Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 251010 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 510 AM EST Sat Feb 25 2017 .SYNOPSIS... An intense cold front will cross through the Mid Atlantic region today, triggering showers and thunderstorms and leading in much colder air and strong gusty winds tonight. High pressure will cover much of the eastern United States on Sunday then will move off the southeast coast on Monday. A low pressure system will develop in the southern plains on Monday and track into the Tennessee Valley by Wednesday. && .NEAR TERM /THROUGH TONIGHT/... As of 430 AM EST Saturday... At 4AM a strong cold front extended from Lake Erie to eastern Kentucky to southwest Alabama. A pre-frontal band of showers and thunderstorms was just ahead of the front with the eastern edge of this line just reaching Smyth and Tazwell Counties. Winds will temporarily turn to the west behind the line then resume a southwest direction until the main front comes through. Models were in very close agreement with the timing of the front. Expecting the boundary to move through southeast West Virginia and far southwest Virginia this morning. The front will continue to move east during the day and will be exiting the area east of Danville and Lynchburg between 4PM and 6PM late this afternoon. A general weakening trend is expected in the band of showers and thunderstorms as it crosses the Appalachians then more showers and stronger thunderstorms will redevelop east of the Blue Ridge this afternoon. Temperatures will be in the 50s and 60s ahead of the front and will be falling behind the front. GLAMP and blend of other short range guidance was used for the non-diurnal trend. Between 12Z/7AM this morning and 12Z/7AM Sunday morning 850mb temperatures drop from around +10 to a range of -10 to -2. This strong cold aid advection will combine with decent pressure rises of +5 to +10MB/6hrs to produce gusty winds behind the front. For now do not have any advisory (40kt/46mph)gusts in the forecast but day shift will have a chance to re-evaluate. Threat for higher wind gusts will continue to be highlighted in the Hazardous Weather Outlook. Air mass gets cold enough for snow in the western upslope area of southeast West Virginia after 00Z/7PM. No change needed to snowfall amounts/liquid equivalent based on the latest guidance. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 330 AM EST Saturday... High pressure over eastern Kentucky Sunday morning will move east across the region and push off the Atlantic coast by Sunday night. Gusty westerly winds Sunday morning will diminish Sunday afternoon as the high builds east. High temperatures Sunday will range from the mid 30s in the lower 50s in the Piedmont. Light southwest winds are expected Sunday night under increasing clouds. Low temperatures Sunday night will vary from the mid 20s in the mountains to the mid 30s in the Piedmont. Zonal flow aloft will develop across the CONUS Monday. Southwest winds will result in warm air advection, increasing moisture and threat for showers. Kept the highest pops in the southwest portion of forecast area. High temperatures Monday will warm into the mid 40s in the mountains to near 60 degrees in the southeast. Shortwaves rotating eastward in the upper flow will create the potential for scattered rain showers Monday night. Low temperatures Monday night will generally be from the upper 30s in the northern mountains to the upper 40s in the Piedmont. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 330 AM EST Saturday... Zonal flow will promote warming temperatures for mid week with main focus for precipitation centered around noisy southern stream short wave energy which models are having difficulty timing. Through Wednesday, the region is expected to remain in a deep southwest flow in advance of a developing trough across the Central Plains states. The GFS continues to be more progressive in depicting pieces of energy streaming across the area, each with the potential for additional rounds of precipitation, especially on Wednesday. CAPE is also forecast to peak on Wednesday, and with trough generally forecast to come through during the day this suggest potential for thunderstorms. Since models have not quite nailed down the timing will list the threat as slight chance attm. Cold front will push off the Atlantic coast Wednesday night. The timing is a little slower on ECMWF compared to GFS. Northwest flow upslope rain and snow showers are possible Thursday, supported by both GFS and ECMWF. Drier weather returns for Friday into Saturday. Temperatures will peak by Wednesday followed by lowering numbers for Thursday behind the trough, dry weather and near seasonal temperatures returning Thursday night into Saturday. && .AVIATION /10Z SATURDAY THROUGH WEDNESDAY/... As of 1130 PM EST Friday... Expecting overall VFR to prevail over the next few hours with ocnl MVFR cigs possible with a swath of strato-cu currently traversing southern/central sections. However appears cigs will lower late from west to east as a band of pre-frontal showers heads east into the mountains by daybreak. The biggest challenge will be timing the cold frontal passage west to east across the region tomorrow. Expect fropa early morning at KLWB and KBLF, mid/late morning at KBCB and KROA, then early afternoon KLYH and KDAN. While best dynamic forcing will be shearing off to our north, expect there will still could be isolated thunder with the pre-frontal band of precip so including a brief TEMPO for tsra far west early. Otherwise using prevailing MVFR vsby for a period of showers most spots excluding KDAN where a bit more removed from deeper moisture. Showers and isolated thunderstorms will be east of KLYH and KDAN by 00Z/7PM if not sooner. Winds behind the front become west to northwest and quite gusty as cold air advection generates good downward momentum transfer and the low level wind field amplifies late Saturday through at least midday on Sunday. High pressure will cover the region behind the front for late Sunday into Monday with VFR expected under lighter winds. Extended Aviation Discussion... A warm front is expected to stay near us Monday night into Tuesday keeping a threat of showers around with sub-VFR possible. Another wave of low pressure will likely prolong the sub-VFR conditions with the next round of heavier showers possible on Wednesday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AMS SHORT TERM...KK LONG TERM...KK/PM AVIATION...JH/MBS/RCS

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