Area Forecast Discussion

FXUS62 KKEY 161900
Area Forecast Discussion
National Weather Service Key West FL
200 PM EST Sat Dec 16 2017
.DISCUSSION...In the middle and upper levels(700-200 mb), latest
satellite imagery overlaid with model streamline analysis as of
200 pm depict a deepening middle and upper longwave trough now 
over the Western CONUS with an embedded sharpening positively 
tilted trough axis oriented from Saskatchewan to just offshore of 
Southern California and a developing upper cyclone over SW New 
Mexico. Downstream of that, middle and upper height rises are 
evident over the SE United States as a deep and warm anticyclone 
centered just over Jamaica builds northwards.
At the surface and in the lower to middle levels,(Surface-700 mb),
latest satellite imagery overlaid with surface land and marine
observations and analysis as of 200 pm detail a 993 mb surface 
low southeast of Newfoundland trailing a cold front southwest to 
across Central Florida. Back behind that feature, the near 1030 
mb center of an east to west oriented ridge is located near
Atlanta, with the ridge intensifying a bit more and earlier than
anticipated by the models. 
.CURRENTLY...As of 200 pm, satellite imagery detects wisps of 
cirrus scattered overhead with no other clouds below that. Despite
near breezy to breezy conditions, temperatures have struggled to 
reach the middle 70s, with dewpoints in the lower 60s, at this 
hour along the island chain. C-man stations are recording 
sustained northeast winds near 15 knots along the Florida Reef, 
with island sensors near 15 mph over land.
.SHORT TERM...Tonight thru Wednesday , middle and upper height 
rises are indicated as large middle and upper ridge builds 
northward across the SE United States out of the Caribbean. The 
surface ridge across Central MS/AL/GA will build eastwards and 
continue to intensify overnight. As such near breezy/breezy 
conditions this afternoon across the islands and surrounding 
waters will become breezy/windy conditions this evening. The high 
will remain in place during Sunday and Sunday night, then slide 
southwards to North Florida Monday and Monday Night, then down to 
Central Florida by Tuesday and Tuesday Night, then just north of 
the Florida Keys on Wednesday. 
Latest available model forecast soundings illustrate a slight 
uptick in boundary layer moisture and given increased near surface
convergence, reinserted a dime pop in the grids beginning 
tomorrow, for typical late night early morning brief showers. High
temperatures will reach around 80 tomorrow and Monday, and into 
the lower 80s by Tuesday and Wednesday, with lows near 70 tonight 
and tomorrow night, and only into the lower 70s Monday and Tuesday
night, with the ol dewpoint rising back to near 70. Return to 
tropical feel in as we approach the apex of the Holiday period
.LONG TERM...Wednesday night through Saturday, heights are still
indicated to remain above normal over Florida with no surface
frontal progged to get down into the Keys. Elevated temperatures
will be several degrees above normal for hi and lo temperatures.
Given slightly more low level moisture, will maintain the dime pop
already in the grids, but a shower, if any will be very brief and
.MARINE...Small craft advisory conditions expected across all
waters tonight except GMZ031-032-035, with SCEC expected except
across Florida Bay. SCA appear likely again across all of the
Florida Straits for Sunday and Sunday Night, with SCEC likely and
SCA still very possible across the rest of the waters again, 
except the shallower GMZ031-032-035 waters. SCEC conditions seem
likely across the Straits again Monday and Monday Night, though
winds and seas begin to come down, and all headlines and
advisories not anticipated Tuesday onward.
.AVIATION...VFR conditions expected overnight at both the KEYW and
KMTH island terminals, with NE-E winds averaging between 12 and 
15 knots with gusts near 20 at the surface, becoming E during the 
evening. Winds will average above 20 knots right off the surface.
Key West 71 82 74 82 / - 10 10 10 
Marathon 72 81 74 81 / - 10 10 10 
GM...Small Craft Advisory from 5 PM this afternoon to 5 AM EST Sunday 
     for GMZ033-034-042>044-052>055-072>075.
Upper Air/Data Collection......Rizzo/KN
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