Area Forecast Discussion
Issued by NWS Blacksburg, VA
Issued by NWS Blacksburg, VA
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924 FXUS61 KRNK 071733 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 133 PM EDT Sun Jul 7 2024 .SYNOPSIS... A front will waver across central Virginia and North Carolina through the week. The chance of showers and thunderstorms will continue each day. Unseasonably warm and humid weather will also remain over the region. && .NEAR TERM /THROUGH MONDAY/... As of 121 PM EDT Sunday... Key message: - Highest confidence for thunderstorms across North Carolina and southern Virginia this afternoon and evening - Scattered showers/storm across most of the area Monday Showers continue in an widely scattered fashion across the NC piedmont into southside VA. The latest HRRR has a pretty good handle but still not enough coverage. PWATS this morning have risen to 2.12 at GSO and 1.36 at RNK. There is a bubble of moisture increasing from the southeast per loop of MSAS, with inverted trough across the upper TN Valley, with actual front stretching from the Tidewater of VA west- southwest through central NC. This configuration may allow for a little more lift swinging into southern VA this afternoon, with also some low level convergence along the southern Blue Ridge into the upper TN valley where isolated storms are possible, so a little more coverage than Saturday but still ranging from isolated/widely scattered from Bluefield-Blacksburg-Farmville, to better coverage south of the VA/NC border, and moreso in the NC mountains. With pwats this high, will have to watch for localized flooding issues as thunderstorms with be proficient rain makers and slow movers. Front stay stalled in the vicinity through Monday and southwest flow aloft plus any embedded weak waves combined with low level moisture convergence will keep the threat of showers/storms around, however, most will stay dry in terms of rain but the humidity stays elevated especially along/east of the Blue Ridge. Any storms will be working with high moisture content Monday as well, so localized flooding is possible, especially if it rains where it does this afternoon/evening with urban areas and steep terrain more prone. Still isolated so not anything close for a watch. Lows tonight stay elevated in the mid to upper 60s west of the Blue Ridge to lower 70s east. Fog could get locally dense in the mountain valleys and where it rains this afternoon/evening if enough clearing takes place. Highs Monday will be dependent on cloud cover and should more clouds than sun, but enough to send temperatures into the 80s in the mountains to lower 90s Piedmont. Forecast confidence is moderate on rainfall coverage and temps. && .SHORT TERM /MONDAY NIGHT 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 /18Z SUNDAY THROUGH FRIDAY/... As of 125 PM EDT Sunday... Scattered to broken cumulus with some TCU/CB possible this afternoon. Best chance of TCU/CB will be along/south of a HLX- DAN line. As such have some showers around DAN this afternoon with VCTS as well. Cannot rule out some development toward BCB/BLF but low confidence. Mainly VFR outside any showers/storms with cigs in the 4-8kft range. Front will remain in place through Monday across the Piedmont. Anticipate some fog/low clouds at time late tonight, mainly BLF/LWB/BCB but could have some at DAN as well. Vsbys could drop as low as 1/2sm at LWB. Ceilings/vsby should rise to VFR after 13-14z. Widely scattered storm set up for Monday afternoon after this taf period. Low confidence on cigs/vsbys tonight with average on storms. High confidence in mainly VFR outside of storms/fog. AVIATION OUTLOOK... Little change in the weather pattern and location of the front is expected 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 Sunday... 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 7th Site MaxT Year MinT Year LoMax Year HiMin Year KBLF 93 2012 44 1951 65 1967 73 1998 KDAN 104 2010 55 1979 76 1961 78 1921 KLYH 100 2012 52 2001 72 2005 75 1977 KROA 102 2012 48 1983 74 2005 78 1977 KRNK 94 2010 41 1972 67 1967 67 2022 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 520 AM EDT Sunday... KFCX Radar is degraded...Horizontal Low Noise Amplifier is INOP, damaged by thunderstorm. Please use data with caution. High reflectivity above 40 dbz appears OK, but the radar is unable to detect and lower reflectivity. A Low Noise Amplifier has been emergency ordered. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS/WP NEAR TERM...WP SHORT TERM...PH LONG TERM...PH AVIATION...AMS/WP CLIMATE...AMS EQUIPMENT...PM