Area Forecast Discussion
Issued by NWS Blacksburg, VA
Issued by NWS Blacksburg, VA
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606 FXUS61 KRNK 132319 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 719 PM EDT Sat Jul 13 2024 .SYNOPSIS... A weak boundary will linger across the Piedmont into Sunday, with limited shower and storm coverage. Afternoon thunderstorm chances can be expected Monday through Tuesday, while another system brings more widespread rain towards midweek. Temperatures will increase with heat index values approaching 100 degrees in Piedmont again for much of next week. && .NEAR TERM /THROUGH SUNDAY/... As of 715 PM EDT Saturday... Key Messages: 1) Warm weather continues; humidity remains in check through the weekend. 2) Isolated convection possible each afternoon....but unlikely to affect most. Isolated showers/few cloud to ground strikes observed on radar/lightning network around Lynchburg. Not much in the way of coverage and should stay that way into this evening. Skies overnight expected to be mainly clear with patchy fog toward dawn in the valleys. Previous discussion... Skies are sunny over much of the area, with some daytime cumulus clouds over the mountains, and additional lower level moisture over parts of the VA and NC Piedmont. Upper level flow is more progressive through tomorrow as short wave energy shifts SE from the western Great Lakes and Canada, and the blocking high over the Atlantic Ocean is suppressed. A stationary front just inland from the Mid Atlantic will shift offshore tomorrow morning as high pressure builds in. In the meantime, an isolated thunderstorm or shower is possible this afternoon for the extreme eastern/southeastern part of the forecast area, where the lower level cloud cover/moisture intersects the front. There is also an isolated chance for convection over the southern Blue Ridge. These cells will weaken with sunset. Today has been warm but not especially humid, and expect clearing skies overnight to support lows in the low 60s to low 70s, with patchy fog once again in the morning. Isolated cells may form again Sunday afternoon, mainly south of I-81, as short wave energy crosses the area. It will be hot again, but overall pretty similar to today, with humidity remaining manageable. Confidence in the near term is high. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... Issued at 111 PM EDT Sat Jan 13 2024 Key Messages: - Above normal temperatures are expected early next week. - Heat indices greater than 100 degrees are expected east of the Blue Ridge Monday and Tuesday. - A limited coverage of showers and thunderstorms is possible near the Blue Ridge. Ridging, both at the surface and aloft, will remain the dominant weather feature for our area heading into early next week. Despite a lack of forcing, sufficient instability (with most likely MLCAPE values between 1000-1500 J/kg)could combine with limited moisture pooling near the Blue Ridge and allow a few afternoon showers or thunderstorms to develop Monday and Tuesday. Any convection that develops should be short-lived and dissipate after the loss of daytime heating. Of greater importance will be the heat, thanks partially to the subsident flow and limited moisture. The bottom line (to quote lyrics from a 40 year-old song) - it`ll be "hot, hot, hot." Confidence is very high that afternoon temperatures Monday and Tuesday will likely average 10 to 15 degrees above climatological norms for mid-July, with highs in the 90s just about everywhere to start the workweek. Tuesday will be even warmer; probabilistic guidance indicates a near certainty (approx. 90% odds) that afternoon temperatures will exceed 95 degrees in the Piedmont and Southside Virginia. In fact, it`s not out of the realm of possibility that afternoon highs could flirt with the century mark across parts of Central Virginia Tuesday afternoon. I`ll keep forecast high temperatures above guidance values since the deterministic output remains at least in the upper quartile of the ensemble spectrum. An increased number of heat-related impacts may be seen as a result of the hotter temperatures. Heat indices between 100 and 104 will likely be seen by Monday afternoon across the Piedmont and Southside, as well as parts of the Roanoke and Shenandoah Valleys. By Tuesday, heat indices will likely reach or exceed 105 in the aforementioned areas. This may require the issuance of Heat Advisories across our area at some point Monday and/or Tuesday. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... Issued at 111 PM EDT Sat Jan 13 2024 Key Messages: - Above normal temperatures continue through Wednesday, with heat indices above 100 still possible. - Shower and thunderstorm probabilities return for the middle and latter half of the upcoming week. Ridging will weaken a little Wednesday, as an upper-level low continues moving across southern Canada. The feature should amplify somewhat, as energy digs into the back side of the low. This should help push a cold front southeastward across the Great Lakes and toward our area. Low-level moisture should increase across the region Wednesday, as boundary layer winds become more southwesterly ahead of the front. Precipitable water values are expected to exceed 1.5 inches, which is between 1.5 and 2 standard deviations above climatological means for this time of year. This, combined with ample instability and increased forcing, should produce an increased coverage of showers and thunderstorms by Wednesday afternoon. Prior to any convective development, Wednesday afternoon`s heat indices could again reach the 100-104 degree range across parts of the Piedmont and Southside. The front should enter our neck of the woods Wednesday evening. From there, longer-range guidance still differs in how quickly the front will move through our region. My current thinking is that the front`s movement will become sluggish across our area Thursday, then get a good push Friday as the Canadian upper-low opens up and finally pushes the system out of our area. That means we will likely see a more widespread convective coverage continuing into Thursday (especially in the afternoon and evening), before the greater coverage shifts south Friday. This is pretty good news overall considering the ongoing dry conditions in our forecast area. And here`s another bit of good news - we should see a return to more reasonable temperatures toward the end of the week (for this time of year anyway) thanks in part to the increased cloud cover and greater coverage of precipitation. Surface high pressure should build across Ohio and Pennsylvania by next Saturday. The northeasterly flow around this feature should help bring a return to slightly drier conditions to at least northern parts of our area. Areas farther to the south will remain closer to the front and could continue to see a slightly greater coverage of showers and thunderstorms. Given the uncertainty in the location of the front at this stage of the game, I don`t plan on straying too far from guidance at this time. && .AVIATION /23Z SATURDAY THROUGH THURSDAY/... As of 715 PM EDT Saturday... VFR conditions expected for the 24 hour TAF cycle, except for patchy morning fog. The fog may drop to LIFR at LWB between 07-13Z. Winds look to be light to calm through the period. Forecast confidence is high. AVIATION OUTLOOK... Daily afternoon SHRA/TSRA chances continue each day through Tuesday, and dissipate at night. A front crosses the region Wednesday and Thursday, bringing more widespread SHRA/TSRA and sub-VFR conditions. && .CLIMATE... As of 715 PM EDT Saturday... Blacksburg tied the record high for today of 92 degrees. The previous record was set in 1936. Roanoke managed 98 degrees, one shy of the record of 99 set in 1954. Except for perhaps the daytime high for Blacksburg on July 16, we currently are not forecasting record high temperatures or record maximum low temperatures Monday, July 15, and Tuesday, July 16, values will be close enough that some folks might be curious what the records are. Below you will find a table that lists these values for different locations in our region and the years those records were set. ************* RECORDS FOR July 15 ************* +=============================================+ | LOCATION | RECORD HIGH | RECORD MAX LOW | | Blacksburg | 99 in 1954 | 72 in 1954 | | Bluefield | 91 in 1951 | 72 in 1942 | | Danville | 104 in 1936 | 79 in 1922 | | Lynchburg | 101 in 1936 | 77 in 1988 | | Roanoke | 103 in 1936 | 74 in 1995 | +=============================================+ ************* RECORDS FOR July 16 ************* +=============================================+ | LOCATION | RECORD HIGH | RECORD MAX LOW | | Blacksburg | 93 in 1983 | 70 in 2020 | | Bluefield | 96 in 1988 | 71 in 1980 | | Danville | 102 in 1934 | 77 in 1920 | | Lynchburg | 103 in 1934 | 76 in 1937 | | Roanoke | 100 in 1988 | 74 in 2020 | +=============================================+ && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...SH/WP NEAR TERM...SH/WP SHORT TERM...DB LONG TERM...DB AVIATION...SH/WP CLIMATE...DS