, SISKIYOU, MODOC AND PARTS OF
JACKSON COUNTY THAT ARE CLOSE TO THE CASCADES AND THE SISKIYOUS.

LONG TERM...WE ARE LOCKED INTO THIS SOUTHERLY FLOW ALOFT BRINGING
MOISTURE AND INSTABILITY ACROSS OUR FORECAST AREA. DID NOT MAKE
MAJOR CHANGES TO THE PREVIOUS LONG TERM FORECAST AS THE TREND HAS
NOT CHANGED. WE WILL SEE THREATS OF THUNDERSTORMS ALL NEXT WEEK
AND TIMING OF EACH STORM WILL HAVE TO BE DONE ON A SHORT TERM
NOTICE. /FB

FIRE WEATHER...A ROUND OF THUNDERSTORMS CAN BE EXPECTED ON MONDAY
AND THESE WILL LIKELY BE ISOLATED COVERAGE AGAIN DUE TO LACK OF
STRONG SHORT WAVE ENERGY TO ENHANCE THE TRIGGER. HOWEVER FROM
TUESDAY ONWARD THINGS COULD BE QUITE ACTIVE EACH AFTERNOON AND
EVENING. THESES STORMS WILL PRODUCE MORE LIGHTNING BUT ALSO MORE
RAIN AND LIGHTNING ACTIVITY LEVEL COULD APPROACH 3 OR 4 AT TIMES,
ESPECIALLY IN LAKE AND MODOC COUNTIES. /FB


&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM PDT TUESDAY FOR
     PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT TUESDAY
     FOR PZZ350-356-370-376.
     HAZARDOUS SEAS WARNING UNTIL 11 PM PDT THIS EVENING FOR PZZ376.

$$

CC





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.