Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 240128
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
928 PM EDT Mon Oct 23 2017

.DISCUSSION...

Evening Update...A broken line of showers and storms has moved
across the nrn forecast area this evening with over an inch of rain
at Daytona Beach and .79 inches at Leesburg. Deep upper level trough
from the upper MS Valley into the southeast states wil continue
favorable upper level divergence that will gradually shift south
through the night. Forecast models indicate mid levels drying out
across nrn sections above 700 mbs after midnight which should tend
to limit additional vigorous convection across NW areas. Will
continue POPs near 50 percent much of the srn CWA and increase POPs
slightly near ongoing convection from Osceola to Volusia counties.
Some locally heavy rainfall amounts up to 1-2 inches possible with
showers/storms that redevelop in the moist low level SW flow through
the night mainly SE of a Clermont to Daytona Beach line.

Tonight (previous)...There will be an increase in coverage of
showers/storms into this evening as increasingly moist south
southwest flow combines with upper divergence ahead of an upper
level trough. The assocd cold front is currently located from
central GA southward across TLH and into the Gulf. Considerable
cirrostratus continues to overspread northern sections which has
limited heating today but developing convection on the FL west coast
will push east and interact with the east coast sea breeze over
interior sections toward evening. Additional storms should develop
over southern sections where more heating has taken place. So have
drawn 50 PoPs all areas. Convection will likely persist well into
the night supported by forcing aloft. The cold front is forecast to
reach Lake/Volusia counties by sunrise then push more slowly across
EC FL during Tue.

Tuesday-Wednesday (previous)...Strong upper low pressure with
associated deep troughing over the central CONUS will move slowly
east and weaken gradually with a mid-level trough axis finally
sliding across the central FL peninsula Wed overnight. This upper
system will help drive a significant cold front into north-central
FL by sunrise Tue morning, then across ECFL during the day on Tue
and Tue night. A tight pressure gradient will remain as weak high
pressure builds into the area behind the front late Tue overnight
into Wed. An above normal chance of showers and thunderstorms
will precede the boundary on Tue with much drier air filtering
into the area from the north on Wed. The showers and storms will
feed off of PWATs between 1.70-1.90 inches and some modest surface
heating. The best dynamics, however, will remain north of the
area. A few strong storms may be possible but currently are not
anticipating any severe weather.

Rain chances will range from 30 to 40 percent north of I-4 to 60
percent south of Orlando Tue. Rain chances will diminish from north
to south over the area Tue night. Have precip slowly ending on Wed
over the Treasure Coast/Okeechobee County as the ECMWF is a bit
slower to scour out moisture.

Max temps in the L80s Tue, perhaps M80s should enough surface
heating occur, and L-M70s on Wed. Mins falling back into M-U50s
north/L-M60s south behind the front Tue overnight, with L50s for
most of the area Wed night, even some U40s north of I-4 or normally
cooler areas of ECFL.

Thursday-Sunday (previous)...Aloft upper troughing continues to
push eastward away from the peninsula as brief shortwave ridging
moves across the state and northerly winds quickly back to
southwesterly ahead of an approaching upper trough to the west for
Fri into the weekend. At the surface weak high pressure builds
across the region on Thu, then off of the Atlantic Seaboard late
Fri into Sat with the approach of a tropical low from the south.
Presently, the ECMWF lifts this feature into the FL Straits by
late Sat, northeast across southeast FL Sat night, and further
northeastward away from the peninsula on Sun, swept away by an
approaching front/upper trough combo. Model consistence and timing
of surface/upper features will play a key role going forward with
exact track/strength of this system.

After cooler than normal conditions again on Thu, temps should
rebound closer to climo Thu night-Fri with the onset of
return/onshore flow, then remain near climo next weekend. For now
have kept land areas dry thru Fri night, then introduce a small
threat for showers on Sat/Sun (moisture gradient could be tight from
north to south).

&&

.AVIATION...
Scattered SHRA/TSRA from KMCO vcnty to KDAB will transition
gradually SE overnight. Added some TEMPO groups for expected
SHRA/TSRA and also included some lower MVFR CIGs nrn terminals in
the 10z-14z time frame late tonight and early Tue morning. Cold
front will slowly push southeast across the area on Tue with sct
TSRA developing aft 15Z mainly MCO south.

&&

.MARINE...
Marine forecast is on track this evening with strongest convection
through midnight expected to affect nrn waters. Tonight(previous)...
S/SE pressure gradient will veer out of the S/SW supporting wind
speeds of 13-18 knots and seas 4 to 5 feet with up to 6 feet well
offshore. Will maintain Caution headline for the offshore waters of
Volusia and Brevard. There will be an increase in coverage of storms
pushing offshore this evening and overnight.

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.

&&

$$

Volkmer/Weitlich



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