Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/01/21

Area Forecast Discussion
National Weather Service Lincoln IL
910 PM CDT Wed Mar 31 2021 .SYNOPSIS... Issued at 315 PM CDT Wed Mar 31 2021 Below average temperatures are expected tonight and Thursday, with lows in the 20s and highs in the 40s. Breezy northwest winds will continue tonight and tomorrow. A warming trend will begin Friday and continue into the weekend, and no rain is expected through at least Sunday. && .UPDATE... Issued at 910 PM CDT Wed Mar 31 2021 Some winter-like air will settle into Illinois tonight. The axis of coldest 850mb air temps (-10C to -13C) will be centered from NE to SW across Illinois at 12z/7am Thursday. Steady NW winds at 10-15 mph will continue through the night, but that will not be enough to slow the cooling process like usual. Skies will be clear though the night, helping radiational cooling. Low temps tonight will be firmly down in the mid 20s, with low 20s toward Galesburg to Lacon. No changes are needed to that part of the forecast. Same with the freeze warning in our far SE counties, where some growing has started. && .SHORT TERM...(Tonight through Thursday night) ISSUED AT 315 PM CDT Wed Mar 31 2021 500-mb RAP analysis for this afternoon showed a trough axis over the Great Plains, with a ridge over the West Coast. These features will translate east over the next several days, driving the weather pattern in the process. Below average temperatures are on the way through Thursday night as breezy northwest flow behind yesterday`s cold front ushers in cooler air. Lows tonight and Thur night will be in the 20s. Highs Thursday will be in the mid 40s, which is about 10-15 degrees below normal for late March. A modest pressure gradient over the area tonight will keep winds from becoming calm, resulting in wind chills in the teens. The 500-mb trough axis will sweep through overnight tonight into Thursday. Behind the trough, a broad area of surface high pressure shifts east, moving directly over Illinois by Thursday evening. This will result in clear skies and light winds, allowing for efficient radiational cooling. Low temperatures will again fall into the mid 20s Thursday night. MRCC guidance and discussions with core partners indicate that there is at least some vegetation susceptible to freezing temperatures in the southernmost counties of the ILX CWA, where a freeze warning has been issued for Wednesday night and a freeze watch has been issued for Thursday night. The threat for damaging cold in the southeast appears greatest Thursday night, when several hours of mid 20s temperatures are expected. The entire CWA will experience below freezing temperatures both Wednesday and Thursday night, so regardless of whether or not freeze headlines are in effect, if you do have at-risk vegetation take action to protect it from the cold. .LONG TERM...(Friday through Tuesday) ISSUED AT 315 PM CDT Wed Mar 31 2021 Ridging will persist over the central CONUS from Friday into next week. On Friday, southerly flow returns and initiates the beginning of a warming trend that will continue through the weekend. The return flow will be more robust over the western half of the ILX CWA on Friday, resulting in highs in the mid-50s west of I-55 and near 50 degrees further to the east. Highs will rise into the 60s on Saturday, then the 70s for Sunday and into early next week. Over this period, breezy south to southwesterly winds are expected everyday. Precipitation chances appear few and far between at this time, with dry conditions expected through at least Sunday. There is some chance for precipitation on Monday, however, models have trended further north with this disturbance and it may miss central IL entirely. Additional precip chances exist by the middle of next week, but little detail can be added to the forecast at that range. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 644 PM CDT Wed Mar 31 2021 The strong NW wind gusts to 25-30KT from this afternoon will linger a few hours into the evening, but will generally subside by 03z. It will still remain breezy overnight, as sustained winds continue in the 10-15kt range. Winds will veer to a more northerly direction tomorrow morning, with sustained speeds in the 13-16kt range through the day. VFR conditions are expected to prevail through the period. && .ILX WATCHES/WARNINGS/ADVISORIES... Freeze Warning from 1 AM to 9 AM CDT Thursday for ILZ071>073. Freeze Warning from midnight Thursday night to 9 AM CDT Friday for ILZ071>073. && $$ UPDATE...Shimon SYNOPSIS...Erwin SHORT TERM...Erwin LONG TERM...Erwin AVIATION...Shimon
National Weather Service Jackson KY
1155 PM EDT Wed Mar 31 2021 .UPDATE... Issued at 1155 PM EDT WED MAR 31 2021 At 330z, a few leftover showers, perhaps mixed with a few flakes over at the highest elevations, were exiting far eastern Kentucky. Much drier air, evident in the low-level WV imagery and surface obs, continues to move in from the west. The latest mesoanalysis shows a relative lull in the CAA late this evening before another CAA surge arrives along with a robust vorticity lobe. Dew points south of the Mountain Parkway and east of I-75 remain relatively high, in the mid 30s to around 40. While the incoming airmass is very dry, this lingering low-level moisture combined with some lifting ahead of the vort lobe will probably generate some increased low to mid-level cloud cover. In fact, this already appears to be happening over the Bluegrass, as per the latest satellite trends. The CAMS seem to be underplaying the lingering moisture over eastern Kentucky and thus could be missing the potential for a few flurries late tonight. Have kept mention of flurries and slight chance snow showers through the night over Southeast Kentucky even though the NAMNEST is the only hi-res model showing this potential. UPDATE Issued at 815 PM EDT WED MAR 31 2021 Another round of showers is crossing our area, courtesy the right entrance region of a 120+ knot 300mb jet residing over eastern Kentucky this evening. This jet is leading to strong isentropic ascent over a sloping anafront surface, as evident by the strongly backed flow in the JKL radar base velocity imagery. Some ice pellets have mixed with the rain in some of the more intense precipitation areas, but well above freezing surface temperatures will ensure that this remains a novelty. The HRRR and RAP seem to be handling this activity the best; therefore, the overnight forecast has been adjusted toward those models. The intensity and coverage of the precipitation is expected to increase over the next couple of hours across southeast Kentucky before the best jet dynamics exit to the east. As the anafront advances eastward, expect snow to mix in at elevations above 2,500 feet. While there should be no travel impacts due to the very warm ground temperatures, a quick dusting to an inch of snow cannot be ruled out on grassy and elevated surfaces above about 3,000 to 3,500 feet. Once the steady precipitation exits to the east, some shallow convection will likely continue under the strong CAA regime. Some of the most robust convection could produce a few more snow showers, flurries, and lower elevation sprinkles through the late night hours, mainly for areas south of the Mountain Parkway and east of Jackson where lingering low-level moisture will be greater. && .SHORT TERM...(This evening through Thursday night) Issued at 621 PM EDT WED MAR 31 2021 An amplifying pattern is underway across the CONUS, as a seasonably deep upper level trough is sharpening up from the Great Lakes down through the southern Plains. At the surface, a cold front has made it east of the Appalachians, with high pressure centered near the central Great Basin through the central Plains region. Temperatures across eastern Kentucky have retreated to the 40s, with light precipitation starting to fill back in across the area. The models have maintained good agreement through the short term. The upper level trough will continue to deepen as it swings from the Mississippi Valley to the Eastern Seaboard through early Friday morning. At the surface, high pressure will gradually build in across the Ohio Valley through the period, with northwesterly flow allowing for well below normal temperatures across our area. A passing upper level jet streak will allow for another round of light to occasionally moderate precipitation early this evening across eastern Kentucky. As temperatures fall off, this will change over to snow across the highest elevations of eastern Kentucky, with perhaps 1 to 2 inches seen atop Black Mountain. Warm ground temperatures should prevent much in the way of impacts. Precipitation will diminish to a few flurries/light snow showers overnight. Ongoing cold air advection will allow for lows in and around the 30 degree mark by dawn, so will let the Freeze Warning ride. Short wave energy will swing through on the backside of the departing trough axis Thursday into Thursday night, with colder temperatures continuing to advect in aloft. This will allow for some fairly steep lapse rates of 7 to 7.5C/km across the area during the afternoon, as surface temperatures struggle to reach the 40 degree mark. Expect mostly cloudy skies and some isolated snow shower activity to break out across the area during the day, before diminishing by dusk. Clouds will gradually clear out Thursday night, setting the stage for a hard freeze area-wide, as temperatures dip into the upper teens and lower 20s, likely breaking record lows at Jackson and London. Given the model consistency regarding the expected air mass, have upgraded the Freeze Watch to a Freeze Warning for Thursday night. .LONG TERM...(Friday through Wednesday) Issued at 506 PM EDT WED MAR 31 2021 The majority of the extended remains fairly uneventful. The main element of more significance is the colder temperatures near the beginning of the period. There is pretty good agreement over most of the period up through Sunday. Models depict our area starting out Friday just to the west of a departing trough and sitting under an area of stronger northwesterly flow, helping with the continued advection of a much colder airmass. Broad ridging lies across most of the CONUS going forward through the weekend and into Monday. At the surface, high pressure dominates across our region, providing calm and clear conditions. Temperatures starting off Friday morning will be frigid, getting down in the mid 20s to right around 20 and a Freeze Warning will be in effect to 11 AM. Temperatures moderate going forward but are still chilly Friday night with temperatures getting down into the mid/upper 20s, and even lower in the valleys. However, a headline for this time period specifically has not been done, given the distance into the future and that there are already two headlines out for early Thursday morning and late Thursday night into Friday morning. It will be mentioned in the HWO for now. Temperatures continue to moderate going through the weekend, but Saturday night still looks a bit chilly, especially down in the valleys, and some frost is possible. However, a hard freeze looks unlikely at this point. Moving into early next week, some uncertainty arises as models are not in the best agreement. They are struggling with the evolution of a trough moving towards the Pacific Northwest on Monday. Generally, a northern stream wave splits from this initial trough while a southern stream trough stays behind for a bit over the western U.S. coast. Beyond this general idea, there are some decent discrepancies, particularly with timing. This leads to a lack of confidence in the evolution of any surface features and the sensible weather experienced here. Overall, stayed relatively close to the blended guidance, and kept PoPs out for most of the forecast period. Some PoPs were introduced near the very end of the forecast period as a frontal boundary attempts to move towards the area, but these were limited to a very low slight chance at most. Again, confidence in that part of the forecast is not very high at this point and there exists a decent chance for change. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) ISSUED AT 839 PM EDT WED MAR 31 2021 At 0030z, VFR ceilings were observed across the area except for far eastern Kentucky (ie. KPBX and KSJS) where MVFR conditions were noted due to a passing band of heavier rain showers along a mid-level cold front. While that band should quickly exit to the east by around 1z, allowing for a brief improvement in ceilings over far eastern Kentucky, another band of showers and lower ceilings will likely move through far eastern Kentucky during the 130-330z timeframe. Outside of far eastern Kentucky, showers and virga will diminish from west-to-east through 3z while ceilings remain solidly VFR. As colder air continues to advect in on northwest winds, some flurry or light snow shower activity will be possible later tonight and again on Thursday. Ceilings will generally remain VFR, although some temporary MVFR visibilities will be possible in the more sustained snow showers. Northwest winds of 5 to 8 kts, will turn more gusty by late Thursday morning, as deeper mixing takes place. && .JKL WATCHES/WARNINGS/ADVISORIES... Freeze Warning from 3 AM to 10 AM EDT Thursday for KYZ044- 050>052-058>060-068-069-079-080-083>088-104-106>120. Freeze Warning from 11 PM Thursday to 11 AM EDT Friday for KYZ044-050>052-058>060-068-069-079-080-083>088-104-106>120. && $$ UPDATE...GEERTSON SHORT TERM...GEOGERIAN LONG TERM...HAS AVIATION...GEERTSON/GEOGERIAN