Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 171932 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 330 PM EDT Sat Mar 17 2018 .SYNOPSIS... An area of low pressure will move southeast along a frontal boundary which stretches across the area tonight. Cooler high pressure will build into the Carolinas behind the low on Sunday. && .NEAR TERM /TONIGHT/... As of 330 PM Saturday... Dew points have been creeping up all day, having edged into the lower 50s across the southern tier this afternoon. The surface frontal boundary stretches from the Central Coastal Plain to the far Northwest Piedmont, setting up a nice corridor along the path the upper short wave will be following tonight. Expect to see convection multiplying by late afternoon then edging southeast along the boundary and into the Northwest Piedmont shortly after sunset. Convective parameters would be alarming if the diurnal timing were more favorable, with very steep mid level lapse rates and a strong shear profile to support at least modest potential for elevated strong storms...perhaps multicellular or supercellular structure, per the day one outlook for a slight risk across the heart of the area. Mesoscale models have been reasonably consistent, timing-wise, in depicting the best convective potential between 700 AM through 300 AM, and have made some fine tuning to the likely PoPs and thunder potential along the favored frontal zone accordingly. Cannot entirely rule out a rouge storm in the southeast, where initial low level instability and updraft helicity will be more favorable. Mins will be mild, low 40s north to upper 40s south, except for the northeast, where earlier (predawn) onset of cold air advection in northerly flow behind the system will allow mins to fall into the upper 30s. && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... As of 330 PM Saturday... Sun will break out during the morning with cool and dry advection underway early Sunday in northeast flow as high pressure scoots across the Ohio Valley and pushes down the Atlantic coast. Highs will benefit from insolation, reaching the upper 50s to lower 60s. The tranquility will be short-lived, however, as the high moves offshore quickly, allowing for southwest return flow ahead of our next system, which will begin to spread increasing cloudiness across the area by late Sunday night, with a chance of light rain in the southwest Piedmont by morning. Lows will be cooler in the northeast Sunday night, mid 30s, while cloudiness and earlier onset of return flow will limit the diurnal fall to the mid 40s in the west. && .LONG TERM /MONDAY THROUGH SATURDAY/... As of 430 AM Saturday... The medium range portion of the forecast continues to look unsettled, with a Miller B surface low configuration system expected late Monday into early Tuesday morning, with rain/showers expected to spread into the area on Monday, with precip chances expected to be maximized on Monday night/Tuesday early morning. This should result in a CAD air mass developing across the area, with potentially a few thunderstorms across far southern/southeastern portions of our area early Tuesday morning. As the coastal low begins to intensify and lift off to the north and east and becomes the dominate low on Tuesday morning chances for showers will begin to decrease. However, given high variability in recent model runs will keep chance pops in the forecast for Tuesday. Additional mid/upper level energy is expected to dive southeastward and into our area for Tuesday night into Wednesday. Model continue to struggle with how this system will evolve, but there remains the potential for a mix of rain/snow across northern/northeastern portions of the area on Wednesday/Wednesday evening. Dry weather is expected to generally return for late week with the mid upper level trough axis expected to shift to the east. Temps during the medium range are generally expected to remain below normal, with temps well below normal in the heart of the CAD (Piedmont) early this week and again on Wednesday with the threat of wintry precip. && .AVIATION /18Z SATURDAY THROUGH WEDNESDAY/... As of 130 PM Saturday... Intial surge of heavier mid cloudiness and patchy light rain has moved east of the area, with a clearing trend spreading east which will continue through around 00Z. Expect cloudiness to increase in from the northwest between 00-03Z as a low pressure area moves east along a stalled frontal zone across the area. This low will lead to a 4-6 hour window for showers (and potentially some stronger thunderstorms capable of producing some hail and damaging wind gusts), from 02Z-07Z in the Triad, and from 02-08Z at the eastern sites. Storms would be moving quickly and will not be extensive, so will not include in the TAFs at this point due to low confidence in the timing and just where they will track. MVFR/IFR ceilings will linger into early morning (12-14Z), with dry northeast flow scattering out the clouds to VFR late in the TAF period. VFR conditions are expected Sunday afternoon as high pressure settles into the area, then another threat of sub-VFR conditions arrives on Monday, with the sub-VFR threat persisting into the middle of next week as a series of disturbances passes overhead. Confidence is not high regarding timing of these disturbances, so aviation interests should check back for the latest thinking. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS/mlm NEAR TERM...mlm SHORT TERM...mlm LONG TERM...BSD AVIATION...mlm is the U.S. government's official web portal to all federal, state and local government web resources and services.