337
FXHW60 PHFO 180645
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
845 PM HST TUE MAR 17 2026
SYNOPSIS
A WEATHER PATTERN FEATURING LIGHT WINDS, MOSTLY CLOUDY SKIES, AND
SCATTERED TO NUMEROUS SHOWERS WILL CONTINUE THROUGH THE MIDDLE
PART OF THE WEEK, WITH THE GREATEST MOISTURE RESIDING OVER
PORTIONS OF MAUI COUNTY AND THE BIG ISLAND. THE WEATHER WILL ONCE
AGAIN BECOME MORE ACTIVE DURING THE LATTER PART OF THE WEEK AS A
NEW LOW DEVELOPS, BRINGING RENEWED CHANCES FOR HEAVY RAIN AND
MODERATE KONA WINDS. GIVEN THE HIGH SOIL SATURATION FROM THE
RECENT KONA STORM, EVEN MODERATE RAINFALL RATES COULD POSE A RISK
FOR RAPID RUNOFF AND FLOODING, ESPECIALLY FROM FRIDAY INTO THE
WEEKEND.
DISCUSSION
ISSUED AT 840 PM HST TUE MAR 17 2026
THIS EVENING, A BAND OF SHOWERS WITH PREDOMINATELY LIGHT TO
MODERATE RAIN RATES IS SEEN ON RADAR AND SATELLITE IMAGERY MOVING
ACROSS PORTIONS OF EAST MAUI AND THE BIG ISLAND. THESE SHOWERS ARE
ASSOCIATED WITH A LOW-LEVEL TROUGH THAT IS MOVING THROUGH THIS
EVENING. AS THE TROUGH MOVES FARTHER AWAY FROM MAUI, EXPECT
IMPROVING CONDITIONS THERE, THOUGH LATEST HI-RES GUIDANCE DEPICTS
LINGERING SHOWERS AND LOW CLOUDS OVER MUCH OF THE BIG ISLAND
THROUGHOUT THE REST OF THE NIGHT AND INTO EARLY WEDNESDAY MORNING.
THE AFTERNOON 00Z SOUNDING AT HILO ALSO SHOWED SOME INSTABILITY
OVER THE WESTERN END OF THE STATE, WHICH WAS REALIZED IN THE FORM
OF A FEW ISOLATED THUNDERSTORMS NEAR THE HILO AREA AND IN THE BIG
ISLAND WINDWARD COASTAL WATERS THIS EVENING. ELSEWHERE, DRIER
CONDITIONS ARE OBSERVED THIS EVENING FROM KAUAI TO MOLOKAI, WHERE
RAIN GAUGE NETWORKS SHOW VERY LITTLE RAIN HAS FALLEN OVER THE PAST
SEVERAL HOURS. THE FORECAST HAS UNDERGONE A SIGNIFICANT UPDATE
THIS EVENING TO BRING SHOWER CHANCES, QPF, AND WINDS CLOSER IN
LINE WITH THE LATEST OBSERVATIONS AND SHORT-TERM MODEL GUIDANCE.
AS THE PREVIOUS DISCUSSION MENTIONED, THE STATE CONTINUES TO
RESIDE BENEATH A LARGE UPPER-LEVEL TROUGHING PATTERN, WHICH
CONTINUES TO TRANSPORT MOISTURE-RICH AIR INTO THE REGION.
PRECIPITABLE WATER VALUES IN EXCESS OF 2 INCHES CONTINUE TO RESIDE
OVER THE ISLANDS, AS SEEN ON CIMSS PRECIPITABLE WATER IMAGERY, AS
WELL AS IN THE AFTERNOON UPPER AIR SOUNDING AT HILO. DESPITE THE
RICH MOISTURE IN THE REGION WITH SCATTERED TO NUMEROUS SCATTERED
SHOWERS POSSIBLE, THE MIDDLE OF THE WEEK WILL STILL LIKELY BE THE
DRIEST PORTION OF THE FORECAST, AHEAD OF THE NEXT LOW PRESSURE
SYSTEM FORMING NEARBY. WINDS WILL BE RELATIVELY LIGHT AND VARIABLE
THROUGH WEDNESDAY NIGHT.
BY THE LATTER PART OF THIS WEEK, THE UPPER-LEVEL WINDS WILL BECOME
STRONGER AND A TROUGH WILL DEEPEN INTO A LOW JUST WEST OF THE
STATE. ONCE AGAIN, A RICH PLUME OF DEEP TROPICAL MOISTURE WILL BE
DRAWN OVER THE ISLANDS, ESPECIALLY THE EASTERN HALF OF THE STATE
OVER MAUI COUNTY AND THE BIG ISLAND, AND WILL MARK THE RETURN OF
SOUTH TO SOUTHWESTERLY SURFACE FLOW (KONA WINDS). AS A RESULT,
SHOWER CHANCES WILL INCREASE SIGNIFICANTLY AGAIN BEGINNING FOR
SOME AREAS ON THURSDAY AND LASTING INTO THE WEEKEND, INCLUDING
THE POTENTIAL FOR HEAVY RAIN AND FLOODING. THE LATEST MODEL
GUIDANCE CONTINUES TO SUPPORT AN ADDITIONAL SEVERAL INCHES OF
RAINFALL POSSIBLE OVER PORTIONS OF THE STATE DURING THIS PERIOD.
WHILE THIS NEXT SYSTEM IS NOT ANTICIPATED TO BE AS INTENSE AS THE
RECENT KONA STORM EVENT, IT IS IMPORTANT TO NOTE THAT IT WILL
IMPACT AN ALREADY HIGHLY SATURATED ENVIRONMENT.
GIVEN THE ANTECEDENT CONDITIONS, INCLUDING ELEVATED STREAMS AND
SATURATED SOILS, EVEN MODERATE RAINFALL RATES MAY QUICKLY LEAD TO
RUNOFF ISSUES. THE THREAT FOR FLASH FLOODING WILL BECOME ELEVATED
STATEWIDE BY FRIDAY, WITH THE POTENTIAL FOR MORE SIGNIFICANT
IMPACTS PERSISTING THROUGH THE WEEKEND. WE WILL CONTINUE TO REFINE
THE FORECAST OVER THE NEXT COUPLE OF DAYS AS DETAILS BECOME MORE
CLEAR.
AVIATION
ISSUED AT 840 PM HST TUE MAR 17 2026
A LOW LEVEL TROUGH PASSING THROUGH MAUI AND THE BIG ISLAND THIS
EVENING WILL CONTINUE TO DRIFT EASTWARD AWAY FROM MAUI OVER THE
NEXT FEW HOURS. WEATHER CONDITIONS WILL IMPROVE OVER MAUI AS THIS
TROUGH BRINGS MORE RAIN AND LOW CEILINGS INTO THE BIG ISLAND
TONIGHT. EXPECT CONTINUED MVFR CONDITIONS OVER KONA AND HILO
AIRPORTS THROUGH THE MORNING HOURS. LANAI AIRPORT MAY ALSO SEE
MVFR TO IFR CONDITIONS AS THESE SATURATED CONDITIONS CAN PRODUCE
AREAS OF FOG OVER THE ISLAND THROUGH THE EARLY MORNING HOURS.
AIRMET SIERRA REMAINS IN EFFECT FOR MOUNTAIN OBSCURATION OVER
MOLOKAI, LANAI, MAUI, AND THE BIG ISLAND AT OR ABOVE 015. NO
OTHER AIRMETS ARE CURRENTLY IN EFFECT.
LIGHT ICING LINGERS IN CLOUDS WITH THE FREEZING LEVEL AROUND 140.
MARINE
ISSUED AT 840 PM HST TUE MAR 17 2026
LIGHT AND VARIABLE WINDS PREVAIL THROUGH MIDWEEK, WITH DAYTIME SEA
BREEZES AND OVERNIGHT LAND BREEZES NEAR THE COASTS. A RIDGE
BUILDING TO THE NORTH OF THE STATE WILL GRADUALLY VEER TO THE
SOUTH BY THURSDAY INTO THE WEEKEND. BY THIS WEEKEND, A WEAK LOW
APPROACHING FROM THE WEST TRAVERSES ACROSS THE STATE AND BEGINS TO
LIFT NORTH ON SATURDAY, WHICH APPEARS LIKELY TO MAINTAIN LIGHT TO
MODERATE SOUTHERLY WINDS FOR THE AREA.
A HIGH SURF ADVISORY IS IN EFFECT FOR NORTH FACING SHORES OF
KAUAI, OAHU, MOLOKAI AND MAUI THROUGH TONIGHT AS THE NORTH-
NORTHWEST SWELL PEAKS TONIGHT. SURF WILL GRADUALLY DECLINE INTO
FRIDAY AS THE SWELL SHIFTS OUT OF THE NORTH AND NORTH-NORTHEAST
THROUGH FRIDAY. A NEW SMALL TO MODERATE LONG PERIOD WEST-
NORTHWEST SWELL IS EXPECTED TO ARRIVE SATURDAY AND HOLD THROUGH
EARLY NEXT WEEK.
SURF ALONG SOUTH SHORES HAS TRENDED UP TODAY AS A FRESH LONG
PERIOD SOUTH SWELL IS EXPECTED TO PEAK WEDNESDAY THEN GRADUALLY
EASE INTO THE WEEKEND. SURF ALONG EAST FACING SHORES WILL REMAIN
WELL BELOW AVERAGE DUE TO THE LACK OF TRADES LOCALLY AND UPSTREAM.
THE EXCEPTION WILL BE FOR EAST FACING SHORES EXPOSED TO NORTH-
NORTHEAST SWELLS EXPECTED LATER THIS WEEK.
HFO WATCHES/WARNINGS/ADVISORIES
HIGH SURF ADVISORY UNTIL 6 AM HST WEDNESDAY FOR NORTH FACING
SHORES OF NIIHAU, KAUAI, OAHU, MOLOKAI, AND MAUI.
DISCUSSION...VAUGHAN
AVIATION...BOHLIN
MARINE...SHIGESATO
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