Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 121723 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1223 PM EST Tue Dec 12 2017 .SYNOPSIS... Today will be breezy and the warmest day of the week. The passage of a strong cold front later today will usher in Arctic air tonight and through Wednesday night. Temperatures will quickly moderate Thursday and Friday. A cold front may bring some light rain Friday and a brief cool down Saturday before seasonable temperatures return Sunday followed by the risk for showers on Monday. && .NEAR TERM /THROUGH TONIGHT/... As of 1000 AM Tuesday...Strong cold front has just crested the mountains and will race SE today. WAA in a strong pre-frontal regime will lead to rapid temp rises this morning along with increasingly gusty SW winds. However, peak temperatures will likely occur a few hours before typical maximums, as the front races across the area, moving offshore around 2 pm. This will lead to a rapid wind shift to the NW with continued gusts of 20-25 mph, along with cooling through the aftn. So, temperatures will peak mostly in the 59-63 degree range today, before falling through the late aftn rapidly on strong CAA. Post-front stratus is likely, as noted by current visible imagery, and RAP soundings suggesting a 2-4 hr period of saturation around 3-5 kft, and have increased cloud cover late this aftn/eve. After a clearly atypical temperature curve during the daylight hours, tonight`s temperature curve may be fairly typical due to conflicting/offsetting factors. It will be breezy enough for mixing and thus normally a slower, flatter temp curve. This will be offset by the fairly robust CAA behind the front, and mins will fall into the mid and upr 20s most places, with wind chills falling below 20 towards Wednesday morning. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 300 AM Tuesday...The Arctic surge will drop dewpoints into the single numbers and teens on Wed as 850 mb temps drop as low as -11C. It will be sunny and cold with highs in the lower to mid 40s. NW to W winds of 10 to 20 mph will make it feel as if it were below freezing for much of the day. Minimum relative humidity will be as low as 25 to 30 percent Wed afternoon. As one deep trough lifts out Wed, another will begin to dig more modestly across the Great lakes and Midwest and then across the east coast late Wed night and Thu. It now looks like the brunt of the cloud cover will brush us by to the N. However, an impressive wind field will overspread the area with 50-60 kt of wind lowering to around 2 kft. These very strong winds will tend to keep the air near the ground moving and with the brunt of the cold and dry advection having passed, it should not be as cold Wed night. We should see dewpoints recover Wed night with low temps no lower than the upper 20s and lower 30s. The strong winds in the lower levels of the column will lift out Thu and under the influence of SW flow, highs should reach the mid 50s with plenty of sunshine. Light surface winds will return Thu night and we will begin to see clouds increasing from W to E ahead of yet another deep trough and surface cold front. These clouds will cap minimums in the mid and upper 30s with lower 40s at the coast. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 300 PM Monday...The East Coast longwave trough will reload late this week as another strong shortwave moves through the Carolinas on Friday. This upper system should induce low pressure to develop at the surface over North Carolina during the day Friday. Moisture is going to be tough to find given deep layer winds have so much offshore component, virtually eliminating Gulf of Atlantic inflow. In fact the only moisture I can find arrives in the 850-700 mb layer from the northwest -- most likely Pacific moisture that came onshore in British Columbia several days earlier. Dynamics are going to be so strong that I still think there will be some light measurable rainfall around, and I`m including a 30 percent chance of showers in the forecast for Friday. Dry weather will develop for Saturday and Sunday as a weak upper level ridge pokes north from the Caribbean and surface high pressure moves eastward along the Gulf Coast. Model depictions of another shortwave trough arriving on the East Coast Monday vary quite a bit from model to model, reducing confidence about what impacts we may see. PoPs of 30 percent have been introduced into the forecast for Monday along with some increased cloud cover. Temperatures will be on a roller coaster ride through the weekend, likely coolest on Saturday as the upper trough moves overhead and offshore. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... As of 12Z...VFR through 13/18Z. Front should be through KFLO/KLBT at TAF issuance and should move through the coastal terminals around 20Z. Soundings suggest high level cigs decreasing. Time height progs indicate a slug of post frontal moisture around 4k which could give tempo cigs mainly KLBT this afternoon into early evening. Otherwise skies should clear out this evening and overnight. Winds may stay gusty into the early evening. Winds should decrease to WNW-NW 7-10 kt by 06Z. Extended Outlook...VFR. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1000 AM Tuesday...Small Craft Advisory remains in effect for all waters as winds become gusty in the vicinity of a cold front today and tonight. These will be from the southwest ahead of this front through this aftn, quickly becoming NW this evening and tonight. Wind speeds will reach up to 25 kts pre- FROPA, and may be higher than that tonight after the passage. Seas of 4-6 ft with isolated higher faces are likely, with a short period wind wave dominant. Near shore seas will fall quickly tonight as the offshore flow develops. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 300 AM Tuesday...Small Craft Advisory conditions are expected to linger across at least portions of the waters Wed morning with the dry and cold surge slowly waning during Wed. However, a developing deep and strong WSW flow should keep winds elevated through much of the period. Winds will likely be near Small Craft Advisory criteria, 20 to 25 kt, Wed night into Thu with a 50 kt jet at 2 kft. Seas Wed morning will be highest offshore, up to 4 to 6 ft. Seas will subside during Wed before building to 3 to 5 ft Wed night into Thu with perhaps a few 6 ft seas across the outermost northern waters. Diminishing winds late Thu and Thu night will result in subsiding seas. LONG TERM /FRIDAY THROUGH SATURDAY/... As of 300 PM Monday...An active and windy weather pattern will continue Friday as a Canadian cold front slides across the area. Low pressure is expected to develop along the front, helping produce a surge of offshore winds Friday night. The latest GFS model is actually showing gale-force winds Friday afternoon and night, but other model guidance is not that strong, instead keeping winds strong, but below 30 knots. Our forecast will go with this weaker wind forecast for now, implying a period of Small Craft Advisory conditions (W winds 20-25 kt) Friday into Friday night. Winds and seas should improve on Saturday as Canadian high pressure builds in from the west. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...Small Craft Advisory until noon EST Wednesday for AMZ250-252- 254-256. && $$ NEAR TERM...JDW/MBB SHORT TERM...RJD LONG TERM...TRA AVIATION...MRR

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