Area Forecast Discussion
Issued by NWS Blacksburg, VA

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545 FXUS61 KRNK 241801 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 201 PM EDT TUE MAY 24 2016 .SYNOPSIS... Our stretch of cool weather will be coming to an end as high pressure builds over the southeast United States and ushers much warmer air into the region. Temperatures will be well above normal for most of the week with highs by Thursday ranging from the upper 80s across the piedmont to the lower and middle 80s west of the Blue Ridge. However along with the warm temperatures will come increasing humidity and the chance for afternoon showers and thunderstorms. && .NEAR TERM /THROUGH TONIGHT/... As of 1155 AM EDT Tuesday... Morning RNK sounding still pretty cool aloft. This will allow for at least scattered clouds this afternoon per steep low/mid level lapse rates. Forecast soundings indicate modest cu depth with cloud bases around 4kft and max cloud depth to about 10kft. This may generate a few sprinkles, but overall trend is for warming to take place aloft, 700 mb temperatures increasing from m1 deg C to +2 deg C by the end of the day. This should cap cloud depth and prevent deep convection. The Meso models and HRRR generate some isolated showers, but POPs AOB 10%. The upper low which has been with us for several days will still have enough influence over our weather today to keep a just a slight chance of showers across the region...especially far north and east...thanks to the combination of diurnal instability and steep lapse rates in the cold pool of air aloft. The prospects for thunder look to be very limited indeed so will not include in the grids. As the day wears on and the low continues pulling off to the northeast much warmer air will begin to surge in from the southwest. This will give our temperatures a much needed boost to slightly above normal...which should feel like a tropical heat wave after our recent stretch of cool weather. Expect highs today to reach the lower 80s east of the Blue Ridge with generally middle and upper 70s to the west. Tonight looks to be quiet with mostly clear skies and lows ranging from the middle and upper 50s east to upper 40s and lower 50s west. There may also be valley fog forming once again late tonight into early Wednesday morning. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/... As of 400 am EDT Tuesday... Upper heights and 850mb temps continue to rise through the period as the northeast U.S. upper low continues to lift northeast into the north Atlantic and troughing deepens and shifts inland across the southwest U.S. Upper heights across our region will be nearing 588dm with 850mb temps averaging near +16C through the period. This will result in much warmer temps than we have seen over the past 14 days...with temps actually above normal through the entire period...generally lows in the 50s to lower 60s and highs in the 70s mountains and 80s elsewhere...nearing 90 across the Piedmont. Little if any synoptic-scale forcing is evident on Wednesday with weak upper ridging in place...but all models depict an area of moisture pooling across the Appalachians..typical of differential heating across the mountains...which could yield isolated to widely scattered afternoon showers/thunderstorms. Instability is minimal at this point...so with no dynamics...activity would be diurnally driven and non-severe. On Thursday...the pattern becomes slightly more interesting and more active convectively speaking. While the region is still under broad upper ridging...the southwest U.S. tough continues to shift inland...but more importantly a notable short wave is ejected to the northeast of the parent upper low into the TN/OH valley by afternoon. The NAM hits the feature the hardest...but it is evident via all of the longer range models. This increase in forcing along with increased thermodynamics...should yield scattered showers and thunderstorms...again largely diurnally driven. By Friday...the aforementioned disturbance has moved to our northwest...but again a notable area of moisture pooling is evident across the mountains...but the best area of such has shifted slightly northwest from Thursday`s location. Of more importance at this point is a potential tropical system apparent in most models developing off the southeast U.S. coast. While all models indicate this system in varying degrees...there are vast differences in the track of such system...with the GFS most aggressive in taking in inland into SC/NC...where it circulates about into the weekend and early next week. This feature may serve initially to induce increased subsidence across the south and east portion of our CWA Friday...but beyond that...cannot hinge on any one solution at this point. && .LONG TERM /SATURDAY THROUGH MONDAY/... As of 415 am EDT Tuesday... As noted in the section above...weather conditions across the region through the weekend and into early next week will depend largely on the track...intensity...and evolution of a potential tropical system moving from the Bahamas northwest into the southeast states per GFS...or hugging the SC/NC coast line per most other models. Clearly...the GFS solution would have a significant impact on our region in terms of cloud cover and precipitation...while other model solutions keeping the low track closer to the coast...would result in more subsidence across our region and minimal impacts. For sure temperatures will remain on the warm side with no significant change in air mass underneath a continuing large-scale ridge...with humidity levels high through the period. Meanwhile...the western system remains mostly intact across the western states while overall weakening and lifting more north than east. Thus...outside a potential tropical system...the pattern is becoming more-and-more summerlike than we have seen so far this year. Look for a continuation of highs in the 70s mountains and 80s elsewhere...with lows mostly in the 50s and 60s. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... As of 200 PM EDT Tuesday... Closed upper low continuing to spin off the New England coast, this feature gradually moving northeast and away from the forecast area. Influence less than in previous days, but still close enough to generate high based cu/sc and some mid clouds, mainly east of the Blue Ridge. Cannot completely rule out an afternoon shower east of the Blue Ridge, coverage certainly not enough to include in the tafs. if there is a risk it would be northeast of KLYH through sunset. after sunset...expecting clear skies all terminals. Wet antecedent conditions from rainfall previous days in combination with light winds and clear skies will promote valley fog formation in the mountain valleys tonight. Main impact will be KLWB/KBCB and vicinity. Expect fog to lift fairly quickly after 9 AM Wednesday with return of widespread VFR. Winds generally light WNW-WSW through the period...speeds 10 mph or less...near calm after 00Z/8PM...increasing again after 13Z/9AM Wednesday but generally less than 10 mph. Extended discussion... Wind flow through Friday will be out of the southwest with the weather pattern more reflective of summer conditions, primarily VFR except for widely scattered afternoon and evening showers during the peak heating part of the day. Nightime fog also possible in the mountain valleys, but mainly after midnight up until an hour or two after daybreak. Potential wind flow change is advertised by the models this weekend per development of a storm system off the southeast Atlantic Coast. Models differ quite a bit on timing and movement of this feature so low confidence forecast beyond Saturday attm. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...MBS NEAR TERM...MBS/PM SHORT TERM...RAB LONG TERM...KK/RAB AVIATION...PM

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