Area Forecast Discussion
Issued by NWS Blacksburg, VA

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183 FXUS61 KRNK 261703 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 103 PM EDT Mon Jun 26 2017 .SYNOPSIS... Weak high pressure will linger over the area today. An upper trough and associated cold front will move through the area Tuesday. A large area of high pressure will build over the area behind the front for Wednesday, then move east of the area Thursday through Friday. Mostly dry conditions with below normal temperatures are expected through Wednesday with warmer, more humid conditions and returning chances for showers and thunderstorms are expected during the later half of the week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 1255 PM EDT Monday... The early afternoon forecast update will reflect only limited changes to the overall general trend for the forecast. Have increased cloud cover across the region per latest satellite depiction across the region. This includes mid to high level clouds in association with a jet streak, and diurnal cumulus due to diurnal and differential heating across the mountains. Forecast high temperatures have not been adjusted by more than plus or minus or or two degrees from the previous forecast. As of 955 AM EDT Monday... The update this morning will reflect primarily minor cosmetic changes to the hourly temperature, dew point, wind, and sky cover forecast grids to reflect the latest observations and expected trends into the early afternoon. No significant changes to the overall forecast for the day is being made. As of 400 AM EDT Monday... Little change expected in the weather across the region today from what was observed on Sunday. 850mb temperatures will change little from around +8C on the northern end of the CWA to around +12C in the southern areas. Broad troughing, anchored across the Great Lakes will continue leaving the area with below normal heights and temperatures as noted above. With the air mass fairly dry, only expecting scattered CU development today with limited cirrus. Slightly breezy west to northwest winds, but otherwise an extremely pleasant day for late June with high temperatures mostly in the 70s west to the lower and mid 80s east after a cool morning with lows in the 50s to lower 60s. Not really very June like, but nice! Overnight into early Tuesday, a stronger short wave embedded within the Great Lakes upper trough will move toward the region, then is slated to sweep through the area Tuesday. Mid clouds will be on the increase overnight in advance of this feature. Not very excited about precipitation with this system, especially prior to 12Z given the limited moisture it has to work with, e.g., PWATS less than 1 inch. However, dynamics may be strong enough to overcome the lack of deep moisture and some light rain showers or more likely sprinkles may begin to develop across eastern KY/TN/WV before daybreak Tuesday, so have introduced some slight chance pops into the Richlands/Bluefield/Independence areas before daybreak Tue. Low temperatures overnight might be a tad warmer in the west than this morning thanks to increased cloud cover, but will still be below normal for late June, mostly in the 50s across the CWA. Radiational cooling will be more effective across the Piedmont Tuesday morning.
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&& .SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/... As of 330 AM EDT Monday... An upper level trough will pivot over the Ohio and Mid Atlantic region Tuesday. Short waves coming across the area will use all available moisture to produce scattered showers through the day. The best coverage will be across the mountains in the morning. Models are wanting to push these showers east of the Blue Ridge, however with a northwest transport wind of 15 to 25 mph and cloud bases at or above 7 kft, sprinkles may be the best bet in the early afternoon. Drier air moves in quickly as high pressure builds in from the west to end the threat for rain Tuesday evening. With abundant cloud cover and rain in northwest flow, Tuesday`s temperatures may run 10F cooler than normal. Cool dry high pressure will drift over the region Wednesday. With plenty of sunshine and a dry air mass, afternoon temperatures will warm into the 70s across the mountains to the lower 80s east of the Blue Ridge. This high will slide off the VA/NC coast Wednesday night and Thursday. Southerly flow on the back side of this ridge will bring temperatures back to seasonal levels. Dew points will also return back to the 60s by Thursday afternoon. && .LONG TERM /FRIDAY THROUGH SUNDAY/... As of 230 PM EDT Sunday... Trough lifts out and 5h ridge works in ahead of the next upstream trough over the northern tier of the U.S. Will see return flow around southeast high with temps/dewpoints returning to typical late June/early July numbers. Also with differential heating and some weak upper impulse should expect to see more storms Friday-and as front across the midwest edges closer to the Ohio Valley, should see a better chance into the weekend especially over the mountains. && .AVIATION /17Z MONDAY THROUGH FRIDAY/... As of 740 AM EDT Monday... VFR conditions expected to continue through the TAF valid period. A broad upper trough remains over the Great Lakes. An embedded short wave will deepen on the southwest side of this upper trough and move southeast through our region late tonight and Tuesday. Low-level moisture is limited, but dynamics are strong so expect a period of mainly mid clouds and a few showers or sprinkles, mainly west of the Blue Ridge after 12Z Tue. Ceilings through this TAF valid period are expected to be mainly at or above 100, with a brief period of BKN cigs possible in some areas this afternoon in the 050-060 range, clearly still VFR. Fog failed to develop this morning as air mass has dried out and increased clouds should prevent fog development overnight into Tuesday morning. The exception could be the Piedmont, such as KLYH and KDAN, but have not advertised for now because confidence is too low. Given expected thick mid/high clouds have left fog out of KLWB for Tue morning, despite indication from several MOS guidance packages of LIFR at KLWB around 12Z Tue. That appears to much driven by climatology at this point, not meteorology. Winds will remain W to WNW through the TAF valid period at speeds of 6-12kts daytime with low end gusts at most stations during the late morning/early afternoon mostly < 20kts. Winds will diminish to 5kts or less after 23Z. High confidence in VFR cigs through the TAF valid period. High confidence in VFR vsbys through 08Z Tue, then medium to high confidence. Medium to high confidence in wind speed/direction through the TAF valid period. Extended Aviation Discussion... A weak disturbance dropping in from the northwest may bring a period of MVFR cigs along with a few showers to the mountains Tuesday, mainly during the first half of the day. Otherwise expecting overall VFR for Monday through Thursday with some brief late night/early morning mountain and river valley fog possible. By Friday, a large area of high pressure will drift to the southeast of the area and be located off the SC/NC coast into the weekend. This will allow a warm/moist southwest flow to return to the area. As a result look for increasing diurnally driven convection into the weekend, most numerous over the mountains. This will increase the threat for brief periods of sub-VFR cigs/vsbys in afternoon/evening thunderstorms. It will also increase the likelihood of late night/early morning fog/low clouds, especially west of the Blue ridge with sub-VFR cigs at times during these hours. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...RAB NEAR TERM...DS/RAB SHORT TERM...RCS LONG TERM...RCS/WP AVIATION...RAB

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