Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 241229 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 829 AM EDT Sat Mar 24 2018 .SYNOPSIS... Low pressure moving along a front stalled to our south will bring clouds and some light rain over the weekend. Strong High pressure will build in from the northeast through the middle of next week keeping the weather cool before the high shifts offshore on Thursday. && .NEAR TERM /THROUGH TONIGHT/... As of 830 AM Saturday...Freeze warning was cancelled early. Increasing cloud cover has resulted in temperatures quickly rising above freezing. Discussion from 3 AM follows: Northwesterly mid level flow will back as flow flattens in response to weakening trough over New England states. At the surface two areas of high pressure in the east; one over Florida and a much larger and stronger one over Hudson Bay. Initially the boundary between the two will be quite diffuse but it will strengthen during the day today in response to an approaching surface low and mid level clipper-like disturbance. Clouds increase towards daybreak and will be widespread for the remainder of the period. Rainfall will be slower to arrive than previously thought; a common model bias especially with weak warm advection/isentropic upglide. Will be trending down QPF with this event as well since guidance now pushes the elevated baroclinicity to our north even as the surface ridge surges southward. This will keep most of the appreciable rainfall north of the area. Mid level flow appears to open up to a few embedded disturbances tonight and rainfall chances should rise a bit , but by then the northward drift of the main baroclinicity will have the upglide surfaces north of the area where the best QPF will remain. && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... As of 300 AM Saturday...It will certainly not be the nicest March Sunday around this area as a mid-winter like wedge becomes entrenched down the coast. This wedge high pressure will be reinforced by confluence within NW flow aloft, and will only begin to erode during Monday as ridging begins to assert itself from the SW. Before this occurs, Sunday is shaping up to be cold, cloudy, and even drizzly, especially the first half of the day. Forecast soundings suggest a pronounced subsidence inversion between 925mb and 800mb, with moisture trapped within this layer where profiles are fully saturated. Dry air above 700mb within the deep NW flow aloft will prevent significant QPF, and will add light showers and drizzle the first half of Sunday before drying begins slowly during the evening. Although any qpf will be light and drizzle should end by the evening, clouds will take much of the night to erode, and expect very little clearing until Monday. The clouds and drizzle combined with NE winds will keep highs well below late March standards, and in fact am forecasting highs below typical mid- January readings. MOS numbers are likely a bit too warm in this setup, so have forecasted temps below guidance, with highs peaking only in the upper 40s north zones, to low 50s far south. A cool night is expected as well as mins drop into the upper 30s to low 40s, but reduced longwave cooling due to clouds should prevent much of any frost Sunday night. On Monday, the aforementioned mid-level ridge expands to the NE which will help to slowly break down the wedge and dry the column. Although the pressure pattern will only slowly weaken, meaning the wedge will likely remain in place through Monday, its weakening combined with the drying will allow more sunshine and temps to rebound to still cool values, but 5+ degrees warmer than Sunday, mid to upper 50s across the CWA. This will lead to another chilly night Monday night, with temps once again falling into the mid/upr 30s with better radiational cooling. This could produce some frost concerns Monday night, especially in the coldest sheltered valleys which will experience lighter winds than the rest of the CWA. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 300 PM FRIDAY...A cool start to the week as high pressure extends down from the north with a cool northerly flow in place. Any lingering clouds should get pushed south of the area and any pcp should remain to the south and west through Wed. Mid to upper ridge extending up from the GOM should help to maintain a dry forecast through mid week. The ridge will get nudged south and east by Wed allowing a deeper southerly return flow to develop late Wed into Thurs, bringing warmer and moister flow for Thurs and Fri. Should see an increase in clouds but pcp should hold off until the arrival of the next low pressure system which should sweep a cold front across the area on Fri. Increasing warm and unstable airmass on Friday will give way to showers and isolated thunderstorms. Pcp water values will reach up near 1.6 inches as moisture pools ahead of the cold front on Fri. Drier and cooler high pressure will build in behind it heading into Saturday. Highs will start out in the 50s on Monday and gradually warm, reaching into the 70s by Thursday and Friday. && .AVIATION /13Z SATURDAY THROUGH WEDNESDAY/... As of 12Z...A upper-level disturbance and a warm front just to the south of the area will see the VFR conditions deteriorating to MVFR mainly after 03 UTC and then IFR due to low ceilings after 08 UTC. Rain is expected to develop after 03 UTC and and impact all TAF sites after 06 UTC. Extended outlook...Sun afternoon IFR becoming MVFR. VFR Mon- Wed. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 300 AM Saturday...A weak high will build in from the north through about midday keeping wind fairly light and out of the north. A front to our south will strengthen later this afternoon/evening. High pressure will sink south to the lee of the Appalachians while flat waves of low pressure traverse the boundary. Winds will grow stronger on the warm side of the boundary but the local area will have trouble getting in on this stronger wind field. The increase in seas previously forecast for tonight possibly requiring flags has been pushed forward in time and none are currently expected during the near term. SHORT TERM MARINE/SUNDAY THROUGH MONDAY NIGHT/... As of 300 AM Saturday...High pressure wedge will be aligned down the coast just inland from the waters both Sunday and Monday. Although the gradient is expected to be pinched more strongly Sunday, gusty NE winds will produce SCA conditions through the entirety of the short term. NE winds of 20-25 kts will develop quickly Sunday and then persist into Monday before only slowly waning late Monday night to 15-20 kts. Gusts during this time may exceed 30 kts at times as well. These gusty NE winds will produce an amplifying NE 6-8 sec wave reaching 6-8 ft. This will push significant seas up to 5-8 ft by Sunday aftn, with only a very slow deamplification to 4-6 ft expected by Monday night. Despite SCA conditions being nearly certain, latest NWPS runs have scaled back the timing and rapid amplification of seas, due to a slower progression of the wedge and NE surge. This being the case, will hold off for at least one more guidance cycle before issuing any advisories for the waters. LONG TERM /TUESDAY THROUGH WEDNESDAY/... As of 300 PM FRIDAY...Northerly winds to shift around becoming more on shore and variable on Tues and then southerly late Wed into Thurs. Gusty NE winds up to 20 to 25 knots on Mon, will ease on Tues as they begin to slowly veer around to the E. These stronger winds will produce seas up to 6 to 7 ft in the outer waters with SCA conditions on Monday. Seas will subside to 3 to 5 ft through Tues into Wed but will increase late Wed in developing southerly flow. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...MBB SHORT TERM...JDW LONG TERM...RGZ AVIATION...DRH is the U.S. government's official web portal to all federal, state and local government web resources and services.