560 FXUS62 KJAX 200540 AFDJAX Area Forecast Discussion National Weather Service Jacksonville FL 137 AM EDT Sat Mar 20 2021 .AVIATION... [Thru 06z Sunday] Gusty northerly surface winds expected through the period, along with MVFR Cigs. There may be breaks at times from the lower CIGs...but have CIGs BKN020-030 thru TAF period. Have VCSH particularly for sites near coast later Today and Tonight. && .PREV DISCUSSION [844 pm EDT]... .UPDATE... Forecast remains on track. A cold front approaching from the northeast has made it into our northeast SE GA counties and will cross the rest of the area overnight tonight. Clouds will move in behind the front, and temperatures will cool. Overnight low temperatures tonight will be low-to-mid 40s in SE GA and upper 40s to lower 50s in NE FL. && .NEAR TERM [Through Tonight]... Low level ridge of high pressure in the Great Lakes region this afternoon will build south-southeastward into the Ohio Valley through tonight, with a colder air mass slowly pushing into the southeast. At the upper levels, broad troughing still remains in place over the eastern CONUS and western North Atlantic waters, with a shortwave rolling along the northern Gulf coast on the SWrn side of the trough. This pattern is leading to pretty thick cloud cover for our neighbors to the west, but we will for most of today remain on the subsidence/sinking side of the trough, maintaining mostly clear skies during the daylight hours and getting that increase in cloud coverage this evening/tonight. This afternoon will be breezy and cool, with northwest winds around 10 to 15 mph and highs in the upper 60s-low 70s. Breezy winds will continue into the overnight hours and lows will be in the low-mid 40s in SE GA, upper 40s to low 50s in NE FL. .SHORT TERM [Saturday Through Sunday Night]... A strong low level pressure gradient will be in place across the region as a ridge of high pressure over the OH Valley slowly rolls eastward to the coastline, pinning yesterday's front in place out in the Atlantic. Our local pressure gradient will be further enhanced as an inverted coastal trough is forecast to develop off the coast of NE FL on Saturday, nudging inland a bit on Sunday. As a result, expect to have strong north-northeast winds through the weekend around 20 to 25 mph with gusts to 40 mph along the immediate coastline. These winds will lead to a host of coastal hazards this weekend including a wind advisory, high surf heights and a high risk for rip currents at area beaches, gale conditions over our offshore water, small craft advisory conditions for our nearshore waters, and the potential for some heavy rain near the coast. Currently, the majority of models keep the highest totals (2-4") just offshore, but if the inverted coastal trough develops further westward, those higher totals could easily make it to our coastal counties. The strong north-northeast flow could also lead to some nuisance flooding along the Atlantic Coast and ICWWs by Sunday. Temperatures will be cold on Saturday, with highs in the mid 50s in SE GA and upper 50s to mid 60s in NE FL. Lows will be in the low-mid 40s again in SE GA and upper 40s to low 50s again in NE FL. Sunday will begin a warming trend, with highs in the low-mid 60s in SE GA and upper 60s to low 70s in NE FL. Lows Sunday night will dip into the upper 40s in SE GA and low-mid 50s in NE FL. .LONG TERM [Monday Through Friday]... An active pattern will set up across the southern US for next week, though it should say mostly quiet for us. At the beginning of the week, low level ridging to our north moves offshore, nudging our inverted coastal trough further offshore Monday through Tuesday. A shortwave will swing from the central Plains into the Great Lakes region early next week, pushing a cold front eastward is forecast to stall out to our northwest around Wednesday. Another shortwave will swing into the northern-central Gulf coast mid-week, potentially developing a small disturbance near the FL Panhandle. Then around Thursday, yet another shortwave digs into the Southern Plains and develops a system that will move through the lower Mississippi Valley Thursday and possibly moving through our area Thursday night or Friday. Ahead of the front at the end of the week, temperatures will continue a warming trend. Highs will warm back into the 80s across the area by mid-week, with highs around 90 not out of the question for north-central FL. Lows will be mostly in the 50s , with lows warming into the 60s late in the week ahead of the front. .MARINE... An inverted coastal trough will develop tonight and remain in place through the weekend. North-northeast winds of 20-30 knots forecast through the weekend across our coastal waters. A gale warning is in place for offshore waters from St. Augustine northward. Even nearshore waters from St. Augustine northward will likely see gusts to gale force over the weekend. Winds will slacken early next week and nicer boating conditions will at least briefly set up for mid-week. Rip Currents: NE FL- Moderate Today, High Risk This Weekend SE GA- Moderate Today, High Risk This Weekend .FIRE WEATHER... Dry and windy conditions today with min RH values this afternoon around 35-40%. RH will remain above 30% through the period, so no red flag conditions are forecast, but it will be very windy this weekend through Monday. Mixing heights are forecast to be on the low side as an inverted coastal trough brings lower clouds and rain chances to the coastline. These low mixing heights will balance out the high winds, so lower daytime dispersions are forecast for the weekend. && .PRELIMINARY POINT TEMPS/POPS... AMG 43 56 45 63 48 / 10 20 40 30 10 SSI 48 56 50 63 54 / 20 30 60 40 20 JAX 50 58 50 64 54 / 10 40 60 40 10 SGJ 54 60 54 67 56 / 10 40 60 30 20 GNV 49 63 48 68 51 / 0 30 20 20 10 OCF 49 66 50 71 53 / 0 20 20 20 0 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AM...Small Craft Advisory from 2 AM Saturday to 2 AM EDT Sunday for Coastal waters from St. Augustine to Flagler Beach FL out 20 NM-Waters from St. Augustine to Flagler Beach FL from 20 to 60 NM. Small Craft Advisory until 8 AM EDT Saturday for Waters from Altamaha Sound GA to Fernandina Beach FL from 20 to 60 NM- Waters from Fernandina Beach to St. Augustine FL from 20 to 60 NM. Gale Warning from 8 AM Saturday to 2 AM EDT Sunday for Waters from Altamaha Sound GA to Fernandina Beach FL from 20 to 60 NM-Waters from Fernandina Beach to St. Augustine FL from 20 to 60 NM. Small Craft Advisory until 2 AM EDT Sunday for Coastal waters from Altamaha Sound to Fernandina Beach FL out 20 NM- Coastal waters from Fernandina Beach to St. Augustine FL out 20 NM. &&