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Area Forecast Discussion (AFD)

Issued by Melbourne, FL (MLB)

FXUS62 KMLB 221256

Area Forecast Discussion
National Weather Service Melbourne FL
855 AM EDT Fri Jun 22 2018


...Highest Heat Index Readings Likely Between 100F and 105F Areawide 
Again this Afternoon...

...Few Strong Storms Possible Again Late Today, Especially Eastern 
Peninsula and Southward from the Cape...

Current-Tonight...Low-level ridge axis remains well south of ECFL 
this morning. Surface flow SW/W areawide and relatively light. 915 
MHZ Cape wind profilers continue to show deep W/WSW flow from just 
above the surface through at least 8.0 kft with wind speeds 
averaging 10-15 kts. Latest 10Z KXMR sounding has just came in with 
a PWAT of 2.18 inches and 500 mb temp of -7.5C, which is a couple 
degrees cooler than this time yesterday. Deep moisture remains over 
the area with PWATs in excess of 2 inches, though the GFS forecasts 
some drier air making it into north of the I-4 corridor by late in 
the day and early evening. 

The ECSB will likely develop, but remain pinned near the coast, with 
greatest chance for any inland push well south of Volusia County. By 
early afternoon we should begin to see initial shower/storm activity 
firing along/ahead of the inland moving WCSB across WCNTRL FL. This 
activity should increase in coverage as the afternoon grows old with 
further mesoscale interactions igniting new convection along the 
way. Late afternoon outflows pushing towards the east coast will 
prompt pulse strong storms across coastal counties from Brevard 
southward lasting into at least early evening before dissipating 
and/or moving off the coast.

Mariners on inland lakes as well as the intracoastal/near shore 
Atlantic waters will need to keep an eye to the sky westward again 
today for developing/approaching storms. A reminder that lightning 
can strike at least 10 miles away from the parent thunderstorm. PoPs 
favoring the eastern peninsula and southward from Orlando where 
highest chances are look appropriate. Models also show favorable 
diffluence aloft late in the day across the southeastern FL 
peninsula. Continue with 40pct far northern reaches of our CWA and 
60pct south of MCO for late day/early evening convective fireworks. 

Main threats continue to be torrential downpours, cloud to 
ground/water lightning, small hail, and gusty winds to around 45 
mph. Local ponding of water (temporary) on roadways may lead to 
nuisance flooding.

Highs will average in the L90s again today and combined with 
moisture values will drive highest heat indices in the 100F to 105F 
range during the afternoon ahead of convective development. Cloud 
debris will thin again through late evening/overnight. Overnight 
mins forecast in the L-M70s with conditions humid.


.AVIATION...Remaining VFR outside of convection. A more active WCSB 
with the ECSB pinned again closer towards the east coast. Expect SCT-
NMRS shra's/tsra's with coverage increasing thru the afternoon and 
early evening. Storms will again pile up on the eastern peninsula 
with deep, but light westerly steering flow. Greatest threat today 
from MCO southward. Expect tempo IFR/MVFR CIGs/VSBYs in/around 
convection. Activity will dissipate/move off of the east coast this 
evening as cloud debris slowly thin overnight. 


.MARINE...Today-Tonight...Ridge axis remains shunted well south of 
the local coastal waters with early morning, light, offshore flow. 
The ECSB will develop, but likely remain pinned near the coast, 
perhaps minimal inland movement south of the Cape. Winds will still 
back to ESE/SE near the coast following ECSB formation. Storm 
steering flow remains westerly so expect offshore moving 
showers/storms again today with heaviest concentration south from 
the Cape and greatest timing late afternoon/early evening. 

Torrential downpours, small hail, cloud to water lightning, and 
gusty winds in excess of 35 kts all in play. Winds/seas locally 
higher invof of storms. Outside of storms seas generally 1-2 ft 
which will allow for favorable boating conditions. Mariners will 
need to keep an eye to the sky westward later today.


.HYDROLOGY...The St Johns River Above Lake Harney near Geneva is 
forecast to remain fairly steady at current levels, staying above 
Action Stage and below flood stage through early next week.