Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 282235
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
335 PM PDT MON JUL 28 2014

.SYNOPSIS...A STRONG UPPER RIDGE OVER NW CALIFORNIA WILL CONTINUE
TO BRING HOT TEMPERATURES TO THE INTERIOR...WHILE THE COAST SITS
UNDER LOW CLOUDS AND FOG. INCREASING MOISTURE WILL LEAD TO A
SLIGHT CHANCE OF THUNDERSTORMS OVER THE INTERIOR MOUNTAINS TUESDAY
AND WEDNESDAY AFTERNOONS.


&&

.SHORT TERM...(THRU THU) UPPER LEVEL RIDGING BUILDING OVER NORTHWEST
CALIFORNIA AND DRY AIR ALOFT HAVE RESTRICTED TOWERING CUMULUS GROWTH
TODAY. MONSOONAL MOISTURE WILL INCREASE OVERNIGHT INTO TUESDAY
BRINGING BETTER INSTABILITY TO THE AREA AND CHANCES FOR
THUNDERSTORMS OVER THE INTERIOR MOUNTAINS FOR TUESDAY AFTERNOON. THE
HRRR MODEL INDICATES THAT LIGHT SHOWERS WILL LIKELY DEVELOP
OVERNIGHT OVER THE SAN FRANCISCO BAY AREA AND SLIDE NORTH IN THE
MORNING HOURS. THESE SHOWERS MAY BRING SOME SPRINKLES OR VERY LIGHT
RAIN TO MENDOCINO COUNTY BUT AT THIS TIME THUNDERSTORMS ARE NOT
ANTICIPATED FROM THIS ACTIVITY. BY THE AFTERNOON THE INSTABILITY
WILL INCREASE AND THE BEST MOISTURE WILL MOVE FARTHER NORTH OVER
TRINITY COUNTY. THE NAM...GFS...AND ECMWF ALL INDICATE THE
POTENTIAL FOR STORMS...POSSIBLY MORE WIDESPREAD THAN CURRENTLY
FORECAST IF THE NAM IS CORRECT. MODERATE 0-6 KM SHEAR MAY ALLOW
ANY STORMS THAT FORM TO MAINTAIN THEMSELVES AND DRIFT OFF TO THE
NORTHEAST. THUS POPS HAVE BEEN INCREASED ACROSS THE VALLEYS OF
TRINITY COUNTY AS WELL.

BY THE EVENING INSTABILITY WILL WANE AND STORMS SHOULD DIMINISH.
WARM AIR ALOFT WILL RE-ESTABLISH ITSELF ON WEDNESDAY AND THURSDAY
LEADING TO LESSER CHANCES FOR STORMS WITH A STRONGER LOW LEVEL
INVERSION/CAP. AT THIS TIME THE CAP APPEARS TO NOW BE STRONGEST ON
THURSDAY...SO HAVE OPTED TO REMOVE THE CHANCES FOR STORMS ALL
TOGETHER FOR THAT AFTERNOON.

AFTERNOON HIGH TEMPERATURES WILL REMAIN SEVERAL DEGREES ABOVE
NORMAL ACROSS THE INTERIOR WITH UPPER LEVEL RIDGING OVER THE
WESTERN UNITED STATES. A STRONG MARINE INVERSION HAS ALLOWED
STRATUS TO BECOME WIDESPREAD OVER THE COAST WATERS. DISSIPATING
THE MARINE INVERSION WILL BE DIFFICULT CONSIDERING THE WARM AIR
ALOFT. THUS THE COASTAL CLOUDS ARE ANTICIPATED TO REMAIN IN
PLACE FOR AT LEAST THE NEXT FEW DAYS. THE STRATUS MAY LIFT SOME
AND REDUCE THE THICKNESS OF THE FOG LATER THIS WEEK AS UPPER LEVEL
SHORTWAVES MOVE OVERHEAD ON THE WEST SIDE OF THE RIDGE. RPA

.LONG TERM...(FRI THROUGH MON) GFS CONTINUES TO INDICATE HIGH
PWATS AS WELL AS FAVORABLE CONVECTIVE PARAMETERS FOR STORMS OVER
THE NORTHERN ZONES THROUGH THE FORECAST PERIOD. BOTH THE ECMWF AND
GFS HAVE AN UPPER TROUGH/LOW APPROACHING THE COAST THIS WEEKEND.
THE APPROACH OF THIS TROUGH SHOULD HELP TO WEAKEN THE STABLE MID
LAYER...THOUGH THERE IS VIRTUALLY NO COOLING ALOFT INDICATED IN
THE MODEL DATA. THERE IS STILL A LOT OF UNCERTAINTY DUE TO THE
PRESENCE OF THIS STABLE MID LAYER WHICH MAY CAP THE CONVECTION.
FOR NOW I WILL CONTINUE WITH A BROAD BRUSH FORECAST OF A SLIGHT
CHANCE OF THUNDERSTORMS EACH AFTERNOON AND EVENING. 850MB
TEMPERATURES DO NOT CHANGE MUCH THROUGH THE PERIOD AND ANY CHANGES
WILL MOST LIKELY RESULT FROM MORE CLOUD COVER AND/OR MARINE AIR
FILTERING INLAND. THE FORECAST ALONG THE COAST HAS BEEN BASED
LARGELY ON CLIMATOLOGY AND PERSISTENCE.


&&

.AVIATION...FOG IS WIDESPREAD ALONG THE COAST WITH A VERY STRONG
MARINE INVERSION IN PLACE. THIS FOG WILL MOVE FARTHER ONSHORE THIS
EVENING ALLOWING LIFR CONDITIONS TO EXPAND ALONG THE IMMEDIATE
COAST. A REPEAT OF TODAY IS EXPECTED TOMORROW FOR COASTAL
TERMINALS WITH THE FOG PULLING BACK TO THE IMMEDIATE COAST IN THE
LATE MORNING AND AFTERNOON.

VFR WILL PREVAIL ACROSS THE INTERIOR. THE ONLY CONCERN WILL BE
ISOLATED SHOWERS AND THUNDERSTORMS DURING THE AFTERNOON HOURS
WHICH MAY BRING SOME LOCALIZED TURBULENCE.


&&

.MARINE...HIGH PRESSURE OFFSHORE COUPLED WITH A THERMAL TROUGH
OVER THE NORCAL INTERIOR WILL MAINTAIN MODERATE NORTHERLY WINDS
ACROSS THE OUTER WATERS THROUGH THE FORECAST PERIOD. THE NORTHERLY
WINDS WILL CONTINUE TO PRODUCE SHORT PERIOD NORTHERLY WAVES THROUGH
THIS WEEK. ADVISORIES IN THE OUTER WATERS HAVE BEEN MAINTAINED FOR
STEEP SEAS OF 7-9 FT AT 8 SECONDS. WINDS SHOULD INCREASE AROUND MID
WEEK AS THE GRADIENT TIGHTENS IN RESPONSE TO STRENGTHENING HIGH
PRESSURE OFFSHORE. SEAS SHOULD COME UP LATER IN THE WEEK AS WELL.

ONCE AGAIN SMALL SCALE EDDIES HAVE FORMED NEAR THE COAST
TODAY...BOTH NORTH AND SOUTH OF THE CAPE. THESE EDDIES HAVE
BEEN CREATING MOSTLY LIGHT SOUTHERLY WINDS NEAR SHORE. THE
MODELS...EVEN THE HIGH RESOLUTION MODELS...HAVE NOT BEEN DOING
VERY WELL CAPTURING THESE SMALL SCALE VORTICES. I ADJUSTED THE WIND
FIELDS NEAR SHORE TO ACCOUNT FOR THE LIGHT SOUTHERLIES ACROSS THE
INNER WATERS.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
    SMALL CRAFT ADVISORY UNTIL 11 PM PDT FRIDAY PZZ470-475.

&&

$$

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