Area Forecast Discussion
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FXUS62 KKEY 230834

Area Forecast Discussion
National Weather Service Key West FL
434 AM EDT Thu Mar 23 2017

Skies are mostly clear across the Florida Keys and adjoining
waters early this morning, with rain-free conditions, and very
seasonable air temperatures in the upper 60s in most Keys island

The large-scale pattern features split upper-level westerlies over
the continental United States, and a sharp ridge extending from
Mexico to Canada. This ridge supports a robust surface anticyclone
currently centered over Pennsylvania and extending south to
central Florida. The southern flank of this system is associated
with a sharp MSL pressure gradient and a remnant, weak convergence
zone once associated with a midlatitude trough/front (but no
longer). In addition, a residual plume of fairly steep 850-500mb
lapse rates (also remnant from a midlatitude short-wave trough)
currently is advecting southward over the Florida Peninsula. A few
thunderstorms are evident in radar/satellite imagery over the
Atlantic east of the Florida Peninsula at this hour.

Forecast reasoning has not changed much during the last 24 hours.
We still expect higher rain chances in the upper Keys late this
afternoon, and to a lesser extent, the middle Keys. The lower
Florida Keys should remain mostly sunny and rain free today.

Tonight will be breezy, with variable cloudiness, scattered
showers and perhaps an isolated thunderstorm or two.

Strong east breezes will persist Friday and Friday night, with
decreasing shower coverage.

Breezes will diminish further Saturday through Sunday, and Small
Craft Advisories may be able to be dropped for some zones
Saturday afternoon, and most zones by Sunday afternoon.

Monday through Wednesday look very seasonable, with mostly clear,
rain-free conditions, moderate breezes, highs near 80F, and lows
near 70F in most Keys island communities.

Small Craft Advisory conditions are expected to develop across all
Florida Keys coastal waters this evening. A sprawling high
pressure system will build from eastern Canada to Cuba today and
tonight. As a consequence, strong northeast to east breezes will
develop across Keys coastal waters this evening, and persist
through early Saturday. The large and strong high pressure system
will weaken slowly, as it migrates over the western North Atlantic
Saturday night through Monday.

VFR conditions will prevail this morning and afternoon for EYW and
MTH. Some showers might affect MTH first after 6 pm, followed by the
slight possibility of a thunderstorm, which were kept out of the
TAFs due to its uncertainty at this time. Northerly winds of 5 to 10
knots this morning, will turn from the east by mid-afternoon and
increase after 24/00z from the east northeast to 15 knots and gusts
to around 20 knots.

The high temperature yesterday, March 22, was 80F at Key West
International Airport, 78F at the National Weather Service in Key
West, and 80F at Florida Keys Marathon International Airport. The
average high temperature for today, March 23, is 79F, and the
average low temperature is 69F.

Key West  79  69  79  70 / -  40 30 10
Marathon  80  71  79  72 / 20 40 30 10




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