634
FXHW01 KWNH 250852
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
452 AM EDT SUN OCT 25 2026
VALID 00Z MON 26 OCT 2026 - 00Z MON 02 NOV 2026
A WEAK BOUNDARY DROPPING SOUTH WILL KEEP LIGHT NORTHEASTERLY FLOW
ACROSS THE REGION AND WINDWARD SHOWERS ACROSS MAUI AND THE BIG
ISLAND THROUGH MONDAY.
THEREAFTER, MORE IMPACTFUL WEATHER IS STILL LIKELY TO IMPACT
PORTIONS OF THE STATE BY TUESDAY INTO WEDNESDAY WITH AREAS OF
HEAVY RAINFALL AND FLASH FLOODING POSSIBLE. A WEAK WAVE OF LOW
PRESSURE ALONG AN ELONGATED TROUGH AXIS SHOULD MOVE ACROSS THE
STATE DURING THIS TIMEFRAME, BRINGING AN INCREASE IN FORCING AND
SOUTHEASTERLY LOW LEVEL WINDS AND MOISTURE TRANSPORT. FAVORABLE
RIGHT ENTRANCE REGION UPPER JET DYNAMICS, AND PWS INCREASING
TOWARDS 2.5" WILL ALSO SUPPORT HEAVY RAINFALL, AND WITH SOME WEAK
INSTABILITY FORECAST, THUNDERSTORMS ARE ALSO A POSSIBILITY. WHILE
SOME UNCERTAINTY WITH THE EXACT DETAILS REMAIN, MODELS ARE
STARTING TO COME INTO BETTER AGREEMENT. THIS INITIAL SURGE OF
FORCING SHOULD BE FAIRLY QUICK MOVING, IMPACTING THE STATE TUESDAY
INTO WEDNESDAY, AND SHOULD FEATURE A MORE WIDESPREAD AREA OF
SHOWERS AND THUNDERSTORMS WITH HEAVY RAINFALL, WITH MODELS
CLUSTERING IN AN AXIS FROM OAHU TO THE BIG ISLAND. MODEL QPF IS A
TOUCH DOWN FROM EARLIER CYCLES, BUT GIVEN THE MOISTURE, FORCING
AND INSTABILITY FORECAST, LOCALLY HEAVIER TOTALS ARE STILL
ANTICIPATED, AND AT LEAST SOME FLASH FLOODING IS PROBABLE.
BY LATE WEDNESDAY INTO SATURDAY THIS MORE WIDESPREAD CONVECTION
SHOULD EXIT THE REGION, WITH A WEAKENING OF THE OVERALL FORCING.
HOWEVER, PWS WILL REMAIN ELEVATED AND THE TROUGH AXIS WILL REMAIN
NEARBY. THUS, WHILE PROBABLY NOT AS WIDESPREAD, PERIODS OF
LOCALLY HEAVY RAINFALL WILL REMAIN POSSIBLE OVER THE STATE, WITH
THE BEST CHANCES ACROSS THE WINDWARD PORTIONS OF MAUI AND THE BIG
ISLAND.
CHENARD
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