Area Forecast Discussion
Issued by NWS Wilmington, NC
Issued by NWS Wilmington, NC
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-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --498 FXUS62 KILM 040541 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1241 AM EST Mon Nov 4 2024 .SYNOPSIS...-- Changed Discussion --Strong high pressure across New England ridging across the forecast area, will move off the East Coast over the next few days. Seasonable temperatures through Monday will surge above normal Tuesday through Thursday as subtropical air moves onshore. Rain chances could materialize Wednesday into Thursday as a trough moves onshore and tracks inland. High pressure will return Friday and Saturday.-- End Changed Discussion --&& .UPDATE... Mid-level ridge axis nearly overhead tonight with cloud coverage more intense west of this axis than the east. If anything, added additional cloud coverage overnight into Mon given latest Sat imagery trends and high res near term models. Sfc ridge axis to wedge across the FA from the north thru northeast (as the high`s center moves off the New England Coast during Mon. A subtle inverted sfc trof, aka coastal trof, will reside parallel and just offshore from the Carolina Coasts later tonight thru Mon. The pcpn should remain just off the coast and any inland track should remain just south of the FA. Marine winds, basically 15 to 25 kt with g30 kt possible given latest 41013, MBIN7 and JMPN7 observations. Seas to build to 5 to 7 ft with a few 8 footers possible. Easterly waves at 6 to 7 second periods to dominate overnight. May tweak min temps upwards but no categorical changes expected. && .NEAR TERM /THROUGH TODAY/... Visible satellite loops show a visually interesting pattern along the SC coast this afternoon. A convective cloud band along the west wall of the Gulf Stream is feeding mid level moisture westward across the Grand Strand beaches. The isentropic level that this moisture is moving along veers clockwise around a 700 mb high centered near Cape Fear. This is leading to a spiraling pattern of ascending, thin mid level clouds. The 12z GFS identifies this pattern really well on its 310K isentropic chart and shows the ascending portion of this circulation should move westward with time. Beneath the moisture and clouds aloft, the boundary layer remains dry with a northeast breeze occasionally gusting to 20 mph this afternoon. Nocturnal stabilization should reduce the gusts considerably tonight. Forecast lows are mainly a function of cloud cover: mid to upper 50s across South Carolina but 50-55 across our North Carolina counties. The region of shallow mid level lift should drift westward to the western half of South Carolina Monday. Surface high pressure across New England will shift eastward, veering our low level winds more easterly with time. This should lead to boundary layer moisture gradually increasing Monday with dewpoints likely jumping back into the 60s along the coast during the afternoon. Rather than mid level clouds, it appears we`ll have cumulus and stratocumulus developing at the top of the daytime mixed layer. HREF data suggests there`s some potential for showers to push onshore mainly south of Myrtle Beach late in the day as shallow instability develops beneath the mid level cap. I`ve introduced a 20 PoP late in the day across Georgetown County, but remaining dry (<10 percent) elsewhere. Monday`s highs should reach 73-77, coolest along the beaches. && .SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/... At 500 millibar, high pressure centered off the Carolina coast will not move much through Tuesday night. To the west, a deep 500 mb trough will drop over the country`s western half as it cuts off from the main flow. At the surface on Monday night, high pressure will ridge from off the coast of Maine along the lee side of the Appalachians. The ridge orientation will allow for southeast flow on Tuesday as the high`s center shifts well east of the Carolina coast. The precipitable water increases ahead of the 500 millibar trough. These values will rise to 1.5 to 2" over the southern half of South Carolina. This will allow showers along the Northeast South Carolina coast. The lows for this period will range from around 60 to lower 60s. Highs on Tuesday will reach to near 80. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... The 500 millibar trough, previously mentioned, will be over the Intermountain West, slowly cut off, and then lift out to the Great Lakes on Sunday. Over the southeast United States, ridging at 500 millibars will ridge northward. At the surface, a cold front over the Ohio River Valley will slowly shift and move across the Carolinas on Thursday night into Friday. The developing tropical system is expected to stay to the south. The best chance of rain is Wednesday night into Thursday. The rainfall amount is forecast to be 1 to 1.5" over northeast South Carolina, with heavier amounts over Williamsburg and Georgetown Counties. At this time, confidence is still low. Temperatures are expected to warm to the lower 80s on Wednesday, then fall back into the mid-70s by the end of the week. Lows are expected to be low to middle 60s Wednesday night and cool back to the mid-50s by Saturday night. && .AVIATION /06Z MONDAY THROUGH FRIDAY/...-- Changed Discussion --VFR continues with some ceilings in the 7k-9k ft range currently across the area. Slug of moisture responsible for this deck will shift northwest of the area around daybreak, leaving varying amounts of high cloud over the area. A SCT/BKN ceiling will develop midday into afternoon around 5k ft, with potential for scattered showers along the Georgetown coast. Mid-level dry air farther north will keep the few showers that develop confined to the SC coast. Enough moisture around 5k ft lingers into tonight that a SCT to OVC deck is possible for much of the area through midnight. Winds remain northeast for the valid TAF period with potential for occasional gusts 15-20 kt in the afternoon, strongest along the coast. Extended Outlook...Some potential for MVFR ceilings Tuesday morning at SC coastal terminals and Tuesday evening at all coastal terminals. Otherwise VFR expected.-- End Changed Discussion --&& .MARINE... Through Monday... Canadian high pressure moving eastward across New England continues to create breezy winds across the Carolina coastal waters. An ASCAT-B scatterometer pass shortly after 10 AM confirmed the GFS wind analysis with a swath of NE 20-25 knot winds within 80 miles of the coast with easterly winds farther out converging along a Gulf Stream front. The strongest winds of the event, near 25 knots with gusts to 30 knots, are expected to occur now through about 10 PM tonight. Wind speeds should gradually diminish late tonight into Monday, veering a bit more easterly with time. The Frying Pan Shoals buoy is reporting wave heights of 7 feet with a period of only 6 seconds. Rough conditions will likely continue through the night, improving slightly on Monday. Since wind and and waves are forecast to deteriorate again Monday night, the Small Craft Advisory will remain in effect through the period. Monday Night through Friday... High pressure over Maine will shift off the Carolina coast, and this will cause the winds to veer from the east to southeast by Wednesday. A slowly moving cold front will cross the waters Thursday night, and the winds will return to the north as it shifts southward. Wind speeds are not expected to be above 15 knots. Small Craft conditions will be ongoing due to seas of 4 to 6 feet. The Small Craft Advisory is expected to expire on Tuesday evening as the winds shift to the southeast and diminish. && .ILM WATCHES/WARNINGS/ADVISORIES... NC...None. SC...None. MARINE...Small Craft Advisory until 7 PM EST Tuesday for AMZ250-252-254- 256. && $$ SYNOPSIS...ILM UPDATE...DCH NEAR TERM...TRA SHORT TERM...RH LONG TERM...RH AVIATION...III MARINE...TRA/RH