Area Forecast Discussion
Issued by NWS Wilmington, NC

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060 FXUS62 KILM 191447 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 947 AM EST Mon Feb 19 2018 .SYNOPSIS...
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A warm front should move onshore today, but may take until tonight through move fully across the area. Bermuda High pressure building in from the east will bring temperatures well above normal this week with possible record warmth Wednesday and Thursday. A cold front will likely stall to our north on Friday. The Bermuda High will again expand over the region for the weekend. A cold front will approach from the northwest Sunday night.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 945 AM Monday...Although all land stations still have northeasterly winds currently, the warm front isn`t too far from the coast given southeast winds reported as close as 30-35 miles from shore at Frying Pan Shoals buoy and CORMP buoy 41037. As you might imagine, models still show a variety of differing solutions with how quickly the front jumps onshore and how far inland and northward it progresses during the day. The 06Z GFS represents the extreme aggressive case for the warm front`s movement, whipping the boundary through virtually the entire area this afternoon. The 06Z NAM and latest several runs of the HRRR represent the other extreme with a stubborn, dense and cold airmass inland resisting the front`s movement until late tonight. The truth probably lies closer, but not entirely, toward the slower progression of the front. I`ve tightened the forecast temperature gradient across the area this afternoon, adding a degree in spots near the coast and subtracting a couple of degrees across Bennettsville and the northern halves of Darlington and Robeson counties. This yields highs in the mid 60s across Darlington, Bennettsville and northern Robeson county, and 70-75 degrees for most locations east of I-95. The beaches should have highs stuck in the 60s given onshore winds crossing cold water. Dewpoints climbing into the 60s near the coast this afternoon may develop some sea fog, particularly near the Grand Strand where water temperatures are coldest. CCU and NDBC pier observations show water temps of 53-55 degrees along the beaches. Discussion from 300 AM follows... High pressure extends down into the Carolinas from the center just off the Mid Atlantic coast while a coastal trough/warm front remains aligned just off the Carolinas coast. Some patchy drizzle, light rain and fog was over inland areas where weak isentropic lift exists while some light showers were breaking out along coastal trough just off the Cape Fear coast. Overall, shallow moisture with low stratus and patchy fog was holding on with a well defined near surface based inversion present. This coastal warm front will push inland and north through this afternoon with winds shifting around to the southeast to south. All guidance is showing some breaks in the clouds expected through this afternoon as inversion breaks. Warm and moist air will follow as a southerly return flow sets up and ridge builds aloft. Temps will rise quite rapidly through the 60s but a fairly sharp gradient will exist as you move inland before the warm front moves through. A fairly wide spread in guidance exists with the NAM slower in pushing warm front through and holding on to temps closer to 60 for highs in the I-95 corridor, while the GFS has temps reaching 70. For now, have forecast max temps just above 70 east of I-95 while places along and west reaching into the mid 60s. Expect some spotty showers associated with the coastal trough/warm front and have included mainly iso shwrs with best chc along the coast and offshore. Not including much in terms of measurable pcp. Dewpoint temps will follow suit into this evening and expect widespread fog and stratus to develop heading into this evening and overnight. Have included patchy to areas of fog into tonight. This warm and moist airmass will support overnight lows closer to 60 in most places with some mid 50s further inland.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 300 AM Monday...Unseasonably warm temperatures are expected in the wake of a warm front as a strong Western Atlantic Ridge builds across the waters. Temperatures at 850 mb are forecast to be 12-15C through the period. Subsidence and only very shallow moisture should prevent any showers from developing. However, model soundings continue to portray a favorable profile for at least patchy late night and early morning fog/stratus. Also, with dewpoints in the lower to mid 60s through the period, any sea fog that does develop could periodically impact some of the beaches at any point in the day or night. Highs will be well up in the 70s Tue and a couple 80 degree readings are possible well inland. Highs on Wed will be similar if not a degree or two higher. The seabreeze circulation should be strengthening each afternoon and thus there should be a sharp temp gradient near the coast with high temps at the beaches stymied near or just above 70 degrees each afternoon. Lows each night will be commonly in the lower 60s. Record highs could be challenged on Wed... 02/20 City High Temperature Forecast/Daily Record High Wilmington 76/81 in 1991 Florence 79/83 in 2014 N Myrtle Beach 72/77 in 1949 02/21 City High Temperature Forecast/Daily Record High Wilmington 77/78 in 2014 Florence 82/81 in 1997 N Myrtle Beach 72/76 in 1953 && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 300 PM Sunday...Main theme for the extended will be strong surface and mid-level ridging sitting off the coast. Strong mid-level subsidence and deep southerly flow will contribute to an extended period of temperatures well above climo. While there is high confidence in a warm and mostly dry period, there area a few times within the forecast with much lower confidence. The first concerns a backdoor cold front Thu night into Fri. Previous solutions had this feature moving into the area late Thu night and lingering for much of Fri before returning north as a warm front. However, recent guidance has shifted away from this scenario, the both the GFS and ECMWF being quicker to move the 1040 high across the Great Lakes and into the Northeast. Given the propensity for ridging to hold on longer than the guidance expects, am leaning in favor of a warmer, drier solution Thu night and Fri. Another area of uncertainty concerns potential cold front late in the period. GFS/ECMWF currently bring this feature into the area later Sun, but not confident it will arrive that early, which would contribute to warmer temps Sun night. Temperatures, as previously mentioned, will be significantly above normal for much if not all of the period. Medium range guidance continues to depict heights at levels not seen before during the last week of Feb. At the same time 850 temps will flirt with 15C. Away from the coast highs will run in the upper 70s to lower 80s through the period with the possible exception of Fri. Closer to the coast, the combination of water temps in the mid 50s and an onshore flow will keep highs much cooler. The large temperature gradient will also create rather windy conditions on the cool side of what should be a strong sea breeze. Lows will range from the upper 50s to mid 60s through the period. Average daily temperatures could run 20-25 degrees above normal each day. Another way of putting it would be that the departure from normal next week will be equal to what the area experienced during the first week of January 2018, just in the opposite direction. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... As of 12Z...Time height shows solid low level moisture up through 850 mbs for most of the day. Think predominately IFR conditions are a good bet through a portion of the afternoon hours. A warm front will move north through the region and erode the relatively weak wedge in place by this afternoon. Winds will shift to the southeast, possibly south this evening. There is a chance for LIFR conditions, probably after midnight, associated with the warm air advection. Extended Outlook...VFR with periods of MVFR through Fri. Good chance of extended periods of IFR/LIFR in sea fog coastal terminals Tues-Fri. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 945 AM Monday...The warm front should begin the enter the coastal waters shortly, shifting northeasterly winds around the south but with only a modest increase in wind speeds. The bigger issue may come as the moisture content of the atmosphere jumps up behind the front. Nearshore water temperatures in the 53-55 degree range may be cold enough to trigger the development of sea fog beginning this afternoon and lasting perhaps into Tuesday. We`ll continue to monitor this potential and may need to issue a marine Dense Fog Advisory sometime later today. Seas of 2-4 feet should decrease by 0.5 to 1.0 foot through tonight. Discussion from 300 AM follows... A coastal trough/warm front aligned just off the Carolina coast will push inland and north through today. Therefore NE winds will shift around through today to the E-SE and eventually S by late this aftn into early this evening. This will leave a warm and moist southerly flow as Bermuda High pressure begins to dominate through tonight. Winds around 10 to 15 kts early this morning will basically fall and remain around 10 kts or less through the period with seas falling to 2 to 3 ft by this afternoon. The only hazard may be the development of sea fog. As dewpoint temps rise into the lower 60s through today into tonight and cool shelf waters remain in teh mid 50s, the potential will exist for some sea fog. SREF probs for vsby less than 1 mile are close to 80 percent off of the SC coast and spread northward in southerly flow. SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 300 AM Monday...Western Atlantic Ridge will bring benign winds and seas. The wind will be S at 10 kt or less, although afternoon and early eve winds should be in the 10 to 15 kt range near shore due to the seabreeze circulation. Seas will be 2 to 3 ft although some 4 ft seas should begin to mix in Wed night. The risk for some sea fog will remain through the period. Sea surface temps across the near shore waters are in the mid 50s while dewpoints advecting across these waters will be in the lower to mid 60s, so just marginally conducive for sea fog development. Also, the expected wind direction is not particularly favorable for increasing the residence time over the cool shelf waters. At this time, have only included patchy sea fog through the entire forecast period. LONG TERM /THURSDAY THROUGH FRIDAY/... As of 300 PM Sunday...Bermuda High will extend across the waters through the period, maintaining south to southwest flow with speeds 10 kt or less. Weak backdoor cold front will try to drop in from the north early Fri, but it is starting to look like the front will stall before reaching the area. Flow may become a little more easterly during Fri, depending where the front ends up, but speeds would drop closer to 5 kt. Seas will run 2 to 3 ft through the period with occasional 4 ft possible near Frying Pan Shoals later Thu and Thu night.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...RGZ/TRA NEAR TERM...TRA/RGZ SHORT TERM...RJD LONG TERM...III AVIATION...RGZ

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