Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 211925 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 325 PM EDT Wed Sep 21 2016 .SYNOPSIS...
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The remnant circulation of former Tropical Storm Julia will maintain scattered showers through Friday. Drier weather should develop Saturday as high pressure pokes in from the north. A cold front will move through early Sunday, followed by several days of onshore winds and slightly cooler temperatures next week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 300 PM Wednesday...Low pressure over southeast NC will drift slowly SW becoming more elongated along the SC coast by this evening with a trough extending northward from center of low. An easterly on shore flow will exist on the front end of low/east side of trough along the coast and continued NE-N flow inland, on back end of low/west side of trough. This pseudo warm front/trough will provide a warmer easterly flow and will allow for some drying and thinning of the clouds. At the same time energy will continue to rotate around this upper low combining with deeper layer moisture inland to produce showers and isolated thunderstorms wrapping around to the S-SE into Northeast SC. Pcp water values show a plume of deeper layer moisture with values over 2 inches running from VA/NC coast around to the SW to S through central NC/SC. Coastal NC will have some drier air wrapping around from the S to SE with pcp water values down closer to 1.7 inches this aftn. Overall, instability will remain marginal due in part to significant cloud cover, so although clouds will blanket most of the area, expect modest QPF amounts of most areas with greatest amounts aligned inland mainly just west of I-95 corridor. If areas break out along the coast, expect some heating and differential heating to produce some further convective development mainly across central portions of forecast area inland from the coast. As this deep low drifts S-SW toward the GA/SC coast through tonight, some deeper layer moisture will wrap back around over the Cape Fear region and should increase shwr activity over the eastern portions of the forecast area overnight as moisture and showers spread from the coastal waters along the coast in a deeper E-SE flow. Expect mainly light to moderate rain but some embedded heavier rain amounts are possible. Overall the cool pool aloft and continued moist flow will produce plenty of clouds and potential for pcp through tonight. Temperatures inland in northerly flow on back side of low will remain in the mid 70s this aftn while temps along the coast will reach over 80 especially where some breaks or thinning in the clouds occurs.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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As of 300 PM Wednesday...The persistent mid to upper low will become more elongated and may drift westward before opening up into a trough along the east coast and moving off shore by Fri night. The center of the low will remain south of the area with trough extending northward maintaining a deeper on shore flow through the period. The trough looks like it will be just along or off shore which will keep a N-NE flow over much of the area but should see more of an E-SE flow at times along the coast and off shore as trough and diurnal shifts take place. Pcp water values will remain up above 1.75 inches through much of the period in a very moist air mass. With such deep layer moisture and a deep low/trough over the region through the period, expect unsettled weather to continue. While POP areal coverage should remain scattered most of this period, there will be bands of showers with more moderate to heavy rain across portions of the area associated with upper level energy rotating around over the region. Drying will finally take place late Fri into early Saturday as trough finally moves off to the east. Skies will begin to clear from west to east leaving partly cloudy skies by Fri night over most places. Max temps will reach near or around 80 during the afternoons overnight lows near 70 Thurs night but slightly lower Fri night as some clearing occurs.
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&& .LONG TERM /SATURDAY THROUGH THURSDAY/...
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As of 300 PM Wednesday...The upper levels will certainly not look anything like summer with a very amplified trough-ridge-trough pattern expected to develop across North America. Models have struggled to form a consensus over the past few days with details, however the new 12z GFS may be on to something with its depiction of an Omega block developing by Tuesday. Due to this blocked pattern, the potential of a strong cold frontal passage late this month is now in jeopardy and we may remain in the tropical/subtropical humidity through the remainder of September. A 500 mb ridge centered across the Mississippi Valley on Saturday will only slowly work east into the Carolinas by Tuesday and Wednesday. A deep upper level low moving across the Canadian Maritime provinces will push a cold front southward along the East Coast, reaching the Carolinas early Sunday. The surface high behind this front won`t dive south, and in fact may only reach coastal New England by late Tuesday or Wednesday. This will create an extended period of onshore winds and the potential for scattered showers as a band of convergence behind the old front could settle across the area, coincident with at least shallow Atlantic moisture.
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&& .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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As of 18Z...A trough of low pressure from KCKI to NE of KILM coupled with an upper level low continues to produce showers and an occasional thunderstorms with mvfr to ifr ceilings. The forecast does not change much with the upper level low slowly shifting to the southwest. Ceilings will continue and they expect to lower again tonight with IFR/LIFR at all sites and slowly lifting to MVFR by late morning. EXTENDED OUTLOOK...Isolated to scattered afternoon and early evening convection possible underneath the cutoff upper low through Friday. MVFR/IFR morning stratus/fog possible each day through Sunday.
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&& .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 300 PM Wednesday...A deep low over the Cape Fear region will drift southwest through tonight. This will result in a weak pressure gradient with winds 10 knots or less through the day. Wind direction will also be somewhat variable, but in general, an onshore flow will continue as the low center drifts southwest. It should kick back to a more northeasterly direction close the coast on the back end of the low and more E-SE farther off shore on the front end of low. Mid- level dry air over the waters is expected to limit storm development today, but should increase overnight in deeper on shore flow. Seas will remain less than 3 ft mixing in with some longer period SE swells arriving tonight. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 300 PM Wednesday...Low pressure will weaken south of the waters with trough aligned up the coast through the period. This will keep an on shore flow through the period and depending on the exact position of the trough, the winds will fluctuate between E-SE to E-NE over the waters...remaining 10 kts or less. Winds will turn more northerly and pick up a bit by Fri night as low finally moves off to the east. Showers and isolated TSTMS will remain in the mix. Seas will basically remain 3 ft or less with a slight, slow and steady rise as a longer period up to 12 second SE swells mix in. LONG TERM /SATURDAY THROUGH MONDAY/... As of 300 PM Wednesday...Julia`s remnants should be long gone from the weather map by Saturday. High pressure dropping southward from the southern portion of Hudson Bay will push a cold front through the Carolinas early Sunday. This front will sink to coastal Georgia Monday with easterly winds developing across the Carolinas. Scattered showers should develop mainly behind the front beginning Sunday night. Wave heights of 2-3 feet are expected south of Cape Fear Saturday into the first half of Sunday, with the potential for 3-4 foot seas near and north of Cape Fear due to residual swells emanating from distant Tropical Storm Karl. By Sunday night modest onshore winds will create the potential of shorter period 2-4 foot waves away throughout the area, continuing into Monday.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...TRA NEAR TERM...RGZ SHORT TERM...RGZ LONG TERM...TRA AVIATION...DRH

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