Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 220300
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
800 PM PDT SUN SEP 21 2014

.DISCUSSION...22/00Z NAM IN.

A CUTOFF LOW IS NOW NEAR THE IDAHO/OREGON/NEVADA TRIPLE POINT.
SHORT WAVES ROTATING AROUND THE LOW INDUCED ENOUGH INSTABILITY TO
SUPPORT SOME THUNDERSTORMS OVER THE SISKIYOUS AND CASCADES AS WELL
AS EAST OF THE CASCADES. THE LAST OF THOSE THUNDERSTORMS ARE NOW
DISSIPATING. CONVECTIVE DEBRIS REMAINS OVER THE AREA...ALONG WITH
LOTS OF MARINE STRATUS AND FOG ALONG THE COAST.

THE CUTOFF WILL MOVE OUT OF THE LOCAL WEATHER PICTURE TONIGHT...
AND A WEAK RIDGE WILL MAKE FOR A WARM AND MOSTLY DRY DAY OVER THE
MEDFORD CWA. THE EXCEPTION WILL BE SOME ISOLATED AFTERNOON AND
EVENING SHOWERS OVER THE CASCADES. THE MODELS DO SUGGEST SOME
INSTABILITY THERE...PRIMARILY FROM AROUND CRATER LAKE NORTH. NOT
MUCH SUPPORT ELSEWHERE SO DON`T EXPECT A LOT OF ACTIVITY...MAKING
THEM SHOWERS INSTEAD OF THUNDERSTORMS WAS A GOOD MOVE. SOUTH TO
SOUTHWEST FLOW ALOFT WILL GRADUALLY STRENGTHEN MONDAY AND THIS
SHOULD LEAD TO SOME GUSTY WINDS IN THE SHASTA VALLEY DURING THE
AFTERNOON AND EVENING...BUT NOT STRONG ENOUGH TO WARRANT
ADVISORIES.

ATTENTION WILL THEN TURN TO THE WEST WHERE A LONG WAVE TROUGH
CONTINUES TO DIG AROUND 145W. THIS TROUGH WILL NOT MOVE ONSHORE
UNTIL FRIDAY OR SO...BUT SHORT WAVES EJECTING FROM THIS TROUGH
WILL BEGIN TO AFFECT THE MEDFORD CWA MONDAY EVENING. THIS WAVE
WILL PUSH A FRONT ONSHORE MONDAY NIGHT INTO TUESDAY. THIS FRONT
WILL BE WEAK AND THE ASSOCIATED PRECIPITATION WILL LIKELY BE
LIMITED TO THE COAST AND COAST RANGE. THE COOLING TREND WILL
CONTINUE AND THIS FRONT WILL LIKELY KICK UP SOME STRONG WINDS EAST
OF THE CASCADES AND IN THE SHASTA VALLEY. A FIRE WEATHER WATCH IS
CURRENTLY IN EFFECT FOR THOSE AREAS.

AFTER THAT INITIAL WAVE...A PARADE OF WAVES WILL FOLLOW UNTIL THE
LONG WAVE TROUGH MOVES ONSHORE. A STRONG WAVE WILL MOVE ONSHORE
WEDNESDAY MORNING AND THIS WILL PUSH A STRONGER AND MUCH WETTER
FRONT ONSHORE LATE TUESDAY NIGHT AND EARLY WEDNESDAY MORNING. JUST
ABOUT ALL OF THE AREA FROM THE CASCADES WEST WILL SEE SOME
PRECIPITATION FROM THIS FRONT AND SOME AREAS ARE GOING TO GET A
LOT OF RAIN. THE MOST WILL LIKELY FALL IN THE COAST RANGE ABOVE
BROOKINGS. THIS WILL ALSO MAKE FOR ANOTHER BREEZY DAY EAST OF THE
CASCADES. INLAND TEMPERATURES WILL DROP TO JUST BELOW NORMAL
VALUES WEDNESDAY.

EXTENDED DISCUSSION FROM THE SUNDAY AFTERNOON AFD...WEDNESDAY
NIGHT THROUGH SUNDAY. A BROAD TROUGH WILL SET UP OVER THE AREA
THROUGH THE END OF THE WORK WEEK AND THIS WILL KEEP A COOL...
SHOWERY PATTERN OVER SOUTHWEST OREGON AND NORTHERN CALIFORNIA.
HIGH TEMPERATURES WILL BE 5-10 DEGREES BELOW NORMAL.

THERE ARE STILL LARGE DIFFERENCES IN THE EXTENDED GUIDANCE
REGARDING THIS WEEKEND`S FORECAST. THE ECMWF CUTS OFF A LOW OVER
CENTRAL CALIFORNIA AND NEVADA...WHILE THE GFS KICKS THE LOW OUT
AND BUILDS A RIDGE OVER THE AREA. IT WILL PROBABLY FALL SOMEWHERE
IN BETWEEN THESE SOLUTIONS WHERE THE TROUGH DOESN`T EJECT QUITE AS
FAST AS THE GFS, BUT ALSO ISN`T QUITE AS DEEP AS THE ECMWF. FOR
NOW, HAVE MADE FEW CHANGES TO THE EXTENDED KEEPING SLIGHT CHANCE
TO CHANCE POPS WITH ONLY A SLIGHT MODERATING TREND. SPILDE

&&

.AVIATION...BASED ON THE 22/00Z TAF CYCLE...IFR/MVFR CIGS/VSBYS
ALONG THE COAST WILL SPREAD BACK INTO THE COASTAL VALLEYS AND THE
LOWER UMPQUA BASIN LATE TONIGHT AND PERSIST INTO MONDAY MORNING.
ELSEWHERE...VFR CONDITIONS WILL PREVAIL THROUGH THE NEXT 24
HOURS...EXCEPT FOR LOCAL MVFR VSBYS IN SMOKE NEAR WILDFIRES IN
JOSEPHINE COUNTY AND THE WESTERN PORTION OF SISKIYOU COUNTY. ALSO,
ISOLATED SHOWERS AND THUNDERSTORMS HAVE DEVELOPED THIS AFTERNOON AND
EVENING OVER THE CASCADES...THE EAST SIDE...AND PORTIONS OF NORTHERN
CALIFORNIA...BUT THESE SHOULD BEGIN TO DISSIPATE SHORTLY AFTER
SUNSET. THE AREA SHOULD THEN REMAIN DRY, ALTHOUGH SOME SHOWERS ARE
ALSO POSSIBLE ALONG THE CASCADES MONDAY AFTERNOON AS A WEAK FRONT
PASSES OVER THE REGION. -BPN

&&

.MARINE...UPDATED 130 PM PDT SUN 21 SEP 2014...HIGH PRESSURE
WILL REMAIN OVER THE WATERS INTO EARLY MONDAY WITH LIGHT TO
MODERATE SOUTHERLY WINDS AND SEAS. SOUTHERLY WINDS WILL INCREASE
MONDAY AFTERNOON AS A SERIES OF COLD FRONTS APPROACH THE REGION. THE
FIRST FRONT WILL ARRIVE MONDAY NIGHT, WITH OTHERS FOLLOWING THROUGH
THE WEEK. EACH WILL BRING PERIODS OF RAIN WITH INCREASED WINDS AND
STEEP TO VERY STEEP SEAS. EXPECT SMALL CRAFT ADVISORY CONDITIONS FOR
MUCH OF THIS TIME, WITH GALES AND HAZARDOUS SEAS LIKELY TO ACCOMPANY
THE STRONGER COLD FRONT MIDWEEK. CONDITIONS SHOULD IMPROVE BY FRIDAY
WHEN HIGH PRESSURE ONCE AGAIN BUILDS INTO THE AREA.
-BPN/DW

&&

.HYDROLOGY...THE FLASH FLOOD THREAT FOR THE DEBRIS FLOW THAT
OCCURRED YESTERDAY AND LAST NIGHT ON THE SOUTHEAST DRAINAGES OF
MOUNT SHASTA...INCLUDING MUD AND PILGRIM CREEKS...HAS DIMINISHED
THIS EVENING AS FLOOD WATERS HAVE SUBSIDED. HOWEVER...RAINS
MOVING IN WEDNESDAY MAY STILL PRESENT A FLOODING THREAT TO THE
AREA. WE`LL CONTINUE TO MONITOR THE LATEST CONDITIONS WITH THE
FOREST SERVICE...AVALANCHE CENTER AND LAW ENFORCEMENT SHOULD
CONDITIONS CHANGE.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...FIRE WEATHER WATCH FROM TUESDAY MORNING THROUGH TUESDAY EVENING
        FOR ORZ624-625.

CA...FIRE WEATHER WATCH FROM TUESDAY MORNING THROUGH TUESDAY EVENING
        FOR CAZ281-282-284-285.

PACIFIC COASTAL WATERS...NONE.

$$

15/15/15



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