####018010237#### FXCA62 TJSJ 180711 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 311 AM AST Tue Aug 18 2026 ...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST, FIRE WEATHER... .KEY MESSAGES... Issued at 248 AM AST Tue Aug 18 2026 - Dry conditions will persist today as a drier air mass dominates the region, limiting the shower activity across the islands. - A Heat Advisory is in effect from 10 AM to 5 PM AST for urban and coastal areas of Puerto Rico and the U.S. Virgin Islands. - By tonight into Wednesday, a vigorous tropical (formerly Invest 94L) will approach the islands, increasing the potential for showers and thunderstorms. - A low to moderate risk of rip currents is expected across local beaches throughout the workweek. && .Short Term(Today through Thursday)... Issued at 248 AM AST Tue Aug 18 2026 Fair weather conditions prevailed overnight across Puerto Rico and the U.S. Virgin Islands, as a dry, stable air mass continues to dominate the region. Once again, it was another warm night across the islands, with overnight lows in the upper 70s to low 80s across lower elevations and in the 70s across higher elevations. Winds were light and variable at 10 knots or less. Another dry, warm day is expected today; however, a gradual transition to a wetter, more unstable pattern is anticipated beginning this evening into Wednesday as a vigorous tropical wave (formerly Invest 94L) approaches the region. Precipitable water (PWAT) values will remain below normal today at 1.35 to 1.50 inches, limiting overall shower activity. Nevertheless, localized afternoon convective activity remains possible across portions of western and central Puerto Rico due to the combination of daytime heating and local effects. As the day progresses, PWAT values will gradually increase with the arrival of the tropical wave, increasing to above- normal values near 2.25 inches by Wednesday morning. This tropical wave is expected to interact with a deep-layer trough, increasing the potential for moderate to heavy rainfall and thunderstorms across the region. Recent model guidance continues to show some uncertainty regarding how much of the moisture will directly impact the islands, and the amount of rain. However, if the current forecast materializes, this setup will favor periods of moderate to locally heavy showers across the U.S. Virgin Islands and eastern Puerto Rico, followed by additional afternoon activity across interior and western Puerto Rico. Localized urban and small- stream flooding is possible if the heavy rainfall develops. Stronger thunderstorms could also produce frequent lightning and locally strong, gusty winds. Any rainfall associated with this wave would be beneficial given ongoing dry conditions across portions of the region, providing welcome relief. Please continue to monitor forecast updates closely today as conditions evolve. Following the wave's passage by Thursday, conditions will rapidly dry out as a drier, stable air mass establishes over the islands. This air mass, accompanied by low concentrations of Saharan dust, will persist through the weekend. An elevated heat risk will affect coastal and urban sections of Puerto Rico, Culebra, Vieques, and the U.S. Virgin Islands today, where a Heat Advisory remains in effect from 10 AM to 5 PM AST. These conditions significantly increase the risk of heat exhaustion and heat stroke, especially for young children, the elderly, and anyone spending extended time outdoors. Stay hydrated, limit direct sun exposure, and take frequent breaks in the shade or air conditioning. Brief relief from the hot temperatures is expected on Wednesday if the forecast materializes and cloudiness with widespread rain persists over the region. && .Long Term(Friday through Tuesday)... Issued at 248 AM AST Tue Aug 18 2026 Drier to seasonal conditions may persist this weekend, with uncertainty increasing by the end of the period. The wind pattern may vary, as a surface high building over the Western Atlantic will likely promote E-ENE winds on Friday, becoming from the E-ESE Sunday onwards as a weak tropical wave approaches the local area. Friday will likely be the "driest" day of the period, as model guidance suggests a drier airmass, along with concentrations of Saharan Dust, filtering into the region. Based on the latest deterministic guidance of the GFS and ECMWF, PWAT values should drop to below climatological normals (between 1.3 and 1.5 inches), as moisture content drops particularly in the mid levels (below 40%). Additionally, the proximity of a mid-level ridge (north of the Hispaniola) should lead to warmer-than-normal mid-level temperatures (500 mb temperatures up to -4 degrees Celsius), subsidence and stability aloft. Although daytime heating combined with local effects should trigger afternoon convection over the western side of Puerto Rico and local island streamers, rainfall accumulations will likely be limited under this pattern, resulting in no flooding threat. By Saturday, moisture content is likely to increase as a perturbation in the trades moves over the CWA, with PWAT values up to 1.80 inches, mainly observed in the 850 - 700 mb layer. Based on the latest model guidance, passing showers should move over windward sections of the islands, during the morning, with afternoon convection over interior and western Puerto Rico. With Saharan Dust concentrations diminishing, conditions look more favorable for showers, without ruling out isolated thunderstorms, over the aforementioned areas. Nevertheless, rainfall accumulations should lead to ponding of water over roadways and poorly drained areas. A similar pattern is expected on Sunday as lingering moisture and winds veering from the E-ESE may enhance deep convection over the northwestern side of Puerto Rico. Monday's forecast remains uncertainty as global model solutions suggests different outlook. From the latest GFS solution, a tropical wave moving over the Central Atlantic may become a cyclonic system and move northeast of the CWA, while the ECMWF's solution suggests that this system shifting northward, far away of the region. Therefore, uncertainty will remain high for the beginning of the next workweek. Seasonal to warmer-than-normal conditions are very likely in the long-term, with Sunday being the "hottest" day of the week as winds shift from the E-ESE. With the available moisture content, heat indices will very likely exceed 100 degrees Fahrenheit, particularly over urban and low-lying areas. Therefore, the heat threat will remain elevated to significant throughout the forecast period. Residents and visitors should stay hydrated and avoid prolonged outdoor activities. && .AVIATION... (06Z TAFS) Issued at 248 AM AST Tue Aug 18 2026 Mainly VFR conds expected across all TAF sites. Generally fair weather conditions will prevail across the region with aftn SHRA across western PR. Light winds at 10 kt or less through 18/13Z. Winds E-ESE at 10-15 kt with sea breeze variations and ocnl gusts up to 25 kt through 18/23Z. SHRA/VCSH expected to increase aft 18/23Z at TJSJ, TIST, TISX as a vigorous tropical wave approaches the islands. && .MARINE... Issued at 248 AM AST Tue Aug 18 2026 Light to moderate easterly trade winds will continue to prevail across the region over the next few days. Seas peaking up to 5 feet today will gradually ease to 2 to 4 feet later in the workweek. By late tonight into Wednesday, an approaching tropical wave will draw in deep moisture, increasing the potential for showers and thunderstorms across most local waters. This will elevate localized lightning hazards and bring gusty winds over the marine zones through midweek. Also, expect hazy skies across the northeastern Caribbean due to suspended Saharan dust, with higher concentrations after the wave passage. && .BEACH FORECAST... Issued at 248 AM AST Tue Aug 18 2026 A low to moderate risk of rip currents is expected through most of the workweek as seas continue to subside to around 2-3 feet across the coastal waters of the islands. However, remember that even when the risk is low, life-threatening rip currents can occur near groins, jetties, reefs, and piers. The lightning potential will increase on Wednesday due to thunderstorm activity associated with the arrival of a tropical wave. Low to moderate concentrations of Saharan dust will keep sky hazy before the wave passage, with higher concentrations expected from Thursday onward. && .FIRE WEATHER... Issued at 248 AM AST Tue Aug 18 2026 Critical fuel conditions persist across the islands, with extreme drought affecting portions of eastern Puerto Rico and the southern coastal plains. Dry conditions will persist across the region with low relative humidity, stressed vegetation, and dry fuels continuing to support elevated fire danger. The greatest concern remains across southern and southwestern Puerto Rico, where fuels are exceptionally dry and recent fire activity has been frequent. A gradual increase in moisture is expected later in the afternoon, as a vigorous tropical wave approaches the islands. Therefore, a Fire Danger Statement is in effect from 10 AM to 5 PM AST for the southern and southwestern plains of Puerto Rico. Residents and visitors are strongly urged to avoid outdoor burning, as conditions will easily support wildfire ignition and rapid spread. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon for PRZ001>005-007-008-010>013. VI...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon for VIZ001-002. AM...None. && $$ EVE SHIFT...DSR/MNG MID SHIFT...GRS ####018006368#### FXUS61 KAKQ 180711 AFDAKQ AREA FORECAST DISCUSSION National Weather Service Wakefield VA 311 AM EDT Tue Aug 18 2026 .WHAT HAS CHANGED... - Updated Discussion - A Heat Advisory has been issued for Bertie, Chowan, and Hertford NC for today. - Rain chances have increased for Thu-Sat, and the entire area has been highlighted in a Marginal Risk ERO for Thursday through Saturday. && .KEY MESSAGES... 1) Remaining very warm and humid today. A Heat Advisory has been issued for portions of Northeast NC along the Albemarle Sound. 2) Most locations remain dry today, but some afternoon/evening storms will be possible, mainly along the coast and well inland over the VA Piedmont. 3) After a brief lull in rain chances through midweek, showers and storms return to the forecast Thursday afternoon into the upcoming weekend. && .DISCUSSION... As of 305 AM EDT Tuesday... KEY MESSAGE 1...Remaining very warm and humid today. A Heat Advisory has been issued for portions of Northeast NC along the Albemarle Sound. A diffuse frontal boundary/surface trough is draped across the Eastern Shore to the Chesapeake Bay and NE NC early this morning. The boundary slides offshore this afternoon with light NNW winds by afternoon. Not quite as hot today, but with drier air not likely to arrive until later tonight and tomorrow, expect another very warm and quite humid day. Forecast highs are in the upper 80s to low 90s, with dewpoints in the low to mid 70s. This will yield maximum heat indices in the mid 90s to around 100F across much of the area. For communities just inland and along the Albemarle Sound, light winds and a stagnant air mass will yield heat indices in the 105-109F range. A Heat Advisory has therefore been issued for Bertie, Chowan, and Hertford Counties. KEY MESSAGE 2...Most locations remain dry today, but some afternoon/evening storms will be possible, mainly along the coast and well inland over the VA Piedmont. No apparent convective trigger today, and therefore expect storm coverage will be lower relative to the past couple of days. Nonetheless, limited coverage of showers and storms remains possible along the coast with the afternoon sea breeze, and as the frontal boundary edges south late today. A few additional showers will be possible well inland late in the day along the weak Piedmont trough. Kept PoPs capped at 20-30%. KEY MESSAGE 3...After a brief lull in rain chances through midweek, showers and storms return to the forecast Thursday afternoon into the upcoming weekend. Temperatures and PoPs return toward climatological norms for mid to late August tomorrow. Modest dewpoint relief for areas along and west of the I-95 corridor as the front settles farther south into the Carolinas. Looking ahead, an increasingly active pattern takes hold again for late week into the weekend. Broad upper level troughing builds over the Eastern Seaboard, driving another series of shortwaves from the Ohio Valley into the mid-Atlantic Thu-Sat. An associated, seasonally strong cold front approaches for late week and will likely stall over the local area. This slowing boundary will once again focus multiple rounds of showers and storms across the area Thursday through Saturday. PWs jump back AOA 2-2.25" and with them, the potential for more strong convection and locally heavy rainfall returns, likely coincident with the position of the stalled boundary. For now, WPC has included the entire local area in Marginal Risk ERO for Days 3-5 (Thu- Sat), and expect this will be refined in time as we get closer. Model ensembles still generally agree that the main trough axis eventually shifts east late Sunday into early next week, driving the front through and briefly introducing a cooler, drier airmass across the mid- Atlantic before temperatures moderate again by the middle of next week. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... As of 200 AM EDT Tuesday... VFR conditions prevail to begin the 06Z TAF period. Some low stratus in the vicinity of the PHF/SBY terminals, and have allowed for some IFR/LIFR conditions early this morning. Thereafter, VFR conditions return and should persist through the end of the period. Only exception is with some scattered convection on the afternoon seabreeze is possible at ORF that could lead to short-lived VSBY restrictions. Some late night stratus/fog will once again be possible along the coast early Wednesday morning. Outlook: Mainly dry/VFR conditions continue into midweek as weak high pressure returns. Potentially turning unsettled Thursday into the weekend ahead of a slow-moving frontal boundary that could bring additional rounds of showers and storms and brief sub-VFR conditions. && .MARINE... As of 305 AM EDT Tuesday... Key Messages: - Generally benign marine conditions expected through the end of the week, outside of afternoon/evening thunderstorms. A weak frontal boundary is crossing the local waters early this morning, shifting the winds from the SW to the N-NW. Wind speeds are aob 10 kt with gusts to 15 kt behind the direction change this morning. The boundary will fully cross the waters by this afternoon with wind speeds remaining around 10 kt. Winds will veer back to the S/SE Wed night/Thur, but will generally remain aob 10 kt. Seas will remain ~2 ft with 1-2 ft waves. Benign, sub-SCA marine conditions will continue through the rest of the week. Isolated to scattered aftn/evening storms are possible again today, which could pose a threat to boaters. The chance of storms decreases Wed, with a potentially greater coverage of storms on Thur/Fri. SMWs are possible with the stronger storms, though widespread severe wx is not expected. There remains a low risk of rip currents at all beaches over the next few days. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...Heat Advisory from 11 AM this morning to 8 PM EDT this evening for NCZ030>032. VA...None. MARINE...None. && $$ DISCUSSION...MAM/SW AVIATION...MAM MARINE...ERI/KMC ####018003116#### FXUS63 KAPX 180714 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 314 AM EDT Tue Aug 18 2026 .KEY MESSAGES... - Showers likely and chance of thunderstorms this afternoon/evening. A few strong storms possible. - Quiet Wednesday-Thursday - Unsettled again Thu night into this weekend && .DISCUSSION... Issued at 314 AM EDT Tue Aug 18 2026 An upper low is gradually transiting Hudson Bay and northern Quebec this work week. This will tend to keep our heights somewhat suppressed, and temps will follow suit. A cold front passage tonight will contribute to our initial chances for rain. After a break, unsettled wx returns for the very end of the week. Outside of more marine locales, surface dew points are in the 50s early this morning. Though these will rebound somewhat today, to near 60s/lower 60s, this will still tend to limit available instability before cold fropa. MlCape values rise to up to 750j/kg by late afternoon in the south half of the forecast area. Turning this into actual convection is not entirely certain; we will mix up into west 1km winds pre-fropa, and convergence along the front will be unimpressive. Current shower activity in the western UP will expand eastward, and some showers could reach western Chip/Mack Cos before 12z. Chancy pops will continue to expand south/east thru very early afternoon. Pops will increase further moving thru the afternoon/evening as instability peaks. Activity rapidly weakens/exits eastward toward/after midnight. 0-6km bulk shear values are 30-40kt, so we perhaps have enough instability and shear for a strong storm or two, but severe storms are not likely. SPC has tucked a marginal day 1 severe risk into the MBL/CAD/Gladwin area (not a huge fan). Much drier air invades behind this front, with dew points lowering into the 40s in some areas Wed night-Thu night. Dry wx expected Wed- Thu, with near seasonable highs but lows below normal. More unsettled wx Thu night into Saturday. Expect energy to dig and eventually close off in the central/eastern lakes region this weekend. Initial chancy pops in the west and north Thu night, become likely across most of northern MI by Fri afternoon/evening. May have to watch out for stronger storms then as well. Likely turning cooler with and behind this system for Sunday-Monday. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 1119 PM EDT Mon Aug 17 2026 VFR condtions will prevail with perhaps patchy BR/FG developing across some terminals later tonight into Tuesday morning. Scattered shower and thunderstorm chances increase through the day Tuesday, but thinking this will be very spotty and pop-up in nature like we had the other day. BR/ FG development looks more widespread late Tuesday into Wednesday morning as more moisture works into the region. && .APX WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...JZ AVIATION...NSC