446 FXUS62 KILM 111421 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1021 AM EDT Thu Oct 11 2018 .SYNOPSIS... Tropical Storm Michael will continue to weaken as it moves across the Carolinas today. Showers and isolated thunderstorms with periods of heavy rain, gusty winds and the threat of an isolated tornado will last through early evening. A cold front will push across the area Friday followed by high pressure and Fall like weather this weekend into early next week. && .NEAR TERM /THROUGH TONIGHT/... As of 1020 AM Thursday...Flash Flood Watch canceled for our coastal counties plus Columbus NC and Williamsburg SC. Forecast rainfall amounts are insufficient to create a significant flooding threat. Even inland it appears rainfall rates aren't increasing high enough, and I may be able to trim back this watch in a few more hours. Discussion from 930 AM follows... The core of moderate to heavy rain directly associated with Tropical Storm Michael covers the I-95 corridor, but only scattered showers exist along the coast. I'm tempted to cancel the Flash Flood Watch along the coast early but will hold off a few more hours in case a training band develops. The potential for flash flood is certainly diminishing compared to forecasts issued yesterday or overnight. An additional 2-3 inches of rain is possible along and west of I-95 today, with lesser values east toward the coast. Wind gusts in the 40-50 mph range should spread northward along the coast over the next several hours, perhaps enhanced a bit higher in the Myrtle Beach/Cape Fear area early this afternoon as deeper mixing due to warmer temperatures tap stronger wind speeds 1200-1500 feet AGL. NAM forecast soundings show 50 knot winds dipping as low as 1500 feet up across Wilmington around 18Z/2 PM EDT. Michael will accelerate off to the northeast today and tonight. The heaviest rainfall is expected inland now through early afternoon, with rapidly diminishing rainfall potential late in the day as the atmospheric column dries out behind Michael. I've updated our forecast grids to indicate a more rapid drying trend during the mid to late afternoon hours. This is our last day in a tropical airmass. Highs should range from upper 70s far inland under the rain, to the low-mid 80s along the coast. I've updated tonight's lows downward by a few degrees (upper 50s inland, lower 60s coast) as cold advection develops behind Michael's increasingly non-tropical structure. -TRA Discussion from 300 AM follows... What is now tropical storm Michael is progressing along much as expected. The main band of showers is now moving into southern areas of the CWA and this will continue to move to northeast in time this morning and afternoon. I basically followed the HRRR and NAM progressions which show mostly a morning event. The southern half of the storm is being somewhat eroded by drier air moving in. The speed of the storm also plays a role in the quick hitting storm. SPC has maintained a slight risk for all but the extreme western parts of the area but at least so far tornado warnings have been rather sparse. Overall I made only minimal changes to temperatures as they will be modulated by showers and some possible sunshine later this afternoon. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 300 AM Thursday...Progressive mid-level pattern sets up in the wake of Michael as broad troughing moves over the eastern CONUS for the end of the week. At the surface, high pressure builds in from the northwest through the period, dropping temperatures close to climo. Precipitable water drops to around half an inch on Fri and stays well under an inch Sat allowing the region the chance to dry out and keeping skies mostly clear. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 300 AM Thursday...A progressive shortwave will move across New England early in the long term period with near zonal flow across the Southeast United States. In response, surface high pressure will move quickly off the coast during Sunday. Return flow will begin Monday ahead of a strong cold front. The front could move through Monday night or early Tuesday morning with a chance of showers/tstms. Drier/cooler weather is on tap by next Tuesday/Wednesday. After near normal temperatures this weekend temperatures will become above normal once again Sunday through Monday in the pre-frontal environment. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... As of 12Z... A break in shower activity will soon come to an end as Tropical Storm Michael approaches the area from the SW. Expect MVFR and IFR ceilings associated with tropical showers and storms throughout the afternoon with a higher confidence of IFR at the inland terminals. The storm is moving rather quickly to the NE so expect showers to end and VCSH to prevail by late afternoon. This will bring mainly VFR conditions with MVFR at a couple of locations. Throughout the day, winds will be from the S/SW at around 20-30 knots with gusts up to 40 knots. As the storm moves off to the NE, expect winds to taper off from south to north. Overnight, winds will shift from WSW to N/NW and decrease to around 10 knots. This will bring dry air with clear skies and VFR through the remainder of the forecast period. Extended Outlook...Tropical Storm Michael is expected to impact the area Wednesday night through Friday, bringing periods of heavy rain with IFR ceilings, as well as sustained winds of 30-40 kt with gusts potentially in the 40-50 knot range. && .MARINE... NEAR TERM /THROUGH THURSDAY/... As of 930 AM Thursday...Although the center of Tropical Storm Michael is well inland between Columbia and Charlotte, a secondary maximum of strong winds has developed across the South Carolina coastal waters. This packet of 35-40 knot winds will move northward along the coast today with wind speeds peaking late this morning in the Georgetown vicinity, early afternoon for Myrtle Beach, and during the late afternoon hours in the Cape Fear area. Seas already ranging from 6-8 feet should build by an additional 3-4 feet during this period of strong winds. After the strongest winds begin to subside, wind directions should veer more westerly which will reduce wave heights quickly for all but the Brunswick County NC coastal waters. -TRA Discussion from 300 AM follows... All waters remain in a tropical storm warning which speaks for itself. Probably a good chance of transitioning to a small craft advisory mainly for residual higher seas late in the period as what will then be gradient winds will be just below criteria. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 300 AM Thursday...Northerly flow through the period will veer from northwest Fri morning to north on Sat and northeast Sat night. Offshore flow at the start of the period will be 15 to 20 kt, aided by pinched gradient due to departing Michael. Gradient relaxes during Fri with speeds dropping to around 10 kt. Northerly flow continues around 10 kt into Sat night before northeast surge arrives, pushing speeds into the high end of the 10 to 15 kt range. Offshore flow drops seas from 3 to 5 ft at the start of the period to 2 to 3 ft later Fri night. Seas remain 2 to 3 ft into Sat evening before slowly increasing to around 3 ft as the period ends due to increasing northeast flow. LONG TERM /SUNDAY THROUGH MONDAY/... As of 300 AM Thursday...High pressure will quickly move off the Mid-Atlantic coast allowing the flow to veer to a southeasterly direction during Sunday. During Monday southerly flow will increase ahead of a strong cold front that could move through Monday night. Seas will be 3 ft or less but will increase in the wake of the strong front late Monday, especially away from the coast in offshore flow. && .TIDES/COASTAL FLOODING... As of 1000 AM Thursday...We have issued a Coastal Flood Warning for the lower Cape Fear River to account for southerly trop storm force winds pushing water upriver and combining with high tide. A Coastal Flood Warning also remains in effect for Brunswick County Beaches and immediate coast. Elsewhere, expect minor coastal flooding along the immediate coast, including the remaining beaches from Surf City down to Pawley's Island, mainly during the morning High Tide cycles except ALSO during the Thu evening high tides, when the last of Michael's circulation progresses northeast of the FA. Minor coastal flooding thresholds for Springmaid Pier in SC is 7.5 ft MLLW and for Johnny Mercer Pier in NC at 6.0 ft MLLW and the Lower Cape Fear River Gage vcnty of Wilmington at 5.5 ft MLLW. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...Tropical Storm Warning for SCZ017-023-024-032-033-039-054>056- 058-059. Flash Flood Watch until 7 PM EDT this evening for SCZ017-023- 024-032-033. Beach Hazards Statement until 8 PM EDT this evening for SCZ054- 056. High Surf Advisory until 4 AM EDT Friday for SCZ054-056. High Rip Current Risk through Friday afternoon for SCZ054-056. Coastal Flood Advisory until 2 AM EDT Friday for SCZ054-056. NC...Tropical Storm Warning for NCZ087-096-099-105>110. Flash Flood Watch until 7 PM EDT this evening for NCZ087-096. Coastal Flood Warning until 1 PM EDT this afternoon for NCZ110. Beach Hazards Statement until 8 PM EDT this evening for NCZ106- 108-110. High Surf Advisory until 4 AM EDT Friday for NCZ106-108-110. High Rip Current Risk through Friday afternoon for NCZ106-108- 110. Coastal Flood Advisory until 2 AM EDT Friday for NCZ106-108. Coastal Flood Warning until 2 PM EDT this afternoon for NCZ107- 109. MARINE...Tropical Storm Warning for AMZ250-252-254-256. && $$ SYNOPSIS... NEAR TERM...TRA/SHK SHORT TERM...III LONG TERM...SRP AVIATION...21 MARINE... TIDES/COASTAL FLOODING...