Area Forecast Discussion
Issued by NWS Blacksburg, VA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KRNK 191126 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 626 AM EST Mon Feb 19 2018 .SYNOPSIS... A warm front will move north through the region today. Afterwards, a strong ridge will set up off the southeast coast providing much above normal temperatures through the week. && .NEAR TERM /THROUGH TONIGHT/... As of 225 AM EST Monday... Looking at a quick shot of rain this morning, with radar showing best coverage of rain already moving into the mountains of WV and southwest Virginia, with a secondary area moving up toward the Triad of NC. Going with the HRRR/NamNest shows best coverage and lift across our northern forecast area through dawn, with the southern area somewhat less organized. Most will be seeing measurable rain, except perhaps portions of northern NC. Most of the rain exits east after 10am as best lift starts to shift further north along warm front. However, the afternoon will stay somewhat overcast, especially in the piedmont thanks to a weak flow out of the south, and inversion in the low levels keeping clouds around. This will lead to cooler highs, which seems to fit the latest MAV/MET guidance with upper 40s to lower 50s. Further west, enough gradient exists to mix the winds down and clear things out somewhat, but ample southwest flow keeps skies greater than 50 percent coverage for clouds, with best chance of sunshine occurring from midday to mid afternoon in the mountains. This should send temperatures into the upper 50s to mid 60s. Will be a reversal of normal highs in our area, where the piedmont is typically the warmest, it will be the coolest today. Nevertheless, highs will be seasonably cool in the piedmont to 15-20 degrees above normal in the mountains. There will be a small threat of rain/drizzle this afternoon mainly along/east of the Blue Ridge, but depth of moisture is somewhat limited. Tonight, expect a cloudy sky in the piedmont to mostly cloudy west. Appears low levels will stay moist and with some upslope patchy light rain and drizzle along with fog will occur across the Blue Ridge, south of Roanoke into NC, and may stream eastward as the low level flow turns more southwest and increases late. Temperatures will only drop a few degrees from highs today in the piedmont with upper 40s forecast, while the mountains sink back into the mid 40s to around 50, still 15 to 20 degrees warmer than normal. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... As of 330 AM EST Monday... The main highlights in this period are the well above-normal, springlike temperatures forecast along with a generally increasing threat for rain moving into Wednesday and Thursday. Specific to the temperatures, these are some 20 to 30 degrees warmer than climatology. Putting that into context...forecast highs are what we`d consider "normal" around early-mid May, and the lows around late-May to early-June. Daily temperature records are probably in jeopardy of being broken, and could potentially eclipse all-time warmest February minimum temperatures at some of our climate sites. See the Climate AFD section for more details. Synoptic-scale features in mid-levels remain well-specified in this period per 00z NWP, featuring a highly anomalous 2-3 standard deviation above normal ridge centered west of Bermuda and a large trough in the southwest US. This sets up a SW-NE oriented height gradient across the middle of the country which will run approximately parallel to a surface cold front that will be slow to advance east. Its position will also be influenced by poorly defined mid-level shortwaves in the flow that are difficult to time. Confidence on timing rain chances Wednesday into Thursday is rather low given that the front keeps trending slower the past few runs - now more likely into Thursday. Tuesday and Wednesday will be the warmest days in the period, though the better chance at sun will be on Tuesday. Exception is in the southern Blue Ridge Tuesday where areas of mist/fog and limited chances for drizzle or light rain will keep clouds hanging tough through at least the morning hrs. Dry mostly everywhere else with low-70s for highs, except mid/upper 60s in the aforementioned cloud plagued southern Blue Ridge in NC/VA. Though forecast is generally dry except with limited chances for light showers against the southern Blue Ridge, a bit more cloud cover forecast into Tuesday night will keep lows in the middle to upper 50s, mildest in the NC Piedmont/Southside. Dewpoints should be rising all day, into the mid/upper 50s by nighttime. Looking into Wednesday, model guidance continues to show some warm- sector convective showers developing in the early afternoon hours mainly west of the Blue Ridge, in an environment of weak instability (LIs -1, CAPEs about 200 J/kg per SREF mean), seasonably high PWAT values of around 1.2" and otherwise limited forcing/lift. Have kept PoPs toward solid Chance from southeast WV into the New River Valley where guidance is the most bullish on rain chances, but kept PoPs east of the Blue Ridge to no better than 15-25%. With the limited instability, kept afternoon slight chance thunder mention in the forecast from the Mtn Empire northeast into the New River Valley and into southeast WV. Kept highs generally similar to Tuesday given a milder start to the day, but if there`s less cloud cover it`s not out of the question that areas in the Piedmont could more easily reach the mid 70s. Lows Wednesday night are a couple degrees warmer than Tuesday night, into the mid to upper 50s. Possible a few towns in Southside and the NC Piedmont may even stay above 60. Quite impressive. Thursday looks to be when the best chance for rain appears to be, and also tend to be the "coolest" in the period. Clouds and rain should be rather common, tending to begin in areas to the north but then build southward toward NC by afternoon. Shown rain totals of about a tenth to as much as a half inch, greatest furthest north and west. Cooler temperatures may also be driven by indication of northeast flow/CAD building south out of northern VA per the global models. By cool, we`re talking highs in the 60s which are still some 20 degrees milder than normal. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... As of 330 PM EST Sunday... An upper long wave trough over the central/northern Rockies is forecast to move east, flattening the subtropical ridge over the southeast CONUS. This will allow a cold front to potentially stall over or just north of our region. This front will result in an increasing threat for showers, but no snow...temperatures remaining above the seasonal norm. && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
As of 620 AM EST Monday... Most of the rain will be exiting our region by late morning. With the rain, expect MVFR to IFR cigs, and based on latest trends in radar/high-res models, a corridor from LWB-LYH should see the most rain threat until 14-15z. For the rest of the day, low levels stay saturated along/east of the Blue Ridge, stuck under an inversion, and with lack of winds to mix it out, should see most of the taf period stay MVFR or lower through the period, though could see some improvement to VFR. Further west, mainly becoming VFR by late morning/early afternoon west of a LWB/BCB line, with LWB/BCB sometimes improving to VFR, but mostly staying in the MVFR range of 2-3kft. Tonight, appears threat of fog will commence after midnight at all sites but BLF where winds will keep it mixed out. Anticipate mainly 2 to 4sm at all sites, with sub-VFR cigs. Drizzle may also impact ROA/BCB after 09z. Extended Aviation Discussion... High pressure strengthens offshore resulting in a return to overall VFR Tuesday ahead of the next cold front well west of the Appalachians. 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.
-- End Changed Discussion --
&& .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...KK/WP NEAR TERM...WP SHORT TERM...AL LONG TERM...PM AVIATION...AMS/DS/WP CLIMATE...AL is the U.S. government's official web portal to all federal, state and local government web resources and services.