Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/19/23

See below for an aviation forecast discussion for the 00Z TAFs.

&& .SHORT TERM...(This Evening through Friday Night) Issued at 331 PM CDT Thu May 18 2023 The main forecast challenges in this period will initially revolve around the sfc smoke that continues to persist this afternoon followed by temperatures tonight into tomorrow. A sfc cold front is currently sweeping southward across our CWA. Wind speeds have been relatively light ahead of this feature today, helping to keep sfc smoke from Canadian wildfires and resultant low visibility persisting. Behind this sfc boundary, an increasing northwest wind is beginning to mix things up so to speak and slowly improving visibility in a few areas. Anticipate these improving conditions will become more noticeable toward late afternoon through this evening. Also, a couple of afternoon showers may develop across our northeast in association with this passing sfc front and and upper trough swinging down across the eastern Dakotas into western Minnesota. The low levels remain pretty dry however, but if any activity materializes it should be fairly short lived. Cold air advection in the lower levels this afternoon and evening will help usher in a much cooler air mass tonight. Chilly temperature readings are expected by daybreak Friday morning. Just how cool we could get may be a bit tricky. All dependent on sky cover and wind speeds going through the overnight hours. A sfc high is progged to build across the western Dakotas overnight and remain centered there. Feel this will give our central and eastern zones enough of a gradient that northwest winds will stay up enough and not allow readings to fall as significantly as if there were very little wind and clear skies. Some of our eastern zones will see increasing cloud cover toward daybreak which would help keep temperatures warmer as well. Farther across our western zones, moreso West River, winds will be lighter, skies potentially more clear. So, anticipate temps will fall in the mid-upper 30s range in some of our northwest zones briefly where some frost could be possible prior to daybreak. Passed on a frost headline at this point because of the uncertainly in wind speeds but this will be a trend we`ll have to monitor going through this evening into the early overnight. Conditions of Friday will be improved in terms of the wildfire smoke. There could be some leftover smoke aloft through the morning hours before that gets swept to the south during the afternoon. A cool air mass remains as the sfc high shifts over our CWA through the day. Highs on Friday could be stuck in the upper 50s to around 60 in our east thanks to more cloud cover while zones from the James Valley and points west see readings in the 60s. .LONG TERM...(Saturday through Thursday) Issued at 331 PM CDT Thu May 18 2023 The long term portion of the forecast begins on Saturday with a surface high pressure drifting south and east of the region with warmer air moving in from the west. While the lower levels of the atmosphere favor a southerly flow, the upper levels suggest the possibility for near surface smoke on Saturday, mainly along and west of the Missouri River. While the latest RAP vertically integrated smoke only goes out to 18Z Saturday, another round of a smoky sky appears likely Saturday afternoon over much of the CWA. The smoke may limit high temperatures on Saturday. Above average temperatures should move into the area early next week as ridging aloft moves into the region. Highs on Monday should reach the low to mid 80s for most locations. The NBM shows a 50 to 60 probability for the Missouri River to reach 90 degrees. The probability is higher on Tuesday, reaching 60 to 80 percent. By mid week, an area of low pressure and a weak upper level trough should track across the region, bringing the potential for showers and thunderstorms. The deterministic ECMWF and Canadian support drier conditions midweek, with the GFS still advertising wetter conditions. The latest rendition of the NBM has reduced the mention of pops on Wednesday, and now favors a better pcpn chance Thursday afternoon into Thursday night. && .AVIATION...(For the 00Z TAFS through 00Z Friday Evening) Issued at 621 PM CDT Thu May 18 2023 Terminals KABR,KATY,KPIR,KMBG The prevailing flight category at KMBG, KPIR and KABR over the next 24 hours is forecast to be VFR. The blustery north- northwesterly winds will draw down within a few hours of sundown. Same thing for KATY over the next 24 hours, except that on Friday between ~13Z and ~21Z, low stratus is forecast to back into KATY from the north-northeast; sticking around until daytime heating/mixing can scatter it out. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Dorn SHORT TERM...Vipond LONG TERM...SD AVIATION...Dorn
Area Forecast Discussion
National Weather Service La Crosse WI
1052 PM CDT Thu May 18 2023 .DISCUSSION...(This evening through Thursday) Issued at 257 PM CDT Thu May 18 2023 Key Messages: - Showers and scattered storms are expected from late this afternoon into tonight. - Smoke will affect visibilities from late this afternoon into Tonight - Patchy frost possible in central Wisconsin Friday Night - After a cool Friday, temperatures will warm into next week Late This Afternoon and Tonight... At 250 PM, radar shows scattered showers and thunderstorms developing along a pre-frontal trough from St. Ansgar, IA northeast to Wabasha, MN. A more widespread band of showers is located from south-central Minnesota northeast toward the western tip of Upper Michigan. Surface-based CAPES have climbed into the 500 to 1000 J/kg range west of the Mississippi River. For the remainder of the afternoon and early evening, these CAPES are forecast to spread east into western Wisconsin. The NAM CAM is a bit too robust with its CAPES (climbing into the 1500-2000 J/kg range). This is due to its surfaces dew points climbing into the lower and mid-60s. Meanwhile, the HRRR has better dew points, but its surface temperatures look to be too warm, so its CAPES of 1000 to 1500 J/kg also look to be a bit too high. Much of the shear is located in the 0-3 km (up to 30 knots) layer along and behind the surface front. As a result, not anticipating any widespread severe weather. However, could not rule out an isolated strong storm. The main threats would be lightning and wind gusts up to 35 mph. Subsidence in the wake of this front will bring the smoke from aloft to the surface. This smoke is reducing visibilities into the 1 to 3 mile range in South Dakota and in western Minnesota. The RAP is showing that this smoke will reduce visibilities in our area into the 3 to 5 mile range. This is likely not low enough so went with visibilities around 2 miles based on the visibilities upstream. Due to this smoke, Air Quality Alerts have been issued by the Minnesota Pollution Control Agency and the Wisconsin DNR. The particulates from this smoke will be unhealthy for sensitive groups such as those with cardiovascular and lung disease. Friday Night... With clearing skies and decreasing winds on Friday night, low temperatures will range from the mid-30s to mid-40s. The coldest temperatures will be in central Wisconsin where they will be cold enough that there could be some scattered frost in the typical cold areas. This Weekend into Early Next Week... High pressure will gradually build across the area on Friday. This high pressure system will produce dry weather into early next week. As this high pressure moves east of the area, temperatures will gradually warm. High temperatures will be around 70 on Saturday and then gradually warm to around 80 by Tuesday. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1050 PM CDT Thu May 18 2023 A band of showers was progressing through northeast Iowa into western Wisconsin this evening in conjunction with a cold front. Behind this front, smoke from Canadian wildfires was reducing visibilities to MVFR and these conditions should remain until a secondary front sweeps south late tonight between 05 and 09Z. Light WNW winds of 5-10 kts this evening behind the initial front will increase from the NW behind the second front to 10-15kts with gusts over 20-25 kt through the daytime hours tomorrow. MVFR to low VFR ceilings are expected to develop by mid to late morning and linger through the rest of tomorrow afternoon. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ DISCUSSION...Boyne AVIATION...Skow
Area Forecast Discussion
National Weather Service Boise ID
824 PM MDT Thu May 18 2023 .DISCUSSION...Smoke layers aloft from wildfires in the Western Canada will remain in place through at least Saturday. Smoke could mix down to the surface tonight across Southwest Idaho and expand westward Friday afternoon. Latest RAP guidance remains unchanged with keeping near surface smoke trapped in the lower valleys as the upper level ridge moves over the forecast area. In addition to the reduce in visibility, the smoke could keep high temperatures a few degrees cooler than previously forecast. NBM and HREF probabilities still favor temperatures in the valley reaching 90 F or above both Saturday and Sunday (70% chance). This is about 15% lower probabilities in the latest run possibly signally the smoke could be an issue. Thunderstorms could return as early as Saturday evening in Southeast Oregon with a potential for stronger storms on Sunday as the upper level trough moves in. Models have remain consistent with a deep moisture plume (in 95% percentile) from the Gulf of Mexico along with substantial destabilization and increased shear with the approaching trough on Sunday. This could support organized thunderstorms across much of the area. Updated forecast for increased smoke/hazy conditions in Southwest Idaho overnight. Update will be out shortly. && .AVIATION...Mainly VFR. Areas of wildfire smoke from Canada will continue to degrade visibility aloft. Isolated evening showers and thunderstorms in Harney County, OR and the Central ID Mountains tomorrow. MVFR conditions, gusty winds to 30 kt, and small hail are possible with stronger storms. Surface winds outside of storms: variable 10 kt or less. Winds aloft at 10k feet MSL: variable 5-10 kt. Weekend Outlook...Isolated afternoon-evening showers and thunderstorms this weekend, mainly in SE OR and central ID. A higher chance of widespread thunderstorms expected Sunday, with some severe storms expected mainly in SE OR. MVFR conditions, gusty winds and hail are possible with stronger storms. Outside of storms, expect VFR conditions and light winds. Areas of smoke. && .PREV DISCUSSION... SHORT TERM...Tonight through Saturday night... Near-record warm temperatures, thunderstorm chances, and smoke/haze from Canadian fires are the primary forecast concerns through Saturday night. *HEAT: The well-advertised warm up remains on track across the entire forecast area amidst an anomalously strong upper-ridge. The position of this feature will remain nearly fixed into this weekend. Forecast trends suggest temperatures will likely peak on Saturday across the entire area, with upper 80s through low 90s expected through most of the Snake Valley and other lower elevation locations. Latest probabilities for exceeding 90 degrees on Saturday are 83% for Boise, 24% for Twin Falls, and 16% for Baker City, OR. There is the possibility that lofted smoke/haze could reduce heating by a couple degrees, but current forecasts suggest the plume will primarily remain situated to the north and east on Saturday. *THUNDERSTORMS: Substantial destabilization (CAPE values near 1000 J/kg) has occurred across eastern Oregon and far western Idaho amidst ample daytime heating. The 12Z BOI sounding this morning showed a near-record PW value of 0.86". Despite the favorable thermodynamic environment, the proximity of the upper ridge to the west over Oregon should keep convection somewhat suppressed today through Saturday over Valley locations. One exception today will be across the Boise/Sawtooth Mountains, Owyhee Mountains, and east-central Oregon, where thunderstorm chances are roughly 15-25% this afternoon and evening. Less activity is expected on Friday (less than a 15% chance), but a gradual increase in moisture on Saturday should lead to an uptick in thunderstorm chances in eastern Oregon (20-40%) and over the Boise Mountains (15-20%). Locally gusty winds to 40 mph and brief heavy rain are likely to accompany the strongest thunderstorms. *SMOKE/HAZE: A substantial plume of primarily lofted smoke continues to meander erratically over the Pacific Northwest. The most significant surface visibility reductions today have been near Baker City, OR. Additional areas of visibility reductions are possible (30-40% chance) overnight into the west-central Mountains and Magic Valleys. Both the RAP-based smoke output and NASA biomass output indicate smoke will spread westward across the Snake Valley Friday morning. LONG TERM...Sunday through Thursday...Southwest flow will develop aloft over the Pacific Northwest as an upper trough approaches on Sunday. With forecast precipitable water values reaching over the 90th percentile on Sunday, combined with increased lift ahead of the trough, showers and thunderstorms are expected to generate during the afternoon and evening. The best chance (35-50%) for enhanced instability and wind shear for stronger thunderstorms in the afternoon will be over central and eastern Oregon. However, thunderstorms over the mountains of southwest Idaho also become more likely (30-45% chance) by the evening as the trough tracks eastward. Storms that develop will be capable of heavy rains, hail, and gusty outflow winds. GFS guidance is currently the most bullish with the amount of precipitation that will impact the area, whereas other guidance members are more conservative and limiting. Thereafter, a cold front is forecast to move through the area on Monday, creating increase wind speeds for the Snake Plain. Temperatures will also cool to around 5 to 10 degrees above normal, which is roughly 10 degrees cooler than the forecast high temps on Sunday. Ensemble guidance agrees that the region will continue to be influenced by the trough passing through the NW U.S. on Tuesday and Wednesday, and therefore the threat of thunderstorms will remain a possibility each afternoon. Currently, the best location for storms will be closer to the NV border and over central Idaho, with a 20-30% chance of occurrence. Lastly, forecast smoke models are predicting that areas of Canadian wildfire smoke will waft in and out of Oregon and Idaho next week, so hazy skies may continue to be in our future. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && $$ DISCUSSION...JDS AVIATION.....SA PREV SHORT TERM...JR PREV LONG TERM....SH
Area Forecast Discussion
National Weather Service Cheyenne WY
949 PM MDT Thu May 18 2023 .SHORT TERM...(This evening through Friday night) Issued at 302 PM MDT Thu May 18 2023 A very active weather pattern will be coming to a close for the short-term forecast package. Heavy rainfall from thundershowers, severe weather, and gusty winds should come to a close here this afternoon. Light to moderate rain showers behind the main cluster of convection is anticipated to linger along and behind the cold frontal passage today and tonight, in conjunction with upslope flow along the higher terrain. The more important concern remains with the visibility and air quality reductions from wildfire smoke. The source region from the wildfire smoke is from Alberta, Canada. Once the northerly winds behind the slow-moving cold front pushed through, significant visibility reductions remain present. Several sites across our cwa have reported observations between 1/2 mile and 2 miles. Went ahead with an Air Quality Alert for the NE Panhandle, and an SPS for southeast WY through 11am FRI. We have also recorded observations with rainfall being present while smoke was still in the vicinity of our automated reporting stations. Overnight, we should see gradual clearing of the cloud cover from north to south. The mostly cloudy conditions are expected to persist through daybreak Friday for areas along and south of Interstate 80. However, the wildfire smoke may linger not only into Friday morning, but the majority of the day. Hi-res models have struggled to handle the near-surface smoke aspect via the HRRR due to the wildfire source point being too far north outside of the domain. Have gone with a combination of the RAP and international models to assess how long, and the concentration levels for smoke to be included in the short term forecast. Will have to re-assess on the next forecast package if smoke needs to be included into the forecast through potentially early Saturday. Daytime highs should begin to moderate back into the 60s for Friday, with slightly cooler temperatures in the higher terrain. A few locations may creep into the lower 70s if the smoke does begin to wane in concentrations near the surface. High pressure will take hold by Friday night as overnight lows creep down into the upper 30s to middle 40s. We will begin to see a dry pattern take hold for the beginning of the weekend as warmer temperatures begin to make a return to the area. .LONG TERM...(Saturday through Thursday) Issued at 302 PM MDT Thu May 18 2023 The only concern with the portion of the forecast is the potential for convection at the beginning of the week continuing through mid week. It is looking look like a mild and fairly dry weekend across the forecast area as the upper level ridge keeps its grip over the region. The models are hinting at a weak shortwave moving through the Nebraska panhandle on Saturday night into Sunday, but it appears like the moisture will be quite limited for any convective development. Next week, the models/ensembles are showing the precipitable water values increasing through the week. At this point, it appears like the better moisture return will take place over Wyoming on Monday and Tuesday with this moisture spreading further east into the Nebraska panhandle on Wednesday and Thursday. The models are also showing the shear increasing over the area especially around mid week in response to the closed low moving into northern Montana. Overall, the trends are pointing to a chance of scattered afternoon thunderstorms through much of the week especially over Wyoming with lesser coverage over the Nebraska panhandle. Temperatures will also be on the mild side with highs in the 70s and lows in the upper 40s to mid 50s. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 948 PM MDT Thu May 18 2023 Wyoming TAFS...Northerly flow at the surface and aloft will help bring in smoke from fires, reducing visibilities to 2 to 6 miles at Laramie and Cheyenne, and 4 miles at Rawlins until 08Z. Clouds will generally remain scattered to broken between 5000 and 8000 feet AGL, although Laramie and Cheyenne will see broken clouds at 2500 feet AGL until 15Z. Nebraska TAFS...Northerly flow at the surface and aloft will help bring in smoke from fires, reducing visibilities to 1 to 4 miles at times. Broken clouds from 3000 to 5000 feet AGL will prevail through early morning, with broken clouds below 1000 feet AGL at Sidney from 09Z to 14Z. Skies will become mostly clear after 14Z Friday. && .FIRE WEATHER... Issued at 302 PM MDT Thu May 18 2023 Fire weather concerns will remain low for the short-term forecast as a cold front and recent precipitation keep fuels and humidity values away from critical thresholds. Light winds will also be present for the short term forecast. Rain showers and isolated thunderstorms are possible this evening into Friday morning, with the potential for a few gusty and erratic winds to 30-40mph. && .HYDROLOGY... Issued at 302 PM MDT Thu May 18 2023 Latest radar loop was showing the showers and thunderstorms mainly tracking across the I-80 corridor this afternoon which is fortunately north of the Snowy and Sierra Madre ranges. Therefore, we will most likely not see too much in the way of rapid rises on the mountains streams and rivers this afternoon. However, we will continue to see some snowmelt during the next couple of days. Fortunately, temperatures will be on the cool side tonight and Friday which will slow down the melting process a bit. The snowmelt process will pickup again this weekend and early next week which may aid in pushing the upper North Platte River close to flood stage at Saratoga. At this point, it still looks likely that Saratoga which will reach minor flood stage on Sunday. Still a little uncertain on whether Encampment and Sinclair will reach minor flood stage, but would not be surprised that they could creep to minor flood stage early next week. Meanwhile, the Little Snake River basin will continue to have steady flow which will result in more minor to moderate flooding near Baggs and Savery. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...BW LONG TERM...REC AVIATION...RUBIN FIRE WEATHER...BW HYDROLOGY...REC
Area Forecast Discussion
National Weather Service Duluth MN
641 PM CDT Thu May 18 2023 .DISCUSSION...(This evening through Wednesday) Issued at 241 PM CDT Thu May 18 2023 Key messages: * Air Quality Alerts continue into Friday due to near surface smoke from Canadian wildfires. * Numerous rain showers with a few thunderstorms this afternoon and tonight before a dry weekend for the Northland. * Patchy frost is possible for the Iron Range Saturday morning. * Warming up for most areas next week. Per the MN Pollution Control Agency, and the WI DNR, an Air Quality Alert remains in effect for northeast Minnesota until 600 am Friday, and until noon Friday for northwest Wisconsin. Near surface smoke behind a cold front will spread across the area this afternoon and into tonight. Visibilities of 1 to 3 miles in smoke have been observed upstream. Per the RAP Smoke forecast, near surface smoke will decrease from west to east tonight into Friday morning as low level air trajectories become less favorable with the passage of the upper level low. For this afternoon, an area of rain showers with embedded thunderstorms will move across northwest Wisconsin ahead of a cold front. While Price county is in a Marginal Risk for severe storms, the overall threat is very low given very modest buoyancy. Additional scattered rain shower and thunderstorm activity will spread across northeast Minnesota late this afternoon, and more so into this evening and tonight as the cold core aloft associated with the upper level low propagates east-southeast. After a brief lull across northwest Wisconsin, this next round of rain showers and a few thunderstorms will spread across the region this evening and tonight. Severe weather is not expected. Precipitation activity will diminish from west to east Friday morning and into the early afternoon as the low propagates into the central Great Lakes region. With light winds and clear skies in surface high pressure, we will be on the lookout for frost Friday night into Saturday morning. However, the 12 UTC guidance suggests the coldest portion of the airmass to be exiting the region through the afternoon and evening. At this time, the Iron Range has the best potential for patchy frost Saturday morning. Looking ahead to next week, surface high pressure across the eastern US will support a warming trend with high temperatures solidly into the 70s, and potentially in the 80s, with southerly surface flow. Of course, the caveat will be lake breezes for especially the North Shore and Twin Ports. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 637 PM CDT Thu May 18 2023 A cold front is passing through the Northland this evening. Winds will shift from southwest to northwest at remaining terminals in northwest Wisconsin. The Arrowhead will experience a few thunderstorms as well over the next few hours. Off and on shower chances continue through tonight and may require future amendments to lengthen the shower and or rain chances at some terminals. MVFR cigs should then clear towards the late morning to afternoon hours tomorrow. && .MARINE... Issued at 325 PM CDT Thu May 18 2023 Southwest winds around 5kts this afternoon will increase to west at 10-15 kts late tonight across western Lake Superior. A localized area of northwest winds with gusts to near 25 kts will develop late tonight into Friday morning between Silver Bay and Grand Marais, and a Small Craft Advisory has been issued. Patchy fog and areas of smoke will reduce visibilities on the lake tonight. Scattered rain showers and a few thunderstorms are also expected. Winds will turn northwest at 10-15kts on Friday. For this weekend, conditions hazardous to small craft are forecast in strong southwest winds on Saturday, and strong northeast winds on Sunday. && .PRELIMINARY POINT TEMPS/POPS... DLH 42 58 41 70 / 60 10 0 0 INL 39 66 38 73 / 60 0 0 0 BRD 41 60 38 72 / 20 0 0 0 HYR 42 58 37 73 / 50 20 0 0 ASX 44 55 40 71 / 70 30 0 0 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. LS...Small Craft Advisory from 4 AM to 10 AM CDT Friday for LSZ141- 142. && $$ DISCUSSION...PA AVIATION...NLY MARINE...PA
Area Forecast Discussion
National Weather Service Des Moines IA
619 PM CDT Thu May 18 2023 ...Updated for the 00z Aviation Discussion... .DISCUSSION.../Tonight through Thursday/ Issued at 321 PM CDT Thu May 18 2023 Key Messages: - Scattered showers and thunderstorms through the overnight. The overall severe weather threat is low. - Areas of smoke passing through this evening may reduce surface visibilities at times. - Pleasant weekend ahead. Cold front is situated across central Iowa from near Mason City to Webster City to Carroll this afternoon. Weak instability has developed in vicinity of the boundary with MLCAPEs below 1000 J/kg and weak shear/flow aloft will limit any strong storm potential. The hail threat is minimized by the lack of instability and where there is an, narrow CAPE profiles. The non-supercell tornado parameter is non zero but LCL heights are quite high and the potential for vorticity stretching is no great again with lower 0-3 km CAPE values generally 50 J/kg or less. The showers and storms will bubble along the boundary for much of the night with cell movements nearly parallel to the boundary. Still that will not pose a heavy rain threat. Smoke is the other issue in the near term. Subsidence behind the cold front has allowed the smoke from the Canadian wildfires to make it to the ground into northwest Iowa with visibilities dropping to 2 miles or less. Some of these visibilities have improved this afternoon with mixing. For the forecast, followed the RAP near surface smoke solution for visibility restrictions. The near surface smoke will diminish overnight as the wind becomes more northerly. The upper level smoke however will have another wave pass across the state on Friday. Friday will be cooler then a very pleasant weekend is on tap with high pressure moving into the region. That high pressure system will have a big influence on the Iowa weather into mid next week. Temperatures will gradually rise into the 80s next week as Iowa is in the return flow though dew points will remain on the dry side as the source region of the air flow will be originating from the high pressure system. The next chance of precipitation as of now is around late Wednesday. && .AVIATION.../For the 00Z TAFS through 00Z Friday evening/ Issued at 619 PM CDT Thu May 18 2023 A narrow line of showers and thunderstorms will move across the area tonight, and may briefly impact ALO/DSM/OTM at times. Highest probability is at ALO where a TEMPO has been included, whereas the other two terminals are covered with VC groups due to lower confidence. Amendments are possible. Also, a broad swath of smoke/haze is advecting across the area and will produce multiple hours of MVFR visibility overnight, and possibly IFR at times mainly in the north, before easing early Friday morning. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION...Donavon AVIATION...Lee
Area Forecast Discussion
National Weather Service Quad Cities IA IL
646 PM CDT Thu May 18 2023 ...AVIATION UPDATE... .SYNOPSIS... Issued at 239 PM CDT Thu May 18 2023 A surface low is near the western tip of Lake Superior this afternoon with a cold front extending southwestward into northwest Iowa to near KOMA. Visibility restrictions due to smoke are occurring behind this front. A second cold front extends from near International Falls southwestward into South Dakota then westward to southeast Montana. Satellite shows a developing cumulus field ahead of the first front with radar showing convective development across southeast Minnesota. Locally, at 3 PM temperatures ranged from 74 degrees at Freeport and Sterling to 81 degrees at Washington Iowa. Dewpoints are in 50s across the area. Surface based CAPE across Iowa 250 to 500 J/KG across Iowa with 0 to 6 km shear was around 25 knots. && .SHORT TERM...(This evening through Friday) Issued at 239 PM CDT Thu May 18 2023 Key Messages: 1. There is a low risk for severe thunderstorms this evening from 4 to 8 PM north of Highway 20 in Buchanan, Delaware, and Dubuque Counties. 2. There is a chance for wildfire smoke to make it to the surface behind a cold front Friday morning. This will have to be monitored for impacts to air quality and visibility. Discussion: The main forecast concerns were timing of precipitation and smoke reaching the surface behind a cold front on Friday morning. A positively tilted 500 MB trough is forecast to move southeastward into northeast Minnesota and western Lake Superior tonight then into Michigan by 00 UTC on Saturday. At the surface, a surface low is forecast to follow a similar track with a prefrontal trough and cold front moving across eastern Iowa, northwest Illinois, and far northeast Missouri. There is a narrow axis of moisture and instability developing along the prefrontal trough late this afternoon and into this evening this evening and overnight. 500 to 1000 J/kg of CAPE are forecast across the area late this afternoon into this evening with 20 to 30 knots of 0 to 6 km shear. Scattered showers and isolated thunderstorms are possible this evening An isolated severe storm is possible late this afternoon into the early evening but confidence is low in this occurring. The better shear moves into the area after 03 UTC. CAMS have showers and storms moving into the area after 03 UTC when instability is decreasing. Rainfall amounts will be light with 0.20 to 0.40 inches possible especially north of Highway 30. Low temperatures on Friday will range from the mid 50s along Highway 20 to the lower 60s south of a Fairfield to Burlington to Galesburg line. Precipitation will quickly exit the area after 12 UTC on Friday. the RAP continues to show the potential for smoke aloft to mix to the surface along and behind the cold front in a short 3 hour window as gusty northwest winds behind front mix to the surface. Clouds and smoke aloft will be slow to clear on Friday behind the front. High temperatures on Friday will range from the mid 60s along the Highway 20 corridor to the lower 70s in far southeast Iowa, west central Illinois, and far northeast Missouri. .LONG TERM...(Friday night through Thursday) Issued at 239 PM CDT Thu May 18 2023 Key messages: 1) Well above normal temperatures for much of the extended period. 2) Small chance for rain late next week. Details: Global models indicate a blocking ridge of high pressure developing from the Plains to the Ohio Valley and to New England. The polar jet will be well up into Canada, with an upper low in the PacNW. This means much of the extended will have very warm temperatures with no significant rainfall. Temperatures will be into the 80s with the potential for 90+ later next week. However, as of now this doesn`t appear to be record breaking heat. ECMWF has H8 temps in the 16 to 18C range which would support well above normal readings. Toward the end of next week we`ll see moisture increase on the backside of the high and stronger mid level flow encroach from the northwest, which should bring with it some rain chances. However, chances look to be small and possibly could remain off to our west. Haase && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 645 PM CDT Thu May 18 2023 VFR cigs are expected through the period as MVFR vsbys due to shra and smoke are expected overnight and into the morning. A cold front will sweep through the area and mix down smoke from a loft. Currently have MVFR vsbys, but cams upstream have LIFR vsbys. Some mixing out is expected, but could see some brief IFR vsbys from the smoke. Otherwise, expect improving vsbys later in the period. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ SYNOPSIS...Cousins SHORT TERM...Cousins LONG TERM...Haase AVIATION...Gibbs
National Weather Service Kansas City/Pleasant Hill MO
636 PM CDT Thu May 18 2023 ...Updated 00z Aviation... .Discussion... Issued at 301 PM CDT THU MAY 18 2023 Key messages: - Thunderstorms will be possible tonight and into Friday morning...severe weather is not expected. Discussion: Low pressure system moving into the upper Great Lakes region will push a sagging front through the region. This front is currently situated across western Kansas up into central Wisconsin. Along the front, scattered showers have started to develop with some embedded thunderstorms. Anticipate showers and thunderstorms to continue to develop and expand in coverage ahead of sunset due to the favorable instability and upper level forcing. Through the overnight and into tomorrow morning, showers will continue to spread across the area as the front continues to sag. Severe weather is not expected due to limited forcing and instability overnight and into the morning along the front. One caveat is a secondary shortwave ejected across the four corners which will ride along the sagging front. This could bring a better chance for some heavy downpours across the southern half of the CWA tomorrow morning. OVerall not expecting any flooding concerns for with this event. Northern high pressure will quickly move into the region behind the front later in the day tomorrow and bring in cooler weather thanks to CAA. One thing to watch is the smoke across the Northern Plains and its trajectory. RAP smoke guidance does have the potential for some thick smoke moving in north of US-36 by tomorrow morning behind the front thanks to due north winds. We can see this happening already across Nebraska where vsbys are down below 5sm. Will have to keep an eye on the smoke and its potential impacts across the region over the next 12-24 hours. Otherwise cooler temperatures and very pleasant weekend is on tap for the region. By next week, upper level ridge and associated high pressure will build across the eastern half of the CONUS keeping the area in southwest flow. Temperatures will increase each day with dry weather for much of next week. && .Aviation...(For the 00Z TAFS through 00Z Friday Evening) Issued at 632 PM CDT THU MAY 18 2023 A cold front will be moving across eastern Kansas and western Missouri overnight. There are two things to watch with this. The first, is smoke associated with the Canadian Wildfires. This afternoon over Nebraska, several sites dropped below 2 mile visibility. However, since 22z this afternoon, conditions have been improving. Expecting mixing to weaken this evening, thus will keep visibility VFR with respect to smoke issues. The second factor to watch will be shower and storm development along the front. Expecting precipitation to start around 09-10z in the KC metro. Thunderstorm coverage will be isolated along the front, therefore will place VCTS for a couple of hours in the TAF and will monitor lightning trends overnight for the 06z TAF issuance. Winds shift north-northwest after the cold front passes. && .EAX WATCHES/WARNINGS/ADVISORIES... KS...NONE. MO...NONE. && $$ Discussion...Sipprell Aviation...Krull
Area Forecast Discussion...UPDATED
National Weather Service Glasgow MT
711 PM MDT Thu May 18 2023 .DISCUSSION... Evening update: As visibility observations now show 10SM or better across all of NE Montana, felt it was best to update the forecast for now through the next 24 hours to better represent the location and movement of smoke from Canadian wildfires. Currently, the smoke seems to have retreated to along the Rocky Mountain front range of central and western Montana. Operational HRRR / RAP smoke models show this area of smoke slowly moving east through the night tonight. I adjusted the weather grids to show this gradual movement. By this time tomorrow, a brief rain shower or two is showing up in a few convection-allowing models, skirting along the southern Saskatchewan / northern Montana border. Probably will not amount to much. -----BMickelson Previous discussion: Smoke was not as bad today as yesterday and it looks to stay that way according to the RAP Smoke products. However, a surface high will drift over the area tonight, allowing for radiational cooling and that could trap smoke close to ground level. Smoke should mix out Friday as the surface high moves to our east and southerly winds bring in cleaner air. Look for a cool night tonight as clear skies and light winds will allow temps to drop into the 30s to low 40s. There is a 5-20% chance that a location in the eastern zones reaches 32F. On Friday, southerly winds and an upper ridge will start a warming trend. Look for temps to reach the upper 60s and 70s. Saturday`s highs look to be mainly in the 80s. Some instability over Alberta could fire up some showers Friday evening that should die before reaching NE MT Saturday. Another impulse looks to fire off thunderstorms over central Montana late Monday that could bring gusty winds as they move into the western zones. Hail doesn`t look likely at this point as the airmass looks a bit dry (dewpoints mainly in the 40s). An upper trough over the Pacific NW associated with the instability Monday looks to remain in place into the middle of next week, keeping the chance of showers around through Wednesday. TFJ && .AVIATION... VFR, possibly MVFR Friday 09-16z. Even though smoke seems to have dissipated across the NE MT region, some smoke models are showing it returning to the area from west to east through the overnight hours. A nighttime inversion could help keep current smoke from clearing away from some locations. Otherwise, skies will be clear tonight with light winds. Look for South winds at 5-15 kts at all TAF sites by Friday afternoon. TFJ/BMickelson && .GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE. && $$
Area Forecast Discussion
National Weather Service Green Bay WI
1044 PM CDT Thu May 18 2023 Updated aviation portion for 06Z TAF issuance .SHORT TERM...Tonight and Friday Issued at 345 PM CDT Thu May 18 2023 There are numerous forecast issues, including thunderstorm/severe potential for late this afternoon/early evening, precipitation trends, air quality/smoke concerns, and cooler temperatures for Friday. Thunderstorm/severe potential...instability has been slow to develop this afternoon, but local mesoanalysis page showed SBCAPE building to 400-800 j/kg in SE MN/NE IA. Satellite and radar showed new convection developing in SE MN, along the approaching cold front. Expect instability to increase in central WI as the front approaches late this afternoon, so thunderstorms appear most likely there. Cannot rule out an isolated severe storm or two in central WI, as deep layer shear of 35 to 40 knots and low wet-bulb zero heights (8-9k feet) favors hail, and inverted-v soundings and 40-50 kt winds in the mid- levels support strong gusts. The overall lack of instability will be a limiting factor. The severe threat should occur in a small time window, mainly 5 pm to 9 pm. Precipitation trends...showers and embedded storms will arrive in north central WI with the cold front between 4 pm and 5 pm, then spread southeast to the lakeshore by around midnight. Expect the thunderstorm threat to wane before the precipitation makes it into NE/EC WI, as instability weakens. As the main frontal precipitation exits eastern WI overnight, additional showers will move into north central WI as the upper level low arrives. Scattered showers will persist across mainly NC/NE WI into Friday. Have lowered QPF amounts a bit for late this afternoon and tonight, given recent trends. Air Quality/Smoke concerns...Wisconsin DNR issued Air Quality Advisories for all of WI earlier today, and these continue through midday Friday over the northwest two-thirds of the CWA, and until midnight Friday night for the Fox Valley/lakeshore areas. RAP near-surface smoke forecasts show smoke mixing to the surface in the wake of the cold frontal passage tonight, and lingering into the day on Friday. The latest forecasts show this occurring in NC/C WI later this evening, and during the overnight hours in the east, with some clearing occurring from west to east on Friday. Added patchy smoke in the forecast, and stayed close to the RAP timing trends. It remains to be seen if vsbys will be greatly reduced anywhere in the forecast area, but models seem to suggest that the smoke will disperse some as it shifts east. Cooler Temperatures on Friday...H8 temperatures are expected to drop to near zero C on Friday as the upper low moves through the region. Lowered high temperatures considerably, with readings in the upper 40s and 50s expected over most of the region. .LONG TERM...Friday Night Through Thursday Issued at 345 PM CDT Thu May 18 2023 A less active pattern will set up for this forecast period and bring dry and warmer weather to the region. Afternoon high temperatures will be above normal throughout the extended with values in the low to middle 70s for the weekend and Monday, then increase to the upper 70s to low 80s for midweek next week. Friday night through Saturday...Moisture wrapping around a departing upper-level low over northern Lake Michigan will keep a few showers across far northeast WI from Friday night into Saturday morning. Meanwhile, high pressure will be moving into the state from the west. The combination of the departing low and the incoming high will cause clouds and an elevated smoke layer to also decrease and exit. The remainder of Saturday will be dry and mostly sunny. Rest of the extended...Dry and mostly sunny conditions are also anticipated for Sunday. However, models indicate a possible backdoor cold front dropping south across the region sometime Sunday afternoon/evening. If anything, this would cause temperatures to decrease quickly behind the front. Models have also continued to lower the potential for precip development due to the amount of dry air already in place. Temperatures will rebound on Monday and Tuesday as low-level winds switch to the southwest and lift warmer air into the region. Models then show signs of the next chance for some precip sometime midweek or towards the end of the week. && .AVIATION...for 06Z TAF Issuance Issued at 1039 PM CDT Thu May 18 2023 Showers and a few thunderstorms will end overnight as a cold front moves across the region. IFR conditions are likely late tonight and early Friday west of a IMT to CWA line, with MVFR conditions to the east. Conditions should improve to VFR by Friday afternoon east of a IMT to STE line and be MVFR to the west. Scattered showers are possible in the north Friday. The layer of smoke that was far above the ground the last several days may mix down to the ground late tonight and Friday, and produce visibilities of 3 to 5 miles. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM.....Kieckbusch LONG TERM......Kruk AVIATION.......RDM
Area Forecast Discussion
National Weather Service Grand Rapids MI
1045 PM EDT Thu May 18 2023 LATEST UPDATE... Update .UPDATE... Issued at 1044 PM EDT Thu May 18 2023 Cold front located upstream this evening will make steady progress tonight moving out of Minnesota and Wisconsin and approach Lake Michigan towards 12Z. The front will then push through the forecast area on Friday. For tonight though, the bulk of the area will remain dry, the exception being the northwest CWA up towards Ludington. The precipitation upstream at the present time though is not impressive in coverage or intensity. The HREF both the 12Z run and the 00Z run trickling show some light precipitation moving into West Central Lower Michigan near and after 09Z. Again, precipitation amounts are not expected to be heavy from this entire frontal passage and only a few hundredths are likely by 12Z. && .DISCUSSION...(This evening through next Thursday) Issued at 147 PM EDT Thu May 18 2023 - Showers Friday The mid level low is still shown to track eastward through MI Friday. Favorable moisture depth and lift are shown to support showers as it tracks through the state Friday. Although trends are for a slightly weaker system with a dip in the qpf shown. Ensemble forecasts of qpf still show most members in the various models with measurable qpf and we will continue to feature relatively high POPs. There is a small risk for thunderstorms and the region is still in a general thunder risk from SPC`s site. The HRRR looked to be the most aggressive with the thunder potential showing 500 to 1000 J/kg of CAPE in the afternoon along the frontal zone. The other models show less CAPE but enough for an isolated storm or two. If we do develop some better instability, given the 500 mb jet streak over the state Friday afternoon, the storms could take on some organization with gusty winds the main risk. - Warming up early next week but will it last Most models still show a significant warm up next week, although the 12z GFS brings down a cold front from the north by Thursday. This model then keeps the temperatures much lower than the other models. It looks like an outlier and this model also shows considerable spread in the ensemble forecasts with the high temperatures for the end of next week. The CMC and ECMWF ensemble mean max temperatures are at or above 80 degrees for the end of the week at Grand Rapids. These two models are either holding steady with the warmth or trending higher. - Looking dry next week The axis of moisture along with the location of the low level jet are shown to be well west of the CWA. This will act to focus the convective development away from MI. Bufkit overviews for Grand Rapids show next week featuring an unsaturated DGZ and mainly subsidence. As a result we will feature dry conditions. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 811 PM EDT Thu May 18 2023 VFR conditions are in place area wide this evening and that will remain the case through the night. An upstream cold front stretching from portions of Western Wisconsin southwest into Iowa will bring lower ceilings and rain into the area on Friday. Tonight though, ceilings will remain VFR and we will be dry at the TAF sites. Ceilings will lower to around 5,000ft at MKG at 12Z with higher cloud bases at the other TAF sites. By 18Z however widespread MVFR ceilings will overspread the area. A band of rain showers and possibly an isolated thunderstorm will move through between 11Z and 00Z on Friday. The lower ceilings will begin to lift out quickly in the afternoon as the front progresses to the southeast. Winds will veer from southeast tonight to south by morning and then southwest and west on Friday. Winds 5 to 15 knots will increase to 10 to 20 knots on Friday. && .MARINE... Issued at 147 PM EDT Thu May 18 2023 It looks like it will get close to small craft conditions tonight up around Little and Big Sable Points. However given the stable conditions over the cooler waters of Lake Michigan, we will hold off on a small craft advisory. Bufkit Overviews for wind and mixing height suggest that we may struggle to reach criteria as well. For now we will feature winds topping out at 20 knots for those locations. Another shot for small craft conditions exists later Friday night into Saturday morning. The mixing height deepens up with cold air advection and the winds at those levels are progged to be near or above criteria. In addition, waves of 3 to 4 feet are progged south of Grand Haven. Thus we will need to monitor trends closely. && .FIRE WEATHER... Issued at 147 PM EDT Thu May 18 2023 The southeast flow continues with temperatures rising now into the mid to upper 60s. Relative humidity values continue to fall with values currently showing 25 to 35 percent at most locations. With surface temperatures likely to go up a few more degrees, the humidity levels will fall off as well. Wind gusts were mostly in the 10 to 20 knot range. Based on all this we will maintain the Red Flag Warning for northern zones into the early evening hours. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...None. && $$ UPDATE...Duke DISCUSSION...MJS AVIATION...Duke FIRE WEATHER...MJS MARINE...MJS
Area Forecast Discussion
National Weather Service Wichita KS
711 PM CDT Thu May 18 2023 .SHORT TERM...(This evening through Sunday night) Issued at 201 PM CDT Thu May 18 2023 A mid/upper trough over Manitoba was digging southeast into the Northern Plains/Upper Mississippi Valley area this afternoon. A cold front extended from this system south and southwestward from the arrowhead of Minnesota to the Central High Plains. Widespread smoke was evident on GOES imagery in the post-frontal airmass stretching across all of the Northern Plains and moving southward into the Central Plains this afternoon. The smoke was reducing visibilities across southern Nebraska and northwest KS to MVFR with visibilities in the 1-3 mile range (lower at times in some areas). This smoke may gradually build southward in the wake of the front as we move through the day on Friday but rainfall over southern KS leads to low confidence in the exact impacts which are not being handled well from the HRRR since it`s domain does not extend into Canada where the origin of the smoke is. the front sinks southward late this afternoon and evening we are expecting showers and storms to develop as the airmass remains weakly capped. Much of this activity may be diurnally driven and tend to fade away as we move through the evening hours impacting portions of central and northern KS. Organized strong/severe storms continue to appear unlikely given weak deep layer shear and mid-level lapse rates. We expect to see a break until late tonight or into the early morning hours on Friday when low level moisture transport ramps up with storms focusing across northern Oklahoma and perhaps into far southern KS during the morning hours on Friday. There still appears to be better support for heavy rain just south of the forecast area but some of this activity could spill into far southern KS given a very moist column with PWATS progged in the 1.5 inch range for above the 90th percentile for mid May and relatively slow storm motions anticipated. Sat-Sun...a stable post-frontal regime is anticipated as we move through the weekend. Seasonably cool temperatures on Sat will rise to near normal on Sunday. We may see some shallow radiational fog develop each morning, especially where the soil remains moist or across southern Kansas. With high pressure overhead, light winds and mostly clear conditions are expected to prevail. .LONG TERM...(Monday through Thursday) Issued at 201 PM CDT Thu May 18 2023 Seasonal and dry conditions should persist over the region for much of the period. There remains a small chance of precipitation Tuesday and Wednesday thanks to uncertainty among model outlooks for upper- level flow. Look for this to change with future model runs, but for the time being, this weak and uncertain flow aloft does not appear to be overly convincing for significant pops. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 657 PM CDT Thu May 18 2023 Main aviation concerns will be shower and storm chances, along with some smoke reducing visibility. Currently have a series of upper waves moving out of the Rockies and into the Plains. In addition, a cold front extends from north of KDDC, through northern KS and into southeast Nebraska. Numerous storms are currently over eastern CO with some additional sct activity over west/central KS. While we may see some decrease in coverage after sunset, feel there will be enough 850mb moisture transport to keep some activity going overnight. Locations generally west of I-135 will have the best chance to see something before 06z with KICT`s higher chances after 06z. Not expecting any severe weather with the storms overnight into Fri morning. Widespread smoke from wildfires in Canada has made it as far south as Nebraska and feel some of this will also make it into KS, especially the northern portion. So will lower visibilities at most sties to account for this. However, with some convection around, confidence is low on how much smoke will have an impact. && .PRELIMINARY POINT TEMPS/POPS... Wichita-KICT 60 70 47 75 / 70 70 0 0 Hutchinson 59 71 44 75 / 60 50 0 0 Newton 60 71 44 74 / 60 60 0 0 ElDorado 60 70 45 74 / 60 70 0 0 Winfield-KWLD 60 71 45 73 / 80 90 10 0 Russell 55 73 41 77 / 60 10 0 0 Great Bend 56 71 41 75 / 60 20 0 0 Salina 58 74 44 76 / 50 30 0 0 McPherson 58 71 43 74 / 60 50 0 0 Coffeyville 62 71 47 73 / 40 90 10 0 Chanute 62 72 46 74 / 30 90 10 0 Iola 61 72 45 74 / 30 90 10 0 Parsons-KPPF 62 71 46 73 / 40 90 10 0 && .ICT WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...MWM LONG TERM...JK AVIATION...RBL
Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1104 PM CDT Thu May 18 2023 .SYNOPSIS... Issued at 1104 PM CDT Thu May 18 2023 Smoke aloft will remain widespread through Friday, but will be less visible as clouds increase ahead of a cold front. This front is expected to bring showers and scattered thunderstorms on Friday, but some may occur west of the Illinois River late tonight. Behind the front, high pressure will bring dry weather for the weekend, and after a brief cooldown, temperatures return to near 80 degrees on Sunday. && .UPDATE... Issued at 824 PM CDT Thu May 18 2023 Going forecast is on track this evening with only minor tweaks needed. Continue to monitor a cold front that stretches from central Wisconsin SW to near Kansas City this hour. A very narrow corridor of diminishing instability in the vicinity of this front will support a few storms to our west this evening, but should weaken to just scattered showers as it moves into the Illinois River Valley late tonight/early Friday morning. Deubelbeiss && .SHORT TERM... (Through Saturday Night) Issued at 243 PM CDT Thu May 18 2023 Key messages: 1) The smoke layer aloft is likely to persist through at least Friday night, though a period of near-surface smoke can`t be ruled out as a front passes through the area. 2) Scattered thunderstorms will be most likely near and south of I-70, though severe weather is not expected. Other than some diurnal cumulus, most of the sky obstructions this afternoon remain with the smoke. Geocolor satellite imagery shows quite the expansive area of smoke across the northern third or so of the CONUS, as far south as the Ohio Valley. Surface obstructions have been most extensive from South Dakota and Nebraska east to near Minneapolis, with widespread visibility of 1-3 miles as air is drawn downward behind the cold front. Midday RAP near-surface smoke guidance does show a period on Friday with some potential for smoky air over Illinois, though in general, the threat is not expected to be as widespread as it is now to our west. However, with the upper low currently just south of Lake Winnipeg only making it to lower Michigan by early Saturday, a wholesale upper level pattern change is not expected yet. Thus, will linger the higher sky grids behind the front through Friday evening, before gradually phasing them out by early Saturday. In terms of the convective activity, the high-res models are in good agreement with bringing the front to the Illinois/Iowa border by about 4 am, the I-55 region by late morning, and exiting areas south of I-70 very late in the afternoon. Areas east of the Illinois River appear likely to remain dry through the night. Highest rain chances before midday Friday will be west of I-55, then east of there through the afternoon. In terms of thunder potential, HREF shows some meager CAPE to around 500 J/kg in the afternoon across the southeast third of the forecast area, with the best chances of any thunder in that area. However, will maintain some isolated thunder chances as far back as the Illinois River late morning as the front passes. Behind the front, surface high pressure builds across the central U.S. on Saturday, edging into Illinois by evening. Will overall be a pleasant start to the weekend, with highs in the lower 70s and some less smoke-filtered sunshine. Geelhart && .LONG TERM... (Sunday through Next Thursday) Issued at 243 PM CDT Thu May 18 2023 Precipitation chances during this period look to be rather meager, as upper level ridging gradually amplifies over the central U.S. The GFS tries to get some nearby convection going on Tuesday due to a weak upper low over the middle Mississippi Valley, though this appears to be an outlier at the moment and the forecast will be kept dry. Main impact from this ridging will be a gradual building of warmth as the week progresses, with highs in the mid 80s Tuesday-Thursday. However, periodic convection near the Gulf Coast should keep any meaningful moisture advection cut off from us, so heat index levels should not be an issue. Geelhart && .AVIATION... (For the 06z TAFs through 06z Friday Night) Issued at 1104 PM CDT Thu May 18 2023 A cold front will slowly move across central Illinois through the day Friday. Ahead of the front, VFR conditions and S/SSW winds will prevail overnight. Winds will back to the SW Friday morning and afternoon with scattered showers near the front. A few isolated storms may develop during the afternoon, but low coverage precludes any mention in the forecast at this time. Winds will turn northwesterly behind the front and precip chances will diminish. Will have to continue to monitor for MVFR vsby behind the front as smoke overspreads the region. For now confidence remains low, but upstream sites over Iowa and Nebraska continue to show widespread 3- 5SM visibility. Deubelbeiss && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$ WFO ILX
Area Forecast Discussion
National Weather Service Louisville KY
930 PM EDT Thu May 18 2023 .Forecast Update... Issued at 930 PM EDT Thu May 18 2023 Skies at mid-evening were partly cloudy across the region. Temperatures varied a bit with mainly lower 70s across much south- central and east-central KY. A small portion of north-central KY had temperatures in the low-mid 60s. Convection continues to wind down across the Tennessee plateau this evening. Convective outflows heading northward will produce some isolated-scattered showers and storms across portions of south-central KY (mainly along and east of I-65) for the next few hours. Latest HRRR and RAP runs agree with this, and some of the activity may make it as far north as the BG Parkway before fading away due to the loss of heating. For the remainder of the overnight, combination of the weak warm advection aloft along with some slight isentropic lift will result in stratus development. So most spots will see mostly cloudy conditions develop after midnight. Lows will range from the upper 50s over southern IN to the lower 60s over KY. && .Short Term...(Tonight through Friday evening) Issued at 310 PM EDT Thu May 18 2023 Synopsis...Mid-level water vapor imagery depicts a small shortwave currently moving through the Tennessee and lower Ohio Valleys while a shortwave ridge occupies the rest of the Ohio Valley. Progressive flow aloft will allow the current features to continue moving to the east while an upper low and attendant frontal surface swing from the Upper Midwest to the Great Lakes. Tonight...Rest of the afternoon will exhibit quiet conditions for most of the region except the Lake Cumberland region and surrounding areas where a chance of showers and isolated storms still exist. Current satellite imagery shows increasing cloud coverage in response to the weak moisture advection ahead of the small shortwave. RAP-based guidance still indicates 1000-1500 J/kg of SBCAPE, weak deep-layer shear and low-level dry air. As a result, there could be a non-zero chance of pulse convection with brief but strong downdrafts as DCAPE values range anywhere between 600-800 J/kg during the late afternoon. This convective activity will be decaying after sunset while it moves northward with a few leftover showers around Lexington before midnight. Rest of the night should stay dry with light southerly winds while a low-level stratus layer build over the western half of the area. Friday...Winds will keep rotating to the southwest with a gradual increase in moisture as the cold front approaches from the northwest. A mostly cloudy day is anticipated with some low-topped, isolated showers and spotty lightning strikes during the afternoon; however, the deeper convection are expected after 20/00Z (see Long Term section below for more details). Overall, decided to trend down precipitation chances and coverage during the afternoon compare to NBM following the HREF and NAM guidance. Temperature wise, lows will be in the upper 50s to low 60s while afternoon highs will probably reach the low 80s. && .Long Term...(After midnight Friday night through Thursday) Issued at 300 PM EDT Thu May 18 2023 Friday Night - Saturday... A positive tilt trough axis and associated cold front will be pushing into and through our region Friday night. Expect fairly widespread showers, and a few thunderstorms possible. In general, coverage should be increasing from sunset onward across our NW CWA, spreading slowly southeastward through the night. Overall, not expecting much strength to any storms due to several limiting factors. 1.) Already meager instability will be steadily waning after sunset. 2.) Mid level lapse rates will remain quite poor (~5.5C/Km). 3.) Deep layer shear will be modest at best, and most of that is from 500mb upwards thanks to a speed max. However, if you look at soundings, convective clouds tops would probably peak between 15-20 K feet. So, again most of that shear likely wouldn`t even be realized. Even thunder/lightning may be hard to come by with such shallow convection. The cold front will be pushing through by Saturday morning, however the upper trough axis will linger just a bit. As a result, we will likely have to hang onto some lingering pops, at least the first part of the day, and especially over our south and east. Thereafter, expect drier conditions heading into the later part of the day from NW to SE as Canadian high pressure begins to build in behind the front. Highs Saturday are tricky given cool advection, cloud cover uncertainty, and lingering precipitation, but low to mid 70s seems reasonable. Later Saturday - Thursday... Looking for a mostly dry pattern to set up for the late weekend and into the first half of next week as Canadian high pressure centered to our north dominates the surface. Aloft, there are a few question marks about the upper pattern as we get toward the middle of next week, and this is hurting confidence a bit. A weak disturbance within an overall benign upper pattern could be enough to keep mention of some slight chance pops for Tuesday. Outside of that, will stay with dry mention. Mid to upper 70s rule for Sunday, with temps trending milder into early next week. Mid 80s should be common by mid week. && .Aviation...(00Z TAF Issuance) Issued at 720 PM EDT Thu May 18 2023 VFR conditions are expected this evening and into the overnight hours at the TAF sites. Winds this evening will be light and variable at times, but the overall winds should be out of the northeast with speeds of less than 5 knots. Winds overnight will shift to the southeast and eventually the southwest after sunrise. Low stratus is expected to develop across the region overnight. Cigs will likely remain VFR though a drop to MVFR looks likely after 19/12Z at the terminals. Winds on Friday during the day will be out of the southwest at 5-10 knots. Some scattered showers and possible storms will be possible across the region after 19/18Z, though the most widespread precip will likely occur after 20/00Z. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update.......MJ Short Term...ALL Long Term....BJS Aviation.....MJ
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
835 PM CDT Thu May 18 2023 .UPDATE... Issued at 835 PM CDT Thu May 18 2023 Going forecast is in good shape this evening, with some only minor adjustments made to add some hourly detail in pop trends from after midnight tonight into Friday with the approaching cold front. Evening GOES vapor imagery depicts a deep mid-level trough and embedded closed low centered near the Minnesota/Saskatchewan/Ontario border. At the surface, an elongated area of low pressure was noted from Ontario into the upper Mississippi Valley, with a cold front trailing southwest across Iowa and into southwest Kansas. The mid- level trough is progged to propagate southeast across the upper Great Lakes through Friday, with the cold front pushing east across the WFO LOT forecast area through the day. Scattered showers and a few thunderstorms were evident in regional radar data along and ahead of the cold front, and these are expected to move into northern Illinois after midnight tonight then work their way southeast during the day Friday with the front. Instability is limited, with forecast soundings from various guidance generally less than 500 J/kg. Precip should largely clear areas northwest of the I-55 corridor by early afternoon, exiting the southeastern parts of the cwa by early Friday evening. Winds turn breezy from the northwest behind the front, bringing in drier air. Current RAP near-surface smoke forecasts suggest there could be some low-level Canadian wildfire smoke in the area immediately behind the front Friday afternoon/evening. Current surface obs depict smoke behind the front across MN/IA/NE, with visibilities less than 5 miles in spots. Don`t have a good feel for how impactful this will be here, with RAP forecasts indicating decreasing smoke concentrations farther east, but would not be surprised to have smoke in lower levels in the wake of the front Friday/Friday evening. Ratzer && .SHORT TERM... Issued at 256 PM CDT Thu May 18 2023 Through Friday night... While we have primarily cloud free skies across the area this afternoon, smoke from Canadian wildfires continues to result in a milky sky with filter sunshine. This will be the general theme through the remainder of the day as temperatures climb through the 70s inland from the lake. An onshore wind will keep temperatures cooler along the IL lakeshore areas. Our next weather maker is a cold front currently shifting across the Upper Midwest. This front will shift eastward across our area during the day Friday. A modest increase in low-level moisture (lower 50s dewpoints) accompanying this frontal boundary will support increasing cloud cover late tonight, followed by a period of showery precipitation (possibly a few embedded thunderstorms) on Friday. The prime time for this activity is expected to be during the morning hours, through around midday for much of far northern IL, with the focus for these showers and embedded storms gradually sagging southeastward across east central IL and northwestern IN into the afternoon. Drier weather, with breezy northwesterly winds are expected to develop across the area in the wake of the frontal passage Friday afternoon. While otherwise quiet weather is likely in the wake of the frontal passage tomorrow afternoon, the potential exists for some reduced surface VSBYs to develop due to wildfire smoke reaching closer to the surface. This has, and continues to be the case within the post cold frontal airmass, with current upstream surface observations across the Dakotas into parts of the Upper Midwest indicating reduced visibilities from wildfire smoke reaching the surface. It still remains a bit unclear how extensive this smoke will be at the surface in our area as the front moves through tomorrow. However, I would not be surprised to see more hazy conditions closer to the surface tomorrow afternoon. KJB && .LONG TERM... Issued at 256 PM CDT Thu May 18 2023 Saturday through Thursday... Upper-level ridging will begin to establish itself over the central and eastern CONUS beginning this weekend, and correspondingly, positive MSLP anomalies will be the rule over the Great Lakes and northeast through at least this middle of next week. Accordingly, we will find ourselves in a quiet and dry pattern over this time frame which should feature no precipitation, plenty of sunshine, and moderating temperatures without a notable increase in humidity. Saturday should be the coolest day of the current extended forecast period with highs ranging from the mid 60s to mid 70s for most. Temperatures should then climb well into the 70s at most locations on Sunday before continuing their ascent into the 80s as we head into the upcoming work week. Temperatures should be cooler near the lake each day, though, as daily lake breezes can be expected with the progged mean positioning of dominant eastern CONUS surface high pressure regions over this time frame not really being conducive to offshore flow. It should also be said that high temperatures may end up being a bit lower than what`s currently in our forecast grids if prevailing northwest flow continues to funnel smoke from Canadian wildfires in our general direction that ends up filtering some of the otherwise abundant sunshine that we are expected to see over the next several days. On a final note, with the richer Gulf moisture likely to be steered into the Great Plains next week, dew points here are expected to primarily remain in the 40s and 50s through the entirety of the long term forecast period. This will lead to comfortable humidity levels during the daytime, so go out and enjoy the great weather over the next several days! Ogorek && .AVIATION... For the 00Z TAFs... 644 PM...Forecast concerns include... Wind shift to southwest tonight. Scattered showers, possible mvfr cigs Friday morning. Gusty northwest winds Friday afternoon. Possible haze/smoke Friday. Possible wind shift/lake breeze late Friday afternoon. A lake breeze has moved west of the terminals, shifting winds east/southeast. Winds will turn back southeasterly this evening and are expected to shift to the southwest overnight. A cold front will move across the area late Friday morning shifting winds to the west/northwest. Winds will continue turning northwest and then likely to the north/northwest by late Friday afternoon. Gusts to 20kts will be possible Friday afternoon. A lake breeze may develop Friday afternoon and move inland through GYY and possibly to MDW. Confidence is low for how far inland in IL this lake breeze would move. For now, have not included this lake breeze in the MDW or ORD taf. Scattered showers are expected along and ahead of the cold front Friday morning. Current tempo mention seems reasonable for the best time period and expected coverage. There is a small chance for an isolated thunderstorm along the front, but no mention at this time given the expected isolated coverage and short duration. Some mvfr cigs are possible with the showers and the front though guidance has been slowly lifting cigs as this time period approaches and has mainly low vfr cigs. Smoke, being reported as haze, from Canadian wildfires is widespread across the midwest, behind the cold front noted above. There is limited skill and guidance for forecasting smoke but there is some potential that this smoke will move across northern IL Friday, behind the cold front, possibly reducing visibilities into the 3-5sm range. Confidence is low and for now have not included smoke but its possible it will be needed with later forecasts. cms && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1051 PM CDT Thu May 18 2023 .UPDATE... Issued at 1048 PM CDT Thu May 18 2023 Updated for 06z Aviation Discussion below. && .DISCUSSION...(This evening through Thursday) Issued at 137 PM CDT Thu May 18 2023 KEY MESSAGES: (optional) - A couple of strong to severe storms possible over from far southeast Minnesota into west central Wisconsin later this afternoon. - Poor air quality due to wildfire smoke from Canada will linger into tonight, but will improve overnight into Friday. Some smoke will still be present aloft on Friday. - Dry and pleasant weather for this weekend. - A warming trend is expected from the weekend onward into next week. A line of showers in association with a surface cold front will continue to push east across the remainder of the forecast area this afternoon, with a few thunderstorms possible over the far eastern portion of the area after 4 PM. Widespread severe weather is not expected, but there may be sufficient instability and shear for some marginally severe hail. Low-level smoke affecting visibility and air quality will persist for about eight hours after frontal passage at any given location based on observations and RAP smoke forecasts. However, smoke aloft looks to stick around into Friday evening as it rotates around the upper low as it moves across northern Minnesota late tonight and into the eastern Great Lakes Friday night. The weather looks benign once we get the current issues out of the way, with dry weather and warming temperatures expected from the weekend through most of next week. Northwest upper flow looks to become zonal by the end of the weekend, and will transition to southwest flow by midweek. We`ll see a prolonged period of warm advection through the week, with the surface trough remaining well to our west through at least Wednesday. The ensemble guidance starts to exhibit more spread after Wednesday, with some solutions bringing the surface trough eastward, which would bring chances for SHRA/TSRA Thursday into Friday. Can`t argue with the consensus approach at this point, so included chance PoPs at the end of the period, but given the large scale pattern it wouldn`t be surprising if things progress more slowly and we remain precipitation free until Friday or later across most of the area. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1048 PM CDT Thu May 18 2023 By the beginning of the period, the front will have moved through all but the EAU area, with winds from 310-340 at 10-15kts with some occasional 20-25kt gusts through the night. We begin VFR with the exception of some smoke in EAU, but likely see many sites dropping to borderline MVFR with cigs between 025-035 for much of the day tomorrow. Skies scatter out as cigs lift by tomorrow afternoon, with clearing skies towards the end of the period. KMSP...Winds will be the primary concern alongside potential for MVFR conditions to begin the daylight hours tomorrow. We trended a bit lower for CIGS compared to the 00z TAF due to higher confidence in the low level moisture. /OUTLOOK FOR KMSP/ SAT...VFR. Wind SW 10-15kts. SUN...VFR. Wind SW to NE 5-10kts. MON...VFR. Wind SE 10-15kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ DISCUSSION...WFO MPX AVIATION...TDH
Area Forecast Discussion
National Weather Service Marquette MI
635 PM EDT Thu May 18 2023 .SHORT TERM...(Into Tonight) Issued at 346 PM EDT THU MAY 18 2023 Latest water vapor imagery and RAP analysis show a closed low centered over southern Manitoba with shortwave ridging over the Upper Great Lakes. Gusty southerly winds have developed today ahead of the approaching cold front from the Northern Plains with gusts reaching 30-35 mph over many east half portions of the U.P with a few downsloping locations along Lake Superior reaching over 40 mph. However, abundant smoke at mid-upper levels from the Western wildfires has limited mixing across the area today keeping temps cooler than expected and thus RHs have not dropped as low as originally forecast. While temps have reached into the mid 60s over the central counties, eastern counties have thus far have struggled to reach 60F at many locations given the thick smoke aloft and onshore flow off Lake Michigan. This has resulted in RHs generally 35 percent or above across much of the forecast area where Red Flag Warnings are currently posted. There could still be a chance of increased heating and mixing over the next hour or two which could lower RHs a bit more so will keep the RFW headline going into early evening over the east half counties, but confidence is waning that RFW criteria will be reached for RH values. The focus then shifts to the mid-level low over southern Manitoba which is fcst to move into the western fcst area later tonight. The associated cold front out ahead of this feature will reach western Upper MI in the next few hours and then push e thru the rest of the cwa tonight, accompanied by showers which will last roughly 3hrs or so. Given little or no instability as noted on SPC mesoanalysis fields have taken thunder chcs out of the fcst late this afternoon into tonight. There will be a break in the showers over the western counties after the main band along the front passes through late afternoon/early evening. Showers tied closely to the mid-level low center will then arrive over western Upper MI, mostly after midnight. Model consensus suggests rainfall amounts generally on the order of 0.10-0.75 inches by 12z Fri, greatest over the western counties and least over the east half. Under mostly cloudy skies, expect min temps in the 40s tonight, possibly near 50F far south central. .LONG TERM...(Friday through Thursday) Issued at 354 PM EDT THU MAY 18 2023 Amplified upper level flow regime across northern North America becomes more zonal over the next week. During this time, troughing across eastern Canada consolidates across the Baffin Island and Greenland region as western Canada and Pac NW ridging shifts east toward the Great Lakes region. This allows for slightly below normal temperatures to transition to a much above normal regime by the end of next week. After rain chances end Friday night, 4-5 days of dry weather are expected before precip chances return late next week. Starting with Friday morning, most of our area will be between waves of precip as the initial cool front exits stage right and a secondary trough enters stage left. There could be a few light showers during the morning, but I think most places will have broken low level cloud cover that increases/thickens through mid to late afternoon. Decent upper level support suggests a few hours of fairly widespread rain showers, but by the late afternoon or evening clearing should begin spreading eastward across our area. By Saturday morning, our whole area should be mostly clear with mostly sunny skies leading to a pleasant day with most places warming to around 70F. Deep mixing up to around ~6kft is expected especially for south-central locations where northwest downsloping should be maximized leading to gusty winds and low RH values. A somewhat stronger wind field across the Keweenaw and winds backing to a more favorable westerly wind direction may result in a few hours of a breezy conditions there Friday evening. Shortwave ridging arriving around sunset allows the boundary layer to stabilize with winds diminishing. Another Hudson Bay high approaches on Saturday behind a seasonably strong cold front dropping south into our area late Saturday night/early Sunday morning. Gusty north to northeast winds off Lake Superior prevent temperatures from warming much through the day with fairly steady temps in the upper 40s, but temps should be able to warm up to around 60F farther inland. The high pressure system sinks southeast toward the Ontario/Quebec border by Monday morning when light winds and clear skies may allow for another round of frost or freeze across the UP. The interior west seems most likely to get below freezing, but patchy frost appears possible across our entire area. Temperatures warm into the 60s and 70s under sunny skies and light winds across the UP with RH values likely to get below 30% for most spots. A weak front approaches on Tuesday with an increasing pressure gradient ahead of it allowing for gusty winds and potential for more elevated fire wx conditions. While precip with this frontal boundary cant be ruled out, chances are more likely on the other side of Lake Superior. The upper level ridge axis shifts overhead on Wednesday then to our east on Thursday allowing for a more amplified WAA regime late next week with moisture and precip chances increasing accordingly. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 635 PM EDT THU MAY 18 2023 A narrow band of showers will move through the area overnight. Wraparound moisture will move in after a cold front moves through late tonight. Conditions will start off VFR at IWD and SAW and then will deteriorate to high IFR/low MVFR tonight into Fri. CMX will be a different story as rain over Lake Superior could bring in some fog and they will go from MVFR to IFR later tonight. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 354 PM EDT THU MAY 18 2023 Low pres and the associated cold front are currently dropping se across far western Lake Superior with southerly winds ahead of the front. The strongest southerlies up to around 30 kt are across the eastern half of the lake at higher elevation platforms where a few gale force gusts to 35 kts are possible late this aftn/evening. This cold front reaches the far eastern lake early Friday morning with lighter westerly winds generally gusting below 20kt behind the front. A few northwesterly wind gusts up to 25kt are possible across the central Lake Friday afternoon before light winds return and continue through Saturday morning as brief ridging moves across the lake. Ahead of the next cold front dropping s toward Lake Superior, wsw wind gusts will increase to 20-25kt across w and central Lake Superior Sat aftn/evening, especially around the w and n side of the Keweenaw. As the front sweeps s across Lake Superior Sat night, winds will shift to n to ne, and there could be a period of gusts to around 30kt for a few hrs after the front passes due to colder air pushing into the area and incoming pres rises. Winds will diminish to mostly under 15kt Sun night as high pres ridge arrives. The ridge will shift toward the Lwr Great Lakes and New England on Mon. SE to S gusts increase to 20-25kt Monday evening or overnight, especially across the eastern half of the lake. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Red Flag Warning until 8 PM EDT this evening for MIZ005>007-013- 014-085>088-095-096. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Voss LONG TERM...EK AVIATION...07 MARINE...EK
...Updated Aviation Forecast Discussion...

.DISCUSSION... Issued at 353 PM CDT Thu May 18 2023 Key Messages: - Shower and non-severe thunderstorm chances this afternoon and evening as a cold front moves through. - Smoke from wildfires has reached the surface behind the front and has lead to reduced visibility and air quality. - Quiet and pleasant weather Friday through Tuesday. Have been working to keep track of smoke and its impacts throughout the day. Worst conditions have generally been directly behind the front, but visibilities below 2 miles stretch all the way back into South Dakota. A second reinforcing cold front has brought cooler temps and some refreshingly smokeless skies to northern South Dakota. We look forward to that. Guidance has been pretty terrible with picking up on the reduced visibility. HRRR has not found the smoke at all and the RAP has been doing well for smoke placement but not visibility. I`ll lean on the RAPs trends while ignoring its actual numbers. Expect the smoke to grow denser after dark - especially south of I-80. OAX NEXRAD has picked up on a few updrafts along the front, just south of the Lincoln and Omaha metros. A few bolts of (intra-cloud) IC lightning have been detected. Expect those showers/thunderstorms to remain on the weak side. No severe weather is anticipated with negligible CAPE and shear. Some gusty winds may be noted. Some light and sparse showers may continue along the NE/KS state line overnight, but very little QPF is expected. Winds will pick up behind the secondary front that will push into the CWA around 10pm. Gusts up to 28mph or so are expected. Again, this will bring a supply of clear air to the area as the upper low tied to the front meanders east toward Detroit. CAA at nearly -3C degrees an hour at 850 hPa will leave us with highs mostly falling below 70F on Friday afternoon, with the breezy winds making it feel a touch cooler. With high pressure overhead on Saturday, winds will be veering from north to southwest with return flow developing, but will remain negligible in speed. Add in sunny skies and highs in the mid-70s, I think it will be quite the pleasant day. Widespread 80s develop by Sunday afternoon as the southerly return flow becomes a little quicker. A weak piece of shortwave energy traverses the area on Sunday, but it`ll be hard pressed to bring much more than an uptick in cloud cover. 80s continue through the work week and weather remains dry under the high pressure ridge over the central CONUS. The pattern breaks down toward the end of next week as a trof approaches from the west. Scattered POPs are warranted for Thursday with the first piece of energy ejecting ahead of the main low. Next weekend brings more chances of showers and storms. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 623 PM CDT Thu May 18 2023 Considerable smoke has descended to ground-level this afternoon in the wake of a weak front that has now shifted south of IA. Resultant IFR to MVFR visibilities, and at times vertical visibility restrictions, are expected to continue into the overnight hours. By late tonight into Friday morning, visibilities should begin to improve as a secondary, stronger cold front moves through the area with gusty north winds. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Nicolaisen AVIATION...Mead
Area Forecast Discussion
National Weather Service Pendleton OR
820 PM PDT Thu May 18 2023 .EVENING UPDATE...Thunderstorm activity is gradually winding down this evening, however there are still a few cells in southern Deschutes county that continue to restrengthen. So far, most of the storms that have developed have produced heavy rain with small hail. Tonight, thunderstorm activity will wane with quiet conditions through tomorrow morning. Tomorrow, the forecast area will continue to be under a south to southwest flow aloft with high pressure aloft. Firstly, afternoon temperatures are expected to warm into the upper 80s to mid 90s across the lower elevations, with 70s to mid 80s mountains. Secondly, another round of isolated to scattered thunderstorms/rain showers are anticipated tomorrow afternoon and evening over the OR Cascades, central and north central OR, as well as the Ochoco-John Day Highlands. Lawhorn/82 && .SHORT TERM...Tonight through Saturday Night...A complex forecast has gotten even trickier with the addition of smoke aloft from wildfires in British Columbia and Alberta. Overall, hot temperatures are expected tomorrow and Saturday but perhaps a bit cooler than previously thought. Still expecting isolated to scattered thunderstorms each afternoon, especially on Saturday. A ridge continues to build over the area with an upper low in the Gulf of Alaska sending a moist south to southwest flow into the interior Pacific Northwest. This is expected to remain the pattern through Saturday night. A cumulus field is developing over the mountains and central Oregon this afternoon and continue to expect isolated thunderstorms over the Cascades and central Oregon as well as the higher terrain of the eastern mountains. Instability is around 500-1000 j/kg this afternoon and will be a bit stronger Friday. Precipitable water remains around 1 inch which is well above normal and is expected to remain at this level through Saturday. Shear is only about 5-10 kts this afternoon and tomorrow, so pulse type cells that form and quickly weaken are expected. Shear increases to around 20 kts and instability rises to 1000-2000 j/kg Saturday, so storms Saturday may be better organized and stronger, though do not expect any severe thunderstorms. Rain amounts in the mountains and central Oregon this afternoon and evening should be fairly light and generally no more than a tenth of an inch though thunderstorms will be slow moving and could locally drop a quarter of an inch. Tonight will see thunderstorms end this evening and weather should be quiet overnight and tomorrow morning. Lows tonight will be warm and in the mid 50s to lower 60s with upper 40s to mid 50s in the mountains. Friday will have warmer temperatures in the upper 80s and lower 90s with mid 70s to mid 80s in the mountains. Guidance is even warmer than this, though have lowered temperatures a couple of degrees due to a recent warm bias in the models and the possibility of continued smoke aloft. The focus for thunderstorms will be mainly in the Oregon Cascades, central and north central Oregon and the Ochoco-John Day Highlands and have scattered thunderstorms there and a slight chance of thunderstorms elsewhere. Rain amounts of up to a quarter inch are expected with up to a half inch with the heavier storms. Showers and thunderstorms should end during the evening. Saturday will be both the warmest day and the day with the most thunderstorm activity. Temperatures will be 20 to 25 degrees above normal with highs in the mid 80s to mid 90s and in the low to mid 80s in the mountains. Record high temperatures will be possible in the Columbia Basin, Yakima and Kittitas Valleys, Blue Mountain Foothills and the Grande Ronde Valley. The NBM is giving probabilities of 90-100% of at least 90 degree temperatures in those areas and a 35-40% chance of 100 degrees around the Tri- Cities. Thunderstorms will begin developing in the afternoon in the Cascades, Ochoco-John Day Highlands and central Oregon and increase and spread over most of the rest of the area in the late afternoon and evening. Rain amounts will be heavier over the Ochoco-John Day Highlands and southern Blue Mountains with amounts of up to a half inch expected. The stronger cells may have even heavier amounts than that. Amounts will be up to a quarter inch elsewhere. Thunderstorms may also have small hail and gusty outflow winds to 40 mph. Perry/83 .LONG TERM...Sunday through Thursday...The long term will be characterized by a pattern change. An upper level trough will begin to break down the ridge that is in place. A leading cold front will cross the region ahead of the upper level trough dropping the temperatures over the area by about 20 degrees from the current temperatures. Some lingering showers will remain and be primarily over the Cascades however, the eastern portion of the area will see an increase in thunderstorm activity as the front passes. Once the upper level low is in place, conditions will return to more seasonable weather with temperatures in the 60s and 70s and dry conditions. Sunday the models are in firm agreement with the placement and timing of the upper level trough. The cold front will be mostly offshore and will move overhead by late Sunday afternoon. EFI shows CAPE values to be above seasonal normal as the front passes over with the HRRR and CAMs models showing the values to be between 1000- 2000 J/kg. Shear will remain low causing these storms to be more pulse like in nature but high enough that an enhanced threat of larger hail and stronger winds could be associated with them. NBM shows the probability of thunderstorms to be >35% and mainly across Central Or through the Ochoco-John Day highlands and the southern Blues. Chances pf rain associated with the front range between 30- 40% and again will be primarily over the aforementioned area. Despite the pattern shift, temperatures on Sunday will remain above seasonal average as the front is not expected to cross over the Cascades until late afternoon. NBM and ensembles show the temperatures to be in the 80s through the Gorge, along the foothills of the Blues, the Basin and adjacent valleys while elsewhere will be in the mid to upper 70s. Models keep the upper level trough in place overhead through Monday night before diverging. The cold front will have already passed over the region bringing with it cooler temperatures and dry conditions through the end of the period. Clusters show that the models begin to struggle with both the position and timing of the next incoming system. The GFS has an upper level closed low moving in from British Columbia and while the ECMWF has the upper level trough already in place deepening. Regardless of the divergence, the majority of the models show a shift in the pattern. EFI continues to show the temperatures to be near normal and the NBM and ensembles show the temperatures to steadily rise. Temperatures on Monday will drop back into the mid to high 70s through the majority of the region with some of the higher terrains in the mid 60s. By the end of the period temperatures will be back in the mid 70s to 80s. Bennese/90 && .AVIATION...Previous Discussion...00Z TAFS...VFR conditions to prevail through the period. Isolated thunderstorms will continue to develop across the mountains through this evening, then redevelop by tomorrow afternoon. Only sites expected to be impacted by vicinity thunderstorms are RDM/BDN. Winds will be light, less than 12kts through the period, except at sites RDM/BDN where gusty erratic winds from nearby thunderstorms may be possible. Lawhorn/82 && .PREV DISCUSSION... /issued 436 PM PDT Thu May 18 2023/ && .PRELIMINARY POINT TEMPS/POPS... PDT 59 89 60 90 / 0 0 10 10 ALW 62 91 62 94 / 0 0 0 0 PSC 64 95 65 97 / 0 0 0 0 YKM 59 91 62 92 / 10 10 10 10 HRI 62 94 63 96 / 0 0 10 0 ELN 57 89 58 89 / 20 10 10 20 RDM 53 87 54 85 / 20 30 30 20 LGD 54 84 55 87 / 10 10 10 10 GCD 53 85 55 87 / 10 10 20 20 DLS 61 94 62 90 / 10 0 10 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ EVENING UPDATE...82 SHORT TERM...83 LONG TERM....90 AVIATION...82