National Weather Service (2024)

Area Forecast Discussion
Issued by NWS Blacksburg, VA

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-- Discussion containing changed information from previous version are highlighted. --313FXUS61 KRNK 280554AFDRNKArea Forecast DiscussionNational Weather Service Blacksburg VA154 AM EDT Fri Jun 28 2024.SYNOPSIS...
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High pressure will track across the mid-Atlantic states today,then shift northeast off the New England coast Saturday. Afrontal boundary to our south will keep moisture aroundinto Saturday, with chances for showers and storms. Anotherfront moves in from the northwest Sunday.
-- End Changed Discussion --&&.NEAR TERM /THROUGH TONIGHT/...
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As of 130 AM EDT Friday...Key Messages:1) Upslope scattered showers/few storms through Friday night.2) Less humid today but increasing again Friday night.There is a low level theta-e ridge strung across the Blue Ridgethis morning with low level convergence. This has resulted inisolated showers. Slow movers but weak and models are fadingthis out through the early morning but would not be surprisedfor a pop up shower to form at times.For today, southeast flow will increase as high pressure worksacross the mid-Atlantic, while a front stays situated from thecoast of NC into the Gulf Coast states. Seems as we head throughthe morning, dewpoints will start to drop across western andnorthern sections of our forecast area (WV through the centralVA piedmont), but could keep higher RH across southside VA intoNC closer to the front.Models are varying on convection today, and leaned toward ablend of the Hi-RES ARW/FV3, which will have chance popssituated across the NC mountains and foothills northward to thesouther Blue Ridge and Mountain Empire of SW VA, this afternoon,with less to no coverage northeast of a Lewisburg to Danvilleline. Confidence is high that storms will be limited asinstability seems lacking but enough heating could produce a fewstorms, but nothing severe. Showers and storms will be slowmovers so some heavy rainfall appears likely but most will seelittle or no rain.Tonight, expect a lull in the evening but moisture starts toramp up again after midnight, that will see widely scatteredshowers over most of the mountains/foothills, with 20 to 30percent chance of getting any measurable rainfall, with slightlyhigher chances again over the NC mountains/foothills northeastalong the Blue Ridge into Patrick/Carroll counties in VA.Highs to will be close to normal as we have a mix of sun andclouds with more clouds across the Blue Ridge and either side.Temps will range from the mid 80s to near 90 east of the BlueRidge, to upper 70s to mid 80s west.Tonight, as dewpoints rise and cloud cover starts to increase,thinking lows will be on the warm/muggy side with upper 60s toaround 70 for most of the region.Forecast confidence is high on temperatures and winds, andaverage on sky cover and shower/storm coverage.
-- End Changed Discussion --&&.SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
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As of 100 AM EDT Friday...Key Points:1. Well above normal temperatures Saturday and Sunday.2. Showers and storms Saturday and Sunday, some with locally heavyrain and strong/damaging winds.3. Drier and cooler for Monday.A look at the 27 June 12Z NCEP Ensemble Mean 500 mb Geopotentialheights shows an upper level trough over the Upper Mississippi RiverValley on Saturday morning, with southwest flow across our region.As we progress into Sunday and Monday, this trough is expected to beover the Great Lakes Sunday morning and just east of our regionMonday morning. By Monday night, the trough will be centered overthe Canadian Maritimes with ridging building into the Ohio Valley. Atthe surface on Saturday morning, low pressure is expected to be overMichigan with a southwest trailing cold front into MO/KS/OK/AR. BySunday morning, this front is expected to be over our region. Highpressure will be nosing into the region from the west Mondaymorning, and be centered overhead by late Monday night.Output from the 27 June 12Z Ensemble Situational Awareness Tableshows 850mb temperatures on Saturday around +16C to +18C over theregion and +18C to +20C for Sunday. For sections of the region theupper end of these ranges correspond to the 90 to 97.5 percentile ofthe 30-year climatology. For Monday, values drop notably reachingthe +12C to +14C range over the area, with the low end of this rangewithin the 2.5 to 10 percentile of climatology. Precipitable watervalues for Saturday are expected to be very high for this time ofyear with numbers around 2.00 inches. This places the western halfof the region higher than the 99.5 percentile of the 30-yearclimatology and the eastern half with a range in the 97.5 to 99.5percentile. This swath of extraordinary high values sweeps acrossthe region Saturday night immediately in advance of the a coldfront. On Sunday, drier values work their way into the region by theafternoon, but values in the forenoon, especially in the southeastsections, will remain very high. Sunday night into Mondaynight, precipitable water values are expected to continue tofall. Values of 0.50 to 0.75 inch are expected by Monday intoMonday night, or values within the 2.5 to 10 percentile of the30-year climatology.The above weather scenario offers a Saturday with very goodprobabilities of showers and storms that contain moderate to heavyrainfall. Temperatures are expected to be well above normal.Additionally, The Day-3 Severe Thunderstorm Outlook from SPC offersMarginal Risk of severe weather generally for areas along and westof the Interstate-81 corridor. Damaging winds would be the greatestthreat. On Sunday, while well above normal temperatures continue,the details are not as clear on the precipitation timing. However, acold front looks to arrive early and then lingers over eastern partsof the region through mid-day and/or the passage of the 850mb coldfront helps to maintain showers and storms across mainly easternparts of the region. By Sunday night, cooler and drier air isexpected to be entering the region with this pattern continuing intoMonday night.Confidence in the above weather forecast is moderate to high.
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As of 100 AM EDT Friday...Key Points:1. Temperatures and humidity trending higher each day.2. Chance of showers/storms late Wednesday night into Thursday.A look at the 27 June 12Z NCEP Ensemble Mean 500 mb Geopotentialheights shows a building upper ridge over the Southeast US. Nearlyzonal flow is expected near the US/Canadian border. The exception isa shortwave trough that is expected to progress from the Dakotas onThursday morning to Upper Mississippi Valley by late Thursday night.At the surface on Tuesday morning, high pressure will be centeredover the area. By Wednesday morning, the high will start shiftingeast of the region as a cold front approaches through the OhioValley. By Thursday morning, the cold front will be over or near ourregion.Output from the 27 June 12Z Ensemble Situational Awareness Tableshows 850mb temperatures around +16C for Tuesday, +19C to +21C forWednesday, +20C to +22C on Thursday. The upper end of the range onWednesday falls within the 90 to 99 percentile of the 30-yearclimatology. On Thursday, much of the area is expected to be withinthe 97.5 to 99 percentile of climatology with potentially themountains of North Carolina higher than the 99 percentile. Forprecipitable water values on Tuesday, expected numbers around orjust shy of 1.00 inch. Values climb on Wednesday to around 1.50inch. For Thursday, numbers climb more to 1.75 to 2.00 inches, orwithin the 90 to 97.5 percentile of the 30-year climatology.The above weather scenario offers a period of rebuilding heat andhumidity after the cooler and drier Monday. Temperatures shouldtrend higher each day. Primarily dry conditions are expected untillate Wednesday night and Thursday with the approach/arrival of acold front and the airmass in advance of it trending progressivelyunstable.Confidence in the above weather forecast is moderate to high.
-- End Changed Discussion --&&.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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As of 150 AM EDT Friday...High probability for VFR for terminals through the period. SomeMVFR ceilings are possible at BLF/BCB/ROA if showers move acrossbut coverage today looks limited more toward the NC mountains,south of ROA/BCB/BLF.Overall anticipate SKC/SCT clouds this morning, then scatteredto broken in the 4-8kft range today into this evening, withagain possible 2-3kft cigs along the Blue Ridge south ofROA/BCB.Winds will be light this morning then turning east to southeasttoday and increasing to 8-12kts especially west of the BlueRidge. Cannot rule out a few gusts to 20kts around BLF.EXTENDED AVIATION OUTLOOK...A greater coverage of thunderstorms and associated MVFR flightconditions is expected Saturday and Sunday, but VFR outside ofany storms.Monday-Tuesday appears to be VFR as high pressure works in fromthe north.
-- End Changed Discussion --&&.RNK WATCHES/WARNINGS/ADVISORIES...VA...None.NC...None.WV...None.&&$$SYNOPSIS...VFJ/WPNEAR TERM...WPSHORT TERM...DSLONG TERM...DSAVIATION...RCS/WP