Area Forecast Discussion
Issued by NWS Blacksburg, VA

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574 FXUS61 KRNK 190715 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 315 AM EDT Tue Sep 19 2017 .SYNOPSIS...
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High pressure will remain over the region the remainder of this week resulting in mainly dry and mild weather during the next few days. Jose should track north, off the east coast today through Tuesday, before sliding just east of New England on Wednesday.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 240 AM EDT Tuesday... Area remains under dry air aloft, per water vapor loop, between Jose passing well offshore and the next upstream axis of deeper moisture associated with a cluster of mid level shortwave energy in the Midwest. Expect this overall trend to continue today as subsidence is maximized espcly east as a drier but weak north/northwest trajectory develops behind the passing Jose. Guidance continues to try and develop shallow convection mountains with heating but convergence looks even weaker this afternoon given less northeast flow. Thus trimmed back going pops to just an isolated shower mention Blue Ridge without any thunder despite slightly higher instability beneath a lingering strong inversion aloft. This mainly in the mid to late afternoon hours when strong heating is maximized. May also be looking at less fog to start the morning per lingering low clouds around which could fill in and delay heating a little longer espcly if fog does develop around dawn. Otherwise appears rather similar to the past few days with low level moisture early fading to afternoon north to south cumulus bands later on. Heating of slightly drier air after a warmer start should also boost highs a bit more today, with some warming aloft west leading to highs 75-82 mountains, and low/mid 80s east. Models show the upstream energy aloft associated with a weak surface cold front to the northwest slowly edging east into western sections by late tonight. However moisture will again be running into subsidence including leftover dry air aloft so expect most showers to fade upon approach into the mountains after loss of heating. This could at least result in more cloud cover which may put a damper on widespread fog late, so only including some patchy coverage in the valleys toward daybreak. Otherwise keeping it mainly clear east to partly cloudy west with only an isolated pop far western ridges late. Lows mainly 55-60 west and 60-65 east pending degree of clouds/fog late.
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&& .SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
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As of 300 AM EDT Tuesday... Our persistent pattern featuring an eastern ridge and western trof will become amplified through the end of the week as a closed low digs into the northwest. While this will provide us with rather uneventful weather through the end of the workweek, it will also open the east coast to effects from tropical systems moving across the Atlantic. Current and future tropical systems will continue to be monitored closely for any potential impacts in our neck of the woods. Capping in the strong ridge aloft will be weakening with time and upstream short wave energy will be undercutting the ridge and moving through the region. Expect the result will be a diurnal pattern for scattered showers/thunderstorms generally along and west of the Blue Ridge, with a trend toward decreasing coverage and drier conditions by Friday as upper support slowly sinks off to the south Expect little change in the temperature regime with a continuation of above normal warmth. Look for highs generally in the low to mid 80s east of the Ridge with mid 70s/near 80 to the west. Lows will generally be in the low to mid 60s east, mid/upper 50s west with some cooler readings in the valleys.
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&& .LONG TERM /SATURDAY THROUGH MONDAY/...
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As of 330 PM EDT Monday... Upper ridge becomes even more dominant in the extended period with a large a dome of high pressure covering the eastern CONUS and extending north into southern Canada right through the weekend. The upper low out west digs even further south into the Great Basin as short-wave energy continues to drop into the long-wave trough. At the same time whatever is left of Jose may be lingering in the western Atlantic with models continuing to struggle with how blocking to the north may affect future movements. Meanwhile, tropical system Maria, likely still a hurricane, will be entering the picture but still well off the southeast coast. Temperatures thought the extended period will remain at about 5F to 10F above mid- to late September climatology and chances for significant precipitation will remain low beneath the strong and persistent ridge.
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&& .AVIATION /07Z TUESDAY THROUGH SATURDAY/... As of 115 AM EDT Tuesday... Bands of low clouds remain mostly along and west of the Blue Ridge late tonight associated with onshore flow and spreading out of residual cumulus from this afternoon. This likely to produce areas of MVFR cigs over the next few hours before diminishing late as the flow starts to turn more north/northwest toward daybreak. Degree of clearing the key for another round of widespread dense fog across the valleys by morning as appears a little more of a gradient out east may preclude to just patchy fog there. Since clouds again look slow to go, have delayed the onset of most fog mountains with more in the way of MVFR developing a couple hours prior to dawn followed by local IFR/LIFR through sunrise. Given a bit more uncertainty plan to include mostly TEMPO groups for the lower cigs/vsbys west while including more MVFR nature in patchy fog east. Some guidance even showing more of a MVFR strato-cu layer expanding overnight before lowering to stratus/fog but iffy. Fog/stratus should burn off around 14z/10A Tuesday, with all sites VFR going into the afternoon under a SCT-BKN cumulus field similar to the past few days. A few isolated showers may develop late in the afternoon, but none should deter flight plans. A weak upper disturbance approaches from the west Tuesday evening which could bring more clouds and added showers and even an isolated storm to far western sections early Tuesday night. Otherwise expecting another round of fog/stratus to redevelop late once any shallow convection ends and clouds diminish by daybreak Wednesday. Extended Aviation Discussion... Overall persistence forecast to prevail for the rest of the upcoming week into the weekend with strengthening high pressure remaining in place between exiting Jose offshore and a weak cold front approaching from the west. This should maintain good flying weather outside of early morning fog/stratus through late next week, with only isolated diurnal showers possible mainly Wednesday and Thursday afternoons as upper level energy slides across. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH NEAR TERM...JH SHORT TERM...MBS LONG TERM...MBS/PC AVIATION...JH/KK/RCS

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