Area Forecast Discussion
Issued by NWS Blacksburg, VA

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154 FXUS61 KRNK 300456 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1156 PM EST Tue Nov 29 2016 .SYNOPSIS... A weak front will remain just west of the area tonight into early Wednesday allowing a series of upper disturbances to track along the boundary. This will result in periodic rounds of showers again later tonight into Wednesday. A stronger cold front will pass through the region Wednesday night bringing drier and cooler weather for the end of the week. && .NEAR TERM /THROUGH WEDNESDAY/...
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As of 1145 PM EST Tuesday... HAve trimmed probability of precipitation back until 06Z/1AM when models bring the leading edge of the precipitation over the Tennessee valley into southwest Virginia and northwest North Carolina. HAve added fog in the forecast where there was less cloud cover this evening and winds were light. Although models have trended west with the most widespread rainfall, closer to the surface boundary under sharpening flow aloft, appears enough deep moisture advecting into the warm sector to produce a few bands of showers across the region late. Southerly jet will also increase mainly far west ahead of this next impulse although appears stronger winds should stay far enough west to preclude any advisory headlines for now. Otherwise only slow temp falls overnight given high dewpoints while clouds return with lows mostly 50s to lower 60s. Front and its associated sharp axis of deep moisture and heavier showers look to remain across or just west of the western slopes into early afternoon Wednesday before pushing east. Some solutions including the Nam/EC remain quite slow to edge the shower axis east while others faster with at least scattered rounds of isolated showers west early on. Since ensembles remain a little faster, kept higher pops over the mountains before swinging the band of heavier rainfall east during the afternoon as the upper trough gives moisture a bit of an eastward boot. Strong diffluence along with an impressive jet aloft of concern in mixing some winds down to the surface and may need an advisory for this combined with gradient winds just ahead of the rainfall mainly far west Wednesday. Deeper convective threat looks limited but again low topped more elevated nature thunder could occur despite limited instability. Thus including stair stepped mention across the region from west to east Wednesday afternoon given wind potential. Overall QPF looks to range from over an inch far west to close to an inch Blue Ridge to less out east at this point. Flow turning more southwest and increasing should push highs well into the 60s if not low/mid 70s east espcly if precip is slower and some breaks develop.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... As of 320 PM EST Tuesday... A cold front will slide across the region Wednesday night ushering in cooler temperatures on Thursday. By Thursday morning, temperatures will range in the 30s across the mountains to the low to mid 40s east of the Blue Ridge. Temperatures will slowly warm Thursday with mid to upper 40s west and mid to upper 50s east. The rain showers will exit the piedmont by midnight then should see a some upslope light precipitation across western Greenbrier Thursday morning before dry air surges into the region. Upslope precipitation above 3000 feet will primarily be light snow while lower elevations transition from rain to flurries through the morning. Pressure rises behind the front will also bring breezy and gusty conditions to the area subsiding Thursday evening. The northern and southern stream becomes separated starting Friday with zonal flow over the region. Looking aloft, the forecast area will be under the influence of the northern stream with 85h temperatures running -4C to -6C going into the weekend. Friday`s high temperatures will range in the 40s across the area with 30`s along ridgetops. Besides a few mountain fair weather cumulus clouds, Friday will remain dry. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 300 PM EST Tuesday... A closed low over north Mexico will generate a disturbance over Texas Saturday. Moisture from this disturbance will get caught in zonal flow and bring an increase in clouds over the region for the weekend. An area of dry high pressure will become anchored over the area keeping bulk of the moderate to heavy rain south across the Gulf states this weekend. On Monday, the closed low exits Mexico and enters the midwest. This system will bring warm Gulf moisture over a lingering dry surface high Monday. Precipitation falling into this dry high will create an insitu wedge. Depending on the timing and availability of cold air, precipitation could start out as a light snow across the mountains, changing to rain over time. Both the GFS and ECM agree on this solution, but differ on timing, precipitation amount and p-type. The GFS has precipitation entering Monday whereas the ECM is Tuesday. For now, we will carry low PoPs for the area and a rain/snow mix for p-type mainly across the mountains. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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As of 1145 PM EST Tuesday... Expecting MVFR to IFR clouds to fill in over southwest Virginia, northwest North Carolina and southeast West Virginia tonight. LIFR fog developed at locations that had rain Tuesday afternoon and stay cloud free longer. Winds will pick up overnight, especially at higher elevations as the low level increases from the southwest. Low confidence on the timing for when visibilities will improve as fog erodes. Area of upper diffluence that was providing lift for the showers and thunderstorms over Mississippi and Tennessee will move into the region late tonight. Guidance was in good agreement keeping much of the area dry until after 06Z/1AM. Some warm air advection also in the region tonight and Wednesday morning which will aide in lift. Next band of heavier showers and will cross the region from west to east Wednesday afternoon allowing for widespread sub-VFR cigs and vsbys until the front crosses Wednesday evening. Shallow convection may enhance the winds. High confidence on the passage of the front and associated moderate showers but lower confidence on the exact timing. Extended aviation discussion... Improving conditions expected after the upper low and final short wave move east of the area later Wednesday night. Conditions should become VFR east of the Blue Ridge into the weekend. Upslope clouds and potentially a weak clipper system could bring a low chance of rain or snow showers into the western sites Thursday and Friday along with lingering MVFR cigs before conditions improve there as well over the weekend.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH NEAR TERM...AMS/JH SHORT TERM...RCS LONG TERM...RCS AVIATION...AMS/JH is the U.S. government's official web portal to all federal, state and local government web resources and services.