363 
FXUS62 KMLB 081511 AAA
AFDMLB

Area Forecast Discussion...UPDATED
National Weather Service Melbourne FL
1111 AM EDT Fri Oct 8 2021

.UPDATE...

Radar imagery currently shows isolated-to-scattered showers and 
lightning storms across the far Treasure Coast offshore waters 
(20-60nm) as they slowly move to the northeast away from east-
central Florida. A mid/upper level high remains off the southern
coast of Florida with deep west-southwesterly flow advecting
moisture from the Gulf of Mexico as seen on Goes-16 water vapor
imagery this morning. Also of note, an inverted surface trough 
remains located to the northeast - stretching from the Carolina 
coasts to the northeastern Florida coast; the National Hurricane 
Center has placed a 30% chance of tropical development for this 
wave over the next 48 hours. Observed skew-t soundings this 
morning indicated plenty of moisture across the area with 
precipitable water values in the 1.8"-2" range, in addition to, 
low-level RH values in the 80-90% range and drier air in the mid 
levels. Although ample moisture has advected into the region ahead
of a stationary boundary upstream of the Space Coast, the region 
has remained dry this morning with offshore flow on the east coast
of Florida keeping precipitation away from the coastline. 
Additionally, unlike yesterday, the east coast sea breeze will 
likely develop later today with a much more dominate west coast 
sea breeze present ahead of the aforementioned boundary. The 
boundary will continue to slowly inch its way closer to northern 
Florida as the upper-level ridge over the eastern half of CONUS 
finally breaks down through the weekend. Numerous showers and 
lightning storms are expected to develop this afternoon and into 
this evening as the west coast sea breeze moves inland and 
collides with east coast sea breeze boundaries, in addition to, 
outflow from storms upstream ahead of the stationary boundary. 
Given the anticipated more dominate west coast sea breeze, 
precipitation will likely form closer to the coast today with the 
best chance for rain and any isolated strong storms that develop  
mainly along and just to the west of I-95. 

Ingredients will be in place this afternoon for an increased 
threat for strong storms across the area outlined. Hi-res guidance
suggests that weak-to-moderate bulk shear values will be present,
EHI values between 1-2, over 3,000 J/kg CAPE values, absolutely 
unstable low-level lapse rates, cooler temperatures aloft, and 
very low LCL heights. Given the expected dynamics and increased 
lift, all modes of threatening weather will be possible this 
afternoon. The primary threats from any strong storms that develop
will be: heavy rainfall, flooding, wind gusts up to 60mph, small 
hail, and frequent cloud-to-ground lightning. A secondary threat 
exists for brief tornadoes and water spouts. Showers and storms
will slowly diminish and move offshore from the northwest to
southeast through this evening with most of the precipitation
ending within a few hours after sunset. High temperatures are on 
track to reach the upper 80s to low 90s this afternoon. 

&&

.PREV DISCUSSION... /issued 342 AM EDT Fri Oct 8 2021/ 

.DISCUSSION...

Current... A weak quasi-stationary boundary remains strewn across
the Deep South early this morning. A weak inverted surface trough
continues off of the Carolina coast. It remains unseasonably warm
and humid across ECFL with temperatures/dewpoints well into the 
70s. KMLB's 88D shows mainly dry conditions, but recently have 
seen some echoes appear along the Treasure Coast and adjacent 
coastal waters. A weak pressure gradient continues across the area
with light and variable to calm winds. Will continue to monitor 
should any shallow ground fog or low stratus develop early this 
morning, but for now continue to keep mention out of the 
grids/zones.

Today-Tonight... The weak front to the north will be slowly 
forced southward into the north-central FL peninsula during the 
day and evening. The driving force for this will be from a 
shortwave trough that will move into north FL late today and 
continue sliding southward this evening/overnight. This will allow
mid-level ridging to amplify over the southern Plains as we find 
ourselves in W/NW flow aloft. 500 mb temperatures are forecast to 
cool to -8.0C to -9.0C across ECFL by early this evening. PWAT 
values will surge in excess of 2 inches over most of central FL. 
The ECSB will develop again this afternoon and provide a focus for
ISOLD-SCT convective development across the coastal counties. As 
we head into late day and early evening, coverage and intensity of
showers/storms (60- 70pct) will increase with a majority of the 
activity piling up across the eastern peninsula. Morning storm 
steering flow is of a light westerly component, but the winds 
increase to around 10 kts later in the day which will push storms 
back toward the coast. Activity will wind down thru mid to late 
evening with cloud debris thinning overnight, once again. 

We are expecting a high coverage of precipitation late today/this 
evening and some cells again will be efficient precipitation 
producers (torrential downpours) with quick 2-3 inch amounts 
possible leading to minor/nuisance flooding. Additional storm 
threats include frequent lightning strikes and gusty winds of 40 to 
55 mph. Cooler temperatures aloft may allow for some small hail to 
reach the ground as well. With the unseasonably warm/moist 
conditions and weak atmospheric wind profile, we may have to remain 
vigilant for potential funnel clouds/waterspouts across the 
intracoastals and near shore Atlc waters later this morning and 
early afternoon. 

High temps today will reach the U80s to L90s. Low temperatures will 
fall into the L-M 70s.

The Weekend... A weak frontal boundary will work its way down the
peninsula Saturday as a highly amplified mid-upper level trough 
digs down the Atlantic seaboard, with the mid level trough axis 
just off or along the east central Florida coast. Copious 
precipitable water, 1.8 to 2.0 inches (90th percentile of PWAT 
values for early October), and ample lift from the frontal 
boundary and trough will result in rain chances up to 70 percent 
ahead of the front, and 40 to 50 percent behind as drier air 
settles in. How much of the area sees high PoPs will depend on the
front's position at peak daytime heating. For now have generally 
gone with 60 percent and higher south of I-4, and below 60 percent
to the north. Sunday, the mid- upper level pattern begins to 
settle into a configuration that will persist for the next several
days, as high pressure builds into the Gulf of Mexico and the 
aforementioned trough drifts slowly eastward towards the Bahamas. 
Sufficient surface moisture will remain for showers and storms to 
stay in the forecast, but significantly drier mid and upper levels
and subsidence from the GOMEX high, will inhibit stronger 
convection. Area-wide rain chances will range from 30-45 percent, 
with lower chances in the northern interior and higher chances 
south and long the coast where moisture and forcing is a little 
stronger. Afternoon highs will be in the upper-80s and overnight 
lows in the upper-60s to lower-70s.

Monday-Friday... High pressure settles into the Gulf of Mexico 
with mid-upper level ridging building across the eastern U.S. The 
trough east of Florida becomes quasi-stationary, with some models 
showing it developing a cutoff low. These two features will 
persist through the long term period, with models lacking 
agreement how these features will evolve past Thursday. Slight 
chance of rain area-wide, with generally onshore flow. Subsidence 
and dry air will limit stronger convection, particularly through 
the northern interior. Afternoon highs will be in the upper-80s 
and overnight lows around 70.

&&

.AVIATION...

Generally VFR conditions outside of any showers/storms. Will 
monitor this morning for any shallow ground fog/low stratus cloud 
threat, especially interior terminals. Confidence for this remains
low, again. Ample moisture with late day boundary collisions will
provide much of ECFL with higher than normal (NMRS SHRA's/SCT 
TSRA's) rain chances (greater than previous day). Continue to keep
"Vicinity" wording in TAFs, but foresee eventual additions of 
afternoon tempo groups for convection. Cooler temperatures aloft 
late today so could see a few strong storms with small hail. Tempo
MVFR invof convection. 

&&

.MARINE...

Today-Tonight... A weak pressure gradient continues 
across the area. Morning offshore component of wind will gradually
become onshore with formation and slow march inland of the ECSB. 
Speeds remain generally below 10 kts outside of storms and will 
transition to offshore again this evening and overnight. A higher 
than normal chance of lightning storms moving across the 
intracoastal and near shore Atlc waters is forecast for later this
afternoon and evening. A few storms may be strong. Frequent 
lightning, torrential downpours, funnel clouds/waterspouts, small 
hail and gusty winds in excess of 35 kts will all be in play. Seas
2-3 ft except for 4 ft well offshore, Cape northward. 

Saturday-Tuesday... Offshore winds will slowly veer from 
westerly/northwesterly on Saturday to southeasterly on Tuesday. 
Saturday and Sunday the wind field off the Volusia and Brevard 
coasts will be stronger, 5-10 knots, and more well defined than off 
the Treasure Coast where winds will be light and at times variable. 
By Tuesday fresh southeasterly winds 5-10 knots will occur through 
all offshore waters. Afternoon showers and storms likely Saturday, 
then lower chances Sunday through Tuesday. Seas generally 2-4 feet 
with some areas of 5 feet possible well offshore.

&&

.HYDROLOGY... The St. Johns River at Astor is forecast to remain 
near Action Stage through this weekend. Additional heavy rainfall is 
possible late today and again on Saturday.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  72  86  70  84 /  50  50  30  40 
MCO  74  88  71  87 /  50  50  20  40 
MLB  72  87  70  85 /  60  70  40  40 
VRB  72  87  70  86 /  60  70  40  40 
LEE  73  88  70  88 /  40  40  10  30 
SFB  72  87  70  86 /  50  50  20  40 
ORL  73  87  70  86 /  50  50  20  40 
FPR  71  86  68  85 /  60  70  40  40 

&&

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

$$

Fehling/Pendergrast