301 
FXUS62 KJAX 120750
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
350 AM EDT Mon Aug 12 2019

...HOT AND HUMID AGAIN TODAY WITH HEAT INDICES PEAKING NEAR
106-112...

...LOCALLY HEAVY RAINFALL LATE THIS AFTERNOON AND EVENING EXPECTED
NEAR THE I-75 CORRIDOR...

.NEAR TERM...Today and Tonight...

Similar story, different day. Oppressive heat is expected by 
noon and through most of the afternoon as thunderstorms eventually
develop and provide relief. While marginal in some areas, decided
to issue the heat advisory for the whole area once again until 6
PM. With the sea-breeze boundaries moving inland, scattered 
showers and thunderstorms will help provide relief to some areas 
fairly early in the afternoon. The longest duration areas
observing heat advisory conditions will most confidently be across
the Suwannee Valley and into SE Georgia where precipitation will
be fairly isolated and temperatures rise into the mid and upper
90s. With precipitation becoming more widespread by 3-4 PM, much 
of the advisory area in NE Florida will probably be below 
criteria. Regardless, it has been observed by numerous stations 
that even after the sea-breeze passes, the combination of slightly
cooler temperatures but higher surface dewpoints still realizes 
heat advisory worth conditions. True relief will come where 
convective activity occurs. 

Surface flow is very weak today so the east coast sea-breeze 
moves inland by early afternoon, initiating a few scattered 
showers and thunderstorms. Additional convection develops along 
the Gulf Coast sea-breeze and slowly moves inland. Mesoscale 
models are all in fairly good agreement that these boundaries 
merge along the I-75 corridor by late afternoon. With dewpoint 
temperatures in the mid to upper 70s, and air temperatures in the 
mid 90s, CAPE values are once again expected to be very high, 
despite warm temperatures aloft. Convective activity associated 
with the merging boundaries likely continues into the evening 
hours across the Suwannee Valley and into portions of SE Georgia 
before eventually fading. A few strong storms will be possible
with the merging boundaries, but heavy rainfall remains the main
concern. GOES derived PWATs suggest 2.3-2.7 inches present over 
the I-75 corridor. Isolated showers dissipate overnight with 
partly cloudy skies by Tuesday morning. 

.SHORT TERM...Tuesday and Wednesday...

By Tuesday, the upper level ridge axis begins to stretch more 
east to west versus the more amplified north to south setup that 
has persisted for multiple days. A wedge of drier air pushes into 
the northern zones, limiting coverage across SE Georgia. Further 
south, sufficient moisture remains, likely leading to another 
round of showers and thunderstorms, mostly driven by the sea- 
breeze boundaries moving inland. Temperatures are still warm aloft
(500 mb temps -3 to -4) so expect late initiation with activity 
continuing into the evening hours as mesoscale boundaries collide.
Ridge axis directly overhead on Wednesday with as a shortwave 
trough descends through the Midwest. The frontal boundary 
associated with the trough is expected to be north of the area, 
limiting convection to the diurnal processes that are typical this
time of year. Precipitation coverage will be slightly higher on 
Wednesday with the drier air offshore. 

Temperatures closer to climatological normals for NE Florida (low
90s) during the short-term however, SE Georgia still 3-5 degrees 
above normal (mid to upper 90s). Dewpoint temperatures in the mid 
to upper 70s keep heat index values elevated with some areas 
possibly reaching heat advisory criteria, especially across SE 
Georgia. 


.LONG TERM...Thursday through Monday...

With the shortwave trough digging into the Southeast, the more 
amplified pattern of a ridge to the west and a weak trough over 
the region resumes, especially below 300mb. With the trough 
positioned slightly west of the region, a deep tropical airmass 
continues to persist over the area. This favors numerous showers 
and thunderstorms throughout the long-term period. Models attempt 
to organize areas of vorticity along the stalled boundary, but all
that would be expected if something were to form would be 
enhanced rainfall. 

Temperatures finally drop to near normals with the trough 
breaking down the upper level ridge. Low 90s are forecast 
throughout the long-term. 


&&

.AVIATION...

Possible low cigs and vsby this morning mainly for GNV and VQQ 
due to recent rainfall. Otherwise VFR cigs look to prevail today 
for the TAFs with a good chance of showers and storms, with GNV having
the best shot of seeing convective impacts at the terminal. For now,
have included TEMPO group for them 18z-22z for MVFR and gusty winds, 
with rest of the TAFs mentioning VCTS. Winds will be light and 
variable early today, then becoming easterly in the aftn near 
8-12 kt, with exception at GNV where more southerly flow at 
5-10 kt is expected.

&&

.MARINE...

Weak flow across area waters continues to provide shallow sea
levels and below criteria winds. Winds do approach caution levels
for off shore waters toward Wednesday evening as a trough of low
pressure moves into the Southeast. The pressure gradient relaxes
toward the end of the week with winds decreasing to 10-15 knots. 

Rip Currents: Moderate risk for all area beaches due to onshore
flow during the afternoon, coupled with a lingering swell. 


&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  96  74  96  76 /  10  10  20  10 
SSI  90  78  91  79 /  20   0  10  10 
JAX  93  77  93  77 /  30  10  20  20 
SGJ  91  76  90  76 /  20  10  30  20 
GNV  93  76  92  76 /  60  70  60  30 
OCF  92  76  90  75 /  60  60  60  40 

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Heat Advisory from noon today to 6 PM EDT this evening for Baker-
     Bradford-Central Marion-Clay-Coastal Duval-Coastal Flagler-
     Coastal Nassau-Coastal St. Johns-Eastern Alachua-Eastern 
     Marion-Gilchrist-Hamilton-Inland Duval-Inland Flagler-
     Inland Nassau-Inland St. Johns-Northern Columbia-Putnam-
     Southern Columbia-Suwannee-Union-Western Alachua-Western 
     Marion.

GA...Heat Advisory from noon today to 6 PM EDT this evening for 
     Appling-Atkinson-Bacon-Brantley-Clinch-Coastal Camden-
     Coastal Glynn-Coffee-Echols-Inland Camden-Inland Glynn-Jeff 
     Davis-Northeastern Charlton-Northern Ware-Pierce-Southern 
     Ware-Wayne-Western Charlton.

AM...None.
&&

$$

McGinnis/Shashy/