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Area Forecast Discussion (AFD)

Issued by Key West, FL (KEY)

FXUS62 KKEY 141004

Area Forecast Discussion
National Weather Service Key West FL
504 AM EST Wed Nov 14 2018

Water vapor imagery highlights an extensive moisture plume racing
northeast from the eastern Pacific to the Canadian Maritimes.
CIMMS mean layer analyses indicate deep ridging persists over the
extreme western North Atlantic. Surface observations place a
stalled cold front over the Gulf of Mexico. And yet, water vapor 
imagery highlights several synoptic players over the next 24 
hours which will drive the stalled front towards the southeast. 
First, a westward moving trough complex near Hispaniola will erode
the subtropical ridging. Second, the base of the long wave trough
south of the Baja Peninsula continues to press equatorward. 
Finally, a short wave trough moving towards California has 
effectively eroded the ridging over the southwestern United States
(see 00Z regional RAOBs). The erosion of the western Atlantic 
ridge will give the long wave trough room to finally press east. 
Phasing of the long wave axis with the California short wave will 
kick the whole shebang eastward. 

The cold front across the Gulf will approach the Florida Keys
tonight. The statistical MOS consensus for tonight continues to
indicate extremely high rain chances for the island chain, with a
lack of corroboration from the plan view pattern. The approach of
the synoptic moisture plume may be contaminating MOS estimates. 
Nevertheless, we have retained the 50% rain chances for the 
overnight period, which is below the consensus. Freshening 
northerly breezes will reach the Dry Tortugas just after sunrise 
Thursday morning. There are still some timing issues, and the GFS
remains an early outlier. The brisk northerlies will spread east 
across the island chain Thursday, reaching the Lower Keys after 
noon, and the Upper Keys shortly after sunset. The warm Gulf and 
Bayside coastal waters will temper the low temperatures Thursday 
night, although howling northerlies will be hard to ignore. 
Temperatures will only reach the mid 70s Friday, the first time 
Key West's high temperature has not reached 80 since May 25th. 
Breezes will subside significantly Friday afternoon in the lee of 
the peninsula. Fresh to moderate, northeast to east breezes will 
persist Saturday through Monday as the front tries to return to 
the north. Expect increased cloud cover and the return of rain 
chances as the warm front morphs over the Keys. A second 
continental airmass surge likely will kill off the frontal 
boundary Monday night or Tuesday. 


A cold front stalled over the Gulf of Mexico will surge towards 
the Florida Keys tonight, then blast southeast through the island 
chain Thursday. Strong northerly breezes and building seas are 
expected behind the front, and Small Craft Advisory conditions are
expected Thursday and Thursday night. Breezes will diminish on 
Friday, followed by several days of moderate northeast to east 


VFR conditions are expected to prevail at both KEYW and KMTH through 
the forecast period. Showers will be in the vicinity of the Key West 
terminal through the morning hours. Winds generally from the east-
southeast and below 10 knots. 


November 14th, on this date in 1949, the daily record high 
temperature of 86F was last recorded. Temperature records in Key
West date back to 1872. 


Key West  87  78  81  70 / 30 50 40 20 
Marathon  88  77  82  68 / 30 50 40 20 




Data Collection......BT

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