Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/22/21

National Weather Service Albany NY
1009 PM EST Sun Feb 21 2021 .SYNOPSIS... Clouds will be on the increase tonight. A storm system approaching from the central U.S. will bring another round of accumulating snow to the area on Monday. Snow could mix with some rain across the lower elevations south and east of Albany. Temperatures early in the week will moderate to above normal levels by midweek, before trending colder than normal again by the end of the week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... As of 1008 PM EST...As a strong 1034 hpa high pressure area departs off the New Jersey shore, IR satellite imagery shows increasing high level clouds starting to expand towards the area. Sky cover will increase through the rest of the overnight hours, with skies become mostly cloudy for the entire area by the late night hours. 3km HRRR shows some light snow showers may start to work into parts of the western Adirondacks towards daybreak Monday. With the fairly clear skies and light winds this evening, temps have crashed rather quickly. NYS Mesonet obs show some places have dropped into the single digits and teens already, which will likely be the lows for the night. Once clouds move in, temperatures should hold steady and could even begin to increase into Monday morning. By late in the overnight, a southerly wind will begin to increase, especially for the north-south valleys, with some gusts starting to exceed 20 mph. && .SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/... A Winter Weather Advisory has been issued for northern Herkimer, Hamilton, and northern Fulton counties from 7 am EST Monday to 1 am EST Tuesday. Key Takeaways regarding Monday`s winter weather event: * Initial band of light snow between 4-7am (a quick coating to less than one inch expected; best chance eastern Catskills and areas north of I-90) * Prime time for accumulating snow: Between Noon-4pm or so * Snow could be heavy at times with snow rates exceeding 1"/hr (especially higher elevations) * Snow tapers to snow showers/flurries after 21z or so * Snow showers/flurries end between 7pm-1am everywhere except for maybe SW Adirondacks (Herkimer/Hamilton counties) Projected snowfall amounts: * 3-6 inches portions of SW Adirondacks extending into the northern Mohawk Valley and northwest Saratoga County (locally higher amounts of 6-8 inches across parts of Herkimer and Hamilton counties) * 2-4 inches across southern VT and eastern Catskills with locally higher amounts of 4-6 inches * 1-3 inches Berkshires into NW CT * Dusting to 2 inches elsewhere (lowest amounts over Albany and the Capital District) Other Keys: * Liquid to snow ratios: 9:1-15:1 (highest north, lowest south) * Snow will be wetter south, drier and fluffier north * Snow could mix with rain along the Hudson Valley (especially south and east of Albany) Technical Discussion: The short-term period will feature active weather with not one, but two chances at additional wintry precipitation. We start off the short-term forecast period with a negatively tilted, occluding surface low pressure system approaching from the central Great Lakes region. Before daybreak on Monday (roughly between 4-7am), a narrow band of light snow, associated with the leading edge of mid-level isentropic lifting, will move over the area. BUFKIT soundings depicts a moderate to deep column of dry air in the lower levels of the atmosphere (particularly under 800 mb). Because of this, snow will likely evaporate before reaching the ground (virga). This is especially true for the valley areas. That said, the best chance for snow to reach the ground with this initial band will be across the eastern Catskills, SW Adirondacks, and higher elevated areas north of I-90. Here, a coating to less than an inch of snow is possible. This could create for some locally hazardous driving conditions during the morning commute in these areas highlighted. As the storm system draws closer to the area, 850 mb low-level jet winds will increase in speed to near 50 kts around 18z (1pm). The increase in the warm conveyor belt winds will allow for an increase in temperature and moisture advection. Surface dewpoints around 18z (1pm) were sampled in the upper 20s to lower 30s across the ALY area. During this time, profile soundings indicate adequate moistening of the lower levels (below 800 mb) around 17z (noon). The main precipitation shield associated with more robust forcing from this storm system will move over the area from west to east beginning around 16-18z (11am-1pm). Because the lower levels of the atmosphere will have become saturated, the 16z-18z (11am- 1pm) timeframe is when we can expect the onset for precipitation areawide. Unlike the last storm system, this storm system will be warmer. Temperatures are projected to climb into the lower to mid-30s on Monday with mid-30s predominantly located over the Hudson Valley. Because of this, we have to deal with the potential for various precipitation types (p-types). At this time, trends continue to point towards things remaining all snow across the higher elevations and snow mixing with rain across the lower elevations/valleys (esp south and east of Albany). Things could initially start off as snow across the valleys. Diabatic cooling via wet-bulbing, however, will not be enough to offset the warmth advected into the area. Therefore, we expect an approximate 2-3 hour period of snow in the valleys before transitioning over to a rain/snow mix. The synoptic setup with this storm system supports orographic effects with upsloping favoring higher snow totals across the higher elevations and downsloping/shadowing favoring lower snow amounts across the valley areas. Large to meso-scale ageostrophic forcings, as well as mid-level instability is quite impressive especially during the beginning parts of this event. By 17z (noon) or around the onset time of precipitation, the area will be placed in the left exit region of a 145-150+ KT 250 mb jet that will be passing over the mid-Atlantic region. The best lift will be below the dendritic growth zone before the onset of precipitation, but by the start of precipitation adequate vertical ascent will have transitioned within/through the dendritic growth zone between 560-700 mb with omega values approaching or even slightly exceeding -2 Pa/s, according to some of the hi-res guidances. According to some of the deterministic models, three-hour isallobaric wind fields at the surface suggest 6-7mb pressure falls around 18z (1pm) which supports sufficient upward motion. Lastly, mid-level instability will be impressive with H7-H5 lapse rates approaching/exceeding 7C/km. All of this suggest that light to moderate snow could become heavy at times with snow rates likely exceeding 1-1.5"/hr. Given these impressive numbers, precipitation could show some convective characteristics. This is not expected to be a long-duration winter event, but rather a quick hitter with good snow rates. Between 21z-00z (4pm-7pm), snow is expected to taper down to snow showers/flurries. Snow showers/flurries should be coming to an end across most places except for the higher terrain areas between 00z-06z (7pm Monday- 1am Tuesday). The bulk of the accumulating snowfall will occur between 17z- 21z (noon-4pm) or so. As far as snow amounts expect 3-6 inches over portions of SW Adirondacks extending into the northern Mohawk Valley and northwest Saratoga County (locally higher amounts of 6-8 inches across parts of Herkimer and Hamilton counties), 2-4 inches across southern VT and eastern Catskills with locally higher amounts of 4-6 inches, 1-3 inches Berkshires into NW CT, and a dusting to 2 inches elsewhere (lowest amounts over Albany and the Capital District). Travel conditions will be slippery with the evening commute being most impacted. Use extra caution if you have to go out. Light southerly winds will pick up in intensity between 14z-21z (9am-4pm) becoming sustained at 10-20 mph and gusting 25-40 mph. Peak wind speeds will be between 15z-19z (10am-2pm) and will be concentrated along the Hudson Valley. We`ll get a very brief reprieve from any form of wintry precipitation Monday evening/night into Tuesday before another storm system tracking well to our north in Canada brings another round of light snow or rain/snow to the region. Early signs suggest that this will be another mountain snow valley rain/snow mix. Light snow accumulations appear likely due to 1) the best forcing being well to our north, 2) the snow associated with this system being pretty moisture starved, and 3) this batch of light snow being a quick hitter. Anywhere from a dusting to 3 inches of snow is plausible with the highest amounts once again over the higher elevations (upsloping) and lowest amounts along the Hudson Valley (downsloping/shadowing potential as well as rain/snow mix p-type). Temperatures will begin its trend higher early to mid-week. High temperatures on Monday are expected to top out in the lower to mid 30s and on Tuesday into the mid 30s to near 40F degrees (cooler higher elevations). Low temperatures Monday night into Tuesday morning will be mostly in the mid to upper 20s. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... An exiting upper level disturbance may still allow for a few lingering snow showers over the Adirondacks or southern Greens on Tuesday evening, otherwise, it should be dry across most of the area. Some breaks in the clouds are possible, especially for valley areas, but temps will only be lowering into the mid 20s to low 30s for lows on Tuesday night. Although Wednesday will start off dry, the next storm system will be approaching for later in the day and into Wed night. This will be a fairly weak wave of low pressure that will be approaching from the Ohio Valley/Great Lakes region and heading towards northern parts of the area as it lifts towards the Northeast. Best chance of seeing some light snow showers (mixed with or changed to rain at lower elevations) will be across western and northern parts of the area for late Wednesday into Wednesday evening and the first half of Wed night. Any snowfall amounts look fairy light and limited to mainly just the Adirondacks. Ahead of the approaching storm system, a southerly flow should allow for milder temps. Highs on Wednesday look to range from the mid 30s over the Adirondacks to the mid to upper 40s in the Capital Region and Hudson Valley. Behind the storm, temps look to fall into the 20s to near 30 for Wednesday night. Fast west-southwest flow aloft look to set up over the region for Thursday into Friday. This should keep mainly dry weather in place with fairly seasonable temps. There could be a few lake effect snow showers Thursday over CNY, but these should mainly be staying west of the area based on the expected northwest flow at lower levels. Valley areas should reach the mid to upper 30s for Thursday, but only lower to mid 30s for Friday. Another chance for some light rain or snow is expected over part of the weekend depending on the exact track of a southern stream storm system. At this point, the majority of models/ensemble members are showing this to be on the light side, as the best moisture/dynamics remain south of the region. However, this is subject to change. As of right now, temps look to continue to be close to seasonal normals for Saturday, with milder weather possible by Sunday. && .AVIATION /03Z MONDAY THROUGH FRIDAY/... VFR conditions are expected overnight. Clear skies and light/calm winds this evening will gradually give way to increase mid and high level clouds after midnight. Towards daybreak, southerly winds will begin to increase, especially at KALB. On Monday morning, clouds will continue to lower and thicken, but it will remain VFR for most of the morning hours. Southerly winds will increase to around 10 kts, with some higher gusts at times. Towards midday, light snow will begin spreading from west to east across the TAF sites, which should lower visibility to IFR range of 1 to 3 SM quickly once snow begins. Ceilings will generally be around 2-3 kft for all sites through the afternoon hours. Snow will last for most of the afternoon, but will be tapering off around 20z-22z, allowing for visibility to improve back to VFR levels. During the afternoon/early evening hours, southerly winds will be 10 to 20 kts for all sites. Some gusts of 20 to 30 kts are possible, with the strongest gusts at KALB. Some rain could mix in with the snow at KALB/KPOU, especially for the late-day hours. Winds will diminish slightly for Monday evening, but will still be somewhat gusty. Outlook... Monday Night: Moderate Operational Impact. Scattered SHSN. Tuesday: Moderate Operational Impact. Breezy. Scattered SHRA...SHSN. Tuesday Night: Low Operational Impact. Breezy. NO SIG WX. Wednesday: Low Operational Impact. NO SIG WX. Wednesday Night: Moderate Operational Impact. Chance of SHRA...SHSN. Thursday: Low Operational Impact. Slight Chance of SHRA...SHSN. && .HYDROLOGY... No widespread hydrological issues are expected over the next several days. Near seasonable temperatures are expected through early this week. This will continue to support mainly frozen precipitation types and allow ice to expand and thicken on area waterways. A storm system for Monday will bring additional light to moderate snow, possibly mixed with some valley rain on Monday. Temperatures will moderate to slightly above normal levels into the middle of next week, possibly allowing for some ripening/warming of the snowpack. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...Winter Weather Advisory from 7 AM Monday to 1 AM EST Tuesday for NYZ032-033-082. MA...None. VT...None. && $$ SYNOPSIS...Evbuoma NEAR TERM...Evbuoma/Frugis SHORT TERM...Evbuoma LONG TERM...Frugis AVIATION...Frugis HYDROLOGY...Evbuoma/KL
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
706 PM CST Sun Feb 21 2021 .UPDATE... 706 PM CST Overall, the evening is going as expected with wet/sloppy/slushy snow (at times mixing with light rain) falling across parts of northern Illinois and northwest Indiana. Temperatures across much of the area have climbed above freezing for the first time since February 4th (when interestingly enough the warmest temperatures were also during the evening), and southeast to south winds have been gusting in the 25 to 35 mph range. It`s a decidedly raw evening out there. At this point in time, we`re at about the midpoint of this system with peak areal coverage of precipitation. Trends in RAP forecast total positive energy (essentially the amount of "energy" available to melt falling snowflakes) suggests we may see snow changing to rain generally along and south of I-88 over the next few hours, with all snow continuing near the Wisconsin state line. Thus, any additional slushy accumulations will become increasingly confined to locations north of I-88. Precipitation should taper from west to east between 10 pm and 2 am, with all areas expected to be dry by 3 am. Breezy west to northwest winds will then return temperatures to below freezing by daybreak. As such, Monday morning commuters should keep an eye out for slick spots on untreated roadways (especially on bridges and overpasses). Borchardt && .SHORT TERM... 315 PM CST Through Monday night... Regional radar mosaic loops show the coverage of radar echoes gradually blossoming across northern and central Illinois this afternoon, serving as visual confirmation of the ongoing ascent and saturation of the air in the region owing to isentropic upglide, DPVA out ahead of the incoming shortwave, and upper divergence in the left exit region of jet that`s overhead and extending out to the southwest. Most the of reflectivity being sampled over the CWA was not quite reaching the ground yet as of 2:30 PM CST, but recent METARs from Rockford and Peru have indicated that precipitation has started across our western counties and is imminent elsewhere as the column continues to saturate and the surface low over central Iowa continues to work its way off to the northeast. Temperatures have warmed into the mid 30s in parts of the Chicago metro this afternoon, marking our first time above freezing in almost 17 days! With these temperatures likely remaining a few degrees above freezing for a few more hours, wouldn`t be surprised to see a brief period of at least a rain/snow mix if not outright rain at the very onset of precipitation in the Chicago metro, but given that below freezing wet-bulb temperatures will be present across the metro through the late evening and with somewhat heavy precipitation rates likely shortly after precipitation onset, we`ll likely cool down closer to freezing pretty quickly and any rain that falls at precipitation onset will change over to all snow soon after. Overall, the same general thoughts about snow rates and snow ratios from previous forecasts apply for this current forecast iteration. The potential for at least brief bursts of heavy snow still remains generally north of I-80 due to 7-8 C/km lapse rates through and just above the dendritic growth zone, with the most favored area for this still being generally northwest of a Dixon to Woodstock line. The favored timing for the heavier snow rates is still shortly after the onset of precipitation through the early evening. Snow ratios still look to range from about 7:1 to 12:1 with the lower ratios generally expected across our south and the higher ratios more likely farther north. Regardless of the exact ratios, this snow will be a wetter type of snow and not the fluffy kind that we had consistently seen over the past few weeks. There are a few minor changes regarding thoughts on final snow totals for the area. While the higher totals (2-4") are still favored to occur across northwestern and far north-central Illinois where the steeper lapse rates could overlap with some mid-level f-gen support and the lower totals (under 1") are still looking likely for areas well south of I-80, there are still concerns with the pesky dry slot currently to our west nosing a little farther north than previously expected which could cause some locations to underperform a bit in terms of final snowfall totals. Have nudged down snow totals slightly along the I-80 corridor where model and observational trends have increased confidence of the rain/snow mix line creeping that far north by mid-evening and to account for the potential for less precipitation occurring overall with the dry slot issue. Potential for loss of cloud ice is also evidently there with the 500 mb dry slot likely to chew up a good amount of moisture through the DGZ, which would suggest that a changeover to drizzle and/or snizzle is looking more possible by mid-evening. Nevertheless, hazardous travel due to sharp visibility reductions and slick roads (from both accumulating snow and any rain/drizzle that manages to freeze on roadways with sub-freezing surface temperatures) can still be expected late this afternoon and evening. Snow will begin to taper off later this evening as the steeper lapse rates move off to the east and the surface cyclone occludes to our north and northeast. Any lingering light snow or drizzle will end from west to east roughly between 10 PM and 2 AM CST. While the precipitation will end, gusty west winds of up to 30 mph will continue overnight into tomorrow afternoon. Another shortwave trough will swing down through the Great Lakes on Monday, but with the mid-levels deprived of any deep moisture and a lack of favorable dynamics over the region, any precipitation from this system should remain well to our north. Westerly to southwesterly flow will allow us to warm up a tad from Sunday`s highs, but cloud cover trapped under a stout 900 mb inversion will likely keep highs from getting any higher than the mid-upper 30s. Ogorek && .LONG TERM... 105 PM CST Tuesday through Sunday... With high temperatures expected to consistently push north of the freezing mark into the middle and end of the week, it`s certainly going to feel quite a bit different than the last several weeks here. Extended guidance continues to suggest, however, that we`ll remain in a fairly active pattern, with numerous disturbances slated to crest the eastern Pacific ridge and zip across the CONUS into next week. The main question is just what side of the baroclinic zone we`ll find ourselves. Tuesday offers up a pretty significant high temperature bust potential. The latest GFS, NAM, CMC, and UKMET continue to suggest that a robust subsidence inversion will keep low-level moisture and associated stratus locked in place, possibly even through Wednesday. The ECMWF, on the other hand, insists that we`ll readily chew through this via the combination of mechanical mixing and insolation, and commensurately drives high temperatures well in to the 40s across the region. The former guidance locks stratus in place all day, which would hold temperatures closer to the low to mid 30s. The path of least regret at this time is to follow the offered blended guidance, which is close to what local climatology would suggest with a deep snowpack in place. Either way, it looks like some bonafide 50 degree temperatures may not be too far to our south... A fast-moving disturbance offers a glancing blow of ascent Tuesday night into Wednesday. Low-levels look pretty parched, but this system could intercept sufficient moisture as it passes our longitude to start producing some precipitation. Could envision needing some slight chance PoPs south and east of I-55/57 for this, but for now, a dry forecast looks fine given the multi-model consensus. Temperatures will be a bit cooler on Wednesday with renewed northwesterly flow and cold advection. There are indications that a more amplified positively tilted trough shifts overhead Thursday behind the aforementioned short- wave, with temperatures trending cooler during that time. Currently expecting highs in the lower 30s, and lows Thursday night in the upper single digits to mid teens. Beyond Thursday guidance begins to diverge resulting in low confidence in any specific features. Will maintain slight to low chance PoPs early Saturday morning into Sunday, in line with the previous forecast and offered blended guidance today. However, as it stands, it appears the better chance for precipitation may lie just beyond the extended period as the upper level pattern becomes more amplified into early next week. Based on the latest forecast, some degree of snow melt during the days with re-freezing at night should help temper and flooding concerns. Carlaw/Petr && .AVIATION... For the 00Z TAFs... The primary concerns for the Chicago airports are: - Waves of moderate snow this evening, with period(s) of drizzle in-between; snow may mix with true rain after 03Z before ending - Slight chance of ice pellets mixed within any moderate/brief heavy snow areas - Gusty south-southeast winds becoming southwest after 03Z-04Z; will likely be temporarily out of the due south prior to shift - IFR ceilings moving in this evening and gradually lifting into MVFR by Monday morning - Gusty west winds overnight turning southwest again by midday Monday The first wave of snow looks to end at ORD and MDW by 0000Z-0015Z with a more prevalent light snow/drizzle then onsetting and persisting through 0100Z-0130Z. The chance for freezing drizzle looks low at this time, as surface temperatures will actually be inching upward on gusty southerly winds. A few gusts to 30 kt are possible, including during the next batch of snow/snow showers, which looks to arrive by not long after 01Z. With the combination of moderate snowfall rates expected and the gusty winds, we continue to note temporary 1/2SM visibility in the TAF. Confidence in this is a smidge lower at MDW, and will watch upstream trends to see how far south moderate/brief heavy snow is being observed. Precipitation should taper late evening into early overnight, and again a mix or even possibly a change to rain is possible before ending. IFR ceilings look to be prevalent much of this evening with higher confidence than earlier. Cannot rule out ceilings as low as 500 ft temporarily, especially at RFD, but even ORD may briefly see that low. As the system cold front passes early overnight, winds will turn westerly and gust to over 25 kt and ceilings should inch upward to the lower MVFR category by daybreak Monday. Confidence in low clouds scattering or clearing midday Monday is medium to high, though specific time is still low. If clearing fully occurs, some southwesterly gusts over 30 kt may be realized during the afternoon. MTF && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory...Winthrop Harbor to Northerly Is. until midnight Monday. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at: