Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 150541 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 141 AM EDT Tue May 15 2018 .SYNOPSIS... Low pressure developing off the Florida west coast should push tropical moisture over the Carolinas beginning Tuesday. This will lead to more clouds, increased rain chances, and cooler daytime temperatures. This weather pattern should last into the coming weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 1036 PM Monday...Low level flow picking up a bit with VWP from Shallotte showing 30 kt from the boundary layer to around 4000 feet, S-SSW. This will serve moisture advection off the Atlantic waters well. The mid-level cap will slowly erode as the infusion of tropical moisture deepens, but not entirely, until Tuesday, so expecting isolated showers only, for the overnight period. No significant changes required, with the clouds setting in, not anticipating sharply reduced visibility in fog/mist. As of 752 PM Monday...Based of recent radar trends, and the latest HRRR depictions, have scaled back overnight POP values to the isolated category, ramping up moreso into Tuesday with TSTMS chances coming into play then. No other changes were made as temperatures, winds, and sky elements, look good. We will see shrinking diurnal temperature ranges in the days ahead due to the infusion on tropical moisture. As of 400 PM Monday...Increasing cirrus clouds today the harbinger of change in pattern. Deep layer low over Florida/Gulf of Mexico lifting ever so slowly northward, it`s upper level moisture arriving first at this time. Moisture advection will deepen into the lower levels through the period yielding lowering cloud heights and rain chances that rise from south to north, the rain likely holding off until the latter half of tonight. Much of Tuesday will be unsettled, though the threat for any heavy rainfall will be slated for later periods. Of note will be the tempered warmth Tuesday afternoon after the recent string of June-like temperatures. Both nights on the other hand will be warmer than climatology due to the extensive cloud cover. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... As of 400 PM Monday...Let the rains begin. From 1 end of the spectrum, the recent hot and dry period followed by now, a wet period. The drifting cutoff upper low is progged to directly affect the Eastern Half of the Gulf of Mexico and Florida during this time period and continuing beyond. The main belt of westerlies remains well north of this system with nothing immediate upstream that could kick start this upper low or even absorb it. With counter-clockwise flow, moisture from several sources...Gulf of Mexico, Caribbean Sea and Tropical Atlantic...will combine and get siphoned northward reaching the ILM CWA and deposited across the local region in the form of showers and thunderstorms, with possible heavy rain producers. For the time period, 8 PM Tue thru 8 AM Wed, the QPF will range from one half to 1 inch. The lower end to occur inland and the hier amounts along the coast due to the unabated onshore movement of the pcpn. Have also identified when and where the hier POPs will occur thruout each day. You have the nocturnal engine over the Atlantic waters springing up convection during the pre-dawn hrs each night and moving northward under southerly flow thru the atm column. This pre-dawn activity will move onshore and inland thru the morning hrs and weakening some as it pushes inland. By midday and thru the early evening hrs, the inland locations will be under the gone for convection to develop given any amount of the days insolation. It will not take much to fire up showers/thunderstorms given a loaded atm with PWs approaching 2 inches and any embedded s/w trofs aloft. Have undercut Max temps for Wed, leaning toward the lower NAM and European. And have increased overnight lows by a degree or 3 with no aspects of any rad cooling conditions. Inevitably, the diurnal temperature range will run 10 to possibly 15 degrees at most. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 400 PM Sunday...A significant plume of tropical moisture will prevail across the region for most if not all of the extended forecast period. Guidance is showing a slightly stronger Bermuda ridge building westward for the weekend, and if this occurs could be a limiting factor for convection along the coast. Otherwise good chance to likely pops continue for most of the area through the period. Steady state temperature forecast as well with highs in the lower to middle 80s and warm overnight lows thanks to the moisture struggling to dip below the 70 degree mark. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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As of 06Z...Slowly deteriorating conditions through the valid period as tropical moisture streams northward from a trough of low pressure in the Gulf of Mexico. Initially, this moisture is manifesting as mid and high level cloudiness which will develop into VFR cigs overnight and into morning, with a few showers possible at the coastal terminals by daybreak. Most of this activity will be light so VFR will be prevail, and the best chance for any restrictions overnight will be in some potential TEMPO MVFR stratus inland. During Tuesday, moisture will increase and showers will become more widespread. Timing of any individual shower is difficult as they will be scattered to numerous, so have carried VFR vsbys with -SHRA and VCTS, with TS most likely during the aftn/eve. Restrictions will be best handled with AMD`s as needed during this time. A brief respite is possible during the late aftn/eve and towards the end of this valid period before another increase in moisture and shower activity with possible restrictions moves towards the area late. Winds will be generally S/SW and light overnight, becoming S/SE around 10 kts Tuesday. Extended Outlook...Periods of MVFR or lower cigs/vsbys will be likely through the extended mainly associated with scattered to numerous showers/thunderstorms
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&& .MARINE... NEAR TERM /THROUGH TUESDAY/... As of 1036 PM Monday...Mixed seas comprised of, SE waves 2 feet every 8 seconds will commingle with SSE waves 2-3 feet every 5-6 seconds overnight. Isolated marine showers can be expected after midnight, with a few TSTMS on Tuesday, as tropical moisture increases across the region. As of 400 PM Monday...The area will remain in between a very large west Atlantic high and low pressure developing over Florida and the eastern Gulf of Mexico. This will promote a continued southerly flow in the 10-15 kt range. Seas will remain 2-3ft for the most part except for a few 4 ft waves that will start affecting the outer portions of New Hanover waters due to their far eastward extent. SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 400 PM Monday...Thruout this period, the local waters will reside in the "middle", between the cutoff low meandering across the NE Gulf of Mexico and ridging associated with Bermuda high pressure over the western Atlantic. The sfc pressure pattern and slowly tightening gradient will result in Southerly winds around 15 kt thruout this time period. Significant seas will slowly build to 3 to 5 ft during this time period and as time passes by, the seas initially at 4 to 6 second periods, will increase to a pseudo swell at 6 to 8 second period given the length and time period under this southerly fetch. SCEC conditions likely by the end of this period, with SCA mainly from seas thresholds remains possible at the end of this period. Showers and thunderstorms will become most numerous each day running from late in the pre-dawn hrs of each day and lasting until the mid to late morning daytime hrs. Mariners will see vsbys 1 nm or less during some of these tropical type rains as well as gusts up to 30 kt. LONG TERM /THURSDAY THROUGH SATURDAY/... As of 400 PM Monday...Bermuda High Pressure will be the dominant feature for the marine community for the extended period. This will keep south to southeast winds of 10-15 and sometimes 15-20 knots across the waters through the period. Significant seas will be 2-4 feet and sometimes 3-5 feet with the stronger winds. Small craft conditions could be in play but more likely is an extended period or several intervals of SCEC conditions. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...SHK NEAR TERM...JDW/MBB SHORT TERM...DCH LONG TERM...SHK AVIATION...JDW MARINE...

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