Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/18/22

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
902 PM CDT Sat Sep 17 2022 .UPDATE... Issued at 859 PM CDT Sat Sep 17 2022 Convection has departed the area, thus have updated the forecast and text products to remove any thunderstorm mentions. Focus then turns to the expected fog development after midnight tonight. High resolution guidance continues to point towards fog development in the James River Valley and into the Prairie Coteau, as high pressure builds overhead and winds weaken. An earlier update trended the forecast towards the latest coverage and intensity and will need to watch for the potential for some dense fog in spots late tonight into tomorrow morning. UPDATE Issued at 629 PM CDT Sat Sep 17 2022 Updated for 00Z Aviation Discussion below. UPDATE Issued at 541 PM CDT Sat Sep 17 2022 No significant changes to the going forecast initially this evening. Surface low is near KVVV at this time and the surface boundaries extend southwest and northeast from there. Instability has increased along the boundaries, with MLCAPEs in the 1000-1400 J/kg range (along and southeast of a line from KETH to KATY) based on RAP and SPC MesoA data. We`ve had a few isolated showers develop thus far, with the strongest being elevated and behind the sfc/850mb cold front in Marshall County. With less instability to work with, don`t expect them to become severe. Still watching weak development along the front and north of the sfc low in Traverse county. It`s in better instability and has added sfc/925mb convergence/FGen, but haven`t seen too much development thus far on satellite. That being said, there is an area of high cirrus on satellite and WV imagery approaching that area, likely associated with a weak upper level disturbance, which could help lead to additional development. There`s a good chance any significant development will be beyond our CWA based on when they would interact. && .SHORT TERM...(This Evening through Monday Afternoon) Issued at 203 PM CDT Sat Sep 17 2022 Deterministic models are in good agreement in the synoptic setup through the short term. A large troughing pattern with the axis of the trough is noted from western Canada through the Pacific Coast with a closed low that will develop through the weekend. Within this main flow, a shortwave trough will continue to push northeast across the upper Midwest and Northern Plains through this evening. Another shortwave is noted to our southeast, which is also pushing northeast through MN/WI. We are on a shortwave roller coaster as another shortwave moves into the upper Midwest overnight into Sunday morning and will push east. Winds at 500mb will continue out of the southwest becoming more zonal overnight through Sunday (couple of the models have it more overnight). By late Sunday into Monday, a ridge will amplify over the area with a 500mb high over much of the central Midwest and Southern Plains. At the surface by 00Z the center of low will be over central- northern MN with the cold front along the SD/MN boarder. Through the overnight hours as this low pushes east/northeast, a surface high pressure system will move in and be centered over SD for Sunday. This high moves east early Monday with our next system moving in from the west. With this setup aloft and at the surface, precipitation chances, in the form of showers and thunderstorms, shift towards northeastern SD into western MN, ahead of the cold front this afternoon and evening. ECMWF is holding on to parts of the LLJ in the eastern CWA that could help aid in convection. Most of the stronger storms will be in central MN but there is a chance of isolated strong to severe in our CWA, mainly in Traverse and Big Stone counties who are on the western edge of this marginal threat. HREF model indicates SB/ML Cape values around 1000-1200 J/kg across the eastern/ northeastern CWA around 20Z with that threat pushing east by late this evening. Bulk shear values increase to 30-40kts. Isolated tornadoes are not out of the question in the marginal risk, especially early on in storm development. Cams/HREF note cell formation with a couple UH tracks with some of these storms, suggesting supercells around 22Z. 0-1km SRH indicate values 50-75m2/s2. RAP sounding between 19-22Z has a STP of 0.2-0.5 across western MN. The time window will be fairly short with CAMs/HREF reflectivity indicating storms pushing through between 4-7PM. Behind the system skies will clear a bit but will be back on the increase with possible fog in the am over northern ND and around the Prairie Coteau. For Sunday, the shortwave mentioned above, does bring moisture aloft in the western and southwestern cwa. However a surface high will be just to the east which could evaporate a lot of that moisture (and keeping any rain from falling anywhere else.)Overnight lows in the upper 40s/mid 50s with cooler air moving in with winds out of the northwest. Highs for sunday ranging in the 70s/lower 80s. .LONG TERM...(Monday Evening through Saturday) Issued at 203 PM CDT Sat Sep 17 2022 A somewhat amplified mid-level pattern is forecast to take shape during the long term. To start the period deterministic/ensemble data are pretty similar in depicting a cutoff low just off the California coast, with another trof digging toward the northwest CONUS. The main difference between today`s model runs and previous ones is that the northern trof appears to be more progressive, and brings a front through the Northern Plains earlier. Some rain chances exist for Monday as WAA pattern shifts from southwest to northeast across the state. However, along with the WAA comes increasing warm air aloft with H7 temps pushing to near or above 10C over a large part of the region. The result being increasing MLCIN over the forecast area. For now will keep low pops in place. Forecast is then pretty much dry until near next weekend. At that time, the old cutoff near California is expected to eject northeast into the Northern High Plains region, and then track slowly east over the Northern Plains. Most long term guidance is onboard with this scenario. As for temperatures, 2m temp anomalies suggest above to well above normal readings for the early part of the period. But, behind a front for Wednesday-Friday, temperatures are expected to fall back to near or even below normal. && .AVIATION...(For the 00Z TAFS through 00Z Sunday Evening) Issued at 629 PM CDT Sat Sep 17 2022 Terminals KABR,KATY,KPIR,KMBG A couple of concerns for the first half of the TAF forecast. First, have some lingering MVFR ceiling behind the cold front over the James River Valley and have been seeing KABR bouncing between VFR/MVFR ceilings over the last few hours. Expect that to continue this evening and eventually see the shallow/thin clouds dissipate. When/If that occurs, expect winds to be light under high pressure and should see some fog development over the James River Valley and Prairie Coteau after midnight and continue into tomorrow morning. Guidance indicates KABR being the site that has the lowest visibility and have indicated LIFR conditions for now. Then the focus turns to an upper level disturbance approaching from the Rockies. This will bring the potential for light rain to central SD tomorrow morning, but at this time, expect conditions to remain VFR. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...SRF SHORT TERM...MMM LONG TERM...TDK AVIATION...SRF
Area Forecast Discussion
National Weather Service La Crosse WI
1102 PM CDT Sat Sep 17 2022 .DISCUSSION...(This evening through Saturday) Issued at 242 PM CDT Sat Sep 17 2022 Key Messages: - Shower/Storm chances increase this evening - Warm start to the week/Much cooler for the first day of Autumn(Thursday)/end the week - Fog potential Monday morning - Rain/Storm chances Monday night into Tuesday and Tuesday night into Wednesday with the cold front Showers/Storms Tonight... Early afternoon satellite water vapor imagery showed the first subtle shortwave associated with this morning`s cloud cover and scattered showers/sprinkles pushing out of the area to the northeast. A second subtle shortwave follows behind just entering central Iowa. Radar imagery shows the associated weakening MCS moving through southeastern Iowa entering far northwestern Illinois. This cluster of showers/isolated storms appears to be nearly aligned with the latest RAP analysis of the moisture transport field. Showers are expected to redevelop and expand in coverage across the forecast area heading into this evening with additional moisture advecting into the region from an increasing southwesterly low-level jet. Cannot rule out some isolated thunder with 1000-1500 J/kg of MLCAPE being available. Any storms that do develop, are anticipated to be elevated and the overall risk for severe storms is greatly limited. Overnight as high pressure builds into the Dakotas and a cold front sweeps east/southeastward through the area, precipitation chances are anticipated to exit a majority of the region by sunrise Sunday morning. Quiet weather will persist throughout the day with afternoon temperatures reaching into 70s and a few locations topping out near 80. Sunday night through Tuesday... The 500 mb pattern through Tuesday is for a piece of the broad area of low pressure over Canada near Ontario to slide toward New England with another...deeper trough pushing toward Montana and North Dakota. Heights increase for Monday and begin to decrease again by 21.00Z. Depending on how far south the 850mb front makes it Sunday night, a few showers/storms could linger across southern areas. Behind the cold front, surface high pressure settles in with decreasing surface winds. Forecast soundings show an inversion setting up in the low levels with surface winds decoupled, but winds above the surface in the 10 to 15kt range. Low level dewpoints spreads appear to be close to zero, thus looks like a good potential for valley fog and more widespread fog if the winds aloft drop down early enough. The low level dewpoints mix out during the morning with highs topping out in the 70s to lower 80s. Monday night into Tuesday, the 500 mb longwave trough is still well to our northwest and into Canada, however, there is good agreement with a lead wave heading toward the upper Mississippi Valley. Although the bulk of the organized precipitation with the wave is north of the International Dateline, the low level jet is forecast to strengthen over Iowa with the potential for scattered showers/storms across parts of the forecast area. MUCAPE is around 2500 J/kg with 40 to 50kts of deep layer shear/0-3km shear of 35- 45kt. Although not the most favorable time of day, could support elevated storms with hail before they shift east if the forcing/shear is this strong. The forcing shifts the storm chances east during the afternoon with warmer temperatures aloft arriving, but will have to watch this with lingering 850mb moisture. Tuesday`s highs should continue to be well above normal with highs in the 70s and 80s. Turning Colder For the First Day of Autumn/End of the Week... The 500mb trough swings through with lowering heights and convergence along the front. Showers/storms increase overnight Tuesday and Wednesday as the cold front pushes south. After highs in the 70s Wednesday, sharply cooler temperatures arrive Wednesday night. Lows for the first morning of Autumn are forecast to be in the 40s and 50s, with 50s and 60s for highs Thursday. Still cool Friday with highs in the 50s and 60s with rain chances returning. && .AVIATION...(For the 06Z TAFS through 06Z Sunday night) Issued at 1100 PM CDT Sat Sep 17 2022 Main cluster of showers and storms expected to largely stay south of the TAF sites overnight. Isolated convection is starting to develop at this hour as the low level jet ramps up, but most of the activity is expected to stay over northeast Iowa and far southwest Wisconsin. Very small chance that anything would graze LSE. That low level jet will lead to marginal LLWS at LSE for several hours overnight, with a lesser chance for impacts at RST early in the period. Main aviation concern continues to be potential for developing low ceilings towards daybreak. Low pressure and a weak cold front dropping into central Minnesota now are already producing MVFR to IFR ceilings up that way, and that stratus is likely to spread into the TAF sites as the front eventually approaches with MVFR to IFR conditions. Winds shifting to the northwest behind the front will bring in some drier air that should scour out the low ceilings by mid to late morning with VFR conditions thereafter. Winds will generally be light through the period. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ DISCUSSION...Peters/Zapotocny AVIATION...Kurz
Area Forecast Discussion
National Weather Service Grand Rapids MI
1201 AM EDT Sun Sep 18 2022 LATEST UPDATE... Aviation .UPDATE... Issued at 808 PM EDT Sat Sep 17 2022 I have increased the risk for getting wet tonight to between 70 pct and 80 pct in a triangle area from near Whitehall to Mount Pleasant to South Haven. The timing of the showers and a few thunderstorms would be between 10 pm and 5 am. This update is based what every run of the HRRR since 15z is showing. The latest NAMNEST and RAP models also show this. Considering there is an MCV over Iowa heading this way, I have increased the pop significantly in the area I wrote about above and adjusted the area of heavier precipitation and pop farther south. As for severe potential tonight, that is limited at best. The effective bulk is negligible. However the mix layer and most unstable cape is between 500 and 700 j/kg by 2 am over our western CWA, north of I-94. This suggests some thunderstorms are possible overnight. Several runs of the RAP model show a 25 to 35 knot low level jet amid at MKG by midnight. Model sounding look fairly moist through 200 mb,, the precipitable water forecast to be near 1.5 inches and RH over 80 pct. This would tell me the rain should have no problem getting to the ground. I could see some isolated locations getting over a half inch of rain tonight. Most of the storms should be north of a line from Holland to Lansing. Most areas should see at least a few hundredths of an inch of rain tonight, if you live north of I-94. && .DISCUSSION...(This evening through next Saturday) Issued at 331 PM EDT Sat Sep 17 2022 -- Chance for showers/few storms this evening -- The increase in moisture from the southwest flow has boosted MUCAPE values to 500-1000 J/KG. Highest values are across Central Lower Michigan where surface dew points are 62f to 64F. A shower with some decent low level reflectivity (50dbz) has recently developed in Montcalm County. We expect more shower development this evening as well as some isolated thunderstorms. This activity should fade with sunset. -- Better chances for precipitation late tonight/Sunday morning -- A better chance for showers and thunderstorms will come late tonight and Sunday morning in a decaying mode. Showers and storms should form on the low level jet axis in Iowa tonight and move east into our area late. We should see precipitation increase after 06z, with the best chances probably towards 12z. This activity will likely be in a diminishing phase as it moves through. The rain and clouds will likely temper our instability for Sunday. -- Small chances for showers and storms again Sunday afternoon/night -- The Sunday morning precipitation will likely curb what activity develops in our area in the afternoon and evening. The HREF shows this well with much of the redevelopment in the afternoon and evening off to the south and east of our area. If the activity comes in weaker tonight however our chances will increase for precipitation on Sunday. At least some chances for precipitation will continue into Sunday night as the front will be sliding through the area at that time. -- Work week forecast -- After a dry Monday, it appears we have the chance for some nocturnal showers and storms Monday night into Tuesday morning with a warm front in the area. A healthy 40 knot low level jet is aimed in our direction Tuesday morning so this will be a time frame to watch. A cold front will bring additional chances for showers and storms Tuesday night. Cooler and drier weather overall settles into the area for much of the rest of the forecast. 850mb temperatures plunge from around +20C Tuesday night near the front to around +3C on Thursday. Not out of the realm of possibilities to see some lake effect rain showers on Thursday with Delta Ts near 17 degrees C. && .AVIATION...(For the 06Z TAFS through 06Z Sunday night) Issued at 1200 AM EDT Sun Sep 18 2022 VFR conditions are expected at all the terminals overnight with scattered rain showers. Potential for isolated storms overnight is too low to warrant inclusion in any of the terminal forecasts at this time but forecasts will be updated accordingly if thunderstorms develop. VFR conditions are forecast to continue at all the terminals Sunday through Sunday evening. Showers will redevelop Sunday evening. There is also potential for a few thunderstorms but it is too early/potential is too low to mention them in the terminal forecasts at this time. Thunderstorms may be added to some of the terminal forecasts for Sunday evening later today. && .MARINE... Issued at 331 PM EDT Sat Sep 17 2022 Earlier today we updated marine headlines to push them through tomorrow and expand in area to the south. Through this evening the Beach Hazards Statement (BHS) and Small Craft Advisory (SCA) are in effect for areas up towards Big and Little Sable Points. After 06z tonight, that expands to include marine areas southward to Holland. Southwest winds will boost waves heights to 3-5 feet this evening near the points. After dark tonight, southwest winds ramp up further with a low level jet increasing to around 40 knots at 1,500 feet. Some of this wind will reach the water surface, more on the order of 15-25 knots which should build a wave field to 3-5 feet in all areas north of Holland. It is not out of the realm of possibilities that we may need headlines further south as well. There is a chance from another increase in southwest flow Sunday night, but only feel comfortable with headlines through the day on Sunday at this point. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement through Sunday evening for MIZ037-043. Beach Hazards Statement through Sunday evening for MIZ050-056. LM...Small Craft Advisory until 8 PM EDT Sunday for LMZ846-847. Small Craft Advisory until 8 PM EDT Sunday for LMZ848-849. && $$ UPDATE...WDM DISCUSSION...Duke AVIATION...Laurens MARINE...Duke
Area Forecast Discussion
National Weather Service Wilmington NC
1006 PM EDT Sat Sep 17 2022 .SYNOPSIS... High pressure continues to keep the area dry through mid week Temperatures look to linger near seasonal norms through the weekend, before a noticeable increase by the beginning of next week. A cold front will cross the area late Thursday and well off the coast on Friday. && .UPDATE... Only minor tweaks made to previous forecast. Isolated light showers across southern Georgetown county have diminished quite a bit. Low level easterly flow expected to advect low clouds across most of the area, particularly northeast SC, into middle of the night before skies clear up before dawn. May see an isolated, very light, shower or two move onshore coastal NE SC overnight into early morning hours. && .NEAR TERM /THROUGH SUNDAY/... The forecast has been quite a challenge along the coast today where Gulf Stream moisture has increased rapidly beneath the subsidence inversion between 3500-6000 feet AGL. An expansive shield of low cumulus developed at the base of this inversion and has advected onshore across the Cape Fear region and Grand Strand. Initially hidden by thick cirrus aloft streaming northward from convection off the GA/FL coast, this low cloud deck has become the big weather story today, holding down temps along the coast. Recently, radar even reveals showers and even a thunderstorm near Bald Head Island. Looking at a NAM or GFS forecast sounding and trying to explain how that thunderstorm was able to punch through the inversion and grow to 33000 feet is testament to how poorly those models are doing. None of the synoptic models (GFS, NAM, ECMWF) really have a clue what low level moisture fields are like currently. Their dewpoints are much too low along the coast, especially near ILM where our dewpoint has recently eclipsed 70. Among the high-res guidance the RAP is doing the best job but still has the dewpoint gradient way too washed out compared to observations. Low clouds should be more expansive than any guidance shows through the evening and possibly overnight hours along the coast. Cirrus will likely become quite dense aloft again too given recent upticks in convection over the SC/GA offshore waters. I`m trending higher than guidance for low temps along the coast tonight given the clouds and increased moisture, but near the center of the guidance envelope inland. This gives upper 60s along the coast and mainly lower 60s inland. Low level onshore winds should continue into Sunday. The inversion should continue aloft, but I have less confidence than usual about low level moisture distribution and the potential for shallow convection, especially along the coast. Forecast highs Sunday are generally 83-87, coolest on the beaches. && .SHORT TERM /SUNDAY NIGHT/... In the mid and upper levels, strong high pressure, 2 SD above normal, over the Red River will slow shift to the Ark-La-Text by 12 UTC Tuesday. Over the Carolinas, there will be a break between the Texas High and the Bermuda High, with an inverted trough over the Florida Peninsula. There is a similar setup at the surface with a break between the two high- pressure centers. The Florida trough strengthens and pushes along the Carolina coast early Monday before the ridge builds westward again quickly Monday night. With the easterly flow over the area, there is a minimal chance of an isolated shower along the southern Georgetown coast. The rest of the region will be dry. Low temperatures Sunday and Monday nights will range from the middle 60s inland to the low 70s along the beach strand. High temperatures on Monday will run from the mid-80s at the coast to the upper 80s inland. && && .LONG TERM /MONDAY THROUGH SATURDAY/... In the mid and upper levels, the strong high pressure, +2SD above normal, will remain over the heart of Texas for much of this week. The trough centered just offshore of the Carolinas will provide a break to allow Fiona to stay well east of the coast. The most significant impact will be the long period swells beginning Tuesday and peaking on Friday. Of course, this will be highly dependent on Fiona`s intensity and track. These swells will provide a dangerous rip current setup but joy for the surfing community. During this forecast period, the models show the deep 2" precipitable water staying off the coast. A cold front in the upper plains is expected to approach the Carolinas on Thursday and offshore Friday morning. At this time, the chances of precipitation continue to be low, but ahead of the cold front, the high temperatures will peak in the middle 90s inland on Thursday. Humidities are expected to be lower than normal; therefore, the heat indices will reach into the upper 90s inland. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... With high pressure to the north and a surface trough to the south, low level easterly flow is advecting moisture into the area particularly across NE SC. Easterly LLJ of 20 kt around 3kft continues bringing the low level moisture inland into early overnight hours, but expect more FEW/SCT vs ceilings. At the coast, high clouds will continue to move out of the area overnight before returning tomorrow afternoon. Low chance for brief MVFR visibilities across northern parts of the area, including LBT, where winds will be weaker closer to center of high. May see an isolated shower move onshore coastal SC during pre-dawn hours. ENE winds tomorrow around 5 kts away from coast, with more easterly sea breeze around 10 kts at coastal terminals in the afternoon. Extended Outlook...VFR. There is a low potential of early morning fog/low stratus Monday through Wednesday. A cold front may reach the area late Thursday. && .MARINE... Through Sunday: 1025 mb high pressure is moving off the Mid Atlantic coast. This will finally allow days of breezy northeasterly winds to come to an end, replaced by somewhat lighter easterly winds tonight into Sunday. Models do not have an especially good handle on the very near term where we`re seeing significant cloud cover and even some showers near Cape Fear currently. Easterly winds are bringing in a very humid Gulf Stream unstable airmass more quickly than was expected. I`m kept a 20-30 percent chance of showers in this evening`s forecast south of Cape Fear. Easterly winds are expected to maintain 10-15 kt speeds overnight, decreasing to around 10 kt Sunday afternoon. Additional isolated showers may develop Sunday. Seas should maintain 2-3 foot heights through Sunday. Sunday Night through Thursday: An easterly to northeasterly flow of 10 knots will dominate the waters Sunday night through Tuesday as an inverted trough of low pressure moves northward into the coastal waters but recedes just as quickly. Winds are expected to be light and variable before becoming southeast at 10 knots on Wednesday. A cold front approaches the waters from the west on Thursday. The winds are expected to veer and increase to 10 to 15 knots on Thursday ahead of the cold front. Seas will run 2 to 3 feet Sunday night into Monday and increase to 3 to 4 feet late Monday before settling out at 3 feet Tuesday. On Tuesday evening, the long period swells from Fiona will begin moving into the waters. An increase in swell heights to 6 ft could be seen by Thursday. Of course, this highly depends on Fiona`s track and intensity. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...ILM UPDATE...VAO NEAR TERM...TRA SHORT TERM...RH LONG TERM...RH AVIATION...VAO MARINE...TRA/RH
Area Forecast Discussion
National Weather Service Lincoln IL
804 PM CDT Sat Sep 17 2022 .SYNOPSIS... Issued at 241 PM CDT Sat Sep 17 2022 Warmer than normal temperatures stick around through early next week. Shower and storm chances return to the area tonight into Sunday, with the potential for strong to severe storms later Sunday into Sunday night. && .UPDATE... Issued at 802 PM CDT Sat Sep 17 2022 Thunderstorms are ongoing across portions of south central and southeast Iowa this evening within a corridor of warm air advection that stretches from eastern KS/NE into far western Illinois, though the greatest focus of a developing low level jet is near the mid Missouri Valley. Latest RAP indicates the eastern most storms are occurring within a region of 1000-1500 J/kg MUCAPE. The instability gradient drops off sharply west to east in western Illinois with 500 J/kg or less along and east of the Illinois River Valley, and, in the near term, instability is progged to diminish as it lifts north slightly. Some of the precip in eastern Iowa will ride the 850-300mb steering flow east into the forecast area but will be in a decaying state as it moves into a less unstable environment and becomes displaced from the better forcing from WAA to our west. Additional rounds of storms forming farther west closer to the nose of the low level jet are possible overnight, but confidence in how this will evolve remains low considering poor initialization and agreement of convective allowing models. Locally, the best chance for precip is still late tonight into Sunday morning as the low level jet veers into NE MO/west central IL. && .SHORT TERM...(This evening through Sunday night) ISSUED AT 241 PM CDT Sat Sep 17 2022 Southwest flow is setup aloft with broad upper ridging positioned over a good portion of the eastern CONUS. A few upper shortwaves paired with broad WAA will be the focus for precipitation chances through the weekend, though the most notable timeframe looks to be later Sunday into Sunday night when a stronger system sends a cold front toward the area. Shower and storm chances increase overnight tonight as 850mb moisture transport ramps up and spills into our area. Activity during this time looks to remain mostly confined along and west of I-57 and is not expected to be severe due to limited instability available. Isolated shower and storm activity may persist into the daytime hours of Sunday which may limit temperatures from reaching their full potential, though still will be warmer than normal. Breezy south winds will pull in dewpoints in the upper 60s to low 70s making the air feel more uncomfortable and allowing strong instability to build. Guidance suggests CAPEs of 2500-3000 J/kg build in by Sunday afternoon, with shear improving as we go into the evening hours when a cold front approaches from the northwest and the LLJ kicks in - bulk shear looks to be between 40-50 kts. A limiting factor at play is noted in the forecast soundings which depict a CAPing inversion present well into the evening hours. That being said, instability may be strong enough to overcome that, especially where CIN will be a tad bit lower west of I-55. CAMs remain in disagreement on where and when activity will fire up, but most of the storms should initiate over eastern IA/northeast MO and move into our CWA by either late afternoon or evening. Given the parameters at play (strong instability, favorable shear, a cold front paired with an upper wave for lift) the chance for strong to severe storms will be possible. Damaging winds and large hail are the biggest threats, though a tornado threat does exist with the focus being along and north of I-72 where isolated storms could tap into the maximized 0-1 km shear values of 20-25 kts. HREF updraft helicity is also focused in this area. A slight risk for severe storms exists across the majority of the CWA for Sunday into Sunday night. Climatologically high PWATs and warm cloud depths will be in place Sunday into Sunday night. A nearly parallel orientation of the front in respect to the flow aloft will likely support training of storms. Recent drier conditions and fast storm motion should limit widespread flash flooding, though localized pockets where storms repeat over the same areas could lead to flash flooding concerns. The 17.12Z SPC HREF pinpoints an area of mean rainfall amounts between 1-2" from extreme northeast MO into west-central IL with the LPMM product suggesting high end amounts of 2-4"+ in this same corridor. At this time, the threat seems highest from roughly Macomb southeastward toward Shelbyville. .LONG TERM...(Monday through Saturday) ISSUED AT 241 PM CDT Sat Sep 17 2022 Shower and storm chances may linger across eastern and southeast parts of the area going into Monday. Once that moves out, things look to get dry and hot for the start and middle of the new week. A strong upper ridge will progressively build over much of the US, bringing near-record temperatures to central IL. The hottest day of the week looks to be Tuesday as 850 mb temperatures near the middle 20 degrees C mark. Surface temperatures look to be in the low to middle 90s with heat indices near 100 in some spots. Records for September 20 are a couple degrees warmer than our current forecast highs, though something worth keeping our eyes peeled on. The upper ridge starts to flatten out Wednesday into Thursday as a mid-level trough dives southeast toward the Great Lakes Region from Canada. A surface low will track across the southern Canadian provinces, sending a cold front further south through the Midwest sometime Wednesday into Thursday. Cooler temperatures will make a comeback Thursday for most, but especially Friday for all. Precipitation chances with the frontal passage appear pretty low at this point, but are not zero. Cooler temperatures stick around for the start of the weekend. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 625 PM CDT Sat Sep 17 2022 A cold front is in place from the Upper Midwest back into the central Great Plains this evening and will slowly approach central Illinois tonight and through the day Sunday. Breezy S/SSW winds are expected ahead of the front with gusts to around 20 kt during the daytime hours. There will be a couple possible rounds of showers and storms that occur ahead of the front. A decaying line of showers is expected to push into central Illinois mid to late Sunday morning. A second round of stronger storms is expected late afternoon and evening, though at this time there is a considerable amount of uncertainty on timing and placement of storms. Outside of precip, expect VFR conditions to prevail through the period. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Deubelbeiss SYNOPSIS...NMA SHORT TERM...NMA LONG TERM...NMA AVIATION...Deubelbeiss
Area Forecast Discussion
National Weather Service Marquette MI
1159 PM EDT Sat Sep 17 2022 .SHORT TERM...(Through Tonight) Issued at 241 PM EDT SAT SEP 17 2022 Upper air pattern consists of a broad 500 mb trough across the western half of the U.S. with a shortwave over the northern plains. The shortwave over the northern plains heads east to the upper Great Lakes tonight. Confidence low in this forecast as unstable airmass over the area could have convection go at any time or place and with convection elevated, models tend to do a poor job predicting where things set up. Best approach continues to be a broadbrush of pops and have basically chance pops almost everywhere. Does look like areas further west and north will have the best chance for pops through tonight and that is where the highest pops are. There will be some fog around as well. .LONG TERM...(Sunday through Saturday) Issued at 352 PM EDT SAT SEP 17 2022 The longterm period starts off Sunday morning with a deep trof off the West Coast as a ridging begins to amplify across the central CONUS. Across the Northern Plains, a shrtwv is shifting east along the international border in ND and MN - this wave will bring a cold front across the UP from west to east Sunday. Behind this wave and front, the central CONUS ridge will amplify and build northward into the Northern Plains on Monday. Another wave is progged to drop SE from the Canadian Rockies into the Northern Plains Tuesday night into Wednesday, as the West Coast closed low begins to shift into the Pac NW with the central CONUS ridge weakening. This Canadian Rocky wave will pass through the Upper Great Lakes on Wed evening before an amplified shortwave ridge moves in behind it on Thursday night. By next weekend, the closed low/trof off the West Coast will begin to traverse across the Northern Plains. This pattern will bring a chance for rain throughout the week as temperatures trend above normal for the start of the week with ridging in place - by the end of the week, temperatures will return towards normal, if not slightly below normal behind a midweek cold front. Clearing skies will be the trend on Sunday as a cold front moves across the UP from W to E. Some showers and perhaps a thunderstorm or two will remain possible along the frontal axis, but there is some uncertainty on instability. Most CAMs actually hold pcpn off on Sunday, but the HRRR has remained steady with bringing some thunderstorms across the central and east with some diurnal heating - especially across the east. Dry weather will then take over on Monday with a weak sfc high pressure overhead. WAA returns on Tuesday as ridging builds across the central CONUS - this should bring temps into the upper 70s across the UP. A small perturbation to the north of the UP could bring an isolated shower, but for the most part it looks like the dynamics will split the UP - so ongoing fcst could be a little too optimistic. Wednesday will bring a stronger cold front across the UP as a strong wave drops south from the Canadian Rockies into the Upper Great Lakes. This will likely bring some gusty winds, lake-effect rain, fall-like temperatures. The cold front will bring temps back down to normal and evening blo normal into the weekend as high pressure moves in Friday and brings an end to the lake-effect clouds. && .AVIATION...(For the 06Z TAFS through 06Z Sunday night) Issued at 1159 PM EDT SAT SEP 17 2022 Challenges remain in this TAF period, as discussed in the previous TAF issuance. That said, there is increasing confidence of LL stratus struggling to move out in a timely fashion on Sunday with a copious deck building in and observed on satellite imagery tonight. KCMX will be the most negatively impacted, but KIWD and KSAW appears to at least go MVFR overnight into early Sun. As Wrly winds move in behind the finally-departing frontal boundary, drier air should assist in pushing out the stratus and lingering LL moisture. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 352 PM EDT SAT SEP 17 2022 Thunderstorms, rain, and some patchy fog will remain possible through tonight as a warm and humid airmass remains over the lake. On Sunday, a cold front will move across the lake from west to east, bringing clearing skies and the end to any remnant fog. This front will bring winds around to the W with gusts btwn 20 to 25 knots through Sunday evening. West winds remain seasonably light under 20 knots through Monday before becoming southerly on Tuesday, remaining btwn 15 to 20 knots. A potent cold front will ample cold air advection will cross the lake on Wednesday, bringing NW winds around 30 knots. At this point, gales can be expected Wednesday night into Thursday morning as the cold air moves across the lake, but will keep winds around 30 knots until more confidence in timing and placement of strongest winds is obtained. Winds relax on Thursday afternoon from the north, but will become southerly and remain light as a high pressure system passing over the lake Friday. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...07 LONG TERM...JAW AVIATION...lg MARINE...JAW
Area Forecast Discussion
National Weather Service Pendleton OR
535 PM PDT Sat Sep 17 2022 Updated the aviation discussion .SHORT TERM...Saturday through Monday...Current water vapor imagery pins a low pressure system centered west of the northern California coast. The outer band of cumulus is starting to push into central OR, with some shower activity popping up around eastern Grant County. Latest HRRR guidance shows main band of rain arriving around 5pm in central OR, spreading north-northeastward and lasting until early Sunday morning. Models continue to show convective development associated with this system, however CAMs and deterministic NAM showing limited instability and lower moisture compared to model runs over the last several days. Overall trend, in fact, has been for a drier forecast associated with this first round of rain, with QPFs ranging around 0.05 to 0.15 inches, locally higher closer to the OR Cascade crests and southern Blues. PWATs around 0.6 to 0.8 across the forecast area, around the 75th percentile for this time of year, but moisture advection into the region appears to be not has enhanced as previously seen. Still, some MUCAPE is present across the southern half of the CWA, and CAMs seem to be consistent in depicting convective cells this evening, so will leave mention of thunderstorms in the forecast, but still think majority of shower activity will be more stratiform in nature. That being said, a few isolated convective cells could certainly throw a wrench in the precipitation forecast. Trend across the models has also been to cut back on QPF across the eastern mountains of OR, with the main shield of precip taking a more north than northeast trajectory. Better chances for precip for the eastern mountains looks to be more during the day Sunday, when the area will fall under an elongated stretch of moisture from the winds aloft stretching from the southern California coast up through the northern Rockies. CAMs and NAM a bit more aggressive at depicting convection during the day Sunday, possibly due to favorable upslope enhancement, so feeling a bit more confident in the thunderstorm forecast for Sunday afternoon across the eastern mountains. Storms should be wet enough to offset any fire risks associated with lightning strikes. Forecast on Monday looks drier, with the exception of central OR as the low pressure system will stall off the California coast and remain in place for much of the week, continuing to pump moisture into the far southern reaches of the forecast area. Any rain there on Monday should be on the lighter end. Temps over the period will be cool, in the 60s and 70s today and Sunday, before warming back up on Monday as the low falls south enough to allow for skies to clear and for more efficient daytime warming to take place. Evans/74 .LONG TERM...Guidance is in excellent agreement that the long- term period will be dominated by the presence of a deep, cut-off upper-level low. This low is currently tracking southward offshore of southwest OR, and concensus among ensemble and deterministic guidance is that it will stall just offshore of SW OR/NW CA through Monday, tracking slowly southward. Weather models often have difficulty resolving how cut-off lows will rejoin the jet stream, and this case is no exception with ensemble clusters revealing that between 50-67% of the variance among members` 500 mb height fields Tuesday through Thursday are driven by timing/location differences of this upper low. Notably, the GEFS is presenting a more progressive solution than the EPS and CMC, one which is mirrored in 12Z deterministic runs. This solution would see the low spin offshore Tuesday, then track onshore and overhead into the Interior Northwest on Wednesday before rapidly departing to the east on Thursday bringing seasonal temperatures and widespread rain showers, especially for the central and eastern mountains. The ECMWF and Canadian eject the low across the region more slowly, having it linger through Thursday before exiting Thursday night into Friday, again bringing seasonal temperatures and rain showers. With either solution, thunderstorms will be possible for the central and eastern mountains if supported by daytime heating. Prior to the low tracking onshore, pressure gradients are supportive of some breezy northeast winds Tuesday for the Columbia and Deschutes plateaus, and the ECMWF EFI is highlighting this. Thursday into Friday, depending on the timing of the upper low`s passage, will see breezy to windy west winds through the Cascade gaps and into the Columbia Plateau. Ensembles and all 12Z deterministic runs are then hinting at a decaying shortwave tracking into northwest Washington or southern British Columbia on Friday with the possibility of showers for the Washington Cascades. Plunkett/86 && .AVIATION...A weather system may bring showers to all taf sites tonight. Isolated thunderstorms may also affect taf sites krdm...kbdn...kpdt...kalw...kpsc...kdls until 06z that may approach lcl mvfr conditions. Otherwise mainly vfr conditions can be expected for the next 24 hours. && .PRELIMINARY POINT TEMPS/POPS... PDT 48 68 46 78 / 40 40 20 0 ALW 50 71 49 80 / 40 40 20 0 PSC 56 73 52 82 / 50 30 10 0 YKM 48 75 48 82 / 60 20 0 0 HRI 52 71 49 83 / 40 40 10 0 ELN 48 78 48 83 / 50 20 0 0 RDM 42 68 40 75 / 70 40 10 10 LGD 47 69 45 78 / 40 60 30 10 GCD 46 73 44 81 / 50 40 20 10 DLS 55 77 53 85 / 70 20 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...74 LONG TERM....86 AVIATION...97
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