Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 281139 AAA
AFDMFR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MEDFORD OR
439 AM PDT MON JUL 28 2014

UPDATED AVIATION AND MARINE SECTIONS

.DISCUSSION...AN ACTIVE PATTERN CONTINUES ON TRACK THROUGH MUCH OF
THE WEEK. A COMBINATION OF AN UPPER LEVEL LOW OFFSHORE AND A
UPPER HIGH OVER THE GREAT BASIN COMBINE TO FUNNEL MOISTURE INTO
THE REGION AS WELL AS COOLER AIR ALOFT TO BRING INSTABILITY TO THE
REGION INTO THE WEEKEND. TODAY WILL SEE NOT NEARLY AS MUCH CLOUD
COVER INLAND EXCEPT FOR SOME LINGERING HIGH CLOUDS ON THE FAR
EAST SIDE. BOTH THE GFS AND NAM HAVE GOOD INSTABILITY ON THE WEST
SIDE...BUT THE 700-500 RH IS BELOW 30 PERCENT AND HAVE CUT BACK
CHANCES TO THE CASCADES AND EAST SIDE. TUESDAY IS LOOKING MORE
FAVORABLE OVER THE AREA AND THE WEST SIDE. UNLIKE OTHER DAYS THAT
HAVE HAD INSTABILITY TO THE SOUTH EARLY WHICH RESULTED IN
EXTENSIVE CLOUD COVER INHIBITING CONVECTIVE DEVELOPMENT THE AREA OF
INSTABILITY IS JUST TO THE SOUTH OF THE REGION. THE NAM AND GFS
BOTH INDICATE LI`S IN THE -3 TO -4 RANGE. THE MORNING STARTS WITH
A SHORT WAVE MOVING INTO MODOC COUNTY AROUND 18Z WITH STRONG
PVA...BUT INSTABILITY IS WEAK WITH THE BEST CONVECTION NEEDING
SURFACE SUPPORT AND HAVE GONE CHANCE POPS WITH A SLIGHT CHANCE OF
THUNDERSTORMS IN THAT AREA. BY 00Z THE BEST PVA IS ON THE EAST
SIDE IN THE WEAKER INSTABILITY COMBINING WITH GOOD THETA-E
CONVERGENCE...AND THE BEST INSTABILITY OVER THE WEST SIDE WITH
WEAKER PVA BUT VERY GOOD 850-700 MB THETA-E CONVERGENCE. WITH THE
WEAK SW 0-6KM FLOW STORMS MAY LATCH ONTO TERRAIN AT TIMES AND
WITH PW VALUES SHOWING AROUND 1.2 INCHES AM THINKING THERE WILL BE
A HIT OR MISS CELL OR THREE THAT MAY BE VERY GOOD RAIN AND
LIGHTNING PRODUCERS WOBBLING UP THE WEST SIDE TUESDAY AFTERNOON
INTO THE EVENING...WITH GREATER COVERAGE OF CELLS ON THE EAST SIDE
AND IN THE CASCADES. BY WEDNESDAY THE FLOW BECOMES MORE
SOUTHWESTERLY SHUNTING THE INSTABILITY AND CONVECTION TO THE
CASCADES AND EAST SIDE. SVEN

&&

.AVIATION...BASED ON THE 28/12Z TAFS...

IFR/LIFR CIGS AND FOG WILL IMPACT THE IMMEDIATE COAST AND COASTAL
VALLEYS FROM THE LOWER UMPQUA RIVER VALLEY NEAR REEDSPORT SOUTHWARD
TO CAPE BLANCO. EXPECT AREAS OF LIFR CIGS TO ALSO FORM ALONG THE
SOUTH COAST NEAR BROOKINGS AND GOLD BEACH THIS MORNING, THOUGH THERE
MAY ALSO BE A CLEAR AREA AROUND PORT ORFORD. CIGS SHOULD LIFT TO VFR
MOST AREAS ALONG THE COAST FROM 16-18Z. EXPECT GUSTY NORTH WINDS IN
THE AFTERNOON/EARLY EVENING BEFORE IFR/LIFR CONDITIONS RETURN DURING
THE LATE EVENING AND OVERNIGHT. THE REST OF THE AREA WILL HAVE VFR,
THOUGH MID-LEVEL MOISTURE WILL INCREASE THIS AFTERNOON WITH ISOLATED
THUNDERSTORMS FROM THE CASCADES EASTWARD IN OREGON AND IN MODOC
COUNTY IN NORTHERN CALIFORNIA. SPILDE

&&

.MARINE...UPDATED 430 AM PDT 28 JULY 2014...

MODELS REMAIN IN AGREEMENT THAT THE CURRENT PATTERN WITH SOME SLIGHT
DAY-TO-DAY VARIATION WILL PERSIST THIS WEEK. HIGH PRESSURE IS
CENTERED OFFSHORE AND A THERMAL TROUGH IS OVER NORTHERN CALIFORNIA
WHICH WILL CONTINUE TO RESULT IN STEEP WIND WAVE DOMINATED SEAS. THE
STRONGEST WINDS WILL OCCUR IN THE OUTER WATERS SOUTH OF CAPE BLANCO
AND DURING THE AFTERNOON AND EVENING HOURS. A VERY SLIGHT WEAKENING
IN THE PRESSURE GRADIENT WILL PERSIST THROUGH WEDNESDAY, THEN WIND
SPEEDS AND SEAS ARE FORECAST TO INCREASE A BIT THURSDAY INTO FRIDAY.
SPILDE

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 AM
     PDT THURSDAY FOR PZZ356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 AM PDT THURSDAY
     FOR PZZ356.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 8 PM PDT THIS EVENING FOR
     PZZ350-370.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 AM PDT THURSDAY
     FOR PZZ350-370-376.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 AM PDT THURSDAY FOR
     PZZ376.

$$

SBN/MAS






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