Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 231301 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 901 AM EDT MON MAY 23 2016 .SYNOPSIS... A low pressure system off the mid Atlantic coastline will drift northeast and away from the region tonight into Tuesday as high pressure builds in from the west. As the high pressure system settles over the southeast states, west to southwest winds on the backside of the system will bring above normal temperatures to the mid Appalachian and mid Atlantic region by midweek. && .NEAR TERM /THROUGH TONIGHT/...
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As of 901 AM EDT Monday... Made some minor adjustments in temperatures for this morning into this afternoon, shaping ISC grids towards sfc obs and their trends. Modified pops and weather with current radar trends and leaning to RNK WRF ARW for late morning into this afternoon. Weak shortwaves will rotate around the upper low lifting to the northeast. This will result in scattered showers and isolated thunderstorms this afternoon. Similar to yesterday, some of the strongest storms will have the potential to produce some very small hail considering the relatively low wet bulb zero levels, and possibly some locally gusty winds and heavy downpours. Forecasted high temperatures look on the mark with readings in the upper 50s in the northwest mountains to lower 70s in the Piedmont. more changes later today... As of 345 AM EDT Monday... One last day of unsettled weather is expected today until much warmer weather arrives from the west for the mid- to late week period. Closed upper low pressure over southeastern VA will drift east to off the mid Atlantic coast by late today, then lift northeast to off the New England coast by daybreak Tuesday. Moisture and weak forcing rotating around the western periphery of the upper low will maintain an ongoing threat of showers to at least the eastern third of the Blacksburg forecast area this morning. Further south and west, some partial clearing on periphery of upper low combining with moist ground and light winds has allowed for some development of patchy fog from the Mountain Empire Area north toward Bluefield. Expect fog to rapidly improve/dissipate with onset of daytime heating - perhaps a bit earlier if cloud shield from upper low pinwheels back into that area. As was the case yesterday, daytime surface heating and cool air aloft under/in proximity to upper low should be sufficient to support better vertical cloud development by early afternoon. Forecast soundings again showing CAPE of around 300-500 J/Kg with relatively low freezing/wet bulb zero levels. This should be sufficient for at least some isolated thunderstorms within a broader area of increasing showers. Some of the higher resolution models imply that there may be a sweet spot for stronger storms along/near a corridor from the Alleghany Highlands southwest through the New River Valley which will be far enough removed from the more widespread cloud shield under the closed low to have a bit more initial sunshine and increased thermodynamic support - but not so far west of the upper low where the mid troposphere will be a bit drier/warmer and therefore less supportive for upward vertical ascent. Similar to yesterday, some of the strongest storms will have the potential to produce some very small hail considering the relatively low wet bulb zero levels, and possibly some locally gusty winds due to a temperature/dew point spread that will be approximately 20F - but certainly not strong enough to imply a severe weather concern. Expect to see a rapid dissipation of any lingering shower activity by early evening with loss of daytime heating and as upper low pressure finally moves away from the area. Arrival of surface ridge and clearing skies under weak subsidence may set the stage for the redevelopment of some patchy late night fog, most notably in the deeper mountain valleys, and perhaps some of the more sheltered low lying areas of the Piedmont. With little change of airmass, temperatures today will likely to be very similar to that experienced on Sunday - with highs mainly from the upper 50s across the higher elevations to around 70 along the VA/NC state line into the foothills of NC. Overnight lows tonight should be generally in the 40s in the mountains, to lower 50s across much of the Piedmont.
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&& .SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/... As of 330 AM EDT Monday... As the closed upper low finally starts to pull away from the region on Tuesday some lingering effects will keep a slight chance of a shower or storm across far northeast sections. Thereafter we will be transitioning to a very summerlike pattern with broad ridging aloft and a Bermuda high off the southeast coast. This will bring a substantial rise in our temperatures as highs go from upper 70s/around 80 east of the Blue Ridge on Tuesday to middle/upper 80s by Thursday...and readings west of the Ridge go from low/mid 70s to upper 70s/lower 80s. Humidity will also be on the rise so conditions will start to feel a bit uncomfortable and require a dusting off of the air conditioner. The heat and humidity will also create diurnal instability and give us a chance for mainly afternoon showers and thunderstorms through the middle of the week with the best chances from the Blue Ridge westward. && .LONG TERM /FRIDAY THROUGH SUNDAY/... As of 1211 PM EDT Sunday... Expect warmer...more like mid to late June type temperatures and weather into the holiday weekend as an upper ridge builds over the Southeast U.S. This pattern will favor mainly dry yet more humid conditions. There will be enough instability and moisture each day across the Appalachians to generate scattered showers and thunderstorm, with less threat in the Piedmont. The cycle will be typical diurnal afternoon/evening variety. Highs Thu-Sun will range from the upper 70s to lower 80s in the mountains to mid to upper 80s in the piedmont. Lows will generally run from the upper 50s to lower 60s mountains to mid 60s piedmont. && .AVIATION /13Z MONDAY THROUGH FRIDAY/... As of 707 AM EDT Monday... Southwestward moving bands of showers on western periphery of upper low pressure over eastern VA will continue to threaten mainly Piedmont areas with occasional MVFR flight restrictions through this morning. Further west, and a bit more removed from upper low, partial clearing over a moist ground combining with light winds supported the development of patchy fog in the SW VA and SE WV mountain valleys - bringing KBLF and KMKJ down into the LIFR range. Threat for IFR to LIFR restrictions should continue in this area into mid morning before onset of daytime heating helps to improve flight conditions back to mainly VFR weather by mid morning as fog lifts/mixes out. However, onset of heating will again help to reignite widely scattered to scattered shower/thunderstorm development by early- mid afternoon as proximity to upper low to east and associated cool pool provide sufficient instability for vertical development - similar to that experienced on Sunday, although perhaps a bit less robust in nature. As a result, have included VCTS in all terminal forecast sites for afternoon period - with threat ending by early evening with loss of daytime heating and as upper low finally begins to drift further east and away from area. Extended discussion... Overall expecting improving aviation weather after the upper low lifts out tonight into Tuesday. We will be going to a more summer like pattern mid to late week with high pressure offshore providing south to southwest flow. Thus, mainly VFR weather expected. However, the potential exists for late night/early morning fog at times around KLWB/KBCB and in some of the deeper mountain valleys. Also some convection could pop up in the mountains Thursday into Friday, making for localized afternoon/evening MVFR restrictions. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...WERT NEAR TERM...KK/WERT SHORT TERM...MBS LONG TERM...WP AVIATION...JH/WERT/WP

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