Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 160525 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 125 AM EDT Wed Aug 16 2017 .SYNOPSIS... Summertime heat and humidity will build and should peak through Friday. Although showers and thunderstorms will gradually become fewer in number, heat index values will climb, and heat advisories may be needed Friday. Showers and thunderstorms will increase during the weekend as a cold front approaches from the north. This front will stall and dissipate nearby early next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... As of 730 PM Tuesday...Latest radar loops show a cluster of weak to moderate thunderstorms about to impact the Cape Fear region, a few spot showers elsewhere. Will tweak forecast slightly regarding timing of these features with the next update, otherwise no major changes anticipated. Previous discussion follows: A sea breeze is resulting in isolated showers thus far while a weak trough farther west and northwest has also resulted in some convection as well. HRRR is supportive of widely scattered storms through the afternoon, and into the evening as a weak impulse moves across NC. Plan on carry chance POPs as a result with little if any chances during the early morning hours. The weak trough will be along the coast during Wednesday and with moderate instability and precipitable water values >2.2 inches will maintain chance POPs. Heat/humidity issues will be a concern Wednesday with heat indices close to advisory thresholds each day. Low temperatures tonight will be a category or two above normal, which has been quite common through a bulk of this summer. && .SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY NIGHT/... As of 3 PM Tuesday...Low amplitude mid-level ridge axis will slowly transition eastward from eastern TN Wednesday night, across the Appalachians Thursday, to the near or just off the coast by 12Z Friday. Precipitable water values look to dip just below 2 inches Wednesday night as northwest flow aloft ushers in a bit of modestly drier air behind a decaying frontal boundary, but will return to around 2.25 inches Thursday and Thursday night. Convection should remain scattered in nature under the flat ridge, with sea breeze and Piedmont trough acting as focusing mechanisms. Heat indices on Thursday are expected to reach into a 100-105 range. Low temps each night will dip into a 75-79 range. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 300 PM Tuesday...Concern for the extended involves heat and humidity Fri/Sat, followed by a cold front for the weekend and into early next week. Vertically stacked high pressure offshore will strengthen into Saturday ahead of a shortwave and associated cold front dropping into the OH VLY. This drives very warm air with high humidity into the region, and highs Fri will climb into the 90s, with mid 90s well inland, which combined with the high humidity will create near heat-advisory apparent temperatures. Isolated showers and tstms are possible Friday as well, but ridging aloft combined with lack of significant forcing will keep coverage isolated. On Saturday, the front will drop into the area and then likely stall as the shortwave hangs back, the front becomes flow-parallel, and ridging persists to the east. Convection chances will ramp up significantly Saturday, with still good chances Sunday as the shortwave digs through the Mid- Atlantic and offshore. Temps for the wknd will remain above climo as well. Concern then shifts to Monday, the day of the total solar eclipse. Guidance has backed off on a clean FROPA, and has the front dissipating overhead during Monday. This is much more typical for late August. While this could create more clouds and unsettled conditions for Monday across the area, mid-level flow does become W/NW behind the aforementioned shortwave which brings some drier air into the mid-levels. At this time a fairly typical August day is expected with aftn CU and convection, especially focused along the stalled boundary wherever that may set up. This does not suggest the eclipse will not be visible, but may be temporarily blocked by convection at times. On Tuesday offshore high pressure re-asserts itself, but yet another weak cold front will approach from the NW creating good convection chances with continuing above climo heat and humidity. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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As of 06Z...Most of the earlier convection has moved out of the area. With synoptic conditions similar to last night, expect inland fog to form in short order. The most favored location is Lumberton where lighter wind fields reside and IFR is likely. For Florence 850MB winds are a little stronger and I have employed MVFR conditions. Later today expect isolated to scattered convecton. Extended Outlook...A brief period of MVFR or lower conditions can not be ruled out in isolated to scattered showers and thunderstorms through Fri. The risk for flight restrictions due to showers and thunderstorms will increase on Sat. Low stratus and some fog during the overnight and early morning hours may result in flight restrictions as well each day.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 730 PM Tuesday...Latest obs continue to show the influence of far-distant Hurricane Gert, with a 3 to 4 ft easterly swell with SW winds of only 10 to 15 kts. Forecast in good shape with no changes planned. Previous discussion follows: Swells from Gert will continue tonight but they will gradually weaken. Seas will be 3-4 ft through tonight, primarily in an E swell, and 3 ft or less during Wednesday. S-SW winds today will veer to an offshore direction overnight as a weak trough moves into the vicinity. Light southerly flow will develop again during Wednesday once the sea breeze becomes established. SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 3 PM Tuesday...A decaying front across the waters Wednesday night will result in light but potentially variable winds, along with the possibility of scattered showers and thunderstorms. Latest guidance suggests the boundary may shift just south of the waters Wednesday night, allowing a period of NE winds before it washes out Thursday morning. Wind direction will veer to the SE Thursday afternoon, and SW Thursday night and Friday as a Piedmont trough and Bermuda high reestablish. LONG TERM /FRIDAY THROUGH SUNDAY/... As of 300 PM Tuesday...A cold front approaching from the NW will sandwich the waters with a pinched gradient as high pressure spins offshore. This will drive increasing SW winds, increasing to around 15 kts by mid-Friday and persisting at these speeds into Sunday morning. This front will stall and begin to dissipate inland from the waters on Sunday, causing the gradient to relax and wind speeds to fall to around 10 kts while maintaining a SW direction. Initially seas will be just around 2 ft, but will increase steadily thanks to an amplifying SW wind wave, becoming 3-5 ft by Saturday night. Conditions should remain just below any cautionary statements however. As the winds begin to ease Sunday, seas will follow, with wave heights falling to around 3 ft at the end of the period. && .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...None. NC...None. MARINE...None.
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&& $$ SYNOPSIS...JDW NEAR TERM...REK/SRP SHORT TERM...CRM LONG TERM...JDW AVIATION...SHK

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