Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 231127 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 727 AM EDT Thu Mar 23 2017 .SYNOPSIS... High pressure will move southeast across our region today and slide off the coast tonight into Friday. A warmer southerly flow will develop Friday into the weekend ahead of a slow moving cold front that will approach the region Sunday. A series of upper-level low pressure areas will track across the central and southern U.S. through next week keeping an unsettled weather pattern in place. && .NEAR TERM /THROUGH TONIGHT/... As of 300 AM EDT Thursday... High pressure over western Pennsylvania this morning will move southeast this afternoon and drift east and off the Mid- Atlantic coast tonight into Friday. Cool easterly flow will keep the areas east of the Blue Ridge just as cool as the mountains. High temperatures this afternoon will range from the mid 40 across the northern mountains to lower 50s in the Piedmont. The far western mountains may make a run at the mid to upper 50s. Clear to partly cloudy conditions are expected tonight. A warm front will lift northward into the Ohio Valley late tonight into Friday morning. Any showers associated with the warm advection and warm front will remain to our north. With dry airmass across our region, leaned towards the drier GFS/NAM solutions over the ECMWF which clips the northern edge of Greenbrier and Bath counties with some moisture about 12z Friday. Low temperatures will range from the mid 20s in the northern mountains to the mid 30s in the western mountains. && .SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/... As of 400 AM EDT Thursday... A pattern transition will be underway at the beginning of this period taking us from the predominant northwest flow aloft we have been in for much of March so far to a very active, unsettled zonal flow with numerous embedded southern stream vigorous upper-level lows. This pattern change will bring frequent rain chances to the area, and some thunderstorms as well, along with an extended period of unseasonably warm temperatures. In fact, after Friday morning, we may have seen the last of any freezing temperatures at most locations in the RNK CWA for the rest of March. Looking at the global picture, we can see the support for this pattern as a broad area of low pressure covering much of the Pacific sends a steady stream of disturbances eastward into the U.S. By the same token, this zonal flow will keep the Canadian/Arctic air locked up north and instead supply the U.S. with a steady stream of Pacific-based air masses. Friday will be the transition day as the current area of cold, dry high pressure moves east off the coast allowing a return southerly flow of warm, moist air from the Gulf to evolve across the region. Temperatures will be on the order of 10-15 degrees warmer than what will be seen on Thursday. On Saturday, a short wave ridge across the eastern U.S. will evolve in advance of the first deep upper low to lift out of the Southern Plains. Thus, Saturday will be a warm day with increasing clouds and possibly some late day showers advancing from the Tennessee Valley into far southwest VA or southern WV. The upper low will then take a more northward track into the Ohio Valley and weaken as it encounters the upper ridge along the eastern seaboard. Nonetheless, sufficient forcing, instability, and moisture will exist as this system rotates with a negative tilt into the Ohio Valley, for a good chance of showers across the region Sunday. Therefore, have advertised likely to categorical pops Sunday. Temperatures Sunday will be just a tad cooler thanks to cloud cover and precipitation, but will remain unseasonably mild. The main questions during the period will be QPF for Sunday and thunder chances. With regard to QPF, models are in fairly good agreement that we should see 1/2 to 3/4 inch of rain Sunday with this first system. Instability is meager and dynamics are weakening. Have included a slight chance of thunder in the far western areas where activity from the TN Valley could arrive before weakening. Severe weather does not appear to be an issue with this first system. && .LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 430 AM EDT Thursday... The next in a series of upper-level low pressure areas will move from the Southern Plains into the Tennessee Valley/Central Appalachians late Monday into Tuesday. While this system will again be weakening as it moves toward the western Atlantic upper ridge, it will have somewhat better dynamics and instability to work with than the Sunday system. Therefore, have included a slight chance of thunder for all areas Tuesday afternoon. This still does not look like a severe weather system, but slightly better potential for such than the Sunday system. Rainfall amounts again appear to be in the 1/2 to 3/4 inch range over all with this event. A quieter midweek period appears in order as the next upper- level system deepens and slows as it moves into Texas and an upper ridge amplifies across the eastern U.S. A weak area of high pressure from the Great Lakes filters into the area for midweek. By Friday, this aforementioned system will move into the Mid-Atlantic region as yet another upper-level low pressure area moves from the southwest U.S. into Texas. Temperatures will remain unseasonably mild through the period with no significant intrusions of Canadian air. A slight cooling will be noted midweek, but temperatures will still be left above normal. Look for maximum temperatures much of the week in the 60s west to the 70s east, with lows mainly in the 40s and 50s. && .AVIATION /11Z THURSDAY THROUGH MONDAY/...
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As of 720 AM EDT Thursday... VFR conditions will continue through the TAF valid period as a large area of Canadian high pressure drifts across the region, then moves off the east coast Friday. Mid-level warm advection will result in an increase in mid/high clouds after 06Z, otherwise just looking for SCT cirrus through the day today. Visibility will be VFR through the period with no fog development. Winds will veer around from the northeast to the southeast through the period at speeds of 4-7kts, generally less after 00Z. High confidence in ceilings and visibilities through the TAF valid period. Medium to high confidence in wind speed/direction through the TAF valid period. Extended Aviation Discussion... Good flying weather is expected to linger into Friday night before moisture starts to increase over the weekend ahead of an upper- level low pressure area moving northeast from the Southern Plains. Precipitation is not expected until Sunday when sub- VFR conditions become more of a possibility. Otherwise looking at overall VFR to start the weekend with most lower cigs remaining west of the area until later Sunday at this point. Periods of unsettled weather will continue into the first half of next week as a series of upper-level lows track from west to east across the U.S.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...KK NEAR TERM...KK/RCS SHORT TERM...RAB LONG TERM...PM/RAB AVIATION...KK/RAB

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