Hazardous Seas Warning 33, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
856 PM PDT TUE MAY 27 2014

.DISCUSSION...GUSTY WINDS CONTINUE THIS EVENING ACROSS EASTERN
OREGON AND NORTHEAST CALIFORNIA. THIS PRESENTS A FIRE WEATHER
CONCERN BUT CONDITIONS ARE EXPECTED TO IMPROVE AFTER SUNSET WITH
WINDS DECREASING. OTHERWISE THE SATELLITE IMAGERY SHOWS THE LOW
PRESSURE MOVING INTO THE COASTAL WATERS AND ABOUT 100 MILES WEST
OF FLORENCE OREGON WITH SURFACE FRONT PUSHING INTO NW NEVADA. THE
LATEST GUIDANCE CONTINUES TO SHOW THE LOW MOVING INLAND LATE
TONIGHT INTO WEDNESDAY. THE ATMOSPHERE IS EXPECTED TO BECOME VERY
UNSTABLE WITH POTENTIAL FOR SHOWERS AND THUNDERSTORMS FOR
WEDNESDAY. CURRENT FORECAST COVERS THIS TREND AND NO UPDATE WILL
BE ISSUED THIS EVENING. /FB

&&

.AVIATION...BASED ON 28/00Z TAF ISSUANCE...A WEAK COLD FRONT IS
EXPECTED TO BRING A FEW LIGHT SHOWERS INTO EARLY WEDNESDAY
MORNING...MAINLY IN SOUTHWEST OREGON WITH THE HIGHEST PROBABILITY
NORTH OF THE UMPQUA DIVIDE. AS A RESULT, CEILINGS WILL REMAIN VFR
INTO THE EARLY EVENING THEN CEILINGS WILL BECOME MORE WIDESPREAD AND
THEY WILL LOWER SOME OVERNIGHT. MOSTLY VFR CEILINGS...WITH ISOLATED
MVFR CEILINGS MAINLY WEST OF THE CASCADES ALONG WITH MOUNTAIN
OBSCURATION ARE EXPECTED LATE THIS EVENING THROUGH EARLY WEDNESDAY
MORNING. CONDITIONS WILL IMPROVE IN THE LATE MORNING ON WEDNESDAY
FROM SOUTH TO NORTH. GUSTY WEST WINDS WILL AFFECT MOST AREAS
WEDNESDAY AFTERNOON. -SK

&&

.MARINE...UPDATED 27/1430 AM PDT...
NORTHWEST WINDS WILL DECREASE SOME THIS EVENING AS AN UPPER TROUGH
MOVES OVER THE WATERS. THE WEAKEST WINDS ARE EXPECTED LATE
TONIGHT...AND THEN NORTH WINDS WILL INCREASE SHARPLY LATE
WEDNESDAY...POTENTIALLY REACHING GALE FORCE THURSDAY AFTERNOON IN
THE WATERS SOUTH OF CAPE BLANCO. SEAS WILL FOLLOW A SIMILAR
TREND...HOLDING STEADY AROUND 6 FEET TONIGHT INTO WEDNESDAY
MORNING...THEN STEEPENING AND INCREASING WEDNESDAY
AFTERNOON...ESPECIALLY SOUTH OF CAPE BLANCO. AGAIN...THE STRONGEST
WINDS AND HIGHEST SEAS WILL MOST LIKELY BE ON THURSDAY AFTERNOON AND
EVENING.

REGARDING THUNDERSTORMS...ISOLATED THUNDER IS POSSIBLE THIS AFTERNOON
INTO WEDNESDAY MORNING AS THE UPPER TROUGH MOVES OVER THE WATERS.
/SK

&&

.FIRE WEATHER...WINDS ARE DECREASING A BIT THIS EVENING BUT
RELATIVE HUMIDITY REMAINS IN THE LOWER TO MID TEENS ACROSS
NORTHEAST CALIFORNIA AND PARTS OF THE SHASTA VALLEY. HAVE EXTENDED
THE RED FLAG WARNING UNTIL 2100 PDT. CONDITIONS WILL GRADUALLY
IMPROVE ESPECIALLY WITH WINDS COMING DOWN BELOW CRITERIA AFTER
SUNSET. HOWEVER HUMIDITY MAY NOT CLIMB ABOVE 20 PERCENT UNTIL
MIDNIGHT. /FB

&&

.PREV DISCUSSION... /ISSUED 707 PM PDT TUE MAY 27 2014/

DISCUSSION...27/12Z NAM/GFS IN.

AN UPPER LEVEL LONG WAVE TROUGH WILL REMAIN NEAR OR OVER THE
PACIFIC NORTHWEST THROUGH THE REST OF THIS WEEK...MAKING FOR
GENERALLY UNSETTLED WEATHER OVER THE AREA.

AS FOR THE DETAILS...A CLOSED UPPER LOW WILL MOVE ONSHORE OVER
THE PACIFIC NORTHWEST THIS EVENING. EXPECT GUSTY WINDS TO DEVELOP
OVER THE RIDGES AND EAST OF THE CASCADES THIS AFTERNOON...WITH
SHOWERS MOVING IN THIS AFTERNOON AS WELL. DUE TO THE LOW RELATIVE
HUMIDITY EXPECTED OVER PORTIONS OF THE MODOC...A RED FLAG WARNING
(RFWMFR) IS IN EFFECT THERE. THERE WILL ALSO BE GUSTY NORTHWEST WINDS
IN THE ROGUE VALLEY THIS AFTERNOON AND EVENING (15-25 MPH).

ISOLATED THUNDERSTORMS ARE ALSO POSSIBLE...MAINLY UNDER THE COLD
POOL ALOFT. THAT COLD POOL WILL REMAIN OFFSHORE THIS
AFTERNOON...THEN TRACK ACROSS THE UMPQUA BASIN TONIGHT INTO
WEDNESDAY BEFORE RETREATING TO THE NORTHEAST WEDNESDAY AFTERNOON
AND EVENING.

THURSDAY LOOKS TO BE RELATIVELY QUIET WITH A DEARTH OF SHORT
WAVE ACTIVITY OVER THE AREA. HOWEVER....FRIDAY LOOKS MORE
UNSTABLE AS A SHORT WAVE WILL ROUND THE RESIDUAL TROUGH AND MOVE
OVER THE AREA IN THE AFTERNOON. THIS WILL SUPPORT CONVECTION AND
THUNDERSTORMS...MOSTLY OVER HIGHER TERRAIN. FRIDAY ALSO LOOKS TO
BE THE WARMEST DAY OF THE WEEK OVER INLAND AREAS.

LONG TERM...SATURDAY THROUGH TUESDAY NIGHT.

THE MAIN ISSUE IN THE LONG TERM IS THE POTENTIAL FOR THUNDERSTORMS.
THE 12Z GFS AND 12Z ECMWF MODELS ARE IN BETTER THAN NORMAL AGREEMENT
THROUGH SUNDAY WITH AN UPPER LEVEL TROUGH MOVING ACROSS THE REGION.
BOTH MODELS HAVE TRENDED SLIGHTLY MORE PROGRESSIVE WHEN COMPARED TO
THEIR EARLIER RUNS. BEYOND SUNDAY, THEY BOTH HAVE A SIMILAR
EVOLUTION OF THE UPPER LEVEL PATTERN BUT WITH DIFFERENCES IN TIMING
AND STRENGTH OF THE NEXT UPPER TROUGH.

AFTER THE EXPECTED WEST SIDE AND CASCADE FOCUS TO THUNDERSTORM
DEVELOPMENT ON FRIDAY AFTERNOON AND EVENING WITH THE UPPER TROUGH
CENTERED NEAR CAPE MENDOCINO, THE TROUGH IS FORECAST TO MOVE
SOUTHEAST TOWARD THE SAN FRANCISCO BAY AREA ON SATURDAY. THIS WILL
LIKELY LEAD TO A LARGER REGION OF ENHANCED INSTABILITY AND AN
INCREASE IN MID-LEVEL MOISTURE. COOS COUNTY AND THE NORTHWESTERN
PORTION OF DOUGLAS COUNTY WILL HAVE THE LOWEST PROBABILITY OF
AFTERNOON AND EVENING THUNDERSTORMS WHILE BOTH THE ECMWF AND GFS
CURRENTLY SHOW A FOCUS FROM WESTERN SISKIYOU COUNTY ACROSS THE
SISKIYOUS AND CASCADES INTO NORTHERN PORTION OF KLAMATH AND LAKE
COUNTIES.

ACTIVITY WILL THEN DIMINISH SUBSTANTIALLY, BUT A FEW LIGHT
CONVECTIVE SHOWERS MAY LINGER LATE SATURDAY NIGHT INTO SUNDAY
MORNING AS THE TROUGH AXIS SHIFTS EAST OF OUR AREA. A SHORTWAVE IN A
WEST TO NORTHWEST FLOW ALOFT ON THE BACKSIDE OF THE TROUGH IS
EXPECTED TO PRODUCE WEAK INSTABILITY ON SUNDAY OVER SOUTHERN AND
EASTERN SISKIYOU COUNTY AND ACROSS THE EAST SIDE. THE ECMWF IS A BIT
WEAKER THAN THE GFS WITH THE INSTABILITY AS IT HAS A STRONGER
SHORTWAVE RIDGE BUILDING IN FROM THE SOUTHWEST. I HAVE LEANED TOWARD
THE MORE ACTIVE GFS FOR NOW.

AS MENTIONED ABOVE, THE NEXT UPPER TROUGH IS EXPECTED TO MOVE
SOUTHEAST INTO THE PACIFIC NORTHWEST ON MONDAY. GIVEN ITS LESS
AMPLIFIED SOLUTION ON SUNDAY, IT FOLLOWS THAT THE GFS IS MORE
PROGRESSIVE THAN THE ECMWF AND HAS A DEEPER/COLDER/MORE UNSTABLE
SOLUTION FOR THE TROUGH. ONCE AGAIN, I HAVE LEANED TOWARD THE GFS
BUT WOULD EXPECT ADJUSTMENTS TO BE MADE AS THE TIME DRAWS NEARER.
THE GFS SUPPORTS ISOLATED THUNDERSTORMS ON THE EAST SIDE MONDAY
AFTERNOON WITH PERHAPS A FEW WEST-SIDE SHOWERS ON THE BACK SIDE OF
THE TROUGH. MEANTIME, THE SLOWER AND WEAKER ECMWF HAS A SLIGHT
CHANCE OF THUNDERSTORMS OVER THE HIGHER TERRAIN OF THE WEST SIDE AND
THE CASCADES.

THESE MODEL DIFFERENCES INCREASE BY AN ORDER OF MAGNITUDE ON DAY
7/TUESDAY WITH THE FASTER GFS PUSHING THE MAIN REGION OF INSTABILITY
EAST OF OUR AREA WHILE THE ECMWF SUGGESTS INSTABILITY WILL BE
FOCUSED OVER OUR AREA FROM THE CASCADES EASTWARD.  /DW

AVIATION...BASED ON 27/18Z TAF ISSUANCE...A VFR STRATOCUMULUS DECK
IS LINGERING OVER WESTERN OREGON THIS AFTERNOON BUT THE MAIN WEATHER
FEATURE IS STRONG SOUTHWEST TO WEST WINDS. THESE WINDS WILL PEAK IN
THE EARLY EVENING...ARE LIKELY TO BRING MOUNTAIN TURBULENCE AND WILL
BE STRONGEST EAST OF THE CASCADES.

A WEAK COLD FRONT IS EXPECTED TO BRING A FEW LIGHT SHOWERS FROM THIS
AFTERNOON INTO EARLY WEDNESDAY MORNING...MAINLY IN SOUTHWEST OREGON
WITH THE HIGHEST PROBABILITY NORTH OF THE UMPQUA DIVIDE. AS A
RESULT, CEILINGS WILL REMAIN MAINLY VFR INTO THE EARLY EVENING THEN
CEILINGS WILL BECOME MORE WIDESPREAD AND THEY WILL LOWER. MVFR
CEILINGS WITH HIGHER TERRAIN OBSCURATIONS WILL BE PREVALENT IN
SOUTHWEST OREGON BETWEEN 07Z AND 17Z. CONDITIONS WILL IMPROVE IN THE
LATE MORNING ON WEDNESDAY. BUT THEN ANOTHER SHORTWAVE DISTURBANCE
WILL ARRIVE IN THE AFTERNOON WITH AREAS OF MVFR CEILINGS AND
SCATTERED SHOWERS AT THE COAST AND NORTH OF THE UMPQUA DIVIDE.
ELSEWHERE, ACROSS SOUTH CENTRAL OREGON AND NORTHERN CALIFORNIA,
CONDITIONS ARE EXPECTED TO REMAIN VFR WITH AREAS OF MID-LEVEL CLOUD
CEILINGS. -DW

MARINE...UPDATED 27/230 PM PDT...NORTHWEST WINDS WILL DECREASE
SOME THIS EVENING AS AN UPPER TROUGH MOVES OVER THE WATERS. THE
WEAKEST WINDS ARE EXPECTED LATE TONIGHT...AND THEN NORTH WINDS
WILL INCREASE SHARPLY LATE WEDNESDAY...POTENTIALLY REACHING GALE
FORCE THURSDAY AFTERNOON IN THE WATERS SOUTH OF CAPE BLANCO. SEAS
WILL FOLLOW A SIMILAR TREND...HOLDING STEADY AROUND 6 FEET TONIGHT
INTO WEDNESDAY MORNING...THEN STEEPENING AND INCREASING WEDNESDAY
AFTERNOON...ESPECIALLY SOUTH OF CAPE BLANCO. AGAIN...THE STRONGEST
WINDS AND HIGHEST SEAS WILL MOST LIKELY BE ON THURSDAY AFTERNOON
AND EVENING.

REGARDING THUNDERSTORMS...ISOLATED THUNDER IS POSSIBLE THIS AFTERNOON
INTO WEDNESDAY MORNING AS THE UPPER TROUGH MOVES OVER THE WATERS.

&&

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

CA...RED FLAG WARNING UNTIL 9 PM PDT THIS EVENING FOR CAZ285.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS FROM 5 PM WEDNESDAY TO 11 AM PDT
     FRIDAY FOR PZZ356-376.
     HAZARDOUS SEAS WATCH FROM THURSDAY MORNING THROUGH FRIDAY
     MORNING FOR PZZ350-356-370.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 5 PM WEDNESDAY TO
     11 PM PDT FRIDAY FOR PZZ350-356-370-376.
     GALE WATCH FROM THURSDAY MORNING THROUGH FRIDAY MORNING FOR
     PZZ376.
     HAZARDOUS SEAS WATCH FROM WEDNESDAY AFTERNOON THROUGH FRIDAY
     MORNING FOR PZZ376.
     SMALL CRAFT ADVISORY FOR WINDS FROM 11 AM THURSDAY TO 11 AM PDT
     FRIDAY FOR PZZ350-370.

FJB/DW/NSK