205 FXUS62 KJAX 170838 AFDJAX Area Forecast Discussion National Weather Service Jacksonville FL 438 AM EDT Mon Jun 17 2019 ...SCATTERED TO NUMEROUS AFTERNOON THUNDERSTORMS EACH DAY THIS WEEK... .Currently... Early morning surface analysis depicts the axis of Atlantic surface ridging extending westward along the FL/GA border. Meanwhile, weak low level troughing was pushing northward across south Florida. Aloft...southwesterly flow now prevails over our region as ridging aloft has shifted southward from the southwestern Atlantic over the Greater Antilles. Otherwise, a shortwave trough migrating across the Arklatex Region and approaching the Ozarks has spawned a Mesoscale Convective System (MCS) over the Texas Hill Country and the upper Texas coast. Latest GOES-East derived Total Precipitable Water imagery indicates that PWAT values have increased to 1.6 to 1.8 inches over southeast Georgia, while PWATs are now in the 1.8 to 2 inch range across most of northeast and north central Florida. A few sprinkles were already moving northward over our southeastern counties. Showers and thunderstorms are also increasing over the offshore waters adjacent to east central Florida just north of the low level trough that is moving northward, while a wave of convection is moving onshore onto the Treasure Coast counties south of Cape Canaveral. Mid and high altitude cloud cover is advancing northward over the northeast Florida coastal counties and the St. Johns River basin. Temperatures as of 08Z mostly ranged from the upper 60s to the lower 70s at inland locations, with mid and upper 70s prevailing at the coast. Dewpoints were generally in the upper 60s and lower 70s. .Near Term (this Morning through Tonight)... The slow moving shortwave trough currently approaching the Ozarks will progress eastward at a slightly faster rate of speed today, moving through the lower Mississippi, Tennessee and Ohio Valleys by late tonight. This feature will gradually deepen southwesterly flow aloft over our region late today, which will lift the low level trough axis and higher PWAT values over south Florida northward. Latest short-term, high resolution guidance indicates that convection associated with the low level trough will reach Cape Canaveral after sunrise and will then advect northward over Flagler County and the southern St. Johns basin by the late morning hours. Scattered to numerous showers and embedded thunderstorms will continue to progress quickly north- northwestward, crossing the Interstate 10 corridor early this afternoon and then moving into inland southeast Georgia during the mid to late afternoon hours. Convection should also develop this afternoon along an inland-moving Gulf coast sea breeze, with mesoscale boundaries from earlier convection along I-95 and U.S. Highway 301 interacting with this later developing convection to focus mid to late afternoon activity over the Suwannee Valley and along I-75 in north central Florida, where likely POPs were placed in the forecast grids. Relatively mild mid-level temperatures and weak lapse rates today should preclude severe thunderstorm development, with a few wet microbursts possible over inland locations late this afternoon as mesoscale boundaries collide, with the strongest activity possibly producing 40-50 mph wind gusts and locally heavy downpours. Plenty of cloud cover should keep highs in the upper 80s for locations east of U.S. Highway 301 in northeast and north central Florida, while convection developing late in the afternoon will allow highs to climb to the lower 90s across most of inland southeast Georgia. The low level trough axis will begin to shift north-northeastward over the Atlantic waters this evening, with a weak low pressure center possibly developing overnight just offshore of Cape Canaveral. Low level flow will become southwesterly by late tonight over northeast and north central Florida as this trough axis/weak surface low pressure center move northeastward over the coastal waters, where scattered to numerous showers and thunderstorms will blossom overnight. Isolated convection may impact coastal locations late tonight, and convection developing over the northeast Gulf of Mexico may also be advected onshore along the Florida Big Bend and Nature Coasts during the predawn hours, possibly moving into southern portions of the Suwannee Valley and west of I-75 in north central Florida towards sunrise. Plenty of mid and high altitude cloud cover should prevail over our region overnight, and lows will range from the lower 70s inland to the mid and upper 70s at coastal locations. .Short Term (Tuesday through Wednesday Night)... Tuesday...Mid level impulse/shortwave over the region will slowly shift offshore through the day as flow pattern becomes more southwesterly. Still expect diurnal heating to interact with deep moisture as PWATs remain close to 2 inches and expect numerous showers and storms with storm motion from the South-Southwest at 10-15 mph and will push storm activity closer to the I-95 corridor during the afternoon and early evening hours. Deep Moisture and cloud cover will hold Max Temps close to climo values in the upper 80s/near 90 degrees. Locally heavy rainfall will become a slightly bigger issue as PWATs exceed 2 inches in some spots with storm motion still less than 10 mph. Also, slightly cooler mid level temps with 500mb in the -7C to -9C range will help enhance strong thunderstorm potential, with isolated downdrafts pushing close to 50-60 mph in most intense activity. Wednesday...In the wake of trof pushing into the Carolinas, surface High Pressure ridge will rebuild south of the region across the Southern FL Peninsula and this will set up a faster West-Southwest flow across NE FL/SE GA and with tropical moisture with Precipitable Water Amounts (PWATs) still around 2 inches, expect numerous showers and storms to break out along the I-75 corridor of inland NE FL by late morning and track across the rest of the area through the afternoon hours reaching a stationary/pinned East Coast Sea Breeze at the Atlc Coast by late afternoon. Cool temps aloft of -9C at 500mb will help to enhance storm strength and along with faster storm motion expect isolated severe storms with downburst potential to 60 mph at times, and the cooler air aloft will support some hail potential in the most intense storms. Max Temps in the upper 80s where storms start up first, while areas towards the Atlc Coast will push to around 90 degrees with West to Southwest winds at 10-15G20 mph at times. Dewpoints in the mid 70s will support Heat Indices into the 100-105 range. .Long Term (Thursday through Sunday)... Thu/Fri...Faster West to Southwest flow still expected to continue across the deep south and along the North Gulf Coast and push a series of mid level impulses/shortwaves that will trigger daily numerous showers and storms that will develop along the Gulf Coast/Suwannee River Valley and push towards the E-NE while the flow will be strong enough to keep the East Coast Sea Breeze pinned along the Atlc Coast as Surface West to Southwest winds will increase to 10-15G20 mph each day. This will push the Max Temps into the 90-95 range each day with Heat Indices into the 100-105F range. While moisture levels will be slightly less with PWATs just under 2 inches and storm coverage may be less than on Mon/Tue, expect the faster storm movement to cover more territory and still lead to PoPs in the 50-70% range. The cooler and more unstable conds aloft will continue to support scattered strong to isolated severe storms with the faster storm motion will allow for better chances for wind gusts up to 60 mph in the most intense storms during the afternoon and early evening hours. Sat/Sun...High pressure at the surface and aloft will begin to build back into the region from the SW and push belt of faster westerly flow just north of the area. This will lead to slightly less storm coverage with PoPs in the 30-50% range. Max Temps into the lower to middle 90s will be more widespread in the afternoon due to less clouds and less storm coverage and will push Heat Indices to around 105 degrees all the way to the coast as enough lingering westerly flow will keep East Coast Sea Breeze close to the beaches. Still expect cool/unstable conds aloft to continue to support scattered strong to isolated severe storms at times. && .Aviation... Periods of MVFR visibilities will be possible at VQQ and GNV through around 12Z. Otherwise, VFR conditions will prevail, with light southerly surface winds developing shortly after 12Z. Showers and thunderstorms will develop over east central Florida and the St. Johns River basin during the mid to late morning hours and will move northward, reaching SGJ towards 16Z and then the Duval County terminals towards 17Z. Thunderstorms are likely to develop near SSI towards 18Z, but activity may stay just inland from the terminal. Thunderstorms will then shift inland towards GNV by 19Z. Due to uncertainties in timing and intensity, we opted to use PROB30 groups at each terminal except for SSI, where prevailing VCTS conditions are expected beginning around 18Z. Briefly gusty southeasterly winds and MVFR to IFR visibilities are expected with convection this afternoon. Activity may linger through around 00Z at GNV. The Atlantic sea breeze will push inland early this afternoon, with surface winds becoming southeasterly and sustained speeds increasing to 10-15 knots towards 16Z at SGJ and then after 17Z at the Duval County terminals and SSI. && .Marine... High pressure centered near Bermuda will drift slowly southward this week, with its axis shifting south of the northeast Florida waters by late Tuesday. Meanwhile, weak low pressure will develop near Cape Canaveral tonight and will move north- northeastward across the offshore waters on Tuesday and will then accelerate over the Gulf Stream waters off the Carolina coast Tuesday night. Showers and thunderstorms will increase over the waters south of St. Augustine this morning and will move northward, with additional activity developing over mainly the offshore waters tonight. A southerly wind surge this evening will bring sustained speeds up to near 15 knots. Seas of 2-4 feet will prevail through Tuesday. Winds will shift to west-southwesterly by Tuesday evening, with rounds of showers and thunderstorms impacting the waters each afternoon and evening through Friday. Outside of thunderstorm activity, caution level wind speeds will develop offshore beginning on Tuesday evening. Caution level wind speeds will then develop near shore during the evening wind surge on Wednesday, with Small Craft Advisory level speeds near 20 knots possible offshore during the Thursday evening wind surge. Caution level seas of 4-6 feet are expected to develop offshore beginning on Wednesday night. Prevailing Caution level winds are expected near shore and offshore late this week. Rip Currents: Winds will become onshore early this afternoon, creating a low-end moderate risk through around the time of low tide during the mid-afternoon hours. A low risk is expected at the southeast Georgia beaches. A low risk is then expected to prevail at all area beaches Tuesday through at least Friday. && .PRELIMINARY POINT TEMPS/POPS... AMG 92 71 91 72 / 50 30 70 30 SSI 88 77 86 75 / 10 30 60 30 JAX 89 72 91 73 / 50 10 70 30 SGJ 87 75 88 73 / 40 20 70 30 GNV 90 70 89 72 / 60 40 70 20 OCF 88 72 88 72 / 60 40 70 30 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AM...None. && $$ Nelson/Hess