Area Forecast Discussion
Issued by NWS Jacksonville, FL
Issued by NWS Jacksonville, FL
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679 FXUS62 KJAX 231115 AFDJAX Area Forecast Discussion National Weather Service Jacksonville FL 715 AM EDT Sun Jun 23 2024 ...New AVIATION... .SYNOPSIS... Issued at 411 AM EDT Sun Jun 23 2024 Early morning surface analysis depicts a lingering trough over coastal GA and SC, with weak high pressure (1017 millibars) otherwise centered over the lower Mississippi Valley. Aloft...deep-layered "Heat Wave" ridging has retrograded westward to a position over Texas and the lower Mississippi Valley, with troughing in place along the southeastern seaboard and the western Atlantic. Meanwhile, a potent shortwave trough was progressing across the Great Lakes region. Latest GOES-East derived Total Precipitable Water imagery nicely displays the weak trough axis that was in place locally, with PWATS for locations west of the U.S. Highway 301 corridor generally in the 1.6- 1.8 inch range, while a more humid air mass prevails east of U.S.-301, where PWATS were above 2 inches. The trough axis continues to fire convection over the offshore Atlantic waters north of St. Augustine and for the near shore waters from St. Augustine southward, with showers developing along the trough axis across portions of north central FL. Multi-layered cloudiness prevails across our area, especially for locations along and east of U.S.-301 that fall within the more humid air mass. Temperatures at 08Z were in the 70s inland, ranging to around 80 at coastal locations. Dewpoints remain in the 70s region-wide. && .NEAR TERM... (through Tonight) Issued at 411 AM EDT Sun Jun 23 2024 Low level troughing in place over the Savannah River Valley will progress slowly northeastward today, exiting the SC coast this evening. West-northwesterly mid-level flow on the western periphery of this trough will attempt to advect the drier air mass currently in place for locations west of U.S. Highway 301 eastward towards the I-95 corridor this afternoon. However, a weak pressure pattern prevailing across our region should allow for the Gulf and Atlantic sea breezes to develop by early afternoon, with PWAT values close enough to climatology to develop numerous afternoon and early evening showers and thunderstorms for northeast and north central FL, mainly due to mesoscale boundary collisions as convective trigger temperatures in the mid 90s are realized. Coverage will be scattered along the Gulf coast sea breeze in the Suwannee Valley and also along the Atlantic sea breeze for coastal southeast GA, with only isolated to widely scattered coverage for inland southeast GA as convective outflows pushing north and northwestward potentially overcome the below climatology PWAT values. The drier air mass advecting into our region will allow for downdraft CAPE values to climb to the 1,000-1,500 j/g range, which may allow for a few storms to become strong as mesoscale boundaries collide as storms pulse, with stronger activity capable of producing downburst winds of 40-50 mph, frequent lightning strikes, and heavy downpours. West-northwest steering flow will tend to focus mesoscale boundary collisions near the U.S. Highway 17 corridor late this afternoon, with activity likely migrating towards the I-95 corridor towards sunset. Seasonably hot temperatures will build over our region today, with highs for inland southeast GA and the Suwannee Valley soaring to the upper 90s, while locations elsewhere climb to the low and mid 90s. Dewpoints within the drier air mass are likely to crash through the 60s across inland southeast GA this afternoon, keeping maximum heat index values around 105. Values could approach Heat Advisory criteria in the Suwannee Valley this afternoon, with a general range of 103-107 degrees expected across our area. We will monitor forecast trends for counties such as Suwannee, Hamilton, Echols, and Gilchrist, which have the higher chances for touching the 108 degree threshold for a Heat Advisory. Convective outflows could keep activity percolating across northeast and north central FL through around midnight, with debris cloudiness potentially lingering overnight and developing west-southwesterly low level flow potentially developing isolated to widely scattered convection along the Nature Coast during the predawn hours on Monday that could sneak into western portions of Marion, southern portions of Gilchrist, and southwestern Alachua Counties before sunrise. A warm and humid air mass will keep lows generally in the mid 70s inland and the upper 70s to around 80 at coastal locations. && .SHORT TERM... (Monday through Tuesday night) Issued at 411 AM EDT Sun Jun 23 2024 Predominately S/SW flow will allow for seasonably hot temperatures and decent moisture Monday and Tuesday, with highs soaring into the mid to upper 90s, with a few areas in inland SE GA seeing highs of 100 on Tuesday. Heat indices both afternoons will top out in the 100-106 range, just below Heat Advisory criteria as of now. Diurnal showers and thunderstorms will develop as the Gulf sea breeze dominates with the southwesterly flow, the highest precip potential will be over NE FL. && .LONG TERM... (Wednesday through Saturday) Issued at 411 AM EDT Sun Jun 23 2024 A more typical summer-time like pattern will be in place, with both the Gulf and Atlantic sea breezes moving inland and interacting each day, sparking scattered to numerous shower and thunderstorm development. Temperatures will remain above normal through the week, with highs reaching the lower to upper 90s with lows in the 70s. && .AVIATION... (12Z TAFS) Issued at 712 AM EDT Sun Jun 23 2024 VFR conditions will prevail at the regional terminals through at least 18Z. Showers and thunderstorms will begin developing along the inland moving Gulf and Atlantic sea breeze boundaries on this afternoon, with activity merging near and east of the U.S. Highway 301 corridor during the late afternoon and early evening hours. We have included a PROB30 group at each terminal for briefly gusty winds and MVFR conditions during heavier downpours for the afternoon and early evening hours on Sunday. VFR conditions should then prevail by 04Z Monday. Southerly winds sustained at 5-10 knots overnight will shift to southwesterly after sunrise, with speeds increasing to around 10 knots by 16Z. The Atlantic and Gulf coast sea breezes will move inland on this afternoon, resulting in surface winds shifting to southeasterly and increasing to 10-15 knots at the SSI and SGJ coastal terminals towards 19Z, with these southeasterly winds reaching the CRG and JAX terminals as convection begins to increase in coverage after 20Z. After convection wanes on Sunday evening, expect southerly surface winds to remain sustained at 5-10 knots at the inland terminals and 10-15 knots at the coastal terminals. A slow tapering of southwesterly winds during the overnight hours is anticipated with prevailing winds of 7 to 12 knots. && .MARINE... Issued at 411 AM EDT Sun Jun 23 2024 Weak troughing will linger over our area today, with prevailing southwesterly winds this morning shifting to southeasterly over the near shore waters this afternoon as the Atlantic sea breeze moves inland. Showers and thunderstorms will be more numerous during the morning hours today offshore, with evening activity more likely for the near shore waters. Seas of 3-5 feet will prevail both near shore and offshore through tonight. Winds will shift to south-southwesterly and will surge to Caution levels of 15-20 knots throughout our local waters this evening outside of ongoing thunderstorm activity. West-southwesterly winds will prevail for the rest of the week as another trough settles over the southeastern states, with scattered thunderstorm chances prevailing each afternoon and evening as activity moves eastward across our local waters. Speeds will generally remain below Caution levels outside of thunderstorm activity, with seas of 2-4 feet prevailing throughout our local waters from Monday through Friday. Rip Currents: Developing onshore winds this afternoon will combine with an easterly ocean swell to create a moderate rip current risk at all area beaches. The easterly swell will begin to fade on Monday, dropping the risk to low for the southeast GA beaches, while onshore winds during the afternoon keep a lower end moderate risk at the northeast FL beaches. && .PRELIMINARY POINT TEMPS/POPS... AMG 97 75 96 75 / 30 20 30 20 SSI 92 78 93 79 / 40 20 30 30 JAX 96 75 96 75 / 60 30 50 20 SGJ 93 77 94 76 / 50 40 60 20 GNV 95 75 95 73 / 70 40 70 10 OCF 93 74 93 75 / 60 40 70 20 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AM...None. && $$