Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 230519 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 119 AM EDT Sun Jul 23 2017 .SYNOPSIS... Hot and humid conditions will continue thru Sunday with heat advisories already in place. Look for some moderation early next week due to a cool front dropping to and stalling across portions of the region. Shower and thunderstorm activity will increase Sun thru Mon time period. A cool front, will approach from the north and push into the area and dissipate during the mid week period of next week. And yet, another cool front will follow and reach the local area late next week. && .NEAR TERM /THROUGH TODAY/... As of 915 PM Saturday...No thunderstorm activity expected for the evening and overnight period. With thunderstorm activity having occurred farther west than Friday, the associated convective debris cloudiness will likely remain west of the ILM CWA tonight. As a result, will indicate mainly clear skies. The sfc pg will remain tightened and will combine with a healthy 20 to 25 kt southwesterly low level jet to keep sfc SW winds active overnight in the 5 to 9 mph speeds inland and around 10 mph closer to the coast. Thus, fog will not be an issue and at this time will hold off with any low level stratus. Min temps will stay somewhat elevated, with mid to upper 70s, highest across the coastal areas due to the influence of warm Atlantic waters where SSTS are running in the low to mid 80s. Previous........................................................ As of 230 PM Saturday...Sprawling mid-level subtropical ridge will continue from the Central Plains to the Carolinas tonight into Sunday along with Bermuda high pressure off the Southeast U.S. coast. These features will combine to maintain the heat/humidity across the forecast area during Sunday. The heat index during Sunday will be above Heat Advisory thresholds once again and a new advisory will need to be issued. Meanwhile, overnight temperatures will continue to be above normal as warm southwest-south flow persists. Regarding POPs, plan to maintain the highest percentages across the far inland zones as isolated to widely scattered convection is possible along the weak trough. Would expect any of these storms to dissipate with the loss of heating this evening. Showers and thunderstorms could form farther east across the area during Sunday with a more active sea breeze, and of course the far inland trough serving as lifting mechanisms. Lastly, tides associated with a new moon will likely allow water levels to slightly surpass minor flood stage at downtown Wilmington. The high tide this evening and Sunday evening would be the highest of the tides. Plan to issue a Coastal Flood Advisory to account for this. && .SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/... As of 300 PM Saturday...This will be a transitional period to more active weather with increased clouds, shwr/tstm activity and relatively cooler, back around normal temps. The broad northern stream trough begins to dig down into the Carolinas between the weakness between two ridges and the large ridge over the central CONUS pushes east behind it. At the same time expect to maintain a rich feed of warm and moist air around Atlantic ridge in the low levels. The Piedmont trough will get pushed east and will provide a focal point for convective activity as well as enhanced upper level support to produce increased chc of convection along sea breeze and localized boundaries. The models also continue to show a piece of energy riding up from the south through Mon. Therefore, expect chance of shwrs/tstms increasing through the period. Models show pcp water values reaching up near 2.5 inches especially Mon aftn into early evening. Although temps will begin to trend downwards, may see some spots still making it just above 105 on Mon aftn in places with breaks of sun, but overall expect temps down closer to 90 with increased potential for clouds and convection. Heat index values will be between 100 and 105 many places. Overnight lows will continue in the mid 70s in a warm and humid air mass. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 300 PM Saturday...The upper air pattern will transition to a cooler pattern for the eastern U.S. next week. The upper ridge over Texas and Oklahoma on Tuesday will retrograde to the Four Corners region by Saturday. A downstream trough will develop along the East Coast, enhanced by a shortwave that almost cuts off across the Carolinas Tuesday and Wednesday, and a pair of progressive shortwaves that move through New England Tuesday and Friday. At the surface, low pressure should take shape across western South Carolina late Tuesday, sinking down to coastal South Carolina by Wednesday night. This will drag a weak cold front down from the north. While yesterday`s ECMWF kept the front across central North Carolina, today`s run is in agreement with the GFS that the front will sink all the way down into the Charleston, SC area. With low- level convergence focused along the front and cooler upper-air conditions with the disturbance aloft, expect thunderstorms to become fairly widespread Tuesday afternoon through Wednesday. There is the potential we`ll see 1-3 inches of rain area-wide. As the upper disturbance kicks offshore Thursday afternoon and drier mid-level air bleeds in from the west, the surface front should dissipate. Friday should be the warmest day in the extended period with highs popping back into the lower 90s and heat indices over 100 degrees again. By Saturday, the GFS and ECMWF are in surprisingly good agreement that a stronger cold front will dive southward and into area, with another enhancement in the potential of thunderstorms. && .AVIATION /05Z SUNDAY THROUGH THURSDAY/...
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As of 06Z...VFR conditions will dominate the period with brief period of MVFR or even IFR possible from afternoon and evening showers and thunderstorms. Both the sea breeze and the Piedmont trough should be more active than in past days but coverage will still be limited. Storm coverage and activity will diminish quickly with the loss of heating as the sun sets. Bermuda High will maintain southerly flow through the valid TAF period. Sea breeze will bring gusts to coastal sites with potential for speeds in excess of 20 kt from the southeast. Speeds tonight will be around 10 kt, preventing any significant fog development. Extended Outlook...Possible MVFR from patchy stratus near sunrise Mon. Brief MVFR/IFR possible in showers and thunderstorms Mon thru Thu.
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&& .MARINE... NEAR TERM /THROUGH SUNDAY/... As of 915 PM Saturday...Raised a Small Craft Exercise Caution for all local waters beginning at 6 am Sunday and ending at 6 am Monday. A tightened sfc pg will exist across the local waters tonight thru Sunday and is due to the local waters sandwiched between the Modest Bermuda High centered offshore from the SE U.S. Coast and the sfc trof of low pressure lying across the Western Carolinas. In addition, a rather healthy nocturnal SW 20 to 25 kt low level jet will exist tonight into Sun morning. As a result, SW winds will run 15 to 20 kt tonight thru Sunday and into Sunday night. Some gusts up to 25 kt will become possible during Sun into Sun night. Significant seas will run 2 to 4 ft initially and build to 3 to 5 ft either late tonight or during Sun morning and likely hold at these heights thru Sun night. Initially tonight, the SE 7 to 9 second period ground swell will dominate the significant seas early on. Wind driven waves at 3 to 5 second periods will eventually become the more dominant factor within the seas spectrum late tonight thru Sun. Previous.................................................... As of 230 PM Saturday...S to SW fetch will continue through the near term period with Bermuda high pressure and inland trough in place. The pressure gradient between these features will enhance the flow, especially each afternoon and evening. Choppy seas are expected each afternoon and evening as well with seas in the 3 to 5 ft range, otherwise 2 to 4 ft late overnight into the morning. SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 300 PM Saturday...Still looks like precautionary headlines may be needed late Sun into early Mon and possibly late Mon again as winds increase to 15 to 20 KT winds and seas reach 3 to 5 ft as gradient tightens between inland trough to the west and high pressure to the east. The afternoon sea breeze will add to the flow and will keep gusty winds and choppy seas near shore Sun eve and Mon afternoon to early evening. LONG TERM /TUESDAY THROUGH THURSDAY/... As of 300 PM Saturday...Bermuda High Pressure will exit the scene on Tuesday as a cold front drops southward from the Mid- Atlantic states. Models are in increasingly good agreement this front will make it into the area late Tuesday night, with 6-12 hours of light northeast winds expected across the coastal waters as this boundary stalls somewhere in the Charleston, SC vicinity. Unfortunately this front will bring increasing thunderstorm chances, some of which may produce heavy rainfall and gusty winds Tuesday afternoon through Wednesday. The front will become increasingly ill-defined on Wednesday, and by Thursday afternoon should wash out as southwesterly winds increase ahead of a stronger front that should affect the area next weekend. && .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...Heat Advisory from 11 AM this morning to 7 PM EDT this evening for SCZ017-023-024-032-033-039-053>056. NC...Heat Advisory from 11 AM this morning to 7 PM EDT this evening for NCZ087-096-099-105>110. MARINE...None.
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&& $$ NEAR TERM...DCH/SRP SHORT TERM...RGZ LONG TERM...TRA AVIATION...III

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