Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 080412
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
812 PM PST SUN FEB 7 2016

.DISCUSSION...THE THERMAL TROUGH IS STRENGTHENING TONIGHT ALONG
THE COAST. TEMPERATURES ALONG SOUTHERN CURRY COUNTY COAST
CONTINUE TO BE IN THE UPPER 60S. OVERNIGHT LOWS AT BROOKINGS WILL
BE QUITE WARM WITH HUMIDITY IN THE COASTAL RANGE IN THE 35-50
PERCENT RANGE. SINCE WE WILL START OUT SO WARM MONDAY
MORNING..EXPECT BROOKINGS TEMPERATURES TO BE QUITE MILD ON MONDAY.
ELSEWHERE CLEAR SKIES WILL BE THE NORMS TONIGHT EXCEPT FOR AREAS
OF FOG AND LOW CLOUDS IN THE ROSEBURG AND POSSIBLY NORTHERN
JOSEPHINE COUNTY. THE LOW CLOUDS SHOULD BURN OFF MUCH QUICKER ON
MONDAY AS DRIER AND SUBSIDING AIR SPREAD INTO THE AREA. WE HAVE
UPDATED THE GRIDS TO REFLECT WARMER TEMPERATURES AND LOWER
HUMIDITY AT THE COOS COUNTY COAST TONIGHT AND MONDAY. OTHERWISE
THE SHORT TERM FORECAST IS ON TRACK. /FB

&&

.AVIATION...FOR THE 08/00Z TAF CYCLE...VFR CONDITIONS WILL CONTINUE
ACROSS MOST THE AREA TONIGHT INTO TUESDAY. OFFSHORE FLOW IS EXPECTED
TO BE SLIGHTLY STRONGER COMPARED TO LAST NIGHT BRINGING ENOUGH DRY
AIR WHICH SHOULD PREVENT OR AT LEAST LIMIT LOW CLOUD AND FOG
FORMATION OVERNIGHT AND MONDAY MORNING. THE EXCEPTION WILL BE IN
UMPQUA VALLEY, INCLUDING KRBG, WHERE LOW CLOUDS AND FOG ARE EXPECTED
TO DEVELOP BETWEEN 6-9Z AND CONTINUE THROUGH MONDAY MORNING. PATCHY
SHALLOW FOG IS POSSIBLE IN THE ILLINOIS VALLEY AND PORTIONS OF THE
ROGUE VALLEY.  AT KMFR EXPECT CONDITIONS TO REMAIN VFR...HOWEVER
THERE REMAINS A SLIGHT CHANCE FOR PATCHY FOG AROUND 15Z MONDAY BUT
GUIDANCE SUPPORTS CONTINUED VFR SO HAVE KEPT FOG OUT OF KMFR TAF
FOR NOW. /CC


&&

.MARINE...UPDATED 800 PM PST SUN FEB 7 2016...A WEAK THERMAL TROUGH
ALONG THE COAST IS BRINGING LIGHT NORTHEAST WINDS. LIGHT EAST TO
NORTHEAST WINDS WILL PERSIST THROUGH MONDAY.  WINDS WILL BECOME
SOUTH MONDAY EVENING AS LOW PRESSURE DEEPENS BEYOND 130W. STEEP SEAS
DOMINATED BY A LONG PERIOD WEST SWELL WILL BUILD INTO THE WATERS
MONDAY AS A LONG PERIOD WEST SWELL OF AROUND 10 FEET AT 16 SECONDS
BUILDS INTO THE WATERS.

A FRONT MAY NEAR THE COASTAL WATERS LATE WEDNESDAY THEN MOVE INTO
THE WATERS THURSDAY INTO EARLY FRIDAY. MODELS CONTINUE TO SHOW
VARIABILITY WITH THE STRENGTH AND TIMING OF THIS FRONTAL SYSTEM
THOUGH AND CONFIDENCE IS LOW TO MODERATE ON DETAILS FOR WAVE AND
WIND FORECASTS DURING THIS PERIOD. OVERALL, EXPECT AN INCREASE IN
SEAS LATE WEDNESDAY AND THURSDAY, WITH THE POTENTIAL FOR STEEP SEAS
DURING THIS PERIOD AND A SLIGHT CHANCE FOR SMALL CRAFT ADVISORY
LEVEL WINDS. ANOTHER STEEP LONG PERIOD SWELL IS EXPECTED TO MOVE
INTO THE WATERS THURSDAY NIGHT AND FRIDAY. /FB

&&

.PREV DISCUSSION... /ISSUED 216 PM PST SUN FEB 7 2016/

DISCUSSION...

SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT...WITH HIGH
PRESSURE JUST TO OUR EAST AND UPPER LEVEL RIDGING DIRECTLY
OVERHEAD, THERE WILL BE LITTLE IN THE WAY OF IMPACTFUL WEATHER
DURING THE SHORT TERM. HOWEVER, THERE WILL BE A FEW THINGS WORTH
KEEPING AN EYE ON.

WITH HIGH PRESSURE TO THE EAST AND GENERALLY LOWER PRESSURE
OFFSHORE TO THE WEST, WE WILL HAVE PREVAILING OFFSHORE FLOW
THROUGH THE TERM. THIS WILL BRING SOME GUSTY WINDS TO THE RIDGES
OF THE CASCADES AND COASTAL RANGES, ESPECIALLY MONDAY NIGHT WHEN
THE GRADIENT REACHES A PEAK. THIS SAME FLOW PATTERN WILL ALSO
RESULT IN DOWNSLOPING FOR MUCH OF THE WEST SIDE. DEPENDING ON THE
STRENGTH OF THE OVERNIGHT INVERSIONS, THIS MAY BE ENOUGH TO KEEP
FOG OUT OF SOME VALLEYS, BUT CONFIDENCE IS MUCH TOO LOW TO BEGIN
PICKING SPECIFIC LOCATIONS THAT WILL FOG IN AND THOSE THAT WON`T.
THOSE THAT DO END UP WITH FOG OR LOW CLOUDS WILL SEE SLIGHTLY
COOLER DAYTIME HIGHS AND SLIGHTLY WARMER NIGHTTIME LOWS. ALL WILL
DEPEND ON THE STRUGGLE BETWEEN THE INVERSION AND THE DOWNSLOPING
FLOW

ALSO IN REGARDS TO  TEMPERATURES, THE OFFSHORE FLOW AND WARMER
AIR MASS WILL RESULT IN HIGHER THAN NORMAL TEMPERATURES FOR MOST,
IF NOT ALL, OF THE REGION. AREA RIDGELINES, ESPECIALLY THOSE ABOVE
THE INVERSION AND WELL INTO THE SUBSIDING EASTERLY FLOW, WILL BE
WELL ABOVE NORMAL. THESE LOCATIONS INCLUDE AREAS WITH EXTENSIVE
SNOWPACK, SO SOME MELTING IS LIKELY, AND AREA CREEKS AND STREAMS
WILL CONTINUE TO RUN SWIFT AND HIGH.

THIS SAME WARM AND DRY PATTERN WITH OVERNIGHT VALLEY FOG WILL
CONTINUE INTO THE MIDDLE OF THE WEEK, BUT THE PATTERN WILL BEGIN
TO SHIFT A BIT BY THE END OF THE SHORT TERM AS THE UPPER LEVEL
RIDGE SHIFTS EAST, AND SOUTHWEST FLOW MOVE IN OVER THE FORECAST
AREA. WITH MOISTURE BEGINNING TO PUSH IN AHEAD OF AN APPROACHING
LONG WAVE TROUGH, CLOUD COVER WILL INCREASE, ALONG WITH THE
CHANCES FOR SOME LIGHT PRECIPITATION. THE RIDGE SHOULD BE
RESILIENT ENOUGH TO HOLD THE BULK OF THE RAINFALL AT BAY UNTIL THE
LONG TERM, BUT SOME LIGHT SHOWERS ARE POSSIBLE AT THE IMMEDIATE
COAST WEDNESDAY NIGHT. -BPN

LONG TERM...THURSDAY THROUGH SUNDAY NIGHT...THE UPPER RIDGE
CONTINUES TO HANG TOUGH ON THURSDAY, BUT THE RIDGE AXIS IS
EXPECTED TO SHIFT EAST INTO IDAHO AS A SHORTWAVE TROUGH ROUNDS THE
BASE OF THE LARGE UPPER TROUGH IN THE GULF OF ALASKA. THIS WILL
BRING INCREASING CLOUDS OVER THE AREA, BUT GIVEN THE RIDGE IS
STILL RATHER STRONG, ANY SYSTEM THAT MOVES UP FROM THE SOUTHWEST
WILL WEAKEN. FOR NOW KEPT IN A SLIGHT CHANCE OF RAIN OVER THE
WATERS AND SLIGHT CHANCE AT THE COAST, BUT PRETTY CONFIDENT IT
WILL REMAIN DRY INLAND. THE MODELS SHOW THE STORM TRACK INCHING
CLOSER TO OUR AREA ON FRIDAY, BUT THE UPPER RIDGE WILL BE SLOW TO
MOVE OUT. GIVEN THE POSITION OF THE UPPER TROUGH, SUSPECT THE GFS
AND EC MAY BE A OVERDONE WITH THE QPF FIELD. ESPECIALLY FOR INLAND
LOCATIONS. THE COAST AND MARINE WATERS MAY HAVE THE BEST CHANCE AT
GETTING ANYTHING, BUT FOR NOW WE`LL KEEP A CHANCE POPS MAINLY WEST
OF THE CASCADES.

THE UPPER TROUGH SWINGS THROUGH THE AREA SATURDAY WITH RIDGING
BUILDING BACK ON SUNDAY. THE MODELS DISAGREE WITH THE AMOUNT OF
RIDGING ON SUNDAY, SO THIS LENDS TO A LOWER CONFIDENCE ON HOW
MUCH, IF ANY PRECIPITATION WE`LL GET. -PETRUCELLI

AVIATION...FOR THE 07/18Z TAF CYCLE...VFR CONDITIONS WILL CONTINUE
THROUGH THIS EVENING AND INTO TONIGHT. OFFSHORE FLOW IS EXPECTED TO
BE SLIGHTLY STRONGER COMPARED TO LAST NIGHT BRINGING ENOUGH DRY AIR
WHICH SHOULD PREVENT OR AT LEAST LIMIT LOW CLOUD AND FOG FORMATION.
THE EXCEPTION WILL BE IN ROSEBURG WHERE LOW CLOUDS AND FOG ARE
EXPECTED TO DEVELOP BETWEEN 7-9Z AND CONTINUE THROUGH MONDAY
MORNING. COULD NOT RULE OUT PATCHY SHALLOW FOG IN MEDFORD TOWARDS
15Z, BUT CONDITIONS SHOULD REMAIN VFR. -PETRUCELLI

MARINE...UPDATED 200 PM PST SAT FEB 6 2016...A WEAK THERMAL TROUGH
ALONG THE COAST IS BRINGING LIGHT NORTHEAST WINDS. LIGHT EAST TO
NORTHEAST WINDS WILL PERSIST THROUGH MONDAY.  WINDS WILL BECOME
SOUTH MONDAY EVENING AS LOW PRESSURE DEEPENS BEYOND 130W. STEEP SEAS
DOMINATED BY A LONG PERIOD WEST SWELL WILL BUILD INTO THE WATERS
MONDAY AS A LONG PERIOD WEST SWELL OF AROUND 10 FEET AT 16 SECONDS
BUILDS INTO THE WATERS.

A FRONT MAY NEAR THE COASTAL WATERS LATE WEDNESDAY THEN MOVE INTO
THE WATERS THURSDAY INTO EARLY FRIDAY. MODELS CONTINUE TO SHOW
VARIABILITY WITH THE STRENGTH AND TIMING OF THIS FRONTAL SYSTEM
THOUGH AND CONFIDENCE IS LOW TO MODERATE ON DETAILS FOR WAVE AND
WIND FORECASTS DURING THIS PERIOD. OVERALL, EXPECT AN INCREASE IN
SEAS LATE WEDNESDAY AND THURSDAY, WITH THE POTENTIAL FOR STEEP SEAS
DURING THIS PERIOD AND A SLIGHT CHANCE FOR SMALL CRAFT ADVISORY
LEVEL WINDS. ANOTHER STEEP LONG PERIOD SWELL IS EXPECTED TO MOVE
INTO THE WATERS THURSDAY NIGHT AND FRIDAY. /CC

&&

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

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 4 AM TO 10 PM PST
     MONDAY FOR PZZ350-356-370-376.

$$

FJB/MAP/CC


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