Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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605 FXUS62 KRAH 071427 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1025 AM EDT Sun Jul 7 2024 .SYNOPSIS... A weak frontal zone extending from the Chesapeake Bay into the Piedmont of the Carolinas will linger and weaken before dissipating by Tuesday. Mid and upper level high pressure will then build across the area before another cold front approaches late in the work week. && .NEAR TERM /TODAY AND TONIGHT/... As of 1025 AM Sunday... * A notable change in the weather pattern and sensible weather for today with more cloudiness and cooler temperatures than the past few weeks. * Scattered to numerous showers and storms are expected although a fair amount of uncertainty in how convection will evolve today. The latest surface analysis shows a cold front extending from the DelMarVa peninsula southwest across southeastern VA into the northwestern Piedmont of NC and into far upstate SC. The air mass across central NC is very moist with PW values of 2.0 to 2.3 inches this morning with the KGSO RAOB observing 2.12 inches. Southeast of the front, dew points range in the lower to mid 70s with an axis of upper 70s extending along the Coastal Plain. Northwest of the front, a light northeast wind is observed in the Triad and in the VA border counties. Further aloft a 594dm mid and upper level anticyclone is centered over the eastern Gulf of Mexico, sandwiched between Beryl and the closed mid/upper level low east of the Carolinas. The mid and upper flow across NC will be rather light today and from the west and southwest. There are a few disturbances in the general flow, most prominently is one moving across eastern NC this morning and perhaps a few others moving into NC from the southwest late this afternoon and this evening. Satellite imagery and surface observations note a good deal of cloudiness across central NC this morning with areas of MVFR/IFR ceilings. With heating, expect some additional breaks in the overcast to develop which will subsequently be followed by stratocumulus and cumulus cloud growth, all of this will result in partly to mostly cloudy skies this afternoon and evening. Particularly challenging today will be the evolution of convection, especially where it will develop and how it evolves. The frontal zone should serve as a natural focus for storm initiation as will a myriad of boundaries across the area including differential heating areas from breaks of sunshine and gradients of different rainfall amounts from yesterday. Convection allowing models provide vastly different solutions which is not surprising given the weak forcing and numerous mesoscale features present. Expect convection to gradually ramp up over the next handful of hours, especially after 1 and 2pm with coverage and intensity peaking between 3 and 6pm and then a gradual decline into the mid and late evening. With a couple of upstream disturbances posed to move near the area tonight, wouldn`t be surprised to see a rogue shower or storm overnight. The main weather hazard today will be slow moving convection in a moist and weakly to moderately unstable environment will be produce some locally heavy rain. Highs today will be tempered by cloudiness and a slightly cooler air mass and generally range in the upper 80s to lower 90s, coolest in the Triad behind the front and warmest across the southeast, ahead of the front and in a warmer atmosphere that did not experience much rain. It will remain warm and muggy tonight with lows in the lower to mid 70s. -Blaes && .SHORT TERM /MONDAY AND MONDAY NIGHT/... As of 330 AM Sunday... Our overall pattern remains much the same, although there are signs that convection coverage may be a bit lower than Sat and today. The frontal zone to our NW will have largely dissipated or morphed into a very weak lee trough, keeping high surface dewpoints and near to above normal temps over the area. Models generally agree in taking the mid-upper low off the Carolinas slowly SSW toward the N Bahamas Mon/Mon night with rising mid level heights over GA/SC/NC, while the high PW axis sitting across central NC decreases about a quarter to a third of an inch. SBCAPE is again expected to peak in moderate territory but with the higher values shunted to our NW. The mid- upper level flow remains quite weak, yielding poor deep layer shear, hindering storm organization once again. Will have pops just slightly under today, peaking at good chance to likely in the afternoon and decreasing in the evening. Once again expect highs in the upper 80s to mid 90s, followed by lows in the 70s. -GIH && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 255 AM Sunday... Tuesday and Wednesday: Beryl is forecast to become ingested within a trough digging into the central/southern Plains Tues and lift into the Mid-MS Valley Wed evening with a transition into an asymmetric cold core cyclone. Closer to home, a continued hot/humid airmass will be in place as central NC is situated within a weakness in the mid-level flow with little synoptic forcing for ascent. This will favor near climo rain/storm chances with pulse, classic summer-type, storm mode. Storm depth/strength may be less than previous days with less instability (500-1500 J/kg SBCAPE) and an upper level anticyclone centered over central NC. Well above normal deep layer moisture and slow storm motions will still pose an isolated risk for flash flooding, mainly in urban and poor drainage locations Tue and Wed. Temperatures will remain hot/humid and average 5-10 degrees above normal. Highs with range from the low/mid 90s with lows in the mid/upper 70s. With heat indices still expected to reach 100-105 and with little recovery overnight, anyone without effective cooling and/or adequate hydration may experience heat related illnesses. Wed night through Friday: The extratropical cyclone associated with Beryl merging with the synoptic trough is forecast to lift through the Mid-MS Valley through the Ohio Valley and towards the Great Lakes region by Wed night into early Thurs morning. Ensemble guidance suggests a unseasonably deep cyclone should evolve (40-60% of members indicating < 1010mb and 20% < 1005mb) by early Thurs with a low-level convergence axis and surface cold front should push into the central Appalachians, and perhaps the Piedmont of central NC into the mid week, which will provide a focus for showers/storms. This should favor rain/storm chances continuing through Wed night and above normal precipitation chances heading into late week. There remains some important along-track inconsistencies on how quickly this area of low pressure shifts northeast, so confidence on timing and eastward extent of the pressure trough and/or effective cold front is lower than normal during this time. Mostly cloudy conditions and above normal chances for rain will temper highs towards below normal by late week, but overnight lows will likely remain around 5 degrees above normal (low/mid 70s). && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... As of 620 AM Sunday... The abundant low clouds that were previously expected to develop early this morning have not panned out, in large part due to the lingering considerable mid and high level cloudiness leftover from last night`s storms, and the persistent isolated showers that have come and gone across the area overnight. Nevertheless, a few low clouds are noted around the area, and there remains a risk of an hour or two of MVFR vsbys in fog along with mostly scattered IFR- level clouds through mid morning, along with an isolated shower or two. As cloud bases rise slowly this morning, VFR conditions should return by 14z areawide, but redevelopment of scattered to numerous showers and storms is expected by 16z-19z starting first in the W Piedmont before quickly expanding across all of central NC, lasting through the afternoon and evening, and aviation interests can expect a risk of storms, with periods of sub-VFR cigs/vsbys and gusty/erratic winds, across all terminals during this time, although coverage should begin to decrease toward 04z. There is a high chance of IFR cigs and MVFR vsbys in fog developing areawide shortly after 06z, forming first at INT/GSO then expanding E. Outside of any storms today/tonight, surface winds will be light and variable, mainly from the SW at RDU/FAY/RWI. Looking beyond 12z Mon, the daybreak sub-VFR conditions should improve to VFR by 15z. Another round of scattered showers and storms is expected Mon, with coverage slightly lower than today. The general pattern of scattered to numerous showers and storms each afternoon through evening will continue through Thu, with at least some chance of early-morning sub-VFR clouds/fog each day. -GIH && .CLIMATE... Record High Minimum Temperatures: 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... None. && $$ SYNOPSIS...Blaes NEAR TERM...Blaes SHORT TERM...Hartfield LONG TERM...Swiggett AVIATION...Hartfield CLIMATE...RAH