Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
421 FXUS62 KKEY 190807 AFDKEY Area Forecast Discussion National Weather Service Key West FL 407 AM EDT Sun May 19 2024 ...New DISCUSSION, MARINE, AVIATION... .DISCUSSION... Issued at 407 AM EDT Sun May 19 2024 Despite being a relatively quiet night across the Florida Keys, KBYX is detecting some of the first showers we have seen within our forecast area in the past few days. All of these showers have remained offshore in the SE Gulf, so there has been no measurable rainfall along the island chain. GOES Nighttime Microphysics is detecting mostly clear to partly cloudy skies across the forecast area, with a combination of both low level cumulus and upper level cirrus. Temperatures remain in the lower to mid 80s early this morning and dew points are in the upper 70s to near 80, leading to heat indices between 95-100 degrees. With winds trending downward over the past hour or so, the oppressive humidity is becoming even more apparent, if that is even possible... Another day of above normal heat is on tap for the Florida Keys. While MOS guidance is suggesting dew points a degree or two lower than what we have been experiencing the past few days, have decided to issue another heat advisory for today. The synoptic feature that has been responsible for this oppressive mid-May heat is an expansive mean layer ridge that has been parked over us. This high will finally get shoved eastward starting today as a longwave trough traverses across the Southeast. The front associated with this trough will slide down the Florida Peninsula over the next few 122days. As this front travels down the state, model guidance depicts moisture pooling across the Keys and South Florida. While the best upper-level support is forecast to remain to our north, rain and thunder chances are forecast to increase tonight. There is still a large amount of discrepancy between models in terms of PoPs, with the ECMWF coming in much wetter than the GFS. As a result, there is an unusually large amount of uncertainty in the near-term forecast. Have decided to split the difference and kept mid-chance PoPs for tonight through Tuesday. Thereafter, rain and thunder chances will return closer to normal (~20%) as mid-level dry air invades. Low-level moisture will remain in place during this time, allowing for mesoscale processes to dominate within the light wind regime forecast for the next week. In terms of temperatures and dew points through the extended forecast, winds will shift to the northwest to north ahead of the aforementioned front this evening. This will bring in lower dew points and help drop temperatures a degree or two beginning tonight. Temperatures through the work week will generally be hovering around the climatological norm, with dew points forecast to be in the lower to mid 70s. This will put us out of Heat Advisory criteria and bring us back to our regularly scheduled May. && .MARINE... Issued at 407 AM EDT Sun May 19 2024 There are no watches, warnings, or advisories in effect for the Florida Keys coastal waters. From synopsis, the western extent of a low-level ridge axis that extends west-northwest has begun to lose its grip across the Florida Keys, and breezes have shifted to the southeast to south. Breezes will quickly veer to the north and decrease today as a frontal boundary slides down the Florida peninsula. There may be a break in the rain-free conditions tonight through Tuesday, followed by variable breezes turning to the east Wednesday through Thursday. && .AVIATION... (06Z TAFS) Issued at 407 AM EDT Sun May 19 2024 VFR conditions will prevail at both EYW and MTH today and early tonight. While there is a slight chance of showers today, they will be isolated at best with low confidence in exact location so VCSH is left out of either TAF for now. Tonight, scattered showers and isolated thunderstorms are expected to develop along the island chain and persist into tomorrow morning. As the timing isn`t set in stone yet and is just on the far edge of the TAF period, no mention is expressed in this morning`s TAFs. Near surface winds will start out of the southeast to south at near 10 knots this morning, becoming west to northwest later this afternoon. && .CLIMATE... Yesterday, May 18th, the low temperature at both Key West and Marathon was 84F. This broke daily record warm low temperatures at both sites. At Marathon, this low temperature tied the highest warm low ever recorded in May in Marathon (current record that was tied: 84F, 2017), and broke the highest warm low ever recorded in May in Key West (previous record: 83F, 2024, 2020, 2017). Temperature records date back to 1872 in Key West and 1950 in Marathon. && .PRELIMINARY POINT TEMPS/POPS... Key West 91 80 88 79 / 10 40 30 40 Marathon 91 80 88 79 / 10 40 30 40 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...Heat Advisory from 10 AM this morning to 6 PM EDT this evening for FLZ076>078. GM...None. && $$ Public/Marine/Fire...NB Aviation/Nowcasts....JAM Data Acquisition.....JAM Visit us on the web at weather.gov/key Follow us on Facebook and Twitter at: www.facebook.com/nwskeywest www.twitter.com/nwskeywest