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Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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266 FXUS62 KRAH 201715 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 115 PM EDT Sat Jul 20 2024 .SYNOPSIS... The combination of a weak nearly stationary front sitting over North Carolina and Virginia, a very moist air mass in place, and a series of upper level disturbances tracking southwest to northeast over the region will bring continued unsettled weather through Tuesday. && .NEAR TERM /TODAY THROUGH TONIGHT/... As of 945 AM Saturday... Ongoing forecast looks pretty good. Primary tweak this morning was to nudge rain chances downward for the next few hours across the N, following radar trends. A few convective clusters and attendant MCVs are evident in both radar and satellite imagery over the region this morning, including one just NW of the Triad in NW NC/SW VA (near and north of a quasi-stationary sfc frontal zone), one just ENE of ATL in NE GA, and a third over central AL, with additional budding MCVs- to-be over and just S of the FL Panhandle. It remains deeply moist over the area, as noted by layer WV imagery and 12z soundings, the latter showing PWs near or over 2". A few isolated showers have popped up this morning in our NE and skirting into our extreme NW, but otherwise we`re in a brief relative lull attm with the more organized convection just to our NW and well to our SW. But we should see an uptick in coverage esp across the S and W later this morning through the afternoon as the NE GA activity spreads into the area, coupled with some heating over our area (albeit modest in the NW half due to high cloud cover there) to support at least scattered convection outside of the incoming MCV. Will continue to depict pops trending upward today, first in the S and W but with good chance to likely pops everywhere at some point. The risk of a few strong to severe storms persists, given the uptick in deep layer bulk shear today to 25-35 kts, although the higher shear (mainly NW) may not spatially coincide with the greatest SBCAPE (mainly SE). Lastly, have opted to hold off on any kind of flood watch for now, given that the area most likely to see downpours today was mostly spared from the heaviest rain yesterday. But HREF probabilities of one or two inches or more is indeed highest across our N, so will continue to monitor CAM and radar trends. Highs still expected to range from around 80 N to the mid 80s to around 90 central/SE. -GIH Earlier discussion from 356 AM: The lead MCV which induced stratiform rain over much of central NC early this morning has shifted off to our east. Lingering light rain over northern areas will continue to dissipate through sunrise. Aloft, a strong short-wave will eject through the Mid- Atlantic/northeast through tonight. An associated strong mid-level impulse currently over Alabama/Georgia will ride along the Appalachians inducing convection across our area this afternoon. As the short-wave ejects northeastward, increasing mid-level flow will induce upwards of 25 to 35 kts of shear across the northern half of our CWA. As such, a few organized/stronger storms will be possible this afternoon and evening (primarily over the Piedmont/Coastal Plain). Forecasted hodographs are generally straight and thus any stronger storm that develops would primarily be capable of producing localized damaging wind gusts. The only caveat is that some guidance suggests sfc backing of winds could be possible across the Piedmont/Coastal Plain later today. As such, there is a non-zero chance for a supercell or a two to develop. While tornadoes wouldn`t be expected, any mid-level rotation could overcome poor mid-level lapse rates and promote the potential for isolated hail. Overall though, the main severe weather potential today remains localized damaging wind gusts. Similar to recent days, given the persistent, anomalously moist airmass, as well as the potential for west-east training cells, isolated flash flooding will be possible. Best chances for flash flooding would likely be along the NC/VA border, where due to recent rainfall, 1 hr FFG is only about 1 to 2 inches. HREF rain rate exceedance probabilities peak just north of the border in AKQ`s CWA, but the actual heavier rain rates could easily slip into our northeast instead. Highs will reach the upper 80s to around 90 in the south. Overnight lows in the lower to mid 70s are expected. && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... As of 305 AM Saturday... The front that is lingering over the region appears as if it should spend most of the day south of the forecast area. While all locations still have likely pops in the forecast, did bump up southern counties to categorical being closer to the focus area of the front. Highs should again be close to normal, ranging from 85 to 90. Conditions will remain muggy, although even with high humidity values, temperatures in the 80s should minimize the amount of triple digit heat index coverage. && .LONG TERM /MONDAY THROUGH FRIDAY... As of 305 AM Friday... There is minimal change to the long term forecast. A longwave trough will extend from Quebec south into the Gulf of Mexico, and warm, moist advection will persist across much of the eastern United States. Will continue with likely pops during this time period. In addition, heavy rainfall rates means that isolated flash flooding will continue to be a threat across the entire area despite the area being in a drought. Highs should remain near climatology in the upper 80s and lower 90s. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... As of 115 PM Saturday... Sct-bkn MVFR clouds persist across central NC, although cigs continue to lift, and the current pace of this lift would suggest that all TAF sites will be VFR by 19z. INT/GSO has seen a band of showers with brief IFR conditions pass over during the last couple of hours, and while these particular showers are exiting, there is a chance for additional scattered to numerous showers and storms to develop through mid afternoon. These are most likely to impact INT/GSO/RDU first, between 18z and 22z, before reaching RWI within an hour later as the showers and storms increase in number, and finally reaching FAY after 22z. Isolated wind gusts over 40 mph will be possible in and near any storms, along with erratic speeds and directions and brief sub-VFR cigs/vsbys. FAY will see a trend from storms to mostly scattered showers overnight, while other sites should trend to dry weather from mid evening onward. We should see a redevelopment of sub-VFR conditions, mainly MVFR cigs (except mainly IFR at INT) with patchy MVFR vsbys after 07z tonight, with the highest confidence across the W. Cigs will again be slow to rise Sun, likely not lifting and breaking up to VFR until after 16z. Surface winds will be under 10 kts and mostly from the SW through Sun. Looking beyond 18z Sun, cigs should have lifted to mostly VFR by 18z, however another round of numerous slow-moving showers and storms is expected across all terminals Sun afternoon through Sun night. There will be a high chance for showers and storms each day through Thu, as we stay in a moist and unsettled pattern. The chance for late-night-through-mid-morning sub-VFR clouds and briefly sub- VFR vsbys will also continue through mid week. -GIH && .CLIMATE... Record High Minimum Temperatures: July 20: KGSO: 75/2019 KRDU: 76/2020 July 21: KGSO: 76/2011 KRDU: 78/1932 KFAY: 80/2017 July 22: KRDU: 78/2011 July 23: KRDU: 78/2011 July 24: KRDU: 79/2011 KFAY: 79/1945 July 25: KFAY: 78/2016 July 26: KGSO: 76/2016 KRDU: 77/2010 && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield/Luchetti SHORT TERM...Green LONG TERM...Green AVIATION...Hartfield CLIMATE...RAH