Area Forecast Discussion
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FXUS62 KKEY 230202

Area Forecast Discussion
National Weather Service Key West FL
1002 PM EDT Sat Apr 22 2017

A large area of rain and showers continues to lift northward,
remaining over the bulk of the Keys service area late this
evening. There have been a few steady pockets of heavier showers
and thunderstorms, but these have favored the Atlantic waters
south of the Lower and Middle Keys thus far. Winds have remained
from the east/southeast, and have fluctuated slightly in speed
through the course of the evening. Most recently, they are on the
upswing, remaining fresh.

The late evening local sounding shows the veered profile remains
in tact, but the depth of the fresher winds has decreased to the
lowest layers. The local airmass is moist, with the precipitable
water tally setting another daily record...2.10 inches. Quite
moist for April. There is enough instability to sustain at least a
few thunderstorms overnight. A mid level trough will steadily work
eastward across the local area overnight. Beneath that, a
relatively deep area of low pressure will lift northeastward
across the local area. Based on the radar loop over the past
several hours, in conjunction with the pattern in place, will hold
on to the categorical probability of measurable precipitation
overnight. The only reason for a late evening zone change would
be to adjust the advertised winds upward through the overnight
period. See reasoning in the marine section below.


The upcoming late evening coastal waters forecast will keep the
small craft advisory for the offshore Gulf waters and all near and
offshore Atlantic waters through the remainder of the first
period. Although winds have fluctuated slightly over the past
several hours, the most recent upward trend, along with the latest
HRRR local solution point toward higher winds as the lower level
cyclonic circulation approaches through the overnight period.
However, directional shifting more toward the south should hold
off closer to the daytime hours of Sunday. Admittedly, wind speeds
may actually be borderline for several hours as far as the
advisory is concerned, but with this unusual pattern, would prefer
to error on the high side. Expect widespread rain showers with a
few thunderstorms over the bulk of our marine service area


Periods of MVFR CIGS/VIS, along with widespread showers will
continue overnight with shower coverage gradually diminishing from
west to east early Sunday morning. Easterly winds will gust to near
20 knots before decreasing to near 10 knots after 23/09z, while
gradually veering and becoming southerly by daylight. Prevailing VFR
will likely return after 23/15z. The thunderstorm risk seems minimal
overnight, but certainly not out of the realm of possibility, and
amendments to the terminal forecast will be issued if necessary.


.CLIMATE... On this date in Florida Keys History, in 1937, a high
temperature of 88 degrees was recorded in Key West. This set the
record for highest temperature measured for April 23rd for the city,
a record which still stands 80 years later. Temperature records in
Key West date back to 1872.


GM...Small Craft Advisory GMZ033-034-042>044-052>055-072>075.



Data Collection......Fling

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