Area forecast discussion National Weather Service Blacksburg Virginia 734 am EDT Sat may 25 2013 Synopsis... high pressure will control our weather heading into the weekend. Early next week a warm front lifts north across US...reaching the Great Lakes by midweek. This will bring a return of temperatures and weather more typical of Summer. && Near term /through tonight/... as of 400 am EDT Saturday... High pressure continues to build into the region this morning. Surface observations indicate light winds everywhere except the higher ridges which are above the nighttime inversion...where still seeing gusts in the 20 to 25 miles per hour range. Otherwise...looking at clear skies. Still have a freeze warning in effect for several of our mountain counties...however it appears that freezing temperatures will be localized and confined to deeper valleys across the warning area...and that most locations will remain above freezing. With plenty of dry air in place...temperatures will spike upward quickly after sunrise. Will start the day off with clear skies...however thin high clouds will build in from the west during the afternoon and evening. Winds will not be as strong today compared to those of Friday as the pressure gradient is far more relaxed...but we can still expect occasional gusts to 20 miles per hour for late morning and the afternoon...more so across the mountains. Wind speeds will diminish quickly by sunset. Highs for today will be a little warmer as well...but still unseasonably cool...with afternoon temperatures reaching into the low to middle 60s across the mountains...and into the low 70s across the piedmonts. For Saturday night...the Alleghany Highlands and portions of southeast West Virginia will experience mostly clear skies and light winds...while thicker cloud cover will be confined further south. With temperatures bottoming out in the middle 30s toward sunrise Sunday morning across our northwest counties...believe there is a chance of patchy frost across Bath...Greenbrier and Monroe counties...although localized frost may also develop elsewhere across the mountains north of Interstate 81. Otherwise...expect to remain precipitation free through the night. && Short term /Sunday through Tuesday night/... as of 530 am EDT Saturday... This period will be the transition period from the deep upper low and associated unseasonably cold temperatures across the middle-Atlantic region to a bonafide summerlike subtropical ridge building in from the central U.S. By mid-week. 850mb temperatures will rise from near 0c early Sunday across the NE part of the County Warning Area to near +20c in the SW part of the County Warning Area by mid-week. Previous runs of the models had been advertising good potential for ridge rider... mesoscale convective system activity as the baroclinic zone lifted north across the region Monday-Tuesday with strong middle-level warm air advection on the back side of the departing upper low. However...recent runs of the models have backed off considerably on this potential. There is still some threat for an mesoscale convective system to develop across Illinois/in/OH/KY area late Monday and move southeast through the northwest flow aloft. The best track for this...if it occurs...appears to be toward far SW Virginia/east Tennessee/northwest NC. The surface air mass at this point across the rnk County Warning Area remains very dry...so it is no likely that any such mesoscale convective system has a great chance of surviving very far eastward into the County Warning Area. By Tue-Wed...the upper ridge continues to build across the region and shunt any potential for mesoscale convective system activity much further north across OH/PA/NY...which would then move east and not southeast into the upper high. However...as a Bermuda surface high sets up with considerable increase in dewpoints and moisture into the region from the Atlantic...expect a marked increase in diurnal/afternoon rain showers/thunderstorms and rain activity induced by differential heating along the alleghanys especially. With all of this in mind...have tailored probability of precipitation to reflect slight chance for mesoscale convective system/baroclinic zone activity late Monday/early Tuesday from south to north...then trended toward almost entirely diurnal mountain focused activity Tuesday afternoon and Wednesday afternoon. At this point...Tuesday afternoon appears to bring the best threat for rain showers/thunderstorms and rain activity...as by Wednesday...upper ridge associated subsidence will tend to suppress activity somewhat. Temperatures will warm noticeably through the period...beginning below normal sun to even above normal by Wednesday. Have used a European model (ecmwf)/GFS MOS model blend...especially during the later periods. && Long term /Wednesday through Friday/... as of 100 PM EDT Friday... The upper trough off the New England coast will move east enough to allow for the start of ridging over the area. However...the northern extent of the ridge will be dampened flat and zonal across the region thanks to a shortwave trough heading southeast through the Ohio Valley. We will start to trend milder...but showers and storms will be in the forecast thanks to the shortwave trough feature through Tuesday. Wednesday through Friday the upper ridge strengthens and temperatures continue their upward trend. By Friday...highs in the upper 80s to around 90 will be common east of the Blue Ridge...with low to middle 80s in the mountains. The highest peaks will be in the upper 70s. && Aviation /12z Saturday through Wednesday/... as of 730 am EDT Saturday... VFR conditions expected to prevail through the taf valid period. Other than some passing cirrus...mainly across the SW half of the forecast area...sky clear should prevail for the most part. No fog noted at any of the rnk taf sites this morning...although just on the other side of the alleghanys...near 0sm visibility in fog for many WV sites. Feel this will stay on that side of the mountains this morning. Will need to watch this more carefully Sun morning given slowly increasing moisture and near 0f T/dew point spread early sun at lwb. Otherwise...VFR visibilities expected through taf valid period. Winds will be gusty again today...but not quite as strong as Friday...as a tight gradient remains in place between the departing low to the NE and the surface high spreading into the Ohio Valley. After 14z...expect west-northwest-northwest winds 12-15kts with gusts 20-25kts at most taf sites...slightly less for lwb. Winds will diminish very quickly after sunset and should become calm at lwb/bcb/lyh/Dan shortly thereafter. High confidence in VFR ceilings through taf valid period. High confidence in VFR visibilities through taf valid period...expect medium confidence lwb after 06z sun. High confidence in wind speed/direction through taf valid period. Extended aviation discussion...moisture increases again next week as the surface high moves east and the upper ridge strengthens over the Mississippi Valley. Will be getting to more humid weather again with scattered thunderstorm threat by Tuesday and fog issues at night in the valleys and especially in any areas that receive rainfall late the day before. && Rnk watches/warnings/advisories... Virginia...freeze warning until 8 am EDT this morning for vaz007-018>020. Frost advisory from 2 am to 8 am EDT Sunday for vaz020. NC...none. WV...freeze warning until 8 am EDT this morning for wvz042>045. Frost advisory from 2 am to 8 am EDT Sunday for wvz044-045. && $$ Synopsis...nf near term...nf short term...rab long term...ds aviation...nf/rab