Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/09/23

Area Forecast Discussion
National Weather Service La Crosse WI
1059 PM CDT Mon May 8 2023 .DISCUSSION...(This evening through Monday) Issued at 150 PM CDT Mon May 8 2023 Key Messages: - Conditional Strong to Severe Storm Threat Today and Tuesday - Warmer Temperatures Through Midweek Across The Area - Active Pattern Continues Latter Half of the Week Into The Weekend Storm Threat Setup This Morning: Conditional storm threat has increased over previous forecasts later this afternoon and into the evening. Upper level ice nucleated clouds overhead earlier this morning were associated with the convection farther south into central IL and have continued east, evident in recent satellite upper level water vapor imagery loops. Derived GOES upper level winds suggest associated perturbation quickly advecting downstream to the Great Lakes. Upstream, the quasi-zonal jet streak core expected to bifurcate the forecast area this afternoon, placing a thermally indirect transverse ageostrophic circulation for parts of the forecast area this afternoon. This is evident in forecasted isentropic analysis pushing 5 ubar/s of upglide at 295 K. Conditional Storm Threat Later This Afternoon & Evening: Weak surface boundary earlier this morning from east-central Minnesota into western Iowa exhibits meager dewpoint differential of 10 degrees per 100 miles. A thick, low level stratus deck early this morning ahead of this moisture gradient has muddled surface temperature differential across the surface front. Forecast cross section analysts show the ageostrophic influence and frontogenetical response expected later this afternoon with 5-10 ubar/s of omega. RAP/HRRR (08.15/12Z) build MLCAPE pool through central Iowa into central Minnesota later this afternoon, pushing 500 J/kg later this afternoon. Associated model soundings show MUCAPE reaching 1000 J/kg, weak low level shear profiles, and straight line hodographs. Tying it all together, early this afternoon the initial inhibitive stratus deck has been clearing, increasing mixing. While, as previously mentioned, low level shear is nearly naught, mid to upper level speed shear should sustain storms and severity, 60 kts from 3-8km, showing straight line hodographs, and RAP soundings suggesting 10km storm tops. In summary, severe hail will be a conditional concern late this afternoon into the early evening from southeast Minnesota into northeast Iowa. Given the nearly non-existent low level shear, surface based storms will be limited, however still possible. Main driving mechanism would be ingestion of the nebulous surface boundary into a splitting discrete supercell storm, resulting in isolated, limited tornado threat. Very low confidence (<20%) and spatial extent. Tonight: This afternoon storm threat and exit behavior of clouds will determine surface cooling overnight and increasing fog potential. Surface dewpoints expected to remain near 50 degrees, suggesting enough moisture should skies clear and surface cooling increases. Conditional Storm Threat Tuesday: While mid and upper level heights build early Tuesday morning, slight ridge running perturbations continue precipitation and storm chances primarily along our western periphery. Lobes of passing mid level positive vorticity advection concurrent with lobes of increased low level theta e are expected to primarily impact our western counties in northeast Iowa and southeast Minnesota into the late afternoon-evening. A quasi-stationary boundary appears to be the initial forcing mechanism exhibiting meager surface convergence. Initial storm motion may lie along and quasi- parallel this quasi stationary surface boundary. Current high resolution forecast models drape this surface boundary from central Minnesota to western Wisconsin; west to just northwest of the local forecast area. Similar to today, best shear expected to be elevated, however more directional shear in the midlevels resulting in clockwise turning hodographs increasing helicity above 250 m2/s2 for an extremely short window into the early evening. While low level shear is limited, again, ingesting of any surface vorticity along the boundary, depending on where it sets up, could result in the potential for an isolated tornado threat. RAP/HRRR build 1000/1500 J/kg ML/MUCAPE through the late afternoon along our western periphery with long and skinny CAPE profiles, limiting initial development and vertical velocity as well as perhaps other severe threat types. Overall, extremely conditional threat given the current forecast hour limiting the number of high resolution models. Also, many different storm dependencies, including cloud and fog deck(s) tonight, exact placement of surface boundary during the day, and timing of best instability concurrent with peak diurnal influence. Given these dependencies and model differences, lot to work out yet and need a lot of ingredients to come together; will be something to keep an eye on. Midweek Into the Weekend: Through midweek, heights again try to build with potential ridge running perturbations and positive lobes of mid level vorticity advection. Low level moisture transport and resultant increased theta e peak off to our west through Wednesday afternoon, with forecast concern becoming maximum daytime high temperatures. Most confidence (>70%) for maximum daytime temperatures in the 70s for much of the area. Progressive pattern continues through the latter half of the week with increased low level theta e passing over the forecast area Thursday. Increased low level moisture transport backs to our west, keeping more moist air there. Storm and severe chances continue Thursday night into the weekend with disagreement on eastward extent of Central Plains upper level positively tilted trough becoming closed as it attempts to advect northeast. Again, something to keep an eye on for Friday into the weekend. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1054 PM CDT Mon May 8 2023 Upcoming TAFS at 06Z will be challenging with various weather situations across the airfields. Clearing at KRST will provide conditions preferable for fog formation by morning, possible LIFR. Recent rains have only added to the confidence and increased the probability. At KLSE, a band of showers will move through around 05Z and set the stage similar to KRST for fog. However, IFR clouds are about 2 counties east of the airfield and with inversion conditions overnight, that deck will expand west into KLSE. IFR is expected but confidence is slightly lower on visibility. Conditions will improve through the morning on Tuesday. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ DISCUSSION...JAR AVIATION...Baumgardt
Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
956 PM CDT Mon May 8 2023 ...New UPDATE... .UPDATE... Issued at 948 PM CDT Mon May 8 2023 Convection over northeast Mexico has struggled to maintain organization as activity approached the Rio Grande. Even though there is plenty of instability and shear is adequate, it appears the convective inhibition is winning out. Adjusted PoPs down slightly for the coastal plains. Latest HRRR shows redevelopment overnight around a forming mid level low. && .SHORT TERM... (Tonight through Tuesday night) Issued at 345 PM CDT Mon May 8 2023 A mid-level trough over the Rio Grande will push a cluster of showers and thunderstorms from Mexico into the Rio Grande Plains and Brush Country tonight. This trough is progged to develop a closed low over Central Texas tonight into Tuesday. Latest CAM guidance shows a bow-like feature move west to east through the CWA from around 7PM through 3AM. Have 40-50% PoPs tonight following this event. Afterwards, the forecast is tricky with global models and NBM indicating higher QPF and rain chances compared to latest CAM showing only a few showers and storms on Tuesday. A surface meso-low is shown to the develop in the CAMs from the storms moving into the coastal waters, progressing parallel northward along the Texas Coast, putting South Texas in the unfavorable drier air entrainment part of the low. Still believe scattered showers and thunderstorms could develop Tuesday and Tuesday night with at least 75th percentile PWATs and bands of positive vorticity aloft associated with the mid-level trough. Mostly cloudy to overcast skies with rainfall will "cool" temperatures down to highs from the low 80s to low 90s east to west respectively. Lows will stay in the mid 70s. && .LONG TERM... (Wednesday through next Sunday) Issued at 345 PM CDT Mon May 8 2023 Key Messages: - Potential for heavy rain, especially Friday through Sunday. Very messy forecast from the middle of this week through the weekend. The overall pattern remains wet with multiple mid-level disturbances interacting with well above normal moisture levels. We`ll break it down here as best we can, but the smaller scale features and timing/placement of the period of heavy rain are still unclear. In the long term period the first feature we`re looking at is a mid- level low that should be exiting the region at the beginning of the period. Depending on the speed of this feature and it`s surface reflection, currently expect a pretty wet Wednesday morning into the afternoon before a drier period Wednesday evening/night. Central to eastern portions of the area will have the best rain chances Wednesday and could see a couple of inches. We are in a slight risk of excessive rainfall for that period. By Thursday morning a weak shortwave will be approaching to bring another shot at showers and thunderstorms during the day. This period looks less organized, but PWAT values remain elevated, so any showers and storms that do develop could bring locally heavy rains. The most concerning period comes Friday afternoon through the weekend as a deeper mid-level trough and closed low develop and approach the area. There are still substantial differences in model guidance which leads to the low confidence in the finer details of this event, but there is pretty high confidence in at least portions of the area getting a few inches of rain through the weekend. Probabilities of 3" or more made out around 50-60% in the NBM in central and eastern parts of the area, but looking at ensembles, ECMWF is indicating 70% chance of 2" for Saturday alone. GEFS ensemble is significantly lower than this. Thus the lower confidence. That said...with current QPF expectations, we will likely have concerns of flash flooding and river flooding for this weeekend. We`ll just have to see how things evolve over the next few days and hope that guidance can settle in on something to improve confidence moving forward. Outside of the thunderstorms/rainfall concerns, there`s not too much else to discuss for the long term period. Temperatures will be seasonal through the end of the week, but likely a bit below normal for the weekend if the widespread rain pans out. && .AVIATION... (00Z TAFS) Issued at 654 PM CDT Mon May 8 2023 Strong convection continues to organize over the higher terrain of northeast Mexico to the west-southwest of Laredo as the mid level short wave trough moves in from the west. Strongly unstable air mass resides along the Rio Grande into the Brush Country with MLCAPE values up to 4000 J/kg. The 0-6 km shear vectors are from the west around 35 knots. Expect activity will continue to advance toward the Rio Grande and affect the Brush Country this evening. Latest HRRR forecast (21Z) does not add confidence in this scenario, showing the complex moving east-southeast toward the Rio Grande valley. But will base forecast on the HREF with the ensembles showing storms moving into the western areas. Will be cautious with bringing activity all the way toward the coast as mid level inversion could inhibit the storms. Will bring the convection to ALI later this evening but only show VCSH for CRP at this time. MVFR ceilings along the coast will move inland this evening with IFR ceilings and MVFR vsbys possible for the coastal plains during the overnight period. A mid level low is expected to form over the Mid-Coast region Tuesday morning. This system will interact with deep moisture in place to produce scattered convection from the Coastal Bend to the Victoria Crossroads from late morning through most of the afternoon. Will show MVFR ceilings prevalent over the coastal plains through the afternoon while VFR ceilings occur over the Brush Country. && .MARINE... Issued at 345 PM CDT Mon May 8 2023 Generally moderate flow is expected across the local waters through this weekend. Daily showers and thunderstorms are expected each day this week with Friday through Sunday being the most active. Any thunderstorms that develops will have the potential to produce gusty winds and frequent lightning. && .PRELIMINARY POINT TEMPS/POPS... Corpus Christi 74 85 74 82 / 40 50 40 40 Victoria 73 83 71 82 / 30 60 40 50 Laredo 73 92 74 90 / 60 30 30 30 Alice 71 87 71 86 / 50 50 30 40 Rockport 74 81 75 84 / 40 50 40 40 Cotulla 73 92 74 91 / 40 30 30 40 Kingsville 74 87 73 84 / 50 50 30 40 Navy Corpus 76 82 76 84 / 40 50 40 40 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ SHORT TERM...TMT/89 LONG TERM....PH AVIATION...TMT
Area Forecast Discussion
National Weather Service Cheyenne WY
525 PM MDT Mon May 8 2023 .SHORT TERM...(This evening through Tuesday) Issued at 400 PM MDT Mon May 8 2023 Active weather pattern will begin over the next 24 to 36 hours with several potential hazards to discuss. Overall, confidence is increasing with the vigorous Pacific storm system forecast to begin pushing into the Rocky Mountain Region on Wednesday. Deterministic models are in much better agreement with this system compared to 2 days ago with solutions favoring a southward track. This storm system is expected to bring widespread low elevation rainfall...heavy at times, severe thunderstorms, some fog, and the potential for significant mountain snow after Wednesday. For today, showers and thunderstorms developed a few hours earlier than expected with a quick 0.05 to 0.10 inch of rain near the I-80 Corridor. Further north, clouds are struggling to develop in an area of broad midlevel subsidence. Expect this to change this evening as the next shortwave disturbance/vorticity maximum enters the region from the west. Expect another round of widely scattered thunderstorms to develop and push east across the high plains late this evening and possibly continuing overnight. Kept the highest POP (30 to 50 percent) after 9 PM as this shortwave trough enters the region. Another jet streak is forecast to push east creating a weak jet couplet and enhanced diffluence aloft. Some of these thunderstorms may contain some gusty winds with high res guidance showing some cold pool activity just behind the bands of showers and thunderstorms. This makes sense given current observed surface dewpoints and inverted V soundings across the northern portion of the area towards Converse County eastward into the northern Nebraska Panhandle. In addition, the Low Level Jet is still forecast to strengthen with gusty south to southeast winds east of the I-25 corridor. This may enhance convection even further with decent low level moisture advection even further south towards the southern panhandle. With convection around the area, not expecting fog to form, but low clouds and overcast skies may be pretty widespread by sunrise Tuesday. For Tuesday, SPC Marginal Risk for strong to severe storms remains over portions of the forecast area, mainly areas along and east of I-25. Still a tricky thunderstorm forecast for afternoon and evening hours since models are still showing the upper level flow backing into the south ahead of the Pacific storm system. A shortwave ridge axis is expected to build ahead of this storm into Kansas, Nebraska, and eastern Wyoming during the day, but models struggling to resolved the position and movement of the next disturbance/weak vort max aloft. HRRR and current NAM are not showing too much activity Tuesday afternoon and evening with only a few thunderstorms developing just east of the Laramie Range and quickly pushing east into the western Nebraska Panhandle. Still expect some thunderstorm activity to develop as winds across the high plains shift into the southeast...resulting in the typical convergence boundary along/near the Laramie Range. However, the timing is highly uncertain. Models are showing higher confidence with a developing storm complex in northeast Colorado and western Nebraska overnight which looks like an MCS moving east south east. Increased POP between 40 to 70 percent east of I-25 late Tuesday night. Tuesday should be the warmest day of the week with highs in the upper 60s to mid 70s, but Wednesday might be a little warmer if the system slows down during the day. Wednesday morning should be deceptively quiet across the area just ahead of the strong Pacific storm, which will be tracking into the Four Corners Region during the day. With a surface low developing and track eastward into Utah and western Colorado, surface winds will likely shift into the east and southeast Tuesday night through Wednesday morning. Expect low clouds and fog to develop as surface moisture advection increasing towards the 80th to 90th percentile, and even higher during the day on Wednesday based on the NAEFS. Added fog mainly to the Pine Ridge and Cheyenne Ridge including the I-80 Summit for now, but may need to extend this across the eastern plains. This will set the stage for a potentially active Wednesday afternoon and evening with ample low level moisture between the 90th to 99th percentile versus climatological averages. Model soundings and convective parameters are favorable for severe weather, and models have trended further west with the favorable shear and 0-3km instability. 12z NAM and NAMnest continue to show EHI`s between 2 to 4, with earlier runs as high as 5 across Albany county and stretching east across most of the eastern plains. 18z run is not quite as aggressive, but still pretty impressive. Soundings continue to show impressive low level wind shear as cyclogenesis gets going somewhere between Albany County, Platte County, and further south along northeast Colorado. With MLCAPE values between 1500 to 2500 j/kg with an impressive cap inversion just below 700mb, which erodes as the potent dynamic forcing ahead of the main storm system tracks north into the region. Started wording the forecast for severe thunderstorms Wednesday afternoon and evening as SPC shows a Day 3 slight risk for severe weather. Expect this area to increase in coverage and can not rule out an Enhanced Risk sometime in the future. Damaging winds, large hail, brief very heavy rainfall, and even a few isolated tornadoes are possible with this set up. However, will have to watch how long the low stratus and fog linger over the area, which may result in considerable CIN through the day. Also, the Pacific storm may be so dynamic, that most of the convection becomes organized (squall lines) too early in the evolution...which will result in more of a straight line wind threat and very heavy rainfall. Residents and travelers are urged to closely monitor this potential severe weather event on Wednesday. But wait, there`s more...snowlevels ahead of this storm will likely be close to 12000 to 13000 feet at the onset Wednesday afternoon. With mositure and warm air advecting into Albany county and the adjacent mountains, will have to closely monitor river and stream levels particularly in the Snowy Range and the surrounding areas for heavy rain on a solid snowpack up around 8000 to 10000 feet. Thought about an Areal Flood Watch, but will let the next shift(s) take another look at it before we commit. .LONG TERM...(Tuesday night through Monday) Issued at 400 PM MDT Mon May 8 2023 Active weather is likely to continue through the end of the week and into the weekend under the influence of a soggy, slow-moving low pressure system meanders its way through the area. The main impacts concern continuing severe thunderstorms, flooding potential due to rain-on-snow in some areas, and heavy mountain snowfall. Starting off Wednesday evening, we will have a strong upper level low located near or just south of the Four Corners encroaching on a strong ridge located over the Plains and Midwest. The severe thunderstorm threat described in the short term period will carry over into Wednesday evening, with profiles remaining conducive. Please see above for details on this threat since the following discussion will mainly focus on the transition to the cool sector of the system and heavy rainfall threat continuing after the severe threat. Veering shear profiles and steep lapse rates continue through much of the overnight hours so scattered severe thunderstorms may continue. By Thursday morning, models show the upper level low moving out into eastern Colorado and becoming negatively tilted against the amplifying downstream ridge. This will lead to winds aloft turning more southeasterly. More vertically stacked wind profiles and less steep lapse rates Thursday will likely change the precipitation characteristics. We will still have isentropic lift and deep orographic flow with easterly winds up to nearly the tropopause. The atmosphere will remain extremely moist. Ensemble mean PW values exceed the 90th percentile of climatology, and the ECMWF ensemble mean PW exceeds the 99th percentile. Widespread showers with scattered embedded thunderstorms are likely through the day on Thursday. The severe potential is a little uncertain with instability more limited than Wednesday and weaker shear owing to the vertically stacked profile. However, a slightly more northward track in the upper level low could easily push more potent profiles into the area, particularly the southern Nebraska panhandle. We will need to watch for this potential, and breaks in cloud cover that could enhance instability. Overall though, the main impact after Thursday morning looks to be more on the rainfall/flooding side of things. There is some concern with heavy rainfall and rain-on-snow especially during the early part of the event Wednesday night through Thursday. Rain could be falling as high as 10kft Wednesday evening with very warm 700-mb temperatures in the +5 to +7C range. Cooler air will work in Wednesday night, pushing 700-mb temperatures to around 0C to +2C over the higher terrain by 12z Thursday. This should bring snow down to around 8500 to 9kft. Substantial snowpack still remains in the 7500 to 9000 ft range that could continue to see rain through the daytime hours on Thursday. We will need to monitor small streams and possibly some rivers for rises due to the combination of heavy rainfall and rain-on-snow through Thursday. Heading into Thursday night, snow levels drop further, such that snowflakes mixing in for the city of Laramie can`t be ruled out early Friday morning. Looking at total QPF estimations, the GFS and GEFS have trended slightly towards the ECMWF over the last 24 hours, while the latter has held fairly steady. The ECMWF solution is a slower, more southerly track of the upper level low that ejects off to the east later, resulting in a longer period of deep upslope flow and favorable dynamics and heavy precipitation. All ECMWF ensemble members now have a surface low developing over Colorado and ejecting eastward from there. There is still roughly one third of the GEFS members that show the surface low quickly moving northward into Nebraska or South Dakota during the day on Thursday, but there are fewer than at this time yesterday. Ensemble QPF remains substantial. The ECMWF ensemble mean continues to show around 1.75" or more liquid precipitation falling by Saturday for almost the entire area from the Snowy Range eastward. The ECMWF ensemble minimum is a fairly eye catching 1.0" liquid at KCYS. The GEFS remains more modest, but has come up a little since yesterday. This ensemble mean still shows 1 to 1.75" for the majority of the area, with higher amounts in Converse county. For the official forecast, kept QPF generally in between the two ensemble means, but will note that with convective nature, some areas are likely to see much more, while others may see much less. Finally, the precipitation will be falling as largely snow in the highest elevations, and could be enough to lead to Warning level accumulations particularly in the Snowy range. Models continue to diverge Friday onward, but there is enough confidence in unsettled and generally cool weather to continue. The GFS pushes the upper level low further north, while the ECMWF holds it further south. The main difference would be additional rainfall in the slower scenario Friday into Saturday, whereas the GFS scenario is still cool and somewhat cloudy but a little drier. Models are showing a highly unusual synoptic weather pattern for the weekend. There is fairly good agreement now on an extremely strong ridge developing over the Pacific northwest and southwest Canada. 200-mb and 500-mb heights to our north will be well above the climatological maximum. Over our area and further southwestward, models show a messy signal with weak vort maxes retrograding and meandering around the southwest under very weak flow aloft. Most of this unsettled weather may stick to our southwest, but could see daily shower and thunderstorm chances continuing Sunday and Monday beyond the end of the main system. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 516 PM MDT Mon May 8 2023 A weak disturbance will be moving through the area through 12Z Tuesday. VCSH and VCTS will be present for most of the terminals between 0Z and 12Z. WY terminals could see localized fluctuations to MVFR if -SHRA occurs during the VCTS events overnight. VRB winds are anticipated for the NE Panhandle terminals, with weak upslope flow taking over between 9Z-13Z. This will create MVFR/IFR CIGs, with MIFG being present at times. Wind gusts should pick up to 15-25 knots by mid-day Tuesday for terminals. && .FIRE WEATHER... Issued at 400 PM MDT Mon May 8 2023 No fire weather concerns this week due to an unsettled and wet weather pattern. Today will be the driest day with relative humidities down to around 20 percent with a few places near 15 to 18 percent. This will be short-lived with increasing moisture tonight ahead of a strong Pacific storm forecast to impact the area with widespread rain, mountain snow, and scattered to numerous thunderstorms through the end of the week. Forecast rainfall amounts are trending higher compared to a few days ago with most places between a half an inch to one inch of liquid by Friday. && .HYDROLOGY... Issued at 400 PM MDT Mon May 8 2023 River levels will continue to trend lower through Tuesday across Carbon and Albany counties before a strong Pacific storm system moves into the central Rockys. Models are starting to come into better agreement with the track of this system and potential impacts, not only from a river flooding perspective...but also areal and general flooding due to heavy rainfall and rain on snowpack in the mountains. Will have to closely monitor the high mountain snowpack and the potential for heavy rainfall Wednesday. Another slow increase in river levels are expected starting late on Tuesday...mainly the Little Snake, Laramie, and Medicine Bow rivers and associated smaller tributaries. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...TJT LONG TERM...MN AVIATION...BW FIRE WEATHER...TJT HYDROLOGY...TJT
Area Forecast Discussion
National Weather Service Dodge City KS
1100 PM CDT Mon May 8 2023 ...updated aviation... .SHORT TERM...(This evening through Tuesday night) Issued at 1245 PM CDT Mon May 8 2023 17Z observations show an upper level pattern with winds out of the west southwest in response to an upper low over the Pacific coast. At the surface a cold front from last night`s MCS is into northern Oklahoma with a surface high located in northern Kansas which has led to sunshine across much of western Kansas. Overall for the evening hours it should be quiet across Dodge City`s CWA. Short term models (HRRR/RAP/NAM) show a developing MCS over northeast Colorado and southwest Nebraska in response to an upper level shortwave riding over a baroclinic zone in the early morning hours. Some of the CAMs have a variance in whether or not the MCS makes it into the I-70 corridor however it should be close enough I kept POPs up around sunrise for our north central counties. Skew t soundings show good shear and plenty of instability that if the MCS is just one lone supercell it could be impactful in the ability to produce large hail in the morning. Tuesday`s setup will depend on what develops through the morning as it looks like the MCS will continue to dive south and east into the more moisture rich air and have upscale expansion along a frontal boundary in central Kansas. The HRRR is thinking a pretty stout outflow boundary will develop and push at least into the eastern third of our CWA. A dryline will also develop during the day in our southwest and we should see an area of good convergence during the afternoon between the moist and dry air roughly somewhere around highway 283. The CAMs once again vary in where the initiation starts but the highest confidence looks to be in our southeast zones where CAPE values will be ~ 3000 J/kg and 0-6 km bulk shear values increase to > 40 kts by the late afternoon. The main question will be if the CAP from the outflow holds or not and based on the latest Skew-t soundings around PTT and P28 it should erode. This environment would certain support some large hail potential and perhaps a brief window for an isolated tornado between 6-9 pm with SRH values increasing to around 150-200 m2/s2. Tuesday evening the convection that does develop should move out of the area as the vort max & forcing moves into central Kansas. .LONG TERM...(Wednesday through Monday) Issued at 239 PM CDT Mon May 8 2023 Key messaging will be the chances of severe weather for Wednesday and Thursday. The setup for severe weather will be dependent on the track of an upper low coming in from the Pacific coast and then being directed north and east along the southwest flow aloft. Wednesday the center of the upper low should be around the 4 corners region and the upper level winds will start to become difluent in the central plains. We should see a shortwave eject out of the Rockies into western Kansas. A dryline should set up in the late afternoon around highway 283 by late afternoon. With skew t soundings showing around 40 m/s 0-6 km shear and CAPE values around 2000 this would support an environment of some large hail potential for any storms to form. The downside for storm potential at this point is the forcing still looks somewhat weak as we will still be under the influence of an upper ridge with the better forcing not arriving until during the night. Thursday...while the setup looks better for severe weather, the confidence on where the severe weather will occur is still somewhat low. Most of the long term models and ensembles prefer a track which takes the upper low into northeast Colorado and negative tilt trough through central Kansas and Nebraska. These setups also bring in the forcing earlier in the day with parts of western Kansas being in the area of forcing by sunrise. This would support more eastward momentum for the dryline and may only have our eastern third counties in a chance of storms. The outlier is still the deterministic Euro which is also slower in the timeframe and further south. This would give much of the area the best chance of more widespread strong to severe storms. We may start to see a shift in where the severe risk sets up for the updated day 3 to areas more into central Kansas. For the areas that stay in the moist air the CAPE and shear values are looking good for another round of storms with large hail and gusty winds potential. The rest of the long term looks more benign as the storm system exits on Friday and surface and upper level winds turn more northeasterly through the weekend which would bring in more cool stable air. Rain chances are possible mainly along the Oklahoma border for Saturday night into Sunday as a slow moving upper low moves through Texas. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1111 PM CDT Mon May 8 2023 VFR is expected through TAF pd. If showers/storms located across NE CO NW KS hold on, then KHYS may see VCTS/CB activity Tuesday morning. Will keep VCTS/CB groups in for that TAF. Tranquil weather is expected for the rest of the terminals through the overnight hours. Patchy AM fog may stay SE of the terminals. E to SE winds 15-30 kt will continue through much of the period. Right now confidence is too low to add TS in the TAFs for Tuesday evening. Early consensus shows that KDDC/KHYS could end up likely to be the most impacted. && .PRELIMINARY POINT TEMPS/POPS... DDC 58 91 61 86 / 10 20 20 40 GCK 56 91 59 86 / 10 10 10 30 EHA 53 94 59 86 / 10 10 10 40 LBL 56 94 59 87 / 10 10 10 30 HYS 58 86 60 85 / 30 40 50 50 P28 62 90 63 84 / 20 40 40 50 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Tatro LONG TERM...Tatro AVIATION...Sugden
Area Forecast Discussion
National Weather Service Des Moines IA
1042 PM CDT Mon May 8 2023 ...Updated for the 06z Aviation Discussion... .DISCUSSION.../Tonight through Monday/ Issued at 236 PM CDT Mon May 8 2023 Key Messages: -Isolated to scattered convection this evening north. -Relatively quiet into Tuesday. -Chances for convection from time to time Tuesday night into the weekend. Severe potential appears low at this time. Stratus lingered across a good portion of the forecast area this morning but has become more cellular as daytime heating has progressed. A few showers have developed in northeast Iowa along a narrow convergence axis and these are likely to pose some limited rain threat to the far northeast CWA over the next few hours. Additional showers and convection is expected in the northwest where weak convergence should lead to development by early evening. Soundings are relatively dry near surface in this area which may lead to gusty winds near this activity. Modest CAPE may also lead to some hail production with the strongest cells but in most cases this is expected to remain sub-severe. The activity is mostly diurnally driven and is expected to fade by late evening with quiet conditions the rest of the night. A return to weak warm advection is expected on Tuesday although the main push of moisture remains west of the state. Relatively quiet weather is anticipated for much of the day with some shower activity grazing the far north associated with a weak shortwave passing through the Dakotas and into Minnesota. Guidance begins to vary a bit more into Tuesday night with GFS and some CAMS, namely the HRRR bringing an MCS across Nebraska on nose of low level jet across the Plains. This impinges on western Iowa by Wednesday morning with decent rainfall. The Euro and NAM remain farther west and much more muted with the MCS development during the night with little impact into Iowa on Wednesday morning. Ensembles appear to lie somewhere in the middle and given the fickleness of convection, PoPs have gone this middle road. Thereafter, the upper flow consists of ridge across the central US as an upper low moves from the southwest and into the Plains by Saturday. Iowa remains in an area of persistent warm advection along periods of modest moisture transport providing chances of precipitation from time to time. With the proximity of the ridge, the shear profile weakens in the soundings by midweek which should limit the overall severe weather threat during this time. Temperatures during the week are expected to remain at or above normal as the upper ridging remains in place. && .AVIATION.../For the 06Z TAFS through 06Z Tuesday night/ Issued at 1037 PM CDT Mon May 8 2023 Last remnants of the storms are weakening as they move into northeast Iowa. Next aviation concern is potential for fog development overnight. With clearing skies, light winds, and ample low level moisture in the wake the last 2 days` rainfall, there is potential for areas of fog, especially in the eastern and northeastern parts of the forecast area closer to the surface ridge axis. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION...Cogil AVIATION...DMD
National Weather Service Kansas City/Pleasant Hill MO
704 PM CDT Mon May 8 2023 .Discussion... Issued at 254 PM CDT MON MAY 8 2023 Key Messages: - Isolated Thunderstorms South of Interstate 70 Possible This Afternoon - Above Normal Temperatures This Week - Multiple Rounds of Showers/Storms This Week Discussion: The trough axis over the western CONUS that provided persistent southwesterly flow over the weekend has lifted into the Canadian Prairie provinces. This has resulted in zonal flow at the mid-levels this morning. Surface analysis is a bit sloppy this morning, there are few outflow boundaries that have been floating around southern Missouri that emanated from the MCS late last night and early this morning. The surface cyclone also stalled to our northeast a bit, and the approaching cold front became a stationary boundary overnight. This afternoon though, that has been moving slightly southward, providing some cumulus clouds out there. The increasing H5 heights have provided enough subsidence to prevent dense cloud cover across the area. Insolation has been present on both sides of the boundary, and overall has actually weakened the temperature gradient somewhat throughout the afternoon. Only a subtle shift in wind direction has been noted with its passage. This has allowed for temperatures to bounce back up despite the strong evaporative cooling with the previous rain showers and approach of the cold front. For the rest of this afternoon, the boundary moving south in conjunction with a weak remnant outflow may produce some isolated to scattered shower/storm activity in our far southern counties. Areas south of Interstate 44 though are more likely for wider coverage of storms. There is a decent degree of instability building along and south of I-44 with some wind shear along the boundary that may support an isolated severe storm. The HRRR and other CAMs have not been overly robust with production for our southern counties though, thus will call the overall threat low. There is another H5 trough moving toward the west coast associated with the stronger PV anomaly that remains over the western CONUS. The general response ahead of this for the Central CONUS will be amplified ridging, with lower-level flow turning south to southwesterly. This will continue to keep afternoon high temperatures this week well above normal. For the rest of the work week, the inner-quartile max temperatures are in the 80s, with overnight lows in the 50s. Even though the pattern will generally be described as a ridge, would anticipate multiple vort maximums ejecting from the PV anomaly out west that will present localized short periods of height falls. With the WAA and moisture transport back into the area, would expect there to be some degree of kinematic forcing that will bring multiple rain shower and thunderstorm opportunities to our forecast area. Late Tuesday, first wave comes through and concentrates convergence mainly along the Interstate 49/29 corridor and westward. This continues into Wednesday morning. The instability axis is strongest just west of the forecast area, and overall shear is weak. Therefore looking at just general shower/thunderstorm concerns late Tuesday through Wednesday. Better chances for strong to severe storms will be westward over the Plains. Thursday, H5 trough is progged to lift out of the four corners region. A strong surface cyclone develops downstream with strong dCVA, and a surface response extends into the region strengthening southerly flow and moisture transport. This will allow for more widespread precipitation potential across most of forecast area. Expecting stronger instability to develop across the area that will support thunderstorm activity. While there will be a secondary short- wave and localized vort max across our area, the stronger flow will stay with the main trough axis. This keeps better deep layer shear over the High Plains and toward the Front Range, and thus the potential for organized severe potential is well west of the area. However, the rainfall will certainly be welcomed for areas still experiencing drought conditions. Heading into the rest of the weekend, the H5 trough likely closes off somewhere between the central and northern High Plains and will maintain low-level meridional flow across the region. Most ensemble members keeps multiple rounds of rain showers and thunderstorms through the weekend. There is not any clear signal for severe weather at this time, will just need watch the position of that trough. If the stronger flow moves further east, the potential could increase for organized activity. With respect to rainfall across the area, several ensemble members bring between 1 and 2 inches of QPF across most of the forecast area between Tuesday afternoon and Saturday afternoon. Localized amounts could certainly be greater in some locations depending mostly on convection occurrence and then stratiform rainfall. The POP forecast may look like a complete wash out over the next 7 Days but with the ridge in place there will be dry periods with warm temperatures. && .Aviation...(For the 00Z TAFS through 00Z Tuesday Evening) Issued at 703 PM CDT MON MAY 8 2023 VFR conditions continue through much of the overnight. There is the potential for some BR/FG development as winds calm toward sunrise. Confidence is higher in BR/FG formation near the river valleys (STJ & MKC). A dip to IFR conditions is possible. Winds pick up after sunrise quickly dissipating any FG/BR impacts and returning VFR conditions. && .EAX WATCHES/WARNINGS/ADVISORIES... KS...NONE. MO...NONE. && $$ Discussion...Krull Aviation...Pesel
forecast discussion, the NBM probabilities continue to indicate
greater than 50% chance of at least 3 inches of rain from Friday
through the weekend. While this is a good sign that a lot of the area will receive beneficial rainfall, there is the concern for Flash Flooding, if too much rain comes down in a too short of a period of time. Otherwise, expect for cooler daytime temperatures with all the cloud cover and moisture while the overnights will remain warm and humid. Stay tuned to the forecast during the days ahead as confidence increases leading up to this potential heavy rainfall event. && .AVIATION... (00Z TAFS) Issued at 623 PM CDT Mon May 8 2023 A cluster of SHRA/TSRA will impact KAUS in the next few hours and have gone with TEMPOs through 03Z. As SHRA/TSRA get further organized over west central Texas and near the Rio Grande this evening they may impact KSAT/KSSF overnight and have replaced TEMPOs with VCTS. Then, SHRA/TSRA will redevelop on Tuesday and have maintained PROB30s for the afternoon hours. Otherwise, VFR skies turn MVFR overnight, then gradually lift on Tuesday. Light to moderate S to SE winds prevail. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 70 85 68 81 / 10 50 30 50 Austin Bergstrom Intl Airport 68 84 66 80 / 10 50 30 50 New Braunfels Muni Airport 70 85 68 81 / 20 50 30 50 Burnet Muni Airport 67 84 66 81 / 30 40 20 40 Del Rio Intl Airport 71 93 72 90 / 30 30 40 20 Georgetown Muni Airport 68 84 66 79 / 10 50 30 50 Hondo Muni Airport 69 87 69 84 / 30 40 30 40 San Marcos Muni Airport 69 84 67 80 / 20 50 30 50 La Grange - Fayette Regional 72 82 69 81 / 20 60 40 50 San Antonio Intl Airport 70 85 69 81 / 20 50 30 40 Stinson Muni Airport 71 86 70 83 / 20 50 30 40 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Short-Term...04 Long-Term...05 Aviation...04
Area Forecast Discussion
National Weather Service Grand Forks ND
1032 PM CDT Mon May 8 2023 .UPDATE... Issued at 947 PM CDT Mon May 8 2023 Showers have cleared out but clouds are sticking around. Looks like the southern valley will be most at risk for more dense fog this evening as they are clearer, but wouldn`t rule out fog under the cloud deck as it will be pretty moist and winds will be light overnight. Forecast remains on track. UPDATE Issued at 640 PM CDT Mon May 8 2023 Some showers could still linger in the area, but most of them have lost their juice with the cloud cover and the sun setting. Fog still looks to be a possibility into early Tuesday morning, but impacts and where the fog will be is uncertain. && .SHORT TERM...(This evening through Tuesday night) Issued at 245 PM CDT Mon May 8 2023 Key Message - The degree of clearing/decrease of clouds tonight will play into many other components of the short term (fog later tonight, high temps Tue, etc.) The regional radars continue to show a nearly stationary line of light showers between Rugby, Harvey and Cooperstown. Looking at water vapor imagery, this looks to be the pivot point between one nice circulation up near Brandon Manitoba and another lobe of short wave energy moving along the North and South Dakota border south of Bismarck. The 12z model runs initialized these features pretty well overall, with the wave south of Bismarck expected to continue to push nearly straight east, into the Red River Valley and adjacent area of west central Minnesota tonight. The SPC meso page shows some weak instability along the Dakotas border now and some higher mid level lapse rates. However, there has just not been much sun or warming today in this FA. That hasn`t been stopping the HRRR from generating spotty showers along the I94 corridor in southeast North Dakota late this afternoon into the early evening. Outside of this area, there have been a few spots still reporting drizzle. All precipitation activity should wane after sunset. The question then turns to how much clearing may occur tonight. There is more cellular cumulus along the Dakotas border, which may favor some clearing south of I94 tonight. However, surface winds should continue to remain on the lower end, so if there is clearing, more fog could develop. Fog and cloud cover could last well into Tuesday morning, with some portions of the FA keeping mostly cloudy conditions through the rest of the day as well. There could be some sunny or partly sunny areas as well, it is just quite difficult narrow that down. The next batch of precipitation begins to move northward into the FA late Tuesday afternoon or night, so more clouds and wet conditions. .LONG TERM...(Wednesday through Monday) Issued at 245 PM CDT Mon May 8 2023 Key Messages: -Continued SW flow keeps the pattern aloft active through the end of the work week. Temperatures warm and stay above average. NW flow takes hold this weekend and early next week. -Chance for some thunderstorms Wednesday evening/overnight and periodically near the end of the work week. Otherwise, rain showers continue through the long term periodically. Discussion: Upper level flow continues to be out of the SW in the 500-250mb level. The trough out west digs in deeper toward the SW United States and the ridge out east amplifies. This helps to bring temperatures into the upper 60s for Wednesday and the low to mid 70s by the end of the work week into the weekend. This adds moisture to the area and is noted in the 700mb level where moisture advection is fairly present. PWAT values range between an inch and 1.5 inches. Comparing this to climatological averages we are sitting at the 95- 97.5th percentiles for Thursday and Friday. This means higher than normal PWATs are a possibility end of the work week. For Wednesday, its on the lower end, with around 0.75-1.0 inch PWATS. 24 QPF could reach over 0.5 inches. The probability of this occuring starting Wednesday is 30-40% chance for the forecast area. 48 hour QPF Thursday through Friday has the potential to reach over an inch in some areas. Turning toward the chance for thunderstorms Wednesday, the main synoptic pattern favors the moisture and instability across the area. CAPE values reach 1000 J/kg and moisture advection is modest in the mid levels. The one lacking factor is the timing of the system and the shear component to fuel the thunderstorm development. Winds have more directional component then speed within the lower levels of the atmosphere. The strongest shear is also during the daytime when the system is still working its way into the region. The timing of the shear on top of the instability/moisture is not quite lining up. This plays the biggest role in development. The chance for thunderstorms are there, but if the atmosphere can`t line up the ingredients the severity starts to become more uncertain than it already is. The chance for thunderstorms are there, but strong to severe storm chances are low in predictability at this time. Continuing chances for thunderstorms are possible end of the work week and into the weekend, but instability looks limited as flow starts to shift toward the NW. A ridge begins to build into the western United States setting up a NW flow aloft and allowing clippers to move across the region. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1032 PM CDT Mon May 8 2023 Fog will be the main issue in this TAF period. Winds will be light through the entire period, and it looks increasingly likely there could be fog Tuesday morning. Not just limited to clearer TAF sites, but all could see at least patchy fog. Some rain showers could develop Tuesday afternoon, and could be thunderstorms as well. MVFR will be predominant conditions through Monday night and Tuesday. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...AK SHORT TERM...Godon LONG TERM...Spender AVIATION...AK
Area Forecast Discussion
National Weather Service Grand Rapids MI
1024 PM EDT Mon May 8 2023 LATEST UPDATE... Update .UPDATE... Issued at 1019 PM EDT Mon May 8 2023 The main change to the forecast was to add patchy fog to the marine forecast. Webcams from around South Haven are showing fog developing. The latest HRRR does indicate fog in and around the nearshore waters tonight. Earlier 18z runs suggest the fog may be an issue over the next couple of periods over the nearshore waters so we will need to monitor trends beyond tonight. && .DISCUSSION...(This evening through next Monday) Issued at 323 PM EDT Mon May 8 2023 --Evening Rain, Decreasing Clouds Late-- Solid area of rain associated with mid level shortwave continues to advance slowly east from Lk MI/WI. Dry air below 8000 ft should cause this to decrease in intensity and coverage to some extent, with the rain becoming more scattered after 00Z per CAM guidance. The rain ends after 06Z with the passage of the shortwave, then a gradual clearing from north to south takes place as drier air/subsidence filters in. --Pleasant Tuesday through Thursday with Warming Trend-- Surface ridging and very dry air mass dominates our weather Tuesday through Thursday leading to clear to partly cloudy skies. Building upper ridge allow temps to moderate from around 70 on Tuesday to near 80 by Thursday and humidity levels will be in the quite comfortable/pleasant category due to dew points only in the 30s and 40s. The dry air will also promote chilly overnight temperatures. --Rain Risk Returns by the Weekend-- As we approach the weekend an upper low begins to drift our way from the Plains then is eventually absorbed by another trough dropping in from the northwest over the weekend. Confidence is currently low regarding the coverage/probability of rain/storms Friday into Saturday as a warm front and higher PWATS/dewpoints lift in our direction. Latest deterministic solutions are most aggressive with rain on Sunday when a robust northwest flow shortwave is passing through the area. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 733 PM EDT Mon May 8 2023 Radar trends show the area of rain diminishing over the TAF sites as a result of the weakening low pressure system pulling away from the region. A weak area of high pressure is forecast to build in for Tuesday. Dry air advection is expected and should result in VFR conditions through the period. Also...the pressure gradient is shown to be weak...which will support wind values mostly under 10 knots. && .MARINE... Issued at 323 PM EDT Mon May 8 2023 High pressure will build into the Great Lakes Region Tuesday and remain in place through Thursday. Winds and waves will stay below advisory criteria, although onshore lake breezes related to differential heating at the land/lake interface could result in briefly stronger winds from mid afternoon through early evening. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...None. && $$ UPDATE...MJS DISCUSSION...Meade AVIATION...MJS MARINE...Meade
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1015 PM EDT Mon May 8 2023 .SYNOPSIS... An active weather pattern with above normal temperatures will remain across the area through Tuesday, along with chances of showers and. thunderstorms. A cold front crosses our region from the north by late Tuesday. By Wednesday, drier high pressure will build in from the north and remain into the weekend. Moisture will increase again over the weekend as a cold front approaches from the northwest. && .NEAR TERM /THROUGH TUESDAY/... As of 1010 pm EDT: All remains quiet over the western Carolinas and northeast Georgia late this evening, with stabilization underway across the region. Upstream, radars across western Kentucky are showing convection developing and beginning to organize. This will likely compose the MCS that recent HRRR runs have propagating toward the southern Appalachians overnight into daybreak. Will gradually bring PoPs back to the western mountains for the overnight hours, with a peak of likely PoPs around sunrise near the TN border. With limited instability east of the mountains, it remains questionable how much activity can survive east of the Blue Ridge Mountains after sunrise. Minimum temperatures should be similar to those observed this morning in most areas. A cold front approaching from the north tomorrow morning will settle southward into the region through the afternoon hours. Once again, lapse rates will not be great on Tuesday afternoon, but temperatures will rise to about 8-10 degrees above climo given warming thicknesses ahead of the boundary. Model profiles should build slightly better surface-based instability of 1500-2000 J/kg by late day mainly in the southern half, if any debris clouds clear quickly enough, along with about 20 to 30 kt of deep layer WNW flow shear. A damaging wind threat could develop Tuesday afternoon if this materializes, but uncertainty is rather high with regard to the environment. Max temps in a few southern tier locations could touch 90 degrees. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... As of 200 pm Monday: Isolated convection may linger into Tue evening, mainly across southern areas before a lower theta-E air mass completely overtakes the CWA. This more stable air mass will otherwise predominate through the short term, bringing an end to the relatively active convective weather. Still cannot completely rule out a stray diurnal shower along the ridge tops Wed and Thu afternoons, but that potential doesn`t even warrant a 20 PoP. Temperatures are forecast to be very close to normal through the period. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... As of 210 pm Monday: Rather weak NW flow will persist atop the region through much of the extended, as an upper ridge axis lingers in the vicinity of the Miss Valley, before beginning to flatten next weekend as a series of upper lows and short wave troughs impact the northern Conus. Low level moisture will slowly increase across the forecast area, as surface high pressure/sprawling ridge over the western Atlantic gradually weakens and oozes east. The potential for isolated/scattered diurnal convection (mainly mountain-centric) is expected to return as early as Friday, gradually ramping up easy day through the end of the period, with PoPs reaching their peak (generally solid chance) next Monday, when the global models indicate height falls and an associated frontal boundary impacting the Southeast and Mid-Atlantic. Otherwise, after one more day of near-normal temperatures on Friday, the main story will become the heat, as temps are expected to be as much as 10 degrees above climo next weekend into Monday. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... At KCLT and elsewhere: Terminals will remain dry through late evening and early overnight as profiles continue to stabilize. MCS remnants may return to the mountains from the northwest overnight and that will be the next best chance for any showers and thunderstorms near KAVL. A VCSH is carried there after 09Z. Scattered, possibly strong, convection could then develop Tuesday afternoon as a cold front settles south into the terminal forecast area. Conditions will be generally VFR at all sites except under any heavy rain showers or storms, with perhaps some MVFR valley fog around KAVL at daybreak. Expect mainly SW to WSW winds tonight, except NW flow at KAVL. Winds will toggle more WNW to NW through Tuesday with the approaching front, then northerly with fropa late in the period. Will continue to feature PROB30 for TSRA during peak heating Tuesday, and gusty winds may need to be added as we get closer in time. Outlook: High pressure and drier conditions are anticipated to move in by mid-week and persist through Friday. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...DEO NEAR TERM...HG SHORT TERM...JDL LONG TERM...JDL AVIATION...HG
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
911 PM CDT Mon May 8 2023 .SYNOPSIS... Issued at 910 PM CDT Mon May 8 2023 High pressure will drift into the Great Lakes region, keeping our weather dry through Wednesday. While high temperatures will still be well into the 70s, northeast winds will result in much less humid conditions. && .UPDATE... Issued at 910 PM CDT Mon May 8 2023 High pressure behind the cold front that just finished pushing south of the forecast area will bring an end to any precipitation chances, while a cooler air mass moves in bringing lows well down into the 50s tonight. An area of low cloud cover in northern IL pushing southwestward in the northeast winds could result in patchy fog overnight, mainly Peoria northwestward, but the cloud cover and light breeze should prevent this from becoming dense. Have added patchy fog for tonight for this, and have trimmed out all PoPs the remainder of the night. 37 && .SHORT TERM... (Through Late Tuesday Night) Issued at 252 PM CDT Mon May 8 2023 Main forecast issue for this period is with the potential for any strong/severe storms through about sunset. Latest surface map shows a few boundaries across the area, with the one of interest for convection extending from near Bloomington and Springfield southwest toward the St. Louis metro. With a fair amount of sunshine this afternoon south of I-72, SPC mesoanalysis shows minimal cap and surface based CAPE`s over 2000 J/kg. Morning HREF shows the CAPE`s north of I-70 will begin to be suppressed a bit later this afternoon as the boundary sinks southward, and morning CAM`s all suggest the main threat of strong/severe storms will be south of I-70. Just how far south that occurs is still up for debate. The latest HRRR has been suggesting our bottom 3 counties (Clay, Richland, Lawrence) as being the initiation point, while a few other CAM`s place it a bit closer to the boundary, which will be near I-70 by 4 pm. High mid-level lapse rates would suggest hail being a concern again, along with damaging winds. In any event, the threat should be over by sunset as the boundary moves closer to the Ohio River. Behind the front, a northeast flow sets up as high pressure settles into the Great Lakes and drifts through the Midwest into mid week. While temperatures still reach the mid 70s to around 80 degrees both Tuesday and Wednesday, humidity levels will be much more tolerable with dew points only in the 40s to around 50. Geelhart && .LONG TERM... (Wednesday through Next Monday) Issued at 252 PM CDT Mon May 8 2023 The extended period begins Thursday with a warm front arriving from the south ahead of a sfc low lifting northeastward across the Plains. Both the GFS and ECMWF have a nose of 16+ degC 850mb temps spreading into Illinois from the southwest with the northeastward advection of the EML by late Thursday and especially Friday. As a result, increasing mid level lapse rates may foster sufficient instability for thunder and perhaps even some small hail with storms both Thursday and Friday. However, the deterministic models are each showing little QPF across central Illinois on Friday, implying that with the warm front to our north, we may be capped and without a sufficient trigger for convective initiation. Nonetheless, any outflow boundaries from Thursday`s showers/storms could ignite updrafts in an increasingly unstable air mass. NBM suggests that probabilities will increase from 20-40% to 40-70% (highest south) for SBCAPE values over 1000 J/kg between Friday and Saturday, indicating the best potential for thunderstorms (possibly severe) will be Saturday. Fortunately, each deterministic model suggests the upper level trough will be weakening as it draws near to us, which would hopefully limit shear enough (GFS forecast sounding suggests only 20-30 kt of 0-6km bulk) to significantly inhibit the potential for organized thunderstorms. At this time, CSU`s machine learning algorithm has only a 5% contour for severe potential over central Illinois on Saturday, and CIPS has nothing. Given the low predictability of severe weather at that time range in the absence of high confidence in a significant forcing mechanism, and that probabilities are looking lower than 15%, SPC doesn`t have us outlooked. Temperatures will be pleasant through at least the first three days in the extended forecast period. Roughly 60% of the Low Resolution Ensemble Forecast (LREF) system have highs greater than 80 degF in Lincoln on Friday, while 75% have highs 80+ on Saturday. Cooling behind some sort of washed out cold front appears likely by Sunday and especially Monday, when around 40% of the LREF have high temps less than 70 degF. Fortunately, no ensemble members thus far have sub freezing overnight low temps early next week and NBM suggests chances for a freeze are less than 2%, so at this time the potential for a hard freeze (and even a frost) appears quite low. Bumgardner && .AVIATION... (For the 18z TAFs through 18z Tuesday Afternoon) Issued at 1220 PM CDT Mon May 8 2023 Ceilings below 3,000 feet are fairly widespread around KPIA/KBMI at midday, though scattered further south. A southward push is expected later this afternoon and especially this evening, in the wake of a cold front. As winds turn more toward the northeast, there will likely be a period of IFR conditions (HREF suggesting 60-90% chances of this between 06-12Z, before the low ceilings push southwest of the TAF sites. Conditions should improve by mid morning Tuesday. Precip-wise, while some isolated thunder can`t be ruled out near KBMI/KCMI mid/late afternoon, the main threat will be further south. Will not include a VCTS mention at this point. Geelhart && .ILX WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch until 8 AM CDT Tuesday for Sangamon. && $$ WFO ILX
Area Forecast Discussion
National Weather Service New Orleans LA
838 PM CDT Mon May 8 2023 ...New UPDATE... .UPDATE... Issued at 828 PM CDT Mon May 8 2023 Update already issued to raise precipitation chances for at least the next 6 hours. Since sunset we`ve seen convection develop between Baton Rouge and McComb in an area of enhanced instability where CAPE values are approaching 3000 J/kg and LI`s of -6 to -7. 00z LIX and JAN soundings would indicate conditions would be less favorable as storms move northeast or east with lower layers fairly dry, so would expect storms to eventually weaken. 00z HRRR does hint at potential for precipitation toward sunrise further east toward the Mississippi coast, and will continue to monitor that trend. Didn`t address anything beyond 12z Tuesday, as convective trends over the next 6 hours or so may dictate timing of any storm development during the day. Will not rule out an additional update later this evening as conditions dictate. RW && .SHORT TERM... (This evening through Tuesday night) Issued at 156 PM CDT Mon May 8 2023 Showers across the western tier have become a bit more scattered as they move east of I55 this afternoon. In this region there has been a bit more surface heating/insolation, which is helping ignite isolated convection along the southshore of the Lake. This activity remains rather weak, but there have been several lightning strikes with these cells. Overall, shear is fairly weak, but instability isn`t lacking. H5 temps are also rather cool and may cool another 1C or two as the upper level impulse moves overhead. Latest CAMs still vary somewhat with this afternoon/evening convection. As the early shower/cloud debris moves east, this may limit convection slightly. However, globals (which have been slightly more reliable over the last several days) continue to indicate rain potential into the early evening before chances drop with the loss of surface heating overnight. Regardless, cannot rule out a stronger updraft or two this afternoon or early evening. Overnight, with the flow weakening and recent rainfall, some patchy fog may be possible, especially over interior south MS and the Florida Parishes (aka more fog favored locations). Another subtle impulse moves into the region on Tuesday, which may again increase rain chances from late morning through the afternoon hours. Again, mesoscale models aren`t in much of agreement and even the QPF from globals have some timing went with a bit wider window for potential, but think the highest potential across the landbased zones given the pattern would be during the late morning into early evening respectively due to diurnal influences. (Frye) && .LONG TERM... (Wednesday through Sunday night) Issued at 156 PM CDT Mon May 8 2023 By Wednesday an upper low closes off across the upper Texas Gulf Coast and then progresses northward around the western periphery of a rather strong ridge over the Midsouth and MO Ozarks. This trough may bring a slightly higher chance of showers and storms across the western tier parishes/counties, but largely most of the upper level forcing will be just west of our CWFA. This feature eventually gets absorbed into the broader longwave across the Rockies going into Thursday. At the surface, pressure gradient tightens between a high pressure off the US east coast and a leeside low over the high plains. Southerly winds should gradually increase in response to the tightening gradient. From this point forward, globals tend to disagree in terms of QPF/POPs. This pattern seems to favor a more summer-like pattern so therefore it would be tough to NOT mention diurnally driven POPs with the boundary layer being rather moist. The ECMWF is the wetter solution, but the GFS still has some QPF signal during this time so no big changes outside of blending POPs with a little more weight on the GFS, especially with some upper ridging in both solutions as a weak Rex Block tries to develop over the SE US. (Frye) && .AVIATION... (00Z TAFS) Issued at 625 PM CDT Mon May 8 2023 All terminals currently VFR with all convection well east or west of all terminals. Main forecast questions are fog and convective threats/timing. Expect low cloud development overnight, as has occurred the last several nights with low end MVFR or high end IFR ceilings. Cirrus overcast and light onshore wind flow have generally prevented extremely low visibilities, and will only knock those down to 3-5SM. Should see improvement to any flight restrictions by 15z Tuesday. As has been the case for the last 4-5 nights, model guidance has been extremely mixed on convective development. With the exception of Saturday night, models have done a poor job of diagnosing overnight convective development to our west, not only regarding timing, but location as well. There are at least a few signs of possible overnight convection across terminals south of Lake Pontchartrain...KMSY/KNEW/KHUM, but not high enough confidence to buy off on it yet. Better signal is during the day on Tuesday, and will carry VCTS at most terminals by late morning or early afternoon Tuesday. && .MARINE... Issued at 156 PM CDT Mon May 8 2023 Generally, favorable marine conditions are expected through much of the week. However, in and around convection expected locally higher winds and seas. Southerly winds will begin to increase closer to the upcoming weekend. At least cautionary headlines will be needed as the low level flow strengths on the western periphery of a strong high pressure across the western portions of the Atlantic. (Frye) && .PRELIMINARY POINT TEMPS/POPS... MCB 66 85 66 85 / 30 50 20 50 BTR 71 88 69 88 / 30 50 10 30 ASD 70 87 69 88 / 20 40 10 20 MSY 72 86 71 87 / 40 40 10 10 GPT 70 84 69 84 / 20 40 10 20 PQL 68 86 67 87 / 30 30 10 20 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...None. GM...None. MS...None. GM...None. && $$ SHORT TERM...RDF LONG TERM....RDF AVIATION/UPDATE...RW MARINE...RDF
Area Forecast Discussion
National Weather Service Marquette MI
728 PM EDT Mon May 8 2023 .SHORT TERM...(The rest of this afternoon through Tonight) Issued at 230 PM EDT MON MAY 8 2023 Sfc high pressure is building in from the north and fighting two shortwave lows this afternoon through tonight, one to our west digging through the Upper Midwest and another passing through the Lower Midwest. This is bringing mid- to high-level cloud cover across the CWA today into this evening, with some low-level clouds possibly moving over the far west late tonight. Still, temps today have already gotten into the mid to upper 60s in many of the interior areas, and spots have already broken 70F; with cloud cover breaking up over most of the area tonight, expect lows to drop into the mid 40s over the far west to mid 30s in the interior east/central. As for rain chances, CAMs show that there is a chance that some showers and possibly a thunderstorm or two moves over the far west late this afternoon and continues into this evening. That being, the recent RAP and HRRR guidance has really backed off on precip chances over the far west, with the HRRR almost completely getting rid of the rainfall altogether. Therefore, I`m keeping the far west under a low chance (20-30%) for rain showers, with thunderstorm chances being around 20% or less. Moving into late tonight, thinking that fog is going to develop over the western CWA as less dry air is expected at the sfc; the fog could be dense in spots. However, the further east you go in the U.P., the lower the chance of fog tonight; don`t expect any east of Marquette and Menominee counties. .LONG TERM...(Tuesday through Monday) Issued at 402 PM EDT MON MAY 8 2023 The big picture of the extended forecast is below normal precip and and above normal temps through much of the forecast. The ECMWF EFI is showing anomalous temps values through Saturday night which is supported by positive 500 mb height anomalies through Saturday between 100 to 150 meters. Some chances for rain arrive late week and continue into the weekend will be followed up by slight chances on Monday before dry conditions return again. With the ridging building in through mid-week, more sunshine is expected to mix in through which will be a nice change from the gloomy clouds and fog that have filled the last few periods. Starting Tuesday, mid-level ridging begins to build in over the UP with a surface high pressure settling south through Ontario Tuesday morning and the into Upper Great Lakes the rest of the day. This will yield light winds/possibly variable winds, plenty of sunshine, and dry conditions. I continued the forecast for lake breeze development on Tuesday with the warmer temps expected to be warmer than Lake Superior surface temps. A few of the CAMS do highlight some stray showers mainly over the far west with the RAP and HRRR bringing them along the WI/MI state line through the evening hours. This could be supported by the mid-level shortwave that is most visible in the NAM. However, with surface high pressure building in and not much there for forcing I am not very convinced. Also a deep layer of dry air up to the 850mb level builds in across the UP as noted in the BUFKIT soundings will work against any potential to develop showers as well as mix down some drier dew point temps, especially in the east. Wednesday through Thursday morning will see the mid-level ridging continue over the Upper Midwest and the surface high pressure track southeast toward the Atlantic, continuing the mostly dry weather. A few diurnal showers alongside a few potential rumbles of thunder are possible Wednesday afternoon. Otherwise dry weather and partly cloudy skies are expected on Wednesday. Thursday reintroduces chances for precip across much of the UP as a mid-level short wave tracks into northern Wisconsin. Confidence in much accumulation or even any showers at all with this initial wave is still low as the past 4 GFS and ECMWF ensemble QPF probabilities of greater than 0.1 inches are all low (20% to 40% chance). A closed off mid-level low will track northeast off the Rockies on Thursday and then take a north to north- northeast track through the Dakotas and Minnesota Friday/Saturday. This system brings the better shot for precip across the UP. If the drier trend continues this week, POPs may need to be brought down for the late week systems. Temps look to drop down near normal late in the weekend and into next week. With dry air moving in early next week, more sunshine and dry weather should be expected. Also with less precip in the forecast, flooding risks should taper down through the week with some exceptions into the weekend. RHs on Tuesday will drop around 30% along light winds over the central/eastern UP yielding borderline elevated fire weather conditions. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 709 PM EDT MON MAY 8 2023 at IWD, A low pressure trough over the western UP has been the focus for isolated to scattered showers over western Gogebic and Ontonagon counties early this evening. Will keep VCSH in the forecast this evening for IWD and then with added moisture from the showers expect a gradual lowering of ceilings to MVFR this evening and then lowering to IFR in patchy fog overnight. Patchy fog should dissipate by late Tue morning with improvement to MVFR conditions. Drier air under high pressure ahead of the western UP trough will result in dry conditions should yield VFR conditions through the period at CMX and SAW. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 402 PM EDT MON MAY 8 2023 Northeast winds gusting around 20 knots will continue through this afternoon across the western third of Lake Superior. With surface ridging continuing to build in through Tuesday, winds look to become light tonight below 15 knots. Light winds below 15 knots are expected across the lake through Wednesday night. Thursday will see generally southerly winds around 10 to 15 knots which will stay light overnight into Friday. Winds will back northeast on Friday and increase to 10 to 20 knots as a low pressure system tracks northeast into the Dakotas and Minnesota. Depending on the low`s track on Saturday, northeast gusts up to 25 knots are possible in the west third of the lake Saturday afternoon/evening. There is the potential for a few weak thunderstorms across the far western lake this afternoon, diminishing this evening evening with some showers continuing through the overnight hours. The primary hazards are a few lightning strikes and some brief periods of small hail. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...TAP LONG TERM...Jablonski AVIATION...Voss MARINE...Jablonski
Area Forecast Discussion
National Weather Service Morristown TN
1042 PM EDT Mon May 8 2023 ...New UPDATE... .UPDATE... Issued at 1029 PM EDT Mon May 8 2023 The MCV and associated convection across SE MO tonight will move southeast towards the Tennessee Valley tonight. Additional scattered showers and thunderstorms are forecast to initiate ahead of this MCV and along residual outflow boundaries late tonight as this feature moves across our forecast area between 08z and 12z. RAP guidance continues to indicate a marginally favorable environment for isolated strong to severe thunderstorms with MLCAPE around 1000 J/Kg along with relatively steep mid-level lapse rates near 7-7.5 deg C/km favorable for some hail risk. The thermodynamic profile is also resulting in DCAPE values of 900 to 1000 J/Kg which is sufficient for some damaging wind gusts with the strongest surface based convection. Deep layer winds will be on the rise overnight ahead of a stronger shortwave across the Great Lakes. This will increase effective deep layer shear to around 30 to 40 kt across the region which will help with storm organization. The severe risk remains low since thunderstorms are expected to generally weaken late tonight and early Tuesday morning, but there is at least a low risk for thunderstorms capable of some strong winds and hail between 08z and 12z Tuesday. Overall, the forecast remains on track with some minor updates to temperatures and PoPs based on current observations and expected trends. JB && .SHORT TERM... (This evening through Tuesday) Issued at 328 PM EDT Mon May 8 2023 Key Messages: 1. Another round of convection expected tonight. Severe chances seem low given overnight arrival. Discussion: Regional radar and satellite imagery show remnant MCS and likely an MCV moving east through eastern Kentucky this afternoon. Models have not resolved this well, but think there will likely be a few scattered showers and thunderstorms pop up over our Virginia counties and possibly far northeastern TN this afternoon and evening as this passes by. Otherwise, do not expect much in the way of any convection through late this evening as the region remains worked over from the storms that moved through yesterday and overnight. However, further west from the Ozarks ENE into the Ohio valley, another MCS is expected to form later this evening. This will eventually work its way southeast through eastern Tennessee. Given the overnight arrival time, severe chances seem to be low. This is supported by forecast soundings from across the CWA. An outside chance for some damaging winds could exist but otherwise expect this to just be another chance for some moderate rainfall. There`s some uncertainty with regards to what portions of the CWA will see this MCS move through. Current thinking is that the northern half of the forecast area will see the best coverage and PoPs reflect this. For tomorrow, expect any rainfall to gradually shift south through the morning hours, leaving most of the area dry by the afternoon hours. Temperatures will be a bit tricky, as they were today, given the potential for lingering convective debris cloud cover. Undercut NBM guidance a tad to hedge towards cooler than expected highs. && .LONG TERM... (Tuesday night through next Monday) Issued at 328 PM EDT Mon May 8 2023 Key Messages: 1. Mostly dry through the mid-week with increasing chances for rain and storms late week and into the weekend. 2. Above normal temperatures expected through the long term. Discussion: Shortwave ridging will build over the region Tuesday night into Wednesday along with surface high pressure transitioning southeast from the Great Lakes. The increased subsidence will result in sunny to mostly sunny skies with conditions remaining primarily dry. Some guidance hints at a few spots of weak returns Thursday afternoon, thus, PoPs has been limited to slight chance in the southern valley, along the Cumberland Plateau, and the GSMNP. More favorable moisture transport will return as we approach the late week, with PWATs increasing to around 1.3 inches per latest ensemble guidance. In combination with the aforementioned surface high pressure meandering further east and the above normal temperatures, conditions will become increasingly favorable for showers and thunderstorms in a typical diurnal manner. There is potential to have minor isentropic lift associated with weak southwesterly H85 flow, but given the low amplitude of the flow and no other significant forcing mechanisms on the synoptic scale have currently restricted wording to chance. Various impulses translating through the mean flow aloft late weekend and into the new week will further weaken the ridge. While there are discrepancies among any finer details, guidance generally has a low pressure system traversing the Ohio Valley with a west- east oriented front to our north. This results in increased chances in showers and thunderstorms. Temperatures through the long term will continue to be above normal, with even a slight warming trend into the weekend. && .AVIATION... (00Z TAFS) Issued at 653 PM EDT Mon May 8 2023 Scattered showers and thunderstorms are expected to develop along a weak cold front tonight and move southeast across the Tennessee Valley and Southern Appalachians with flight impacts expected at all TAF sites. Predominant VFR conditions are forecast, but periods of MVFR, and potential tempo IFR/LIFR, will be possible late tonight and early Tuesday within areas of heavier convection. Drier air arrives and winds shift to the NW/NNW on Tuesday afternoon with clearing sky conditions and decreasing chances of thunderstorms. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 65 85 59 83 / 50 30 0 10 Knoxville McGhee Tyson Airport, TN 63 80 56 80 / 60 40 0 10 Oak Ridge, TN 63 82 56 81 / 60 30 0 0 Tri Cities Airport, TN 60 77 50 78 / 60 50 0 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...CD LONG TERM....KRS AVIATION...JB
Area Forecast Discussion
National Weather Service Norman OK
1022 PM CDT Mon May 8 2023 ...New AVIATION... .SHORT TERM... (This evening through Tuesday) Issued at 246 PM CDT Mon May 8 2023 We have entered "mesoscale season", where forecast predictability becomes very low and each forecast is dependent on how the previous day`s storms evolve. Below is a snapshot of how the forecast looks right now, but things could change rather dramatically in subsequent forecasts. Thunderstorms are possible within two regimes this evening, although neither regime contains a super large chance of convection. The first area to watch will be in western north Texas, where a weak inverted surface trough across the Llano Estacado will lead to easterly surface winds and westward-surging moisture across the Caprock this evening. The 12Z HRRR and 12Z NAM 3KM show a comical difference in moisture quality - the NAM shows upper 60s dewpoints and 4,500 CAPE around sunset, while the HRRR shows upper 50s and 2,000, respectively. Both may be sufficient for rather short-lived, slow-moving multicell clusters capable of downburst winds and downpours. However, given very weak forcing, this is a low- likelihood scenario. The second, likelier scenario for thunderstorm development will occur this evening and overnight across north central Oklahoma. A subtle impulse will round the top of the shortwave ridge anchored over us, and most CAMs suggest that this impulse will be the impetus for CI along a frontal boundary lifting into southern Kansas after sunset. These storms will slowly sag southward into northeast Oklahoma. The best chance for thunderstorms tonight in our area will be north of a Stillwater to Cherokee line. Otherwise, expect lows tonight to drop into a soupy low-to-mid-60s as the dryline once again sloshes westward after sunset. Cloud cover will largely be regulated by any anvil debris from storms over or east of our area, but the night looks to be clearer to the west. Some patchy fog is possible in western and northwestern Oklahoma late as moisture surges in from the east. Storms may linger into the morning in north central and northeast Oklahoma, though they should decay not long after daybreak as the shortwave ridge strengthens over the Red River. Another impulse is expected to develop atop the ridge and intersect the frontal boundary tomorrow evening. This time, flow will be somewhat stronger in the frontal region and a supercell storm mode appears possible. There is some uncertainty regarding the northward advance of the front, with the NAM maintaining it near the OK/KS border and most other models lifting the front near I-70. The chance for organized severe storms will thus be dependent on that frontal location, and will be monitored in subsequent forecasts. There is an outside chance of a storm or two along the dryline in western OK and western north TX, but both forcing and deep-layer shear are incredibly poor in this region. A soupy airmass will remain in place across most of our area tomorrow with highs in the low 90s to the west and the mid-80s to the east. Meister && .LONG TERM... (Tuesday night through next Sunday) Issued at 246 PM CDT Mon May 8 2023 Tomorrow night, the core of the ridge will shift slightly north, bringing easterly flow aloft to the Red River region and raising heights further to the north. This will effectively kill any storms that are ongoing. The ridge axis will finally begin to shift eastward slightly on Wednesday as a powerful shortwave trough begins to overspread the High Plains. Some guidance shows a weak trough/MCV- like feature sliding northward through eastern Oklahoma and western Arkansas Wednesday evening. All told, this will probably mean two things: first, a break from the constant low storm chances that many areas have seen over the past week. Second, a break from the early summer impression that everyone has seen over the last week. Highs will drop into the low-80s area-wide with quite a bit more cloud cover than previous days. On Thursday, the High Plains trough will eject into the central Plains. There is some uncertainty about the exact placement of the 40-50 knot flow aloft by Thursday evening, but a best guess would say western Kansas. Even if western Oklahoma only sees glancing influence as the NAM suggests, subtle height falls and 35 knots of 500 mb flow across deep-layer moisture are often all severe weather events in this area require in mid-May. Trends will continue to be watched, but Thursday looks to be the likeliest day for impactful severe weather in our area. This coming weekend gives off strong "washout" vibes, particularly across southwest Oklahoma and western north Texas. This is due to a resurgent STJ, which will eject northeastward from Mexico in time to cut off the High Plains low and trap the cutoff across the southwest. Northwest flow across the northern Plains will encourage a synoptic-scale front to surge southward. The result will likely be a stalled frontal boundary somewhere in our area with plenty of Pacific moisture atop it, a classic recipe for high rainfall amounts. Meister && .AVIATION... (06Z TAFS) Issued at 1016 PM CDT Mon May 8 2023 Still expecting some low stratus and BR to develop late tonight into early Tuesday over central OK. Some IFR cigs will briefly be possible. Winds will remain southerly and less than 10 kt. Cirrus clouds will stream in from TX overnight too. There`s a low chance of showers and thunderstorms developing around 06-09Z across northern OK but confidence is far too low to include any mention of TSRA at PNC. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 87 65 85 65 / 0 10 20 20 Hobart OK 92 63 91 62 / 0 10 20 20 Wichita Falls TX 91 64 89 64 / 10 10 10 20 Gage OK 88 60 93 61 / 0 10 20 20 Ponca City OK 89 64 86 64 / 10 40 50 40 Durant OK 87 66 86 65 / 20 0 20 20 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && $$ SHORT TERM...04 LONG TERM....04 AVIATION...03
Area Forecast Discussion
National Weather Service Salt Lake City UT
227 PM MDT Mon May 8 2023 .SYNOPSIS...An unsettled pattern will continue through the weekend with several disturbances expected to bring convection to at least northern Utah today and Tuesday, with more widespread convection possible Wednesday. && .SHORT TERM (Through 12Z Wednesday)...A relatively chaotic spring-time pattern continues across the Interior West. Afternoon upper air and satellite analysis indicates a relatively strong shortwave trough crossing northern California. The attendant jet max is noted on satellite, with a broad area of upper level diffluence shifting into northern Utah. Additional shortwave troughs are noted upstream across the eastern Pacific. Current mesoanalysis suggests sufficient destabilization...with SBCAPE values near 500 J/kg. Latest RAP suggests this destabilization will continue with a broad area of SBCAPE values near 500-1000 J/kg by 00Z. Deep layer shear is averaging between 40-55kts across northern Utah. Given synoptic support combined with more than sufficient instability and deep layer shear, expect convection will continue to develop across northern Utah and Uinta County, WY into the evening. Looking at the CAMS and current RADAR trends, the evolution of this convection seems on track with a developmental quasi-linear feature noted near the Utah/Nevada border. Looking at the pre- convective environment, dewpoint depressions across western Utah are around 30 degrees or so. As one would expect, model soundings suggest inverted-v type profiles. Expect convection to continue to shift east with time into the Wasatch Front through Uinta County WY. The highest threat period for the Wasatch Front looks to be 4 PM - 7 PM. Given the degree of instability combined with deep layer shear and antecedent conditions, expect the threat of microburst winds and small hail with any deeper convection. With the shortwave trough shifting east, convection should gradually end from west to east through the evening. The next shortwave trough will drop south along the California coast Tuesday afternoon. Upper level diffluence will again set up across portions of western Utah. HREF ensemble mean SBCAPE values will again range around 250-500 J/kg across northern Utah, with deep layer shear around 30kts or so. CAMS are decidedly less impressed, with most convective activity confined to the western and northern border areas. This may be underdone and bears watching with the next forecast update. .LONG TERM (After 12Z Wednesday)...Two main periods of possible sensible weather impacts across the region in the extended forecast. The first comes Wednesday as scattered showers and thunderstorms move through the area in association with a trough passage, with relatively high snow levels to around 8.5-9k feet. The second potential impact is canyon or downslope winds along the Wasatch Front Saturday into Sunday as an unusual high over low (Rex Block) scenario develops across the West and supports a period of easterly flow over northern Utah. A trough axis passage on Wednesday as the main low center moves through the Four Corners will support the development of scattered showers and thunderstorms with with relatively steep low and mid level lapse rates. Flow will be very light under the trough axis, resulting in very little shear or even steering flow for that matter. Popup scattered shower and thunderstorms with around 500 J/kg of CAPE will largely struggle to organize given this environment, and briefly heavy rain showers are possible, especially over and tied to the higher terrain as anything that develops on the terrain will struggle to move off of the terrain in this environment. Thus some localized rain on snow could increase runoff potential over mid/high elevations where snow remain on the ground. Fortunately temperatures will continue to be seasonable in this pattern. By Thursday, the upper low will only move into the Colorado / Wyoming Front range, with eastern Utah still under the western periphery of its cyclonic flow aloft. Thus while we will be drying out on the back side of the low, there still will be enough moisture/support diurnal pop up showers and thunderstorms over the mountains, although becoming more isolated to widely scattered in nature. The more unusual pattern starts to develop Friday through the weekend, as ridge builds to our north over the Pacific Northwest into British Columbia and Alberta, while lower pressure remains in place over the Great Basin into the Southwest US. This Rex Block type setup starts a more unusual easterly flow across northern Utah that gets kicked off on Saturday as vort max on the back side of our aforementioned low gets pinched off and ejects westward across northern Utah all the way toward Northern California by late Saturday evening. This easterly flow sets up the potential for at least a period of gusty canyon winds along the Wasatch Front Saturday into Sunday. Digging into this setup a bit more - we can be very confident on the overall pattern as all clusters of the available 100 ensembles solutions between the GEFS/EPS/CMCE all show this Rex Block development with easterly flow across Utah. The main differences between the clusters comes down to the strength of the 700 mb easterly flow, and strength of the easterly surface pressure gradient that develops across northern Utah. Thus there is potential for a stronger downslope storm, however only about 20% of EPS members show wind gusts of 40 mph or greater at Hill AFB (proxy location for prime downslope location along northern Wasatch Front). Balancing the fact that all models are showing this easterly flow with the fact that there are several smaller scale details to iron out being a day 5/6 forecast, have started with introducing some sub- advisory level canyon winds in the forecast for the main canyons between Brigham City and Salt Lake City, and we`ll continue monitoring this setup for any stronger potential. && .HYDROLOGY...Rivers continue to run fast, cold and high area-wide. A reminder to keep pets on leashes and children away from these waterways for the foreseeable future. River flood warnings continue for the Bear River at Corinne, the South Fork of the Ogden near Huntsville and the Sevier near Hatch. A river flood watch remains in effect for the lower Weber River near Plain City. An areal flood warning is now in effect for the Bear River from the Woodruff Narrows northward to the Utah/Wyoming state line west of Sage Junction, WY. An areal flood watch remains in effect along the Little Bear south of Hyrum Reservoir. Over the next week, flows are forecast to increase on many additional creeks, streams and rivers. The Little Bear near Paradise is the first river that may approach flood stage later this week...and will be monitored for a potential watch over the next 24 hours. && .AVIATION...KSLC...VFR conditions with brief MVFR/IFR conditions this afternoon as convective showers and thunderstorms move through. These will contain gusty and erratic winds along with lightning. These will move out of the area after 03Z with clearing skies and light winds prevailing. .REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions across all of the area aside from northern sites that could see brief MVFR/IFR conditions as convective showers and thunderstorms move through between 20-03Z. These storms will contain gusty and erratic winds along with lightning. Skies will begin to clear after 03Z with winds becoming light and variable. Southern Utah will remain dry with VFR conditions. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...Flood Watch through Friday afternoon for UTZ107. WY...None. && $$ Kruse/Church/Mahan For more information from NOAA`s National Weather Service visit...