Area Forecast Discussion
Issued by NWS Wilmington, NC

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428 FXUS62 KILM 280241 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 941 PM EST Mon Feb 27 2017 .SYNOPSIS... A warm front will lift north of the area Tuesday leading to near record high temperatures Wednesday. A strong cold front will bring thunderstorms Wednesday night into Thursday morning, followed by seasonable temperatures late week. Even cooler temperatures are expected by the weekend. && .NEAR TERM /THROUGH TUESDAY/... As of 900 PM Monday...A cluster of thunderstorms have developed off the southern South Carolina coast. Showers and some thunderstorms were more spotty as you move inland across southern South Carolina an southern Georgia. This convection was in association with a warm front. The front is expected to be aligned along the Carolina coast Tue morning and then quickly move N of the area during Tue. The high resolution HRRR model has been accurately portraying convective trends this eve. It shows the thunderstorms passing offshore to our S during the overnight. However, weak isentropic upglide should be enough to produce some showers on the cool side of the boundary. I have increased POPs to the 30-40 percent range. Still do not feel thunder is warranted given the lack of meaningful instability. Where rain does measure, amounts will be a tenth of an inch or less. Dewpoints have been increasing through the day, an indication of the ongoing moistening in the low levels. These higher dewpoints will ensure we will be a good 20 degrees warmer tonight than last night. We are forecasting mainly mid 50s with upper 50s along the immediate coast. The GFS shows sea breeze convection Tue afternoon. Expect a warm day on Tue with highs generally in the middle 70s. && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 300 PM Monday...Active period through mid-week as near record highs give way to a strong cold front and widespread convection Wednesday night. Period begins Tuesday night with high pressure offshore and a warm front well north of the area. Increasing SW winds will drive strong WAA Tuesday night, and mins will likely fall only into the low 60s, mid 60s at the coast. This is more representative of early March highs, and sets the stage for what will be a very warm day on Wednesday. Drying in the mid-levels behind Tuesday`s front will allow sunshine to break through the mid/high level cloudiness which will combine with 850mb temps of 12-14C - near all-time highs for the date according to SPC Sounding Climatology. This suggests highs approaching records Wednesday aftn, with widespread 80+ away from the immediate coast. Forecast for Wednesday, March 1: Wilmington, NC: 81 Record: 83 (1918) Florence, SC: 84 Record: 84 (1997, 1951) N Myrtle Beach, SC: 77 Record: 81 (1955) Wednesday will be very warm, and with deep SW flow, instability will increase as dewpoint values rise into the 60s. This will set the stage for a possible severe weather event Wednesday night as a cold front races across the region. The Storm Prediction Center has our area in a MRGL risk for severe Wednesday night. A strong cold front will be reaching across the area driven by a potent vorticity impulse moving into New England causing height falls locally. Since this front is expected to cross overnight, likely after midnight, instability will be waning, but an HSLC event is possible. While these nocturnal events do not usually create widespread severe, over 50 kts of wind at 1500 ft AGL help to produce bulk shear values over 50 kts, DCAPE of 400-700 J/kg, and 0-1km SRH of 200-300 m2/s2 creates looping hodographs. Additionally, SHERB values reach 0.7 to 0.9 across far NW portions of the CWA, with lower values elsewhere. This supports at least an isolated damaging wind threat even overnight, as well as an isolated tornado threat, but widespread severe is not forecast. However, a weakening squall line will likely move across the area and most places will receive a gusty shower with briefly heavy rainfall. The highest threat for any severe will be west of I-95 Wednesday night. Temps will crash behind the front, but because of the late FROPA, mins will only have time to fall into the mid 50s well inland, around 60 at the coast, still well above normal for the date. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 230 AM Monday...Cold front will be off the coast as the period begins with strong cold advection underway. Showers may linger in the area for the first part of Thu morning, especially along the coast but any activity would be short lived. Canadian high builds in from the northwest Thu into Fri under broad 5h trough aloft. Reinforcing shot of cold air arrives Fri afternoon, along with an increase in northwest winds and a drop in relative humidity. The center of the surface high settles over the area Sat morning, sliding just off the coast into Sun. Pattern aloft transitions from broad troughing to flat flow, which helps push the surface high off the coast Sun. Temperatures near climo Thu and Fri will dip below climo Fri night and Sat. Temperatures will bounce back to climo Sat night as the return flow develops on the backside of the high. Increasing southerly flow Sun combined with westerly flow aloft will push temps several degrees above climo as the period ends. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... As of 00Z...VFR for much of the valid TAF period. However, there is a risk of MVFR ceilings and visibility in showers, mainly between 08z and 15z. A warm front will move across the terminals late tonight and Tue morning. Extended Outlook...VFR. However, there is a risk for reduced ceilings and visibility in showers and thunderstorms, mainly Wed night into Thu morning. && .MARINE... NEAR TERM /THROUGH TUESDAY/... As of 900 PM Monday...A warm front to our S will lift N and into the waters overnight. The front is expected to move N of the waters Tue morning. Given the front will move into the area overnight, wind speeds will decrease slightly, from 10 to 20 kt late this eve to 10 kt or less overnight. While the front is in close proximity, a varied wind direction is likely, but overall, the direction will veer from E and SE ahead of the front to S behind it. Seas will be 2 to 3 ft. SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 300 PM Monday...Cold front will cross the waters late Wednesday night, with SCA conditions possible. Ahead of this boundary, SW winds will increase steadily from 10-15 kts early Tuesday night, to 15-25 kts during Wednesday immediately ahead of FROPA. The frontal passage will be accompanied by a sudden wind shift to the NW with only slow decreasing speeds through the end of the period. Seas of 4-7 ft are expected late Wednesday and Wednesday night, rising from 3-4 ft Tuesday night, and a 5-6 sec southerly wind chop will be the primary wave group. A subtle decrease in amplitude is possible very late Wednesday night as the winds begin to shift offshore. Additionally, sea fog will be possible Tuesday night and especially on Wednesday as high moisture air advects across cooler shelf waters. Have not introduced any sea fog into the forecast attm as there is some concern that Td-T spreads may be slightly too high, and parcel residence times may not be long enough for saturation due to the fast wind speeds. Will mention the possibility here and address in the official forecast as we get closer to the time of potential sea fog. LONG TERM /THURSDAY THROUGH FRIDAY/... As of 230 AM Monday...Strong cold front will be either moving across the waters or just east of the waters as the period begins. Offshore flow will drop from a solid 15 kt in the morning to 10 to 15 kt in the afternoon. Weak offshore flow continues Thu night into Fri before another surge of cold air pushes across the waters Fri afternoon/evening. This surge will push northwest flow to 15 to 20 kt with gusts approaching 25 kt. Seas will trend down, from 3 to 6 ft Thu morning to 1 to 3 ft Fri morning, as offshore flow decreases. Increasing winds later Fri and Fri night will result in a slight bump in seas with dominant wave becoming a short period wind wave. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...RJD SHORT TERM...JDW LONG TERM...III AVIATION...RJD is the U.S. government's official web portal to all federal, state and local government web resources and services.