Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 201329 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 929 AM EDT Tue Jun 20 2017 .SYNOPSIS...
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Bermuda high pressure will remain centered offshore this week, but will continue to ridge back to the west over the Eastern Carolinas. A cold front dropping southeast will stall just inland from the coast today before dissipating by Wednesday. Tropical moisture will funnel northward from the Gulf of Mexico for much of this week, further enhancing the potential for torrential rainfall, and possibly localized flooding at times.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 930 AM Tuesday...Sunshine currently across the eastern zones is going to aid in a broken line of deepening convection and torrential rainfall into afternoon, as convergence begins to strengthen and tap into deep tropical moisture across the region. Satellite sensors detecting a plume of PWATS values in excess of 2 inches streaming from the Gulf into the eastern Carolinas this morning. Training of convection and relatively weak steering flow will promote localized flooding through the afternoon hours. The flow with likely parallel orientation of the line itself. No significant changes to the forecast, did up POP values along the coastal interior zones to above likely and into a categorical rating. The other focus area will be along the I-95 corridor ahead of an upper trough with increasing support aloft today. As of 300 AM Tuesday...Deep layer moisture will pool ahead of a cold front dropping southeast through the Carolinas today. Pcp water values will reach up above 2 inches as the deep S-SW flow taps into fee of tropical moisture from developing tropical system well south in the Gulf of Mexico. Models are hinting at a wave of low pressure developing along the frontal boundary over the central Carolinas as a shortwave rides through later today as mid to upper trough digs further down into the area. The actual surface front will not make it through the area and should remain just west of forecast area maintaining this deep moist southerly flow. Overall expect convection to continue to flare along and ahead of front as well as localized convection along sea breeze and any outflow boundaries that develop enhanced by upper level support through today into tonight. Will maintain focus on main threat of localized flooding due to heavy rain and possible wet microbursts as low-level winds will not be very strong. Although the surface front does not make it through, the winds aloft will veer slightly as the trough aloft pushes east into central NC into early Wed morning as wave of low pressure moves off to the NE. This will produce some drying and subsidence through the mid layers in a more westerly flow toward the end of the period into early Wed morning. Overall expect pcp to diminish after midnight with some breaks in the clouds. Temps between 75 and 80 this morning will rise a few degrees with plenty of clouds and pcp. Tonight temps should drop a few degrees lower, between 70 and 75 for a low.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 300 AM Tuesday...Remains of a front stalled in the area at the start of the period will gradually dissipate while a stream of tropical moisture spreads north across the region. Still some unresolved differences between the GFS/ECMWF/Canadian with respect to the how juicy the air gets and how long the tropical moisture lingers in the region. The differences do appear to be decreasing as the ECMWF has backed off on how much dry air spills into the region Wed night following the passage of the shortwave trough. On the opposite end the GFS is now suggesting the weak shortwave will indeed spread a bit of drier air into the region late Wed and Wed night. The result will be highest pop earlier Wed with a gradual decreasing trend from northwest to southeast in the afternoon and evening. Mid level ridge starts to expand back west as early as Wed night with a stream of tropical moisture spreading north from the east side of the Gulf of Mexico system. Timing of this moisture will be key in deciding when higher pop returns to the forecast. There will be a decrease in precip chances late Wed or Wed night but if the tropical plume is slow to arrive much of Thu could be on the drier side with only a few isolated showers developing on the sea breeze, given the presence of the 5h ridge. Deeper moisture return, projected to be late Thu or Thu night, may lead to an increase in convection. Timing will be critical as there is a lack of forcing and, if moisture arrives later, instability will also be limited. These factors all keep coverage later Thu and Thu night uncertain and for now have favored the drier solutions. High temperatures will end up below climo Wed due to clouds and convection. Highs climb above climo Thu as subsidence and drier take hold. Low temps both nights will end up well above climo. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 300 PM Monday...Unsettled weather with a chance for showers and thunderstorms is expected through the extended period though chances for showers and thunderstorms will diminish a little Friday and Saturday as upper ridge builds west into the area. Upper troughing will return for Sunday and Monday resulting in increasing chances for showers and thunderstorms again. High temperatures will increase from the mid to upper 80s thursday to the upper 80s to lower 90s for the weekend before moderating slightly to the mid to upper 80s for Monday. Lows should be in the low to mid 70s through the period. && .AVIATION /13Z TUESDAY THROUGH SATURDAY/... As of 12Z...Low stratus, mainly FEW/SCT, this morning may consolidate into a BKN/OVC IFR ceiling through midday before lifting to a MVFR ceiling for the remainder of the day. Deep moisture in the region today is likely to result in widespread showers and thunderstorms as the sea breeze, heating, and a disturbance aloft will all help generate storms. All terminals are likely to be affected at some point, but no terminal will be affected all day. Winds remain south to southwest today but could become gusty and erratic in the vicinity of stronger convection. Storms may persist until well after midnight, especially closer to the coast where widespread IFR ceilings may hold on until close to daybreak. Extended Outlook...The risk for flight restrictions due to thunderstorms will continue through the period. The probability for reduced ceilings and visibility in thunderstorms with heavy rain should be highest tonight through Wed and possibly again on Fri. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 930 AM Tuesday...Seas running 3-4 feet mainly in SE waves every 5-6 seconds. Scattered showers and TSTMS today will create locally higher winds and waves in and near storms and showers. No changes to the marine forecast at this time expect to up seas as high as 4 feet. As of 300 AM Tuesday...Precautionary headlines will come to an end early this morning as SW winds ease up a bit remaining between 10 and 15 kts most waters. This will allow seas up near 3 to 5 ft to subside to 2 to 4 ft through today. Winds will back slightly and spike up a bit in afternoon sea breeze, but overall gradient will relax as cold front stalls west of area. Deep tropical moisture will stream over the waters enhancing shwr/tstm activity through today. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 300 AM Tuesday...Southwest flow will continue around west side of Bermuda High through the period. Speeds will run in the 10 to 15 kt range with diurnal increases to a solid 15 kt and perhaps a bit higher each afternoon and evening. Seas around 3 ft Wed and Wed night increase to 3 to 4 ft Thu and Thu night. LONG TERM /FRIDAY THROUGH SATURDAY/... As of 300 PM Monday...South to southwest winds of 10 to 15 kt are expected through the period with seas of 2 to 4 ft. Winds and seas may run higher in scattered thunderstorms.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...RGZ/8 NEAR TERM...RGZ/8 SHORT TERM...III LONG TERM...RAN AVIATION...III/MRR

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