Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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987 FXUS62 KRAH 151030 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 630 AM EDT Mon Jul 15 2024 .SYNOPSIS... A strong subtropical ridge will remain over the Southeast through early to mid-week. A cold front will approach from the northwest on Wednesday and stall out over the region into the weekend, resulting in unsettled weather to close out the week. && .NEAR TERM /THROUGH TONIGHT/... As of 300 AM Monday... ...Heat Advisory Has Been Expanded to incluce the Southern Piedmont... ...Record Breaking Temperatures... Subtropical ridging atop offshore Bermuda high pressure with a lee troughing along the eastern slopes of the Appalachians will persist through mid week. Models continue to indicate that the heat will build ever so slightly today as h8 temps warm from 22C to 23C and low-level thicknesses increase 1442m to 1447m. This should translate into 1-2 degrees of warming with record breaking high temps expected at 2 of our 3 climate sites(GSO and RDU) as most locations warm into the upper 90s, with some triple digits/lower 100s possible in the typically warmer locations. Meanwhile, the soupy dewpoints will continue to pool across the eastern half of the forecast area, which will exacerbate the effects heat and lead to heat indices of 105 to 109 degrees. Have expanded the Heat Advisory into the southern Piedmont counties, which now encompasses all but 4 of our northern/northwest Piedmont counties. We will see another day of isolated to widely scattered diurnal showers and storms, with the lee trough, seabreeze, and weak perturbations moving off the higher terrain providing the foci. Convection will fizzle out after loss of heating with dry conditions overnight. Muggy lows in the mid to upper 70s, with little to no overnight relief from the heat. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... As of 300 AM Monday... Remaining under the influence of the subtropical ridging aloft and Bermuda high pressure in the lower levels, PWATs increase 2.2-2.3" across the area Tuesday. Rain chances should be up from previous days, more in the climatological ranges(~40%), as models suggested a noted increase in the potential for weak perturbations to move through the region. While the increase in cloud cover and rain chances should temper high temps 2-3 degrees, the higher humidity/dewpoints should offset the slightly cooler temps to yield similar heat indices in the 105-109 range. Thus, additional Heat Advisories will be needed be much of the same areas. Given the moist airmass, convection could linger well into the overnight hours. Balmy overnight lows in the mid to upper 70s. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 345 AM Monday... A classic very wet pattern and heavy rain threat will set up across central NC for the extended period. PW values increase further on Wednesday to 2-2.5 inches as mid-level troughing digs into the Great Lakes and southern Canada, turning the flow aloft over central NC more southwesterly. This will also shunt the western Atlantic ridging farther east and begin to gradually lower heights. At the surface, a strong cold front will stretch from the northern Mid- Atlantic to the southern Appalachians by Wednesday night, as low pressure over southern Canada enhances the lee trough over the Mid- Atlantic. While the best forcing for precipitation will still be to our north and west, shower and storm coverage should still be fairly widespread, highest NW in closest proximity to the front. Temperatures will be kept down a bit from the clouds and precipitation, but it will still be quite warm and humid with little drop in thicknesses. Forecast highs are mostly mid-90s and heat indices around 105 from around the Triangle south and east. Low temperatures Wednesday night won`t provide a lot of relief, only dropping to the mid-to-upper-70s. Thursday and Friday look to have the best chance for heavy rain in the period as the cold front reaches central NC and slows down. Deep southwesterly flow aloft ahead of broad mid-level troughing that digs from the Northeast US into the lower MS Valley will continue to bring in above-normal PW values. So there will be plenty of moisture for this front to tap, along with moderate instability of around 500- 1500 J/kg. The vast majority of GEFS/EPS/CMC ensemble members depict precipitation. Thus likely to categorical POPs are justified, maximized with daytime heating in the afternoon/evening, though chance POPs still linger overnight. WPC now has a slight (level 2 of 4) risk for excessive rain on Thursday from roughly US-1 eastward in NC where the frontal progression looks slowest, with a marginal (level 1 of 4) risk elsewhere. The greatest POPs shift to the south and east on Friday as the front settles near the NC/SC border. The front may retrograde back NW a bit on Saturday and Sunday, and likely POPs continue each day. However, overall rainfall amounts may decrease slightly as the front starts to wash out and upper support wanes, with Atlantic ridging building back westward. Ensemble mean QPF from Thursday through Sunday is generally 2 to 3 inches, greatest south and east, and of course locally higher amounts will always be possible where storms occur. While so much rain for multiple days in a row will cause some flooding concerns, it will provide more welcome drought relief. It will also help bring down high temperatures to upper-80s to lower-90s on Thursday (near normal) and only upper-70s to mid-80s on Friday and Saturday. A slight warming trend may commence on Sunday. Lows will be in the upper-60s to lower-70s. Fortunately widespread severe weather is not a major concern during the period given the weak shear. && .AVIATION /11Z MONDAY THROUGH FRIDAY/... As of 630 AM Monday... Patchy ground fog at KRWI will quickly dissipate. Isolated to widely scattered showers/storms will develop again this afternoon, with best chances near KFAY as convection along the sea breeze penetrates inland. Outlook: Isolated storms remain in the forecast early this week, but generally VFR is expected. A better chance of widespread showers and storms, and thus flight restrictions, occurs in the Wed-Fri period as a front settles into the region. && .CLIMATE... Record High Temperatures: July 15: KGSO: 97/1974 KRDU: 99/1997 July 16: KGSO: 99/1915 KRDU: 101/1887 KFAY: 103/1937 July 17: KRDU: 100/1887 KFAY: 102/1932 Record High Minimum Temperatures: July 14: KGSO: 77/1981 KRDU: 77/2017 KFAY: 80/2017 July 15: KGSO: 74/2019 KRDU: 76/1992 KFAY: 78/2015 July 16: KGSO: 75/2010 KRDU: 77/2010 KFAY: 78/1992 July 17: KGSO: 75/2013 KRDU: 80/1887 KFAY: 77/2019 July 18: KGSO: 76/1986 KRDU: 79/1887 KFAY: 77/2019 July 19: KGSO: 75/2016 KFAY: 77/2023 && .RAH WATCHES/WARNINGS/ADVISORIES... Heat Advisory from 11 AM this morning to 8 PM EDT this evening for NCZ008>011-023>028-039>043-073>078-083>086-088-089. && $$ SYNOPSIS...Kren NEAR TERM...CBL SHORT TERM...CBL LONG TERM...Danco AVIATION...CBL/Kren CLIMATE...RAH