Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 251421 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1021 AM EDT Tue Apr 25 2017 .SYNOPSIS... Low pressure centered over the eastern Carolinas will slowly drift northeast and off the coast by tonight. Today will be the last wet and unsettled weather day before warming and drying begins Wednesday. High pressure will build across the southeastern U.S. for the second half of the week. This will result in a considerable boost to the temperature with above seasonal warmth expected by the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 1021 AM EDT Tuesday... The flood watch was allowed to expire this morning because the widespread heavy rainfall has ended or shifted east of area. A few rounds of moderate rain may still pass across the Southside of Virginia and the Piedmont of North Carolina this morning. Flood warnings remain in effect until 1215 PM EDT for ROCKINGHAM and CASWELL counties. River flood warnings continue today, please refer to latest FLWs and FLSs. The crest of Danville on Dan River at 26.8 would put the river at major flood. Several flood advisories are in effect this morning including Roanoke and Montgomery counties. Surface low was centered over eastern North Carolina this morning with the upper low centered along the SC coast. This almost vertically stacked system will gradually fill and weaken as it drifts off the coast today into tonight. HRRR, Hiresw- arw-east and NAM showed rain tapering off this afternoon from west to east. Made some minor adjustments in pops and weather for late morning into this afternoon. Modified temperatures with the latest surface obs and shaped readings towards the Glamp for late morning into this afternoon. More changes later... As of 500 AM EDT Tuesday... Pronounced cut-off area of low pressure and stream of moisture/rain continues to impact the Mid-Atlantic Region. The actual surface low (998 mb) was centered over eastern North Carolina with the upper low centered along the SC coast. This almost vertically stacked system is expected to gradually fill and weaken as it drifts off the coast later today. However, it will likely take another 24 hours to completely rid its influence. Until then expect another cloudy day with periods of light rain or drizzle. The moderate to heavy rain threat has pretty much come to an end, although can`t rule out an additional quarter to half inch of rainfall south and east of Danville. Will allow the flood watch to expire this morning. River flood warnings will continue for the next day or two along some of the main stem rivers with the greatest impact along the Dan River. Temperatures today will be 5 to 8 degrees warmer than yesterday, nudging 60 in many areas, but still well under where we could be for late April. For tonight, any clearing will set the stage for fog formation. Unless the stratus persists, anticipate development of fog per wet ground, diminishing winds and radiational cooling from the departing mid/upper level cloud cover. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 500 AM EDT Tuesday... The lawn mowers will start humming Wednesday. Anybody that fertilized their lawn prior to this rain event will have a hay field to maintain. Temperatures Wednesday are expected to be a full 15 to 20 degrees warmer with the return of the sun and warming southwest wind flow aloft. An upper level ridge of high pressure is expected to begin building over the southeastern CONUS. This will result in increasing heights and warming thicknesses with 85h temperatures climbing to near +15 deg C Wednesday. This will support surface temperatures well into the 70s, and testing 80 degrees across southside VA and the Piedmont of NC. Temperatures could potentially be a degree or two warmer, but think a lot of this initial surge of warmth will go into latent heating and an attempt to evaporate all of this moisture laying around from the multiday rain event. As we transition into the second half of the week, will have to keep our eyes on a surface trough/front that will play tag with our area late Thursday. A trough of low pressure moving out of the Rockies will spawn an area of low pressure that will track from the central Plains into the upper Mid-West and western Great Lakes Wednesday into Thursday. The associated surface front is forecast to move east, crossing the Ohio/TN valleys Wednesday night, then across the Appalachians on Thursday. The front is expected to weaken with time as it encounters the building ridge of High pressure over the southeast CONUS, so any shower/storm activity associated with the front is expected to cross our CWA in a sub-severe stance with the primary threat for wetting showers across our mountain counties, and little or no impact to areas east of the Blue Ridge. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 530 Am EDT Tuesday... Surface front will exit or wash out across the forecast area Friday. Lingering clouds may knock the temperature down a degree or two Friday, but this will likely be temporary as the Upper Ridge over the southeast CONUS builds stronger for the weekend. Models suggest 85h temperatures will warm into the +16 to +19 degree C range by Saturday. This will likely yield temperatures well above normal with highs in the upper 70s to near 80 in the mountains and mid to upper 80s for the foothills and piedmont. With low level moisture combined with these warm temperatures, this will result in just enough instability for the possibility of isolated to scattered mainly mountain diurnal convection. Models hinting at potential for some warm frontal showers just to our west on Saturday so will need to keep a an eye on that as we get closer. Otherwise, digging trough to the west approaches and models in general agreement that associated cold front approaches late on Monday and should be quite a big stronger than the one late this week. If the front moves through during max heating Monday afternoon will need to watch potential for severe weather as well, and this will be a fairly fast moving system. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/... As of 700 AM EDT Tuesday... Poor flying conditions will persist today as a slow moving upper level cutoff Low slowly meanders across the eastern Carolinas. This Low is forecast to drift northeast and away from the area Wednesday. Until then, expect predominantly low IFR ceilings and areas of rain and drizzle. The tight pressure gradient around the area of low pressure will also result in a strong northeasterly low level jet, which will favor an extended period of low level wind shear, these winds persisting until the low moves off the Mid-Atlantic Coast later today and tonight. Extended Aviation Discussion... Better flying weather is expected for the second half of the week, though another front may bring scattered MVFR showers/storms Thursday afternoon and evening across the mountains. Drier and much warmer weather will return for Friday and Saturday with temperatures much above normal for the weekend. && .HYDROLOGY... As of 600 AM EDT Tuesday.... Rainfall totals since 8AM Friday through this morning were in the 2 to 6 inch range, with the main impact from heavy rainfall roughly south of a line from Bluefield West Virginia to Lynchburg VA. Runoff from this rainfall had resulted in small stream flooding with numerous roads and low water crossings closed due to flooding. Many trees fell due to the saturated ground and several minor rock and mud slides were reported. All of this runoff has now flowed into the rivers where there is ongoing river flood warnings for sections of the Roanoke, and Dan River Basins. The Flood warning for the NEW river has been canceled, the crest now moving downstream and out of the service area. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...PM NEAR TERM...KK/PM SHORT TERM...PM/SK LONG TERM...PM/SK AVIATION...PM HYDROLOGY...PM is the U.S. government's official web portal to all federal, state and local government web resources and services.