Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 241515 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1115 AM EDT Tue Apr 24 2018 .SYNOPSIS... Low pressure will slowly move from the Tennessee Valley to the Carolinas today. Prolonged southeast winds will keep the area wet through tonight. As this area of low pressure departs on Wednesday, two additional disturbances look to cross near our area during Thursday and Friday. && .NEAR TERM /THROUGH TONIGHT/... As of 1115 AM EDT Tuesday... A flood watch remains in effect into this afternoon along the southern Blue Ridge. See the hydro discussion below for more details. A deep upper level trough continues to pivot toward North Carolina. Rain is still steadily moving northward, but most of the heavier rainfall appears to be just east of Danville and outside the CWA at this time. The cool wedge with decent northeast flow continues to keep the entire region cloudy and moist. Any chance of thunder this afternoon was removed as the wedge appears firmly entrenched, which will keep instability to the south. High temperatures were tweaked a little downward based on observational trends. The center of the slow moving upper low will traverse east across the forecast area tonight into Wednesday morning. The low to mid level winds just above the surface will become westerly with the passage of the mid level trough. Decreased pops tonight and transition ptype to showers. Low temperatures tonight will vary from the mid 40s in the northwest mountains to the mid 50s in the piedmont. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/... As of 445 AM EDT Tuesday... The slow moving closed upper low will continue to move slowly east and northeast away from the region. Wrap around moisture will linger across much of the area Wednesday with high chance to likely pops continuing across much of the CWA. Additional rainfall amounts being on the back side of the upper low should be manageable and mostly in the 1/2 range or less. Minor flooding may continue in some spots, but do not see any major issues. Meanwhile, a northern stream trough will linger across the Great Lakes through the period while another compact vigorous closed southern stream system moves into the Mid-South and toward the southeast by Thursday. All-in-all conditions will remain cloudy, unsettled, and rather wet during the period. The best chance for rainfall will be Wednesday with the departing upper low and then again late Thursday into Friday with the secondary southern stream upper low. Have just a brief mention of Thursday Wednesday across the NC Piedmont area where instability, shear, SIG SVR parameters appear just enough to support thunder in that area. Nothing severe is expected. The Friday system may also support isolated thunder but have not introduced yet due to lack of instability and southern track of system. Rainfall may become an issue again depending on the exact track of the heaviest rainfall. The GFS suggests that minor flooding would at least be possible, while the NAM and the ECMWF keep rainfall amounts well below FFG and mostly below 1.0 inch. Temperatures will be seasonal normals through the period with 850mb temperatures hovering mostly in the 4C to 6C range yielding high temperatures in the 60s and lows in the 40s. No Arctic or Canadian air masses are foreseen during the period as the upper flow remains largely zonal and the two streams, northern and southern, remain separate and distinct. && .LONG TERM /SATURDAY THROUGH MONDAY/... As of 515 M EDT Tuesday... The closed southern stream upper low will lift off to the northeast during the early part of the weekend leaving weak broad northern stream troughing across the eastern U.S. This cloud leave a fair amount of cloud cover lingering in the mountains, but overall the weekend looks like a big improvement over the weekdays with more sunshine, slightly warmer temperatures into the 60s and 70s, and light winds. Temperatures will start this portion of the forecast a few degrees below normal, but trend milder, especially for Sunday and Monday. By Monday temperatures are forecast to average about five degrees above normal. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/... As of 558 AM EDT Tuesday... Poor flying conditions expected during the taf period with rain and low clouds. The combination of a wedge east of the mountains and increasing isentropic lift will result in periods of rain, heavy at times today. MVFR Cigs will lower to IFR, ISOLD LIFR conditions this morning. With slow motion of the closed low moving out of the Mississippi valley expect rain and IFR conditions to linger into this afternoon. Believe the wedge barrier jet will keep winds a bit gusty at KLYH and KDAN through the period. While the southeasterly low level jet running over the top of the wedge is quite robust, very moist and stable boundary layer conditions will inhibit winds mixing down. The most likely locations for stronger wind gusts will be at the higher elevations in the west to include the airfield at KBLF. The axis of heavy rain will shift eastward today as the low travels east across the region. Medium to low confidence in ceilings, visibilities and winds during the taf period. Extended Aviation Discussion... This afternoon the low will be situated overhead so rainfall may start to fade in the southwest around BLF after 18z then shifting northeast through this evening. Expect sub-VFR through the afternoon, and into Tonight/early Wednesday. Winds turn to the northwest, by late Tonight into Wednesday and allow for the precipitation to trend showery in the west. The weather pattern will remain unsettled Thursday into Friday as a series of disturbances crosses the area, each with the potential for providing showery precipitation and localized sub-VFR conditions. Drier weather expected for Saturday. && .HYDROLOGY... As of 300 AM EDT Tuesday... No changes need to the flood watch, which remains in effect through 400 PM Tuesday. Additional rainfall today of one to three inches possible with isolated amounts over four inches along the southern Blue Ridge from near Meadows of Dan to Blowing Rock. Looks likely that the areas around the Watauga River in NW NC as well as streams flowing off the Blue Ridge are going to need to watched. Ensembles for the rivers are still lagging though the SREF is a bit robust in bringing flooding threats later on to the Dan River, as well as portions of the Greenbrier and New. Other ensembles as well as the RFC are keeping all rives at or below flood stage. Something to watch once we see how much falls, but rises along the main stems, including the New and Dan Rivers are likely, as well as portions of the Roanoke. Given lack of deep convection, flash flooding appears less likely. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...Flood Watch until 4 PM EDT this afternoon for VAZ015>017-032. NC...Flood Watch until 4 PM EDT this afternoon for NCZ001>003-018- 019. WV...None. && $$ SYNOPSIS...KK/PW NEAR TERM...KK/PW SHORT TERM...RAB LONG TERM...DS/RAB AVIATION...KK HYDROLOGY...KK/WP is the U.S. government's official web portal to all federal, state and local government web resources and services.