Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/26/22

Area Forecast Discussion
National Weather Service La Crosse WI
647 PM CST Sun Dec 25 2022 .DISCUSSION...(This evening through Sunday) Issued at 300 PM CST Sun Dec 25 2022 Key Messages: - A quick-hitting round of snow tonight, mainly for areas along and west of the Mississippi River. A total of 1-3 inches expected, which will lead to slick travel conditions. - Warm-up in the offering starting Tuesday--highs in the 30s by Wednesday and even low 40s for Thursday! - Additional rain/snow late in the week still possible. TONIGHT: Snow, mainly west of the Mississippi River A well-advertised Alberta Clipper is on its way to affect the region this evening and overnight. Extrapolation of current radar and surface observation trends has the leading band of snow crossing I-35 around 4 pm, reaching the Highway 63 corridor by 6pm, and the Mississippi River before 8pm. The bulk of the snow should fall before midnight in conjunction with the strongest isentropic ascent/Fgen forcing, with kinematic lift ahead of the upper tropospheric trough axis fueling light snow up until sunrise, ending from north to south as the trough axis swings through. The one aspect of this forecast that still presents a degree of uncertainty is snowfall amounts. Two factors drive this issue, the degree of forcing through a very deep dendritic growth zone (8-12 kft deep) and the influx of dry air on the east flank of the system. The short-term guidance has been steadfast in the frontogenesis lift waning this evening as the WAA wing of the snow moves through, but the HREF/GEFS/EPS has underperformed on the snow up in the Dakotas, where visibilities fell to a quarter of a mile and snow reports of 3-5 inches have reported. Dprog/Dt trends with the HREF show that the probability of >1" of snow rapidly increased over the Dakotas right as the storm arrived compared to the previous two runs. The snow has struggled to push east of a Crookston, MN to Mankato, MN line today, slower than previously forecast and a signal that the dry lower troposphere is eroding the front edge of the snow band. This may limit how far east snow advances across the forecast area, especially east of the Mississippi River. The latest HRRR runs are reflective of these observations, keeping a very sharp snowfall gradient along a Winona, MN to Wisconsin Dells, WI line. Overall changes to the forecast have been minimal. Have pushed snow ratios to 20:1 throughout the forecast area given the anomalously deep DGZ. Have also increased QPF values after midnight as the system pivots over southern Minnesota, increasing the residence time of the light snow west of the Mississippi River. This raises snow amounts to 2.5-3 inches west of a line from Rochester, MN to Guttenberg, IA. Would not be surprised to see some 3+ inch reports if the forcing is any stronger than progged. Have issued a winter weather advisory to cover the threat. MONDAY - WEDNESDAY: Warming Up! Monday will be the last cold day of the stretch as strong southerly flow ensues behind the passage of a surface high pressure ridge Monday night. We will see a steady increase in temperatures over the next 36 hours with highs in the mid-20s Tuesday afternoon and lows plateauing Tuesday night. By Wednesday, with a +6 to +9 C warm nose working into the region, highs in the low to mid 30s are looking to be a good bet. A northern stream wave passes north of the region and may bring periods of clouds, but little in the way of impactful weather is forecast. THURSDAY - SATURDAY: Warm, rain/snow possible Longwave troughing sets up along the West Coast by Thursday morning and persists through the end of the forecast period. A lead shortwave ejects from the base of the trough Thursday or Friday, though the bulk of the guidance is coming in drier for PoPs with forecast soundings showing low stratus/drizzle across the warm sector south of the warm front. Given that forecast dewpoints would push into the 30s, an advection fog event may develop Thursday and Friday, which may result in lower highs than currently forecast. The deterministic progs still show a stronger system coming out Friday into Sunday as the parent longwave trough lifts northeastward, but ample variability in the location of the system and whether or not it even impacts the area keeps us in a holding pattern for ascertaining any further details. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 647 PM CST Sun Dec 25 2022 Snow will continue moving into the local area this evening, bringing in low MVFR to IFR conditions consistent with current upstream observations. However, short periods of LIFR conditions could be possible within heavier snow. Model guidance suggests there will be a tight gradient in snowfall, with some uncertainty on how far east the snow band may reach. This will have impacts on restrictions at KLSE, with a shift further east bringing a higher likelihood for IFR conditions and further west possibly keeping restrictions higher than currently forecast. Will continue to monitor trends and make updates as necessary. Behind this system VFR conditions are expected to prevail, with south winds becoming more north/northwest through the day Monday /around 10kts or less/. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...Winter Weather Advisory until 3 AM CST Monday for MNZ086-094-095. IA...Winter Weather Advisory until 6 AM CST Monday for IAZ008>010-018- 019-029-030. && $$ DISCUSSION...Skow AVIATION...EMS
Area Forecast Discussion
National Weather Service Goodland KS
735 PM MST Sun Dec 25 2022 .UPDATE... Issued at 735 PM MST Sun Dec 25 2022 00z NAM, RAP and HRRR all show moisture in the 850-500mb layer increasing through about 09z from Flagler to Tribune and Leoti. A 140-150kt upper level jet moves over this area supporting at least slight chance pops for rain showers and snow showers. Low temperatures through about sunrise are expected to be in the middle 20s to lower 30s. On Monday, another weaker shot of arctic air backs into the area, slowly moving away during the afternoon. We`ll have another wide range in high temperatures with middle 20s to around 30 from McCook to Hill City east, middle to upper 40s across Kit Carson and Cheyenne counties in Colorado. We`ll also have some stratus to deal with which will impact the hourly temperatures for those sites its over. && .SHORT TERM...(This evening through Thursday Morning) Issued at 153 PM MST Sun Dec 25 2022 Ridging over the west and a westerly component to the wind is allowing temperatures to warm nicely into the 40s and mid 50s. The exceptions being east areas which are just now making it above freezing as the linger impacts of the arctic air mass remain along with cloud cover. Winds will begin to turn northerly into the evening as a clipper system moves into the area. Water vapor imagery clearly shows the system as it rides down the east periphery of the ridge. Sprinkles/virga will be common early as RAP soundings show dry low levels but fully anticipate this to saturate into the early evening. Rain is expected to be the primary precipitation with this system with the better chances lying to the east; with some filling into the northwest as the evening progresses which may see some snow briefly mix in. Not expecting much in precipitation wise as few hundredths are currently forecast due to the amount of time it takes to saturate the low levels and the quick moving nature of the system. Monday, will be a bit trickier temperature wise to the west as the clipper system will bring in some colder temperatures with it. I wound up cooling western areas a few degrees as the RAP/NAM/ECMWF all indicate the freezing line extending just west of the Kansas/Colorado state line through 18Z. High temperatures look to range from the upper 20s to the east to the mid 40s west, although the west may be a few degrees cooler depending on the final track. Into Monday afternoon winds will again become westerly allowing the downsloping winds again to rapidly warm temperatures into west Kansas as the clipper system moves away from the area. Low temperatures into Tuesday morning are forecast in the low 20s east to upper 20s west. Tuesday and Wednesday will again be warm due to southwesterly flow ahead of a trough over the western CONUS. Some model data continues to show some locales approaching 70 degrees Tuesday, given the time of the year having a hard time bumping temperatures up more than the 50th percentile currently. High temperatures Wednesday will again be well above average in the low 50s to low 60s. During the day Wednesday, the above mentioned trough moves into the area bringing the next chance of precipitation. Based on the current track it appears that the NW portion of the area will have the relative best chance of precipitation. 850mb temperatures aren`t overly cold with this system with them averaging just around freezing. Current expectations are for a rain/snow mix with perhaps some freezing rain mixing in as forecast soundings over Yuma County do show a warm nose being present. Low temperatures into Thursday morning are forecasted from the low 20s to perhaps the low 30s over the east. .LONG TERM...(Thursday through Sunday) Issued at 132 PM MST Sun Dec 25 2022 A progressive pattern will be in place across the CONUS during the long term period. Several fast moving shortwave troughs are forecast to move through the area. Precipitation chances appear to be low through most of the week, with perhaps a stronger system set to impact the area late in the weekend or early next week. Temperatures will be near or slightly above normal with highs in the 40s and 50s and lows in the 20s. If any precipitation were to occur, it would be light rain during the day and perhaps a light wintry mix of rain/freezing rain/snow at night. Confidence in any precipitation materializing before Sunday is low. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 328 PM MST Sun Dec 25 2022 An area of rain has developed and is moving to the SE. Some uncertainty remains if it will impact the KGLD terminal so opted for VCSH. Upstream observations has shown sporadic drops in ceiling to MVFR in the heaviest areas of rain, so went for low end VFR ceilings for KMCK. LLWS will become of a concern around 06Z as the effects of a quick moving Clipper system affects the area. Winds will rapidly become southerly during the early afternoon at KGLD as the system moves away. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ UPDATE...99 SHORT TERM...Trigg LONG TERM...024 AVIATION...Trigg
Area Forecast Discussion
National Weather Service Lincoln IL
905 PM CST Sun Dec 25 2022 .SYNOPSIS... Issued at 256 PM CST Sun Dec 25 2022 A clipper system will bring central Illinois a quick inch or two of snow Sunday night into Monday. A ridge of upper level high pressure building in to the region from the west will result in warming temperatures through the end of the work week, when parts of the area could experience temperatures in the 60s. Chances for rain increase by Friday and Saturday ahead of the next system. && .UPDATE... Issued at 905 PM CST Sun Dec 25 2022 Evening upper air analysis and water vapor imagery indicated a mid level circulation over southwest MN, with an attendant 1012 mb surface low over far NW IA. Radar returns ahead of the clipper have already progressed east of the IL River, though the initial round of lift in the warm advection sector is working to moisten the dry low levels as noted on 00z KDVN/KILX soundings. Light snow was reported in Galesburg within the last half hour, with more substantial snow located over southeast IA where visibilities around 1 mile were reported. The light snow will spread southeast across the CWA overnight, with accumulations around an inch or less for most areas. After the first round of lift pushes through, will need to monitor potential for light freezing drizzle as deeper saturation is lost especially over west central IL late tonight. A few freezing drizzle obs have been reported over southern IA this evening. As the surface low tracks into west central IL after daybreak, a band of frontogenesis north of the low will bring another round of light snow to the northern CWA, which will drop southeast across the region during the afternoon. Any accumulations will be light, again around an inch or less. Will continue to highlight impacts of light snow with Special Weather Statement product. Only a few tweaks were made to the forecast, nudging low temperatures up a degree or two, and refining PoP timing based on latest trends. && .SHORT TERM...(Through Monday night) ISSUED AT 247 PM CST Sun Dec 25 2022 Truly, there`s only one forecast concern in the short-term, and that is the clipper system coming in from the northwest. The deterministic GFS, ECMWF, CMC, and NAM all show a 500mb vort max drifting southeast from the northern Plains into IA/IL/MO between this evening and around noon Monday. HREF forecasts negative omega at 700mb by 9 PM, GFS suggests Q-vector convergence in the 850-300mb layer by midnight tonight, and NAM and RAP forecast soundings suggest more saturation in the dendritic growth zone compared to what they forecast yesterday, so support for frozen precipitation is looking promising. The upper feature is forecast to slowly weaken as it crosses our area though, so snowfall amounts could be a little lower than what folks upstream see. The HREF suggests precipitation totals from this event will be generally in the 0.10-0.15" range, highest in our north and southeast CWA. NBM v4.1 has trended downward, and suggests around a 30% chance for >1" of snow by 12z Tuesday morning for most of the CWA, while the probabilities are higher (around 50-60%) south of I-70. The probability for more than 2" from NBM is around 5% to 15%, again maximized south of I-70. For now, we`ve decided against issuing an Advisory given (1) the bulk of the snow will fall overnight when hopefully few folks are traveling and (2) accumulations are expected to fall so shy of Advisory criteria (3"). As far as timing goes, we heavily relied on high resolution ensemble guidance. HREF suggests precipitation will begin to creep into our NW CWA around 7 to 8 PM and reach Peoria shortly thereafter. The CAMs suggest the heaviest snow rates with this initial wave will be across our northern counties between roughly 9 PM and midnight, and across our southeast counties between 2 and 6 AM tomorrow morning. Precipitation rates to around 1mm/hr (snow rate ~0.5"/hr, based on forecast snow ratios) are expected south of I-72 with this activity. The second round late Monday morning into the early afternoon will be less widespread with the lack of large-scale forcing, but beneath the upper feature during this time isolated snow showers will produce some brief additional accumulations of perhaps another half inch in spots. The other big weather story will be the warmer temperatures tomorrow. NBM even suggests a 65% chance that high temperatures will reach the 30s tomorrow in Lawrenceville. .LONG TERM...(Tuesday through Sunday) ISSUED AT 247 PM CST Sun Dec 25 2022 Cluster analysis suggests ensemble consensus is for a ridge to be situated over the western and central Great Plains and a trough across the Ohio Valley at the start of the extended period, with some uncertainty developing by Wednesday and especially Thursday in the rate of eastward translation of the ridge. At this time, it appears the EC ensemble is on the whole the slowest of the three extended-period ensembles, with over 1/3 of its members comprising the most amplified Thursday 500hPa height cluster; meanwhile, the CMC ensemble is the primary driver of the fastest cluster, which has the ridge axis shifting into the northeast and a trough developing in the Plains by Thursday. The slower and slightly more amplified solution favored by the EPS would mean a longer period of warming for our area, while the more progressive solution depicted by the cluster dominated by the CMCE would suggest warming would be maximized across the mid Atlantic while our section of the country remains cooler. All three deterministic models have a surface low developing and riding northeastward along the western periphery of the ridge as it slides east of the region at the end of the week, though there`s been a tremendous lack of both run-to-run and model-to-model consistency with the location and strength of this low. Some grand ensemble members even have a few hundred J/kg of CAPE overspreading central IL during this time period, but confidence is fairly low in thunder potential. Confidence is higher, however, in precipitation targeting our area by late week. Every member of both the EPS and GEFS has some amount of precipitation in Lawrenceville at some point Friday through Sunday, and several GEFS members have more than 2" of QPF there by the time it`s all done. At this time, the means of all three extended ensembles suggest most of the precipitation will fall south of our area, though if the system were to shift in its track our area could get in on those heavier amounts. Fortunately, precipitation type is not a concern during this period, as temperatures will be far too warm for wintry weather. NBM suggests a 30% chance for max temps equal to or greater than 60F in Springfield on Thursday, with above average temperatures likely to continue through at least the first half of the weekend. Depending on the track and strength of the low, and hence the location and strength of warm air advection ahead of it, temperatures could wind up way on the warm side of NBM`s distribution and forecast changes may be warranted. For now, though, we`ll let it ride given lack of confidence in the upper pattern and surface low. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 522 PM CST Sun Dec 25 2022 An Alberta clipper low pressure system will track southeast across the region over the next 24 hours. This will spread -SN and MVFR ceilings and visibilities over the terminals tonight. Some IFR visibilities are possible at times in the more intense areas of snow. Ceilings are forecast to lower to IFR around 13-14z, before rising back to MVFR later in the afternoon. Periods of -SN should gradually diminish during the afternoon. With the center of low pressure passing just southwest of the terminals, winds will gradually back from southwest this evening to northwest Monday afternoon, all near/under 10 kt. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...25 SYNOPSIS...Bumgardner SHORT TERM...Bumgardner LONG TERM...Bumgardner AVIATION...25
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
537 PM CST Sun Dec 25 2022 .UPDATE... Issued at 507 PM CST Sun Dec 25 2022 Regional radar reflectivity shows the first wave of snow with an incoming clipper system entering far northwest Missouri at this hour. While echos extend further south/east, observations do not report any precipitation given very dry low-levels. However, more recent observations show wetbulbing (decreasing temperature, increasing dew point) is occurring and will likely allow for light snow to begin in the northern CWA in the next few hours. No changes to the general timing for snow onset tonight. While accumulations will be on the light side, any snow will stick to the cold pavement and cause slick roadways. The potential remains for a brief window of freezing drizzle tomorrow morning on the back side of this wave, when DGZ relative humidity drops below 50% within the system`s dry slot and the low levels remain saturated. However, lift in that saturated, sub-freezing layer is very weak if existent according to RAP soundings. Cloud ice is quickly re- introduced aloft when the upper-level low passes overhead, making the window for any ice very narrow. The best chances for any freezing drizzle exist across the Ozarks, where the DGZ remains drier for a longer period of time. MRB && .SHORT TERM... (Through Late Monday Night) Issued at 302 PM CST Sun Dec 25 2022 Key Short Term Message: The most pressing item of interest in the short term period continues to be the potential for accumulating snow between late this evening and late tomorrow afternoon. Confidence remains high that light snow accumulations will occur across much of the area during this period, but latest guidance continues to suggest that snow accumulations will remain light. In the meantime, it has been a chilly but otherwise quiet Christmas day throughout the area, as well below normal temperatures remain firmly in place throughout the region. Considering that temperatures have not even approached the freezing mark since the last accumulating snow, very little of it has melted yet, and several locations woke to a white Christmas this morning (1" of snow depth or more). While quiet weather will persist for at least several more hours, increasing high level cloud cover is hinting at the approach of a fast moving shortwave from the northwest, one that is almost certain to bring another round of widespread but generally light accumulating snow to the region. While there have been some minor tweaks to the forecast this afternoon, the main points remain largely the same, with confidence gradually increasing in the potential snow amounts across the region. Beginning late this evening, perhaps as early as 7 or 8 PM across northeast Missouri, light snow is expected to encroach upon the area from the northwest, driven largely by isentropic ascent ahead of the approaching shortwave. In spite of modest warm air advection, temperature profiles all resoundingly support snow as the precipitation type, with a healthy portion of the profile at least initially within the dendritic growth zone. However, this initial round of snow is expected to be rather progressive and will likely sweep through almost the entire area before sunrise tomorrow. Considering both this and the modest forcing mechanism and modest moisture available (typical of clipper systems), QPF amounts continue to look rather low. As such, in spite of moderate to high snow/liquid ratios, total snow accumulations are expected to be generally light. On the other hand, the combination of at least moderate snowfall rates for a brief period (2-3 hours), and cold ground temperatures will allow snow to readily stick to pavement quickly overnight tonight, potentially creating slick roads for at least a short period. This will be especially true where surfaces are untreated. As this initial round of WAA snow moves southeast of the area, drying aloft will likely strip away much of the available cloud ice, and most of the snow will dissipate for at least a brief period. At this point, model forecast sounding profiles suggest that a brief period of light freezing drizzle will be possible in some areas, particularly across the Ozarks. Any freezing drizzle that manages to develop would likely be of short duration and low intensity, meaning that any accumulations would likely be restricted to very light amounts on elevated surfaces. Sometime between late tomorrow morning and late afternoon, the surface low will finally move through the area, bringing with it another round of light snow that will likely add to the already existing accumulations in some areas. However, neither the coverage or intensity of this second round of snow is likely to match the previous round, and temperatures are likely to be much closer to the freezing mark. As such, while this additional snow may push accumulations close to the high end of our forecast range, particularly across far eastern Missouri and western Illinois, we don`t anticipate significant impacts from this additional snow. In summary, light snow accumulations remain likely across much of the area, spread out across roughly 24 hours but falling within roughly two concentrated periods overnight tonight and during the day tomorrow. The 10-90th percentiles representing the "best" and "worst" case scenarios remain generally between a light dusting and roughly 2 inches, respectively, with a slight preference for the higher totals across eastern Missouri and western Illinois where the surface low remains most likely to track. Still there remains a bit of uncertainty regarding this last point, as a slight change in the track if the low would likely impact the location of the highest snow totals. Meanwhile, impacts are expected to be minimal from freezing drizzle at this point, but will continue to be monitored. At this time, this event does not look significant enough to warrant the issuance of a Winter Weather Advisory locally, but considering the expected holiday travelers and the relative ease with which snow will stick to roads, at least some marginal impacts are expected. BRC .LONG TERM... (Tuesday through Next Sunday) Issued at 302 PM CST Sun Dec 25 2022 Key Long Term Message: A significant warming trend remains nearly certain during the middle of the week, while widespread soaking rain remains very likely from late Thursday through the end of the week. The last of the snow will subside by Monday evening as cold, dry air fills in behind the departing shortwave. While this parting shot of cold air will lead to a chilly Tuesday morning in the teens and high single digits, it will be the last such morning for the foreseeable future. That is because a significant warming trend is on the way next week, driven by a wholesale pattern change across the lower-48. As tomorrow`s system kicks out to the east, a longwave ridge will build in earnest across the central U.S. Tuesday, and eventually shift east of the Mississippi river by Wednesday. Likewise, a longwave trough will develop across the western U.S., placing the Mississippi Valley region within a regime of southwest flow aloft that will persist through the end of the week. This upper flow pattern will allow for two things to occur. First, the combination of building heights aloft and robust southerly flow will bring a significant warming trend to the region beginning Tuesday and kicking into high gear Wednesday and Thursday. While afternoon temperatures Tuesday will likely still be 5 to 10 degrees below normal, by Wednesday temperatures will jump 15 to 20 degrees to around 5 to 10 degrees ABOVE normal. This continues even further into Thursday, with temperatures expected to climb into the 60s. This is also supported by very narrow temperature spreads among ensemble guidance, leading to a high confidence forecast for this mid-week warmup. Secondly, the persistence of southwesterly flow aloft and the northward transport of Gulf moisture will bring about the return of widespread rainfall over the latter half of the week, beginning with the passage of a shortwave late Thursday. While there remains a non- trivial amount of spread among ensemble members, confidence is very high that widespread rainfall will occur across much of the area between late Thursday and late Saturday, with a slight preference for the eastern half of Missouri and much of Illinois. While there will very likely be dry periods within this window, the more specific timing details within this period remain highly uncertain. The same applies to potential amounts, but considering the potential for multiple rounds of rainfall and high precipitable water content (~90th percentile), soaking rain is very likely for a large portion of the region. BRC && .AVIATION... (For the 00z TAFs through 00z Monday Evening) Issued at 507 PM CST Sun Dec 25 2022 VFR conditions will give way to MVFR ceilings areawide overnight as a clipper system brings snow to the region. Brief instances of VSBY reductions down to IFR are likely with the main band of snow at KUIN and the St. Louis metropolitan terminals overnight. There will be a definitive break in the precipitation during the morning on Monday, however another bout of light snow is possible at the St. Louis terminals during the afternoon with the passage of the upper-level and surface low. It appears that, other than the pre- existing MVFR CIGs and a wind shift to the northwest, there will be no other notable impacts with this final round of precipitation. CIGs will likely begin to improve during the late evening on Monday beyond the current TAF period. MRB && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Marquette MI
719 PM EST Sun Dec 25 2022 .SHORT TERM...(This evening through Monday) Issued at 236 PM EST SUN DEC 25 2022 Water vapor imagery and RAP analysis show a deep mid-level low centered just e of James Bay. At the sfc, weakening 983mb low is colocated with the mid-level low. With the system slowly moving farther away and weakening, winds are slowly gradually relaxing across Lake Superior and Upper MI this afternoon. Out on the lake, winds are still gusting to around 35kt across the central and e, but should diminish blo gales in the next hr or two. KMQT radar still shows several moderate LES bands from Munising area eastward, but reflectivities within these bands are weakening and the bands are becoming more spaced apart due to the increasing influence of ridging/drier air from north and west of Lake Superior. Northwest winds will continue to gradually weaken into this evening and expect LES bands to continue weakening as well over the nw snow belts. As for headlines, only the eastern zones of Alger, northern Schoolcraft and Luce have a winter weather advisory headline thru 00Z and that still looks reasonable. Don`t think the evening shift will need to extend that headline based on radar trends, webcams and fcst model soundings. .LONG TERM...(Tonight through Sunday) Issued at 218 PM EST SUN DEC 25 2022 Father Christmas` gift to da Yoop is a much quieter period of weather tonight and into this coming week across the forecast area then the past few days. Continued lake effect snow showers are expected through Monday night. More widespread coverage of showers is expected across the east. Overall, accumulations should be on the light side, generally 1-3 inches of fluffy snow with a couple areas potentially seeing a little more in the east. A weak shortwave moving through the region Monday night may support a synoptic uptick of snow showers in the east for a few hours, but guidance pushes these bands offshore through the night as the next system drifts toward the Upper Great Lakes and southwest flow develops. Warm front associated with a system approaching the Upper Great Lakes will lift into the forecast area Tuesday. 0z determinstic`s differed on where the better forcings will line up, and the 12z appears to be honing in on a potential solution. Its possible the forecast area could see a wave of moderate wetter snow Tuesday evening, with the best chances for impacts being in the eastern U.P. Guidance suggests the frontal boundary could stall in the vicinity as another low dissipates to our southwest. At this point, a majority of the solutions suggest the boundary would settle over northern Lake Superior or Ontario, suggesting continued WAA ahead of the next low moving into the region toward the end of the week. This low is progged to lift northeastward through the region Thursday night. GEFS, GEPS, and EPS membership haven`t really honed in on where the low will track, but the ensemble means of each suggest the low may end up tracking near the Arrowhead. This would put us within the warm sector of the system, suggesting that rain or a wintry mix would be the dominate precip type Thursday and Friday. Another low looks to follow into the Great Lakes the Saturday/Sunday time period, which could impact New Year`s Eve and Day holiday plans. Similarly to the preceding low, there`s still a good bit of spread of where the low could track and potential outcomes. However, much like the preceding system, there appears to be a potential for rain or a wintry mix being the predominate precip type if it moves through the region. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 719 PM EST SUN DEC 25 2022 There has been improvement from IFR to MVFR, but MVFR ceilings will persist through tomorrow morning at all TAF sites in nw flow. However, the snow and gusty winds have diminished with 12 to 15 kt sustained speeds only continuing through Mon 03Z at KIWD and KCMX. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 218 PM EST SUN DEC 25 2022 Vessel observations from those exiting the Duluth Harbor this morning were mainly ~20kt winds while observations elsewhere were still blowing 35-50kts. By early afternoon most sites were either below gale or below 40kts. Expecting continued diminishment of the winds for the remainder of the afternoon and into next week. By Monday morning, 10m winds lake-wide are expected to be 25kts or less. Expecting these light winds to persist until Monday night, when southwesterly and westerly winds increase ahead of the next system. Guidance continues to suggest a winds ~30kts and some low end gale gusts are expected by Tuesday afternoon, mainly across the eastern half. As winds continue to improve today, the colder airmass overhead should persist until southwest flow develops late Monday night/Tuesday. This should support improving ice accretion rates across the lake through this period. With this said though, isolated heavy and more widespread moderate freezing spray potential can`t be ruled out today/tonight. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Voss LONG TERM...JTP AVIATION...TDUD MARINE...JTP
Area Forecast Discussion
National Weather Service Nashville TN
831 PM CST Sun Dec 25 2022 ...New UPDATE... .UPDATE... Issued at 822 PM CST Sun Dec 25 2022 A few of the latest incoming models have amped up the snowfall in our northwest for tomorrow. Light snow accumulation could occur in that area as early as the pre dawn hours. Went ahead and updated the SPS and HWO to hit this a little harder. Latest grid updates suggest snowfall amounts for Monday of three quarters of an inch for our northwest...a dusting for our far south...and one half inch amounts possible elsewhere. Otherwise, the latest grids look to be in good shape. Current pops do reach 40% for Stewart county just prior to 12Z. As mentioned earlier, updated the HWO and SPS to hit this situation a little harder. Hrrr and Nam nest have ticked upward with those northwest snow amounts. Will advise midnight shift to examine the latest out of WPC and issue an advisory if necessary. && .SHORT TERM... (This afternoon through Monday Night) Issued at 246 PM CST Sun Dec 25 2022 Mid state will continue to remain dry through evening hours tonight. Quick clipper type of storm system will move across our area late tonight into Monday. It should bring some accumulating snowfall amounts with highest amounts of around one quarter to around one half of an inch for locations north of I-40, especially for those locations west of I-24. Temperatures look like they will finally climb above freezing on Monday. A change over to rain showers could be possible for locations around and west of I-65 Corridor during the late afternoon hours. As temperatures once again go below freezing, isolated snow showers should continue into evening hours before tapering off from southwest to northeast as an upper level trough passage follows behind this upper level disturbance. Lows tonight will be warmer than those last night mainly spanning mid teens. Highs on Monday should rise into low to mid 30s west of Cumberland Plateau Region with temperatures across Plateau still slightly below freezing. Although continued seasonably cold lows expected Monday night, the slight warming trend will continue with lows mainly around 20 to lower 20s. A special weather statement was issued earlier this afternoon to provide additional details on this potential of accumulating snowfall across our area late tonight into Monday. Some additional slick spots will be possible, but no widespread travel issues are expected as of this time. && .LONG TERM... (Tuesday through next Sunday) Issued at 246 PM CST Sun Dec 25 2022 Long term forecast period will be highlighted by warming temperatures and increasing rainfall chances as second half of week into at least first part of upcoming holiday weekend. Initially it is looking like one to two inches of rainfall could occur across our area Thursday through Saturday as shower chances increase, with isolated to scattered showers continuing across mid state region Saturday night into New Years Day. The reason behind this significant change in the atmospheric pattern is that a surface frontal system will begin to develop across central contiguous U.S. as Tuesday progresses and slowly shift eastward as weekend progresses. A possible surface frontal passage late Saturday night could occur. Development of this pattern will allow low level warm air advection to become increasingly established across our area. Deep upper level troughing developing across western contiguous U.S. by mid week will usher in southwesterly flow aloft as also this upper level system slowly shifts eastward. Highs by next Saturday afternoon could be as warm as low to mid 60s, upper 50s Cumberland Plateau Region with just slightly cooler temperatures expected on New Years Day. && .AVIATION... (00Z TAFS) Issued at 511 PM CST Sun Dec 25 2022 VFR conditions will continue through the evening and overnight hours with light SSW winds. A weak system will bring scattered light snow showers on Monday (after 12Z). Some episodes of MVFR cigs/vsbys will occur, but these episodes will be too brief and transient to include in tafs for BNA and MQY. CKV and CSV are more likely to keep MVFR and perhaps some brief IFR within some of the snow showers. && .PRELIMINARY POINT TEMPS/POPS... Nashville 16 36 23 42 / 10 40 20 0 Clarksville 15 36 20 38 / 40 50 20 0 Crossville 10 31 19 40 / 0 30 20 0 Columbia 14 36 20 42 / 10 30 10 0 Cookeville 12 32 22 40 / 0 40 20 0 Jamestown 10 31 19 40 / 0 40 20 0 Lawrenceburg 14 35 21 43 / 0 30 10 0 Murfreesboro 13 35 21 42 / 10 30 20 0 Waverly 15 35 21 38 / 40 40 20 0 && .OHX WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE.......21 SHORT TERM...JB Wright LONG TERM....JB Wright AVIATION.....13