Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/19/23

Area Forecast Discussion
National Weather Service Burlington VT
1017 PM EDT Sat Mar 18 2023 .SYNOPSIS... Scattered to numerous gusty snow showers will move through the region through the evening, and again tomorrow morning ahead of a couple of frontal boundaries. In between, a lake-effect snow band is expected to produce locally heavy snowfall in southeastern St. Lawrence County in New York. Blustery conditions reminiscent of mid-winter will occur Sunday with areas of blowing snow. A return to more seasonable weather is expected on Monday with some light valley rain and mountain snow at times through the first part of the week, followed by more widespread precipitation later in the week. && .NEAR TERM /THROUGH SUNDAY NIGHT/... As of 1016 PM EDT Saturday...The forecast remains in good shape for the overnight hours with the initial surge of snow showers occurring over southern portions of St. Lawrence County as expected, but the main lake effect event remains on track to take shape later tonight, which continues to be supported by the incoming 00Z guidance. So after the current radar activity wanes over the next hour or two, a brief lull is expected before the true lake effect band develops after 2-3AM and still looks to deposit a quick 3-6" across southern portions of St. Lawrence and Franklin Counties of New York. Previous Discussion...Snow shower activity has blossomed in response to daytime instability, height falls, and increasing surface convergence in advance of a weak surface cold front. The amount of instability and moisture is more than sufficient for convection, and as such the snow squall parameter in the western Adirondacks is greater than a value of 2 per RAP mesoanalysis late this afternoon. Relatively high cloud bases are supporting strong downdrafts with brief gusts in excess of 35 MPH possible; these stronger winds should be mainly in the St. Lawrence Valley through the rest of the daytime hours associated with a southwesterly low level jet. These winds should diminish somewhat tonight as flow becomes more west- southwesterly. As such, cold winds moving along Lake Ontario will support the lake-effect snow band into the favored downstream area of far southeastern St. Lawrence County and southern Franklin County in New York, where a Winter Weather Advisory remains in effect. Model guidance has honed in on roughly a six hour period with best chances for heavy lake effect snow, roughly 2 AM to 8 AM, before wind shear increases and the band diminishes tomorrow morning. Still expect locally as much as 8 inches with sharply lower amounts heading farther north into the Advisory area, although this region will see snow showers aside from the lake effect band tonight into tomorrow. Relatively mild temperatures today will trend much cooler tonight as low level temperatures drop sharply. This well below normal air mass, featuring surface temperatures in the twenties, will help steepen low level lapse rates again. As such, expect gusty westerly winds, and any snow showers will be prone to blowing around given their low density. Even when scattered snow showers diminish in the afternoon, have indicated areas of blowing snow to continue primarily in higher elevations. Again, with lack of a strong surface front tomorrow morning, the organization and intensity of snow showers will likely be limited, but are generally from the northern Adirondacks eastward through the northern two-thirds of Vermont some briefly heavy and gusty snow showers are possible. Lingering showers should tend to diminish during the afternoon and be focused along and east of the spine of the Greens due to strongly unblocked flow. With a continued pressure gradient through the night and some cloud cover possible overnight, have not shown much of a temperature change moving through the night. In fact, by Monday morning some locations may be a bit milder than in the evening as some warm air advection develops. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... As of 338 PM EDT Saturday...With a trough passing north of the international border along with lingering 700mb moisture, light showers could linger in the Adirondacks, northern Greens, and the Northeast Kingdom throughout the day Monday. Any additional lake effect snow falling in northern New York is expected to drop off by the end of the morning. PoPs are in the 25-30% range at most. West/southwesterly winds will draw in milder air, allowing highs to rebound into the upper 30s to lower 40s, around average for this time of year. Due to this, any snow accumulations with this light snow will be limited to a dusting to couple tenths of an inch at higher elevations. The precipitation reaching the valleys will most likely be rain. Including in the St. Lawrence Valley, where conditions could become gusty with up to around 25 mph gusts, and in general the forecast area will have good mixing and gusty winds. The southern half of the area could even have a good amount of sunshine in the afternoon as high pressure expands northward from the mid- Atlantic. A shortwave is expected to move toward/into our forecast area Monday night, returning the potential for snow showers along the international border/Adirondacks, where best moisture will traverse. PoPs capped at around 20-30% for this period, and clouds start increasing from the northwest to southeast. Winds out of the southwest are anticipated to calm slightly throughout the night with lows in the 20s, again around average. Thanks to these colder temps, any showers are expected to be snow showers overnight, with just another few tenths of accumulations in the Adirondacks. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 338 PM EDT Saturday...A shortwave passing through the region as a jet streak sets us in its left exit region on Tuesday will produce more shower activity and mostly cloudy skies, mainly for the northern half of the forecast area with PoPs 25-30% at most. Showers could start as snow early, but rain will likely take over as dominant p-type throughout the day as temperatures rise into the 40s. Winds are expected to turn more westerly Tuesday morning, then calm and variable Tuesday afternoon as shortwave energy departs and ridging builds in into Wednesday. This ridging will produce briefly dry weather Tuesday night/early Wednesday, but another shortwave will head into the Great Lakes with a larger trough following it across Manitoba. Late Wednesday into Thursday, these features look to combine in Ontario as they head into Quebec, associated with a low pressure at the surface. Our forecast area will initially receive an influx of milder air and precipitation Wednesday night as the system occludes to our north. Best chances for precip occur Wednesday night-Thursday, so widespread 30%+ chances with 50-65% chances mostly in terrain-driven upslope areas. Thursday night, chances linger in the 30-40% range. Temperatures Wednesday and Thursday will rise into the 40s, while south-central Vermont could even flirt with the lower 50s. This will mean mostly rain again for the valleys as snow mixes in at higher elevations. As warmer air affects the atmospheric column, model soundings show warm nose bending toward the 0 C line in some spots, like the Northeast Kingdom and the Greens, so there`s the potential for a bit of wintry mix, but overall it looks isolated and low confidence at this time. We are also monitoring the potential for minor river flooding, but with this being the extended period, much can change between now and the event. Currently ensemble models are indicating a few not-insignificant river rises across the forecast area. We will have to see how models handle QPF with this system in the coming days. A frontal boundary is expected to drag through the forecast area following the initial midweek batch of precip, so PoPs remain around 30-50% into Saturday night with the potential for showers as a shortwave rides the front. Highs could come down slightly Friday and Saturday, but overall still looking to stay in the 40s. Once again valley rain, snow mixing to the summits, however, at night, there`s the chance for more snow than rain showers with this front as temps drop. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... Through 00z Monday...Mainly VFR, although isolated to scattered snow showers will result in occasional MVFR and IFR visibilities. Timing of these showers is challenging with multiple boundaries moving eastward through the region. Have utilized the 00z hi-res guidance to better time the snow showers, which could briefly drop vsby to MVFR although cigs should stay mainly VFR between 3500 to 4500 ft. The exception is KSLK, where more persistent snow from a lake effect band off Lake Ontario looks to impact the terminal between 06z and 10z with IFR vsby and perhaps MVFR cigs. Winds will be predominantly southwest through 12z Sunday then turning more westerly. It will be quite breezy with winds gusting to 25 kt and even a few isolated 30 kt gusts possible. Outlook... Sunday Night: VFR. Slight chance SHSN. Monday: VFR. Slight chance SHRA, Slight chance SHSN. Monday Night: VFR. Slight chance SHSN. Tuesday: Mainly VFR, with local MVFR possible. NO SIG WX. Tuesday Night: Mainly VFR, with areas MVFR possible. NO SIG WX. Wednesday: VFR. Slight chance SHRA. Wednesday Night: Mainly VFR, with areas MVFR possible. Chance SHRA, Chance SHSN. Thursday: Mainly MVFR, with local IFR possible. Chance SHRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...Winter Weather Advisory until 2 PM EDT Sunday for NYZ029-030- 034. && $$ SYNOPSIS...Kutikoff NEAR TERM...Kutikoff/Lahiff SHORT TERM...Storm LONG TERM...Storm AVIATION...Chai
Area Forecast Discussion...UPDATED
National Weather Service Indianapolis IN
1030 PM EDT Sat Mar 18 2023 .Mesoscale Update... Issued at 1030 PM EDT Sat Mar 18 2023 Residual shallow layer of instability is supporting a narrow band of moderate to heavy snow showers from near Crawfordsville to Westfield and Carmel to northern Hancock County. This band is organizing west-northwest to east-southeast parallel to mean PBL flow and may bring a brief burst of significantly reduced visibility and cause a few slick spots on roads over the next hour or so, before decreasing in intensity through midnight. Northern portions of Indianapolis will be impacted as this band moves southeastward at around 25 mph. We have sent a localized Special Weather Statement to describe travel impact potential, since we`re seeing some reduced traffic speeds on Google Maps traffic data under this snow band. Elsewhere, flurries are still likely into the first part of the night as a shallow convective layer remains optimally placed within the dendritic growth temperature range. These will be inconsequential and nonmeasurable, however. Impacts should be limited to the narrow corridor described above, and will be minor. && .Forecast Update... Issued at 635 PM EDT Sat Mar 18 2023 CIRA layered precipitable water product shows a drier lower troposphere advecting into northern Illinois. This will reach central Indiana later tonight, and bring an end to the flurries and snow showers. In fact, even before then, minimal surface heating contributing to a layer of shallow convective instability should slowly diminish through the evening. Thus, the cellular convective snow showers should steadily/slowly decrease early-mid evening. There may be just enough residual convective instability and optimally-placed convective cloud within the dendritic growth zone for a few flurries to persist the first half of the night. MSLP gradient, mechanical mixing, and clouds should prevent a sharp temperature drop tonight. However, temperatures have been roughly around the 25th percentile of models this afternoon. So, the magnitude of this Arctic air mass isn`t fully captured and we will follow day shift`s lead and keep temperatures in the lower percentile range (i.e., around the 25th percentile, or roughly on par with the HRRR though maybe a degree colder) through the night. All that is to say the current forecast is largely on track with only nitpicky details addressed in this update. Have a good evening. && .Short Term...(This evening through Sunday) Issued at 302 PM EDT Sat Mar 18 2023 * Very cold for mid March tonight * Scattered snow showers and flurries end this evening * Dry and a little warmer Sunday Arctic air continued to flow into central Indiana this afternoon. This is resulting in clouds reestablishing themselves across the area, and the additional development of flurries and scattered snow showers. Temperatures were from near 20 into the upper 20s. Rest of this afternoon... Cold advection will continue along with cyclonic flow. This will keep the scattered snow showers and flurries going, especially north. Not expecting much if any accumulation with these as the atmosphere overall is pretty dry. With the low water content of the snow, it will blow around easily. Gusty winds will persist with a decent pressure gradient across the area, with gusts over 30 mph common. This will make it feel even colder. Tonight... The core of the cold air will move into the area during the first half of the Tonight period. Some flurries will linger into the evening with this, but with loss of heating, expect the snow showers to end by early tonight. Clouds will continue with the cold still aloft, but more holes may develop as heating is lost. Overnight, the southern forecast area should see skies become partly cloudy. However, lower clouds will linger in the remaining cyclonic flow north. Winds will remain up around 10mph, so radiational cooling with not be strong. However, the Arctic nature of the airmass will still allow temperatures to fall into the teens most areas. Will trend below blended guidance given the strength of the cold air. Sunday... The upper trough will exit the area as surface high pressure builds in with drier air. This should erode the remaining clouds during the morning hours. Sunshine and some warmer air moving in will bring highs back into the mid and upper 30s. This is still much below the normal highs in the 50s. && .Long Term...(Sunday night through Saturday) Issued at 300 PM EDT Sat Mar 18 2023 * Noticeable Moderation Monday through Thursday * More Active Pattern Wednesday-Friday, Potential For Heavy Rainfall Sunday Night through Tuesday... The long term will start dry amid a noticeable moderating trend as rather broad surface high pressure slowly slides from the Mississippi Valley to the Mid-Atlantic. Ample March sun will shine through the dry column through much of the early week. Coupled with increasing south-southwesterly breezes, a noticeable transition Monday should find temperatures climbing at least 25 degrees to around 50F. Moderation will continue into Tuesday, with surface low pressure slowly approaching from the central High Plains...backing the robust fetch to southerly, promoting thickening clouds. Fairly certain no organized rain reaches the CWA through the late Tuesday timeframe given the dry lower levels. Appears temp/dewpoint combos will promote daily minimum relative humidity values near 25-35 percent both Monday and Tuesday which could briefly present marginal fire weather concerns during afternoon hours...with this potential to be refined in updated packages. Readings are expected to peak in the 50s Tuesday. Tuesday Night through Saturday... The pattern will then turn more active for the midweek through Friday amid above normal temperatures and perhaps at least brief anomalously high humidity. Surface low pressure expected to pass well to the north/west of the region should bring a decent slug of light-moderate rainfall into the Wednesday timeframe. Greater impacts will likely accompany a nearly-stationary frontal boundary as it slowly crosses the Midwest in the Thursday-Friday period, with at the very least potential for extended rain. A subtropical upper ridge strengthening along the Gulf coast will build northward while sliding into the southeastern United States. Above normal readings will be pumped into Indiana on gusty southerly breezes. Adequate instability for thunderstorms so far appears most likely on Thursday when highs in the 60s could couple with dewpoints in the 50s...with the possibility of additional moderate/heavy rainfall to close out the workweek as the boundary finally crosses to the Ohio Valley. So far appears the long term will end with another area of surface high pressure advancing drier conditions into the Midwest, although with a less pronounced ridge of more seasonable temperatures than the current cold blast. && .Aviation...(00Z TAF Issuance) Issued at 425 PM EDT Sat Mar 18 2023 Impacts: * Flurries with scattered snow showers producing brief bursts of reduced visibility through early evening * Gusts 25-30 knots subsiding this evening Discussion: Cyclonic moist flow and influence from an eastward migrating weather system centered over the Great Lakes will keep occasional snow flurries and scattered snow showers through early evening. Once the diurnal convective cycle subsides winds will become less gusty and snow showers will decrease. Brief MVFR ceilings and sub-VFR visibility can be expected with passing more significant snow showers until then. Afterwards, improving flying conditions are expected. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ Mesoscale...BRB Update...BRB Short Term...50 Long Term...AGM Aviation...BRB
Area Forecast Discussion
National Weather Service Northern Indiana
732 PM EDT Sat Mar 18 2023 .SYNOPSIS... Issued at 156 PM EDT Sat Mar 18 2023 Lake effect snow showers will persist through this evening, with the greatest intensity and accumulation potential north of the Toll Road. Expect 1 to 3 inches of snow, with localized amounts up to 4 inches in the advisory. It will remain windy and cold through tonight before warmer temperatures return Sunday and into next week. && .SHORT TERM...(This Evening through Sunday) Issued at 242 PM EDT Sat Mar 18 2023 A upper low pressure system moving east across southern Canada and the upper Great Lakes is the weather-maker for today and tonight. Snow showers forced along by a cold front front brought 1 to 2 inches of accumulations to the 1st and second tiers of counties in our south this morning. Additionally, the lake effect snow belts were invigorated with the fresh shot of cold air. Lake induced temperature differences of 25 to 30 degrees will become more like 20 to 25 degrees tonight as the back side of the area of vorticity associated with the upper low exits the forecast area. Lake induced inversions will rise up to about 700 mb or 8.5 to 9 kft today before slowly falling overnight. Low level moisture today appears the best within Michigan on those mainly 290 degree trajectories before a more northwest wind triggered by a departing surface instability trough this evening starts the slow dissipation process over of the moisture overnight. All through this, a particular problem is the sub-950 dryness apparent in forecast soundings. Additionally, strong gusty winds between 25 and 40 mph during the afternoon are expected to taper off tonight as the gradient relaxes causing the low level jet to relax. But these winds will serve to break up the snowflakes as they fall likely reducing their influence on accumulations, but lowering visibility due to their greater reflectivity within the daytime light. One concern for the late afternoon into tonight period will be that aforementioned shift in the low level wind trajectories. This would change the direction of convergent boundaries located in the wind field and the RAP in particular wants to set up a single band through the Michigan counties and into a few Northern Indiana counties. Have noted a similar shift in the other model output QPF as well. The aforementioned issues with the snowfall accumulation have kept totals down during the daytime, but we`ll lose the sunlight`s influence tonight and the winds die down slightly allowing for flake size to trend larger. All these factors taken into consideration, have allowed for an additional 1 to 3 inches of lake effect snowfall within the advisory area and perhaps into St. Joseph, Elkhart, and Lagrange Indiana counties. A stray 4 inch area of snowfall will be most possible between Cass and St Joseph, Michigan counties, which may be where the lake effect snow band has its largest residence time. Lowered visibility will again be possible and may briefly hamper travel within the heavier lake effect snow bands. Temperatures tonight will be able to drop back to the upper teens to low 20s as the dry/cool air begins an attempt to shut off the lake induced cloud/precip plumes. Height rises begin to come in and low level moisture will be mostly gutted after 00z tonight, but will take a dissipation of the low level wind convergence and swivel of the wind trajectories to a more southerly wind component to shut off lake effect snowfall. That change doesn`t look to occur until Sunday morning and so will hang on to cloud cover and at least 15 to 20 PoPs into this period to track the dissipation. Highs Sunday reach into the mid 30s. && .LONG TERM...(Sunday Night through Saturday) Issued at 242 PM EDT Sat Mar 18 2023 With the upper low pulling away and the aforementioned warming low level temperatures we start the warming trend back towards seasonable temperatures and reach those by Monday. But above normal 50 degree temperatures will be common on Tuesday through Friday with 60s also possible. The one problem for reaching these above normal temperatures would be the rain chances that enter the area Tuesday night and continue at times into the next work week. The Tuesday through Wednesday rain chances would be from various weak vort maxes moving by to our northwest with the warm advection wing. Models have attributed a bit more moisture to these and have produced more light precipitation with them as a result. Thereafter, a baroclinic zone stalls nearby the area likely as a result of the southeast CONUS ridge setting up. Various weak waves of low pressure ride along it each providing a dose of moisture/rainfall to the area. These extra doses of rainfall would serve to provide an uptick to the recently saturated ground likely reinvigorating the river flooding. We`ll need to watch the track of a low pressure system late week into the weekend. The NAO flips neutral to negative and may allow a more southward track to the low, but by how much is unsure this far out. && .AVIATION...(For the 00Z TAFS through 00Z Sunday Evening) Issued at 724 PM EDT Sat Mar 18 2023 Strongest lake effect snow bands appear to be north of SBN, where there is also better low level moisture. Yet still expect rapid fluctuations between VFR and IFR as cellular snow snow continue to pass over the terminal. Will account for this with a wide range in visibility between dominant conditions and tempo group. Concerns much lower at KFWA which is seeing much lighter snow showers/flurries with only brief MVFR conditions possible. Snow showers look to quickly wind down overnight as deepest moisture and lift departs with a return to VFR conditions expected and eventually clearing of the cloud cover on Sunday. Gusty west wind this evening will subside some overnight but likely to remain above 10 kts through the day Sunday. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...Winter Weather Advisory until 5 AM EDT Sunday for MIZ078>080-177- 277. OH...NONE. LM...Small Craft Advisory until 5 PM EDT Sunday for LMZ043-046. && $$ SYNOPSIS...MCD/Fisher SHORT TERM...Roller LONG TERM...Roller AVIATION...Cobb Visit us at Follow us on Facebook...Twitter...and YouTube at:
Area Forecast Discussion
National Weather Service New Orleans LA
814 PM CDT Sat Mar 18 2023 ...New EVENING UPDATE... .EVENING UPDATE... Issued at 759 PM CDT Sat Mar 18 2023 Performed a gridded forecast update this evening to reflect observations and recent model guidance. Forecast is looking on track generally with little adjustments required. Main focus in the next 12 hours will be the cold, and how cloud cover and a passing front will impact the diurnal trends and attendant MinT`s. Can`t sway too far away from the earlier forecast with good consensus continuing. Hanging on the idea that winds will pick up later tonight enhancing low-level mixing, disrupting the plunge of temperatures which is also impacted by cloud cover leading to modest insulation. Am seeing a brief window of freezing temperatures for atelast portions of SW MS however regardless of these limiting factors as CAA intensifies but be aware - a warmer bias would be meteorologically plausible especially if guidance is not picking up on the degree of winds/cloud cover offsetting the strong CAA which may prevent areas to reach freezing. Overall - mid to upper 30`s for the northern half of the CWA is looking good and sits right around deterministic with very little, if any adjustments required. As for winds, can`t ignore the potential for winds to remain up enough throughout the night given this reinforcing frontal passage. Winds near calm to 0-3kt is well below the NBM10th percentile. Did increase winds a notch tonight above the 10th but lower than the deterministic which again, further supports the potential warmer bias in the forecast and will be monitored. Could very well be a case where the diurnal trend drops faster ahead of the front throughout the night, then flat lines/slows around daybreak as mixing kicks up. Sunshine attempts at returning in intervals tomorrow, but may not be completely done with the clouds as the base of a strongly positive-tilted trough axis to our north swings down the MS river valley, meeting up a weak/subtle impulse pressing ENE from the Mexican plateau into SE TX. Enough downstream divergence and moisture feed will support mid to upper-level clouds. Deterministic NBM settled well into the higher end of ensemble guidance and I like this. It`s important to note simply the time of the year - keeping temperatures cold all day requires very strong CAA and thick clouds. Any degree of offset would explain a warmer bias as well for highs. Blended in the 75th for highs bringing many areas in the mid 50`s. Aware this sticks out a bit, but wanted to make sure we are on the right track given the synoptic setup and time of the year. Otherwise, winds remain breezy at times tomorrow especially over marine areas and across north- facing shorelines. Introduced the NBM10th percentile in dewpoints in the afternoon to account for strong mixing per HRRR soundings as deterministic NBM is notorious at under doing. No other additional impacts expected. KLG && .SHORT TERM... (This evening through Monday night) Issued at 235 PM CDT Sat Mar 18 2023 Not much change from the previous forecasts. Biggest concern and challenge in the short term is trying to determine overnight lows for tonight and tomorrow night. At the risk of continuing to repeat, the temperature forecast for tonight is a bit tricky. Much of the guidance indicates potential for freezing temperatures across our southwest MS counties as well as some northern portions of the adjacent LA parishes, and even down the Pearl and Pascagoula drainages. The limiting factors are going to be lingering clouds at least through the first part of the night, as well as some mixing owing to a secondary shot of cold air advection associated with a fast moving shortwave. Both of these factors will cut down on the radiational component of overnight cooling. Most likely freeze locations still look to be across our southwestern Mississippi counties from Wilkinson across to Walthall. In these areas, even the warmer NBM guidance continues to indicate freezing temperatures for at least the northern half of each county. Another factor playing a supporting role is that these areas only warmed to right around 50 degrees today. Current temperatures are even still in the upper 40s at some observation sites in these counties. That being said, the temperature doesn`t need to drop quite as far to reach the freezing mark. Have gone ahead and upgraded the freeze watch for SW MS to a freeze warning for tonight. Sunday will be another rather chilly day for March with afternoon temperatures only rising into the low to mid 50s. It won`t feel quite as raw as today though as there will be fewer clouds. Winds will still be a little breezy, but not quite as strong as today, either. Sunday night there is high confidence that we will see widespread light freeze impacts for much of the area. Conditions appear much more favorable for an efficient radiative cooling night with mostly clear skies, winds easing to 5 mph or lower in places away from the south shore of the tidal lakes, and dewpoints in the low to mid 20s for much of the area. With those factors in mind, temperatures should begin to plummet after sunset. At this point the biggest question continues to be how far south will it freeze? At this time the main portion of the New Orleans metro looks to remain above freezing as winds off the lake will moderate the temperatures somewhat. Am generally forecasting upper 30s for these areas. Similarly, areas closest to the Louisiana coast should remain above freezing. The question is for areas from Belle Chasse across the west bank through upper portions of Terrebonne and Lafourche Parishes. MOS numbers continue to be several degrees lower than the NBM forecast in these areas. For example, the 12z MAV and MET indicate lows of 32 and 30, respectively, at KNBG. The 12z Euro ensemble mean is 32 with a 50th percentile of 31 and a low member of 26 (LOL). The latest run of the NBM comes in at 37. A similar story unfolds at Houma, though even the NBM has come in at 34 there with the latest run. I do think the MOS guidance, especially the ECM, is a little too cool, so I didn`t make a lot of adjustment to the NBM numbers except in the Belle Chasse and west bank areas where the NBM tends to struggle more. This results in min temperatures generally in the mid 30s for these areas. However, there are some isolated spots in portions of northern Terrebonne and Lafourche, and on the west banks of St. John and St. Charles Parishes that could touch the freezing mark. Confidence in this happening is low so I`ve opted not to expand the area of the freeze headline at this time, but the next couple shifts will need to take a close look at some of these areas to make a more informed decision. Given the high confidence of freezing conditions elsewhere, though, have upgraded the previous freeze watch to a freeze warning for areas that are generally along and north of a line from Morgan City to Lake Maurepas, and eastward across the north shore and Mississippi coast. After starting out quite chilly, temperatures Monday should rebound into the upper 50s to even lower 60s in some places as we lose the influence of cold air advection. Monday night temperatures look to stay above freezing but will still dip into the mid to upper 30s across northern areas. && .LONG TERM... (Tuesday through Friday night) Issued at 235 PM CDT Sat Mar 18 2023 Zonal flow will dominate the upper level pattern Tuesday, transitioning to strong ridging and high pressure influencing the area Wednesday and Thursday. Southerly surface winds will advect warm air and moist air into the area throughout the week. Tuesday through Thursday, looking at the models, will be pretty dry with above average temperatures. We will warm up considerably from Tuesday through the end of the week. There was not good model consensus on the high temperatures, but given the calm winds and mostly sunny skies, it could be possible to overachieve on guidance. It will be something we may need to adjust in the forecast down the road, but for now, NBM was left in the forecast due to the numerous model uncertainties. Generally, highs in the low 80s could be expected Wednesday/Thursday timeframe thanks to the strong ridging and extra daylight hours. Friday, a shortwave system will move through the area. It is too soon to discuss many details. But strong warm air advection ahead of the system will help enhance instability. Weak upper level divergence will help to enhance lifting in the environment. Some strong storms may be possible, if there is decent shear. But that will depend on how far north the best forcing ends up, and the models cannot agree on that at the moment. Looking at the current pattern in the models, there could also be some concern for flash flooding given the orientation of the line and the slower shear/movement. It will be something worth monitoring as we get closer to the event. && .AVIATION... (00Z TAFS) Issued at 620 PM CDT Sat Mar 18 2023 Expect VFR conditions through the TAF period for all local sites. Seeing mid to upper-level BKN to OVC clouds across the area which will break up going into tonight. Some FEW to SKC during the day tomorrow. Otherwise, main impacts will be a reinforcing cold front sliding south overnight, which will increase winds around daybreak lasting into the day on Sunday. Wind direction bearing 350 to 010 can be expected with occasional sfc gusts to 15 to 20kts. Stronger winds can be expected for terminals near north-facing shorelines including KNEW where winds may gust upwards of 20-30kts by the time the front passes early Sunday, lasting through the day but otherwise, no additional impacts are anticipated. && .MARINE... Issued at 235 PM CDT Sat Mar 18 2023 Hazardous conditions persist across the coastal waters through Sunday afternoon owing to cold air advection and a tight pressure gradient between low pressure between the frontal trough extending through Florida and into the central Gulf, and high pressure centered over the Rockies. The high will finally build in enough by Sunday evening to hopefully end headlines and then winds will slowly veer back around to the southeast as the high lifts northeastward through the work week. && .PRELIMINARY POINT TEMPS/POPS... MCB 31 49 26 56 / 0 0 0 0 BTR 37 54 31 59 / 0 0 0 0 ASD 37 56 30 60 / 0 0 0 0 MSY 43 54 39 56 / 0 0 0 0 GPT 38 54 32 57 / 0 0 0 0 PQL 35 56 28 60 / 0 0 0 0 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...Freeze Warning from 10 PM Sunday to 10 AM CDT Monday for LAZ034>037-039-046>048-056-057-071-076-079>086. GM...Small Craft Advisory until 1 PM CDT Sunday for GMZ530-532-534- 536-538-550-552-555-557-570-572-575-577. MS...Freeze Warning from 10 PM Sunday to 10 AM CDT Monday for MSZ068>071-077-083>088. Freeze Warning from 2 AM to 9 AM CDT Sunday for MSZ068>071. GM...Small Craft Advisory until 1 PM CDT Sunday for GMZ532-534-536- 538-550-552-555-557-570-572-575-577. && $$ SHORT TERM...DM LONG TERM....MSW AVIATION...KLG MARINE...DM
Area Forecast Discussion
National Weather Service Marquette MI
746 PM EDT Sat Mar 18 2023 .SHORT TERM...(Through Tonight) Issued at 359 PM EDT SAT MAR 18 2023 Water vapor imagery and RAP analysis show a deep mid-level low over the Great Lakes region, centered n of Georgian Bay, with 500mb height anomalies around 360m over northern MI. 850mb trof passed across the area late last night, reinvigorating lake enhanced snow off of Lake Superior under deep cyclonic northerly flow per KMQT VAD wind profile. Per latest RAP analysis, 850mb thermal trof at around -18C currently extends ne to sw across the area. Lake enhanced snow this morning into the aftn has not well-organized, which limited snow accumulations to some degree by limiting the duration of hvy snow. Nonetheless, the deep moisture to near 20kft and healthy overlake instability has resulted in frequent bursts of hvy snowfall. KMQT radar has shown +28dbz echoes scattered throughout the lake effect regime, suggesting at least 1 inch/hr snowfall rates at times. Webcams have also shown periodic very low vis in the heavy snow showers. Gusty winds to 25-40mph, strongest at exposed locations near Lake Superior (Copper Harbor ASOS peaked at 51mph), are also creating blsn and sharply reduced vis. Increasingly stronger solar insolation at this time of year has also supported land based development of -shsn/flurries outside of the lake effect areas, well inland in s central Upper MI. Back edge of deep moisture is currently pushing se with drying at the lower levels as well. With this drying spreading across western and northern Lake Superior, LES has taken a notable hit out w with LES ending close to the lake. It`s a cold aftn for mid Mar with temps currently running in the mid teens to lwr 20s F. So far, temp has only reached 15F here at the NWS office. The record low max temp for the day at this location is 19F. That will likely be broken. As drying continues to spread se thru the late aftn/evening, expect a rapid diminishing of LES from w to e across the area. There may not even be any flurries lingering over the w by late aftn. Diurnally aided flurries/-shsn over the s central will end quickly toward sunset. Lingering LES over the e will wind down to mostly just flurries this evening. With the DGZ dominating the shallow convective layer, will probably see some flurries linger well into the overnight hrs. To the w, skies will become mostly clear. With high pres well to the sw over the Plains and a shortwave and associated sfc trof dropping into northern Ontario, it won`t be a great radiational cooling night by any means as winds won`t completely decouple. However, given the cold conditions leading to sunset and a new layer of fresh snow cover, will lean toward the lower side of guidance for the interior. MET/MAV have a min temp of 0F and 1F, respectively, at KLNL which is often a good indicator of where traditional cold spots over the w will end up. Won`t go quite that cold, but interior cold spots will likely fall to about 5F. Otherwise, 10 to 15F will generally be the rule. .LONG TERM...(Sunday through Saturday) Issued at 344 PM EDT SAT MAR 18 2023 Starting Sunday, we get a little bit of a breather from the active weather pattern as the low pressure bringing the LES over us this afternoon continues to lift away into northern Quebec tomorrow. This allows a quick reprieve from snowfall Sunday, with mostly sunny skies expected across the area. With high pressure ridging skirting by to our southwest Sunday, expect some WAA which, combined with the sunny skies, should give us high temps in the mid 30s to around 40F over the south central. Therefore, if you have the winter blues or are tired of being stuck inside the past few days, Sunday would be a great day to enjoy the outdoors! As we move into Sunday night, a cold front from northern Ontario drops south over Lake Superior and moves over the area. Model guidance, particularly CAMs, are hinting at a line of convection forming over the lake from west to east along the frontal boundary due to some weak fgen along the front. As the front moves southwards over the northern portion of the UP, a quick burst of snowfall could be seen over the area, with possibly moderate to heavy snowfall being seen for a few minutes along the band. However, as the fgen band dies out, marginal and light LES sets up over the north to northeast snow belts late tonight into early Monday. Light, weak, and pulse-y LES could continue over the northeast snow belts throughout the rest of the day. Overall, thinking impacts associated with this cold front will be fairly minimal, as snow totals should range from a dusting to around an inch. The only concern would be when the band of snowfall associated with the fgen comes onshore, as snowfall rates then may greatly reduce visibility and quickly accumulate on roads (albeit only for a short while); however, these concerns are relieved a bit due to this occurring overnight though. The next system that looks to impact us is expected to come around Tuesday evening. With model guidance projecting a Colorado low to move through MN Tuesday night, expect the warm front of this low to bring some wet snowfall and rain to the area. Most of the area should start out as pure snowfall, save for maybe southern Menominee County. However, as the warm front slowly lifts through the area Tuesday night into Wednesday, expect the transition from snowfall to rain from the south and west to the north and east. Ahead of the transition, it looks like we could see up to moderate snowfall at times, with sloppy accumulations that may be enough for a low-end winter weather headline, particularly over the north and west. Model guidance has QPF for this event ranging from around 0.20 to 0.60 inches (this includes the rain and snow); the greatest QPF totals look to occur along the southeast upslope areas. Once the warm front moves through Wednesday, expect high temps to get into the 40s across the area before the cold front pushes in Wednesday afternoon and evening; some additional light rain/snowfall is expected with the cold front`s passage. Recent model solutions have shifted northward a second low pressure that was previously slated to move through the Lower Midwest late this work week. While the Euro keeps the low along the MI/IN line and the GFS has it slightly further north, the Canadian, UKMET, and NBM seem to highlight the possibility of the low lifting through Lake MI or northern Lower MI into northern Ontario Thursday. However, confidence in the most northerly solutions is fairly low, as the previous runs and the current GFS and Euro keep the low well south of the area; it will depend on the strength and speed of the high pressure dropping from Canada into the Plains during the middle of next week. However, given how the previous storm system lifted drastically north and westward last week, solutions with precip occuring over the UP are still on the table. Should the more northerly solutions win, we could see some more snowfall across the area late Wednesday night into possibly Thursday. Meanwhile, the chance for precip heading into next weekend isn`t looking all that great; while the Euro keeps the strong low pressure solution moving through Lake Erie Friday night, other medium range guidance keeps nominal ridging over us. Nevertheless, it still looks possible that a weak cold front from northern Ontario could drop down over the area and bring some snowfall back across the UP this weekend. Overall, temps look to be around normal over the course of this next week, although we can expect to see some swings from above normal (like Sunday and Wednesday) to below normal (like Monday and Tuesday) throughout the week as the generally active weather pattern continues. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 726 PM EDT SAT MAR 18 2023 High pressure building in from the west and associated much drier air will quickly diminish any remaining lake effect -shsn this evening as the terminals improve to VFR. Northwest winds will also be diminishing through the night and backing west. As winds back west late tonight into Sunday west winds will become gusty at CMX with gusts to around 30 kts during the day on Sunday. West- southwest winds between 20 to 25 knots are expected at IWD on Sunday. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 404 PM EDT SAT MAR 18 2023 As a low pressure system continues to pull away into northern Quebec tonight into Sunday morning, expect winds to diminish this evening as they back with time, with NNW gales up to 40 kts over the eastern lake early becoming NW winds 20 to 30 kts by Sunday morning. Likewise, any heavy freezing spray continuing over the eastern half of Lake Superior this evening ends not too long after midnight, although some moderate freezing spray could be seen still across the lake into Sunday. However, with a cold front moving down from northern Ontario late tonight, expect winds to begin increasing from the W/WSW early Sunday morning ahead of the front, becoming gales of 35 to 40 kts by around noon EDT. However, when the cold front moves across the lake Sunday evening, expect the gales to quickly die down, with north to northeasterly winds of 20 to 25 kts becoming dominant across the lake late Sunday night. As a weak shortwave moves through the UP and northern Lake MI Monday, expect winds to remain northeasterly at 20 to 25 kts over the far western lake before lightening up to around 20 kts or less Monday evening. However, as a low pressure system over the Central Plains Tuesday lifts into MN Tuesday night, expect winds to pick up again from the east, with gales of 35 to 40 kts being possible over the far western lake. As the low moves through the lake Wednesday, expect the higher winds to move over the eastern half of the lake before the cold sector of the low brings northwesterly winds of 20 to 25 kts back across the lake Wednesday night into Thursday. Moving into next weekend, expect winds to be fairly light. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Lakeshore Flood Advisory until 2 AM EDT Sunday for MIZ005>007. Winter Weather Advisory until 8 PM EDT this evening for MIZ005>007-013-014-085. Lake Superior... Heavy Freezing Spray Warning until 8 PM EDT /7 PM CDT/ this evening for LSZ162-240>242-263. Gale Warning from 11 AM EDT /10 AM CDT/ to 8 PM EDT /7 PM CDT/ Sunday for LSZ162-242>244-263-264. Heavy Freezing Spray Warning until 2 AM EDT Sunday for LSZ243>251-264>267. Gale Warning until 8 PM EDT this evening for LSZ243>248-264-265. Gale Warning until 2 AM EDT Sunday for LSZ249>251-266-267. Lake Michigan... None. && $$ SHORT TERM...Rolfson LONG TERM...TAP AVIATION...Voss MARINE...TAP
Area Forecast Discussion
National Weather Service Blacksburg VA
856 PM EDT Sat Mar 18 2023 .SYNOPSIS... Gusty winds are expected tonight behind a cold front. Much colder air will move in overnight and Sunday. Even colder temperatures are forecast for Sunday night. Temperatures increase to above normal by Tuesday, becoming very warm by Thursday. The next widespread chance of rain may come Friday. && .NEAR TERM /THROUGH SUNDAY/... As of 845 PM EDT Saturday... ...Front moving through ushering in cold and gusty weather... Radar shows echoes associated with a frontal passage, but so far not seeing anything reach the ground with dry air still in the low and mid levels. The lowest cloud deck is around 6kft and should be low enough to produce some seeder-feeder type snow showers for the Greenbrier Valley, with a few sprinkles or flurries downwind into the overnight hours. Did increase wind gusts just a bit to 15-25 mph for the valleys and 25-35 mph for the ridges as the front moves through and bumps up mixing heights for a few hours. Winds should decrease closer to the 10-15 mph range by morning. Still expecting very cold wind chills on the mountains, ranging for 0 to +10F in the valleys, and as low as -12F on top of the ridges. As of 445 PM EDT Saturday... Colder with light mountain snow and flurries/sprinkles...winds lowering some overnight... A cold front was entering the northwestern sections of the forecast area, accompanied by plenty of altocumulus and light snow showers. Expect these clouds to spill into the rest of the region tonight as the front continues pushing SE. After looking at the snow squall parameters from the NAM and HRRR tonight, have added either snow flurries or a cold rain for a few hours this evening. It will be plenty cold (-8 to -10C at 850mb) for upslope showers to drift to or even past the Blue Ridge, so we may see some light sprinkles/flurries reach as far south as Boone to Roanoke to Lynchburg, resulting in a few hundredths precip at most. Also adjusted snow ratios and thus snow amounts tonight for the Greenbrier Valley. Just an increase of a few tenths, giving max snow amounts just under an inch for the northeastern part of the Greenbrier County. As of 200 PM EDT Saturday... Cold and windy with light mountain snow... With the cold front safely to our east, most areas have broken to partly cloudy skies thanks to the dry air. Later this evening into the overnight period, as the upper trough associated with the front makes its pass over southwest VA, winds will have a slight resurgence in strength and induce some upslope clouds for most of the CWA, and some light snow showers/flurries along the western slopes of the mountains. It will only be for a few hours, and accumulation will be scant. Most will see no accumulation or a dusting, and the higher elevations of Greenbrier County, WV could see up to an inch. Winds will gust between 25-35 MPH in the mountains overnight, and up to 25 MPH for the rest of the CWA, with weaker winds towards Southside VA. With low overnight temperatures in the teens and low 20s overnight west of the Blue Ridge, wind chills will be in the teens and single digits. Some limited portions of ridgetops and peak elevation locations above 3500ft could experience a brief period of wind chills below zero. These spots are the exception rather than the rule for this forecast period though. East of the Blue Ridge, overnight lows will be in the mid 20s/low 30s. On Sunday winds will start to calm and the skies will clear and make way for considerable sunshine. Things will be slow to warm up with many west of the Blue Ridge not getting out of the 30s, and east of the Blue Ridge high temps just getting into the mid 40s. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... As of 151 PM EDT Saturday... Significant cold to start Sunday night, then temperatures moderate into Tuesday. Closed upper low near New Brunswick Sunday night will lift northeast into the Atlantic ocean by Tuesday. Trailing band of vorticity will result in some high clouds Sunday night into Monday. A more zonal flow aloft establishes Monday into Tuesday night. At the surface, high pressure will build across our region and shift east offshore by Tuesday night. Low temperatures Sunday night will be very cold with readings from the single digits to the lower 20s. PWATs drop to 0.05-0.10" by Monday morning, and close to the climatological daily minimum recorded for the day at RNK. High temperatures will remain below normal from the mid 30s in the mountains to around 50 degrees in the Piedmont. Low temperature Monday night will generally be in the 20s. Clouds increase Tuesday allowing temperatures to moderate to highs from the mid 40s in the northwest mountains to near 60 in the Piedmont. Skies become cloudy Tuesday night as a cold front approaches from the west. Low temperatures Tuesday night will range from the lower 30s in the west to the mid 30s in the east. Confidence in the Short Term Forecast is high. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 151 PM EDT Saturday... Much warmer with showers possible especially late in the workweek, then drier for Weekend. High pressure over the Gulf of Mexico build north across our region Wednesday into Friday. With rising heights temperatures will moderate Thursday and Friday. High temperatures will be warm with readings in the 60s and 70s. Several shortwaves pass to our north and may bring some clouds and a few showers. Models continue to have differences in timing. However, southeast West Virginia has the best chance for showers in the Medium range. The first opportunity for rain will be Wednesday. Confidence is moderate for the long term forecast. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/... As of 840 PM EDT Saturday... Gusty NW winds are developing along and behind a cold front which is moving through this evening. Expect gusts to 20 kts for the valleys, and 25 to maybe 30 kts for a few hours in the mountains. Winds decrease some by daybreak as mixing weakens for a few hours. VFR conditions will remain in place for most TAF sites through the TAF valid period with the exception of BLF/LWB which may drop to MVFR in snow showers. Expect the mountain clouds to hang on towards 15-18Z Sunday before clearing. .Extended Aviation Outlook... Winds will subside completely Sunday night. Confidence is high that good flying weather will continue through Monday and Tuesday. Clouds will increase by Tuesday night as a warm front approaches from the west to bring a chance of rain showers and sub-VFR conditions on Wednesday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...SH NEAR TERM...SH/VFJ SHORT TERM...KK LONG TERM...KK AVIATION...SH