####018007526#### FXUS66 KMTR 031827 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1127 AM PDT Fri May 3 2024 ...New AVIATION... .SYNOPSIS... Issued at 1243 AM PDT Fri May 3 2024 A cold front will bring rain, gusty winds, and colder temperatures on Saturday. Dry weather returns Sunday as a gradual warming trend kicks off. && .SHORT TERM... (Today and tonight) Issued at 108 AM PDT Fri May 3 2024 A shallow marine layer will bring low stratus to coastal areas and adjacent valleys Friday morning. High temperatures will depend on whether a location is in or out of the marine layer. For example, Pt. Reyes is only expected to reach 56 degrees today, while Santa Rosa will flirt with 80, and enjoy ample sunshine. By the afternoon, an approaching cold front will cause the winds to increase, with rain reaching the North Bay early Saturday morning. && .LONG TERM... (Saturday through Thursday) Issued at 108 AM PDT Fri May 3 2024 A gale force, 997 mb, vertically stacked low pressure system is currently near the Gulf of Alaska. This system will be driven southeast by a 150 kt jet stream through Saturday. This strong jet max will also create divergence aloft, allowing the surface pressure to remain steady or even decrease slightly as the system loses latitude. The low center is expected to come ashore near Northern California or Southern Oregon early Saturday morning. An associated cold front will cross the Bay Area through the day Saturday. This frontal passage will bring periods of rain and gusty winds as it ushers in a new, colder air mass. Precipitable water values are expected to be above 1" on Saturday, with some guidance as high as 1.25". As the cold, dense air lifts this moisture, rain clouds will develop. The total QPF is holding pretty steady with most places expected to receive around 0.5" on Saturday. While not a total wash-out, this is a significant amount for May, which has monthly normal rainfall pretty close to the expected amount from this one system. During the afternoon OAK balloon launch Thursday, the 1000-700 mb thickness was measured at 2967 m. This new air mass will drop the that to around 2815 m, according to the NAM point sounding. By Sunday morning, NAM has the 700 mb temperature down to -12.7C, which is well below the 10th percentile (-5.2 C) and even the daily minimum (-9.9 C) from May 5, 1988. Note the 1000-500 mb thickness drop isn't as impressive due to more flat mid-level lapse rates. This suggests that any convection that takes advantage of the cold air aloft will be low-topped, even by Bay Area standards. Additionally, the coldest mid-level air arrives overnight Saturday/early Sunday during the diurnal minimum. These two factors should limit the potential for thunderstorms, although a slight chance remains. Finally, this system will bring a noticeable drop in temperature, especially for inland areas. Friday will feature inland temps in the mid to upper 70s. 24 hours later, these same places will be stuck in the upper 50s or low 60s. Beyond Saturday, the forecast is more straight forward. Ridging from subtropical high pressure builds in Sunday which will gradually transition to the standard coastal trough set-up by mid next week. This pattern will bring the return of dry weather, lots of sunshine, and a gradual warming trend. Coastal areas may reach the low 70s and some inland areas will be in the 80s by late week. && .AVIATION... (18Z TAFS) Issued at 1126 AM PDT Fri May 3 2024 VFR prevails through the daytime today, though stratus makes a return in the early to mid evening for most terminals, bringing largely IFR/LIFR conditions as ridging continues to squash cloud decks. Winds generally W/NW and strong today, with gusts around 20- 25 knots, higher at SFO. As stratus approaches in the evening, winds ease, but remain close to 10 knots through much of the night, and slowly turn to become more S/SW ahead of the approaching low pressure system. By the mid morning hours of Saturday, most terminals will see winds increase once more to become breezy and gusty out of the SW, and rain begins, lowering visibilities at terminals. Cloud decks are expected to improve to become MVFR around the same time to slightly after when rain approaches as greater lifting from associated low pressure is enabled. Rain continues through the end of the TAF period for most terminals, with winds turning to become N/NW and breezy. Vicinity of SFO...VFR conditions last through the afternoon today, with strong and gusty onshore winds. Max gusts up to 35 knots are expected. Stratus makes an early return in the evening, bringing IFR conditions. Models suggest a reduction to LIFR conditions in the overnight hours, but at this time, confidence in that development is low. Have kept CIGS IFR and then improving to MVFR in the later morning for now. Rain and gusty SW winds begin just prior to sunrise Saturday for KSFO. Winds turn to become W/NW in the later morning, but rain lasts through the afternoon. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Conditions improve to VFR in the early afternoon today, though only for a few hours before stratus and IFR/LIFR CIGs make a quick push inland in the early evening. Winds NW and breezy this afternoon, but easing into the evening to below 10 knots. IFR/LIFR CIGs last through the majority of the overnight hours. Towards the late morning of Saturday, rain begins and CIGs lift to become IFR. Some model solutions hint at CIGs lifting enough to become MVFR by the end of the TAF period. However, confidence in this outcome is low at this time. For now, have left CIGs as lifting, but remaining in IFR through the end of the TAF period. && .MARINE... (Today through Wednesday) Issued at 457 AM PDT Fri May 3 2024 Strong and gusty northwesterly winds will persist for yet another day as the region remains in between high pressure over the Eastern Pacific Ocean and low pressure over the Southwest. Gale force gusts will be possible, especially over the coastal waters and southernmost zones. Tonight, a cold front will drop down from the Pacific Northwest bringing rain and moderate to fresh breezes across the waters. As the low pressure system exits to the east and the pressure gradient is allowed to relax, winds will diminish going into next week. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory until 9 PM PDT this evening for Mry Bay- Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm. Gale Warning until 3 AM PDT Saturday for Pt Pinos to Pt Piedras Blancas 0-10 nm. Small Craft Advisory until 3 PM PDT this afternoon for Pt Arena to Pt Reyes 10-60 NM. Small Craft Advisory from 3 AM to 9 AM PDT Saturday for Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...Flynn LONG TERM....Flynn AVIATION...AC MARINE...AC Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea ####018003560#### FXUS62 KKEY 031827 AFDKEY Area Forecast Discussion National Weather Service Key West FL 227 PM EDT Fri May 3 2024 ...New DISCUSSION, MARINE, AVIATION... .DISCUSSION... Issued at 1107 PM EDT Fri May 3 2024 A mix of sun and clouds continue as we head into the evening hours with radar showing only a few showers around the forecast area. While a cloud line has set up across the Middle and Lower Keys, there has been no indication that any rainfall is occurring and dry conditions should continue overall. A seasonably quiet weather pattern is on tap for the Florida Keys through the extended forecast. While deep tropical moisture is located nearby across the Central and Western Caribbean, this moisture will generally remain parked there, leaving the Keys in a drier airmass. Rain chances are not expected to eclipse 20% as this drier airmass and a generally stable environment nix most shower development before it can lead to measurable rainfall across the island chain. The best chance for rainfall will be Sunday night through Monday night when some of the aforementioned moisture to our south creeps into the Straits. This, combined with possible speed convergence from oscillating wind speeds, will lead to a better environment for shower development. Have retained the previously advertised 20% for these forecast periods. As mentioned, easterly winds will peak and lull through the extended forecast, with higher winds expected overnight, decreasing by the morning. These easterly winds will continue to pump in near to above normal temperatures, with highs in the mid to upper 80s forecast during the day, and lows only dropping into the mid to upper 70s. Dew point temperatures will also slowly inch upwards through next week, with lower to even possibly mid 70 dew points possible by late next week. Summer coming up on us very quickly, with the possibility of another front and some relief becoming more and more unlikely each day. && .MARINE... Issued at 1107 PM EDT Fri May 3 2024 High pressure over the western North Atlantic will encourage moderate to fresh easterly breezes for the next several days. Small craft should exercise caution tonight due to increasing winds across portions of the coastal seas. Breezes will tend to peak overnight, followed by lulls in the afternoon. && .AVIATION... (18Z TAFS) Issued at 1107 PM EDT Fri May 3 2024 Dry, VFR conditions will prevail at EYW and MTH through the TAF period. Near-surface winds will be slightly elevated near EYW while a weak afternoon cloud line remains north of the terminal. Stronger near-surface winds may allow an occasional gust up to 20 knots, but the lack of predictabiltiy or persistence kept them out of the TAFs. CIGs will remain above VFR criteria with FEW to SCT layers below 3 kft. && .CLIMATE... On this date in Keys Weather History, the daily record high temperature of 91F was recorded in 1873. Temperature records in May for Key West date back to 1873. && .PRELIMINARY POINT TEMPS/POPS... Key West 76 85 77 85 / 10 10 20 10 Marathon 76 85 77 85 / 10 10 20 10 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...NB/DP Aviation/Nowcasts....AJP Data Visit us on the web at weather.gov/key Follow us on Facebook and Twitter at: www.facebook.com/nwskeywest www.twitter.com/nwskeywest