Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 211119 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 619 AM EST Sat Jan 21 2017 .SYNOPSIS... A warm front just north of the area will drift back south and basically meander across the bi-state region of the carolinas today into Sunday. A more complex and potent storm system will affect the Carolinas Sunday into Monday with potential for severe weather during Sunday afternoon and evening. Total rainfall amounts today through Monday should amount to one to three inches. This storm system will slowly depart through Monday leaving high pressure for Tuesday and Wednesday. The next cold front will move across the area on Thursday. && .NEAR TERM /THROUGH TONIGHT/... As of 940 PM Friday...Low levels of the atm have become saturated across the ILM CWA with areas to widespread dense fog now common across the ILM CWA. The exception are locations along the immediate coast where visibilities have been staying above dense thresholds. A dense fog advisory has been issued to alert motorists. With the south to north upper ridge axis east and off the coast of the Carolinas, Sw flow aloft will access Gulf of Mexico moisture. At the same time, a mid-level s/w trof will move northeast from Louisiana this morning to Norfolk, VA by daybreak Sunday. With a meandering sfc boundary affecting the bi-state region of the Carolinas, a sfc low will develop on this front and race to the northeast like it`s mid-level s/w trof, off Norfolk, VA by sunrise Sunday. This will cause the meandering front to oscillate once again, 1st lifting north today and then dropping back to the south as the low moves off the coast of VA. This basically keeps the FA within a somewhat saturated airmass thru the period and thus the threat for low stratus and fog thruout this time period. The front and mid- level dynamics will produce some pcpn this morning, however, via the HIRESW model, accumulating rainfall will occur from early to mid aftn thru the mid-evening hours. Not much drying there- after, and therefore look for either or both, low stratus and fog to plague the ILM CWA tonight. As for temps, the ILM CWA will see both highs and lows running 10 to 15 degrees above normal. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
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As of 300 PM Friday...This will become a busy period of changing wx conditions due to the progressive flow basically occurring at all levels. All eyes turn toward the potent upper closed low over Louisiana at sunrise Sunday. This closed upper low does intensify as it moves from Louisiana ENE to the Western Carolinas by daybreak Mon. Looking at the GFS, European, NAM and SREF model comparisons...and for the most part they all agree thru 72 hrs with the mid-level closed Low over Virginia by Monday evening. Its the time line there-after is when the models diverge from one another`s solutions. For Sunday thru Sunday night, is the time period when the upper low captures the sfc low. By Sunday evening, an occluded front will extend from the captured low to the Carolinas Coasts. Aloft, the dynamics associated with the upper closed low along with the twisting and turning of the winds from the sfc to aloft will favor a hodograph that signifies tornadic possibilities. Will definitely have the wind shear from both increasing speeds from the sfc thru aloft and also wind shear in terms of wind direction changes as one goes up thru the atmosphere. The amount of instability avbl will be in question in order for this severe wx to materialize. The old saying, high Shear, low Cape maybe just enough input from each for svr thunderstorms to develop with this event. I`ve seen where 60+ kt winds were howling less than 1200 ft AGL, but with no avbl CAPE for thunderstorm activity to develop and tap those low level jet winds in bringing them down to the sfc. The overall time-line SVR Threat will be from Sunday mid to late afternoon across the SW portions of the ILM CWA...moving across and exiting NE of the ILM CWA by mid to late Sunday evening. Will highlight the Severe potential in the Hazardous Weather Outlook. The stacked low will drift across VA and off the VA Cape by Tuesday daybreak. The sfc cold front pushes well east of the FA late Sunday night thru Monday. Enough moisture will wraparound aloft, keeping the FA within cloudiness along with a low POP for either light showers or patchy light rain or drizzle. There just isn`t any cold air avbl for any type of Wintry Pcpn chances to worry about given this type of system and the Winter season we are currently are in. Overall, temps thru this period will start well above normal, ie. 15 degrees above normal. And will end with temps 5 to 10 degrees above normal.
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&& .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 3 AM Saturday...Impressive stacked low will be exiting to the northeast Tuesday morning with weak mid level ridge axis to the west shifting overhead. 5h ridge does expand north slightly Tue into Wed, increasing mid level subsidence, but it shifts off the coast by midday Wed. Under the mid level ridge a weak surface high will build in from the west. The high is a modifying maritime tropic airmass and lacks cold air. As a result temperatures Tue and Wed will remain well above climo. Mid level subsidence and a lack of deep moisture helps keep the region free of precip as well as limiting cloud cover. A cold front, trailing low pressure moving from the eastern Great Lakes to southeast Canada Wed into Thu, moves into the area Thu. Deep southwest flow ahead of the front will help spread Gulf moisture over the region. Precipitable water values approach 1.5 inches just prior to fropa and there should be some potential for isolated showers, especially if a slower solution similar to the latest GFS, verifies. GFS also depicts a weak wave developing along the front prior to the boundary reaching the forecast area. ECMWF is a little faster with the front (in part because it doesn`t develop the surface wave). While temperatures ahead of the front will be well above climo, the passage of the front begins a downward trend in temperatures as another high builds in. Temperatures will be near climo for Fri and then below climo on Sat. The cold air does not arrive in 1 big surge, instead it oozes into the southeast over a period of a couple days. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... As of 06Z...Expect periods of intermittent MVFR/IFR conditions to become widespread IFR/LIFR early this morning as increasing coverage of low cigs, below 5h feet, and areas to widespread fog, occasionally dense, up to the midday hours. During the afternoon hours, given ample available low level moisture, do not anticipate conditions to drastically improve, thus remaining around IFR/LIFR conditions into this evening. Also, patchy to areas of light rain will move across the area from midday thru this afternoon. Calm to variable in direction up to 3 kt, will dominate this morning and into this afternoon. Winds will pick up from the south thru south-southwest at 5 to 9 kt and will continue into the evening hrs. Sea fog will develop by this evening over the adjacent waters, and depending on wind speeds and more-so wind directions, the coastal SC terminals may experience this advection type fog. Extended outlook...MVFR/IFR ceilings and visibility expected early Sunday morning. By midday Sunday into Sunday evening, showers and thunderstorms will overspread the area with IFR conditions at times. There is an increasing potential for strong to severe thunderstorms Sunday aftn and evening. There-after, Monday thru Wednesday, MVFR to mainly VFR conditions expected. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 345 AM Saturday...SCA has been raised for all coastal waters beginning at 6 am Sunday and persisting thru 6 pm Tuesday. A sfc frontal boundary will be meandering across the local waters this period. At first, it will lift northward as a warm front this aftn and then drop back to the south slightly tonight, likely stalling across or just north of the region. The wind directions will become the problem child this period. Wind speeds will see a lull this morning thru this aftn, then pick up to 10 to 20 kt by daybreak Sunday with the meandering front having drifted back to the north for good. Thus the ILM Waters will remain in the warm sector under increasing S to SW winds. Will indicate isolated thunder across the waters, mainly across waters that have SSTS near 60 degrees which for the most part are the offshore waters. Significant seas will be at their lowest today when compared to what they will become during the next 3 days. The seas will begin their rising trend tonight with 3 to 5 footers possibly by daybreak Sunday. Wind driven waves at 5 to 6 second periods, will dominate the significant seas spectrum this period. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 400 AM Saturday... LONG TERM /TUESDAY THROUGH WEDNESDAY/... As of 3 AM Saturday...Strong offshore flow to start the period will gradually subside during Tue as high pressure builds in from the west. Conditions Tue morning will likely require headlines but unsure if SCEC or SCA will be warranted. Gradient gradually relaxes Tue with speeds dropping under 15 kt Tue night as winds veer from northwest to southwest. Surface ridge axis moves overhead Wed morning with speeds around 10 kt. Ridge axis shifts offshore Wed with a steady increase in southwest winds in the afternoon and evening. Solid 15 kt southwest winds Wed afternoon will increase to 15 to 20 kt Wed night. Offshore flow Tue leads to a steady reduction in seas, dropping from near SCA thresholds Tue morning to 1 to 3 ft Tue night. Southwest flow developing and then increasing Wed will start building with values peaking between 3 to 5 ft late Wed and Wed night. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...Dense Fog Advisory until 10 AM EST this morning for SCZ017-023- 024-032-033-039-053-055. NC...Dense Fog Advisory until 10 AM EST this morning for NCZ087-096- 099-105-107-109. MARINE...Small Craft Advisory from 6 AM Sunday to 6 PM EST Tuesday for AMZ250-252-254-256. && $$ SYNOPSIS...DCH NEAR TERM...DCH SHORT TERM...DCH LONG TERM...III AVIATION...DCH MARINE... is the U.S. government's official web portal to all federal, state and local government web resources and services.