Area Forecast Discussion...Updated National Weather Service Saint Louis MO 110 PM CST Tue Nov 26 2019
.UPDATE... Issued at 102 PM CST Tue Nov 26 2019
Have upgraded the Wind Advisory to a High Wind Warning for western and northern portions of the CWA. Latest model solns suggesting higher wind gusts late tonight into Wed morning for much of central and northeast MO and into west central and southwest IL. Momentum transfer techniques suggest peak wind gusts of 50 to 55 kts fairly common with some suggestion of peak gusts near 60s kts. Given the 925mb jet core of 50+ kts, these gusts seem reasonable. The Warning may need to be extended further south to include at least the St. Louis metro area with future updates, but will need to monitor trends. Tilly &&
.SHORT TERM... (Through Late Tonight) Issued at 339 AM CST Tue Nov 26 2019 Early this morning, a strong storm system over the Rockies was carving out a deep TROF in the western CONUS and backing the flow aloft over our region from the SW. The flow becoming SW was resulting in increasing lift and moisture sliding in to our region from the south and was resulting in increasing clouds south of Interstate 70. At the surface, a cold front extended from central Illinois through the STL metro area and into southwest Missouri. Temperatures have cooled into the 30s and lower 40s behind the front but remained in the 40s to around 50 ahead of it. The storm system to our west will continue to dig and approach our area through sunset this evening, reaching eastern Kansas and Nebraska. The surface front will stall near the STL metro area this morning before returning northward as a warm front during the day today. WAA will be the main source of lift for most of the day. The expected result is to be shower development over southeast MO just before sunrise and this will then slide northward during the day gradually expanding in coverage as it does so. Later in the afternoon, additional lift from upper level disturbances streaming rapidly east from another storm system located off of Baja California are expected to create more widespread shower and isolated thunderstorm development for areas mainly south and east of the STL metro area but some of this should edge there too. Thunder during the day is expected to be limited more to the afternoon and to areas primarily northwest and west of the STL metro area. Eventually skies will be cloudy, and with rain around, temp rises will be limited and will be driven more by the surge of low level moisture northward than actual warming, with most locations peaking in the upper 50s and lower 60s. After sunset, the storm system center will track to our northwest, driving a negatively tilted TROF through our region. The lift from the TROF axis will intersect what will have then become somewhat unstable and high in moisture with the combo of the dry punch of air expected to be enough to result in a narrow band of showers and thunderstorms initiating over central MO in the evening and then rapidly racing eastward overnight. The anticipated environment that the storms will encounter will be one of high dynamics and shear but limited instability. The limited instability is deceptive in that storms are expected to be low-topped. Storms that do form will be very fast moving (excess of 50mph) and will be able to tap into 0- 1km shear of 40kts. Given all of this, there will be an isolated tornado and damaging straight line wind threats with any strong storm. The real danger is the fast paced movement of these storms and that they will be occurring at night at a time of the year most do not think they will occur. The main window for this severe storm threat looks to be from 7pm-2am, from central MO to southwest IL. In the wake of the line of storms, winds will shift from the southwest gradually becoming more westerly by 12z/Wed. Mixing will deepen with drier air building in. H925 winds are expected to be in the 40-50kt range and once mixing deepens to tap into this--likely around or shortly after midnight tonight, wind gusts to 45-50mph are expected for the entire area. This scenario will continue into Wednesday morning and has justified the issuance of a Wind Advisory.
TES
.LONG TERM... (Wednesday through Monday) Issued at 339 AM CST Tue Nov 26 2019 The wind advisory will continue into Wednesday as low pressure moves from eastern Wisconsin across northern Michigan and Lake Huron by 00Z. High pressure over the Plains will build eastward through the day, and the pressure gradient will eventually slacken enough for winds to diminish below advisory criteria...most likely by 21Z. Highs on Wednesday will be cooler in the mid 40s to around 50, but the wind chill will definitely make it feel much cooler...more like the low to mid 30s in most locations...at least until the wind drops off in the mid to late afternoon. A ridge stacked through the depth of the troposphere will build across the Mississippi Valley on Wednesday night ahead of the next trough. The ridge continues drifting east through Thanksgiving Day, and the flow will eventually turn back to the southwest as the ridge axis moves east of the forecast area and the western U.S. trough becomes the dominant weather feature. The GFS is a bit faster with this process than the ECMWF or NAM, and it has the 850mb wind swinging around over central and southeast Missouri as early as 15Z Thursday morning. This produces weak to moderate moisture convergence at 850mb between 15-18Z and about 0.01 inch of QPF. Most of the GEFS QPF plumes are flat don`t start to angle upward until between 15-18Z, and then only slightly. Feel pretty confident at this point that if there is any wintry precipitation in the morning, it`ll be very light and is likely to have no impact to travel. As the moisture deepens in the afternoon, expect light rain to overspread much of the area. Clouds and precipitation will likely limit highs to the upper 30s and low 40s. Continuing low level warm advection will produce periods of rain Thursday night through Saturday morning. Temperatures will warm up a few degrees on Friday, but it`ll still be chilly since the surface wind stays out of the east or southeast through Friday afternoon with highs only in the mid to upper 40s. A substantial piece of the trough over the western U.S. breaks off and ejects northeast overnight Friday night. The surface reflection of the closed upper low moves from the Great Plains into the Midwest Saturday. The ECMWF and GFS diverge on the speed with which the low moves east, with the GFS being about 6hrs faster than the EC. The GFS solution would push the cold front associated with this storm system through the area during the morning or early afternoon, while the ECMWF holds the front back until late afternoon and evening. The slower solution would produce a greater threat for thunderstorms on Saturday. Have opted not to add thunder to the forecast at this time and wait for better model agreement. Another shot of cold air rolls in behind the front Sunday and Monday. Lows drop into the upper 20s to mid 30s and highs struggle to reach the upper 30s and low 40s. There may be some snow showers on Sunday as the upper low tracks north of Missouri across Iowa and northern Illinois, but QPF on both the GFS and ECMWF are very light so little if any accumulation is expected at this time. Carney && .AVIATION... (For the 18z TAFs through 18z Wednesday Afternoon) Issued at 1144 AM CST Tue Nov 26 2019 Ceilings will rise this afternoon across all terminals as strong surface winds gusting into the low 20s, driven by a strong pressure gradient, enhances mixing. KCOU will increase to VFR conditions mid afternoon through the evening, while KUIN and the metro terminals will persist at IFR conditions into the evening hours. Thunderstorms and associated IFR conditions will move across the terminals this evening, reaching KCOU by 02Z, and moving to KUIN and the metro terminals between 04 and 05Z. Strong surface winds gusting up to 45 kts are expected with these storms at all terminals. In the wake of the thunderstorms sustained winds will hover in the mid 20s and gust up to the mid 40s Wednesday, prompting the Wind Advisory that is in effect for all terminals from midnight until 200 PM Wednesday. SPECIFICS FOR KSTL: Winds will be the primary threat associated with the thunderstorms that will be moving through the metro area between 05 and 07Z tomorrow, however there is an isolated risk of tornadoes with these storms as well.
MRM
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.PRELIMINARY POINT TEMPS/POPS...
Saint Louis 61 40 48 32 / 50 70 0 0
Quincy 56 36 42 29 / 60 70 0 0
Columbia 61 36 45 30 / 5 70 0 0
Jefferson City 63 38 46 31 / 5 70 0 0
Salem 59 42 48 31 / 90 90 0 0
Farmington 60 40 49 31 / 90 80 0 0
&& .LSX
WATCHES/WARNINGS/ADVISORIES... MO...Wind Advisory from midnight tonight to 3 PM CST Wednesday for Crawford MO-Franklin MO-Iron MO-Jefferson MO-Madison MO- Reynolds MO-Saint Charles MO-Saint Francois MO-Saint Louis City MO-Saint Louis MO-Sainte Genevieve MO-Warren MO- Washington MO.
High Wind Warning from midnight tonight to 3 PM CST Wednesday for Audrain MO-Boone MO-Callaway MO-Cole MO-Gasconade MO- Knox MO-Lewis MO-Lincoln MO-Marion MO-Moniteau MO-Monroe MO- Montgomery MO-Osage MO-Pike MO-Ralls MO-Shelby MO. IL...Wind Advisory from midnight tonight to 3 PM CST Wednesday for Bond IL-Clinton IL-Fayette IL-Madison IL-Marion IL-Monroe IL-Randolph IL-Saint Clair IL-Washington IL.
High Wind Warning from midnight tonight to 3 PM CST Wednesday for Adams IL-Brown IL-Calhoun IL-Greene IL-Jersey IL- Macoupin IL-Montgomery IL-Pike IL.
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.UPDATE... Issued at 102 PM CST Tue Nov 26 2019
Have upgraded the Wind Advisory to a High Wind Warning for western and northern portions of the CWA. Latest model solns suggesting higher wind gusts late tonight into Wed morning for much of central and northeast MO and into west central and southwest IL. Momentum transfer techniques suggest peak wind gusts of 50 to 55 kts fairly common with some suggestion of peak gusts near 60s kts. Given the 925mb jet core of 50+ kts, these gusts seem reasonable. The Warning may need to be extended further south to include at least the St. Louis metro area with future updates, but will need to monitor trends. Tilly &&
.SHORT TERM... (Through Late Tonight) Issued at 339 AM CST Tue Nov 26 2019 Early this morning, a strong storm system over the Rockies was carving out a deep TROF in the western CONUS and backing the flow aloft over our region from the SW. The flow becoming SW was resulting in increasing lift and moisture sliding in to our region from the south and was resulting in increasing clouds south of Interstate 70. At the surface, a cold front extended from central Illinois through the STL metro area and into southwest Missouri. Temperatures have cooled into the 30s and lower 40s behind the front but remained in the 40s to around 50 ahead of it. The storm system to our west will continue to dig and approach our area through sunset this evening, reaching eastern Kansas and Nebraska. The surface front will stall near the STL metro area this morning before returning northward as a warm front during the day today. WAA will be the main source of lift for most of the day. The expected result is to be shower development over southeast MO just before sunrise and this will then slide northward during the day gradually expanding in coverage as it does so. Later in the afternoon, additional lift from upper level disturbances streaming rapidly east from another storm system located off of Baja California are expected to create more widespread shower and isolated thunderstorm development for areas mainly south and east of the STL metro area but some of this should edge there too. Thunder during the day is expected to be limited more to the afternoon and to areas primarily northwest and west of the STL metro area. Eventually skies will be cloudy, and with rain around, temp rises will be limited and will be driven more by the surge of low level moisture northward than actual warming, with most locations peaking in the upper 50s and lower 60s. After sunset, the storm system center will track to our northwest, driving a negatively tilted TROF through our region. The lift from the TROF axis will intersect what will have then become somewhat unstable and high in moisture with the combo of the dry punch of air expected to be enough to result in a narrow band of showers and thunderstorms initiating over central MO in the evening and then rapidly racing eastward overnight. The anticipated environment that the storms will encounter will be one of high dynamics and shear but limited instability. The limited instability is deceptive in that storms are expected to be low-topped. Storms that do form will be very fast moving (excess of 50mph) and will be able to tap into 0- 1km shear of 40kts. Given all of this, there will be an isolated tornado and damaging straight line wind threats with any strong storm. The real danger is the fast paced movement of these storms and that they will be occurring at night at a time of the year most do not think they will occur. The main window for this severe storm threat looks to be from 7pm-2am, from central MO to southwest IL. In the wake of the line of storms, winds will shift from the southwest gradually becoming more westerly by 12z/Wed. Mixing will deepen with drier air building in. H925 winds are expected to be in the 40-50kt range and once mixing deepens to tap into this--likely around or shortly after midnight tonight, wind gusts to 45-50mph are expected for the entire area. This scenario will continue into Wednesday morning and has justified the issuance of a Wind Advisory.
TES
.LONG TERM... (Wednesday through Monday) Issued at 339 AM CST Tue Nov 26 2019 The wind advisory will continue into Wednesday as low pressure moves from eastern Wisconsin across northern Michigan and Lake Huron by 00Z. High pressure over the Plains will build eastward through the day, and the pressure gradient will eventually slacken enough for winds to diminish below advisory criteria...most likely by 21Z. Highs on Wednesday will be cooler in the mid 40s to around 50, but the wind chill will definitely make it feel much cooler...more like the low to mid 30s in most locations...at least until the wind drops off in the mid to late afternoon. A ridge stacked through the depth of the troposphere will build across the Mississippi Valley on Wednesday night ahead of the next trough. The ridge continues drifting east through Thanksgiving Day, and the flow will eventually turn back to the southwest as the ridge axis moves east of the forecast area and the western U.S. trough becomes the dominant weather feature. The GFS is a bit faster with this process than the ECMWF or NAM, and it has the 850mb wind swinging around over central and southeast Missouri as early as 15Z Thursday morning. This produces weak to moderate moisture convergence at 850mb between 15-18Z and about 0.01 inch of QPF. Most of the GEFS QPF plumes are flat don`t start to angle upward until between 15-18Z, and then only slightly. Feel pretty confident at this point that if there is any wintry precipitation in the morning, it`ll be very light and is likely to have no impact to travel. As the moisture deepens in the afternoon, expect light rain to overspread much of the area. Clouds and precipitation will likely limit highs to the upper 30s and low 40s. Continuing low level warm advection will produce periods of rain Thursday night through Saturday morning. Temperatures will warm up a few degrees on Friday, but it`ll still be chilly since the surface wind stays out of the east or southeast through Friday afternoon with highs only in the mid to upper 40s. A substantial piece of the trough over the western U.S. breaks off and ejects northeast overnight Friday night. The surface reflection of the closed upper low moves from the Great Plains into the Midwest Saturday. The ECMWF and GFS diverge on the speed with which the low moves east, with the GFS being about 6hrs faster than the EC. The GFS solution would push the cold front associated with this storm system through the area during the morning or early afternoon, while the ECMWF holds the front back until late afternoon and evening. The slower solution would produce a greater threat for thunderstorms on Saturday. Have opted not to add thunder to the forecast at this time and wait for better model agreement. Another shot of cold air rolls in behind the front Sunday and Monday. Lows drop into the upper 20s to mid 30s and highs struggle to reach the upper 30s and low 40s. There may be some snow showers on Sunday as the upper low tracks north of Missouri across Iowa and northern Illinois, but QPF on both the GFS and ECMWF are very light so little if any accumulation is expected at this time. Carney && .AVIATION... (For the 18z TAFs through 18z Wednesday Afternoon) Issued at 1144 AM CST Tue Nov 26 2019 Ceilings will rise this afternoon across all terminals as strong surface winds gusting into the low 20s, driven by a strong pressure gradient, enhances mixing. KCOU will increase to VFR conditions mid afternoon through the evening, while KUIN and the metro terminals will persist at IFR conditions into the evening hours. Thunderstorms and associated IFR conditions will move across the terminals this evening, reaching KCOU by 02Z, and moving to KUIN and the metro terminals between 04 and 05Z. Strong surface winds gusting up to 45 kts are expected with these storms at all terminals. In the wake of the thunderstorms sustained winds will hover in the mid 20s and gust up to the mid 40s Wednesday, prompting the Wind Advisory that is in effect for all terminals from midnight until 200 PM Wednesday. SPECIFICS FOR KSTL: Winds will be the primary threat associated with the thunderstorms that will be moving through the metro area between 05 and 07Z tomorrow, however there is an isolated risk of tornadoes with these storms as well.
MRM
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.PRELIMINARY POINT TEMPS/POPS...
Saint Louis 61 40 48 32 / 50 70 0 0
Quincy 56 36 42 29 / 60 70 0 0
Columbia 61 36 45 30 / 5 70 0 0
Jefferson City 63 38 46 31 / 5 70 0 0
Salem 59 42 48 31 / 90 90 0 0
Farmington 60 40 49 31 / 90 80 0 0
&& .LSX
WATCHES/WARNINGS/ADVISORIES... MO...Wind Advisory from midnight tonight to 3 PM CST Wednesday for Crawford MO-Franklin MO-Iron MO-Jefferson MO-Madison MO- Reynolds MO-Saint Charles MO-Saint Francois MO-Saint Louis City MO-Saint Louis MO-Sainte Genevieve MO-Warren MO- Washington MO.
High Wind Warning from midnight tonight to 3 PM CST Wednesday for Audrain MO-Boone MO-Callaway MO-Cole MO-Gasconade MO- Knox MO-Lewis MO-Lincoln MO-Marion MO-Moniteau MO-Monroe MO- Montgomery MO-Osage MO-Pike MO-Ralls MO-Shelby MO. IL...Wind Advisory from midnight tonight to 3 PM CST Wednesday for Bond IL-Clinton IL-Fayette IL-Madison IL-Marion IL-Monroe IL-Randolph IL-Saint Clair IL-Washington IL.
High Wind Warning from midnight tonight to 3 PM CST Wednesday for Adams IL-Brown IL-Calhoun IL-Greene IL-Jersey IL- Macoupin IL-Montgomery IL-Pike IL.
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WFO
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