Area Forecast Discussion
Issued by NWS Blacksburg, VA
Issued by NWS Blacksburg, VA
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277 FXUS61 KRNK 080732 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 332 AM EDT Mon Jul 8 2024 .SYNOPSIS... Little change in the weather pattern is expected through the end of the week. Scattered thunderstorms each afternoon and evening will have the potential to produce very heavy rain. Tuesday and Wednesday will be the hottest days of the week, with the humid conditions and unseasonably warm temperatures continuing into the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 300 AM EDT Monday... Key messages: - Highest confidence for thunderstorms and excessive rainfall in the North Carolina mountains and foothills Overall pattern keeps southeast surface and low level wind today, reacting convergence along and just east of the southern Blue Ridge. This may result in a similar training pattern as seen on Sunday with storms forming and moving northeast, then forming again near the original location were the convergence is maximized. The Ensemble situational Awareness tables showed the highest concentration of well above normal precipitable water values in the North Carolina foothills today. Rainfall will again be in the 2-4 inches/per range. This potential for excessive rainfall will be highlighted in the Hazardous Weather Outlook. Bufkit forecast soundings showed a layer of warmer air between 850 and 800 MB. It may take until 19z/3PM for to reach the convective temperature and overcome this cap. Broken layer of mid and high clouds will somewhat limit heating this morning, but starting out in the mid 60s to mid 70s, so not a stretch to get back into the 80s and 90s. Muggy surface dew points in the lower 60s to lower 70s, so no major changes to forecast lows for tonight. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 1255 PM EDT Tuesday... Key Messages: 1. Heat index values peaking between 100 and 105 Tuesday afternoon east of the Blue Ridge. 2. Near record to record high minimum temperatures for some locations Wednesday morning. The deterministic medium range models and ensembles are in good agreement that the persistent southeast U.S. upper level ridge will amplify over our area Tuesday resulting in a return to well above normal temperatures and oppressive heat index values, especially east of the Blue Ridge where these values will likely reach close to or over advisory (105 degrees) criteria. Did lower the NBM forecast high for ROA by a degree as it was an outlier compared to other members of the NBM ensembles. The upper level ridge flattens slightly on Wednesday as an upper level trof, which appears to absorb the remains of Beryl, moves into the Great Lakes region by Wednesday evening. This will bring down temperatures a few degrees, but still well above normal with heat index values still expected to be between 100 and 105 east of the Blue Ridge. NBM low temperature forecasts (which were generally followed), suggest near record to record high minimum temperatures Wednesday morning. The GEFS shows PWAT anomalies slightly above 1 standard deviation above normal on Tuesday, but increases to 1.5 to 2 standard deviations above normal Wednesday. Plus, forecast soundings show higher CAPES on Wednesday with slightly stronger 0-6km bulk shear values. As a result, lowered POPs for Tuesday (with scattered storms mainly in the mountains) and went below NBM guidance, while keeping high POPs, more closely aligned to the NBM, in place for Wednesday. areas of heavy rain and localized flash flooding is possible, especially if storms form/move over urban and poor drainage areas. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 130 PM EDT Sunday... Key Messages: 1. Localized flash flooding possible late this week. The WPC Cluster Analysis output shows increasing uncertainty with the amplitude and timing of an upper level trof moving across the Great Lakes and potentially into the northeast U.S. this weekend. This will be critical to the location of a surface boundary late this week in or close to our forecast area. Considering there will be an upper level low in the western Atlantic weakening and lifting west, then north, across the Mid-Atlantic coast on Friday, this suggests the surface boundary will have a difficult time advancing eastward and remain in, or very close to our forecast area. This will result in a good chance for showers and storms Thursday, Friday and potentially Saturday, with the ECMWF Extreme Forecast Index highlighting Friday as the day with the best chance for heavy rain and potential flash flooding. The NAEFS keeps PWAT values 1-2 standard deviations above normal late this week which provides higher confidence that locally heavy rain will be possible somewhere in the region. Will continue to highlight the threat for locally heavy rain in the HWO. With additional cloud cover expected late this week, went a couple of degrees below the NBM forecast highs, until Sunday, when the upper level trof begins to lift and the GEFS indicating 850mb temps returning to 1-2 standard deviations above normal. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... As of 325 AM EDT Monday... Overall pattern keeps southeast surface and low level wind today, reacting convergence along and just east of the southern Blue Ridge. This may result in a similar training pattern as seen on Sunday with storms forming and moving northeast, then forming again near the original location were the convergence is maximized. A majority of the thunderstorms this afternoon and evening will remain south of KBLF and KBCB. Bufkit forecast soundings showed a layer of warmer air between 850 and 800 MB. It may take until 19z/3PM for to reach the convective temperature and overcome this cap. Broken layer of mid and high clouds this morning was keeping IFR/LIFR fog and stratus patchy. Satellite showing more gaps in the high clouds west of the Blue Ridge. This favors MVFR to LIFR fog at KLWB and KBCB before 12Z/8AM. Any stratus and fog should dissipate by 13-14z. Average confidence on ceiling and wind. Below average confidence on timing and extent of thunderstorm coverage today. AVIATION OUTLOOK... Little change in the weather pattern through the rest of the week. This will result in a daily threat of thunderstorms, mainly in the afternoon and evening. Prevailing conditions will be VFR. The exception will be brief periods of IFR/MVFR with the thunderstorms and also with overnight fog. && .CLIMATE... As of 520 AM EDT Monday... Records for the warmest minimum temperatures may be set at Blacksburg on Monday and Tuesday. Tuesday looks to be the warmest day of the week so those records have been listed here. July 8th Site MaxT Year MinT Year LoMax Year HiMin Year KBLF 93 2012 45 1951 70 1947 71 1977 KDAN 103 2012 54 1979 74 1949 78 1930 KLYH 101 2012 53 1983 68 1918 75 2022 KROA 102 2012 50 1979 74 1949 77 2012 KRNK 96 1988 42 1896 67 1896 70 1941 July 9th Site MaxT Year MinT Year LoMax Year HiMin Year KBLF 92 2007 42 1918 63 1979 75 1994 KDAN 103 1977 52 2018 69 1950 76 1987 KLYH 102 1936 53 2018 66 1927 74 1992 KROA 101 1936 48 1918 68 1969 77 1992 KRNK 97 1988 42 1961 67 1927 67 1939 && .EQUIPMENT... As of 820 PM EDT Sunday... KFCX Radar is degraded...Horizontal Low Noise Amplifier is INOP, damaged by thunderstorm. Data from the radar has been compromised. Please use data with caution. A replacement amplifier has been emergency ordered. Estimated back in service time is 6PM Tuesday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AMS SHORT TERM...PH LONG TERM...PH AVIATION...AMS/PM CLIMATE...AMS EQUIPMENT...PM