Flash Flood Warning 17, NWS Honolulu, HI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST THU MAR 8 2012

.SYNOPSIS...
A DEEP UPPER LEVEL TROUGH IS FORECAST TO KEEP THE WEATHER UNSETTLED
THROUGH SATURDAY...WHILE A STRONG HIGH PRESSURE SYSTEM FAR NORTHWEST
OF THE STATE MAINTAIN STRONG AND GUSTY TRADES INTO EARLY NEXT WEEK.
ALL ISLANDS WILL BE VULNERABLE FOR HEAVY SHOWERS AND THUNDERSTORMS
THROUGH FRIDAY NIGHT. EXPECT THE HEAVY WEATHER TO LESSEN SATURDAY...
WITH A RETURN TO MORE TYPICAL TRADE WIND WEATHER FOR THE NEW WORK
WEEK.

&&

.DISCUSSION...
HEAVY SHOWERS HAVE ALREADY BEEN FOUND OVER WINDWARD PORTIONS OF THE
BIG ISLAND...MAUI AND MOLOKAI THIS EVENING. ADDITIONAL SHOWERS ARE
STARTING TO FORM OVER WINDWARD OAHU AS WELL.

THE OVERALL FORECAST PHILOSOPHY REMAINS THE SAME. AN UPPER LEVEL LOW
WILL FORM TO THE NORTHWEST OF KAUAI ALONG THE EXISTING UPPER LEVEL
TROUGH. WE HAVE A SURFACE BOUNDARY NEAR MAUI THIS EVENING WHICH IS
EXPECTED TO STRENGTHEN WITH THE HELP OF THE CLOSED UPPER LEVEL LOW.
THIS COMBINATION IS WHAT IS HELPING TO SPARK THE HEAVY SHOWERS...AND
WITH THE INTENSIFICATION EXPECTED OVERNIGHT...WILL LEAD TO MORE
SHOWER DEVELOPMENT.

AS MENTIONED...THERE HAVE ALREADY BEEN SOME THUNDERSTORMS WITH THIS
SYSTEM...MAINLY ALONG A LINE NORTHEAST OF THE BIG ISLAND TO
SOUTHWEST OF THE BIG ISLAND. THE SURFACE FEATURE IS EXPECTED TO WORK
ITS WAY TO THE WEST...WHICH WILL BRING THE THREAT OF THUNDERSTORMS
AND HEAVY RAIN WITH IT. AS THE FEATURE DEVELOPS...WE/LL SEE THE AREA
AFFECTED BY HEAVY SHOWERS EXPAND.

OVERNIGHT THE GREATEST THREAT WILL BE TO MAUI COUNTY...WITH SOME
THINGS FIRING OVER PARTS OF THE BIG ISLAND AND OAHU FROM TIME TO
TIME. BY MORNING...WE EXPECT KAUAI TO BE GETTING IT AS WELL. STILL
EXPECTING THE BULK OF THE EVENT TO BE FELT FRIDAY AND FRIDAY...SO
THE FLASH FLOOD WATCH CONTINUES THROUGH 6 AM SATURDAY.

THE WIND ADVISORY CONTINUES TONIGHT FOR LANAI...FOR THE NORTH WINDS
BEING FUNNELED THROUGH THE PAILOLO CHANNEL. EXPECT THE WINDS TO
BECOME MORE EASTERLY TONIGHT...WHICH SHOULD ALLOW THE WINDS ON LANAI
TO DIE DOWN. OTHER AREAS OF THE SMALLER ISLANDS HAVE BEEN ON THE
WINDY SIDE...BUT OVERALL IT STILL APPEARS WINDS ARE BELOW ADVISORY
CRITERIA. WILL CONTINUE TO MONITOR OVERNIGHT OF COURSE.

A WINTER WEATHER ADVISORY IS IN PLACE FOR THE BIG ISLAND SUMMITS.
LAYERED CLOUDS ASSOCIATED WITH THUNDERSTORMS NEAR THE SUMMITS WILL
BRING MOISTURE TO THE SUMMITS...AND WITH TEMPERATURES AT OR BELOW
FREEZING...EXPECT ANYTHING TO FALL IN A WINTRY MIX. THE BIG ISLAND
SHOULD BE THE FIRST TO GET OUT OF THE CURRENT WEATHER PATTERN LATER
TOMORROW...SO THE ADVISORY GOES THROUGH FRIDAY AFTERNOON.

&&

.AVIATION...
TAFS REMAIN ON THE PESSIMISTIC SIDE GIVEN THE WIDESPREAD +RA AND
ISOL/SCAT TSRA OVER MUCH OF THE AREA. CONDITIONS ARE EXPECTED TO
DETERIORATE FURTHER OVER THE NEXT 24 HOURS. GUSTY NE WINDS AND
PERIODIC LOW VIS/CIGS ARE LIKELY IN THE CRITICAL PERIOD AND LONGER
TERM. A WIND ADVISORY REMAINS IN EFFECT FOR LANAI THROUGH
TONIGHT...SO EXPECT PHNY TO BE VERY WINDY.

AIRMETS REMAIN POSTED FOR IFR CONDITIONS OVER SOME MT AREAS...LLVL
TURB AND ICING IN ANY CONVECTION AND THE PRECIP LAYERS. THESE WILL
CONTINUE WILL SLIGHT MODIFICATIONS AS THE WEATHER EVOLVES...AND
PUSHES TO THE EAST.

SIGMET ROMEO ALSO REMAINS IN EFFECT EXTENDING FROM THE WINDWARD MAUI
COUNTY WATERS NEWD ALONG THE MAINLAND ROUTES FOR ABOUT 800 NM.
CONVECTION MAY BECOME ISOL AT TIMES...BUT GIVEN THE HIGH TRAFFIC
AREA THE SIGMET WILL LIKELY REMAIN FOR A WHILE.

&&

.MARINE...
THE WAVE WATCH INDICATES A RISING SHORT PERIOD EAST SWELL TONIGHT.
THUS A HIGH SURF ADVISORY HAS BEEN POSTED FOR THE EAST FACING
SHORES OF ALL ISLANDS UNTIL 4 PM HST FRIDAY.

THE SMALL CRAFT ADVISORY WILL REMAIN IN EFFECT FOR ALL HAWAIIAN
WATERS FOR WINDS AND/OR COMBINED SEAS...WITH THESE CONDITIONS
EXPECTED THROUGH AT LEAST SATURDAY MORNING.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH FOR MAUI MOLOKAI LANAI OAHU KAUAI UNTIL 6 AM HST
SATURDAY.

SMALL CRAFT ADVISORY UNTIL 6 AM HST SATURDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY FOR THE EAST FACING SHORES TO UNTIL 4 PM HST
FRIDAY.

WINTER WEATHER ADVISORY FOR THE BIG ISLAND SUMMITS UNTIL 4 PM HST
FRIDAY.

WIND ADVISORY FOR THE ISLAND OF LANAI UNTIL 4 AM HST FRIDAY.

&&