Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
288 FXUS62 KKEY 220837 AFDKEY Area Forecast Discussion National Weather Service Key West FL 437 AM EDT Sun Sep 22 2024 ...New DISCUSSION, MARINE, AVIATION... .DISCUSSION... Issued at 437 AM EDT Sun Sep 22 2024 Convection has been a bit more active during the late night period than would have been expected given the fairly dry airmass sampled by the 00Z Key West sounding (PW of 1.69 inches), and very weak flow present throughout the lower and mid levels. Currently, radars show widely scattered showers over the Gulf waters north of the Lower Keys and the Straits of Florida. Temperatures along the island chain are mostly in the lower 80s, with dewpoints in the mid 70s, and winds on land mostly from the NE to E at 5 mph or less. Surface analysis depicts a nearly flat pressure gradient still present across our region, with weak high pressure over the Southeastern states, a trough draped across the Bahamas, and broad low pressure over the SW Caribbean Sea. Aloft, a trough is moving slowly eastward over the western Atlantic and the Bahamas, with a ridge building over the Texas coast and the western Gulf of Mexico. Generally quiet weather with below normal rain chances will prevail across the Keys today through Monday, with extensive dry air in the mid to upper levels likely to suppress convection. Light flow in the lower to mid levels may allow for some minor island cloud line development again today, but this will be vertically challenged by the dry air aloft. The best rain chances during this period will probably occur this evening, when a brief window of NE steering flow may transport some convection and/or associated outflows from the southern mainland down into our area. Otherwise, expect light mainly easterly breezes today to increase a bit on Monday, with highs around 90 and lows mostly in the lower 80s. Forecast uncertainty increases greatly thereafter, as eyes turn to our southwest, where a developing Central American Gyre (CAG) will likely aid eventual development of a tropical surface low somewhere over the western Caribbean Sea, although timing and subsequent movement of any such low remain quite uncertain at this time. We do note somewhat better agreement among the 00Z GFS/ECMWF and 00Z GEFS runs, showing a northward track near the Yucatan Channel and then up through the central or eastern Gulf, although timing differences remain. For now, we continue to forecast an extended period of breezy/windy and wet weather beginning late Tuesday and continuing through the rest of the work week. We continue to emphasize that the extended forecast will likely change during the next several days as the eventual evolution of any tropical low resulting from the CAG becomes more clear. Residents and visitors in the Keys are encouraged to check back for the latest forecast updates through the upcoming week. && .MARINE... Issued at 437 AM EDT Sun Sep 22 2024 A Coastal Flood Advisory remains in effect for the Upper Keys, and a Coastal Flood Statement remains in effect for the Middle and Lower Keys, as above normal tides continue. Boaters can expect less clearance under fixed bridges, especially during the hours around high tide. Late night observations show mostly NE to E breezes of 5 to 7 knots along the reef and at Long Key C-MAN, with seas at Satan Shoal running a bit below one foot. From the synopsis, light easterly flow across the Keys coastal waters today and tonight will gradually increase Monday through Tuesday, as high pressure builds along the Eastern Seaboard, and a tropical low slowly develops in the northwestern Caribbean Sea. Heading through the middle and later part of the week, the forecast will depend on the potential development and movement of this low. At this time, we expect fresh to strong east to southeast breezes to develop late Tuesday, becoming southerly late in the week, with the strongest winds over western sections of the Keys waters. Mariners should continue to closely monitor the latest forecast updates during the next several days. && .AVIATION... (06Z TAFS) Issued at 437 AM EDT Sun Sep 22 2024 VFR conditions will prevail at EYW and MTH for the 06Z 22 Sep TAF period. Broad near-surface wind convergence will support development of widely scattered showers and isolated thunderstorms in the early morning south of the island terminals. TEMPOs may be required for VCTS or TSRA conditions. Near surface winds are forecast to shift after sunrise, and VCSH was removed from the TAFs in response to the change in direction. && .CLIMATE... On this day in Keys weather history in 1959, the daily record low temperature of 66F was recorded in Marathon. This temperature reading tied for the coldest temperature recorded during the month of September. Temperature records for Marathon date back to 1950. && .KEY WATCHES/WARNINGS/ADVISORIES... FL...Coastal Flood Advisory until 5 PM EDT Monday for FLZ076. GM...None. && $$ Public/Marine/Fire...Jacobson Aviation/Nowcasts....AJP Visit us on the web at weather.gov/key Follow us on Facebook and Twitter at: www.facebook.com/nwskeywest www.twitter.com/nwskeywest