Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 262229
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
329 PM PDT TUE MAY 26 2015

.SYNOPSIS...LINGERING INSTABILITY ACROSS EASTERN TRINITY COUNTY
WILL BRING THE POSSIBILITY OF THUNDERSTORMS THROUGH THIS EVENING.
OTHERWISE DRY WEATHER WILL CONTINUE TO PREVAIL THROUGH THE WEEK.

&&

.SHORT TERM...(THROUGH FRIDAY) AN UPPER LEVEL SHORTWAVE IS ADVANCING
TOWARD NORTHWEST CALIFORNIA AND MAY TRIGGER SOME AFTERNOON/EVENING
STORMS OVER TRINITY COUNTY TODAY. MODEL SOUNDINGS ARE VERY SIMILAR
TO YESTERDAY SO IT WOULD NOT BE A SURPRISE THAT A STRONG OR SEVERE
STORM FORMS. HOWEVER THE SHORTWAVE TODAY IS NOT AS STRONG...WILL
MOVE INTO THE AREA MORE IN THE EVENING THAN AFTERNOON HOURS...AND
HAS A MORE NORTHERLY TRAJECTORY. THUS EVEN THOUGH THE MODEL
SOUNDINGS ARE SIMILAR THERE IS STILL CONSIDERABLE UNCERTAINTY AS TO
HOW MANY SHOWERS/STORMS FORM TODAY. AS THE AFTERNOON HEAT WANES THIS
EVENING INSTABILITY WILL DECREASE AND ANY SHOWERS/STORMS THAT DO
FORM WILL DISSIPATE FOR THE OVERNIGHT HOURS.

COASTAL STRATUS HAS REMAINED PERSISTENT THOUGH SOME BETTER MIXING
HAS ALLOWED THE DEL NORTE COAST TO PARTIALLY CLEAR OUT. THERE IS
POTENTIAL FOR A BRIEF PERIOD OF SUNSHINE EVEN IN THE HUMBOLDT BAY
AREA BEFORE THE CLOUDS EXPAND AGAIN ALONG THE COAST AND SPREAD
INLAND OVERNIGHT. WITH AN UPPER LEVEL RIDGE BEGINNING TO MOVE OVER
THE WEST COAST THE MARINE LAYER SHOULD COMPACT SOME TONIGHT WITH THE
POTENTIAL FOR MORE FOG ALONG THE COAST. A REPEAT ON TUESDAY IS
ANTICIPATED ON WEDNESDAY FOLLOWED BY EVEN A HIGHER LIKELIHOOD OF FOG
WEDNESDAY NIGHT INTO THURSDAY.

AS THE RIDGE BUILDS OVERHEAD ON WEDNESDAY A WARM LAYER WILL MOVE
OVERHEAD RESULTING IN A DECENT CAPPING INVERSION ACROSS THE REGION.
THUS VERY LITTLE IF ANY CONVECTIVE DEVELOPMENT IS ANTICIPATED
WEDNESDAY AFTERNOON AND EVENING. OPTED TO REMOVE THE SHOWER AND
THUNDERSTORM CHANCES FROM THE FORECAST WITH THIS UPDATE FOR
WEDNESDAY.

AN UPPER LEVEL SHORTWAVE ON THE EAST SIDE OF A CUT OFF UPPER LEVEL
LOW OFF THE CALIFORNIA COAST WILL MOVE TOWARD NORTHWEST CALIFORNIA
ON THURSDAY. THIS SHORTWAVE MAY POSSIBLY RESULT IN SOME COOLER AIR
ALOFT AND A TRIGGER TO OVERCOME THE LOW LEVEL INVERSION THURSDAY
AFTERNOON IN THE TRINITY COUNTY MOUNTAINS. THUS SLIGHT CHANCES FOR
THUNDERSTORMS HAVE BEEN MAINTAINED FOR THURSDAY AFTERNOON AND A
REPEAT MAY OCCUR FRIDAY AFTERNOON. /RPA

.LONG TERM (SATURDAY THRU MONDAY)...THE BROAD BRUSH UPPER LEVEL FLOW
IS FORECAST TO HAVE AN AMPLIFIED RIDGE STATIONED OVER THE WEST COAST
BRINGING ABOVE NORMAL TEMPERATURES TO INTERIOR AREAS THIS WEEKEND. A
SHORTWAVE TROUGH WILL SLIDE UNDER THE LONGWAVE RIDGE BRINGING AN
INFLUX OF MOISTURE TO THE REGION AND SOME SHOWER ACTIVITY FOR FAR
EASTERN DEL NORTE, TRINITY, AND NE MENDOCINO COUNTIES. WE`RE STILL
ANALYZING THE POTENTIAL THREAT FOR AFTERNOON THUNDERSTORMS THIS
WEEKEND AS THE APPROACHING SHORTWAVE TROUGH INCREASES MOISTURE OVER
NORTHWEST CALIFORNIA. ADDITIONALLY, LOW LEVEL INSTABILITY AND CAPE
VALUES LOOK FAVORABLE FOR STORM DEVELOPMENT ESPECIALLY IN TRINITY
COUNTY. HOWEVER, STORMS DO NOT TYPICALLY DEVELOP UNDER A SW FLOW
REGIME AND A WEAK CAP IS FORECAST TO DEVELOP WHICH SHOULD DISCOURAGE
THE DEVELOPMENT OF DEEP CONVECTION. FOR NOW, HAVE LEFT THUNDERSTORMS
OUT OF THE LONG TERM FORECAST. MOVING INTO EARLY NEXT WEEK
TEMPERATURES SHOULD RETURN TO NEAR NORMAL AS THE UPPER RIDGE
FLATTENS OUT AND THE FLOW BECOMES MORE ZONAL. /KML


&&

.AVIATION...STRATUS ALONG THE COAST HAS REMAINED PERSISTENT
...PARTICULARLY ON THE MENDOCINO COAST. SOME MIXING HAS OCCURRED
NORTH OF THE CAPE AND MAY BRING A PERIOD OF VFR TO CEC AND ACV
BEFORE THE STRATUS EXPANDS AGAIN AND MOVES INLAND THIS
EVENING/OVERNIGHT. CLOUDS MAY REACH UKI ONCE AGAIN TONIGHT THOUGH
THERE IS SOME UNCERTAINTY WITH THE MARINE LAYER EXPECTED TO BECOME
MORE COMPRESSED AS A RIDGE BUILDS OVERHEAD. ANY CLOUDS THAT PUSH
INLAND WILL QUICKLY DISSIPATE WEDNESDAY MORNING LEAVING VFR FOR THE
INTERIOR AND IFR OR LIFR NEAR THE COAST FOR MUCH OF THE DAY. /RPA


&&

.MARINE...NORTHERLY WINDS WILL CONTINUE THROUGH THE WEEK AS A RIDGE
OF HIGH PRESSURE REMAINS STATIONED JUST OFFSHORE. SMALL CRAFT
ADVISORIES MAY NEED TO BE EXTENDED WITH THE UPDATE TONIGHT BUT THERE
IS STILL UNCERTAINTY IN THE COVERAGE OF SMALL CRAFT WINDS. EITHER
WAY CONDITIONS WILL BE BORDERLINE HAZARDOUS AS FORECASTED WINDS WILL
BE SKIRTING LOW END CRITERIA LEVELS THIS WEEK. STEEP SEAS WILL
PERSIST IN RESPONSE TO THE FRESH WINDS. OTHERWISE A SOUTH, SOUTHWEST
WAVE GROUP WILL IMPACT THE WATERS AS A LOW PRESSURE SYSTEM
APPROACHES CALIFORNIA AND A NORTHWEST SWELL WILL DIMINISH THROUGH
THE WEEK. /KML


&&

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

&&

$$

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