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[Printable]
366
FXUS66 KMFR 180352
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
852 PM PDT WED SEP 17 2014

.DISCUSSION...THE UPPER LOW OFFSHORE WILL OPEN UP INTO A TROUGH AS
IT APPROACHES THE COAST OVERNIGHT AND MOVES ONSHORE THURSDAY.
MOIST AIR SURGING NORTHWARD AHEAD OF THIS SYSTEM BROUGHT AN AREA
OF RAIN INTO PORTIONS OF WESTERN SISKIYOU COUNTY AND ALSO
JOSEPHINE AND CURRY COUNTIES THIS AFTERNOON AND EVENING. THE
BULLS-EYE FOR RAINFALL WAS IN AND AROUND CAVE JUNCTION WHERE
0.25-0.35 OF AN INCH FELL IN JUST A FEW HOURS WITH LESSER AMOUNTS
ELSEWHERE. STEADY RAINFALL WAS ALSO REPORTED FOR A FEW HOURS OVER
AND NEAR THE ONION FIRE WITH ISOLATED TO SCATTERED SHOWERS
ELSEWHERE WEST OF THE CASCADES.

MODELS HAVE NOT BEEN VERY GOOD WITH RESPECT TO WHERE RAINFALL HAS
OCCURRED THIS AFTERNOON AND EVENING. OF ALL THE GUIDANCE, THE SREF
HAS BEEN HANDLING IT THE BEST...SO HAVE PLACED MORE EMPHASIS ON
ITS SOLUTION REGARDING POP/QPF THROUGH THE OVERNIGHT. EXPECT MOST
OF THE ACTIVITY TO REMAIN FROM THE CASCADES WESTWARD OVERNIGHT
INTO THURSDAY MORNING. WE SHOULD SEE ANOTHER MORE ORGANIZED AREA
OF RAIN DEVELOP OFFSHORE AND MOVE INTO THE COAST DURING THIS TIME
FRAME. AS THE TROUGH MOVES ONSHORE THURSDAY, SOUTHERLY FLOW ALOFT
WILL WEAKEN. EXPECT ISOLATED TO SCATTERED SHOWERS TO MOVE OVER
THE WEST SIDE VALLEYS AND ALSO THE EAST SIDE, BUT THE BEST
ACTIVITY WILL BE FROM THE CASCADES SOUTHWESTWARD TO WESTERN
SISKIYOU COUNTY. CONVECTIVE PARAMETERS ARE WEAK THURSDAY
AFTERNOON, BUT THERE IS A SLIGHT CHANCE OF THUNDERSTORMS FROM THE
CASCADES EASTWARD. THIS SYSTEM WILL MOVE FAR ENOUGH SOUTH AND EAST
THURSDAY NIGHT THAT THE RISK OF SHOWERS WILL END. AN UPPER RIDGE
WILL BUILD IN FRIDAY INTO SATURDAY RESULTING IN RAPID WARMING AND
DRYING ACROSS THE CWA. SPILDE

&&

.AVIATION...BASED ON THE 18/00Z TAF CYCLE...
GUSTY SOUTH AND SOUTHWEST WINDS WILL DECREASE THIS EVENING ACROSS
THE MOUNTAINS AND EAST SIDE. OTHERWISE THE MAIN IMPACT OF A LOW
GRADUALLY PUSHING INLAND TONIGHT AND THURSDAY WILL BE LOWERED
CEILINGS IN SHOWERS.  RAIN SHOWERS ARE EXPECTED TO CONTINUE ALONG
THE COAST AND COASTAL MOUNTAINS WITH SCATTERED SHOWERS GRADUALLY
PUSHING INLAND TONIGHT INTO THURSDAY. EXPECT PERIODS OF LOCALIZED
IFR TO LIFR ALONG THE COAST IN FOG TONIGHT AND THURSDAY MORNING  AS
WELL AS AREAS OF MVFR CIGS IN SHOWERS THROUGH THURSDAY MORNING. ALSO
ISOLATED THUNDERSTORMS ARE POSSIBLE THROUGH TONIGHT ALONG THE
COAST.   WIDESPREAD MOUNTAIN OBSCURATIONS ARE EXPECTED OVER THE
COASTAL MOUNTAINS THROUGH THURSDAY MORNING. FURTHER INLAND, EXPECT
SCATTERED SHOWERS TO SPREAD INLAND OVERNIGHT AND MORE SO ON
THURSDAY. PARTIAL  MOUNTAIN OBSCURATIONS WILL OCCUR FROM THE
CASCADES WESTWARD TONIGHT THROUGH THURSDAY. VALLEY CEILINGS WILL BE
MOSTLY VFR, EXCEPT AREAS OF MVFR CIGS IN SHOWERS MAINLY FROM THE
CASCADES WEST.  AS THE LOW SHIFTS INLAND THURSDAY, EXPECT VFR OVER
MOST THE AREA BY MID TO LATE THURSDAY  AFTERNOON WITH LOCAL MVFR
CIGS IN SHOWERS AND AREAS OF MOUNTAINS OBSCURATIONS. ALSO ISOLATED
THUNDERSTORMS ARE POSSIBLE FROM THE CASCADES EAST THURSDAY
AFTERNOON. /CC

&&

.MARINE...UPDATED 630 PM PDT WED 17 SEP 2014...LOW PRESSURE WILL
BRING RAIN SHOWERS THROUGH THURSDAY WITH SOUTH WINDS AND BUILDING
SEAS. SEAS ARE EXPECTED TO BECOME STEEP LATE THIS EVENING THROUGH
THURSDAY MORNING. THERE IS ALSO A SLIGHT CHANCE OF THUNDERSTORMS
THROUGH TONIGHT. SEAS WILL GRADUALLY LOWER LATE THURSDAY AND
THURSDAY NIGHT. THEN A DEVELOPING THERMAL TROUGH WILL LEAD TO
INCREASED NORTH WINDS WITH STEEP WIND WAVES LATE FRIDAY AFTERNOON
THROUGH EARLY SATURDAY MORNING. SEAS WILL TRANSITION BACK TO BEING
DOMINATED BY A WESTERLY SWELL OVER THE WEEKEND AND SOUTHERLY WINDS
WILL DEVELOP SUNDAY INTO MONDAY AS A WEAKENING FRONT APPROACHES THE
WATERS. WINDS AND SEAS ARE EXPECTED TO BE BELOW SMALL CRAFT ADVISORY
LEVELS LATE SATURDAY THROUGH MONDAY. /CC

&&

.FIRE WEATHER...WILL ALLOW THE RED FLAG WARNING TO EXPIRE AT 9 PM
PDT THIS EVENING AS WINDS HAVE DIMINISHED IN MOST AREAS AND
RELATIVE HUMIDITY VALUES ARE RECOVERING. SPILDE

&&

.PREV DISCUSSION... /ISSUED 304 PM PDT WED SEP 17 2014/

DISCUSSION...CURRENT VISIBLE IMAGE SHOWS THE BULK OF THE CLOUD COVER
ALONG THE COAST AND INTO DOUGLAS AND JOSEPHINE COUNTIES. ELSEWHERE
THE CLOUDS HAVE DECREASED, BUT MOUNTAIN WAVES ARE FORMING WHICH IS
AN INDICATION OF STRONG WINDS ALOFT. WINDS HAVE BEEN CRANKING UP
OVER THE LAST FEW HOURS AND ARE STRONGEST OVER THE RIDGES AND EAST
OF THE CASCADES. ALSO WINDS CONTINUE TO BLOW IN THE SHASTA VALLEY
AND AT LAST REPORT WEED WAS REPORTING A PEAK GUST OF 52 MPH. EAST OF
THE CASCADES KLAMATH FALLS REPORTED A PEAK WIND OF 41 MPH. THE
MODELS OVERALL ARE UNDERESTIMATING THE WIND SPEEDS AND WILL
GENERALLY BE GOING ABOVE GUIDANCE FOR THE ABOVE MENTIONED LOCATIONS.
MODERATE TO STRONG WINDS WILL CONTINUE AT LEAST THROUGH MIDNIGHT FOR
THE AFOREMENTIONED AREAS, THEN SHOULD SLOWLY DECREASE TOWARDS EARLY
THURSDAY MORNING.

PRECIPITATION AHEAD OF THE UPPER LOW CENTERED NEAR 39N/132W IS
MOVING INTO SOUTHWEST OREGON. SO FAR, A COUPLE OF TICKS ON THE RAIN
GAGE HAS SHOWN UP IN CURRY COUNTY, BUT WE`LL SEE MORE AS RADAR
RETURNS SHOW A LINE OF PRECIPITATION MOVING NORTHWARD TOWARDS CURRY
AND WESTERN JOSEPHINE COUNTY. EVEN THEN, WERE ONLY EXPECTING BETWEEN
0.15 AND 0.25 OF AN INCH TONIGHT. ELSEWHERE, PRECIPITATION AMOUNTS
WILL BE LIGHTER AND MOST ALONG AND WEST OF THE CASCADES. ALSO MODELS
ARE HINTING AT SOME ELEVATED INSTABILITY OVER THE WATERS AND
POSSIBLY RIGHT ALONG THE COAST AND WITH A COOL POOL ALOFT MOVING
OVERHEAD THIS EVENING, THEREFORE FELT IT WAS BEST TO PUT IN A SLIGHT
CHANCE OF THUNDER. ALSO WEAK INSTABILITY IS PRESENT FROM AROUND
CRATER LAKE NORTH AND HAVE KEPT A SLIGHT CHANCE THERE.

THE UPPER TROUGH WILL SPLIT AS IT MOVES INLAND THURSDAY AND THIS
WILL BRING SOME GOOD NEWS. FIRST, IT WILL NOT BE AS WINDY COMPARED
TODAY AND SECOND WE`LL HAVE A BETTER CHANCE OF GETTING MEASURABLE
PRECIPITATION, ESPECIALLY WEST OF THE CASCADES. HOWEVER WITH THE
UPPER TROUGH SPLITTING, THIS WILL TEND TO PUT A CAP ON THE AMOUNT OF
PRECIPITATION. AT THIS TIME, WERE EXPECTING BETWEEN 0.10-0.20 OF AN
INCH FOR THE CASCADES, UP TO 0.10 FOR THE COAST RANGE, 0.10 OR LESS
FOR MOST WEST SIDE LOCATIONS AND 0.05 OR LESS EAST OF THE CASCADES.
THE MODELS ARE IN FAIRLY GOOD AGREEMENT SHOWING THE GREATEST
INSTABILITY FROM THE CASCADES EAST, ALTHOUGH SOME INSTABILITY EXIST
IN EASTERN JACKSON COUNTY AND EASTERN DOUGLAS COUNTY.

THE UPPER TROUGH CONTINUES TO SPLIT THURSDAY NIGHT INTO FRIDAY
MORNING AND A CUTOFF LOW WILL DEVELOP FRIDAY AFTERNOON ON CENTRAL
CALIFORNIA. ANY SHOWERS WILL END THURSDAY NIGHT WITH DRY AND WARMER
WEATHER RETURNING FRIDAY AND LASTING THROUGH THE WEEKEND. A THERMAL
TROUGH WILL DEVELOP OFF THE OREGON COAST AND WE COULD SEE INCREASING
OFFSHORE FLOW WITH MODERATE TO POOR RECOVERIES IN WESTERN SISKIYOU
AND SOUTH COAST RANGE IN OREGON.

THE EC AND GFS ARE IN PRETTY GOOD AGREEMENT SHOWING ANOTHER BROAD
UPPER TROUGH DIGGING NEAR 140W AND THIS WILL KICK THE UPPER LOW IN
CALIFORNIA NORTHEAST INTO SOUTHEAST OREGON, BUT IT SHOULD HAVE
LITTLE OR NO IMPACT FOR US.

THE UPPER TROUGH WILL PUSH EAST TOWARDS THE OREGON COAST MONDAY AND
THE GFS AND EC SHOW ENOUGH INSTABILITY ALONG THE NORTHERN CASCADES
IN THE AFTERNOON TO WARRANT A SLIGHT CHANCE OF STORMS.

THINGS COULD GET INTERESTING OUT TOWARDS THE END OF THE FORECAST
PERIOD. THE EC AND GFS ARE IN REMARKABLE GOOD AGREEMENT SHOWING A
MUCH MORE ACTIVE PATTERN STARTING NEXT WEDNESDAY. OF NOTE THE
PREVIOUS 2 GFS RUNS (6Z AND LAST NIGHTS 0Z) WERE SHOWING A STRONG
RIDGE OVER THE AREA WHILE THE EC WAS STILL SHOWING A MORE ACTIVE
PATTERN. INTERESTING ENOUGH, THE RMOP SHOWS A HIGH PROBABILITY (34%
PROBABILITY) OF A STRONG RIDGE SETTING UP OVER THE REGION IN THE
SAME TIME PERIOD, BUT THIS WAS BASED IN PART ON LAST NIGHTS (0Z)
RUN. IT WILL BE INTERESTING TO SEE WHAT THE 0Z RUN WILL SHOW
TONIGHT. FOR NOW WE FELT IT WAS BEST TO INCREASE POPS ENOUGH FOR A
CHANCE MENTION, BUT IF THE EC AND GFS REMAIN IN GOOD AGREEMENT, THE
POPS WILL NEED TO BE ADJUSTED SIGNIFICANTLY HIGHER. IF WE TAKE THE
OPERATIONAL MODELS AT FACE VALUE, WE COULD BE LOOKING AT OUR FIRST
MODERATE TO HEAVY PRECIPITATION EVENT IN QUITE SOME TIME. AGAIN THIS
IS STILL A WAYS OUT AND WE`LL HAVE TO WATCH HOW THE MODELS TREND
OVER TIME. -PETRUCELLI

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...RED FLAG WARNING UNTIL 9 PM PDT THIS EVENING FOR ORZ624-625.

CA...RED FLAG WARNING UNTIL 9 PM PDT THIS EVENING FOR CAZ284-285.
     RED FLAG WARNING UNTIL 9 PM PDT THIS EVENING FOR CAZ281.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS
     UNTIL 11 AM PDT THURSDAY FOR PZZ370-376.

$$

MAS/MAP/CC







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