Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/01/24


Area Forecast Discussion
National Weather Service Des Moines IA
641 PM CDT Tue Apr 30 2024 ...Updated for the 00z Aviation Discussion... .KEY MESSAGES... - Enhanced Risk This Afternoon/Evening for Very Large Hail and Damaging Thunderstorm Winds - Heavy rain and marginal severe weather Wednesday night into Thursday. Localized hydrology impacts possible. - Active weather resumes this weekend and at the beginning of next week. && .DISCUSSION... Issued at 255 PM CDT Tue Apr 30 2024 Upper air analysis paints a broad area of troughing over southwest Canada with embedded shortwave energy propagating around the feature. One of note in the northern Plains will generate severe weather for Iowa today as it ejects across the region this afternoon. A secondary surface low placed over Nebraska will begin to phase into the main system, but will work together to intensify low level moisture advection. This process was already noticeable this morning as an advection wing of showers and storms progressed into the state, outrunning the instability axis. High dew point values will pool along an approaching cold front in the west, driving CAPE values into the 1000s range in southwest Iowa. Wind fields are favorable for storm organization with 50kt+ winds out of the West at H500 paired with diffluent flow aloft and enhanced southerly low level flow mentioned earlier. The wind field is near textbook for dominating right-moving supercells. Plenty of directional and speed shear aloft with an impressive looking low level wind field. The highest confidence threats would be hail and wind with storms, especially in the early stages of their lives when they are discreet. Large rotating updrafts with sufficient instability and ventilation are primed for large hail production. The 18z OAX sounding further supports hail production with 700-500mb lapse rates valued at 8.3 C/km. Inverted-v soundings below will allow for the acceleration of cold pools and, consequently, severe winds. Can expect possible hail in excess of 2 inches with larger storms and winds approaching 70mph in the favorable downdraft regime. Some uncertainty lingers on how these two threats will evolve as the sun sets and the LLJ influence increases. CAMs illustrate a gradual evolution of a linear mode of sorts with embedded UH streaks in the line. Thu UH streaks are large from the anticipated large updraft regions of storms with some updrafts noticeably deviating off Bunkers motion and into the better instability, further increasing the streamwise vorticity ingest. Whatever cell/cluster can get going along the instability axis will likely be the dominating storm and inhibit upscale growth of cells further to the north of it. CAMs have been consistent in placing this storm somewhere in central Iowa, but cannot say in certainty who would be directly impacted. Now, to cover the tornado threat. As it sits, there is a 5% risk of a tornado within 25 miles of of a point. If you observe soundings from the RAP for this afternoon, the tornado chances appear to be higher. The main difference is in the LCLs. Consensus for the area appears to be LCLs generally around 1500m which is too high for tornadoes. The RAP has some consistency in its run in really pooling moisture along the cold front this afternoon, lowering the LCLs to favorable heights for tornadoes. If the LCLs in the environment are lower, the storm will be able to ingest some of the streamwise vorticity found in the lowest km of the environment. Helicity values in this region of the atmosphere are in the 100s which is more than enough for tornadogenesis. That all being said, we are not expecting tornadoes to be the primary threat today, but that doesn`t mean they aren`t out of the question. The potential for tornadoes is higher the further into the moisture axis you traverse as this will be the region of the best potential for lower cloud bases. A close analysis of the near storm environment will be needed as the storms involve because further environmental factors such as boundary ingestion could further encourage tornadogenesis. A brief pause in precipitation is expected during the daytime Wednesday, but the Gulf opens up again through the day ahead of another approaching area of low pressure which will work to enhance jet speeds Wednesday evening and overnight, generating PWAT values nearing 1.5 inches in the southwest. Warm cloud depths will exceed 3500m. An MCS is anticipated to move into portions of southern Iowa ahead of even more rainfall anticipated with the main shortwave during the day Thursday. The MCS will settle for a path generally along wherever the instability axis sets up across the south. Consequently, the recovery of instability for Thursday will be questionable, causing uncertainty in severe weather chances. Nonetheless, the LLJ with advance further into the state through the day and continue to support additional rainfall statewide. Climatologically, PWAT and specific humidity values are in the upper 90th percentiles and near the top of the GEFS QPF model climatology. The ECMWF EFI covers much of the state in values between 0.7 and 0.8. The same area is circled in a shift of tails contour, signifying further that the QPF amounts are near the top of the model climatology. The grand ensemble 24 hour QPF exceeds 1 inch for especially the southern part of the state, given that this is a course output, locally high amounts are possible and will be better evaluated as the hi res window captures the event fully. Some river response is expected with HEFS putting some sites in action stage. The rest of the period remains mild and active with additional rain chances returning over the weekend. Temperatures will remain near 70 degrees. Active weather remains the theme into early next week. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 640 PM CDT Tue Apr 30 2024 A line of severe thunderstorms currently moving across central Iowa to impact the terminals now thru 02-03Z. MVFR/IFR cigs and vsbys to accompany these storms. Severe weather possible w/strongest storms to include hail and damaging winds. Skies quickly clear back to VFR behind with winds easing and becoming westerly through the overnight hours into the daylight hours on Wed. Chances for rain/lower CIGS to return Wed evening as the next weather system approaches from the SW. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Jimenez AVIATION...Percha
Area Forecast Discussion
National Weather Service Quad Cities IA IL
639 PM CDT Tue Apr 30 2024 .KEY MESSAGES... - The forecast will remain active through the period with almost daily chances of showers and thunderstorms. - Heavy rain is possible over the next 7 days with 1 to 3+ inches of rain in the forecast from WPC. - Temperatures are forecast to remain near to slightly above normal through the period. && .SHORT TERM /THROUGH WEDNESDAY/... Issued at 210 PM CDT Tue Apr 30 2024 A weakening area of showers and storms continues to lift east northeastward this afternoon across central Iowa north of a warm front that is forecast to continue lifting across the remainder of the area. Winds have shifted to the south behind this warm front with gusts up to 25 mph. At 2 PM, temperatures range from 69 degrees at Dubuque to 79 degrees at Washington with dewpoints largely in the lower to mid 50s. The dry air continues to impact the area of showers in central Iowa and think that this will continue to dissipate over the next couple of hours with light rain possible across Benton, Buchanan, Delaware, and Linn Counties. CAMs continue to show the development of a line of storms to our west this afternoon that moves east southeastward through this evening and has it moving across eastern Iowa, northwest Illinois and far northeast Missouri between 00 and 06 UTC. HREF 2 to 5 km updraft helicity swaths show the convection moving into our area west of a Fairfield to Cedar Rapids line before gradually weakening as it moves eastward. Continue to think that hail and damaging wind gusts are the main threat. SPC has our western two rows of counties in a slight or level 2 out of 5 risk of severe storms and the reminder of the area in a Marginal or level 1 out of 5 risk for severe storms. CAMs are in good overall agreement in the evolution of these storms and have been hinting at potentially stronger storms across area south of I-80. Several runs of the HRRR as well as the 12 UTC NAm Nest show the development of strong winds behind the convection across the area mainly along and north of Interstate 80. We will continue to monitor the situation to see if this does occur. The cold front will move across the area from west to east overnight with high pressure quickly building into the area at the surface and aloft. Skies will quickly clear from the west. High temperatures on Wednesday are forecast to be in the lower to mid 70s. Model soundings show some mixing behind the cold front with gusts west winds developing Wednesday morning with gusts up to 25 MPH through the day. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... Issued at 210 PM CDT Tue Apr 30 2024 A more active pattern will remain in place across the Upper Midwest Wednesday night through Monday night. There is a storm system roughly every 24 hours or so. A potent wave digging into the Rockies Wednesday night into Friday is forecast to deepen as it moves into the Plains. We will see a few leading impulses ahead of this wave pass through the area, leading to persistent showers/storms for the remainder of the week. The first of these will arrive Wednesday night. This will be a wet period, with the potential to see quite a bit of rain. With recent rains and more forecast, some rises along area rivers are possible. The parent wave developing is the one that has our attention though. There is plenty of uncertainty with this system, as well as major timing differences amongst guidance. Although, all long term guidance does show this system. If this wave deepens enough and we get that negative tilt upon arrival, this will bring the potential for strong to severe storms late in the week. Although, it is too soon to say for sure. WPC is highlighting our area in the risk for Excessive Rainfall from midweek through the end of the week, as they are currently forecasting between 1-3+ inches of rain by the week`s end for some. Thus, flash flooding will be possible, as well as rises along area rivers. So, just be mindful and stay up to date with the latest forecasts! && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 639 PM CDT Tue Apr 30 2024 VFR conditions are expected for most of the period. A line of showers and storms is expected to affect all TAF sites through 06z. Current tempo timing has been timed to match current radar trends. Tempos may need updating to include wind gusts especially at DBQ/CID/BRL as gusts over 50 kts are possible at these sites. Also DBQ could have prolonged winds after 05z, but confidence is low at this time. Frequent gusts to near 50kts could be possible at DBQ. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ UPDATE...Gibbs SHORT TERM...Cousins LONG TERM...Cousins/McClure AVIATION...Gibbs
Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
622 PM CDT Tue Apr 30 2024 ...Updated 00z Aviation... .KEY MESSAGES... - A Few Severe Storms Possible Tonight - More Rain Showers and Thunderstorms Wednesday/Thursday - Flooding Possible With Heavy Rainfall && .DISCUSSION... Issued at 326 PM CDT Tue Apr 30 2024 Compact H5 ridge axis has shifted eastward of the area and has pushed the surface anticyclone into the Ohio River Valley. A strong PV anomaly has resulted in a closed-low system over the Pacific Northwest that has been ejecting multiple vorticity maximums across the Central CONUS. The one of interest over the next 8-10 hours is an H5 short-wave trough axis that has acquired a negative tilt moving across the Northern Plains. Height falls extend southward with enhanced vorticity southward into the High Plains and Central Plains, and has promoted dCVA across the Front Range resulting in surface Lee Cyclogenesis. This has been promoting strong WAA across the area along with stronger theta-e advection into the lower Missouri River Valley. The warm front with this system has already pushed into Iowa this afternoon with cold front currently analyzed through west-central Kansas behind the main surface wave. There is also a dryline across western Kansas but the cold front should overtake this by the time it approaches our forecast area. With deepening surface cyclone, surface winds have been slowly backing over the past few hours across our area. H5 height falls have expanded eastward into eastern Nebraska and eastern Kansas late this afternoon and convergence has been steadily increasing in the area of pressure falls. A few showers have already developed in eastern Nebraska as of 19z. The boundary layer has been mixing quite a bit this afternoon, and the theta-e advection has helped MLCAPE values approach 1500 J/kg, with 12z HREF mean favoring this increasing to between 2000-2500 J/kg by the early evening. As the mid-level streak ejects ahead of the main trough axis with approaching vorticity maximum, deep layer shear will readily increase along the cold front and several kilometers ahead of it into the warm sector, with 0-6km bulk shear values generally around 40 kts. This bulk-shear vector is also oriented perpendicular to the cold front, which will support an initial discrete storm mode, as well as support a supercellular storm mode. Mid-level lapse rates have been steepening most of the afternoon which will support buoyant updraft development in the axis of convergence along the cold front and surface pressure falls with the approaching cyclone. RAP soundings suggest mid-level lapse rates near 8.0 C/km along several points with the approaching cold front. Thermodynamically these updrafts would suggest support for large hail, as there is also CAPE concentrated with the sub-freezing layer that could allow for hail embryo growth. The main question will be how fast storms move off the boundary, and if low-level storm relative flow is too strong, may eject hail stones out of the favorable growth. However with the magnitude of shear and shape of the hodograph the favorable pressure perturbations along the flanks of the updrafts may be enough to sustain large hail. With the larger degree of boundary layer mixing, some RAP soundings are showing increasing DCAPE values and drastically increasing theta-deficits from the surface to the top of the boundary layer that would suggest stronger cold pools and damaging wind potential. However, RAP/HRRR may be over producing the mixing, as stronger theta-e advection has maintained higher dewpoints and thus theta-e deficits are currently weaker than progged by deterministic CAM output. As for the tornado threat, we still need to remove some of the inhibition present from a weak inversion around 850mb. Thinking with the clear skies we have this afternoon we should be able to achieve this, giving us near- surface based parcels as convergence continues to increase. Low- level hodographs demonstrate notable curvature, with 0-500m SRH values near 100 m^2/s^/2, and 0-1km values between 150-200 m^2/s^/2 later this evening as the low-level jet ramps up. For both a storm motion with the mean wind and Bunker`s Right Mover estimation, storms will be able to realize large amounts of streamwise vorticity. Coupled with stronger storm-relative inflow providing strong updrafts, this could support a tornado threat. However, unsure how far east this will last. Storms will likely need to stay closer to the cold front to realize this kind of shear environment, and may quickly move off the boundary prior to entering our area. Therefore, will mainly be concerned with large hail and damaging wind if stronger supercells develop. Experimental WoFS models may be able to provide some guidance on how long supercells can last if they move off the boundary. As the low-level jet continues to strengthen through the evening, discrete storms along the front should congeal and eventually become an MCS or QLCS storm mode. This should eventually generate stronger cold pools capable of wind gusts, and perhaps a localized hail threat. As for rain, most deterministic CAM solutions are generally around 0.25 to 0.50 inches, with mean HREF values around 0.30 inches. The probability matched mean values from the 12z HREF do show a few high pockets of rainfall that exceeds one inch. From coarser resolution ensembles, mean QPF values in our far southwestern CWA is generally around 0.75 inches but a few members to produce more than one inch, and probability for exceeding one inch are around 30 to 40 percent. Therefore, have issued a Flood Watch for Flash Flooding potential in Bates County , MO and Linn County, KS this evening. Other areas could experience flash flooding with localized heavy rainfall, but will be difficult for it to become widespread. Rivers already experiencing high flow may rise with heavier rainfall this evening. Wednesday morning, subtle H5 height rises are progged through the morning which should help to end overnight activity along the front with just enough subsidence. Another short-wave coming out of the Intermountain West will provide another round dCVA and surface cyclogenesis across the Plains, maintaining southerly low-level flow. RAP/HRRR depict this stalling out the surface cold front roughly along the Hwy. 36 corridor, and starts another period of WAA by Wednesday morning across the area. Expecting isentropic upglide that could produce shower activity Wednesday morning into the afternoon. There will still be some instability under steep-midlevel lapse rates that perhaps could produce more convective structure, but there may not be enough large scale ascent support for this. Further, any subsidence with the H5 height rises my suppress this development. Have kept some POPs through Wednesday as current ensemble probabilities for measurable precipitation remain between 20- 30 percent, though probabilities rapidly drop off for a threshold QPF of 0.10 inches. By Wednesday evening, H5 height falls will pick up in pace, and the surface cyclone deepens as stronger dCVA occurs over the Central Plains and the system begins to move eastward. Convergence will increase across the lower Missouri River Valley and another cold front will begin to move across the area. There is some potential for convection to develop, but this will largely depend on boundary layer destabilization through the afternoon. If insentropic ascent keeps skies overcast, there may not be enough instability for convection structure. However, clear skies may allow for steepening boundary layer lapse rates, and improving kinematics with the approaching short-wave trough could produce stronger thunderstorms with some severe potential. Given how conditional Wednesday Night`s setup is on with tonight`s activity, will not dive to deeply into mesoscale details at this time. Right now, it appears the more favorable spot forcing and instability to line up will be west of the CWA. However, continued rainfall though may start to increase Flash Flood Risk, especially into Thursday morning. By Thursday Morning, ensemble probabilities for exceeding 0.50 inches of QPF is around 50 percent for a large portion of the forecast area, with around 20 percent for exceeding 1.0 inches. If a stronger convective storm mode is realized Wednesday Night into Thursday Morning, the higher end of the QPF spectrum could result in further flash flooding issues, as well as other hydrologic issues on area rivers and streams. Rain shower activity continues into Thursday as boundary slows down as well as propagation of H5 short-wave trough axis, with most of the activity exiting the area by late Thursday Night. The main vorticity max driving the Wednesday/Thursday activity should be cleared of the forecast area by early Friday morning. Progressive mid-level flow being rerouted around Canadian closed-low system continues through the weekend and into the next work week bringing additional chances for rain showers and thunderstorms. At this time, there is still a large amount of spread that makes it difficult to pinpoint details at this time, as well as comment on any severe weather potential. However hydrological concerns will remain with heavier rainfall events. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 620 PM CDT Tue Apr 30 2024 Cold front is moving closer with storms lined up along them. These will impact the TAF sites between 00z and 03z this evening, with a brief period of MVFR ceilings. Lingering precipitation possible on backside, conditions improve to VFR by the early morning Wednesday. Additional rain is possible Wednesday. && .EAX WATCHES/WARNINGS/ADVISORIES... MO...Flood Watch through Wednesday morning for MOZ053. KS...Flood Watch through Wednesday morning for KSZ060. && $$ DISCUSSION...Krull AVIATION...Krull
Area Forecast Discussion
National Weather Service Hastings NE
955 PM CDT Tue Apr 30 2024 .KEY MESSAGES... - There is a slight chance (around 20%) of thunderstorms this afternoon across far eastern and northeastern portions of the forecast area. These storms may become severe. - Shower and thunderstorm chances increase (up to near 70% during the afternoon) on Wednesday areawide with storm chances increasing up to 95% Wednesday night. - There is a 20% to 30% chance of strong to severe storms during the day Wednesday but much higher chances (up to around 70%) Wednesday evening and night. - After today, high temperatures will mostly be in the 60s and 70s and low temperatures in the 30s to 50s. && .UPDATE... Issued at 955 PM CDT Tue Apr 30 2024 Quick update regarding thunderstorm potential tomorrow... Latest model guidance is really honing in on the ongoing activity across KS/OK and how it will affect our sensible weather on Wed. In general, seems less and less likely that the surface warm front will return northward anywhere close to the local CWA, owing to persistent convection over central/SE Kansas into N OK through the overnight and even into Wed AM. Sfc winds will turn SE, but all this will do is advect a convectively overturned airmass from these areas into south central Nebraska and north central Kansas. This is not overly uncommon for this area at this time of year, as we`re still several weeks from peak sun angle and don`t have the help of surface ET. In fact, latest hi-res guidance suggests an expanding area of only 50s sfc temps by the aftn hrs thanks to more Erly/upslope sfc flow and thickening cloud cover. Prior to that, will probably see incr scat elevated convection from S to N by late AM or early aftn. Forecast soundings are generally unimpressive, at least from a thermo environment, as MUCAPE largely remains less than 1K J/kg. Could see some small hail (pea to penny-ish) from strongest cores, thanks to seasonably low WBZ heights and strong effective shear. Appears our "highest" risk for severe convection will come during the late evening and overnight from activity that initially develops over NE CO, then shifts E. Due to aforementioned stabilized effects from earlier in the day, any tstms tmrw eve/night will likely be elevated...around 800mb per 00Z HRRR forecast soundings. These soundings continue to be somewhat modest from an instability perspective (MUCAPE 1000-2000 J/kg, perhaps locally higher W/SW of the Tri-Cities), but 50kt of SWrly flow at H5 atop incr 35-45kt Srly LLJ should yield a substantial amount of effective shear. Even after excluding the stable lowest 1km, 1-6km hodographs are still quite long, and straight, with around 60kt of effective shear. This suggests some sort of combination of splitting supercells and/or linear segments. Axis of MUCAPE is highest W/SW of the Tri-Cities, so these areas may have highest risk in the 00Z-06Z time frame, with lessening risk with time and eastward extent. Large hail will likely be the primary risk. If linear storm mode indeed transpires, then dmg wind risk isn`t zero...but a relatively deep stable layer (around 1km) argues against much high wind making it to the sfc. This seems to be reflected in 00Z HRRR by lack of significant gusts near this convection. Any tornado threat looks to remain well S/SW of the area. && .DISCUSSION... Issued at 312 PM CDT Tue Apr 30 2024 Today and tonight... An upper trough is over the Pacific Northwest and Northern Plains and extends southward over the Central Plains. A cold front is pushing through south central and central Nebraska and north central Kansas from the northwest. Showers and thunderstorms are expected to develop along and ahead of this cold front this afternoon into this evening as it moves southeastward. Most models are showing the convection developing east of the forecast area, but there is about a 20% chance of storms developing across the far eastern and northeastern part of the forecast area later this afternoon. Any storm that develops will have the potential (60% to 70% chance) to become severe given fairly high CAPE, wind shear, and instability. Gusty northwest winds are present behind the front with temperatures in the 60s and 70s. A surface high will be present across the area tonight with fairly light winds. Low temperatures will range from the low 40s to low 50s. Wednesday and Wednesday night... Showers and thunderstorms may develop across mainly north central Kansas into far south central Nebraska Wednesday morning as the cold front lifts northward a bit and interacts with an upper level disturbance. Widespread severe storms are not expected with this activity but a few strong to severe storms will be possible (about a 20% to 30% chance). An upper trough to the west will move closer to the region Wednesday afternoon further increasing the upper level lift. There is uncertainty as to whether the activity during the morning and early afternoon hours will be strong to severe. Lift from the upper trough will increase across the area Wednesday night with the stalled front receiving a push southeastward. This will likely result in a complex of storms moving across the forecast area Wednesday evening into Wednesday night. The threats with these storms will be large hail, damaging winds, localized flash flooding, and a low tornado threat. High temperatures Wednesday will be in the mid 60s to low 70s. Low temperatures Wednesday night will be in the mid 40s to mid 50s. Thursday through Monday night... Lingering showers and storms are possible (up to a 50% chance) mainly east of Highway 281 Thursday morning. The rain and storms are expected to be out of the area Thursday afternoon. Winds will be gusty out of the northwest Thursday morning into Thursday afternoon as the colder air pushes through the area. High temperatures Thursday are expected to be in the mid 60s to low 70s. Winds will weaken during the evening hours with partly cloudy to mostly clear skies overnight. Low temperatures Thursday night are expected to drop into the mid 30s to mid 40s. Winds will increase out of the south to southeast on Friday as an upper trough covers the northern and central Plains. High temperatures on Friday are expected to be fairly similar to the previous day. An upper trough will move over the Central Plains Friday night and will provide increased chances (up to around 60%) of showers and thunderstorms. Low temperatures Friday night are expected to be in the mid 30s to upper 40s. The showers and storms will end by Saturday afternoon with high temperatures in the mid 60s to lower 70s. Low temperatures Saturday night will mostly be in the 40s. Winds across south central and central Nebraska and north central Kansas will increase out of the south to southeast with an upper trough dominating the western part of the country on Sunday. High temperatures on Sunday will mostly be in the 70s across the area. Gusty south to southeast winds will continue into Sunday night with lows in the 50s. The upper trough to the west will begin to move over the Central Plains on Monday with increasing rain and storm chances (up to near 50%). Low temperatures Monday night are expected to be in the mid 40s to mid 50s. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 658 PM CDT Tue Apr 30 2024 Tonight: W-NW winds will decr around sunset, then veer substantially through the overnight...becoming lgt and somewhat variable after midnight. Skies should be clear to mostly clear with just some FEW-SCT high clouds. Confidence: High. Tuesday: Expect incr mid level clouds by mid to late AM, then lower clouds, perhaps MVFR, towards the last 3-6 hrs of the valid period. The lowering CIGs could also be accompanied by some lgt shwrs. Winds will become ESE-SE for daytime hrs, and incr to 12-16kt, with gusts towards 20kt, esp for the aftn. Confidence: Medium. && .GID WATCHES/WARNINGS/ADVISORIES... NE...None. KS...None. && $$ UPDATE...Thies DISCUSSION...Schuldt AVIATION...Thies
Area Forecast Discussion
National Weather Service Goodland KS
515 PM MDT Tue Apr 30 2024 .KEY MESSAGES... - A marginal to enhanced risk for severe thunderstorms continues for the region Wednesday afternoon and evening. Isolated storms possible in the afternoon east of Highway 83 in northwest Kansas where large hail, damaging winds and perhaps an isolated tornado will be possible. Storms will become more widespread Wednesday night with large hail and locally heavy rainfall becoming the primary hazards. - Severe storms possible next Monday in eastern portions of the area. - Elevated to near critical fire weather possible Monday and Tuesday of next week. && .SHORT TERM /THROUGH FRIDAY NIGHT/... Issued at 200 PM MDT Tue Apr 30 2024 Cold front has moved out of the area this afternoon with gusty northwest winds in its wake. Those winds will gradually diminish through the late afternoon and early evening. Tonight, a weak wave embedded in the southwest flow aloft combined with low level upslope at the surface might result in a few isolated showers, mainly overnight, from northeast Colorado into southwest Nebraska. However, confidence is low and most models are dry. Low temperatures will be in the 40s. Clouds will increase Wednesday morning with moisture return from the southeast. By 18z expecting most if not the entire area to be socked in with low to mid level clouds with east to southeast winds. Weak impulse in the southwest flow aloft comes across in the afternoon with warm front likely south of the area. With persistent easterly winds north of the warm front, clouds may persist well into the afternoon. This will impact not only thunderstorm chances, but temperatures. Convective allowing models not in the best agreement on where storms will initiate. The HRRR has a couple of isolated supercells initiating after 21z near southeast corner of the area moving northeast, and additional develop towards 00z in northwest corner of the area near the secondary cold front. NAMnest on the other hand keeps the area in the cool, cloudy and capped all day with more of a stratiform light drizzle or light showers. The NAM does show plentiful elevated instability and shear, but never taps into it. The NAM keeps surface temperatures in the upper 40s to lower 50s all day in most of northwest Kansas and southwest Nebraska, a solution that cannot be completely discounted. Given all the uncertainties, confidence in severe risk and temperatures is low. Wednesday night, upper heights continue to fall/cool with approach of main upper trough. Surface cold front will continue to plow southeast and should be through the forecast area by 06z. There will be a risk of severe storms during the evening with the stronger forcing. NAM finally shows elevated convection developing late in the evening which taps into MUCAPE in excess of 1000 j/kg and up to 3000 j/kg in eastern areas with deep layer shear of around 50 kts. The HRRR shows a similar environment during that time with elevated storms and a favorable combination of MUCAPE/shear that would suggest a risk for large hail. HREF shows lows probabilities of 6-hour rainfall amounts of greater than 1 inch at 06z across mainly southwest Nebraska, which is consistent with the HRRR which shows 1-2 inch amounts along the Kansas/Nebraska border area and the NAM which shows a bullseye of around 1 inch in the same general area. Storms will be moving at a fairly decent clip of 10-20 kts, so appears to be more of a heavy rain threat than flash flood threat. Storms continue to move east overnight, with perhaps a lingering risk for severe hail between 06-09z east of Highway 25, before moving out after 09z. Low temperatures will be in the 40s. After morning clouds, Thursday will be mostly sunny with highs in the 60s. Widely scattered light showers will be possible Thursday evening in western areas with a weak wave coming across in the zonal flow aloft. However, with no instability to work with and little moisture, impacts will be minimal. Lows Thursday night will range from the upper 30s to lower 40s. Zonal flow continues on Friday with another open wave coming out of Colorado in the afternoon. Convection should initiate on the higher terrain to the west with forecast SBCAPE values of less than 500 j/kg. Showers and isolated storms continue east into Friday night, possibly merging into a large area of light to occasionally moderate rain. GFS and ECMWF show 12-hour precipitation amounts by 12z Saturday morning of between a quarter and a half inch. High temperatures will be in the lower 70s and low temperatures will range from the low to mid 30s in northeast Colorado to the lower 40s in north central Kansas. && .LONG TERM /SATURDAY THROUGH TUESDAY/... Issued at 200 PM MDT Tue Apr 30 2024 Saturday will be dry with shortwave ridging in the southwest flow. High temperatures will be in the upper 60s. Models are mixed regarding precipitation chances on Sunday. Next disturbance in the southwest flow passes well to the south in the GFS solution, but the ECMWF has a weaker, broader wave with a few showers/isolated storms further north. Confidence is rather low, but blended model did put in some 20 to 30 pops for the area during the afternoon and evening. Instability continues to be weak, so severe storms not expected. Temperatures warm into the 70s to lower 80s with lows Sunday night in the upper 40s to middle 50s. On Monday, the main trough ejects across the Rockies and a deep closed low will develop over the northern Rockies/adjacent plains by Monday afternoon. Most of the local area appears to get dry slotted on that track with a fire weather risk should stronger winds develop. Dry line trailing south across the High Plains may reside in eastern portions of the area Monday afternoon. Models show moderate instability along and east of the dry line with deep layer shear of 50-70 kts, parameters sufficient for a risk of severe storms including supercells. Uncertainty at that time range on location of the dry line is high and will likely fluctuate until the models can settle on a solution. High temperatures will be mainly in the 70s and lows in the 40s. Should be on the dry and breezy side of that system for Tuesday with highs in the 70s and lows in the 40s. May see another day of fire weather concerns with afternoon humidity minimums approaching 15-20% along with the breezier conditions. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 515 PM MDT Tue Apr 30 2024 KGLD...VFR conditions are expected through at least 14z. A northerly wind around 10kts at taf issuance will veer to the east overnight with speeds generally below 11kts. On Wednesday, east-southeast winds slowly increase through the day, gusting up to 25kts or so. Sub VFR cigs in stratus are possible in the 16z-20z timeframe and if the NAM model is correct, linger through the rest of the taf period. HRRR/GFS boundary layer relative humidity show the stratus (marking the location of a dry line) lifting to the northeast so at this time the late afternoon forecast of cigs is uncertain. Presently, am not expecting any precipitation through the period. KMCK...VFR conditions are expected through about 20z. A northwest wind gusting up to 25kts at taf issuance will subside below 10kts by 02z with winds veering to the east at speeds under 10kts overnight. On Wednesday, easterly winds gusting up to 25kts are expected. From 20z-24z, sub VFR cigs are expected in stratus. Will need to watch for a few showers in the vicinity of the terminal in the 08z-12z timeframe and again after 18z. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...None. CO...None. NE...None. && $$ SHORT TERM...024 LONG TERM...024 AVIATION...99
Area Forecast Discussion
National Weather Service Green Bay WI
1034 PM CDT Tue Apr 30 2024 Updated aviation portion for 06Z TAF issuance .KEY MESSAGES... - A low pressure system will bring a period of showers and thunderstorms from late this evening into the overnight hours tonight. No severe weather is expected, but a few storms could bring brief gusty winds and small hail. Another round of showers and storms are likely from Thursday into Friday. - Gusty west winds from 30 to 40 mph are expected over central and east-central Wisconsin on Wednesday. While recent rains will limit the fire weather potential, the gusty winds will bring a threat of isolated power line fires. - Due to recent and upcoming rainfall, rivers and streams will be on the rise late this week. Some rivers are forecast to reach bankfull stage by Friday or Saturday. && .DISCUSSION... Issued at 223 PM CDT Tue Apr 30 2024 Short Term...Tonight and Wednesday The latest RAP analysis and satellite/radar imagery show widespread low stratus across north-central to far northeast Wisconsin within a shallow, cool airmass. The back edge of this cloud cover has been slowly shifting to the northeast as return flow on the western flank of a ridge axis increases over the northern Mississippi Valley. Looking upstream, an elongated area of low pressure exists to the lee of the Rockies ahead of a potent shortwave trough. Showers and thunderstorms have developed on the leading edge of the moisture axis in a region of elevated moisture convergence from eastern South Dakota to Iowa. As low pressure tracks northeast across the region, precip and thunderstorm trends along with gusty winds on the backside of the system are the main forecasts concerns through Wednesday afternoon. Showers and thunderstorm potential: Low pressure will be intensifying as it moves from southern Minnesota early this evening to western Lake Superior by Wednesday morning. Strong QG forcing will be passing across the northwest half of Wisconsin as the low passes to go along with steep mid-level lapse rates upwards of 7 C/km. This forcing combined with a 40-50 kt low level jet will lead to a swath of showers and embedded thunderstorms lifting from southwest to northeast across the region from late evening through the overnight hours. The HREF indicates that elevated instability will weaken though the night, but can reach 500-750 j/kg as storms enter central WI late this evening. As a result, a few strong storms will be possible, primarily over central WI, but no severe weather is expected. The storms will become more isolated over north- central and far northeast WI late tonight as instability wanes. There is a 30-40% chance of 0.50" or more of rainfall over parts of central to north-central WI tonight. Gusty winds Wednesday: As the low lifts across Lake Superior, boundary layer winds will increase in a cold advection regime on Wednesday morning. HRRR/RAP/GFS all point to substantial low level moisture beneath the inversion and within a broad thermal troughing regime. As a result, some drizzle may stick around into Wednesday morning over far northern WI. The cloud cover and light precip will likely hinder wind gust potential across the region. Forecast soundings and NBM probabilities indicate the greatest potential for wind gusts above 35 mph will occur over east-central WI (40-60%) in the 1-2 pm hour, but those probabilities fall to under 20% for wind gusts greater than 40 mph. Therefore, while it will be windy, gusts do not appear strong enough for a wind advisory at this time. The gusty winds of 30-40 mph could lead to isolated power line fires, but recent rainfall and potential for underperforming winds due to cloud cover should limit the potential substantially. Think the potential is greatest over central WI to far northeast WI where green up has yet to occur in the sandy soil/forested areas. Long Term...Wednesday Night Through Tuesday An active pattern containing several systems and multiple rounds of precip is set to persist through the extended. Main focus will be on an end of week system that will bring rain chances to the western Great Lakes starting Thursday afternoon. As a result, the majority of the forecast area is under a slight risk for excessive rainfall Thursday through Friday. Expect river/stream levels to be on the rise through the end of the week, with some locations reaching bankfull by the end of the week. Thursday/Friday precip chances... Rain chances will begin to ramp up toward the latter half of the week as a robust trough spins up a lee cyclone that will eject into the upper Midwest by Friday morning. Warm air advection precip will likely arrive Thursday afternoon out ahead of a warm front before becoming more widespread Thursday evening along a trailing cold front as it moves east across the forecast area. Models are still struggling to hone in on QPF amounts, although ensemble guidance currently shows a strong signal for at least half an inch of storm total QPF through Friday. Given strong poleward moisture transport and an open Gulf, some models (GFS and ECMWF) would suggest closer to 0.75 to 1" of event QPF. Most convective elements look to remain to our south and east, although an elevated thunderstorm with some gusty winds cannot be ruled out Thursday evening through Friday morning with MUCAPE values in the 300 to 400 J/kg range (NAM). Best chances for thunder currently look to be in east- central Wisconsin, although any storms will have to overcome a robust surface inversion due to easterly flow advecting a stable lake airmass onshore. Drier conditions will then arrive behind the cold front on Friday as winds increase and veer to westerly. Gusts between 20 and 30 mph will be possible during this time, mainly in central Wisconsin. Saturday/Sunday precip chances... As Friday`s surface low continues to decay and exits to the north, another upper-level disturbance is progged to develop in its wake, bringing additional precip chances through the weekend. However, there is still model disagreement about the timing of this feature this far out in the forecast period, and thus how fast precip chances will arrive. Overall QPF amounts look to be lower than the previous system as most of the prime Gulf moisture struggles to make it up into the forecast area. Convective elements currently don`t look too impressive, although this may change as additional models come in range. && .AVIATION...for 06Z TAF Issuance Issued at 1033 PM CDT Tue Apr 30 2024 Showers and isolated thunderstorms will move across the region overnight as an upper level disturbance and surface front approach from the Plains states. Flight conditions will lower to MVFR/IFR in the precipitation. The rain will end by daybreak Wednesday. MVFR ceilings are likely west of an ESC to STE line, with VFR ceilings to the east. Southwest winds will gust to over 30 knots mostly south of a AUW to SUE line. Another weather system will bring additional showers and thunderstorms to the region Thursday and Thursday evening. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....MPC/Goodin AVIATION.......RDM
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
836 PM CDT Tue Apr 30 2024 .KEY MESSAGES... - Wind gusts 50 mph or higher possible around/just after midnight as a line of decaying showers/isolated thunderstorms moves across the area. - Gusty westerly winds to 30 mph Wednesday. - A couple periods of showers and thunderstorms mid to late week, most notably Wednesday night into early Thursday morning, then again late Thursday night into Friday morning. && .UPDATE... Issued at 836 PM CDT Tue Apr 30 2024 Recent radar trends across southern Iowa show that a cluster of generally discrete supercells proceeded by disorganized convection toward the Des Moines area has congealed into a more organized MCV near Ottumwa. Unlike as was depicted in earlier CAM guidance, this organization does not display a cohesive MCS signal. Expectations are for the current MCV to track just south of east into the relatively more favorable convective environment. This would bring the track along or just south of the far southern CWA. Concerns of a potential small wake low with 50mph+ winds remain valid, but the smaller footprint of organized convection and weaker cold pool/trailing meso-high suggest the overall threat is waning. Farther north, residual mid-level forcing may be able to maintain some lingering isolated showers and storms across most of northern Illinois through the overnight hours. Given the existing low-level dry airmass and only gradual nocturnal surface decoupling in the warm sector, any (decaying) shower/storm would still be capable of producing gusty winds at the surface. Kluber && .DISCUSSION... Issued at 308 PM CDT Tue Apr 30 2024 Through Wednesday Night: The primary forecast focus and concern is regarding what the HRRR and several other models are showing late this evening into the early overnight hours, which is the potential for wind gusts 50 mph or higher. As showers and a few thunderstorms move into the western area late this evening, they will be in a weakening phase and as they dissipate across the local area, the models are showing the potential for strong winds mixing to the surface. Of note with the HRRR is that it has been doing this consistently, run after run today. There is a narrow time window of strong winds via a low level jet and whether the models are mixing into this low level jet or trying to develop a wake low is not clear. Confidence is low for how this will evolve and trends with convection across IA will need to be monitored into this evening. Have bumped up winds tonight, with gusts into the 30-35 mph range but if what the HRRR and some of the models are showing does continue in later runs this evening, its possible a short duration wind headline may be needed. The models show these stronger winds diminishing in the predawn hours. Winds turn westerly Wednesday morning and now appear to be a bit stronger than previously expected, especially along and north of I-80 where wind gusts to 30 mph are possible. Winds slowly turn northwesterly Wednesday afternoon with speeds/gusts slowly diminishing in the mid/late afternoon. This may allow a lake breeze to develop into northwest IN by late afternoon but confidence is low for a lake breeze into northeast IL late Wednesday afternoon. The next system will bring a chance of showers and possibly a few thunderstorms to the area late Wednesday night into early Thursday morning. Confidence is fairly low for coverage and its possible that much of the area may remain dry, with the best chances across the northwest cwa. cms Thursday through Tuesday: Warm air advection driven showers (and some embedded thunderstorms) may be ongoing across portions of northern/northwestern IL at the start of the period Thursday morning as a surface warm front lifts northward into the area. However, the focus for this early morning warm air advection driven convection is expected to shift north of the area through midday as the surface warm front continues its northward shift towards the WI state line. Thereafter, a primarily precipitation free afternoon is anticipated, as we await our next good potential for showers and storms with an approaching cold front later Thursday night into Friday morning. While most areas may end up dry Thursday afternoon, temperatures could end up varying considerably across far northeastern IL (northern Chicago suburbs). This is due to fact that Lake Michigan may slow the northward progression of the warm front into WI near the lake, thus resulting in continued persistent cool east-southeasterly winds through the day. In such a scenario, temperatures Thursday afternoon would be held down in the lower 60s near the lake in far northeastern IL, while areas to the south of the warm front experience summer-like temperatures (in the low to mid-80s) and breezy south winds. Mild weather will continue into Thursday night as our area remains locked in the warm sector of the surface low tracking northward across the upper Midwest. This low is forecast to occlude over northern MN and far southwestern Ontario into early Friday morning. As it does so, the attendant surface cold front will slide eastward into our area very late Thursday night into Friday. A period of showers, and a few embedded thunderstorms, is likely to accompany this front, with the highest chances (60-80%) coming early Friday morning. We will need to continue to monitor the potential for any hydrologic concerns during this time frame, especially given the recent heavy rainfall the area has experienced. However, signs continue to point at the heaviest rainfall amounts potentially remaining west of the NWS Chicago forecast area in closer proximity to the track of the surface low. The rain threat is expected to end from west-to-east on Friday following the cold frontal passage. Thereafter, temperatures are favored to return closer to normal going into the weekend. Another approaching disturbance may result in another period of precipitation late Saturday into Saturday night, but the signal for this is not all that strong at this point. Otherwise, slightly warmer temperatures are favored into early next week with the overall weather pattern continuing to look rather active across the central CONUS. KJB && .AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 617 PM CDT Tue Apr 30 2024 Aviation Key Messages: - Decaying SHRA moving across the area late tonight - A period of strong (>40 kt) south-southwest wind gusts possibly accompanying the decaying SHRA, with at least 25-30 kt range gusts appearing probable - Potential for a period of MVFR CIGs early Wednesday, primarily at RFD - Diminishing winds turn northwest late Wednesday and eventually light northeast later Wednesday evening Surface winds will continue to back to the southeast early this evening, in response to low pressure currently moving east across the mid-Missouri River Valley. Area of strong/severe TSRA across IA-NW MO-KS are expected to weaken quickly as they move east this evening and outrun better instability to our west. Decaying showers will likely make it into northern IL, though may be only for a brief period especially farther east into the Chicago metro terminals. Of greater interest, has been multiple successive runs of the HRRR CAM, which had shown a consistent signal for very strong west- southwest winds of 40-50+ kts associated with the decaying showers. Latest (22Z) HRRR run has backed off these higher wind magnitudes, though along with other guidance continues to suggest a period of gusty winds near 30 kt overnight. Will continue to monitor trends with convection to our west and any associated enhanced winds. Forecast soundings indicate a period of MVFR ceilings are possible behind a cold front which will move through the area pre-dawn, with a better signal farther west/northwest for KRFD than our other terminals. These should erode after sunrise Wednesday, with breezy west winds expected. Winds are expected to diminish and veer northwest late in the day as surface high pressure spreads into the area, and then shift northeast later Wednesday evening. Ratzer && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory until 7 PM CDT Wednesday for the IL nearshore waters. Small Craft Advisory until 1 PM CDT Wednesday for the IN nearshore waters. && $$ Visit us at weather.gov/chicago
Area Forecast Discussion
National Weather Service Shreveport LA
851 PM CDT Tue Apr 30 2024 ...New UPDATE... .UPDATE... Issued at 843 PM CDT Tue Apr 30 2024 All is quiet attm across the Four State Region as our cu field has completely dissipated with just some high blowoff cirrus trying to invade our far west and northwest counties attm. Winds should go mostly light overnight and thus we could see some fog once again but it should not be to the extent that we saw early this morning prompting Dense Fog Advisories. Watching a complex of thunderstorms currently across SE KS, trying to enter northern and NE OK attm. Upper flow is mostly zonal to WSW aloft across the Southern Plains and upstream of our region but this activity is trying to drift slowly south and east. Latest HRRR tries to generate what looks like a cold pool with this convection late tonight with that convection continuing south and east with some of it entering far northern McCurtain County closer to 12z Wed. Did add just a little pops across our far northwest zones to account for this possibility as a southwest low level jet will likely continue feeding this complex through the night. Otherwise, temps are in the ballpark so no additional changes were necessary. Update out shortly...13. && .SHORT TERM... (This evening through Wednesday Night) Issued at 303 PM CDT Tue Apr 30 2024 The latest water vapor imagery indicates a rather broad area of mid and upper level dry air from the Southern Plains into the Southeast CONUS. With a surface ridge moving farther east tonight while a lee surface trough strengthens over the High Plains, low- level moisture will begin to gradually increase. This should result in more low clouds during the early morning hours of Wednesday. Patchy fog will also be possible but current thinking is increased surface wind speeds and increased low-level cloud cover may limit the potential for dense fog as compared to Tuesday morning. A weak disturbance in the zonal flow aloft will provide the potential for at least a isolated showers or thunderstorms on Wednesday. The first opportunity will be limited to portions of Southeast Oklahoma and extreme Northeast Texas Wednesday morning. However, rain chances will spread southward during the afternoon. There may be a brief lull in the rain chances early Wednesday evening, but the flow aloft will quickly become more southwesterly and will amplify resulting in a rapid increase in deep layer moisture. A broad area of showers and thunderstorms are expected to develop from Kansas southward into Texas ahead of a cold front and dryline. These storms should move into the area after midnight Wednesday night/Thursday morning. Strong large scale forcing and abundant deep layer moisture may result in locally heavy rainfall, especially across Deep East Texas. Severe weather chances appear low at this time. CN && .LONG TERM... (Thursday through next Monday) Issued at 303 PM CDT Tue Apr 30 2024 Widespread showers and thunderstorms should be ongoing Thursday morning, especially across Southeast Oklahoma, Southwest Arkansas, East Texas, and portions of Western Louisiana. Vertical ascent is expected to be quite strong during the day Thursday as a shortwave trough moves east-northeast across the forecast area. Combined with precipitable water values over 2 inches, locally heavy rainfall is likely, particularly south of Interstate 20 across East Texas and into Western Louisiana. Thursday`s convection is expected to be well ahead of the cold front, and more showers and thunderstorms are likely as the front moves into the area on Friday before stalling north of Interstate 20. The heaviest rainfall rates are generally expected on Thursday, but the threat of heavy rain should finally diminish Friday afternoon as the front begins lifting back northward into Oklahoma and Arkansas. The remainder of the long-term forecast will remain quite unsettled. Southwesterly flow aloft will persist and a series of weak perturbations in the flow will keep chances for scattered showers and thunderstorms in the forecast Friday and Saturday. Rain chances may increase across the northwest half of the area on Sunday as a stronger shortwave trough lifts northeast across Texas and Oklahoma. Deep southerly flow will provide plenty of warm air advection and moisture to fuel convection. Despite the persistent rain chances, during the weekend, the strong warm air advection will keep a warming trend in place. Daytime high temperatures should be well into the 80s and possibly into the lower 90s early next week. With the rainfall and wet soils, very humid conditions can be expected to accompany the heat. CN && .AVIATION... (00Z TAFS) Issued at 626 PM CDT Tue Apr 30 2024 VFR remains airspace wide this evening as clouds continue to clear on out. Clear skies, calmer winds and a close T/Td relation will once again promote the chance for reduced VSBY at area terminals. Flight conditions will recover through the morning across central and and eastern terminals as the BR/FG lifts and burns off, with some FEW/SCT prevailing through the late morning before a return to mostly SKC. Cross sections this evening look to promote some BKN low CIGs across the western terminals through the afternoon and evening. RK && .PRELIMINARY POINT TEMPS/POPS... SHV 63 87 70 78 / 0 10 20 90 MLU 62 87 66 80 / 0 0 10 60 DEQ 62 85 64 75 / 10 10 30 90 TXK 64 85 68 77 / 0 10 30 90 ELD 61 86 64 77 / 0 0 10 70 TYR 66 85 68 79 / 0 30 60 90 GGG 65 85 68 78 / 0 30 40 90 LFK 65 85 69 81 / 0 40 30 70 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...None. LA...None. OK...None. TX...None. && $$ SHORT TERM...09 LONG TERM....09 AVIATION...53