918
FXHW60 PHFO 171230
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
230 AM HST THU APR 17 2025
SYNOPSIS
A CONVECTIVE PATTERN WITH MOSTLY LIGHT WINDS WILL HOLD IN PLACE
DURING THE NEXT COUPLE DAYS, WITH SHOWERS FAVORING AREAS NEAR THE
COAST AT NIGHT AND THE ISLAND INTERIORS DURING THE AFTERNOON AND
EVENING HOURS. LIGHT TO MODERATE TRADE WINDS WILL RETURN OVER THE
WEEKEND INTO EARLY NEXT WEEK, HOWEVER LINGERING MOISTURE WILL
LIKELY KEEP THE PATTERN RATHER SHOWERY, EVEN IN LEEWARD AREAS AT
TIMES. A NEW STORM SYSTEM DEVELOPING WEST OF THE STATE COULD BRING
SOUTHERLY WINDS ALONG WITH ANOTHER CHANCE FOR HEAVY RAINFALL AND
THUNDERSTORMS TO THE ISLANDS TUESDAY AND WEDNESDAY.
DISCUSSION
CURRENTLY AT THE SURFACE, A WEAKENING STATIONARY FRONT IS LOCATED
AROUND 350 MILES NORTHWEST OF KAUAI, WITH BROAD TROUGHING NOW
PRESENT OVER THE ISLAND CHAIN. MEANWHILE, A 1029 MB HIGH IS
CENTERED TO THE DISTANT NORTH-NORTHEAST. WINDS ARE LIGHT AND
VARIABLE ACROSS THE WESTERN ISLANDS, WHILE LIGHT TO MODERATE
EAST-SOUTHEASTERLIES ARE PRESENT IN UNSHELTERED SECTIONS OF MAUI
COUNTY AND THE BIG ISLAND. INFRARED SATELLITE IMAGERY SHOWS
MOSTLY CLOUDY CONDITIONS IN PLACE, WITH RADAR IMAGERY SHOWING A
FEW SHOWERS NEAR THE COASTS OF THE ISLANDS, WITH MOST ACTIVITY
OVER THE COASTAL WATERS. MAIN SHORT TERM FOCUS REVOLVES AROUND THE
POTENTIAL FOR HEAVY RAIN AND THUNDERSTORMS DURING THE NEXT COUPLE
DAYS.
BROAD TROUGHING WILL HOLD IN PLACE DURING THE NEXT COUPLE DAYS,
KEEPING LAND AND SEA BREEZES COMMON OVER THE WESTERN END OF THE
STATE. LIGHT TO MODERATE EAST-SOUTHEAST WINDS WILL PERSIST OVER
THE EASTERN ISLANDS, WITH LAND AND SEA BREEZES COMMON IN THE MORE
TERRAIN SHELTERED AREAS. THE BROAD TROUGHING WILL DAMPEN OUT BY
LATE FRIDAY, ALLOWING LIGHT TO MODERATE TRADE WINDS TO FILL BACK
IN ACROSS THE STATE FRIDAY NIGHT AND PERSIST THROUGH EARLY NEXT
WEEK. A DEVELOPING STORM SYSTEM WEST OF THE ISLANDS COULD BRING
MODERATE SOUTHERLY WINDS TO THE AREAS TUESDAY AND NEXT WEDNESDAY.
AS FOR THE REMAINING WEATHER DETAILS, A CONVECTIVE PATTERN IS
EXPECTED TO CONTINUE THROUGH FRIDAY, WITH SHOWERS FAVORING AREAS
NEAR THE COAST AND NIGHT AND THE ISLAND INTERIORS DURING THE
AFTERNOON AND EVENING HOURS. AN UPPER LEVEL TROUGH WILL MOVE
SLOWLY EASTWARD ACROSS THE STATE TODAY THROUGH FRIDAY, WITH 500
MB TEMPERATURES OF -12 TO -14C AND PRECIPITABLE WATER VALUES
HOVERING AROUND 1.5 INCHES. THIS IS EXPECTED TO BRING SOME HEAVIER
SHOWERS TO THE AREA DURING THE AFTERNOON AND EVENING HOURS. IN
ADDITION, ISOLATED THUNDERSTORMS WILL REMAIN POSSIBLE AS THE COLD
POOL ALOFT MOVES EASTWARD ACROSS THE STATE, AND SOME SNOW IS
EXPECTED ACROSS THE HIGH ELEVATION SUMMITS OF THE BIG ISLAND AS
WELL. AS A RESULT, A WINTER WEATHER ADVISORY IS NOW IN EFFECT FROM
NOON TODAY THROUGH 6 PM FRIDAY FOR ELEVATIONS ABOVE 11,000 FEET.
THE UPPER LEVEL TROUGH WILL LINGER NEAR THE BIG ISLAND THROUGH
THE WEEKEND, SO A THUNDERSTORM OR TWO COULD DEVELOP HERE EACH
AFTERNOON. ELSEWHERE, WE SHOULD SEE A HYBRID TRADE WIND PATTERN
RETURN. PRECIPITABLE WATER VALUES CONTINUE TO HOLD CLOSE TO 1.5
INCHES AND THE LATEST MODEL TRENDS HAVE BEEN FOR WEAKER TRADES. AS
A RESULT, THE PATTERN LOOKS A BIT SHOWERY THROUGH THE WEEKEND,
WITH CHANCES FOR SHOWERS EACH AFTERNOON AND EVENING IN MOST
LEEWARD AREAS AS WELL. A NEW STORM SYSTEM MAY BRING ANOTHER ROUND
OF HEAVY RAIN AND THUNDERSTORMS TO THE ISLANDS TUESDAY AND
WEDNESDAY.
AVIATION
A STALLED FRONTAL BOUNDARY NORTHWEST OF KAUAI, ALONG WITH BROAD
TROUGHING OVER THE ISLAND CHAIN, WILL LEAD TO LIGHT AND VARIABLE
WINDS ACROSS KAUAI AND OAHU THIS TODAY, WITH LIGHT TO MODERATE
SOUTHEAST FLOW PREVAILING ELSEWHERE. UNSTABLE CONDITIONS ALOFT
WILL BRING HEAVIER SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
OVER OAHU AND KAUAI THIS MORNING, BECOMING A STATEWIDE THREAT BY
LATE MORNING AND INTO THE AFTERNOON. LOCALIZED IFR CIG/VIS IN
+TSRA/+SHRA MAY ACCOMPANY ANY OF THE MORE ROBUST ACTIVITY.
LIGHT FLOW WILL LEAD TO A SEA BREEZE/LAND BREEZE PATTERN THROUGH
THE NEXT SEVERAL DAYS.
MARINE
LIGHT TO MODERATE EAST-SOUTHEAST WINDS WILL PERSIST INTO FRIDAY
AS A STALLED FRONT SLOWLY DIMINISHES TO THE WEST. OVER THE
WESTERN END OF THE ISLANDS, THE LIGHT WINDS WILL ALLOW A LAND AND
SEA BREEZE PATTERN TO DEVELOP NEAR THE COASTS. FOR THE EASTERN
END, LIGHT TO MODERATE EAST TO SOUTHEAST BREEZES, WITH LOCALIZED
FRESH POCKETS, WILL LIKELY PERSIST, PARTICULARLY AROUND THE BIG
ISLAND. A RETURN TO MODERATE EASTERLY TRADES IS POSSIBLE BY THE
WEEKEND AS HIGH PRESSURE BUILDS TO THE NORTH. HEAVY SHOWERS AND
THUNDERSTORMS WILL REMAIN POSSIBLE INTO FRIDAY DUE TO AN UPPER
DISTURBANCE IN THE AREA.
SURF ALONG EXPOSED NORTH AND WEST FACING SHORES WILL TREND UP
LATER TODAY AS A FRESH NORTH-NORTHWEST ARRIVES AND BUILDS DOWN
THE ISLAND CHAIN. OBSERVATIONS AT THE OFFSHORE BUOYS TO THE
NORTHWEST STARTED TRENDING UP AROUND MIDNIGHT, WHICH SHOULD
START SHOWING AT EXPOSED SHORES ON KAUAI BY NOON, THEN TO OAHU AND
MAUI COUNTY THIS AFTERNOON INTO TONIGHT. SURF MAY NEAR THE
ADVISORY LEVELS FOR EXPOSED NORTH AND WEST FACING SHORES TONIGHT
INTO FRIDAY AS THIS SWELL PEAKS. A DOWNWARD TREND IS THEN EXPECTED
OVER THE WEEKEND, WITH THE SWELL SHIFTING OUT OF NORTH.
SURF ALONG EAST FACING SHORES WILL REMAIN BELOW THE APRIL AVERAGE
THROUGH AT LEAST SATURDAY, THEN STEADILY RISE TO AROUND AVERAGE
BY EARLY NEXT WEEK.
SURF ALONG SOUTH FACING SHORES WILL REMAIN SMALL, WITH MAINLY
OVERLAPPING BACKGROUND SOUTH SWELLS MOVING THROUGH. A LARGER PULSE
OF SOUTH-SOUTHWEST SWELL MAY ARRIVE TUESDAY.
HFO WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY FROM NOON TODAY TO 6 PM HST FRIDAY FOR
BIG ISLAND SUMMITS.
DISCUSSION...JELSEMA
AVIATION...THOMAS
MARINE...GIBBS
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