Area Forecast Discussion
Issued by NWS Jacksonville, FL

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000 FXUS62 KJAX 041036 AFDJAX Area Forecast Discussion National Weather Service Jacksonville FL 536 AM EST Thu Mar 4 2021 .AVIATION... [Through 12Z Friday] Deck of IFR-MVFR cigs has pushed south of all TAF sites. Unlimited cigs and vsbys with light winds through the period. && .PREV DISCUSSION [313 AM EST]... .NEAR TERM [Through Tonight]... A very weak pressure pattern is in place over our area, with low pressure continuing to move off to the northwest across the Nrn Atlantic waters, a deep low pressure system spinning in place over the northeastern US, and a surface ridge of high pressure in Ontario that will dig slightly south toward the Great Lakes region through tonight. Locally, this is bringing light, generally northern winds and gradually clearing skies. Temperatures should peak in the upper 60s to low 70s across most of the area, with mid 70s in the greater Ocala area. Overnight, temperatures will dip into the low to mid 40s. .SHORT TERM [Friday Through Saturday]... Deepening troughing over New England will drive a backdoor cold front southward down the Carolina coast on Thursday night. Our local pressure gradient will begin to tighten from north to south on Friday morning as this dry cold front passes southward across our area, with northeasterly winds becoming breezy along the Interstate 95 corridor during the afternoon hours. High cloudiness will increase from the west during the afternoon hours, with inland highs warming to around early March climatology, with upper 60s for inland southeast GA, lower 70s for inland northeast FL and mid 70s for north central FL. Breezy onshore winds will keep coastal highs in the 60s. Meanwhile, a closed mid and upper trough migrating eastward across the southern Plains and the Ozarks on Friday will pivot southeastward on Friday night and will gradually weaken as it encounters a confluent flow pattern aloft along the eastern seaboard, compliments of the deepening trough over New England. Weak low pressure will traverse the Gulf of Mexico from Friday night through Saturday afternoon. Strengthening high pressure over the Great Lakes region in the wake of the cold frontal passage will begin to wedge down the southeastern seaboard, resulting in coastal trough development over our near shore Atlantic waters on Friday night. Isentropic lift will strengthen from west to east after midnight on Friday night, with increasingly convergent low level onshore winds and the developing coastal trough likely developing showers by the predawn hours along the northeast FL coast, with light showers then overspreading the rest of our area towards sunrise on Saturday. Thickening cloud cover will keep lows in the mid to upper 40s for inland locations along and north of I-10, ranging to the lower 50s along the northeast FL coast, where breezy conditions will continue overnight. Steady rainfall will develop on Saturday morning for locations along and south of I-10, with light rainfall expected for southeast GA that should depart before sunset as the aforementioned weakening trough migrates across our area. A tight local pressure gradient will exist throughout the weekend as strong high pressure builds southward from the Great Lakes towards the southeastern states. Cloud cover and rainfall will keep highs on Saturday below climatology, with highs likely remaining in the 55-60 range nearly area-wide. Rainfall amounts on Saturday are expected to range from 0.5 - 0.75 inches for locations from Gainesville to St. Augustine and points southward, while amounts along the I-10 corridor will generally run around 0.25 inches, with 0.10 or less for southeast GA. A few coastal showers may linger on Saturday evening in northeast FL as breezy northeasterly winds continue, while skies clear overnight from west to east. Clearing skies and cold air advection will drive lows down to the mid to upper 30s for inland southeast GA, with 40s elsewhere. Some patches of frost may be possible at wind sheltered locations north of Waycross towards sunrise on Sunday. .LONG TERM [Sunday Through Thursday]... Troughing aloft will persist over the eastern seaboard through early next week, creating an extended period of deep and dry northwesterly flow aloft that will keep temperatures below climatology through Tuesday morning. Breezy onshore winds will continue at coastal locations through at least Tuesday, and highs will mostly remain in the 60s, except upper 50s for coastal locations north of Jacksonville Beach on Sunday. Strong high pressure will build over the southeastern states on Sunday night and Monday. Frost appears to be increasingly likely across inland southeast GA and northern portions of the Suwannee Valley on Sunday night, as lows fall to the mid 30s, with lows elsewhere in the upper 30s to lower 40s inland and mid to upper 40s at coastal locations. Highs on Monday will remain in the 60s, except lower 70s for north central FL. Troughing aloft will then de-amplify as it moves off the U.S. eastern seaboard on Tuesday, with a dry west-northwesterly flow pattern remaining in place locally for the remainder of the week. Temperatures will rebound to near climatology on Tuesday, except at coastal locations, where persistent onshore winds will keep highs in the 60s. Onshore flow should weaken enough by Wednesday to allow highs to reach the 70s for coastal northeast FL, while lows continue to moderate to the 40s inland and 50s for coastal locations beginning on Tuesday night. .MARINE... Offshore seas of 4 to 6 feet today will subside to 3 to 5 feet by tonight. Generally north or northeast winds around 10 to 15 knots will prevail through the period, with a brief period of cautionary 15 to 20 knot winds this weekend as another weak low pressure system moves from the Gulf across central Florida. Rip Currents: Moderate risk of rip currents through Friday. .FIRE WEATHER... A drier air mass will funnel into our region today as northwesterly surface and transport winds increase to 5-10 mph after sunrise, with winds inland shifting to north-northwesterly this afternoon, while north-northeasterly winds increase to around 10 mph at coastal locations this afternoon. Marginally low daytime dispersion values are expected today for locations east of I-95. Minimum relative humidity values will fall to around 30 percent inland this afternoon. Breezy northeasterly surface and transport winds will then develop by the late morning hours on Friday. Light showers will develop after midnight on Friday night, followed by steady rainfall and likely low dispersion values on Saturday for locations south of I-10. Only light showers are expected for locations north of I-10. Breezy northeasterly winds will continue, with windy conditions developing at coastal locations on Saturday afternoon. .HYDROLOGY... Mostly minor river flooding continues for most of the main stem rivers in southeast GA as well as the Suwannee Valley, with the exception of Moderate Flooding on the lower Santa Fe near the Three Rivers Estates gauge. Levels on the lower Santa Fe should fall back to minor flood status by the weekend as the flood wave travels down the lower portion of the Suwannee River. && .PRELIMINARY POINT TEMPS/POPS... AMG 69 42 68 44 59 / 0 0 0 20 30 SSI 68 49 61 49 56 / 0 0 0 20 40 JAX 71 46 69 49 57 / 0 0 0 30 60 SGJ 67 50 67 52 57 / 0 0 0 30 80 GNV 73 43 73 50 57 / 0 0 0 40 70 OCF 74 45 76 53 59 / 0 0 0 40 80 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AM...None. &&

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