Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/09/21

National Weather Service Albany NY
946 PM EDT Sat May 8 2021 .SYNOPSIS... An elongated trough of low pressure will slowly migrate east of the region tonight. A developing storm system across the central and southern Plains States will approach later Sunday. Periods of rain are expected by Sunday evening and continue through the night. Conditions improve slowly on Monday with seasonable cool weather and perhaps some showers, mainly for the higher terrain. && .NEAR TERM /THROUGH SUNDAY/... Upper system slowly exiting as upper dynamics and low level forcing weaken. Showers are down to isolated in coverage and should be dissipated late this evening. Clouds are gradually breaking up in central NY and the breaks are building east. So, between midnight and daybreak, eastern NY should see some breaks in the clouds and western New England should see breaks by daybreak. Light winds and the breaking up of the clouds should support a steady cooling of temperatures, especially after midnight. Not including fog but some areas cold see fog depending on how much clearing we get and if temperatures reach dew points for a considerable amount of time. Just minor adjustments to the temperatures, rain chances and sky cover through the night. Previous AFD has a few more details and is below... PREVIOUS DISCUSSION: Deformation axis, inverted surface trough, extended from the northwest hills of Connecticut into the Catskills and Herkimer County. Some showers were attempting to develop to the east and northeast of Albany which was tied to a more diurnal cycle along with a little elevation boost to the convective potential. HRRR at the moment appears rather too robust with the forecast potential this afternoon with the HREF CAMS members a bit more realistic. So we will keep PoPs into the chance-scattered categories for the balance of the late afternoon into the early evening hours. Due to rather chilly temperatures this afternoon across the higher terrain of the Dacks and Catskills, with sunset we would not be surprised to see a little wet snow mix in before the departure of the precipitation. Variable cloud cover can be expected across the CWA with better chance for some clearing south of Albany with northwest winds aiding in downsloping off the Catskills. Some patchy fog will be possible where the rain was more prevalent earlier today as overnight lows dip back into the 30s across the terrain to around 40F for the Hudson River Valley locations. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... Mothers Day (Sunday)...Fairly good consensus for a dry yet cool for the month of May standards. Any sunshine we are able to soak in during the morning will become increasingly filtered by an increase in cloud coverage. As seen in the upstream H2O vapor loop, an elongated area of moisture extending from the Tennessee Valley and northwestward into the Dakotas which leads to the upper low over Montana will be approaching. 12Z NCEP Model Suite and international guidance have come into better agreement with the onset of precipitation during the afternoon from southwest to northeast. An enhanced area of rainfall is forecast to develop south of I90 by sunset with impressive FGEN and isentropic lift. Otherwise, look for light rain to evolve after 18-21Z timeframe Sunday. Sunday night...Surface wave is forecast to track east-northeast, south of I80 corridor, with periods of light rain across the region. The heaviest rainfall appears to fall south of I90 where combination of best H850-700 FGEN, isentropic lift and divergent q-vectors aloft are progged to occur. Here, rainfall amounts could approach three quarters of an inch with values near two- tenths north of I90. It will not only be damp but rather chilly with overnight lows into the 30s across the higher terrain to 40-45F for valley locations. Monday into Monday night...Overall a drier weather pattern as the surface wave tracks off the New England coastline in the morning hours. Then a cold front will approach and clear our eastern CWA Monday evening. H850 temperature hover just above 0C during the daylight hours then in the wake of the frontal passage drop below zero by sunrise Tuesday morning. If skies are able to clear and winds decouple, could see some valley areas get close to frost advisory. So only slight chance PoPs for mainly the terrain Monday then with the passage of the cold front some wet snow may mix in across the Dacks with some Lake Ontario contributions. Highs mainly into the 50s on Monday then lows into the 30s with around 40F for Hudson River Valley locations. && .LONG TERM /TUESDAY THROUGH SATURDAY/... The long-term forecast period will feature cooler than normal temperatures with a couple of upper troughs that will serve as the pre-dominant play makers during this period. The weather pattern also looks mostly dry/tranquil through the period. We start off the period on Tuesday with a pretty stout 540 mb upper low moving over the area from southeastern Canada. Thermal profiles aloft associated with this upper low will be pretty cold for this time of year with 850 mb temperatures ranging between -2C to -4C, which is 1 to 2 STDEVS cooler than normal. In addition to the chilly conditions, some scattered showers are possible during the day on Tuesday as cyclonic vorticity advection and differential heating in the boundary layer increases. Given the dynamics in place, some of the showers could be convective, especially during the peak diurnal hours. At this stage it appears that higher elevation areas along and especially north of I-90 will be most favored for showers on Tuesday. Some of the highest peaks of the SW ADKs could see a rain/snow shower mix. Most areas within our cwa (especially along the valley and south) should remain dry. Breezy northwest winds will be the other story on Tuesday as well. Increased height falls aloft and incoming cold air advection associated with the aforementioned 540 mb upper low will cause for a tightening of the pressure gradient. This will allow for breezy northwest winds at the surface. The synoptic and topographic setup could favor a channeling of breezy northwest winds down the Mohawk Valley into the Capital District and into the Berkshires. At this stage of the game, it appears that winds could gusts as high as 25 kts in this zone during the day on Tuesday. Tuesday night colder air moves over the region as any leftover rain/snow showers come to an end. Overnight low temperatures will be something to monitor in the days ahead given that levels could approach/near frost or freeze territory. This is of concern given that the growing season has begun most places. That said, winds could be the saving grace as winds will only let up a little Tuesday night with gusts approaching 20 kts. Again this will be something to keep watch on in the days ahead. Drier weather conditions for all return Wednesday as a broad 1028 mb surface high pressure system builds into the region from the west. Beyond Wednesday, deterministic forecast models diverge on the evolution/overall handling of the weather pattern, particularly with the aforementioned surface high pressure system and a storm system over the southern U.S. Eventually, the storm system over the southern U.S. will track northward towards our area. The question remains when and how far west will it track along the East Coast to potentially affect our area. The 12z GFS model is quickest/most bullish with precipitation chance over our area, while the 12z ECMWF/CMC models are more slower and more conservative with precipitation chances (keeping the track of the storm system furthest east). The suite of ensembles support the possibility of precip as well with again the GEFS being the most aggressive. One item to note is that run to run trends have scaled back for all models and their ensembles precipitation chances and amounts. That said, have kept just low grade 20-30% PoPs Thursday through Friday. Forecast models advertise another storm system approaching from the central U.S. over the weekend into early next week timeframe. Given the amount of uncertainty in the medium range, have only low grade PoPs through the remainder of the extended period. As far as temperatures, as mentioned earlier, anomalies will run cooler than mid May standards for the balance of this period. While our normal highs for this time of year are in the upper 60s and lows in the upper 50s, projected daytime highs during this period will range from the mid 50s to mid 60s (cooler higher elevations) and nighttime lows will mostly be in the 40s especially in the valleys (cooler higher elevations). && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... Upper system exiting and showers are expected to end through this evening. VFR ceilings will prevail at all TAF sites through the evening. There are some breaks in the clouds in central NY that are building east. Ceilings should break up between midnight and daybreak at KALB, KPOU and KPSF but KGFL may see ceilings most of not all of the night. There could be intervals of ceilings in the MVFR range at KGFL between about 08Z-12Z. Not including fog but if there are enough breaks in the clouds to allow temperatures to reach dew points for a considerable amount of time, some fog could form but chances too low to include until near term trends can be monitored. After about 12Z, just a few clouds well above 3000 feet into the afternoon. By about 20Z, the next system approaches and the leading edge of ceilings just above 3000 feet spread across the region. SOme patchy rain could approach KPOU and KPSF, so including VCSH there after 20Z. West to northwest winds at less than 10 Kt this evening become near calm by daybreak. West winds Sunday morning at less than 10 Kt shift to southwest by around 20Z. Outlook... Sunday Night: High Operational Impact. Definite RA. Monday: Low Operational Impact. Slight Chance of SHRA. Monday Night: No Operational Impact. NO SIG WX. Tuesday: Moderate Operational Impact. Breezy. Chance of RA. Tuesday Night: No Operational Impact. NO SIG WX. Wednesday: Low Operational Impact. Breezy. NO SIG WX. Wednesday Night: No Operational Impact. NO SIG WX. Thursday: No Operational Impact. NO SIG WX. && .FIRE WEATHER... Showers will slowly come to and end tonight as the passage of the weak low pressure slides east of the region. Overnight RH values range between 75 and 95 percent with a westerly wind less than 10 mph. The RH values fall between 30 and 50 percent Sunday afternoon, with those lower values to the northeast of Albany. Otherwise should be a generally dry day until late in the day. Chances of rain increase as the next low pressure system approaches. The winds to be west to southwest at 5 to 15 mph. Periods of rain expected Sunday night with likely a soaking rainfall south of I90. && .HYDROLOGY... Widespread hydrological issues on the main stem rivers are not expected into the middle of next week. Showers will be slowly coming to an end this evening as low pressure tracks away from the region. Another chance of rain with light to moderate amounts arrives late Sunday through Monday. Total rainfall may vary from two tenths of an inch to a half or three-quarters of an inch over the HSA with the higher totals from the Capital District south and east. 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...None. MA...None. VT...None. && $$ SYNOPSIS...BGM NEAR TERM...BGM/NAS SHORT TERM...BGM LONG TERM...Evbuoma AVIATION...NAS FIRE WEATHER...BGM/Wasula HYDROLOGY...BGM/Wasula
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1157 PM EDT Sat May 8 2021 .AVIATION... A mix of mid and high clouds over Lower MI thickens and lowers during the late night before rain moves in along the IN/OH border toward sunrise. Light rain initially allows VFR conditions to hold on for a few hours during the early morning followed by a quick transition to MVFR as rainfall rate increases. This mainly affects the DTW corridor and likely up to PTK while just brushing the FNT region with some sprinkles during the afternoon. The northern edge of the pattern stops before reaching MBS and then begins pulling away to the south and east. The diminishing trend in coverage and intensity continues through late afternoon with rain ending across the entire area by 00Z Sunday evening. For DTW... High clouds thicken and lower during the late night before rain begins shortly after sunrise. A quick transition to MVFR occurs as the rain intensity increases around mid morning. Conditions could also briefly touch IFR during the peak rain intensity within a couple hours of 18Z. .DTW THRESHOLD PROBABILITIES... * High for ceiling 5000 feet or less mid morning into late afternoon. && .PREV DISCUSSION... Issued at 948 PM EDT Sat May 8 2021 UPDATE... Evening satellite imagery and surface observations indicate afternoon cumulus lifted and settled into an 8000 ft broken layer over the Tri Cities and northern Thumb region. The cloud trends indicate a few more hours of cushion are likely before any strong radiational cooling occurs in that area. The mention of patchy to a few areas of frost is looking good before high clouds thicken later in the night. Looking farther ahead late tonight and Sunday, textbook cyclogenesis is ongoing on the lee side of the Rockies through the central Plains. It is a large low pressure system that already has a generous supply of Gulf moisture fueling a wide swath of showers and thunderstorms to the north and east of the low track. Moisture transport into the low and mid levels of the leading warm front will be enhanced by the strengthening nocturnal low level jet later tonight and Sunday morning to continue fueling convection roughly in the surface to 850 mb frontal zone. Thunderstorms in this pattern are expected to remain south of the Ohio border but the northern fringe of showers reaches across into Lenawee and Monroe counties by sunrise. The latest runs of the HRRR, RAP, and the 18Z NAM help with some refinement of onset timing and additional sharpening of POPs on the north flank of the pattern. The 18Z NAM collapsed the spatial scale of elevated convection in its QPF footprint compared to the 12Z run while the 00Z HRRR adjusted slightly farther north compared to its afternoon runs. Together, these model trends suggest keeping POPs high for a late night onset toward the Ohio border while delaying the northward expansion by a couple hours during the morning. The 700 mb frontal zone is still too strong, especially with a boost from the upper jet over the northern Great Lakes, to rule out higher based showers reaching the M-59 corridor by late morning and then brushing the I-69 corridor during the afternoon. Other than the above mentioned timing refinements, today`s afternoon forecast package remains fully on track for Sunday with categorical POPs in the Detroit metro area tapering to chance north of I-69 and then dry north of the Tri Cities to northern Thumb. PREV DISCUSSION... Issued at 339 PM EDT Sat May 8 2021 DISCUSSION... Seasonably cool early May environment firmly entrenched again this afternoon, owing to the perpetuation of higher amplitude troughing featured south of a closed mid level circulation positioned near Hudson Bay. These lower mid level heights briefly ease northward for latter half of the weekend period, as attention shifts to lower amplitude shortwave energy of pacific origin now ejecting into the plains. Blossoming corridor of mid level warm/moist air advection will emerge tonight within the north/ne flank of the resulting low level cyclone, the initial stages noted locally via a steady increase in high based cloud from south to north overnight. This will place a definitive ceiling on nocturnal cooling potential, particularly south of the I-69 corridor. Larger window of open sky supports lows of mid 30s north, with readings across the south in the vicinity of 40 degrees. Mid level frontal zone lifts northward into southeast Michigan late tonight and early Sunday, remaining anchored over southern sections of lower Michigan throughout the daylight period. Aggressive period of deep layer saturation will commence along the frontal slope, anchored initially by strong system relative isentropic ascent. Frontal forcing will increase with time as the boundary intersects the right entrance region of the upper jet max fixated within the height fall center looming to the north. Magnitude and duration of forcing maintains a high probability for an all day, solid soaking rainfall event south of the M-59 corridor. Rapid decline in both forced ascent and moisture quality with northward extent suggests a sharp northern edge to the gradient for meaningful precipitation - latest model guidance offering the I-69 corridor as this line with rain chances tailing off over the Saginaw valley and northern thumb. Daytime heating potential certainly muted given rainfall expectation and a northeast gradient - a raw day as temperatures linger in the middle and upper 40s many locations outside of the far north. Hudson Bay low will slowly eject south-southeast into the eastern great lakes during the early week period. Subsequent height falls arrive locally Monday, effectively reinforcing the cooler resident thermal profile within prevailing low level northwest flow. Diurnal steepening of lapse rates could yield a shower or two during peak heating across central lower mi, but absent of greater moisture depth or more tangible forcing the prospects appear limited. Highs locked in the 50s. Emergence of deeper layer northwest flow contained within the broader mid level cyclonic periphery supports a period of cold air advection Monday night and Tuesday - low level thermal trough early Tue afternoon characterized by 850 temps of -4 to -6C. Once again highs should arrive a solid 10+ degrees below average. Modest warming trend during the late week period, as upper heights gradually recover. Dry and stable profile Wednesday as low-mid level ridging briefly governs conditions. Loosely organized troughing then appears to take residence Thu-Fri, so potential for conditions to become more unsettled again within this window. MARINE... High pressure will continue to remain in place across the central Great Lakes the remainder of today with generally dry conditions except for a few stray showers across portions of southern Lake Huron and Lake St. Clair. The high pressure will shift slightly north as low pressure tracks eastward from the central Plains towards the northern Ohio Valley late tonight into Sunday, bringing widespread rainfall to the southern half of the local waters. Light and variable winds will reorient northeasterly in response to the low pressure system and become moderate in strength, especially across western Lake Erie, where the tightest pressure gradient will help yield gusts around 25 knots during the day Sunday and building wave heights of 3-5 feet posing hazardous small craft conditions. Winds will back more northwesterly and become more moderate in strength across all waters for early next week as high pressure becomes reestablished across the Great Lakes. HYDROLOGY... Rain will increase in coverage across lower Michigan Sunday morning as a low pressure system tracks through the Ohio valley. Widespread rainfall expected through the daylight period from the M-59 corridor southward, with a period of lighter rain reaching northward into the I-69 corridor. Highest rainfall totals will exist near the Ohio border, where amounts upwards of one inch will be possible. Rainfall totals generally between one quarter and one half inch will occur across the Ann Arbor and metro Detroit regions, with under a quarter of an inch north of M-59. This rainfall is not expected to result in flooding concerns. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...Small Craft Advisory from 10 AM to 10 PM EDT Sunday for LEZ444. && $$ AVIATION.....BT UPDATE.......BT DISCUSSION...MR MARINE.......IRL HYDROLOGY....MR You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Quad Cities IA IL
702 PM CDT Sat May 8 2021 ...AVIATION UPDATE... .SYNOPSIS... Issued at 213 PM CDT Sat May 8 2021 A surface low is developing in the vicinity of the corner of NE Colorado, NW Kansas, and SW Nebraska this afternoon. A warm front extends east southeastward from the low towards Kansas City then southeastward to Memphis TN. Clouds have overspread Iowa, northeast Missouri into west central Illinois. A band of precipitation associated with FGEN forcing in the 850 to 500 MB layer stretches from FSD to IOW and then southeastward to MQB. Temperatures across the area were generally in the lower to mid 50s. AWG is the cool spot at 48 degrees with rain falling. && .SHORT TERM...(This Evening through Sunday) ISSUED AT 213 PM CDT Sat May 8 2021 Forecast Changes: 1. Rainfall amounts of 1 to 1.5 inches have expanded across to include all of the area for this storm system. The main forecast concerns were chances of precipitation and type. Model forecasts have trended southward with the track of the surface low moving it from northern Missouri to roughly the Interstate 80 corridor. Confidence still remains low on precipitation amounts and location. Models have consistently shown 850 to 500 mb FGEN overspreading the area late this afternoon into early Sunday morning. This in conjunction with shortwave trough moving across the area this evening in zonal flow aloft. This will provide strong forcing for precipitation across the area tonight into Sunday morning. Deep moisture will also be in place during this period. Expect showers to expand in coverage this afternoon this evening then warm moist air aloft will bring instability to the area south of Interstate 80 with the threat for isolated to scattered thunderstorms. There is no threat for severe storms today. There is one potential fly in the ointment for the heavier precipitation is if the convection expected across eastern Kansas into Missouri inhibits to the northward flow of moisture into the area which the amount of precipitation especially across the northern half of the area. Precipitation type: Some models have been showing dynamic cooling taking across the area tonight with the strong forcing in place and large dewpoint depression this afternoon before saturation wins out. This will cause the column to further cool. The NAM and HRRR are the coolest of these solutions with a change over to snow along the Highway 20 corridor and temperatures in the mid 30s during this period. Think that a mix of snow is more likely with slowly rising dewpoints but it will be close. Do think that a couple of hours of snow or a rain/snow mix is possible early sunday morning but do not expect any accumulations. An easterly wind will develop this evening with gusts of 20 to 30 knots or up to 35 MPH. This will result in a raw, cool night, across the area with falling precipitation. Low temperatures on Sunday morning will range from the upper 30s north of Interstate 80 to the lower 40s south. Precipitation will come to end from west to east Sunday morning. Skies will be partly cloudy by the end of the day on Sunday. Winds will diminish Sunday afternoon as the surface low passes to the south and east of us. A quick rebound in temperatures is expected as precipitation comes to an end on Sunday with highs in the lower to mid 50s. .LONG TERM...(Sunday Night through Saturday) ISSUED AT 213 PM CDT Sat May 8 2021 1. Temperatures are still a concern in the days ahead. While rainfall will not be significant, temperatures will continue to be well below normal, and will bring the threat for additional frost headlines to both Sunday night and Monday night in the forecast for this upcoming week. The pattern through Tuesday is dominated by a cold upper trof of low pressure, centered over the Great Lakes. This will keep our skies partly to mostly cloudy each day, and clear to partly cloudy at night, since much of the cloud over is diurnally driven on the west side of the trof. Highs given the strong sun angle will reach the upper 50s to lower 60s Monday and Tuesday, but the cold air dry air aloft will support lows in the 34 to 38 range Sunday and Monday night, allowing for the threat for frost, especially along and north of Highway 30. Some light showers may develop at peak heating Monday, but for now, I`ve left the forecast dry. It`s something to watch, and if the signal towards instability showers continues, we can add isolated/scattered showers on the next cycle. If they occur, they would not offer a significant QPF impact. The upper pattern shifts east somewhat by Wednesday, allowing for surface high pressure push towards the eastern Great Lakes. Light south winds and sunshine should return by Wednesday, with increasing southerly flow strengthening by late week. While our temperatures will rise, guidance continues to show mainly 60s and lower 70s, until Saturday, where mid 70s are expected. Over all, this should be a pleasant weather week after Monday. && .AVIATION...(For the 00Z TAFS through 00Z Sunday Evening) ISSUED AT 654 PM CDT Sat May 8 2021 Poor aviation conditions are expected tonight into early Sunday morning as widespread light to moderate rain drops ceilings and visibilities to MVFR/IFR. The rain could become briefly heavy at times south of DBQ and there is the potential for embedded thunderstorms. In addition to the rain, gusty E to NE winds between 20 to 30 kts are anticipated tonight. Conditions will improve through the mid to late morning on Sunday. && .HYDROLOGY... Issued at 1037 AM CDT Sat May 8 2021 A river flood watch has been issued for the La Moine River at Colmar due to the current forecast of 1 to 2 inches falling in the basin. There is lower confidence at this time in the exact placement of heavy rain as well as rainfall amounts. While strong lift will be in place north of the warm front tonight into Sunday across Iowa and northwest Illinois, severe thunderstorms across Missouri late this afternoon into this evening may disrupt the flow of moisture into the area and limit the amount of rain that we receive. Given the current dry conditions, the placement of the highest rainfall amounts will dictate which points see within bank rises. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ SYNOPSIS...Cousins SHORT TERM...Cousins LONG TERM...Ervin AVIATION...Uttech HYDROLOGY...Cousins
National Weather Service Jackson KY
1132 PM EDT Sat May 8 2021 .UPDATE... Issued at 1131 PM EDT SAT MAY 8 2021 Made some adjustments to precip chances for the rest of tonight, based on the latest radar trends and HRRR and GFS model data. PoPs overall were decreased with the main focus of rain the rest of tonight along and north of the Mountain Parkway. Made some small adjustments to temperatures as well, but nothing earth shattering. Did have to take down Somerset`s low for tonight as they had already fallen below the previously forecast min as of 3Z. Also issued an update to the NPW simply to give the mid-shift until toward the end of their shift to update it again. The information in the NPW stayed exactly the same. All updated produces have been issued. && .SHORT TERM...(This evening through Sunday night) Issued at 505 PM EDT SAT MAY 8 2021 Energy rounding the base of a negatively tiled trough over the northern Rockies will break away and track eastward across the CONUS in rapid fashion today. This disturbance will reach the lower Ohio Valley by tonight. Rockies lee side surface low will strengthen and move eastward in response, lifting a warm frontal boundary northward across eastern Kentucky tonight. This will leave eastern Kentucky within the warm sector of this storm system leading up to cold frontal passage Sunday night. Gradient winds will increase considerably ahead of the cold front that is expected to pass through eastern Kentucky Sunday evening into Sunday night. Operational models indicate that H850 winds will increase within a LLJ to between 50 and 60 kts while H950 winds increase to around 35 kts. Steep boundary layer lapse rates (>7 C/kg) and reasonably deep mixing (up to 5 kft AGL) over to portions of eastern Kentucky could help mix down higher wind gusts of around 35 to 40 mph. However, substantial mid/high level cloud cover may help mitigate the deeper mix down of higher wind gusts as well. Decided to try and give a little heads-up to our boaters and went with a Lake Wind Advisory for Cave Run and a special weather statement for the remainder of the area. Will need to monitor upcoming runs in case the Lake Wind should be expanded to the Lake Cumberland region as well, where wind gusts appear more marginal. SPC has a good portion of our area in a marginal risk for severe thunderstorms Sunday. Cloud cover dampens potential instability across the area and timing of the front into eastern Kentucky Sunday evening into Sunday night means prime heating will be over. MUCAPES of only 500-1000 J/kg and effective shear of 30-35 kts could be enough for a few strong storms to fire, possibly an isolated severe or two as well. As stated before, boundary layer lapse rates are quite steep, mainly across the southeast portion of the forecast area. But mid/upper level lapse rates are marginal, indicative of the lack of over instability. At this point, feel overall threat to be fairly minimal. However, this could change should we see more insolation and better surface based instability. Obviously, with the strong wind fields in place, gusty winds in and around any showers or thunderstorms would be the greatest hazard, which is why SPC decided to carry a marginal threat...i.e. due to convectively augmented wind gusts to gradient winds. .LONG TERM...(Monday through Saturday) Issued at 505 PM EDT SAT MAY 8 2021 Things start off pretty rainy initially on Monday morning. The active weather of the short term will be winding down some as the surface low continues east and drags the cold front through the remaining southeastern half of the area. Any thunderstorms should be done at this point and any ongoing rain showers will be pushing down to the south through the day. High temperatures Monday will stay quite cool, especially when compared to Sunday, under the northwesterly to northerly flow behind the front, and generally top out in the low 60s. High pressure then nudges in across the Ohio Valley as the front exits, and skies start to clear some late, at least in the northern parts of the CWA close to the center of the high. The rain has generally pushed south of the area at this point. However the NAM does bring some rain back into the far southern counties late Monday night with a small passing wave of energy aloft. Even with it being somewhat consistent in this solution, it is a bit of an outlier and ensemble probabilities are low. So, kept PoPs just barely under slight chance due to reasons just mentioned and to keep more consistent with neighbors. Lows Monday night are chilly in the low 40s. Cool and dry weather will continue through mid-week as high pressure remains over the Ohio Valley. Tuesday night is cold in particular, dipping down into the upper, and possibly mid, 30s. A few valley locations, particularly further north, may be able to squeak out temperatures low enough to support a possible light touch of frost, but am not super confident in that at this point, and trends will need to be monitored. Going into Thursday, there`s still some disagreement remaining. In general, there`s a wave that nudges over from the Mississippi Valley over the day Thursday. The GFS in particular is a bit sharper with this feature along with a slightly stronger wave at the surface, and brings rain back into the area Thursday afternoon. The ECMWF and Canadian have the upper level wave weaker and have precip staying to our south. Ensembles appeared to lean slightly more towards the ECMWF and Canadian in terms of the pattern as a whole, and in terms of precipitation specifically, probabilities are not super high, but not low enough to be ignored. At this time, the forecast has rain moving in Thursday afternoon and exiting Friday. A few thunderstorms are also possible Thursday afternoon, though this is conditional on there actually being rain at all. There looks to be a break in the rain Friday, before another system eventually moves in sometime over the weekend. Temperatures stay cool generally, but gradually modify through the second half of the period. Overall, for the late part of the work week, agreement is poor, and relied on the NBM for this time frame. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) ISSUED AT 727 PM EDT SAT MAY 8 2021 Mid and high level clouds will yield BKN to OVC CIGs this evening and tonight, as a sluggish boundary returns to the north overnight as a warm front. This warm front will drop CIGS to around 6K AGL with scattered rain showers developing tonight. Showers should end as sunrise approaches, with CIGS lifting back up to 100 AGL or higher. There could even be a short window of time where skies scatter out Sunday morning, with perhaps BKN high clouds left over. A low level jet will increase across the region late tonight with the warm frontal zone, leading to a period of about 4-6 hours of non- convective low level wind shear, likely from 9 to 15Z. Surface winds will increase to between 10 and 15 kts from the southwest from late morning onward, as stronger winds aloft mix down. Gusts to around 25 kts will be possible at times, the result of an approaching cold frontal system Sunday, which is expected to reach eastern Kentucky by Sunday evening. SYM may begin to be affected by showers and a few storms by around 19Z, as the cold front approaches. Showers and storms will likely not begin affecting SME, LOZ, and JKL until near the end of the TAF period. && .JKL WATCHES/WARNINGS/ADVISORIES... Lake Wind Advisory from 1 PM to 7 PM EDT Sunday for KYZ051-052- 060-106. && $$ UPDATE...AR SHORT TERM...RAY LONG TERM...HAS AVIATION...AR
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
917 PM CDT Sat May 8 2021 .UPDATE... 917 PM CDT Going forecast is in generally good shape this evening, with only some minor adjustments made based on observational and recent model trends. Primarily, tightened up the sharp QPF gradient along the I-88 corridor, brought some slight thunder chances farther north out west through midnight, and shifted greatest potential for a period of rain/wet snow slightly south late tonight into early Sunday morning. Precipitation continues to overspread the forecast area at mid- evening ahead of a strong 995 mb surface low analyzed over central Kansas. A surface warm front stretched from northeast KS southeast into far western TN, with an impressive low-mid level baroclinic zone within the elevated frontal zone north of the surface boundary. Strong frontogenesis was occurring across IA and into central/northern IL within this zone, with 35-45 kt 850 mb return flow providing moisture transport/convergence and producing precipitation into the forecast area. Several mPING reports of graupel had been noted upstream across IA as precip developed into dry low levels, though largely all rain at the surface as the column saturates. Has also been persistent thunder along and just north of the U.S. 30 corridor across IA this evening, along the northern periphery of elevated MUCAPE plume. Model trends, including 18Z ECMWF and several consecutive runs of the HRRR, have continued to depict a tight gradient in expected rainfall totals along and just north of the I-88 corridor across northern IL. Going forecast trends for precip timing/pops appear to be in good shape, though did tighten up the QPF gradient across far northern/northeast IL with lowered amounts especially toward the IL/WI border in the northern suburbs, and increased amounts immediately south of I-88. Still expecting 1-2 inch amounts there, with isolated 2+ amounts possible. Lightning trends have been decreasing recently as elevated convection approaches the Mississippi, but based on proximity did take slight chance thunder potential into the I-88 corridor and across our southwest counties this evening. This should slide southeast with time, with areas mainly south of I-80 favored for embedded thunder later tonight. Other adjustment was to shift our narrow axis of potential rain and snow mix (or even briefly changing to all wet snow pre-dawn) slightly south about a half county or so into the I-88 corridor west of Chicago late tonight. Again successive HRRR runs and the 18Z ECMWF continue to highlight that area for this potential, with HRRR and RAP forecast soundings both depicting cooling of the column and WBZ heights lowering below 1500 ft AGL along the northern periphery of the heavier precipitation shield during the pre-dawn hours. Continued to mention the potential for some slushy accums from roughly the Forreston and Dixon areas through Rochelle and into DuPage/northwest Will counties. Blustery east flow off the lake should help keep surface temps a little warmer farther east into the metro area and reduce potential for any accums on grass or elevated surfaces. Otherwise, no changes to going forecast. Updated digital and text products already available. Ratzer && .SHORT TERM... 245 PM CDT Through Sunday... Mother`s Day will feature weather conditions more characteristic to St. Patrick`s Day, with cloudy, blustery, and very wet conditions for the morning. The main forecast messages are: * Rain onset spreads from west-to-east this evening with possibly brief ice pellets mixing in at first * Rain increases in intensity late this evening into overnight, with some embedded thunderstorms possible mainly south of I-80 * Potential for a mix with snow has increased for primarily a portion of north central Illinois and eastward toward the Fox River Valley part of northeast Illinois late tonight into early Sunday morning * Rainfall of 1 to 2 inches for most locations along/south of I-88, with isolated over 2 inches possible, though flooding threat should remain low * Gusty northeast winds keep temperatures down through Sunday, even as rain ends west to east late morning into afternoon A lot to unpack for the rest of this weekend. Looking upstream on GOES-16 water vapor imagery shows a well-defined, strong upper low over Montana moving southeast bringing with it 100 meter 500 mb height falls. In still a somewhat split flow pattern, a 100 kt subtropical jet moving into the Central Plains ahead of this wave will result in a deepening surface low below 1000 mb into Missouri overnight. This should spread into an area of some coupled jet divergence over our region overnight into Sunday morning, resulting in the mid-latitude system overall maturing as it heads over Illinois/Indiana. The synoptic pattern is such that a rain shield should gradually blossom through the evening followed by a steady moderate to more heavy rain with the stronger upper forcing overnight into early Sunday. Model guidance is in decent agreement with this synoptic evolution, though some spread exists and given where we are located within the baroclinic leaf, a subtle difference in low track will alter the heavier QPF axis, the area where a few hour wet snow mix is favored, and the magnitude of the winds. Given a hefty footprint of convection anticipated over the Central Plains into Missouri River Valley tonight, this could result in a more south track within the model solution envelope, such as the RAP has been advertising and the 12Z ECMWF depicts. The HRRR has also trended ever so slightly south from its earlier solutions today. This is the more favored route, but a more north solution such as the 12Z NAM cannot be fully discounted yet. All model guidance agree on the strong mid-level baroclinic zone to our west (18C difference from LBF to MPX on 12Z RAOBs) tightening over the area tonight and a sharpened frontogenetic vertical circulation. This is a longer duration zone of such forcing and this is the zone most favored to see the heaviest rain rates on strong moisture convergence and ascent. It`s also along this where enough wet bulb cooling may occur to support snow. Given marginal low-level melting profiles (<10 J/kg of positive energy using a local revised Bourgouin technique) and upright instability predicted on an area of steeper 650-500 mb lapse rates, there likely will be an area that does change over. As mentioned earlier, there certainly is some wobble room where this is, but a consensus/middle ground solution is toward I-88. Warm surface temperatures will result in quite a bit of immediate melting, but if a band of instability-driven heavier rates persists for 2-3 hours as mainly snow, then could certainly see accumulation on at least grassy and elevated surfaces. While a tail of the solution envelope, f-gen magnitude events such as this can provide a mesoscale-level (multi-county scale) quick several inches. There have been a few CAMs run that have shown something like this, though seem to be much too robust in their efficiency of turning 100% QPF to snow, and at too high of ratio. Further east with increasing easterly winds off the warmer waters of Lake Michigan, the potential for snow drops into the heart of the Chicago metro as well as far northwest Indiana. South of I-80, more melting energy exists thanks to the proximity of the 850 and 700 mb lows passing closely by to the south. It is always a true challenge with predicting snow during these tail end of season events, as thermal profiles are marginal and present one striking failure mode. Also there could be enough moisture transport robbing from the south by daybreak to start reducing the precipitation rates by early Sunday morning to the point where overcoming the marginal low-level temperatures becomes quite iffy. The surface low looks to be due south of the area during the morning Sunday, and this is when the tightest pressure gradient and strongest winds are predicted. The 925 mb winds look to be around 35 kt, with the outlier NAM giving 40 to 45 kt. With some lake-induced steeper lapse rates and a slightly deeper boundary layer, some gusts to 40 mph may be experienced in the lake adjacent counties with the onshore flow. As a note regarding any lakeshore flooding concern, wind speeds over the lake are too low and the direction does not look to maximize the fetch, especially with lake levels having dropped over the past year. As the system departs east, rain will end from west-to-east over the region, with areas east of I-55 likely seeing some rain continuing into early afternoon. The cloud shield, precipitation, and winds will keep temperatures from climbing much at all on Sunday morning, with many areas likely hanging in the 30s through 10 to 11 AM. There should be some recovery in the afternoon, although highs should probably stay shy of 50 for many of those eastern CWA communities including Chicago. These will not be a record cold high temperatures for the day as those are low 40s for Chicago and Rockford. See the longer term forecast below for more brighter weather to discuss by later next week! MTF && .LONG TERM... 119 PM CDT Sunday night through Friday... As a surface high pressure system settles over the Great Lakes beneath upper-level northwesterly flow, most of next week looks relatively quiet. Sunday and Monday nights continue to look chilly with lows in the mid 30s supporting areas of frost away from the Chicago metropolitan area. Light winds and partly cloudy skies will then be a daily occurrence, with highs gradually warming from the mid to upper 50s Monday and Tuesday toward the mid to upper 60s by the end of the week. Daily lake breezes will hold lakeshore locations in the 50s, however. A few afternoon sprinkles or light rain showers can`t be ruled out from time to time as "wiggles" in the upper-level flow pass through. The upper-level pattern from the weekend onward looks decidedly spring-like with warming temperatures and chances for showers and thunderstorms. Borchardt && .CLIMATE... 330 PM CDT Some wet snow mixing in is possible at Chicago and more so Rockford late tonight and early Sunday morning. The last time Rockford saw snow in May was May 16, 2014 (trace). As for accumulating snow in May, the last time was May 10, 1990 (0.2 in.). The latest accumulating snow on record in Rockford is May 11, 1966. The last time Chicago (official site O`Hare) saw snow in May was May 2, 2005 (trace). The last measurable snow in May was May 5, 1989 (0.5 in.). The latest accumulating snow on record in Chicago is May 11, 1966. There have only been two Mother`s Days with snow in Chicago since Mother`s Day became official in 1908, and those were May 9, 1954 and May 8, 1960 (both traces). MTF && .AVIATION... For the 00Z TAFs... 624 PM...Primary forecast concerns include... Ifr cigs overnight/Sunday morning. Strong/gusty northeast winds overnight and Sunday. Rain developing this evening, ending late Sunday morning. Chance of snow early Sunday morning. Rain will spread across the area this evening and increase in coverage and intensity late this evening into the overnight hours, ending from west to east mid/late Sunday morning. There is likely going to be a sharp cut off to this rain which may be near a rfd/ dpa/ord line and there is some uncertainty for cigs along and north of this cutoff. Ifr cigs are expected to develop for much of the area overnight and continue through late morning Sunday, slowly lifting to mvfr and then to vfr during the afternoon. For now have maintained only tempo ifr cig mention for rfd/dpa/ord. There is a chance for a few thunderstorms overnight, but these are expected to remain south of the terminals. There may be a narrow axis of snow that develops along the northern portion of the rain axis, which would possibly be along a rpj/arr/igq/gyy line. There is quite a bit of uncertainty regarding the snow potential and for now opted to keep previous forecast mention at rfd/dpa, though some mention at mdw/gyy may be needed as trends emerge. Easterly winds around 10kts will slowly increase through the mid/ late evening with gusts into the 20kt range overnight. Winds will turn more northeasterly by daybreak when gusts into the upper 20kt range will be possible, only diminishing into the mid 20 kt range Sunday afternoon. These strong winds/gusts will end with sunset Sunday evening. cms && .MARINE... 245 PM CDT Strong east-northeast winds will develop over southern Lake Michigan late tonight and continue through midday Sunday. There is potential for gale force winds with this but that signal is somewhat muted, with the most favored outcome looking to be winds of 30 kt and possibly sporadic gales Sunday morning and early afternoon. This is supported by similar situations to that as forecast (analogs), which indicate around a 60% chance of 30 kt winds along the Illinois shore while less than 10% chance of 35 kt winds. Also the winds becoming more north-northeast Sunday afternoon into evening will continue wave action despite the wind speeds gradually diminishing. MTF && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744- LMZ745...4 AM Sunday to 4 AM Monday. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1053 PM CDT Sat May 8 2021 .UPDATE... Issued at 1045 PM CDT Sat May 8 2021 Updated to include 06z aviation discussion below. && .SHORT TERM...(This evening through Sunday night) Issued at 250 PM CDT Sat May 8 2021 The big winner today is dry air. 12z MPX sounding showed RHs just above h7 of less than 1%, so the baroclinic zone of forcing in place from western NoDak (where it has been snowing most of the day!) to southeast IA is doing nothing more than moistening the mid levels of the atmosphere locally. HRRR has been trending farther and farther south with the northern edge of the rain shield through the day and it is now looking like it doesn`t even make it as far north as the MN River in western MN. Still have categorical PoPs, but have them just confined to the I-90 corridor. Though we may not get much rain out of this, we are seeing ample mid/upper level cloud cover. These clouds will help keep temperatures tonight from falling into the 20s as they did this morning. There may be some clearing into central MN tonight, so temps near 30 are possible up there, but this is also where the growing season has not reached an advanced enough stage to need frost/freeze headlines, so for now, we have no frost freeze headlines. A one night break before they`ll likely be needed again Monday and Tuesday mornings. For Sunday, the GFS/NAM show a weak pressure trough working across the area, with afternoon showers developing along the boundary in southeast MN into adjoining portions of western WI. However, forecast soundings looks really dry, so think this is nothing more than a hint at a diurnal cu-field forming. Followed more the idea of the ECMWF with a dry forecast and a Mother`s Day that is a little on the cool side with highs in the 50s with a mix of clouds and sun. Sunday night, the big unknown is what happens with cloud cover. At the surface, high pressure will be moving in with light winds and dry conditions prevailing. This will be yet another opportunity to drop lows into the 20s and 30s, so another round of frost/freeze headlines may be needed depending on how potential mid/upper cloud cover impacts lows. .LONG TERM...(Monday through Saturday) Issued at 250 PM CDT Sat May 8 2021 More of the same to start this period on Monday and Tuesday with surface high pressure and the same cut-off low aloft aloft. This means dry conditions and below normal temperatures with highs in the mid 50s on Monday and low 60s on Tuesday. The pattern finally starts to change mid week as the cut-off low and surface high pressure move out. This leads to a more active pattern with a few shortwaves moving through the Upper Midwest. This first wave moves through late Wednesday/early Thursday, but this appears to be a rather week wave with little synoptic support provided so rain chances are low. The next chances arrives Friday into Saturday and this one could provide some more synoptic support and therefore some rain. Despite this wave being present in most members of the GFS and ECMWF systems there remains a wide spread in the strength of this wave and its associated QPF. So the chances of rain look better late week than mid week, but the spread remains high. For example among GEFS members QPF for this late week wave range from near zero to a half inch. There is however more clustering on the lower end such that confidence is higher in this being a light precipitation event. What remains more certain in this period is a gradual warming trend. After we bottom out on Monday with high temperatures only in the 50s, normal highs are in the upper 60s, temperatures will gradually warm up next week. Breaking out of the early week northerly flow pattern will allow temperatures to warm up to normal by the end of the week with both forecast and normal highs around 70. Looking ahead the rest of May looks more likely to be near or above normal rather than below normal on the temperature front at this point. && .AVIATION...(For the 06Z TAFS through 06Z Sunday night) Issued at 1045 PM CDT Sat May 8 2021 Solid VFR conditions expected throughout this TAF duration. High clouds will be prevalent throughout, with ceilings likely to be maintained overnight and potentially for much of Sunday. SE winds under 10 kt to start will go light/variable overnight before picking up 5-10kt Sunday from the north. KMSP...No additional concerns. /OUTLOOK FOR KMSP/ Mon...VFR. Wind N 10 kts. Tue...VFR. Wind N 5 kts. Wed...VFR. Wind SW 5-10 kts. && .FIRE WEATHER... Issued at 250 PM CDT Sat May 8 2021 A very dry airmass will remain in place through Tuesday. Afternoon humidities between 20 and 30 percent are expected daily through Tuesday. At this point, winds are not expected to be strong enough any day to meet Red Flag criteria, but the dry conditions will continue to lead to elevated fire weather conditions daily through Tuesday. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ UPDATE...JPC SHORT TERM...MPG LONG TERM...NDC AVIATION...JPC FIRE WEATHER...MPG
Area Forecast Discussion
National Weather Service Pueblo CO
327 PM MDT Sat May 8 2021 .SHORT TERM...(This evening through Sunday) Issued at 327 PM MDT Sat May 8 2021 Warm and windy across much of the area today, though changes have begun this afternoon as upper wave digs into the nrn Rockies and cold front drops south through the plains. Enough upward motion was associated with the wave to generate some high-based storms over the mountains this afternoon, though large t/td spreads were keeping precip light and confined to mainly the higher elevations. Surface front was roughly along a COS to LAA line as of 22z, and will likely accelerate southward this evening as convective outflows give it a boost. Instability increases behind the boundary, as dewpoints rise into the 30s/40s, suggesting a risk of some strong/severe storms over the far eastern plains into mid-evening. Severe wind will likely be the main risk given large downdraft CAPE (gt 1200 j/kg), and latest HRRR suggests cold pool/broad outflow boundary developing ahead of the storms, which may generate a period of blowing dust and low visibility mainly east of I-25 until sunset. Activity fades overnight, though clouds will increase along and east of the mountains toward morning as low level flow turns more e-se. On Sun, cool/moist air mass covers the eastern plains, with some isolated showers developing during the morning. By Sun afternoon, low level sly flow reappears along the NM border, with CAMs suggesting enough instability/shear for some strong/severe cells in Las Animas County where SPC has a marginal risk. Just enough instability elsewhere for a mention of thunder in the afternoon as weak convection develops over the ern mountains and I-25 corridor, though severe threat will be low given CAPE of only 100-300 j/kg away from the mountains. Max temps will be cooler area-wide, most pronounced cooling on the plains, where clouds and precip should hold readings even cooler than NBM numbers would suggest, especially along I-25. .LONG TERM...(Sunday night through Saturday) Issued at 327 PM MDT Sat May 8 2021 ...Potential for widespread precipitation event for plains and eastern mountains through early Tuesday... ...Possibility for significant snow accumulations above around 9000 feet in the eastern mountains... .Sunday night through Monday...Trough over the northern and central Rockies will progress eastward with cool and moist airmass over the eastern plains and into the eastern mountains. Models and ensembles show variations in the strength of the trough which will affect the amount of precipitation on the plains and eastern mountains. The models and ensembles generally fall into to camps. The GFS and GEFS mean have a sharper trough across the northern Rockies. The sharper trough has more southwest flow aloft with the 700 mb baroclinic zone remaining over northern Colorado. With a widespread overrunning event likely Monday into Monday night, the further northern baroclinic zone would tend to keep the heavier precipitation over northern Colorado. The EC, EPS and CMC have a weaker trough with the 700mb baroclinic zone remaining further to the south. As a result, the heavier band of QPF would be over southern Colorado. A quick look at the cluster analysis shows the general disparity between the models and their associated ensemble means for QPF Monday night into Tuesday. In the grids followed the WPC QPF and the NBM snow levels. The WPC QPF is good compromise for QPF totals, giving 2 day totals from around 0.6 to 1.2 inches of liquid. If the further south solution verifies, QPF totals could be higher. As for the burn scars, believe much of the precipitation will be stratiform with lower rates over a longer time period. The NBM snow level is a good compromise between the higher snow levels in the GFS/GEFS and the lower snow levels in the EC/EPS/CMC solutions. The NBM keeps the heavier snow mostly above 9000 feet. It could get cold enough Monday night for snow over the Palmer Divide with the grids currently having a few inches. In addition, the location of the baroclinic zone will affect the surface temperatures. The warmer GFS tries to mix out the Raton Mesa area Monday with warmer temperatures. The GFS tends to mix out the lower level cold air too quickly, even if the upper level solution verifies. As a result, I have cooler the temperatures Monday on the eastern plains in collaboration with DDC. Given the uncertainty with the solutions, that the heavier snow will be over the higher elevations, and most of the accumulations will be Monday and Monday night, will not issue any winter highlights at this time. .Tuesday...Upper trough starts moving east of the region with a cool upslope airmass on the plains. Expect some showers to continue on Tuesday over the eastern mountains and plains with generally light QPF amounts. .Wednesday through Saturday...Upper ridge builds over the region with a warming and drying trend. A weak disturbance may move into the region late in the week with some chances to showers or thunderstorms Friday and Saturday. NBM has silent to isolated PoPs with light QPF, which summarizes the pattern well. --PGW-- && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 327 PM MDT Sat May 8 2021 At KCOS, cold front moving through the terminal as of 22z, with n-ne winds gusting to 35 kts behind the front continuing into the evening. Risk of a vcts behind the front from 22z-01z, though with limited moisture, gusty and erratic winds will be the main features of any storms. Clouds will thicken and lower overnight, with MVFR cigs and a vcsh by 10z-12z Mon. Prolonged period of MVFR/occasional IFR cigs and periods of showers/isolated thunderstorms then likely through Sunday. At KPUB, gusty w-nw winds will shift to the n-ne behind a cold front 23z-01z. Clouds then thicken and lower overnight, with some MVFR cigs and showers/isolated thunderstorms likely from Sunday morning onward. At KALS, strong w-sw winds gusting to 30-40 kts may produce some blowing dust and brief periods of MVFR visibility into early evening, with perhaps a vcsh adding to wind speeds as well. Winds diminish with VFR conditions overnight and early Sunday. && .PUB WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 8 PM MDT this evening for COZ224. Red Flag Warning from 11 AM to 8 PM MDT Sunday for COZ224. && $$ SHORT TERM...PETERSEN LONG TERM...PGW AVIATION...PETERSEN
Area Forecast Discussion
National Weather Service Springfield MO
649 PM CDT Sat May 8 2021 .SHORT TERM...(This evening through Sunday) Issued at 235 PM CDT Sat May 8 2021 A warm front was lifting northeast through the area this afternoon. Breezy south winds with temperatures in the upper 70s to lower 80s were occuring southwest of Springfield. Conditions were much cooler across the eastern Ozarks as the front had not lifted through there yet as clouds kept temps in the mid 60s. The front will likely lift completely through the whole area by this evening and will generally reach the Interstate 70 corridor before stalling. Shortwave energy was currently moving through the Rockies and a deepening surface low was developing across southwest Kansas. A strong elevated mixed layer/cap was moving into the area and will keep precip chances virtually zero through this evening. By late evening however, a very strong 850mb jet (70knots) will develop from Oklahoma into southern Kansas. Thunderstorms will develop across northern Kansas and will likely consolidate into a cluster, becoming more linear with time. They will likely move through the Kansas City area around Midnight and then start taking a turn more to the east/southeast along the warm front and edge of the capping inversion. This complex will likely begin affecting areas north of Highway 54 sometime between 1-3am. MU capes in the 2000-2500j/kg range and 50kts of bulk shear will be more than sufficient to sustain this convection as it moves into the area. Given the expected linear nature, damaging wind gusts to 70 mph will be the main risk, however large hail to the size of quarters and a tornado will also be possible, especially with storms that can interact with the warm front, or with segments that align favorably with 0-3km wind shear vectors which look to be pointed east about 40kts. 12z HREF probabilistic data as well as SPC probs show the highest chances for severe storms tonight generally north of Interstate 44, especially closer to the Lake of the Ozarks region and locations near/north of Highway 54 after midnight. Lesser chances are expected along/south of I-44 in the 3am-7am timeframe, however there could still be a rather strong outflow boundary/effective front that moves through with gusty winds. Also, as the low level jet and surface low strengthens tonight, should see surface winds increase out of the south to around 30mph with gusts of 40-45mph possible, mainly from Springfield and points west. Therefore a Wind Advisory is in effect from 10pm-7am to account for this pre frontal wind threat. PW values in the 1.5-1.7in range will likely allow for some very heavy rainfall rates, however with a fairly progressive line, should see mainly a limited/localized risk for flash flooding, mainly with any cells that can train on the western periphery of the complex as the llj feeds into it. This matches WPC slight risk for excessive rainfall well. Overall rainfall amounts of 0.5-1.5 inches looks likely across the northern half or so of the area. Locations south of Highway 60 will not see as much with this system. Strong cold air advection looks likely for Sunday and with cloud cover remaining most of the day, high temps in the 60s will be reached early in the day, with readings dropping into the lower to middle 50s by afternoon. A rather raw and unseasonably cool Mothers Day is expected. .LONG TERM...(Sunday Night through Saturday) Issued at 235 PM CDT Sat May 8 2021 Surface high pressure builds down into the central US which will lead to several cool days that last through mid week. Highs in the 60s and lows in the 40s are a good bet. Can not rule out some upper 30s for lows a few nights. While models do show some light precip chances, a dry airmass and northeasterly winds with the high pressure may preclude much rainfall through early week. Temperatures look to moderate by late week with NBM generally showing highs increasing into the 70s. Low confidence in rain chances by the weekend with substantial model differences in the overall pattern. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 620 PM CDT Sat May 8 2021 Thunderstorms over Kansas and Nebraska are expected to form into a large complex that will move east into NW Missouri then shift south across the forecast area tonight. Exact details are still somewhat uncertain, but confidence is good given model consistency. Leaned heavily on the HRRR model for timing and coverage, which favors KSGF for the highest probabilities of thunderstorms and most intense convection. KJLN and KBBG look more on the periphery of the thunderstorm area. A damaging wind and large hail threat will exist. Strong winds aloft with gusts at the surface will also be a continued and increasing concern tonight. As the low level jet strengthens tonight, winds in the 2-4 thousand foot elevation range should be 60 to 70 knots. This will lead to increased surface gusts and low level wind shear. Convection clears out Sunday morning. && .SGF WATCHES/WARNINGS/ADVISORIES... MO...Wind Advisory from 10 PM this evening to 7 AM CDT Sunday for MOZ066-077-078-088>090-093>095-101>104. KS...Wind Advisory from 10 PM this evening to 7 AM CDT Sunday for KSZ073-097-101. && $$ SHORT TERM...Burchfield LONG TERM...Burchfield AVIATION...Titus
...Update to aviation forecast discussion...

.DISCUSSION... Issued at 259 PM CDT Sat May 8 2021 1930Z water vapor imagery showed a closed low over western MT with a shortwave rotating through the base of the trough over the central Rockies. A low pressure system as been steadily deepening across southwest KS and southeast CO. The warm front extending northeast of the surface low had lifted into south central NEB and far northeast KS. Severe thunderstorms remain probable tonight as guidance from the CAMs as well as the synoptic scale solutions develop a complex of storms and move them east along the warm frontal boundary tonight. If there has been a trend in the CAMs, the HRRR has been a little west with the initiation of storms and slower to bring them into the western parts of the forecast area. Otherwise they`ve been pretty consistent. Aircraft soundings near MCI show a substantial capping inversion near the warm front at 18Z and one near ICT at 1822Z also shows a cap over the warm sector. With the shortwave still to the west, will need to wait for storms to form near the triple point and move east. Forecast soundings from the NAM and RAP continue to forecast a mid level weakness in the wind field causing the hodograph to have an inflection. This would suggest storms would tend to split with cell mergers causing disruption with the updrafts and this seems to be what the CAMs depict this evening. However the low level jet is progged to strengthen as the shortwave moves into the plains and 12Z NAM forecast soundings show a brief window just ahead of the cold front where the hodograph elongates and loses the inflection. So there could be a risk for tornadoes into the evening, especially if a supercell storm could set up on the south of the convective cluster with uncontaminated access to the warm sector. There continues to also be a large hail risk and damaging winds. Some of the forecast soundings analogs show the potential for hail over 2 inches in diameter and with storms expected to congeal into a line, damaging winds may be the more widespread hazard to deal with tonight. As for flash flooding, there is a bit more uncertainty in excessive rainfall for a couple reasons. First storms look to be fairly progressive. If there was going to be a training concern, it would be along the warm front, but eventually the cold front should catch up and push the convection east and south. Second, models have trended further north with the axis of heaviest rainfall, and this makes some sense as the warm front has lifted into southern NEB. North central and northeast Kansas missed out on the isolated rainfall this morning and flash flood guidance of 2+ inches an hour support the idea that the ground could take a quick one or two inch downpour. Ultimately I think any flash flooding risk is going to be to isolated for a watch and driven by repeated convection over the same spot which isn`t a forgone conclusion. Something else to be concerned with tonight are the gradient winds behind the surface low. Models show the pressure gradient increasing as the low passes south of the forecast area. There is the potential for winds to remain up overnight and into Sunday morning, but it looks like the stronger pressure gradient forcing and wind gusts are coincident with the convection expected to occur. Even the HRRR keeps wind gusts below advisory levels. Think that if the gradient winds could reach advisory levels, it would be brief and right after storms pass, with the gradient beginning to relax shortly after storms move out. Because of this have opted not to issue a wind advisory and will monitor trends. Rain is expected to push east of the forecast area fairly early in the day Sunday with surface ridging building in. Cloud cover for a good portion of the day along with low level cold air advection is expected to keep temps in the 50s on Sunday and breezy north winds will make it feel cooler than that. The surface ridge remain over the central plains through Wednesday keeping temps below normal. There remains some potential for rain Monday through Wednesday as models show some energy kicking out from the west and riding over the central plains. There has been some variability in model runs with respect to the energy lifting out across the area and as a result POPs have bounced around a little bit. At this time it appears the better forcing for precip may impact the area Tuesday. But confidence in POPs is only so-so. Return flow redevelops Thursday with temps warming into next weekend. Differences between the GFS and ECMWF lead to more uncertainty in the forecast by Saturday, so did not stray from the national blend of models. This has chances for showers and thunderstorms Thursday night through Saturday. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 610 PM CDT Sat May 8 2021 Only minor changes to going forecast. Convective complexes slowly taking shape to the west and thunderstorm impacts are on track for the next several hours. Post-complex winds continue to veer into the end of this forecast though MVFR cigs will likely persist. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION...Wolters AVIATION...65