Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
733 FXHW60 PHFO 211751 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 751 AM HST Fri Nov 21 2025 .UPDATE... Updated the shower chances for today to reflect current observations and guidance. && .SYNOPSIS... A wet morning for many under mostly overcast skies and breezy trades. Shower activity and winds will both continue to decline into Saturday. Typical trade weather this weekend where showers will favor windward areas with the occasional shower making it into the lee. Weather will trend more wet going into the middle of next week as weak troughs passing north of Hawaii draw up more moisture-rich southerly air and bring it across the state. && .PREV DISCUSSION.../ISSUED 520 AM HST Fri Nov 21 2025/ A fairly active radar this morning as a moist air mass is currently passing over the island chain. Quick hitting light to moderate showers caught within moderate offshore trades have put down a few tenths of an inch of rain since midnight...quarter inch totals being measured over a handful of windward Kauai, Oahu and Big Island communities. A swath of mid to upper level clouds moving up from the southwest within weak upper troughing that is residing in the vicinity of the state will create a milky day. A jet stream level shortwave trough passing through to the east will draw up higher mid layer moisture and guarantee greater shower frequency and a more overcast day. This shortwave does not appear that it will produce a great deal of instability, but under the weakened trade wind flow, it could trigger a few afternoon showers over more leeward terrain. Partially to mainly overcast skies, along with the mixing provided by light easterly breezes, will regulate temperatures by a few degrees and promise a relatively comfortable afternoon and evening. A 1032 mb surface high is centered approximately 1400 miles northeast of Hawaii will maintain light to moderate trades across most of the interior and nearshore waters into Sunday. The next high moving in from the west will replace this high early next week and briefly weaken the downstream pressure gradient, subtly weakening winds heading toward Thanksgiving Day. Upper ridging from the west will expand eastward across the Central Pacific as weak troughing rides in from the west between the 30N and 40N parallels. Weak ridging will be the alpha feature and maintain order in the form of stability in the days leading up to the holiday. This equates to light to moderate trades and windward- focused showers early next week. Stubborn passing troughs far north of the state may dig further south from Tuesday night onward into next weekend. This features may draw up higher equatorial moisture and increase rain probabilities from Tuesday night onward. A deeper trough may descend and dig in the vicinity of the islands around Thanksgiving. Numerical weather prediction models are in disagreement on the location of this trough next Friday but do agree that a cold front may reach the western waters next weekend. While uncertainty is low on the timing and location of the front, confidence is just high enough to mention a slight probability of a cold front sitting on our western doorstep this Thanksgiving holiday weekend. && .AVIATION... Mid to high clouds continue to move from the southwest to northeast across the state within upper troughing. Primarily VFR categories as frequent passing showers get caught up within moderate to occasionally strong trade winds. Occasional MVFR cats over windward and mountains within lowered overcast and showers. Lower level trades will begin to weaken Friday evening into Saturday morning. AIRMET Sierra is in effect from Molokai to Kauai N thru SE sections for tempo mountain obscuration from low decks and light precipitation. These conditions will continue through early Saturday morning. AIRMET Tango is in effect due to lee side terrain low level turbulence. This will be ongoing through at least Saturday morning. AIRMET Zulu update for light to moderate icing from Kauai to Maui. Evening PIREPS have reported light to moderate riming just north of Maui and Oahu within the 150-FL230 layer. && .MARINE... High pressure far northeast will continue to drift eastward through the weekend as a front passes north of the waters. Fresh to locally strong trade winds will gradually ease through the forecast period. The Small Craft Advisory (SCA) has been trimmed and extended to the windier waters and channels around Maui County and the Big Island through tonight. A new high pressure building in north of the waters this weekend will continue to move east and keep trade winds in the gentle to locally fresh range through the early part of next week. The current northwest swell will continue to decline and plateau later today at small to moderate levels. A small to moderate long period northwest swell is expected to start building in this afternoon and keep surf heights elevated over the weekend near High Surf Advisory (HSA) levels for north and west facing shores. Long period forerunners have started to fill in from this new swell slowly this morning at the NDBC 51101 buoy northwest of the islands. A slight reinforcement of similar magnitude is expected from the northwest, building in Saturday, and peaking Saturday evening into Sunday. In the long range, a potentially larger northwest swell is expected around the middle of next week. Stay tuned for more details as the low starts to develop to the far northwest of the islands. As the trade winds gradually weaken over the coastal waters and upstream of the islands, the current rough and choppy surf along east facing shores will slowly decline into the weekend and into early next week. Surf along south facing shores will decline today as the south-southeast swell eases. Surf looks to remain tiny to small through the forecast period with tiny background southerly energy. && .FIRE WEATHER... Critical fire weather conditions are not expected through the weekend. Breezy, relatively wet trades will create elevated afternoon humidity levels today. Rainfall behavior and trade winds will drop off going into early Saturday. Light to moderate trade winds and fairly stable conditions are forecast through early next week. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Saturday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ UPDATE...Tsamous DISCUSSION...Blood AVIATION...Blood MARINE...Shigesato