822 FXUS62 KJAX 071558 AFDJAX Area Forecast Discussion National Weather Service Jacksonville FL 1058 AM EST Thu Jan 7 2021 ...SHOWERS ARRIVE LATE THIS AFTERNOON IN THE SUWANNEE VALLEY AND INLAND SOUTHEAST GA... ...BREEZY WESTERLY WINDS AND SEASONABLY COOL WEATHER ON FRIDAY... .UPDATE... Late morning surface analysis depicts a weak coastal trough situated over the near shore Atlantic waters that is in the process of lifting northward as high pressure (1024 millibars) shifts eastward towards the Mid-Atlantic coast. Meanwhile, low pressure (1007 millibars) was moving eastward across the lower Mississippi River Valley, with a cold front extending southward through central portions of the Gulf of Mexico and a warm front lifting northward towards the FL panhandle coast. Showers have overspread the FL panhandle as isentropic lift strengthens along and north of the warm front. Otherwise, our local pressure gradient continues to tighten downstream of this approaching storm system, with breezy easterly winds now observed at most inland locations and northeast winds persisting along the immediate coast as of 16Z. Temperatures were rising through the upper 50s across southeast GA and into the mid 60s for most of northeast and north central FL as mid and especially high cloud cover are thickening from west to east. Winds will continue to slowly increase and will veer to southeasterly early this afternoon as low pressure pivots eastward into the Deep South. Highs will climb into the lower 70s for locations along and south of Interstate 10, where cloud cover will not thicken nor lower until the late afternoon hours, while highs elsewhere generally climb to the mid and upper 60s, except for lower 60s near the Ocmulgee/Altamaha Rivers and along the immediate southeast GA coast. Latest short-term, high resolution guidance shifts shower activity eastward from the FL panhandle into the Suwannee Valley and inland southeast GA during the 3-4 PM hour, with activity then migrating eastward towards U.S. Highway 301 towards sunset and then the I-95 corridor during the early to mid-evening hours. Although a 40-45 knot low level south-southwesterly jet at 850 millibars (5,000 feet) will enter our region late this afternoon and early this evening, instability will only be elevated in nature, and thunderstorm activity is not anticipated as low pressure exits the southeast GA coast during the predawn hours and this storm system's cold front sweeps offshore of the northeast FL coast before sunrise. Shower activity should exit the northeast FL coast shortly after midnight, with a period of thicker stratus or stratocumulus continuing ahead of the front through the overnight hours. Winds will shift to west- southwesterly during and after the frontal passage, with cold air advection dropping lows into the upper 40s for inland southeast GA and the western Suwannee Valley, with low and mid 50s expected elsewhere. Breezy westerly winds will quickly develop after sunrise on Friday, with wrap-around moisture likely resulting in mostly cloudy skies for much of the day across southeast GA as low pressure strengthens as it accelerates northeastward off the U.S. eastern seaboard. && .AVIATION... [Through 12Z Friday] VFR conditions will prevail at the regional terminals through at least 23Z. Showers will approach the GNV and VQQ terminals from the west towards 23Z, bringing brief periods of MVFR conditions at these terminals through around 04Z. Showers will then reach the rest of the terminals after 01Z, brining brief periods of MVFR conditions through around 05Z. MVFR ceilings of 2,000-3,000 feet will then be possible through around 12Z at the regional terminals as surface winds shift to westerly at 5-10 knots. VFR conditions should then prevail after 12Z as ceilings rise to 3,000-4,000 feet and westerly surface winds increase to 10-15 knots. && .MARINE... A coastal trough situated over our near shore waters this morning will lift northward this afternoon as low pressure over the lower Mississippi Valley pivots eastward across the Deep South, emerging off the South Carolina coast towards sunrise on Friday. Southeasterly winds will strengthen this afternoon, with Small Craft Advisory conditions developing over the offshore waters adjacent to northeast FL shortly after noon and then over the offshore Georgia waters towards sunset. Seas will build to 5-7 feet by late afternoon for the offshore FL waters and 4-6 feet for the southeast GA waters, where Small Craft should exercise Caution this afternoon. This storm system's cold front will push eastward through our region late this evening and overnight, accompanied by showers. Seas offshore will build to 6-9 feet tonight, while seas of 3-5 feet expected near shore. Low pressure will strengthen as it accelerates northeastward off the U.S. eastern seaboard on Friday, keeping strong offshore winds and elevated seas in place through Saturday. Winds and seas will briefly diminish late this weekend as high pressure builds into the southeastern states, followed by the next storm system quickly developing along the central Gulf coast region Sunday night and then moving over our region by Monday night and Tuesday. Rip Currents: A high risk of rip currents continues today at the northeast FL beaches due to a long period northeasterly ocean swell combining with strengthening onshore winds. A moderate risk is expected at the southeast GA beaches. The lingering long period swell will keep a moderate rip current risk at all beaches on Friday, with a low risk likely on Saturday as breezy offshore persist. && .FIRE WEATHER... Strengthening easterly surface and transport winds late this morning will shift to southeasterly this afternoon, creating good dispersion values area-wide that will border on marginally high values by the mid afternoon hours. Showers will impact our region late this afternoon and especially this evening, followed by strong westerly surface and transport winds on Friday. Increasing cloudiness will keep dispersion values and humidity levels higher on Friday afternoon in southeast GA, while a drier air mass and good dispersion values are forecast for northeast and north central FL. && .PREV DISCUSSION [526 AM EST]... .NEAR TERM [through Tonight]... High pressure will be centered to the north this morning, as a trough develops along the FL coast. This trough will lift north northeast through the morning and afternoon, and is expected to remain just off shore, along with much, if not all of its associated showers. The precipitation associated with the approaching low pressure system will reach far western counties around 18z, then spread east through the afternoon, reaching the east coast around sunset. The low center will move to the northeast around midnight, with the cold front pushing to the east of forecast area during the overnight. Shower activity will decrease from west to east during the overnight. Instability is expected to be limited, so have not included Thunderstorms in the forecast. Can not completely rule one out, but chance too low for mention at this time. Temperatures will trend a little above normal over SE GA Today, but warm advection on southerly flow will push readings above normal into the 70s over NE FL, except for the Suwannee valley. The FL beaches will hold below 70 though due to the onshore flow across the relatively cooler coastal waters. .SHORT TERM [Friday Through Saturday Night]... Friday...Low pressure continues to intensify as it tracks to the Carolina Coast and West Winds will increase to 15-25 mph with gusts up to 35 mph by the afternoon. Cooler airmass will hold Max Temps at below normal levels with Highs in the 50s across SE GA and near 60 across NE FL under Mostly Cloudy skies. Lagging mid-level trof axis will likely not have enough moisture to trigger much in the way of shower activity, but a few sprinkles will be possible in the lower clouds through the day, mainly across SE GA, but overall measurable rainfall chances remain around 10% or less. Friday Night...Partial cloud cover lingering on the back side of the low pressure system and elevated Northwest winds at 5-10 mph combined with cool temps falling into the upper 30s over inland areas and lower 40s along the coast will push Wind Chill readings down into the lower to middle 30s by sunrise. Saturday...Chilly airmass settles into the region on Northwest winds at 10-15 mph and clearing skies by the afternoon hours as High Pressure builds in from the West. Below normal temps continue with Highs only in the 50s area-wide. Saturday Night...High pressure ridge extends into the region from the Northwest and under mostly clear skies and light NW/near calm winds expect a frosty night with lows in the lower 30s across inland SE GA/Suwannee Valley with a light freeze now possible, and mid to upper 30s closer to the Atlc coast with plenty of frost expected and Frost/Freeze headlines may be required around sunrise. .LONG TERM [Sunday Through Wednesday]... Sunday...Mostly sunny and still cool as High Pressure moves north of the region and expect light and variable winds but still below normal temps with Highs still mostly in the 50s/near 60 degrees. Cloud cover starts to increase ahead of the next system Sunday Night and while inland temps may still fall into the mid/upper 30s, less frost formation is expected. Monday...The GFS/ECMWF 00z runs have come into better agreement with low pressure system tracking out of the Gulf of Mexico and into South GA by Monday Evening and expect to have another of gusty showers by the afternoon/evening hours with an isolated thunderstorm possible, a very similar scenario to today's (1/7) system. Max temps rebound into the 60s, but overall fast speed of the system prevents deep moisture return on the latest model runs. Tuesday...Depending on speed of exiting low pressure system, a few morning showers are possible otherwise clearing skies and seasonable temps with highs in the 60s and breezy West winds again. Wednesday...Cool High pressure builds into the region from the Northwest and temps return to below normal levels with Highs around 60 and lows in the 30s inland/near 40 Atlc Coast, and some frost will be possible Tue and Wed nights. && .PRELIMINARY POINT TEMPS/POPS... AMG 62 47 55 37 52 / 70 90 10 10 0 SSI 63 53 59 40 52 / 40 60 10 10 0 JAX 71 51 59 39 56 / 30 60 10 10 0 SGJ 71 56 64 42 56 / 10 70 10 10 0 GNV 71 52 61 39 57 / 50 70 10 10 0 OCF 74 53 63 39 58 / 40 50 10 10 0 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...High Rip Current Risk until 7 PM EST this evening for Coastal Duval-Coastal Flagler-Coastal Nassau-Coastal St. Johns. GA...None. AM...Small Craft Advisory from 1 PM this afternoon to 4 PM EST Saturday for Waters from Fernandina Beach to St. Augustine FL from 20 to 60 NM-Waters from St. Augustine to Flagler Beach FL from 20 to 60 NM. Small Craft Advisory from 10 PM this evening to 10 AM EST Saturday for Waters from Altamaha Sound GA to Fernandina Beach FL from 20 to 60 NM. &&