Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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104 FXUS62 KRAH 121810 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 210 PM EDT Sun May 12 2024 .SYNOPSIS... High pressure will build across the Southeast and Mid Atlantic region today, then shift off the Southeast coast tonight through Monday. A storm system will move in from the west Monday night through Wednesday, bringing unsettled weather. Weak high pressure moving in briefly for Thursday will be quickly followed by another storm system arriving Friday. && .NEAR TERM /TONIGHT THROUGH MONDAY/... As of 210 PM Sunday... Continued fair and dry tonight, as weak high pressure builds in from the west, with a deep boundary layer topped by stable/dry mid levels and a light WNW mid level flow. After the high-based clouds dissipate near sunset, skies will be clear through at least this evening, followed by a few high clouds spreading in late, esp over our SW, emanating from TX/W Gulf Coast convective complexes. Lows tonight should be similar to this morning, upper 40s to lower 50s. For Mon, the surface high will shift off the Mid Atlantic coast, resulting in the onset of a light SSE/S return flow late in the day. High and mid clouds will steadily move in from the WSW through the day as remnant MCVs or residual debris clouds from TX/Gulf convection pass over the Carolinas. But it will remain rain-free, with residual dry air in the mid levels (600-700 mb) and a lack of moisture transport through the low levels. With thicknesses expected to rise to near normal and less insolation than we`re seeing today, high temps should be similar, upper 70s to lower 80s. -GIH && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 145 PM Sunday... A closed upper trough over MO Mon night will become an open wave as it tracks eastward Tue and Tue night into the lower OH valley and parts of KY/TN. At the surface, guidance shows a Miller B low pressure tracking from east-central MO into the OH valley during this period. Downstream of the low, a warm front over GA/SC is forecast to lift northward Tue night. While there remain some differences with respect to track/intensity, models show a secondary low tracking NE along the NW Piedmont and along the VA border at this time. Rain chances will overspread the region overnight Mon night and especially Tue morning/afternoon as moisture transport and isentropic ascent maximize over the region. Precipitable water values increase to near record daily maximum values of 1.75 to 2.0 inches. While not a classic setup, there are some indications of a weak in-situ wedge that could set up over the NW Piedmont Tue as the secondary low tracks through. As such, most of the forcing north of the warm front will be isentropically driven but some thunder chances will exist across our southern zones, mainly south/east of US-64/US-1 in closer proximity to some surface based instability. Highs could be tricky in the NW with lots of low clouds/rain around. We lowered highs to the upper 60s in the NW and mid 70s in the far SE, but these may need to be lowered if trends favor a wedge setup. Rain chances appear to lessen Tue evening/overnight into early Wed as a dry slot moves in from the mid-level shortwave. However, lingering low-level saturation should favor drizzle/shower chances over portions of the area, and perhaps some fog. Lows will be in the low to mid 60s. Rainfall totals could range from half an inch to three quarters of an inch in the NW to three quarters of an inch to 1.25 inches in the SE by Wed morning. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 305 AM Sunday... Surface low pressure should be over southern Illinois at the beginning of the extended forecast and precipitation will extend well to the east, with rain increasing in coverage through the day. Models begin to diverge with the surface feature Tuesday night, with the 00Z GFS showing two low centers by Wednesday morning (over KY/TN and DE) while the 00Z ECMWF has one broad center over OH. Regardless of which scenario plays out, think that a bit of a dry slot will develop over the Carolinas Tuesday night and there should be a bit of a lull in shower coverage. The last two runs of the ECMWF are suggesting that the upper trough helping to support the surface low could close off into an upper low over the mid-Atlantic on Wednesday, helping to intensify the surface low as it passes to the north. While some rain could linger Wednesday evening, conditions should then dry out as high pressure settles over Quebec and a ridge extends along the eastern seaboard on Thursday. Meanwhile, the next system will be developing in the Plains, and with models indicating it may move east a little more slowly, have removed all pops from the forecast Thursday night. Had enough confidence to add likely pops across western counties Friday, but the models diverge too much after this to go with anything higher than chance pops through Saturday. Tuesday remains the coolest day in the forecast with widespread highs in the 70s and possibly even upper 60s near the Virginia border, otherwise temperatures should be near climatology, around 80 and 60 degrees. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... As of 135 PM Sunday... VFR conditions are likely, with high confidence, for the next 24 hours across central NC. Dry weather will continue, and after scattered to briefly broken high-base cumulus this afternoon dissipates, fair skies will prevail this evening through Mon, although high clouds will steadily spread in and thicken Mon afternoon. Surface winds will be from the WNW or NW through this afternoon at 10-15 kt gusting to around 20 kt, diminishing to light and variable after 22z. Looking beyond 18z Mon, VFR conditions are expected through Mon evening, although light sprinkles will begin spreading into the western Piedmont during the evening hours. Widespread rain with a high chance of sub-VFR conditions and increasing/shifting winds aloft will overspread the area from SW to NE starting Mon night, lasting through Tue afternoon. Rain should become lighter and more patchy Tue evening/night, but sub-VFR fog and low clouds should linger through Wed morning. A band of showers with brief sub-VFR conditions is expected to swing through Wed afternoon/evening. Areas of sub-VFR clouds are possible early Thu morning, otherwise VFR conditions will dominate Thu. Scattered sub-VFR showers and storms are possible Fri afternoon. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...Kren LONG TERM...Green AVIATION...Hartfield