Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 050219
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
419 PM HST WED MAR 4 2015

.SYNOPSIS...
A TROUGH ALOFT AND TROPICAL MOISTURE NEAR THE SURFACE WILL
CONTINUE PERIODS OF RAIN AND ISOLATED THUNDERSTORMS THROUGH
TONIGHT OVER MAUI COUNTY AND THE BIG ISLAND. SNOW AND INCREASING
WINDS WILL ALSO AFFECT THE BIG ISLAND SUMMITS. A STRONG SURFACE
HIGH TO THE NORTHWEST WILL BRING BREEZY TRADE WINDS INTO THE
WEEKEND AND SCATTERED SHOWERS WILL AFFECT MAINLY WINDWARD AREAS.
THE THREAT OF HEAVY RAIN DECREASES OVER MAUI AND THE BIG ISLAND
THURSDAY MORNING BUT WILL INCREASE AGAIN SUNDAY AND MONDAY.

&&

.DISCUSSION...

A PLUME OF MOISTURE FROM THE DEEP TROPICS AND AN UPPER LEVEL
TROUGH ARE BRINGING STEADY RAINS AND ISOLATED THUNDERSTORMS TO
THE BIG ISLAND AND MAUI. THE AFTERNOON HILO SOUNDING SHOWS A DECREASE IN
PRECIPITABLE WATER FROM LAST NIGHT... DROPPING FROM 2.15 TO 1.50
INCHES... ALTHOUGH THE HIGH VALUE LAST NIGHT CAN BE TEMPERED
SOMEWHAT AS THE SOUNDING WAS LIKELY RAIN CONTAMINATED. THE
SOUNDING ALSO SHOWS UPPER LEVEL WINDS OF 100 MPH TURNING FROM WSW
LAST NIGHT TO WEST THIS AFTERNOON INDICATING THE UPPER TROUGH IS
CONTINUING ITS WESTWARD MOTION.

RADAR AND OBSERVATIONS SHOW STRATIFORM RAIN WITH EMBEDDED MODERATE SHOWERS
FROM MOLOKAI TO THE BIG ISLAND THIS AFTERNOON WITH SNOW FALLING AT THE
HIGHEST ELEVATIONS OF THE BIG ISLAND. THIS SCENARIO WILL CONTINUE
INTO TONIGHT WITH A FLASH FLOOD WATCH FOR MAUI AND THE BIG ISLAND... AND
A WINTER STORM WARNING FOR THE BIG SUMMITS BOTH IN EFFECT UNTIL 6
AM THURSDAY MORNING. KAUAI AND OAHU ARE MAINLY DRY WITH LAYERED
MID AND UPPER CLOUDS JUST CLEARING KAUAI AS OF 4 PM THIS
AFTERNOON. THE CLEARING SKIES WILL CONTINUE EASTWARD OVER OAHU
TONIGHT AND MAUI COUNTY AND THE BIG ISLAND THURSDAY. THE UPPER
TROUGH WILL PUSH WEST OF THE AREA THURSDAY MORNING EASING THE
FLASH FLOOD THREAT AND POTENTIAL FOR SNOW ON THE SUMMITS.

AT THE SURFACE... EAST WINDS OVER MAUI COUNTY AND THE BIG ISLAND ARE
PUSHING THE TROPICAL MOISTURE INTO WINDWARD SLOPES WITH A SURFACE
TROUGH LOCATED NEAR THE BIG ISLAND EXTENDING TO THE NORTH. A
STRONG HIGH PRESSURE LOCATED FAR NW OF THE STATE IS PUSHING BREEZY
NNE WINDS OVER KAUAI AND OAHU BRINGING IN MUCH DRIER AIR AS
INDICATED BY THE AFTERNOON LIHUE SOUNDING WHICH RECORDED A DRY
1.02 INCHES OF PRECIPITABLE WATER. THE DRY AND GUSTY NNE WINDS
WILL SHUNT THE TROPICAL MOISTURE SOUTH OF THE BIG ISLAND THURSDAY
AS THE UPPER TROUGH EXITS TO THE EAST ALLOWING RAINFALL COVERAGE
AND INTENSITY TO DECREASE OVER THE EASTERN HALF OF THE STATE.

NNE TRADES WILL CONTINUE INTO THE WEEKEND WITH THE TRADES PUSHING SHOWERS
INTO THE WINDWARD AREAS. DECREASING WINDS ARE EXPECTED SUNDAY AS A
SURFACE TROUGH FORMS NORTH OF THE BIG ISLAND AND AN UPPER TROUGH
SWINGS IN FROM THE NORTHWEST OVER THE STATE. THE WEAKENING WINDS
WILL ALLOW TROPICAL MOISTURE TO AGAIN INFILTRATE THE BIG ISLAND
AND POSSIBLY MAUI AREAS... INCREASING THE CHANCE OF RAIN WITH THE
POSSIBILITY OF HEAVY SHOWERS. UNDER THIS SCENARIO DRIER WEATHER
WOULD REMAIN OVER THE WESTERN HALF OF THE STATE.

A LARGE-SCALE TROUGH ALOFT WILL PERSIST NORTH OF THE ISLANDS
THROUGH NEXT WEEK. THE MOST ACTIVE PERIODS WILL COME AS SHORT
WAVE TROUGHS WITHIN THE PARENT TROUGH MOVE OVER THE ISLANDS FROM THE
NORTHWEST. MODELS ARE IN FAIR AGREEMENT WITH A SUNDAY/MONDAY
SHORTWAVE SWINGING OVER THE AREA WITH THE NEXT ONE COMING THROUGH
WEDNESDAY/THURSDAY.

&&

.AVIATION...
AIRMET TANGO CONTINUES FOR HIGH LEVEL TURBULENCE ACROSS THE AREA AS
AN UPPER LEVEL TROUGH REMAINS IN PLACE NORTH OF THE MAIN HAWAIIAN
ISLANDS. THE UPPER LEVEL TURBULENCE WILL LIKELY CONTINUE THROUGH
TONIGHT. FOR MAUI COUNTY AND THE BIG ISLAND...AIRMET SIERRA REMAINS
IN EFFECT FOR MTN OBSC OVER WINDWARD AREAS. LAYERED HIGH CLOUDS ARE
ALSO PRODUCING LIGHT ICING OVER THOSE ISLANDS...FOR WHICH AIRMET
ZULU REMAINS IN EFFECT. FOR OAHU AND KAUAI...EXPECT PERIODS OF ISOL
MVFR CIGS MAINLY OVER WINDWARD AREAS...OTHERWISE VFR SHOULD PREVAIL.

&&

.MARINE...
THERE IS A SLIGHT CHANCE OF THUNDERSTORMS OVER THE COASTAL WATERS
AROUND THE BIG ISLAND AND MAUI THROUGH TONIGHT. A SMALL CRAFT
ADVISORY IS IN EFFECT FOR STRONG TRADE WINDS AND ROUGH SEAS OVER
THE WINDIER COASTAL WATERS. ROUGH SURF WILL BUILD ALONG EAST FACING
SHORES...AND THIS SURF COULD REQUIRE A HIGH SURF ADVISORY LATER IN
THE WEEK. OTHERWISE...SURF IS EXPECTED TO REMAIN BELOW THE
ADVISORY THRESHOLDS THROUGH THE WEEK. A NORTH SWELL ARRIVING
SUNDAY MAY PRODUCE ADVISORY LEVEL SURF ALONG THE NORTH FACING
SHORES.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR MAUI-KONA-SOUTH BIG
ISLAND-BIG ISLAND NORTH AND EAST-KOHALA-BIG ISLAND INTERIOR.

WINTER STORM WARNING UNTIL 6 AM HST THURSDAY FOR BIG ISLAND
SUMMITS.

SMALL CRAFT ADVISORY UNTIL 6 AM HST SATURDAY FOR KAUAI NORTHWEST
WATERS-KAUAI LEEWARD WATERS-KAUAI CHANNEL-KAIWI CHANNEL-MAALAEA
BAY-PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-
BIG ISLAND SOUTHEAST WATERS.


&&

$$

MORRISON...DISCUSSION AND MARINE
REYNES...AVIATION






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