Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 010215 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 915 PM EST Wed Nov 30 2016 .SYNOPSIS...
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Mild and moist south to southwest winds will continue through tonight as a strong cold front approaches the Carolinas from the west. The front will move off the Carolina Coasts and offshore during Thursday morning, basically around daybreak. Cooler and drier Canadian high pressure will infiltrate the area during Thursday through Sunday. Areas of low pressure will affect the area late Sunday thru the first half of next week with clouds and increasing rain chances.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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As of 830 PM Wednesday...After the line of convection pushed across the Appalachians, a decrease with intensity was noted as well as some pcpn areal coverage. The activity is now pushing across the I-95 corridor and has now stabilized with respect to intensity. Meaning, it`s basically light shra with embedded moderate shra. Occasionally, will see a reflectivity more in the form of a convective cell, but they have become less and less of an occurrence as this pcpn as a whole moves eastward. The activity will become somewhat more diffuse in coverage when it reaches the ILM CWA Coast. This due to question instability and the main dynamics aloft, ie. 300 mb wind jet streak further staying further west and north of the ILM CWA as it moves off to the NE. Thus, the area does not directly experience the RR quadrant of this upper jet along with the associated UVVS. Have made adjustments to the POPs and QPF thru daytime Thu morning in response to this area of pcpn tracking to the east with individual elements accelerating to the northeast. Have indicated 3 hr QPF blocks to better gage the occurrence of pcpn amounts. Very little tweaking of temps and dewpoints needed at this time with expected CFP followed by CAA and drier air basically occurring late this period, but mainly during the short term period following. Previous.................................................... As of 300 PM Wednesday...Strong southwesterly winds aloft continue ahead of a large upper level-low that is still centered over the northern Mississippi River valley of Minnesota and Wisconsin. Water vapor imagery is showing the strong jet rotating up the southeast side of the low with speed nearing 110 knots at 500 mb over the lower Mississippi River valley. Most of the showers that formed on the convergence boundary this morning have shifted off the coast with a scattered showers developing back to the west over Columbus and Bladen counties. The showers are expected to be isolated to scattered through the early evening. The 17 UTC HRRR shows the convective line that is moving across Georgia at this time will approach the western counties around 7 PM, and will weaken as it moves across the county warning area through the night. Also, the 12 UTC NAM, GFS and ECMWF all show this strong line weakening as it moves across the region. The chances for significant precipitation in our area are not looking as good with this model cycle. The models are indicating the chances of precipitation will extend to just after 12 UTC for southeast South Carolina but earlier for the areas to the west. The lows overnight will drop into the middle 50s west of Interstate 95 and lower 60s at the coast.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... As of 300 PM Wednesday...This period will see the remainder of any showers exiting the southeast North Carolina coast with high pressure building in behind the cold front. This high pressure is expected to continue through Friday night. High temperatures are expect to only be in the upper 60s on Thursday and with cold air advection behind the cold front highs on Friday will only be around 60. Low temperatures on Thursday night will fall into the upper 30s well inland to the lower to middle 40s at the immediate coast line. On Friday night temperatures will drop into the middle 30s well inland and 40 to 42 at the beaches. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 300 PM Wednesday...A deep cutoff upper low across the Baja peninsula will eject out into the southern stream flow early next week, bringing rain chances to the Carolinas. However the timing of this remains uncertain owing to extremely large model differences between the slower GFS and faster ECMWF. Forecasters at WPC have access to a great deal of data we don`t at the local NWS level, and noted in their extended discussion that the ECMWF ensembles resemble the GFS operational run and its ensembles much more than they do the ECMWF operational run. For this reason, we favor a GFS-centric forecast for the extended period. Surface high pressure and a low-amplitude upper level ridge should keep Saturday dry. However by Sunday moisture should begin increasing in advance of the big upper system ejecting out of Mexico. While even the fast GFS doesn`t bring the trough to our longitude until Tuesday, increasing flow of Gulf moisture in the mid-levels should bring clouds and perhaps a little light rain to the area Sunday afternoon or Sunday night. Rain chances then develop again on Tuesday when I`ve increased rain chances to 40-50 percent. A northern stream trough which is shown in both the GFS and ECMWF should roll east out of the Rockies during the middle of next week and could begin to spread another risk of rain into the area by late Wednesday. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... As of 00Z...Persistent fog along the coastal terminals has broken up leaving IFR ceilings with low stratus. A cold front will track across the TAF sites from west to east tonight. This should produce a line of showers with gusty SW to W winds. Have not included thunderstorms in TAFs due to timing of frontal passage, but expect rapidly moving showers with some heavier rain and stronger winds possible just ahead of and along the front from 02-06z inland and 05-09z along the coast. Post fropa expect VFR with westerly winds through end of TAF period. Extended outlook...Expect VFR. Expect clouds and pcp back in forecast by end of period with some MVFR/IFR conditions possible by Monday. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 830 PM Wednesday...Winds over the waters have veered slightly from due S to SSW-SW at the moment. Enough cooler SSTS remain nearshore to keep winds aloft from mixing down to the ocean sfc. This is evidenced with Johnny Mercer Pier at 10 to 15 kt wind speeds with latest SSTS at low to mid 60s...and Frying Pan Shoals buoy at 20 to 30 kt wind speeds with latest SSTS in the mid to upper 70s. Thus, will forecast the ILM coastal waters basically in the middle of these 2 extremes. Significant seas will run 4 to 7 ft for the ILM SC Waters and 4 to 8 ft for the ILM NC Waters. The higher seas will occur across locations with the higher SSts and thus hier wind speeds. This includes the local waters off Cape Fear and Cape Romain. Previous................................................. As of 300 PM Wednesday...South winds of around 20 knots are occurring over the waters this afternoon well ahead of cold front that is located just west of Georgia to southern Mississippi. As the front moves closer to the coastal waters the winds will become southwest and increase to 20 to 25 knots with higher gust. Seas are running between 4 and 6 feet from 20 miles offshore to the coast. Seas are expected to increase to 5 to 7 feet overnight. A small craft advisory will continue for all the water through the night. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 300 PM Wednesday...At sunrise the cold front will be approaching the coastal waters and will move across the waters during the morning. As the winds direction shifts behind the cold front they will weaken, and the seas will diminish below small craft conditions south of Little River around 7 AM and 10 AM north of Little River. By Thursday evening, the winds will shift from the west to the northwest by Thursday evening, and remain north to northwest through Friday night. Winds will relax to 10 knots by Friday and seas will settle out around 2 to 3 feet during this time frame. LONG TERM /SATURDAY THROUGH SUNDAY/... As of 300 PM Wednesday...Canadian high pressure over the Mid- Mississippi Valley will build east into the Carolinas early Sunday, weakening slightly as the centers sits across the interior of both states Sunday night. Moderate offshore breezes Saturday should gradually die down Saturday night, but may get re- energized Sunday night as a wave of low pressure begins to take shape along the Georgia coast late.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...Small Craft Advisory until 7 AM EST Thursday for AMZ254-256. Small Craft Advisory until 10 AM EST Thursday for AMZ250-252. && $$ SYNOPSIS...DCH NEAR TERM...DCH/DRH SHORT TERM...DRH LONG TERM...TRA AVIATION...RAN

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