Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/16/17


Area Forecast Discussion
National Weather Service La Crosse WI
635 PM CDT Fri Sep 15 2017 .SYNOPSIS... Issued at 130 PM CDT Fri Sep 15 2017 GOES water vapor imagery this afternoon showing an impressive mid- level cyclonic circulation lifting from WY toward the Dakotas. This was producing surface cyclogenesis over the Central Plains with increasing moisture transport ahead of this low into our area. RAP analysis has axis of 850mb moisture transport extending from eastern KS northward into western MN. Have been watching an area of showers and isolated thunderstorms lifting slowly northeast toward our forecast area in northeast IA/southeast MN on the eastern periphery of this moisture transport. Believe the bulk of this activity will stay just west of the area through the remainder of this afternoon/early evening. Otherwise, temperatures as of 2pm this afternoon were in the 80s. && .SHORT TERM...(This evening through Saturday) Issued at 130 PM CDT Fri Sep 15 2017 Going into tonight...low pressure will lift northeast across western MN, drawing the surface cold front a bit further east into central MN through northwest IA. Main axis of moisture transport/fuel for convection looks to remain just west of our area but will likley see isolated to scattered showers/storms nudge into western portions of the forecast area (mainly northwest of a line from Charles City Ia to Medford WI). This area will be on the very eastern fringes of this better moisture transport. Otherwise, look for a rather muggy overnight with lows in the middle/upper 60s with dew points in the lower 60s. The cold front oozes ever so slowly eastward toward the area on Saturday, extending from northwest WI through south central MN by late in the afternoon. This keeps bulk of showers/storms west of the area through the day with continued warm air advection across our area. 925mb temperatures in the 23-25C range in the afternoon, so should see unseasonably warm highs again in the 80s, coolest over the northwest where more cloud cover is expected. .LONG TERM...(Saturday night through Friday) Issued at 130 PM CDT Fri Sep 15 2017 Vigorous mid-level trough rotating northeast into the easter Dakotas.northwest MN drives the surface cold front across our area Saturday evening/overnight. CAPE will be waning going into the nighttime hours and Bulk Shear is mostly post-frontal, so severe threat looks minimal at this time. However, cannot rule out a few stronger storms with small hail and gusty winds. After some lingering morning shower chances, drier/cooler air will filter into the area Sunday. Look for mostly sunny skies by afternoon with highs in the upper 60 to the middle 70s, which is right around seasonal normals. High pressure shifting off to the east already by Sunday night as a mid-level trough ejects out of the Central Plains toward our area. This will produce a chance of showers west of the Mississippi River after midnight. For next week...southwest flow aloft will keep the area in occasional shower/thunderstorm chances as several mid-level disturbances eject out of the main trough out west into our area. Otherwise, temperatures are expected to be slightly above normal through this period with highs in the middle/upper 70s and lows in the middle 50s/lower 60s. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 635 PM CDT Fri Sep 15 2017 Quiet weather conditions are set to continue into the evening hours for all areas, with just some passing cirrus as low level wind shear becomes the biggest issue from about 03Z onward for all areas. Another push of moisture into the area (similar to last night) should result in developing mid level clouds and likely at least scattered showers and thunderstorms late tonight, particularly near and west of the RST terminal. Given uncertainty in coverage/placement, will stick with a vicinity mention at this point and continue to watch trends. There is a very low end chance that a shower or storm gets closer to LSE as well through mid morning, though that risk is quite low per current forecast trends. Otherwise, surface winds should again become gusty into the midday and afternoon hours on Saturday, with any lingering morning showers/storms ending and ceilings dissipating. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SYNOPSIS...DAS SHORT TERM...DAS LONG TERM...DAS AVIATION...Lawrence
Area Forecast Discussion
National Weather Service Cheyenne WY
551 PM MDT Fri Sep 15 2017 .SHORT TERM...(This evening through Sunday night) Issued at 245 PM MDT Fri Sep 15 2017 Just a few showers noted so far this afternoon over parts of the CWA as the area is likely seeing some subsidence behind a departing shortwave ejecting north over the northern high plains. Another wave over Utah should bring another round of mainly showers to the CWA this evening, with some snow possible over the highest peaks. Little accumulation expected however. Pcpn should end Saturday morning with the passage of the main upper trough. A cold front will move across the CWA this evening with mins falling into the 40s over much of the CWA, with some 30s over western valleys. Saturday will feature mild temperatures across the CWA with some fairly breezy winds out west in the afternoon as decent westerly mid level flow mixes down. The winds will drop off in the evening with clearing skies setting up a chilly night Saturday night. Mins could get close to or even a bit below freezing in low lying areas such as Alliance and western valley locations Sunday morning. Return flow during the day Sunday will allow warmer temperatures over the plains as upper flow backs to southwesterly. .LONG TERM...(Monday through Friday) Issued at 245 PM MDT Fri Sep 15 2017 Looking at a rather active week weather-wise, especially from Tuesday onward. Southwest flow aloft will provide dry and warm conditions to start the work week. A vigorous upper level jet will carve out a fairly deep trough from the northern Rockies to the southern Great Basin Tuesday. A Pacific cold front will surge southeast across the CWA Tuesday night, accompanied by scattered showers. Instability for thunder will be marginal at best. High temperatures Wednesday will be 10 degrees cooler compared to Tuesday. The upper trough lifts northeast into the northern Great Plains and upper Midwest later Wednesday, with the next upper jet maxima and trough tracking east then northeast across the CWA Wednesday night and Thursday with scattered showers. Highest elevations west of the Laramie Range may see some snow, but no significant accumulations are expected. The third in a series of upper troughs will be deeper as it tracks across the Intermountain West Friday. Shortwave energy in deepening south-southwest flow will trigger more shower activity at that time. High temperatures by the end of next week will trend near to below seasonal normals. Most days will be breezy, mainly along and west of the Laramie Range. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 550 PM MDT Fri Sep 15 2017 More widespread IFR conditions expected tonight across the Nebraska Panhandle and east of the Laramie Range. Should start earlier too with recent rainfall and upsloping winds already ongoing. Generally followed HRRR guidance on timing/locations of IFR onset. && .FIRE WEATHER... Issued at 245 PM MDT Fri Sep 15 2017 A cold front will move across the districts this evening with showers and possibly a thunderstorm or two behind the front. Wetting rains look to be rather isolated though. A little snow is even possible over the highest mountain peaks overnight. Mild and mainly dry weather is then expected Saturday and Sunday with some breezy afternoon winds over western areas. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...RE LONG TERM...MAJ AVIATION...GCC FIRE WEATHER...RE
Area Forecast Discussion
National Weather Service Des Moines IA
649 PM CDT Fri Sep 15 2017 ...Updated Aviation Discussion... .SHORT TERM.../Tonight through Saturday/ Issued at 338 PM CDT Fri Sep 15 2017 Tonight...A low and associated deep upper trough will begin to pivot northeast. This will drive a shortwave across the region tonight and push an elongated surface low and associated cold front into northeast MN and southeast NE. Ahead of this boundary will be a wave of theta-e advection and some weak to moderate lift. This should be sufficient to have showers and storms. However, instability is only modest and shear is negligible so the better storms will remain west of the forecast area tonight with showers/isolated storms expected to dribble across the area. The HRRR handled things today the best and leaned towards that model for tonight though all models point to only weak showers/convection tonight. The NAM is the most bullish and mainly across the west. I`ve gone with that main thinking but tempered pops/qpf to be more in line with the HRRR. Saturday...The aforementioned cold front will slowly make it`s way across the state Saturday into Sunday. By 00Z Sunday the front should only be through about the Western third of the state. The best forcing and shear lag the front somewhat and there is some uncertainty as to what the morning showers and cloud cover will do to the instability so overall, not expecting much during the day but may see showers with isolated storms. By afternoon...especially late afternoon into Saturday night, we should see enough sun and destabilize enough that storms should develop along/behind the frontal boundary, some of which could be strong to severe. Shear is mostly unidirectional so large hail with maybe some damaging wind would be the threat going into the evening. Strongest storms should hold off til the evening but west of highway 169 would be of concern late in the day. .LONG TERM.../Saturday night through Friday/ Issued at 338 PM CDT Fri Sep 15 2017 Increased kinematic forcing into Saturday evening should help any afternoon convection to increase along the boundary across western into central Iowa. Sufficient shear exists for some organization and a convective line is likely to develop by early evening. Some severe weather will occur in the evening with main threats from damaging winds and large hail. The convection will spread quickly southeast overnight as surface front moves through the state with relatively dry and cooler conditions for much of Sunday. However, upper flow will persist from the southwest and a return to warm advection is expected by Sunday night along with increasing low level moisture transport. Elevated convection is expected to spread northward into the state overnight into Monday morning with best threat in central and southern areas. Thereafter, warm sector will spread northward into the state as large western trof develops. As this trof deepens and matures, a surface boundary is expected to move into the state toward the middle of next week. Both Euro and GFS indicate a period of active weather with periods of thunderstorms and the possibility of heavy rainfall. Temperatures will remain generally at or above normal with southerly flow into the state for much of the week. && .AVIATION.../For the 00Z TAFS through 00Z Saturday evening/ Issued at 643 PM CDT Fri Sep 15 2017 Expecting VFR conditions throughout the TAF period. The main concern is with storm potential over northern Iowa and possibly impacting MCW and FOD. Certainly VCTS seems viable for MCW and FOD towards Saturday morning, but low confidence in mentioning any MVFR visibility due to the coverage and duration of the convection. Winds continue to mix through the evening hours tonight before subsiding somewhat overnight. However, they increase again late Saturday morning into the afternoon as a deep trough advances towards the state. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...FAB LONG TERM...Cogil AVIATION...Podrazik
Area Forecast Discussion
National Weather Service Quad Cities IA IL
553 PM CDT Fri Sep 15 2017 ...00Z AVIATION UPDATE... .SYNOPSIS... Issued at 250 PM CDT Fri Sep 15 2017 18z surface data has low pressure over central Nebraska and high pressure over the Ohio Valley. A front ran northeast from the low into eastern Lake Superior. Dew points were mainly in the 60s across the Midwest with some 50s across eastern Iowa. && .SHORT TERM...(This Evening through Saturday) ISSUED AT 250 PM CDT Fri Sep 15 2017 Very warm and dry conditions will be seen through sunset. After sunset the dry conditions will continue through midnight. Attention then turns to the late night time frame. After midnight, the RAP model has a layer of unstable air aloft, that, when combined with some weak forcing and moisture generates some elevated convection. This situation occurred last night and resulted in showers and a few thunderstorms. So, based on this persistent signal from the RAP, slight chance to low chance pops have been introduced for areas west of a Manchester, IA to Williamsburg, IA line. The rain from the elevated convection will fall through a dry layer that is around 10 kft deep. So, while the nocturnal convection may look impressive on radar, the amount of rain at the surface may just barely wet the pavement. The nocturnal convection that develops late tonight will dissipate around mid morning Saturday. Once the clouds break up, very warm conditions will be seen across the area with high temperatures ranging from the mid 80s to the lower 90s. Dew points will drop during the day but heat index readings are still expected to be in the upper 80s to lower 90s. Refer to the climate section for record highs for September 16th. .LONG TERM...(Saturday Night through Friday) ISSUED AT 250 PM CDT Fri Sep 15 2017 Long term forecast highlights are unseasonably warm temps through next week, along with potential for some relief from the recent dry spell. A well-advertised cold front will finally arrive Saturday night into Sunday. Highest rain coverage is favored along/west of the Mississippi River. Areal averages should be less than 1/4 inch, with isolated pockets of heavier rain with isolated storms. This will not provide much relief for the drought conditions across southeast Iowa. Weak deep layer shear and forcing should preclude any organized severe weather threat. Clouds and a south breeze will keep lows Saturday night well above normal, mainly in the 60s. Sunday, expect scattered showers and a few storms to linger as the front pushes south of the area. A cooler and drier air mass will overspread the area, with afternoon highs in the mid 70s to around 80. Early next week, there is more favorable model consensus regarding the arrival of another short wave trough embedded in southwest flow, along with a warm front across the forecast area. This scenario could yield some more widespread significant rain Monday and/or Monday night, although confidence in details remains low. Looking ahead, expect highs warming into the 80s Tuesday/Wednesday. The ECMWF and GFS are both advertising more rain for Wednesday. Temps will remain above normal through Friday, with additional late week chances of showers and thunderstorms. Model blend pops indicate at least some potential for rain every period. This is overdone, but no period can be reliably ruled out at this point. && .AVIATION...(For the 00Z TAFS through 00Z Saturday Evening) ISSUED AT 544 PM CDT Fri Sep 15 2017 VFR conditions expected to persist through the TAF cycle. Several convective allowing models continue to suggest the potential for elevated SHRA and possibly an isolated TSRA moving into eastern IA late tonight until mid morning Saturday while weakening. KCID still appears to have best potential of being impacted by a SHRA or TSRA that may result in brief period of MVFR conditions (visibility), but given anticipated weakening trend have maintained VCSH wording at KCID and also at KDBQ toward 12z through 16z. Otherwise, expect periods of mid and high clouds with winds backing to SE at 4-8 kts tonight then veering to SSW on Saturday at 10-20 kts. && .CLIMATE... ISSUED AT 250 PM CDT Fri Sep 15 2017 Record Highs for September 16... Moline.........92 in 1931 Cedar Rapids...98 in 1931 Dubuque........96 in 1931 Burlington.....95 in 1906 && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ SYNOPSIS...08 SHORT TERM...08 LONG TERM...RP Kinney AVIATION...McClure CLIMATE...08
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1014 PM CDT Fri Sep 15 2017 .UPDATE... Quick update to add some slight chance PoPs to far northwestern Val Verde County due to shower activity on the KDFX radar. Based on the HRRR this activity should stay confined to areas just north and west of our area, but a brief shower could work into Val Verde County over the next one to two hours. Otherwise, the rest of the forecast is on track with increasing clouds overnight and patchy fog by morning. && .PREV DISCUSSION... /ISSUED 649 PM CDT Fri Sep 15 2017/ AVIATION.../00Z TAFS/ Will maintain a near persistence forecast with I-35 sites seeing low cloudiness return around midnight and some spotty ifr cigs by around 10Z. Afternoon and early evening pressure gradients look to tighten up from mixing of stronger winds aloft with decoupling late at night expected to yield the ifr conditions. The gradient holds tighter over DRT so will keep their cigs as mvfr and short-lived in the late morning hours. A few showers are suggested to be in the picture near DRT by rapid refresh models. Will wait for the 06z update to consider introducing any impacts as they should be minor. PREV DISCUSSION... /ISSUED 248 PM CDT Fri Sep 15 2017/ SHORT TERM (Tonight through Saturday Night)... Upper air analysis this morning showed a shallow trough over the Gulf of Mexico with a low amplitude ridge over West Texas. The flow over South Texas was northwesterly. At the surface, high pressure was centered to our east and winds were from the south to southeast. There was a trough over West Texas producing convection. This activity will stay north of our CWA as it dissipates this evening. The upper level ridge will become dominant during this period. The low level flow will remain south to southeasterly, so we don`t expect much change in the weather. Continuing flow from the Gulf will bring high temperatures down a couple of degrees Saturday. Patchy will form again overnight along and southeast of I-35. A spots could have visibility as low as a half mile. LONG TERM (Sunday through Friday)... The upper level ridge will move to the southwest into the middle of next week. In response, upper flow will become more zonal by Tuesday. During this transition, a short wave trough will move across Central Texas and bring a chance for showers and thunderstorms Monday and Tuesday across the eastern half of the CWA. Tuesday night into Wednesday an upper trough will dig down across New Mexico and pick up the remnants of Tropical Storm Norma from the Pacific. This will bring another chance for rain Wednesday and Thursday across all of South Central Texas. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 92 72 92 71 91 / 0 0 - 0 10 Austin Bergstrom Intl Airport 92 71 91 69 91 / 0 0 - 0 10 New Braunfels Muni Airport 92 71 93 70 91 / 0 - - 0 10 Burnet Muni Airport 92 70 91 69 90 / 0 0 0 0 - Del Rio Intl Airport 100 73 96 73 95 / 0 0 0 0 - Georgetown Muni Airport 90 71 91 69 90 / 0 0 0 0 10 Hondo Muni Airport 98 70 96 70 94 / 0 0 0 0 10 San Marcos Muni Airport 92 71 92 69 90 / 0 0 10 0 10 La Grange - Fayette Regional 93 71 91 70 91 / 0 0 10 - 20 San Antonio Intl Airport 92 72 93 71 91 / 0 - 0 0 10 Stinson Muni Airport 95 72 93 72 92 / 0 0 0 0 10 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Mesoscale/Aviation...Oaks Synoptic/Grids...Treadway Public Service/Data Collection...30
Area Forecast Discussion
National Weather Service North Platte NE
713 PM CDT Fri Sep 15 2017 .SYNOPSIS... Issued at 311 PM CDT Fri Sep 15 2017 Well defined lead PV anomaly moving northeast across eastern WY on downstream side of long wave trough located over the western US. Ahead of this feature strong LLJ and low level warm air advection creating a large area of mid level instability across eastern NE into SD/MN. Within this environment SHRA and TSRA developed as a result of forcing of a northward advancing warm front last night and through the morning. Further west, more widespread rain and even snow in the higher elevations across parts of MT/WY supported by fairly substantial cold conveyor belt across southern Canada combined with warm conveyor belt originating from the aforementioned LLJ and warm advection pattern through the Dakotas and turning westward and wrapping into the low. Second and more substantial PV anomaly dropping southward on backside of upper low over eastern WA/OR into NV/UT. && .SHORT TERM...(This evening through Saturday) Issued at 311 PM CDT Fri Sep 15 2017 Previously mentioned PV anomaly will rotate through the upper low across the central Rockies today. Downslope winds will drive/create a dryline surge across northeast CO and western KS and into southwest/central NE this afternoon. Surface low will continue to pull northeast into western MN and weaken as it stays anchored to broader area of weakening warm air advection. Associated subsidence behind exiting short wave to be in place across western NE into the afternoon. Slight precip chances near the SD border late this afternoon but large scale subsidence should keep most of the area dry through late afternoon. As PV anomaly moves off the Rockies it will cause a surface low to develop in northeastern CO and allow a cold front to drop south into the Panhandle this evening. Upper height falls then rotate into the western Dakotas late afternoon and evening and low level winds respond resulting in convergence along the front across northeastern NE and to some degree along the dryline in central NE by evening. RAP soundings suggest inverted-V profiles in low levels west of this line, suggesting dry air below a shallow moist layer in the mid levels. This profile exists to some degree in eastern north central NE in the form of an elevated mixed layer and therefore allows some CAPE/instability to be available above low level forcing and should set the stage for thunderstorm development if parcels can make it above low level stable layer. Short range models differ on this occurring, but if it does there will be decent potential for enough instability to produce updrafts capable of supporting marginal large hail, hence the area of marginal risk for severe storms as presented by SPC. Further west, weaker elevated instability moves into the NE Panhandle this evening. Next area of height falls associated with next PV anomaly rotating through main upper trough will allow mid level southerly winds to increase across the west creating a new warm conveyor belt and developing an area of strong frontogenetic forcing in this weakly unstable environment in the Panhandle. More widespread showers and a few thunderstorms will develop as a result of the strong mid level forcing, moving east across north central NE overnight. Though some instability is presented in RAP soundings in this area it likely won`t be enough to support large hail. Good confidence in the occurrence of SHRA/TSRA here however as this sequence of events is supported by most models. For saturday some lingering showers and maybe a rumble of thunder or two will be across north central NE. But otherwise expect a lot of cloud cover behind the front and much cooler temps. Upper low pulls northeast into the Dakotas and although some weak forcing with remain across north central NE this will lessen through the day. .LONG TERM...(Saturday night through Friday) Issued at 311 PM CDT Fri Sep 15 2017 An active weather pattern will be taking shape the next several days as a large upper trough becomes established across the Pacific northwest. This trough will slowly move east into the central and northern plains by the end of next week. Ahead of this large trough, a weak disturbance will quickly move east across the area Sunday into Sunday night. Will include some chance pops for precipitation with this. Appears enough instability to include thunder. As the upper trough slowly moves east next week, isolated to scattered showers and thunderstorms will be possible by midweek as southwest flow aloft becomes established on the eastern periphery of the approaching trough. Will keep pops conservative as quite a bit of model differences at this point. After a cool weekend, it will begin to warm up again ahead of the upper trough early next week. It appears highs in the upper 70s and 80s will return through much of next week. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 711 PM CDT Fri Sep 15 2017 Clouds will increase with MVFR CIGS likely by late evening. Ceilings will range from 1000 to 1500 FT AGL. Look for skies to gradually clear Saturday afternoon. Light showers will be possible at the KVTN terminal tonight. Will handle this with a vcsh group given the expected sparse coverage of showers. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Stoppkotte SHORT TERM...Stoppkotte LONG TERM...Taylor AVIATION...Buttler
Area Forecast Discussion
National Weather Service Marquette MI
816 PM EDT Fri Sep 15 2017 .SHORT TERM...(This evening through Saturday) Issued at 403 PM EDT FRI SEP 15 2017 Another day with the stalled front and trough across the area. Main impacts are thunderstorms, with an outside chance of a stronger storm, far west over the next 2-3 hours, moderate swim risk through this evening for Schoolcraft County, high swim risk for Schoolcraft County Sat, dense fog potential across the Keweenaw tonight, and possibly some strong to severe storms over the W on Sat. . Thunderstorms have formed over NW WI, far W U.P. and far W Lake Superior as a weak shortwave lifts through. CAPE values up to 1,000 J/kg over the west with weak shear may result in a stronger storm or two, but think chances of that are small. HRRR and RAP are also showing some precip breaking out over the NCentral as the shortwave passes, which is possible given the lake breeze there as an additional focusing mechanism. Have slight chance PoPs over the NCentral. Ahead of an upper wave and the SFC low riding up the front, precip may skirt the western U.P. Sat, with greater chances for precip as the wave/low approaches later in the day. Some of the storms could be strong to severe given potential for up to 2,000 J/kg of cape and effective shear values of 20-30kts. Large hail and damaging winds the primary threat. Dense fog is possibly over the Keweenaw tonight with E winds off the Lake. Not confident enough to issue any headlines though. With large waves along the beaches of Schoolcraft County, the mod swim risk will continue into this evening, with larger waves and a high swim risk on Sat. The night shift will issue the headline if needed. .LONG TERM...(Saturday night through Friday) Issued at 348 PM EDT FRI SEP 15 2017 Guidance continues to hold onto the dominant upper level ridge across the eastern CONUS through the weekend; however, there continues to be some nudging to the east which could bring the upstream trough further east towards the Upper Peninsula. Will continue to bring steady increases of precip and possibly thunder. With a low pressure system lifting north of the forecast area Sun, guidance indicates a frontal boundary will precede a surface ridge of high pressure late in the weekend into early next week. This will then allow dry weather to return. The pattern does start to become more active with a quasi-zonal orientation from Tue-Thur of next week. This will bring periodic chances for showers and possibly thunder, but also with more seasonal temps. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 806 PM EDT FRI SEP 15 2017 LLWS at all sites tonight. Expect showers to generally hold off to the west through much of the period. At KCMX, LIFR to VLIFR conditions in CIGS and fog are expected into early overnight with eastern flow off the lake and plenty of upstream low level moisture. Conditions should improve late tonight to VFR as winds shift to a downslope southeast direction. At KSAW, moist southeast upslope flow could lead to some patchy fog/stratus late tonight but uncertainty is such that kept VFR conditions thru the period. At KIWD, moist northeast flow off Lake Superior will lead to LIFR stratus clouds early this evening but once winds shift southeast later this evening expect improvement to VFR. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 403 PM EDT FRI SEP 15 2017 An inverted surface trough currently anchored across Lake Superior will begin to weaken tonight. NE winds to 20 to 30 knots may occasionally gust to 35 knots into early tonight before weakening. Winds will then increase on Sunday out of the W gusting to 20-30 knots. Otherwise, winds will be below 25 knots.. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Titus LONG TERM...Beachler AVIATION...Voss MARINE...Titus
Area Forecast Discussion
National Weather Service Topeka KS
610 PM CDT Fri Sep 15 2017 ...AVIATION UPDATE... .SHORT TERM...(This evening through Saturday) Issued at 336 PM CDT Fri Sep 15 2017 The early afternoon water vapor satellite imagery featured a deep longwave trough positioned over the inter-mountain west with multiple subtle perturbations rotating around its base and ejecting to the northeast. One such wave helped prolong an area of showers and isolated thunderstorms across central Kansas. Despite a 10 kft deep wedge of dry air below cloud base, precip managed to reach the ground thanks to the added kinematic lift associated with the departing shortwave. At the surface, an elongated 1002 mb surface low was located near the the Siouxland region with a trailing cold front stretching southwestward and into far NW Kansas. NE Kansas was located in the warm sector ahead of this front, but clouds from the daytime precip resulted in a complex thermal field in the early afternoon analysis. Over the next 24 hours, the upper level longwave will pivot ENE into the western Dakotas as a 90 kt jet streak wraps around the base of the trough. This will help push the cold front southeastward during the day tomorrow, approaching Concordia by the mid to late afternoon. Aside from a slight chance of showers and storms with the nocturnal LLJ early tomorrow morning, the next best chance for storms will be along and ahead boundary tomorrow afternoon. MLCAPE values will likely exceed 3000 J/kg due to steepening mid-level lapse rates and ample surface heating ahead of the boundary. However, the best jet dynamics and deep shear look to stay north of the CWA. Thus, the best threat for stronger storms will be in the incipient stages of any convection, with large hail and localized damaging winds the main threats. This is in agreement with the SPC Day 2 marginal outlook. .LONG TERM...(Saturday night through Friday) Issued at 336 PM CDT Fri Sep 15 2017 Front continues southeast through the area Saturday night, through not terribly fast with upper flow nearly parallel to it. Should still be enough forcing and moisture for decent coverage despite some capping remaining with a few near-severe storms possible until ML CAPE diminishes in the late evening. Not seeing any obvious signs of a persistent training situation but some locations could see locally heavy amounts. Expect decreasing coverage with time late in the night into midday Sunday with chances increasing again Sunday night into Monday as isentropic upglide develops through the column and the southern branch jet comes into Oklahoma for added ascent in its left-front quadrant. Not much focus in the ascent noted at this time though still high-chance to likely PoPs are warranted and elevated CAPE increasing to around 1000 J/kg could produce some small hail. Will need to watch how much the warm sector moderates Monday afternoon with the potential for a decent shear/ML CAPE combination and suggestions of low level convergence remaining. Low- level jet increase Monday night for another chance for elevated storms. Western CONUS upper trough deepens into the midweek as multiple waves rotate through it. Current operational models are fairly consistent with another Pacific cold front passing through Tuesday night and Wednesday though, though southwest flow in the mid levels could bring a decent cap in. Have kept chances limited at this point. Somewhat better precip chances come late in the forecast with the upper trough pushing a bit farther east. As for temperatures, Sunday still looks the coolest of the week with highs perhaps not breaking the mid 70s in some locations. Highs return to the 80s for the remainder of the week. && .AVIATION...(For the 00Z TAFS through 00Z Sunday) Issued at 610 PM CDT Fri Sep 15 2017 Mid level warm air advection continues over the area, although I`m not sure how much moisture advection is occurring with mid level moisture already in place. Forecast soundings hint at some brief saturation overnight implying some elevated storms could develop. But with the RAP and HRRR showing isolated precip at best, think including a VCTS may be a little to aggressive at this point. As for LLWS, forecast soundings maintain good mixing of the boundary layer through the night with a very shallow inversion at best. LLWS remains a concern with a 40KT+ low level jet and will keep a mention of it for TOP where there is a better chance for surface winds to back more to the southeast. However at MHK and FOE think there is a better chance for surface winds to remain gusty through a good portion of the night as models maintain a good surface pressure gradient over the area. In general VFR conditions should prevail into Saturday with a FROPA and chances for TS anticipated just beyond the forecast period. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Skow LONG TERM...65 AVIATION...Wolters