705 FXUS62 KJAX 261053 AFDJAX Area Forecast Discussion National Weather Service Jacksonville FL 553 AM EST Tue Jan 26 2021 .AVIATION... [Through 12Z Wednesday] Tricky forecast this morning with an upper level deck of clouds over all of our TAF sites preventing those previously forecast MVFR-IFR cigs and vsbys from developing...at the same time, nearby sites where upper level deck is less dense have dropped as expected. There's still a chance for those MVFR-IFR conditions near GNV and SSI this morning, with the fog now most likely to develop a little after sunrise and hang around only for an hour or two. After that, VFR conditions forecast through around 06Z and then scattered MVFR cigs will begin to filter northeastward into the area, with fog development expected near GNV again around 08Z. Winds from the southwest around 5-10 kts are anticipated through the period. && .PREV DISCUSSION [319 AM EST]... .NEAR TERM [Through Tonight]... At 1 AM, an area of surface low pressure was near the TN-WV border has a cold front extending southwestward from it across central TN, northern AL, central MS, and into southwestern LA. Out ahead of this front lies a very slow-moving broken line of showers and thunderstorms that stretches from west of Atlanta, GA through Birmingham, AL, then running south toward Hattiesburg, MA and Baton Rouge, LA. Model guidance shows this front will flatten out (becoming more east-west oriented) through the morning hours today then begin to stall across central GA and the northern Gulf coast by the evening hours. Our area will remain in the warm, humid air mass ahead of the system through the period. In the morning, this will mean fog and low ceilings across the region that could hang in through around 8 AM near Gainesville, FL and Ocala, FL. After that, we'll warm up into the the upper 70s to the low 80s. As storms ahead of the front run eastward through the afternoon hours and overnight, we'll see showers and isolated thunderstorms making their way into inland SE GA. These storms could linger in place near the Altamaha River through much of the night, similar to the current line near Birmingham this morning. With low level warmth, there will be some instability available to sustain storms long enough to possibly produce some damaging wind gusts of around 40-60 mph. Overnight, another round of low clouds and fog will likely develop south of the stalled frontal boundary. .SHORT TERM [Wednesday Through Thursday]... Low stratus and potentially dense fog will advect northeastward from the northeast Gulf of Mexico across a large portion of northeast and north central FL early during the predawn hours on Wednesday, with coverage of fog possibly extending into coastal southeast GA. Fog and stratus will lift by the mid-morning hours at these locations as southwesterly low level winds quickly strengthen before sunrise. A potent shortwave trough positioned over the southern Plains states early on Wednesday morning will move rapidly eastward, reaching the Ohio Valley by sunset and then moving offshore of the Mid-Atlantic states early on Thursday morning. A 160-knot jet streak at 250 millibars (35,000 feet) located south of this trough over the Ozarks and Tennessee Valley on Wednesday morning will weaken slightly as it traverses the southern Appalachians and the Carolinas, moving off the Carolina coast on Wednesday night. These features will induce weak cyclogenesis near Mobile Bay along a stalled frontal boundary during the predawn hours on Wednesday that will move east-northeastward across inland portions of southeast GA on Wednesday afternoon, emerging near the GA/SC coast on Wednesday evening. Deep west-southwesterly flow will be in place locally on Wednesday, with a ribbon of deep moisture surging into our area just ahead of the wave of low pressure along the front. A broken convective squall line is expected to take shape near the Altamaha/Ocmulgee Rivers during the late morning hours, and this line will surge southeastward across our area through the afternoon and early evening hours. Impressive speed shear will overspread our region, with bulk shear values of 60-70 knots forecast by model soundings. Lapse rates will be a limiting factor for a more significant severe weather event, as morning stratus will be slow to lift and insolation will be limited at most locations. However, model soundings depict ML CAPE values of 250-500 j/kg across southeast GA and the Suwannee Valley by early afternoon, and a few strong thunderstorms will be possible within the broken squall line, with strong wind gusts of 40-50 mph possible. Highs on Wednesday will climb to the mid and upper 70s, with a few lower 80s possible in north central FL. Convection within the broken squall line is expected to weaken towards sunset as activity approaches the I-95 corridor and north central FL. Showers will move offshore towards midnight, and cold air advection will then overspread our area on the heels of breezy northwesterly winds that will drive lows down into the 40s region-wide as skies rapidly clear from northwest to southeast during the overnight hours. Low pressure will strengthen as it moves quickly northeastward past the Gulf Stream waters on Thursday morning, with strong high pressure building southeastward from the Upper Midwest into the Ohio Valley by Thursday evening. Breezy north-northwesterly winds will shift to northerly by late afternoon, with speeds decreasing towards sunset as our local pressure gradient gradually relaxes. Despite full sunshine, cold air advection will keep highs in the 50s, except around 60 in north central FL. Thin cirrus could invade our skies within the deep northwesterly flow pattern on Thursday evening, but surface winds will decouple at inland locations, setting up a light freeze for most inland locations and patchy frost possibly extending into coastal locations. Lows will fall to the lower 30s inland, ranging to the mid and upper 30s at coastal locations. .LONG TERM [Friday Through Tuesday]... Deep northwesterly flow aloft will continue on Friday and Friday night as high pressure gradually weakens over the southeastern states. Fair skies and a dry air mass will allow highs to rebound to just slightly below climatology, with highs ranging from the upper 50s to lower 60s, except mid 60s in north central FL. Frost will be possible at inland locations on Friday night, where lows will fall into the 30s, while low level onshore flow keeps coastal lows in the 40-45 degree range. Low pressure will emerge from the lee side of the Rockies into the southern Plains States on Saturday afternoon as high pressure builds over the Great Lakes region and the Mid-Atlantic states, wedging down the southeastern seaboard late in the day. Low level winds will become southeasterly, and developing zonal flow aloft will result in highs climbing into the 60s, except around 70 in north central FL. Low pressure traversing the Ozarks and Missouri Valley on Saturday night and Sunday will drag a cold front into the lower Mississippi Valley by Sunday afternoon, resulting in strengthening southwesterly flow for our area, with warm air advection boosting highs into the 70s, except upper 60s for locations north of Waycross, where scattered showers are forecast to arrive late in the day. Secondary low pressure will develop over the southeastern states by late Sunday, with the cold front slated to cross our area during the overnight hours, accompanied by scattered showers. Breezy northwesterly winds in the wake of this front will cool highs back towards early February climatology early next week, with lows falling back to the 30s at inland locations by Monday night. .MARINE... A cold front will stall to the west of our local waters today. On Wednesday morning, an area of low pressure will develop along the front near the Florida panhandle, which will allow the system to accelerate northeastward in the afternoon across the Georgia coastal waters, dragging the cold front across our area during the evening hours. As the front moves in, showers and isolated thunderstorms will move over our coastal waters Wednesday into Wednesday night. Along and behind the front, westerly and then northwesterly winds will increase across the coastal waters, with occasional Gale Force wind gusts possible offshore and Small Craft Advisory conditions developing near shore. Small Craft Advisory conditions will persist for the offshore waters through early Friday. Weakening high pressure will then build into our region on Friday afternoon, resulting in decreasing winds and subsiding seas. Rip Currents: Low risk of rip currents at NE FL and SE GA beaches through Wednesday. .FIRE WEATHER... Strong south-southwesterly transport winds will develop shortly after sunrise across inland southeast GA, with breezy transport speeds elsewhere. Breezy southwesterly surface winds are expected area-wide early this afternoon. Scattered to numerous showers and a few embedded strong thunderstorms will then traverse our region from northwest to southeast on Wednesday, with activity moving off the Atlantic coast during the early evening hours. Strong southwesterly surface and transport winds are expected area-wide. A colder and drier air mass will then plunge over our region late Wednesday night and Thursday, with breezy north-northwesterly surface and transport winds expected through the early afternoon hours on Thursday before diminishing late in the afternoon. .HYDROLOGY... Storm total rainfall values over inland SE GA could be around 1-3" through Wednesday night, with totals of 1" or less further south. Most of our area rivers are currently at low levels and most of SE GA and NE FL area have seen 30 day rainfall departures 1-3" below normal, so this rainfall is expected to be beneficial and not to cause any widespread flooding issues. That said, isolated areas could see higher totals from storms which could lead to localized flooding issues. && .PRELIMINARY POINT TEMPS/POPS... AMG 77 63 75 42 54 / 30 40 90 30 0 SSI 74 61 74 45 54 / 10 10 50 60 0 JAX 80 62 79 45 56 / 10 10 40 50 0 SGJ 77 61 79 48 55 / 10 10 30 30 0 GNV 78 60 79 46 59 / 10 10 50 30 0 OCF 79 60 79 47 61 / 10 10 50 30 0 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AM...None. &&