Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 241906 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 306 PM EDT Sat Sep 24 2016 .SYNOPSIS...
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Cold front arrives from the north tonight, moving south into the Carolinas Sunday, before stalling. High pressure following the front will wedge south along the eastern slopes of the mountains Sunday into early Monday. Another cold front will shift in from the west Monday night into Tuesday bringing better chances of showers and isolated thunderstorms for early next week.
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&& .NEAR TERM /THROUGH SUNDAY/...
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As of 230 PM EDT Saturday... A cold front, currentLY over northern Virginia, will edge toward the area this evening then slide to the south into the Carolinas tonight. Low deck clouds will accompany the front with a few prefrontal dark base clouds producing a few sprinkles late this afternoon. Low level flow remains northeasterly which should limit chances for measurable precipitation for the next 24 hours. However, moisture is shallow (under 4 kft), but will remain thick and overcast through the day Sunday. With some weak warm air advection, isentropic lift and flow turning more easterly on Sunday, light rain/drizzle is possible along eastern slopes of the Blue Ridge. As the front moves to the south, cool air and cloudy conditions will keep temperatures on the cool side for the next 24 hours or so. Considering the depth of the wedge is around 3000 to 4000 feet, just about everyone will see cooler than normal temperatures Sunday. Temperatures will only warm into the 70s with eastern slopes likely to stay in the 60s. The Bluefield-Richlands area will be on the western flank of the wedge and could see some erosion in the afternoon. A warm upper level ridge over the southern Mississippi Valley could stretch east into area, allowing southwest Virginia to warm to near 80F.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
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As of 245 PM EDT Saturday... Low level wedge looks to be at its strongest Sunday night into early Monday with the axis of the surface high just east of the mountains aided by continued light rain/drizzle across the west and shortwave ridging aloft. Guidance even suggests that some drier air from the northeast could work into eastern sections during the evening given the strength of the high, allowing for brief clearing before the flow aloft starts to turn more southwest overnight. This should once again propel the shield of low clouds back east by early Monday with lingering low pops for light rain/drizzle espcly Blue Ridge and points west into midday Monday. Lows mostly 50s to lower 60s Sunday night with coolest air over the north/northeast. Wedge should begin to scour out Monday afternoon as ridging aloft flattens in advance of the strong upstream upper trof that will push an associated cold front toward the mountains by late in the day. Models also show quite an increase in moisture depth ahead of the front with PWATS near 2 inches under decent southwest flow aloft. This deepening flow looks to gradually weaken the wedge from west to east by Monday evening although far northeast sections may not see the cool pool exit until overnight when the pre-frontal showers arrive. However does appear to be enough instability and added focus as the warm front lifts north and the pre-frontal lobe enters, to support some low chance thunder mainly south/west late Monday, with more widespread shower coverage progressing east during the overnight. Latest ensembles as well as a mix of the GFS/EC also support a swath of around one half to as much as one inch of qpf espcly central/eastern sections. Therefore running with a period of high chance to low likelys from west to east starting late Monday mountains and out east into early Tuesday. Boundary may slow enough during Tuesday given the stalling nature of the strong upper low to the north, to linger some shower pops eastern sections, with more clearing developing mountains by afternoon. Stayed with cooler highs Monday, 70-75, except perhaps near 80 far west where will exit the wedge sooner. Appears enough cool advection to hold much of the mountains in the 60s to around 70 Tuesday espcly if clouds persist longer, with the east mainly mid 70s pending how soon the showers end.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
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As of 145 PM EDT Saturday... Upper low/trof should push east across the mid-Atlantic during midweek with its associated cold front exiting the region to start the period. However latest model trends suggest a somewhat slower scenario with lots of uncertainty in just how fast this will happen given the slow evolution of this complex upper system to the north. Based on current and still rather progressive model solutions, could still be looking at a few evening showers southeast Tuesday night as the front perhaps slows per added low pressure rippling northeast. Also passing of the center of the 500 mb trof axis/cold pool may also generate a few showers mainly northern/western sections late Wednesday into early Thursday but iffy. Otherwise should see much drier air invade the area as ridging both surface and aloft take control from later Thursday into next weekend. Expect mostly seasonal temps with highs 60s west to 70s east with coolish overnights with some 40s mountains and 50s elsewhere.
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&& .AVIATION /19Z SATURDAY THROUGH THURSDAY/... As of 740 AM EDT Saturday... Backdoor front will bring some scattered to broken altocu later this afternoon. As we head into the evening and flow turns more northeast behind the front, lower cigs will become more common along and east of the Blue Ridge. Will may see patchy drizzle develop along eastern slopes of the Blue Ridge, but given moistures is shallow (under 4000 feet) left out at all sites. Sub VFR expected into Sunday, and possibly Monday with wedge in place. Fog and drizzle or light rain will be possible Sunday night along/east of the Blue Ridge with showers scattered into Monday ahead of a west to east moving front. Extended aviation discussion... A strong, but slow moving, cold front will be approaching the area from the west on early Tuesday. Models have significant differences on the timing and location of this front, but rain chances during the first half of next week will be on the increase. Until the front pushes across, Tuesday, we should stay in a period of sub-VFR at times, especially northeast of a line from LWB-BCB-DAN. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH NEAR TERM...RCS SHORT TERM...JH LONG TERM...JH AVIATION...RCS

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