textproduct: Jacksonville

KEY MESSAGES

For the latest NE FL and SE GA Daily Key Messages please visit: https:/www.weather.gov/media/jax/briefings/nws-jax-briefing.pdf

- Elevated Fire Danger at Inland Locations this Afternoon. Near Critically Low Humidity Values Expected Along with Ongoing Drought Conditions

- Near Record High Temperatures Today & Thursday

- Fire Weather Watch for Locations East of U.S.-301 on Thurs Afternoon & Evening. Gusty Southwesterly Winds, Near Critically Low Humidity& Ongoing Drought Conditions

- Strong to Isolated Severe Thunderstorms on Thursday Afternoon & Evening. Main Impact Area: Locations Along and North of the Interstate 10 Corridor. Main Hazards: Wind Gusts of 40-60 mph, Frequent Lightning Strikes & Isolated Tornadoes

- Scattered to Numerous Thunderstorms from Friday Afternoon through Monday

NEAR TERM /THROUGH TONIGHT/

Main Highlights This Period:

- Warm Temperatures Today

- Moderate Risk of Rip Currents at All Area Beaches

Dry weather conditions will continue through today and into tonight as high pressure over the region moves off towards the east and a southwesterly flow develops over the region ahead of the advancing cold front pressing in from out of the northwest. Southwesterly diurnal winds will act to keep the east coast sea breeze pinned nearer to the coast. Early morning fog developments, primarily along and west of the I-75 corridor, will disperse by midmorning. High temperatures will rise to be near record high levels this afternoon with max temps rising into the mid 90s over inland areas and in the mid to upper 80s along the coastline. Overnight low temperatures will drop down into the mid to upper 60s for inland areas and in the upper 60s and lower 70s for counties along the coastline.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/

Main Highlights This Period:

- Fire Weather Watch on Thursday Afternoon and Early Evening for Locations East of U.S. Highway 301 in Northeast and North Central FL

- Strong to Isolated Severe Thunderstorms Possible for Locations Along and North of Interstate 10 on Thursday

- Near Record High Temperatures Possible Across Portions of Northeast and North Central FL on Thursday Afternoon

- Scattered Thunderstorms Area-Wide on Friday and Friday Night

Deep-layered riding over the southeast Gulf and the FL peninsula on Thursday will flatten while shifting southward on Thursday night and Friday. Meanwhile, troughing digging southeastward from the Great Lakes and Mid-Mississippi Valley will direct a shortwave trough eastward from the Ozarks on Thursday morning, across the Tennessee Valley on Thursday afternoon, with this feature filling as it crosses the Carolinas on Thursday night. This troughing will drive a cold front across the southeastern states on Thursday, with this boundary decelerating as it crosses southeast GA on Thursday night and then stalling along the I-10 corridor on Friday as fast zonal flow prevails across the southeastern states in the wake of the filling shortwave that will progress offshore. Otherwise, a cutoff trough currently spinning over the Desert Southwest will eject into the zonal flow pattern by late Friday, traversing west Texas on Friday night.

Our local pressure gradient will tighten downstream of the aforementioned troughing and cold front on Thursday morning. Breezy southwesterly winds will overspread our area by the mid to late morning hours, and stout ridging over the FL peninsula will drive near record heat all the way to area beaches on Thursday afternoon. Uncertainties in the forecast arise with a potential early start to convection on Thursday morning across southeast GA. This convection could spread cloud cover southward to the I-10 corridor by the late morning and early afternoon that could put a cap on instability. However, strong subsidence across the FL peninsula will likely result in a thin enough cirrus layer for highs to soar to the mid and possibly upper 90s for locations east of the U.S. Highway 301 corridor, with dewpoints crashing through the lower 60s could create Red Flag Conditions as southwesterly winds strengthen to 15-20 mph with frequent gusts of 25-30 mph. Heat index values may approach or even exceed 100 degrees on Thursday afternoon along the I-95 corridor in northeast FL, depending on just how much mixing occurs that would lower dewpoints during the afternoon hours. Highs will likely remain in the 80s for much of inland southeast GA, although lower 90s could occur in the Okefenokee Swamp and low to mid 90s for coastal southeast GA if convection does not develop until the afternoon hours.

A narrow ribbon of deep moisture, featuring PWATs of 2 - 2.25 inches, will pool just ahead of the decelerating cold front on Thursday, which should create scattered to numerous showers and thunderstorms across southeast GA and northern portions of the Suwannee Valley. Timing of this convection remains in question, and convection should weaken as it moves south of the I-10 corridor on Thursday evening as it encounters the more stable air mass associated with the retreating deep-layered ridge. An impressive jet streak of at least 140 knots at 250 millibars (around 35,000 feet) will be traversing the Tennessee Valley and southern Appalachians, providing increasingly diffluent flow aloft, while a low level jet of 40-50 knots at 850 millibars (around 5,000 feet) traverses southeast GA during the afternoon hours. Model soundings indicate that ML CAPE values will rise to the 1,000 - 1,500 j/kg range across southeast GA on Thursday, and these factors have helped maintain a "Marginal" risk for severe thunderstorm development (level 2 of 5) by the Storm Prediction Center on Thursday. Convective outflows and hot temperatures could maintain strong to isolated severe storms along the I-10 corridor, and the SPC has thus expanded the risk southward through the Suwannee Valley and northeast FL into the early evening hours on Thursday.

Convection ahead of the frontal boundary will likely weaken on Thursday evening across northeast FL, with multi-layered cloud cover expected across our region on Thursday night as the front slowly moves through southeast GA and likely stalls along the I-10 corridor towards sunrise on Friday. Weak cool air advection behind the frontal passage should drop lows back into the 60s for inland portions of southeast GA, while lows remain in the lower 70s elsewhere.

Fast zonal flow across the Deep South will result in the frontal boundary stalling on Friday along the I-10 corridor. Weak shortwave energy embedded within the zonal flow pattern will enter our area from the west during the afternoon hours, potentially igniting scattered convection. Low level flow will weaken, however, and the best forcing associated with the previously cutoff shortwave trough traversing west Texas will keep better forcing to the west of our region. Cloud cover and weak cool air advection should keep highs in the upper 70s and lower 80s across southeast GA, while highs south of the stalled front likely soar to the lower 90s again across north central FL, with highs elsewhere across northeast FL generally in the mid to upper 80s. Although timing is uncertain, better forcing associated with the upstream shortwave trough could increase convection after midnight on Friday night, especially for locations north of I-10 per latest model blends. Lows will range from the 60s for locations along and north of I-10 to the lower 70s for north central and coastal northeast FL.

LONG TERM /SATURDAY THROUGH TUESDAY/

Main Highlights This Period:

- Scattered to Numerous Showers and Thunderstorms Continue through Monday.

- Strong to Severe Storms Possible on Sunday and Sunday Evening.

- Beneficial Rainfall Expected, Especially Across Southeast GA.

- Slightly Cooler and Less Humid Conditions Arrive Monday Night through Tuesday Night.

Potent shortwave troughing traversing Texas on Saturday will move across the Lower Mississippi Valley on Sunday and the rest of the southeastern states on Sunday night. Meanwhile, a stalled frontal boundary will remain in place across our area this weekend, followed by a cold frontal passage currently slated for Monday as the aforementioned shortwave trough gets absorbed by a progressive northern stream trough that will be migrating across the eastern U.S. Scattered to numerous showers and thunderstorms will continue across our region on Saturday, with a few stronger storms being possible during the afternoon and evening hours, depending on cloud cover and available instability. A higher threat for strong to severe storms appears likely on Sunday, with the shortwave trough providing another potent low level 40-50 knot jet at 850 millibars (around 5,000 feet). Thick multi-layered cloud cover on Saturday will likely keep highs in the 80s, except around 90 possible for locations south of the stalled front in north central FL. Lows on Saturday night will range from the mid 60s across inland southeast GA to the lower 70s for north central and coastal northeast FL. Highs on Sunday should nudge upwards to the upper 80s and lower 90s, potentially fueling more instability for stronger convection late in the day. Lows on Sunday night will only fall to the upper 60s and lower 70s ahead of the approaching front.

Model blends keep scattered to numerous showers and thunderstorms in place on Monday, but timing and intensity remain in question, depending on when the cold front crosses our area. Highs will likely remain in the 80s, although lower 90s could be possible along the I- 95 corridor if the cold frontal passage is delayed until the afternoon hours. Highest rainfall amounts will the stalled front and early week cold frontal passage will likely occur across southeast GA, where widespread totals in excess of 1 inch appear to be likely.

Troughing aloft will then dig into the southeastern states on Monday night and Tuesday, with high pressure building over the southeastern states shifting winds to northwesterly on Monday night, northerly on Tuesday morning, and then northeasterly by Tuesday afternoon and night. Clearing skies and cool air advection following the frontal passage will drop lows to the upper 50s for inland southeast GA and the 60s elsewhere by Tuesday morning. Highs on Tuesday will range from the upper 70s to the lower 80s across southeast GA and coastal northeast FL to the mid and upper 80s for the Suwannee Valley and north central FL. Radiational cooling at inland locations on Tuesday night will drop lows to the 50s and lower 60s, with an onshore breeze keeping coastal lows in the mid to upper 60s.

AVIATION /12Z WEDNESDAY THROUGH 12Z THURSDAY/

Predominantly VFR conditions will persist through the majority of the forecast period with reduced ceilings and visibilities this morning potentially affecting GNV due to smoke from a fire to the south drifting into the vicinity. Mild winds will strengthen from out of the south and southwest for inland sites with south-southeasterly onshore winds affecting coastal sites and extending into CRG and JAX.

MARINE

High pressure centered near Bermuda will weaken as a cold front enters the southeastern states tonight. Southerly winds this morning will shift to southeasterly this afternoon, with speeds increasing to Caution levels by early this evening both near shore and offshore. The cold front will slow its forward progress as it approaches our area on Thursday, with breezy southwesterly winds expected across our local waters through Thursday evening. Showers and thunderstorms will be possible from late Thursday afternoon through early Thursday evening ahead of this front, with strong to isolated severe thunderstorms possible, mainly across the Georgia waters. This front will slow its forward progress on Friday morning and will then stall by Friday evening across the northeast Florida waters. Scattered to numerous showers and thunderstorms will be possible from Friday afternoon through the weekend, with another round of strong to severe thunderstorms possible on Sunday afternoon and evening, well in advance of another cold front that will be entering the southeastern states. This front will sweep southeastward across our local waters on Monday, followed by high pressure briefly building over the southeastern states on Monday night and Tuesday.

Rip Currents:

Onshore winds will become breezy this afternoon, with these winds combining with a slowly fading easterly ocean swell to create a lower end moderate risk at all area beaches. Breezy southwesterly winds will yield a low risk at area beaches on Thursday. Winds will shift to northeasterly on Friday, likely resulting in a moderate risk at area beaches.

FIRE WEATHER

- Elevated Fire Danger This Afternoon At Inland Locations

MARGINALLY HIGH DAYTIME DISPERSION VALUES POSSIBLE ON FRIDAY - Afternoon For North Central Florida

Dry weather is expected to prevail area-wide through Wednesday night. An Elevated Fire Danger is expected this afternoon at inland locations, as humidity values fall to near critical thresholds and elevated mixing heights create high daytime dispersion values for inland portions of southeast Georgia, where breezy southwesterly transport winds are expected, while good to marginally high values prevail elsewhere inland.

A Fire Weather Watch is in effect for locations east of the U.S. Highway 301 corridor from Thursday afternoon through early evening as southwesterly transport winds strengthen, with breezy surface speeds developing area-wide by the mid to late morning hours. Although some uncertainty exists regards to timing of showers and thunderstorms traversing our area along with associated cloud cover, current guidance indicates enough sunshine along the I-95 and U.S. Highway 17 corridors for hot temperatures to lower humidity values to near critical thresholds by early afternoon, with elevated mixing heights creating high to very high daytime dispersion values area- wide. Strong to isolated severe thunderstorms are expected to develop across southeast Georgia, likely by the late morning or early afternoon hours, with activity potentially moving southward towards the Interstate 10 corridor by the late afternoon or early evening hours.

Scattered showers and thunderstorms will remain possible area-wide on Friday, with an increasing coverage possible during the weekend, potentially providing beneficial rainfall to our region. Breezy southwesterly surface and transport winds are likely to continue across north central Florida on Friday, creating good to marginally high daytime dispersion values. Poor values are currently forecast for locations north of I-10, where cloud cover and cooler temperatures are expected as transport winds shift to west- northwesterly.

FOG POTENTIAL AND OTHER REMARKS: Patchy to areas of locally dense fog will be possible across portions of the Suwannee Valley and inland southeast Georgia during the predawn and early morning hours on Thursday.

CLIMATE

Record High Temperatures at NE FL/SE GA climate sites for:

Wed, May 6: JAX: 96/2012 CRG: 96/2012 GNV: 96/1955 AMG: 95/2012

Thu, May 7: JAX: 94/1977 CRG: 94/1977 GNV: 96/1955 AMG: 93/1962

PRELIMINARY POINT TEMPS/POPS

AMG 90 65 85 64 / 0 10 60 10 SSI 84 71 90 70 / 0 0 30 20 JAX 95 68 97 70 / 0 0 10 10 SGJ 90 70 97 72 / 0 0 0 0 GNV 95 65 93 71 / 0 0 0 10 OCF 95 67 92 72 / 0 0 0 0

JAX WATCHES/WARNINGS/ADVISORIES

FL...Fire Weather Watch from Thursday afternoon through Thursday evening for FLZ024-038-124-125-132-137-138-140-225-232- 233-237-325-333-425-433-533-633. GA...None. MARINE...None.