Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 201447 CCA AFDILM Area Forecast Discussion National Weather Service Wilmington NC 652 AM EST Fri Jan 20 2017 .SYNOPSIS... A warm front will lift north across the area today. The front will then remain in close proximity through the weekend. Waves of low pressure will move along this boundary with the last and deepest Sunday night and Monday. This will result in a wet weekend with total rainfall amounts of one to three inches. Thunderstorms will have the potential to produce severe weather Sunday and Sunday night. As the deep low departs, high pressure will build toward the area Tuesday and Wednesday. A weak cold front will stall in the region on Thursday. && .NEAR TERM /THROUGH TONIGHT/... As of 600 AM Friday...The main surge of showers were quickly moving across the I-95 corridor near daybreak. The rain was very light. A front will approach from the S and should sneak into the Forecast area before stalling. A weak wave of developing low pressure on the front will skirt the coast as it moves N of the area today. The front will then have a tendency to sag S tonight as the wave moves NE and well offshore. An upper trough will pivot across the Southeast states around an upper low in the Northern Plains through midday. As the upper level support pulls away, the showers are expected to become increasingly diffuse. A large area of showers across the upstate of South Carolina was moving toward the I-95 corridor as of 07z. Will carry highest pops across the I-95 corridor this morning, up to a likely risk across Marlboro and Darlington counties. The risk for showers will decrease as you move eastward toward the coast. The risk will also be highest this morning, but will remain above threshold in most areas into the afternoon. Rainfall amounts will be light. Clouds today should keep temps rather uniform across the area, lower 70s. However, an onshore flow will keep the beaches in the mid and upper 60s. We do not expect measurable rainfall tonight, although will show POPs beginning to increase to slight chance near daybreak for southern and westernmost areas. Can not rule out some spotty drizzle tonight. Model soundings continue to support low stratus and fog development and have included areas of fog in the grids at this time. Widespread fog may turn dense overnight as dewpoints remain elevated. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 400 AM Friday...A front will be in close proximity through the period. A wave of surface low pressure is expected to move NE along this front coincident with mid-level shortwave energy Sat. Precipitable water values ramp up Sat, especially by/during the afternoon and will show POPs ramping up in kind. This wave moves by and if the timing holds, and this of course is not a certainty, we should experience a lull in the coverage of convection sometime Sat eve. However, our Forecast Area will remain ripe for more significant rainfall as another wave moves NE along the front. A 50 to 60 kt low level jet at 2-3 kft will impinge on the area overnight Sat into Sun morning and precipitable water values again peak near 1.5 inches. This supports another round of categorical POPs. Then perhaps a lull before the vertically stacked area of strong low pressure reaches the area Sun night and Mon. As you can see, the forecast is froth with complexity. However, the bottom line is we are expecting a very wet and stormy weekend with bouts of showers and some thunderstorms. Our current storm total rainfall forecast through Sun night is 1 to 3 inches of rain and this will be enough to cause localized ponding and perhaps some flooding in the most urbanized areas where drainage is poor. The other major concern is whether any of the thunderstorms will produce severe weather. Here the signals are a bit mixed with the strongest low-level jet not quite in sync with the strongest lift nor the better instability and shear. The strongest low- level jet is currently slated to arrive during Sun morning, a diurnal minimum. Still the severe weather potential late in the weekend exists with mixed layer CAPE values on the order of 500 J/kg with significantly higher instability not too far to our S where the warm sector will be deepest. However, as is often the case in the winter season with these powerful systems, there will be very strong shear. The 0-6 km Bulk Shear values reach up to 70-80 kt Sun and Sun night and these are very high. These values heighten the tornado risk. So it still remains to be seen whether there will be sufficient instability in the lowest levels of the atmosphere to produce damaging winds or tornadoes in our area. SPC currently has a good portion of the eastern Carolinas in a slight risk for severe weather Sun and Sun night. We continue to highlight the weekend hazards in the Hazardous Weather Outlook. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 300 AM Friday...A complex storm system will be on the move to the east/northeast Monday with some residual moisture and forcing aloft continued to advertise good chance pops winding down in the evening. In the wake of this system a broad and deliberate pattern change begins to take shape. Brief mid level ridging moves across Tuesday as strong troughing takes shape out west. This feature will deepen and move east with a full cyclonic flow in place by the end of next week. At the surface, weak high pressure Tuesday and Wednesday will give way to a cold front Thursday. A decent southwest flow of moisture with this system warrants at least some mention of pops for Thursday. Colder temperatures arrive for next weekend with the expectation of below freezing readings (overnight lows) returning for the first time in a while. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... As of 12Z...A warm front will sweep north across the region between now and 16Z, veering surface winds from east to southwest. A little light rain is possible inland along with patchy MVFR ceilings as the front moves through. VFR conditions should prevail through tonight, however as low-level moisture continues to increase we expect widespread IFR/LIFR conditions in fog and low ceilings to develop late tonight, mainly after 06Z-08Z. Extended outlook...IFR/LIFR likely continuing Saturday morning. Tempo MVFR or lower ceilings and visibility expected in showers and thunderstorms Saturday afternoon through Sunday night. Thunderstorms will have the potential for strong to severe wind gusts Sunday afternoon and night. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 600 AM Friday...A front, approaching from the S, will move across the waters as a warm front this morning. SE winds will veer to SW with its passage, but speeds will not exceed 10 to 15 kt. Seas of 1 to 2 ft this morning will build to 2 to 3 ft this afternoon. Tonight, the front is expected to sag southward as weak low pressure along the North Carolina coast moves NE and away from the area. A SW or WSW wind should hold across the waters, but wind speeds will be 10 kt or less with seas holding near 2 to 3 ft. There is some concern for sea fog development and reduced visibility late tonight and have included in the gridded forecast at this time and through the day Sat. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 300 AM Friday...Sea fog may result in reduced visibility through a good portion of the day Sat. A front will be in close on Sat and a wave of surface low pressure is expected to move NE along this front. This will bring widespread showers and some thunderstorms across the waters, especially Sat afternoon. Then on Sun, another wave will be moving along this wavering front and then finally the strongest and deepest area of stacked low pressure will make its way across the area beginning Sun night. Waves of widespread showers and some thunderstorms are expected with each of these features. Convection will have the potential to produce at least gale force gusts Sun and Sun night. Small Craft Advisory conditions are expected to get underway Sun morning and then to persist into the early part of the work week. Sustained winds will peak around 25 kt with higher wind gusts expected. Seas will peak in the 6 to 9 ft range. LONG TERM /MONDAY THROUGH TUESDAY/... As of 300 AM Friday...Low pressure will be departing to the northeast leading to a continuation of strong southwest winds at least for a few hours Monday. Expect speeds of 20-25 knots through midday dropping to 15-20 by the evening. A more offshore flow develops Tuesday with similar speeds of 15-20 knots although leaning toward the lower end of the range most of the day. Significant seas will show a similar trend with very high values early in the period (7-10 feet) dropping considerably Tuesday. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...SHK NEAR TERM...RJD SHORT TERM...RJD LONG TERM...SHK AVIATION...TRA

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