Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 192345 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 645 PM EST Mon Feb 19 2018 .SYNOPSIS... A warm front will lift north of the region overnight and a strong ridge will then set up off the southeast coast providing much above normal temperatures through the week. Chances for rain increase late Wednesday into Thursday. && .NEAR TERM /THROUGH TUESDAY/... As of 640 PM EST Monday... Confidence is increasing for the development of fog overnight, some dense, within the North Carolina foothills, and areas near and along the NC/VA border east to around Martinsville, or perhaps even Danville. At this time, this confidence is being expressed in a more heightened Hazardous Weather Outlook. Additional associated Special Weather Statements will be posted soon. Will hold on any advisories at this time. As of 235 PM EST Monday... The big weather story in the near term (and beyond) is in fact the development of a very big ridge off the southeast U.S. coast which all the global models have been consistently showing with somewhat varying amplitude for at least several days and short- term models now in agreement. WPC model diagnostic discussion favors the EC and EC ensembles for the strength of the ridge which is a little less extreme than the UKMET and CMC but still highly anomalous. Heights more typical of summer with 594 dm heights at h5 building over the Carolinas by midday Tuesday will allow for unusually warm temperatures expected both overnight and Tuesday (see Climate section below for details on possible records). 850 mb temps are near +15C by Tuesday afternoon and with more sun than today would not be surprised if some records highs are at least challenged, although at this point only Bluefield is currently forecast at a record for tomorrow. Overnight lows will not fall off much tonight especially in the east where lingering overcast impedes diurnal cooling. Patchy fog is likely tonight and some very light drizzle possible mainly along the Blue Ridge where ceilings may be quite low at times. Clouds will continue to diminish tomorrow with temps maxing out in upper 60s to low 70s, some 20 to 30 degrees above normal for this date. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 200 PM EST Monday... Surface high pressure over Bermuda and a strong 595 dam upper level ridge just off the East Coast will provide a strong warm air advection pattern for Tuesday night and Wednesday. Meanwhile, a cold front will try to move eastward across the Ohio River Valley. Model guidance continues to show well above normal temperatures for Wednesday that could put records in jeopardy, which are further discussed in the Climate section. The only caveats going against this record warmth are cloud cover and a chance of afternoon showers. A slight threat of a thunderstorm exists over southeast West Virginia, but model soundings reveal quite weak instability with CAPE only reaching 100 to 200 J/kg. The latest GFS solution has a little more cloud and shower coverage than the NAM and ECMWF models. There is a consensus that some morning clouds could linger along the southern Blue Ridge until the afternoon, but temperatures could soar significantly once the clouds break up. The chance of rain will increase during Wednesday night and Thursday as the cold front tries to edge closer. Models portray the upper level ridge slowly flattening and sagging southward, but it will still resist the eastward progression of the cold front. Temperatures should remain well above normal for the middle of February, but highs should run a little cooler for Thursday due to surface high pressure passing over eastern Canada and beginning to wedge southward along the eastern side of the Appalachian Mountains. Eventually, the cold front will fold over and set up as a nearly stationary baroclinic zone over northern Virginia. Thus, this forecast keeps the highest probability of rain north of Interstate 64. Shower coverage should also increase west of Interstate 81 later in the afternoon. With the cool wedge in place by Thursday night, lows should be notably cooler compared to Wednesday night. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 200 PM EST Monday... The cool wedge should weaken as surface high pressure heads offshore on Friday. However, the latest GFS shows a slower weakening trend compared to the ECMWF model. Another area of low pressure will try to develop over the southern Gulf Coast as an upper level trough progresses eastward from the Rocky Mountains. More clouds and chances of rain seem likely for the upcoming weekend as this area of low pressure pushes eastward. Meanwhile, the upper level ridge over the Southeast should finally give way and heads toward Florida. That pattern change should free up the atmospheric flow to allow a cold front passage over the Mid Atlantic toward Sunday night. High pressure should allow drier conditions by Monday. Despite the overall trend of more clouds and rain, temperatures still should remain considerably above normal with no anticipated threat of freezing temperatures. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... As of 630 PM EST Monday... Areas just east of the crest of the Blue Ridge south of roughly Floyd, VA, and locations near the VA/NC border can expect LIFR/IFR conditions overnight, lasting into early Tuesday morning. Light steering winds will help maintain low clouds, fog and drizzle within this region. West and north of this region, VFR/MVFR conditions will be more common through the night, and be the primary conditions as the bulk of the TAF sites. KDAN will have the best chance of sub-MVFR conditions through the night. During the day Tuesday, conditions will be slow to improve near the NC/VA border, while the mountains should trend to VFR fairly quickly. Extended Aviation Discussion... Scattered MVFR showers are expected Wednesday into Thursday with the approach of a cold front. This front lifts back north Friday with continued threat of showers and potential low clouds. && .CLIMATE... As of 330 AM EST Monday... Tuesday and Wednesday will feature well-above normal temperatures that may approach or eclipse daily record highs and daily record high minimum temperatures. It`s also possible that all-time warmest February minimum temperatures could be approached or broken in this period. Following are daily records, as well as the all-time warmest minimum temperatures recorded in the month of February, for our five climate sites with long-established periods of record: Tuesday 2/20/2018 Site MaxT Year HiMin Year BLF 67 2017 48 1994 DAN 74 1971 51 1949 LYH 76 1930 59 1939 ROA 75 1939 54 1971 RNK 69 2017 47 1991 Wednesday 2/21/2018 Site MaxT Year HiMin Year BLF 65 1996 54 1997 DAN 75 2011 55 1953 LYH 75 1930 50 1981 ROA 73 1930 48 1997 RNK 71 1986 49 1953 Warmest HiMin - February: Site HiMin Date BLF 57 Feb 5 2008 DAN 60 Feb 18 2008 LYH 59 Feb 20 1939 ROA 57 Feb 12 1932 RNK 52 Feb 16 1990 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...PC/WP NEAR TERM...DS/PC SHORT TERM...PW LONG TERM...PW AVIATION...DS/PC/WP CLIMATE...AL

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