Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 251102 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 702 AM EDT Tue Oct 25 2016 .SYNOPSIS...
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Cool high pressure will build in from the northwest today and remain wedged along the eastern slopes of the Appalachians into Wednesday. Low pressure crossing the Great Lakes will push a cold front through our region on Thursday. High pressure follows the front for the end of the week.
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&& .NEAR TERM /THROUGH TONIGHT/... As of 230 AM EDT Tuesday... Quiet weather regime under diminishing winds to prevail over the next 24 hours as surface high pressure builds to the north today before orienting south along the eastern slopes of the Appalachians overnight. This should keep very dry air/subsidence in place today with only some patchy upslope low clouds far northwest sections early this morning. Temperatures remain quite varied attm from 30s in the deepest valleys to as mild as around 50 on the ridges. Therefore will maintain the going frost advisory with focus mainly in the valleys for frost early this morning. Highs today a bit cooler than Monday behind the front given the passing trough aloft and more northerly flow to start. However warming of dry air along with the flow turning more west/southwest aloft later today across the west, supports highs at or slightly above mos which gives upper 50s to mid 60s overall. Main question tonight will be with the frost potential out east as winds remain light and dewpoints dry under the surface ridging. Only caveat appears with some high cloud potential as weak shortwave ridging to the west helps drop a speed max through the region from the northwest with some associated high/mid cloud canopy per model time sections. This could be enough to keep frost mostly patchy at best and confined to more outlying areas so including mention near daybreak but without any advisory headlines for now. Otherwise one of the colder nights seen so far with lows mostly 30s to low 40s ridges, except perhaps a few 20s far western valleys, where not including any added frost/freeze headlines beyond this morning per end of the growing season. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... As of 330 AM EDT Tuesday... We will start the period with a cool and relatively dry wedge of high pressure east of the Appalachians bringing a mix of sun and clouds to the region. By Wednesday night the upper ridge axis will slide by to our east as a trof approaches from the west. The bulk of the short wave energy in the trof looks to remain off to our north, along with the best isentropic lift and strongest winds in the southwesterly low level jet. This will take the surface low and bulk of precipitation through the Ohio valley into New England, with the trailing cold front moving through our area on Thursday. Expect this scenario will bring breezy conditions and high chance to likely POPs for areas west of the Blue Ridge by early Thursday with lower chance POPs further to the east across the piedmont. While mid/upper level lapse rates are steep on Thursday, believe best dynamics are too far removed to generate a significant chance for thunder so will keep mention out of the grids for now. As the front pushes off to our east Thursday night, blustery west winds will combine with lingering moisture to keep a chance of showers in the mountains before the moisture starts to wane. High pressure returns for Friday with breezy conditions and seasonable temperatures, though a bit cooler across southeast West Virginia. Expect temperatures in the wedge on Wednesday to be in the mid/upper 50s with low/mid 60s along the southern and western periphery. Mixing out the wedge on Thursday will allow temperatures to reach the mid/upper 60s east of the Ridge with low/mid 60s to the west. Readings will be a bit cooler in the west behind the front on Friday with upper 50s/lower 60s, but some downslope will boost temps to the east with lower 70s in the foothills of North Carolina to the mid/upper 60s across the NC/VA piedmont. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... As of 300 PM EDT Monday... A low pressure system will track from the Great Lakes to New England Friday into Saturday. The associated front with this system will slowly move south across the forecast area Saturday and Saturday night. Since we have a ridge blocking the Gulf and bulk of the precipitation and energy will be with the parent low to the north, we are only forecasting scattered light showers north of 460 and sprinkles or just an increase in clouds south. Both the GFS and ECM are at odds with the forecast for Sunday and Monday. For now, we will keep conditions dry. Temperature will be above normal Saturday with areas along the VA/NC border warming into the 70s. Temperatures cool down behind the front Sunday but are expected to remain above normal into early next week. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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As of 645 AM EDT Tuesday... Widespread VFR under light winds expected today and tonight with high pressure in control. However may see some late night river valley fog across a few of the mountain valleys late tonight espcly around KLWB where will include brief LIFR toward daybreak. Also frost likely in the valleys with some patchy nature coverage in the east as well around dawn. Extended aviation discussion... Still expecting overall VFR to continue Wednesday into Wednesday night with surface high pressure ridging south across the region. However some potential to see areas of sub-VFR in patchy strato-cu espcly Blue Ridge and points east although confidence low given such dry air in place. Thursday...Low pressure is forecast to move across the upper midwest and into the Great lakes with a surface front crossing the Ohio Valley. Threat for showers and sub-VFR will be possible along this front which would impact the central Appalachians by Thursday afternoon. However given best support passing to the north and limited moisture, expecting best potential for lower cigs/vsbys to occur across the western mountains and across northern portions of the area at this point. High pressure builds in from the northwest Friday, with potential MVFR ceilings at KBLF/KLWB before the high arrives. Another front may cross through the region on Saturday with possible showers and MVFR ceilings in the mountains. However, models were still showing differences in the timing of the weekend system.
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&& .FIRE WEATHER... As of 315 AM EDT Tuesday... Very dry conditions will continue to persist today as high pressure builds into the region from the northwest and wedges down east of the mountains by the middle of the week. Expect this to help reduce winds this afternoon with speeds on average below 10 mph. This while the flow turns more northeast across eastern sections with variable to light westerly trajectory across the mountains through the afternoon. Temperatures will also be cooler but given the arrival of even drier air behind a cold front from Monday, appears afternoon humidity levels will fall to between 20 and 30 percent across much of the region. Therefore will continue to headline the fire weather forecast (FWF) for low humidity levels today. Humidity may recover a little on Wednesday ahead of an approaching cold front. This front should bring the next round of scattered showers Thursday although the chances for widespread wetting rainfall appear low at this point. Dry air returns again for the end of the week behind the front. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...Frost Advisory until 9 AM EDT this morning for VAZ007-009-010- 020. NC...None. WV...Frost Advisory until 9 AM EDT this morning for WVZ042>044-507- 508. && $$ SYNOPSIS...AMS/JH NEAR TERM...JH SHORT TERM...MBS LONG TERM...MBS/RCS AVIATION...AMS/JH/WP FIRE WEATHER...JH is the U.S. government's official web portal to all federal, state and local government web resources and services.