Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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046 FXUS62 KRAH 061830 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 230 PM EDT Sat Jul 6 2024 .SYNOPSIS... A subtropical ridge will continue to extend across the eastern Gulf of Mexico and Florida into early next week. A cold front will slowly move southeast into Virginia and the Carolinas over the weekend and then dissipate. && .NEAR TERM /THROUGH TONIGHT/... As of 1110 AM Saturday... * Continued dangerously hot this afternoon with record high temperatures and major to extreme heat risk * More numerous thunderstorms than previous days * Increased concern that slow moving storms with torrential rain will pose a flash flood risk across the southern Piedmont, Sandhills and perhaps the Triangle. The latest surface analysis shows a complex surface pattern with a Piedmont surface trough extending from VA south across the Carolinas. The trough across central NC appears to be enhanced by remnant outflows from convection last night. A light northwest wind is noted in much of the Triad and south central VA with dew points in the lower 70s. A more southwesterly flow is noted further east in the Triangle and Coastal Plain with dewpoints in the lower to mid 60s. Further aloft, the mid-level ridge along the Southeast coast will persist today and strengthened a bit from yesterday. The flow on the back side of the ridge has accordingly strengthened a touch from previous day and the flow has become more southwesterly. The regional radar is quiet this morning, but several disturbances enhanced by convection across MS/AL/GA last night will track northeast this across central NC. These mid and upper level features will track across the surface trough and interact with a persistently warm, moist and moderately unstable air mass across the region. In addition, PW values will increase further today (note PW values this morning were 1.95 at KGSO and 2.28 at KMHX) and range around 125 to 150% of normal toward evening. Already seeing a field of cumulus develop across south-central NC. These clouds will build during the late morning with widely scattered storms firing during the early afternoon across the southern Piedmont and Sandhills then expanding northeast into the Piedmont and becoming more numerous in the broad surface troughing during the mid afternoon. Scattered convection is possible across all of central NC later this afternoon and evening but the greatest chances and coverage will be near the surface trough. Concerned that the flow parallel to the trough and the disturbances moving across the area will lead to multiple clusters of storms moving across the same areas. High PWs of 2.0-2.3" and slow-moving/backbuilding nature of cells may result in isolated to scattered instances of flash flooding. The greatest threat area will be in a triangle from Wadesboro northeast to Raleigh and south to Fayetteville. The convection will likely linger longer than previous night but begin a general weakening trend during the late evening with lingering showers/isolated storms and patches of light rain continuing overnight. Temperatures today are again likely to reach the upper 90s to around 100 with a few localized spots climbing into the lower 100s. With dew points in the lower to mid 70s heat index values will range from around 100 in the Triad, to 105 to around 115 elsewhere. It will remain warm and muggy tonight, with lows in the mid 70s to around 80. -Blaes && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... As of 230 PM Saturday... * Showers and storms expected again on Sunday * Still hot and humid but heat indices will be a bit lower Sunday`s weather will mirror today`s (Saturday) with a similar airmass in place featuring 2.25 to 2.5 in PW`s in place, weak steering flow, and MLCAPEs around 1000-1500 J/KG. In response to today`s convection, a weak surface trough will be deposited across the area and should serve to trigger another round of showers and storms across the area. Meanwhile upstream convection across portions of AL, SC, and GA and their remnant MCVs could serve to focus additional convection across the area during the day tomorrow. The 12Z HREF is suggesting storms could get going early in the day (15-16Z) especially across the western Piedmont before blossoming and slowly expanding eastward. As is the case today, storm motions will likely be slow and convection is likely to be dominated by pulse-type clusters producing periods of heavy rain and isolated sub- severe wind gusts. Hard to pin down any specific area for heaviest rainfall potential but much (if not all) of central NC shares a similar 50-70 percent chance of precip during the day. Given the broad area and low confidence in pinpointing a specific area, I will hold off on Flood Watches. Showers are likely to linger into early evening before dissipating around midnight. Thicknesses should be a bit lower and with storms potentially developing earlier in the day, cloud cover should also be on the increase. Temps should run about 5 degrees cooler than today with highs only reaching the low to mid 90s. Heat indices should remain at or just below triple digits, with the only exception being portions of the southern Coastal Plain where readings may try and take a brief run toward 100-103 before clouds, convection, and outflows bring temps back down. Lows falling into the low/mid 70s. && .LONG TERM /MONDAY THROUGH SATURDAY/... As of 230 PM Saturday... * Typical summer pattern expected with hot/humid conditions * Daily diurnal thunderstorm chances, with greatest rain chances late in the week The mid level pattern for much of next week will feature broad southwesterly flow as the NC becomes positioned between longwave troughing over the Great Lakes and an offshore ridge. It`s worth pointing out that there will also be an upper low that lingers off the NC coast for a period of time this week, but nearly all guidance suggests it will be drawn southward away from our area and should not be a player in our weather across central NC. Embedded within the southwesterly flow aloft will be a series of weak perturbations, all of which are difficult to track and time their arrival into NC, but will ultimately promote daily afternoon/evening shower and thunderstorm chances with areas across the Sandhills and western Piedmont favored any given day. PW`s next will generally range from 1.75 - 2.25 inches during this time (90-95th percentile) with little day to day variation while afternoon MLCAPEs should easily climb into the 1000-1500 J/KG range. In short, precip chances next week will closely mirror a typical climatological distribution for early/mid July. An influx of additional moisture aloft late in the week should support somewhat higher than normal precip chances and PoPs have been trended upward slightly. Hot/humid conditions will once again be the theme next week, although values should be a bit lower than what has been observed recently. Afternoon highs should reach the low to mid 90s, with the highest values of the week possible Tuesday into Wednesday. The arrival of additional moisture (and presumably cloud cover) should hold temps back a bit (upper 80s to lower 90s) to close out the week although heat indices could still approach the triple digits given the humid airmass. Mild overnight lows in the low to mid 70s will also be common. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... As of 200 PM Saturday... Widely scattered showers and thunderstorm will develop across central NC this afternoon. Initially convection will be focused across the Southern Piedmont and Sandhills near the KFAY terminal and then expand across much of the area. Scattered convection will continue through the afternoon and into the early evening before waning during the mid and late evening hours. Convection will be most widespread near the KFAY terminal from 20 to 02Z with the least coverage at the KINT/KGSO terminals. Lingering showers or stratiform light rain is possible into the overnight. Outside of thunderstorms, VFR conditions are generally expected, with localized MVFR to VFR restrictions in storms along with areas of MVFR visibilities and IFR clouds are possible late tonight to around daybreak Sunday, especially across the western Piedmont and across the southern tier. VFR conditions should return by mid morning Sunday. Generally light southwest to westerly winds at less than 8kts are expected through the period although much stronger gusts, perhaps in excess of 35 kts are possible in thunderstorms. Outlook: A rather typical summer pattern of scattered afternoon and evening showers and storms along with some late night and early morning stratus and fog are expected through the period with the coverage of storms and restrictions expected to uptick on Wednesday into Thursday. -Blaes && .CLIMATE... Record High Temperatures: July 6: KRDU: 102/2022 KFAY: 99/1990 Record High Minimum Temperatures: July 6: KGSO: 76/1999 KRDU: 79/1900 KFAY: 76/2017 July 7: KGSO: 73/2019 KRDU: 77/1900 KFAY: 78/2017 July 8: KGSO: 76/2010 KRDU: 78/1986 KFAY: 79/2012 July 9: KGSO: 76/1987 KRDU: 74/2014 && .RAH WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 8 PM EDT this evening for NCZ007>009-023>025-039-040-073>076-083-084. Excessive Heat Warning until 8 PM EDT this evening for NCZ010-011-026>028-041>043-077-078-085-086- 088-089. && $$ SYNOPSIS...Blaes NEAR TERM...Blaes SHORT TERM...Leins LONG TERM...Leins AVIATION...Blaes CLIMATE...RAH