219
FXHW01 KWNH 180831
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
331 AM EST THU DEC 18 2025
VALID 00Z FRI 19 DEC 2025 - 00Z FRI 26 DEC 2025
AN UNSETTLED PATTERN WILL CONTINUE THROUGH THE START OF THE PERIOD
AS AN UPPER-LEVEL LOW REMAINS IN POSITION TO THE NORTH,
KEEPING THE EASTERN EDGE OF A BROAD TROUGH OVER THE ISLANDS. AT
THE SURFACE, A STALLED BUT WEAKENING COLD FRONT WILL MAINTAIN
UNSTABLE CONDITIONS THROUGH FRIDAY. AS A FOCUS FOR ENHANCED LOW-
LEVEL MOISTURE CONVERGENCE, THE FRONT WILL SUPPORT ADDITIONAL
CHANCES FOR HEAVY RAINFALL ACROSS NI'IHAU, KAUAI, AND OAHU. HIGH-
RESOLUTION GUIDANCE FROM THE HREF REINFORCES THIS THREAT,
INDICATING ELEVATED PROBABILITIES FOR ADDITIONAL RAINFALL TOTALS
EXCEEDING 2 INCHES BETWEEN 00Z FRIDAY AND 00Z SATURDAY.
THE TRANSITION TOWARD A MORE STABLE REGIME IS EXPECTED BY THE
WEEKEND AS THE UPPER LOW WEAKENS AND LIFTS NORTHEASTWARD. AN UPPER
RIDGE IS FORECAST TO BUILD IN ITS WAKE AND REMAIN IN PLACE ACROSS
THE ISLANDS THROUGH THE MIDDLE OF NEXT WEEK. MEANWHILE, SURFACE
RIDGING BUILDING IN FROM THE NORTH WILL HERALD THE RETURN OF A
MORE STANDARD TRADE WIND REGIME. EXPECT MODERATE TO FRESH
EASTERLY TRADES TO FOCUS TYPICAL PASSING SHOWERS ALONG THE
WINDWARD SLOPES.
PEREIRA
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