Flash Flood Watch 5, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
506 AM PST TUE DEC 9 2014

.SHORT TERM...A STRONG JET STREAM OVER THE EASTERN AND CENTRAL
PACIFIC COMBINED WITH A PERSISTENT LOW PRESSURE NEAR THE GULF OF
ALASKA WILL BRING A SERIES OF INCREASINGLY STRONG STORMS INTO THE
AREA TODAY THROUGH THURSDAY. THE STORMS EXPECTED WEDNESDAY AND
THURSDAY ARE UNUSUALY STRONG AND MAY BRING SIGNIFICANT WINDS AS
WELL AS MODERATE TO HEAVY PRECIPITAITON WITH THE POTENTIAL FOR
DANGEROUS CONDITIONS AND POWER OUTAGES.

TODAY...AS A FRONT APPROACHES FROM THE WEST AND PUSHES INLAND BY
LATE THIS AFTERNOON, EXPECT INCREASING SOUTH WINDS ALONG THE
COAST WITH GUSTY WINDS DEVLEOPING OVER THE MOUNTAINS. LIGHT TO
MODERATE RAIN IS EXPECTED ALONG THE COAST...WITH AREAS OF LIGHT
RAIN EXPECTED INLAND, ESPECIALLY FROM THE CASCADES WEST. THE MAIN
IMPACT FROM THIS STORM WILL BE ALONG COASTAL AREAS.

THEN TONIGHT INTO WEDNESDAY, A VERY STRONG FRONTAL SYSTEM IS
FORECAST TO BRING A WARM FRONT INTO THE AREA TONIGHT WITH A STRONG
COLD FRONT PUSHING INTO THE COAST WEDNESDAY. THIS FRONT WILL BRING
THE POTENTIAL FOR STRONG AND DANGEROUS HIGH WINDS TO THE COASTAL
WATERS AND ALONG THE COAST...AS WELL AS INLAND INTO THE SHASTA
VALLEY, SUMMER LAKE AREA, AND OVER SOME EAST SIDE MOUNTAINS. HIGH
WINDS WATCHES ARE IN EFFECT FOR THESE AREAS. ALONG THE COAST,
MODELS SHOW A STRONG LOW LEVEL JET OF 70 TO 80 KT AT 925 MB
PUSHING INTO THE COAST WEDNESDAY ALONG WITH A TIGHT SURFACE
PRESSURE GRADIENT. THIS IS EXPECTED TO BRING HIGH WINDS WITH GUSTS
OF 60 MPH OR GREATER TO THE COAST. ALSO THERE IS A POTENTIAL FOR
HURRICANE FORCE GUSTS OVER THE COASTAL HEADLANDS. INLAND, MODELS
INDCATE A POTENTIAL FOR HIGH WINDS WITH GUSTS OF 60 MPH OR GREATER
IN THE SHASTA VALLEY AND SUMMER LAKE AREA AS WELL AS OVER SOME
EAST SIDE MOUNTAINS AS 700 MB WINDS INCREASE TO 65 TO 75 KT AND
THE SURFACE PRESSURE GRADIENT INCREASES WEDNESDAY. BREEZY AND
GUSTY CONDITIONS ARE ALSO EXPECTED FOR OTHER INLAND AREAS.
PORTIONS OF THE ROGUE VALLEY AND VALLEYS EAST OF THE CASCADES MAY
REACH WIND ADVISORY CRITERIA WITH GUSTS OF 45 MPH WEDNESDAY
AFTERNOON AND EVENING.

AS THE FRONT GRADUALLY PUSHES INLAND WEDNESDAY AFTERNOON AND
EVENING, ALSO EXPECT MODERATE TO HEAVY PRECIPITATION TO SPREAD
INTO THE AREA, WITH HEAVIEST AMOUNTS FROM THE CASCADES WEST. SNOW
LEVELS ARE EXPECTED TO REMAIN ABOVE 7000 FT ELEVATION DURING THIS
PERIOD.

OF CONCERN, IS MODELS ARE BEGINNING TO COME INTO AGREEMENT SHOWING
A STRONG LOW DEVELOPING ON THE SOUTHERN END OF THIS COLD FRONT
AND MOVING TOWARDS THE SOUTHERN OREGON COAST WEDNESDAY NIGHT AND
THURSDAY MORNING. THE GFS, NAM, SREF AND ECMWF ALL SHOW A
FAVORABLE TRACK FOR A WIND STORM EVENT WITH A 975 TO 985 MB LOW
TRACKING FROM SOUTHWEST TO NORTHEAST JUST OFF THE SOUTHERN OREGON
COAST. SO HAVE INCREASED WINDS FOR THIS PERIOD WITH PEAK WINDS
EXPECTED THURSDAY MORNING AS THE LOW TRACKS JUST OFF THE COAST.
MODELS INDICATE A 70 TO 80 KT LOW LEVEL JET MOVING INTO THE COAST
WITH A VERY STRONG PRESSURE GRADIENT DEVELOPING AT THE SURFACE
THURSDAY MORNING. INLAND...A MID LEVEL JET AROUND 70 TO 80 KT
ALONG WITH AN INCREASING PRESSURE GRADIENT WILL BRING THE
POTENTIAL FOR DANGEROUS AND STRONG WINDS TO INLAND AREAS. EXPECT
THE BEST CHANCE FOR HIGH WINDS TO BE ALONG THE COAST, INTO THE
SHASTA VALLEY AND SUMMER LAKE AREAS AND OVER THE EAST SIDE MOUNTAINS.
HOWEVER, OF CONCERN WILL BE HOW DEEP THIS LOW DEVELOPS. IF MODELS
CONTINUE TO TRACK THE LOW NEAR THE COAST AND SHOW A DEEPENING LOW
PRESSURE, THEN THIS MAY BRING HIGH WINDS TO SOME WEST SIDE VALLEYS
AND INTO THE SISKIYOUS AND CASCADES MOUNTAINS. STRONG GUSTY WINDS
COMBINED WITH MODERATE TO HEAVY PRECIPITATION MAY BRING SIGNFICANT
IMPACTS WITH HAZARDOUS TRAVEL CONDITIONS, DOWNED TREES AND POWER
OUTAGES.

SNOW LEVELS ARE EXPECTED TO REMAIN HIGH THROUGH THURSDAY MORNING
WITH SNOW LEVELS AROUND 7000 FT OR HIGHER ELEVATION. HOWEVER,
HIGH PRECIPITATION RATES MAY LOCALLY LOWER SNOW LEVELS TO AROUND
6500 FT ELEVATION THOUGH WEDNESDAY EVENING THROUGH THURSDAY
MRONING. THEN AS THE LOW SHIFTS NORTH THURSDAY AFTERNOON AND
EVENING, EXPECT COLD AIR TO MOVE INTO THE AREA AND SNOW LEVELS TO
LOWER TO AROUND 5000 TO 6000 FT WITH CONTINUED AREAS OF MODERATE
PRECIPITATION. ALSO COLD AIR ACCOMPANYING THE LOW MOVES INTO THE
AREA LATE THURSDAY, THIS WILL ALSO BRING SOME UNSTABLE CONDITIONS
WITH A SLIGHT CHANCE FOR THUNDERSTORMS ALONG THE COAST AND INLAND
INTO PORTIONS OF THE WEST SIDE.

GIVEN THE POTENTIAL FOR MULTIPLE IMPACTS AND SIGNIFICANT DAMANGE FROM
THESE STRONG STORMS, AREA RESIDENTS AND TRAVELERS SHOWED STAY
TUNED FOR UPDATES.

&&

.AVIATION...FOR THE 09/12Z TAF CYCLE...CIGS AND VIS ARE GENERALLY
EXPECTED TO REMAIN VFR THROUGH TONIGHT, HOWEVER, THE MOUNT SHASTA
CITY AREA WILL REMAIN MVFR WITH UPSLOPE LOW CLOUDS IN SOUTHERLY
FLOW...AND A FEW VALLEYS LIKE THE ROGUE COULD SEE A PERIOD OF
MVFR/IFR CONDITIONS EARLY THIS MORNING. A STRONG SYSTEM OFFSHORE
WILL INCREASE PRESSURE GRADIENTS AND LEAD TO GUSTY SOUTH WINDS ALONG
THE COAST, AND STRONG WINDS JUST ABOVE THE SURFACE WILL PRODUCE LOW
LEVEL WIND SHEAR AT THE COAST AND JUST INLAND...INCLUDING ROSEBURG.
SCATTERED SHOWERS AND AREAS OF TERRAIN OBSCURATION ARE EXPECTED OVER
THE NEXT 24 HOURS.

VERY STRONG WINDS AND HEAVY PRECIPITATION WILL IMPACT AVIATION
THROUGHOUT THE AREA WEDNESDAY AND THURSDAY.

BPN

&&

.MARINE...UPDATED 330 AM PST MON DEC 8 2014...A VERY STRONG STORM
SYSTEM WILL PRODUCE GALE TO STORM FORCE WINDS AND VERY HEAVY SEAS
TODAY THROUGH THURSDAY. WINDS AND SEAS WILL BE EXTREMELY HAZARDOUS
TO ALL VESSELS, AS GALES OVER THE COASTAL WATERS TODAY BUILD TO
STORM FORCE BY WEDNESDAY. AFTER A BRIEF BREAK WEDNESDAY NIGHT, STORM
FORCE WINDS WILL RETURN THURSDAY MORNING. HURRICANE FORCE GUSTS ARE
POSSIBLE THROUGHOUT THIS TIME.

SEAS WILL BECOME VERY HEAVY AND STEEP, RESULTING FROM LARGE LONG
PERIOD WEST SWELL AND STRONG SOUTHERLY CHOP. COMBINED SEAS WILL
BUILD TO HEIGHTS IN EXCESS OF 25 FEET, WITH BREAKING WAVES OF OVER
30 FEET EXPECTED NEAR SHORE AND NEAR SHOALS AND OTHER SHALLOW WATER
AREAS.

CONFIDENCE IS ABOVE AVERAGE AND INCREASING CONCERNING THE STRENGTH
OF THIS SYSTEM, WHICH WILL LIKELY RANK IN THE TOP 10 PERCENT OF THE
STORMS TO AFFECT OUR REGION. ALL MARITIME AND COASTAL INTERESTS
SHOULD TAKE ALL PRECAUTIONS NECESSARY TO PRESERVE LIFE AND PROPERTY,
AS SIGNIFICANT DAMAGE IS POSSIBLE TO UNSECURED AND EXPOSED EQUIPMENT
AND INFRASTRUCTURE.

BEYOND THURSDAY, WINDS AND SEAS WILL DIMINISH, BUT UNSETTLED WEATHER
WILL CONTINUE. CONTINUED LONG PERIOD SWELL IS EXPECTED THROUGH THE
WEEKEND, WITH ANOTHER ROUND OF WIND AND HEAVY SEAS EXPECTED EARLY
NEXT WEEK. -BPN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH SURF ADVISORY FROM 10 PM THIS EVENING TO 10 AM PST THURSDAY
     FOR ORZ021-022-615-618-619.
     HIGH WIND WATCH FROM LATE TONIGHT THROUGH THURSDAY MORNING FOR
     ORZ021-022-615-618-619.
     HIGH WIND WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
     MORNING FOR ORZ030-031-624-625.

CA...HIGH WIND WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
     MORNING FOR CAZ085-285.
     HIGH WIND WATCH FROM LATE TONIGHT THROUGH THURSDAY MORNING FOR
     CAZ081-281.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 4 PM PST THIS AFTERNOON FOR
     PZZ350-356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 PM PST THIS
     AFTERNOON FOR PZZ350-356.
     STORM WARNING FROM 4 AM WEDNESDAY TO 4 PM PST THURSDAY FOR
     PZZ350-356-370-376.
     GALE WARNING UNTIL 4 PM PST THURSDAY FOR PZZ350-356.
     HAZARDOUS SEAS WARNING UNTIL 4 PM PST THURSDAY FOR PZZ350-356.
     GALE WARNING UNTIL 4 AM PST WEDNESDAY FOR PZZ370-376.
     HAZARDOUS SEAS WARNING UNTIL 4 PM PST THURSDAY FOR PZZ370-376.

CC