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115 FXPQ50 PGUM 190601 AFDGUM Area Forecast Discussion National Weather Service Tiyan GU 401 PM ChST Thu Jun 19 2025 .Marianas Synopsis... Satellite and radar observations show a few clouds with isolated showers across the Marianas. Ritidian and Ipan buoys show combined seas between 2 and 4 feet. && .Discussion... The dry trade-wind pattern continues across the region. Isolated thunderstorms remain in the forecast for Friday. However, Both MIMIC TPW and Blended TPW show PWATS below 2.00 inches across the Marianas today, which aligns with this morning's upper air sounding. Both MIMIC and Blended TPW show PWATS as low as 1.75 inches moving into the Marianas. Although thunderstorms are still possible at these PWATS, without a forcing mechanism to assist in convective development, confidence is low in thunderstorms occurring tomorrow. For now, thunderstorms remain for consistency, but it may need to be removed with the next forecast update if PWATs continue to trend drier. Looking ahead, there are signs that the pattern may flip back to being very active towards the middle and end of next week. It's too early to get into the details, but both the GEFS and EPS are starting to show increased precipitation across the Marianas. For now, handled the end of the period with 30% PoPs, but changes are likely as we approach the latter half of next week. && .Marine... Marine conditions remain benign with combined seas between 2 to 4 feet. Combined seas look to remain steady over the next several days. That said, models appear to hint towards a slight increase in trade swell sometime this weekend, while winds remain light. This could allow surf to rise and lead to the risk of rip currents to briefly become moderate along east facing reefs. && .Eastern Micronesia... An active pattern will develop across eastern Micronesia through the weekend into next week. Multiple surface troughs will pass west across the region through a convergence zone. In addition, upper- level winds will increase at times as the Tropical Upper-Tropospheric Trough (TUTT) occasionally dips south, enhancing the lift and instability across the region. Expect generally scattered showers and isolated thunderstorms through the period, with Probability of Precipitation (PoPs) fluctuating between 30 to 40 percent through early weekend. Showers could become high-end scattered to possibly numerous at times (PoPs 50-60 percent) late weekend into next week as the models are showing the Inter-Tropical Convergence becoming better developed and creeping north towards the forecast points. Combined seas of 4 to 6 feet will dip 1 to 2 feet through the weekend for Pohnpei and Kosrae as the trade swell subsides, but look to linger for Majuro as the trade swell remains slightly elevated. As the ITCZ creeps north next week, the background south to southeast swell looks to increase. Combined seas and surf along south-facing reefs/beaches could rise slightly as a result. Winds will remain gentle to moderate for the period. && .Western Micronesia... A generally unsettled weather pattern persists across far western Micronesia. A surface convergence boundary is focusing scattered to numerous showers and isolated thunderstorms over and west of the Republic of Palau, as a trade-wind trough moves in from over Yap State. Scattered showers are seen near and west of Yap Proper, but look to be gradually diminishing this afternoon. Palau will likely remain in an area of convergence and shower development through later tonight, but both locations will see a gradual easing of showers tonight through the remainder of the week, with coverage possibly dropping to isolated at times this weekend. To the east, isolated to scattered showers are seen near Chuuk with a series of outflow boundaries crossing the area from east to west. Chuuk Lagoon can expect on-and-off scattered showers through the next few days as it remains just on the outer periphery of the features causing them. A disorganized ITCZ looks to briefly build north into the area around Friday, diminish this weekend, before re-emerging Monday. Models suggest a more robust ITCZ disturbance or two may cross the area next week, sometime during the midweek onward. There was little to no change to the marine forecast. Benign marine conditions continue, with combined seas of around 3 to 4 feet near Palau and Yap, and 4 to 6 feet near Chuuk, expected to gradually diminish about a foot or so over the next few days. Mostly gentle winds persist for Palau and Yap, with moderate to fresh winds over Chuuk waters tonight expected to diminish to gentle to moderate through the weekend. && .GUM WATCHES/WARNINGS/ADVISORIES... GU...None. MP...None. Marianas Waters...None. && $$ Marianas: Williams East Micronesia: Slagle West Micronesia: DeCou