Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/26/18

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
638 PM EDT Tue Sep 25 2018 .AVIATION... A moist and weakly unstable environment lies across Se Mi, preceding a cold front now over the western Great Lakes. Multiple convergence areas ahead of the front will pose the risk for thunderstorms prior to frontal passage, which will not occur until 05-09z tonight. Ample low level moisture will also support continued intervals of MVFR (perhaps some IFR) cigs and showers. The passage of the front will end the risk of additional thunderstorms late tonight. Post frontal cold air advection will boost westerly wind gusts (20 knots or greater at times). A gradual lifting of the post frontal inversion due to cold air advection will also result in a slow but steady lifting of the strato cu during the course of Wed morning, like VFR by early afternoon. For DTW...An expansion of a mid cloud deck and embedded showers have worked into metro Detroit, which may be enough to hold off the threat for thunderstorms an hour or two after TAF issuance. The cold front will advance across metro between 09Z and 10Z, veering the winds to the west. There will at least be a chance of thunderstorms at anytime prior to fropa. .DTW THRESHOLD PROBABILITIES... * High for ceiling aob 5000 ft tonight and Wednesday morning. Moderate Wednesday afternoon. * Moderate confidence that thunderstorms will occur through the night but low confidence on timing/coverage. * Low confidence that westerly winds will exceed crosswind thresholds Wednesday morning. && .PREV DISCUSSION... Issued at 403 PM EDT Tue Sep 25 2018 DISCUSSION... Severe weather potential for late afternoon through tonight remains the primary focus for the afternoon forecast package. The overall scenario continues to be strongly conditional on adequate recovery of instability which remains possible but with low confidence. The bottom line is that hourly monitoring of instability trends will be required to continually assess severe weather potential or the lack thereof. That being said, instability is about the only element missing as large scale support and a strong wind field otherwise are more than adequate to support and/or sustain organized convection. Showers and ordinary thunderstorms that moved in from Indiana and NW Ohio continue to fade during mid afternoon while cloud debris further inhibits daytime heating over SE Michigan. This sets up target areas for new development over SW Lower Michigan moving eastward from the lee of Lake Michigan, and over Illinois and western Indiana moving toward the Ohio border region of SE Michigan later in the evening. Expect this would be more discrete convection occuring ahead of the surviving portion of the Iowa MCS that would approach SE Michigan shortly after midnight if adequate downstream instability can be maintained. Mid afternoon hourly mesoanalysis indicates MLCAPE rising slowly from values mostly less than 1000 J/kg across the mid Mississippi Valley into Lower Michigan. This is expected to reach the 1000-1500 J/kg range during the 21-00Z time period as a corridor of steeper mid level lapse rates moves into Lower Michigan from the Midwest. RAP projections indicate 700-500 mb lapse rates in the 7.0-7.5 C/km range along the leading edge of height falls ahead of the advancing upper level trough. The associated cooling aloft could be enough to maintain MLCAPE near 1500 J/kg well into the night along and shortly ahead of the cold front and should be considered the target range to hold for severe potential. It also suggests an advective component of instability into SE Michigan is possible which would be required for new storm development and to maintain storms moving into our area from the west. Other than concerns for instability trends, discrete convection that is able to develop ahead of the Midwest MCS will be within a strong wind profile having both some low level curvature and some mid level length. RAP and NAM sounding projections advertise 0-3 km SRH exceeding 150 m2/s2 and 0-6 km bulk shear exceeding 40 knots, 0-1 km helicity also exceeds 100 m2/s2 with 0-3 km CAPE exceeding 150 J/kg with cloud base on the low side of 3000 ft. These are all thresholds for supercell characteristics and for tornadogenesis, even in low topped convection. This again is strongly conditional on development of adequate instability, which is in doubt, but combined with the other elements of the storm environment remains worthy of the slight risk outlook. Tornado and small hail potential would be secondary to damaging wind if the upstream MCS can hold together. The cold front with this system exits quickly around sunrise Wednesday followed by dry and cooler mid week conditions leading into the extended period characterized by periodic shortwaves ushering in transient shots of cooler temps and attendant opportunities for showers. This will occur within a slowly retrograding background state most evident by the motion of the 591dm high centered near Florida this Friday potentially migrating toward western Texas after Day 7, a scenario that would offer a better opportunity for sustained longwave troughing locally. In the meantime, a steady stream of Pacific energy will keep heights at bay over the Great Lakes as this evolution unfolds. Chance of rain accompanying Friday`s fropa will be followed by highs at least 10 degrees below normal for the weekend. A brief warmup will then be tempered by another chance for rain under similar circumstances early next week. MARINE... A cold front will track through the region tonight which will prompt a notable change in conditions over the lakes. Currently, southerly winds are ushering in a warm and moist airmass which will result in scattered showers and thunderstorms into the overnight. Winds will quickly flip around to the northwest late tonight while strengthening as colder air filters in behind the front. The strongest winds remain across the northern Lake Huron basin where gusts will reach around 30 knots Wednesday morning into the afternoon hours. Though a few gusts to gale force are possible, it`s appears to be over a very short window so we will continue to hold off on any gale headlines. These elevated northerly winds will build wave heights along a portion of the Lake Huron shoreline prompting a small craft advisory. Northwest winds diminish late Wednesday and Wednesday night as high pressure builds into the region. Winds become southwesterly and strengthen again Thursday in advance of the next cold front. HYDROLOGY... Potential exists for scattered showers and thunderstorms this evening into tonight ahead of a cold front that will sweep through the region early Wednesday morning. Rainfall totals will average around one third of an inch, although any thunderstorm activity could bring very localized higher amounts. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...Small Craft Advisory from 6 AM to 4 PM EDT Wednesday for LHZ421-441. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....SC DISCUSSION...BT/JVC MARINE.......DRK HYDROLOGY....DRK You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Quad Cities IA IL
926 PM CDT Tue Sep 25 2018 .UPDATE... Issued at 924 PM CDT Tue Sep 25 2018 Elevated post frontal showers have developed across Missouri and are now reaching into northeast Missouri. Most of the activity should remain south of the area. However, I would not be surprised if some showers get into Hancock and McDonough counties later tonight and have added pops there. Updated forecast to be available shortly. && .SYNOPSIS... Issued at 1135 AM CDT Tue Sep 25 2018 Strong cold front was bisecting the state of Iowa late this morning. Temperatures across the area ranged from the upper 70s to low 80s across the southeast to the lower 60s to upper 50s across the northwest. Showers and thunderstorms were located across Iowa. Some of these storms could be severe with damaging winds, hail and tornadoes all possible threats. Update at 10AM this morning continues to have the current thought for this afternoon`s event. As a result, have attached it here for brevity. Severe Potential: Looks as though elevated convection will begin to overtake the warm sector and become rooted in the BL. This should occur shortly before noon and likely just west of the CWA. Overall convection speed will slow down and begin to move into our area. This will give time for CAPE to build this afternoon across the CWA. Synoptic models show that shear doesn`t support tornadogenesis, due to SW sfc winds. It appears that a sfc wave is forming across SW IA. This wave will back winds, much like the HRRR shows. I believe that we will have a tornado threat from any mesovortex that develops. I also believe that shear will be greater than what synoptic models forecast due to this low. As far as severe parameters go, tend to favor CAM solutions related to shear. Severe threat for winds to 70 mph, hail and tornadoes remains for the area. && .SHORT TERM...(This Afternoon through Tonight) ISSUED AT 1135 AM CDT Tue Sep 25 2018 Showers and storms will be exiting the area at the beginning of the period. It appears that the overall severe risk will be waning after 00z across the area. Main forecast concern for the overnight period will be how low to go with temperatures as strong CAA brings cool air into the area. Currently, most of the area will see lows in the 50s to the upper 40s. .LONG TERM...(Wednesday through Monday) ISSUED AT 150 PM CDT Tue Sep 25 2018 Dry conditions will be seen through Friday morning, as high pressure builds into the mid and lower MS River valley. Cool and breezy NW winds will be expected Wednesday, with highs struggling into the low to mid 60s. A chilly night with light winds will allow temperatures to fall into the low to mid 40s. Warmer temperatures are expected Thursday as the high departs and gusty southwest return flow sets up. Highs are slated to be in the mid 60s to lower 70s Thu. From Friday through Tuesday, there is some uncertainty in models. In short, there are slight to chance PoPs, mainly rain showery type, through most of the day4 through day7 period focused on a meandering boundary across the region. A re-enforcing cold front will sweep through Friday with highs in the upper 50s and 60s. Even colder temps are expected Saturday with highs in the mid 50s to low 60s. Saturday may end up being mostly dry with a surface high building in. A warm front and low pressure system lifts across the area Monday, with highs in the 70s to near 80 along with some chance/likely thunderstorm chances mainly over the northern part of the CWA. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening) ISSUED AT 625 PM CDT Tue Sep 25 2018 Strong cold front just east of the Mississippi will move into the Ohio Valley overnight. Behind the front IFR/MVFR conditions be seen through 06z/26 with scattered SHRA. After 06z/26 conditions will improve to VFR as high pressure builds into the Midwest. && .HYDROLOGY... Issued at 1022 AM CDT Tue Sep 25 2018 Not much change to river forecasts. The Cedar River at Vinton has crested with Cedar Rapids expected to crest this evening near 17.5 feet. On the Wapsipinicon River near De Witt Major flooding is expected to begin tomorrow, with a crest expected Friday night into Saturday. Moderate flooding is still forecast for the Cedar River at Conesville and the Iowa River at Marengo, Columbus Junction, Wapello, and Oakville. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ UPDATE...08 SYNOPSIS...Gibbs SHORT TERM...Gibbs LONG TERM...Sheets AVIATION...08 HYDROLOGY...14
Area Forecast Discussion
National Weather Service Green Bay WI
1055 PM CDT Tue Sep 25 2018 Updated aviation portion for 06Z TAF issuance .SHORT TERM...Tonight and Wednesday Issued at 241 PM CDT Tue Sep 25 2018 The latest RAP analysis and satellite/radar imagery show a cold front extending from around Marinette to Wautoma early this afternoon. Partial clearing over northeast WI has allowed some instability to develop up to the 600-1000 j/kg range. Meanwhile, a shortwave trough over Minnesota, and associated surface low over Iowa continue to push an area of showers and storms to the northeast and across southwest Wisconsin. This area of precipitation remains on track to pass over the area from mid- afternoon through the evening. Given the instability over east- central WI, concern remains for a few strong storms to develop, mainly from about 21-00z time period. The main threat will likely be strong, gusty winds from any storms. Tonight...Cold front, and weak surface low, will be departing over central Lake Michigan at the start of the period. Although the potential for strong storms will likely have passed on to the east by 00z, deformation showers and a few embedded storms are expected to continue across the region through the evening before exiting northeast WI shortly after midnight. Partial clearing is possible overnight, mainly over central and east- central WI, but additional cloud cover from a trailing shortwave will approach late. With gusty northwest winds developing behind the front, lows will fall back into the 40s at most locations. Wednesday...Upper troughing will be moving across the region. Progged soundings indicate the thermal profile will be supportive of an ample cu field developing at locations that clear overnight. With a breezy west wind and scattered to broken cloud cover, temps will range from the mid 50s north to low 60s south. .LONG TERM...Wednesday Night Through Tuesday Issued at 241 PM CDT Tue Sep 25 2018 Another cold front is forecast to arrive late Wednesday night into Thursday, along with the next chance of showers. Models show little instability with this system, so will hold off on any mention of thunder at this time. Drier weather is anticipated Thursday night, but a short-wave trof and secondary cold front could bring scattered showers on Friday. Canadian high pressure is expected to be the dominant weather feature over the weekend, and the 00z ECMWF would suggest that the high would keep mainly dry conditions in place through Sunday morning. The GFS is dry Friday night into Saturday, but quickly shifts the Canadian high east on Saturday night, allowing showers to develop due to increasing WAA/isentropic lift. An unseasonably cool air mass will arrive Friday night, with 850 mb temperatures dropping to -5 to -6 C over north central WI by Saturday morning. Will need to keep an eye on Friday night and Saturday night, as forecast lows are cold enough to be concerned about frost potential. However, sky cover and wind will play a significant role in whether or not frost forms, and it is too far out to ascertain those details. A significant isentropic lift/overrunning event is possible across the forecast area from Sunday night into Monday night. There may be enough elevated instability to support thunderstorm development, especially over the south half of the forecast area. This is shaping up as a potentially very wet period. Temperatures should be near normal on Thursday, drop below normal over the weekend, then recover to near normal early in the work week. && .AVIATION...for 06Z TAF Issuance Issued at 1055 PM CDT Tue Sep 25 2018 As the cold front continues to shift off to the east of the area, winds will remain out of the west and northwest through the rest of the night into Wednesday. The winds could gust to the 15 to 20 knot range tonight and again Wednesday afternoon. Lower clouds will linger through late tonight before lifting overnight into Wednesday morning. GRB, ATW and MTW may lift a bit earlier with the downsloping winds into those sites. As cooler air linger aloft Wednesday afternoon, could easily see some afternoon CU giving a broken MVFR ceiling. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM.....MPC LONG TERM......Kieckbusch AVIATION.......Cooley
Area Forecast Discussion
National Weather Service Huntsville AL
852 PM CDT Tue Sep 25 2018 .NEAR TERM...(Tonight) Issued at 852 PM CDT Tue Sep 25 2018 The line of storms has moved off into NE AL and portions of southern middle TN. Radar, lightning observations and GLM data all suggest a few stronger storms continue to be embedded in this line. With precipitable water values of 2+inches over the area these storms have been producing very high rainfall rates between 2-4 inches per hour. Thankfully, wind flow through the atmosphere has kept these moving and the flash flood threat down. Some brief wind gusts of 30 to 40 mph are possible as the storms shift into GA and E TN. We`ll likely see a break in activity through about 3 or 4 AM. Then, a weak wave moving north up the MS River Valley will combine with a frontal boundary shifting E/SE out of the plains to generate another round of showers and storms. Hires guidance has been handling these features pretty well and also have a good handle on current radar trends. The HRRR brings the batch of showers currently over the ArkLaMiss into NW AL a little after midnight. So in terms of PoPs over the next several hours, we initially have a decreasing trend as the current line exits east. Then around midnight start to raise PoPs back up out west and spread these higher values eastward through sunrise. With the little bit of clearing before the next round of rain arrives temps may be able to cool a few more degrees. Lows around 70 degrees seem reasonable for much of the area. .SHORT TERM...(Wednesday through Thursday) Issued at 245 PM CDT Tue Sep 25 2018 The front should continue to drift swd starting Wed, and gradually make its way into the area later in the day. Abundant moisture flow ahead of the front coupled with an increase in synoptic forcing should allow for num/widespread showers/tstms to develop along/ahead of the advancing boundary. With unseasonably high PWAT`s xpcted to remain near/just above 2 inches, multiple episodes of heavy rainfall are possible with these showers/tstms. A Flash Flood Watch may be required for Wed/Wed night and perhaps into Thu. With the front xpcted to remain invof the gen area, total rainfall amounts look to be right around 2-2.5 inches, with locally higher amounts certainly possible. Areas east of I-65 into NE AL will have the highest prob of any localized/flash flooding Wed into Thu. Latest model suites are then fairly consistent with moving the boundary south of the area later in the day Thu, with a somewhat weakening trend. This will translate into rainfall gradually tapering off from the west during the day Thu. Rain chances look to remain fairly high across the ern zones thru Thu, although total rainfall amounts will be on a diminishing trend. Given the abundant cloud cover/rainfall in the area, afternoon highs Wed/Thu may struggle to climb any higher than the mid/upper 70s range. Lows Wed night look to fall more into the mid/upper 60s given the influx of some cooler air. .LONG TERM...(Thursday night through Monday) Issued at 245 PM CDT Tue Sep 25 2018 Rainfall will continue to be on a gradual diminishing trend near the end of the work week, with the front perhaps just south of the area and continuing to weaken. This may at least allow afternoon temps on Fri to climb more into the lower 80s for most spots. The wx across the region will then be dependent on another frontal boundary approaching from the NW this weekend. However, the latest global models are not clear on this boundary moving into the area as with the front Wed. As such, rain chances will mainly be iso/sct in nature starting this weekend, with much of this activity dependent on the strength of the moisture return back into the region. Highs look to rebound more into the lower/mid 80s for much of the period, while lows trend predom in the mid 60s. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 624 PM CDT Tue Sep 25 2018 A line of showers and storms at the HSV terminal as of 23z but should be east by 01z. Brief drop to MVFR cigs/vis possible with these storms. Some clearing is noted in satellite behind the storms and cigs should improve to VFR. Then late tonight into early Wednesday a frontal boundary is forecast to approach the area. Scattered to numerous showers/storms are forecast after 12z Wednesday. IFR cigs/vis are possible under the heavier activity during the day Wednesday. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...Stumpf SHORT TERM...09 LONG TERM...09 AVIATION...Stumpf For more information please visit our website at
Area Forecast Discussion
National Weather Service Lincoln IL
855 PM CDT Tue Sep 25 2018 .UPDATE... Issued at 855 PM CDT Tue Sep 25 2018 0130z/830pm surface analysis shows cold front just east of the I-55 corridor...with a broken line of convection just ahead of the boundary from near Rantoul S/SW to Taylorville. These storms will continue to progress eastward over the next couple of hours, eventually exiting into Indiana by around midnight. Behind the front, breezy and much cooler conditions are spilling into the western KILX CWA where temperatures have already dropped into the lower to middle 60s. HRRR continues to suggest a line of post- frontal showers will develop from Missouri into portions of central Illinois later this evening into the overnight hours. Latest radar mosaic is showing these showers already materializing across central and western Missouri, so will be keeping a close eye on radar trends to see how far N/NE these showers will expand. Have updated hourly PoPs to focus likely showers/thunder across east-central Illinois through midnight, then have added chance PoPs for showers along/south of a Paris line overnight. && .SHORT TERM...(This evening through Wednesday) ISSUED AT 330 PM CDT Tue Sep 25 2018 Severe Thunderstorm Watch is ongoing across the northern third of the CWA late this afternoon and is set to continue til 10 pm. The strongest storms are north of the CWA but additional showers and storms will continue to develop across portions of central IL along I-72 and move northeast. Will keep highest pops to the north through the evening hours and then have pops getting lower as moving to the southeast and south. Based on HiRes models and other models, back edge of the precip should move through rather quickly this evening with precip ending across most areas around midnight and then in the east and southeast late tonight. Once the precip moves through tonight dry weather is expected on Wednesday. As the front moves through tonight winds will become northwesterly and this should usher in cooler temps for tonight. Overnight lows are expected to drop into the upper 40s in the northwest to around 60 in the southeast. Most areas will see temps of around 50 mid 50s. Wed temps will be much cooler tomorrow with northwest flow...with 60s possible across the CWA. .LONG TERM...(Wednesday night through Tuesday) ISSUED AT 330 PM CDT Tue Sep 25 2018 The extended period will predominately be dry as a northwest flow pattern takes over the area for the rest of the week and then more zonal during the weekend. Any precip chances will remain north of the CWA the rest of the week and into the weekend as weak waves move through the flow and across the Great Lakes region. However, small chances of precip will be seen across the extreme northern tier of the CWA through the period. The pattern begins to slowly change to more southwest/zonal for the beginning of next week and this results in the models differing with timing and position of precip across the CWA. A blend of the models brings precip chances for Mon night and Tue and this seems fine for now. Temps will vary through the period with 70s expected Thur and Fri, 60s for Sat, 70s again for Sun, and then 80s for Mon and Tue. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 724 PM CDT Tue Sep 25 2018 Line of broken showers and isolated storms will continue to move through the area with only thunder seen on radar/satellite near BMI. Will keep VCSH at all other sites and VCTS at BMI...all for a few hours. Then clouds will become MVFR at around 2.5kft on back side of the front. These clouds are expected to hang around until morning...then clear out during the morning hours. Winds will become northwest behind the front. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Barnes SHORT TERM...Auten LONG TERM...Auten AVIATION...Auten
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
840 PM CDT Tue Sep 25 2018 .UPDATE... Issued at 840 PM CDT Tue Sep 25 2018 At 8pm, the surface cold front extended from just east of Springfield, IL (KSPI) to southern Lincoln County Missouri to near Jefferson City, MO (KJEF). Surprisingly very little convection has developed along this front in our forecast area from earlier and the front is currently precipitation-free. Examination of soundings showed a bit stronger mid level cap that led to much of the frontal scale forcing being suppressed. A slight chance token PoP will be retained until 06z as this cold front continues to push southeast through our region. Of a more important forecast change is the HRRR/RAP have really picked up on post-frontal development of showers with isolated thunderstorms currently over western Missouri due to frontogenetical forcing (welcome to the COOL season!) and broadscale forcing aloft. Have decided to run with this depiction for overnight PoPs, which places many areas in likely category. Instability will be quite limited when this does enter our forecast area late this evening and have showers going instead. These showers are expected to exit the forecast area to the east by mid-morning Wednesday. Otherwise, the rest of the forecast is on track with only minor cosmetic changes made. TES && .SHORT TERM... (Through Late Wednesday Afternoon) Issued at 330 PM CDT Tue Sep 25 2018 Isolated showers and a lone thunderstorm have developed over the area this afternoon. Am surprised there hasn`t been more lighting as of yet given the 1500-2000 J/Kg MLCAPE on indicated by SPC Mesoanalysis over eastern Missouri and southern Illinois. RAP soundings are showing some low level CAPE with a mid level wedge of warmer air around 10,000 feet. While the soundings are uncapped by the warm mid levels, it`s possible the RAP is a little too cool aloft and updrafts aren`t able to punch up high enough to cause glaciation and lightning production. I expect that between the instability and the approaching shortwave the convection should eventually be able to grow tall enough to produce lightning later this afternoon. 0-6km shear is in the 40-50kt range, with the higher end of those values over northeast Missouri and west central Illinois. With the aforementioned MLCAPE values and shear, will have to remain vigilant through the early evening for severe thunderstorms. The greatest potential should be over northeast Missouri and west central Illinois where the highest shear and CAPE values are superimposed. CAMS have been too strong/too widespread with convection so far this I can`t say I have a lot of faith in them for the evening. That being said, the operational HRRR seems to finally be figuring out that there may not be as much convection this afternoon and evening as originally thought, so am leaning toward it for guidance on coverage tonight. Instability drops off very quickly behind the cold front tonight which should pass from central into east central Missouri between 00- 04Z, and from there through our southeast Missouri and south central Illinois counties by 07-08Z according to the RAP. This should put an end to the threat for thunderstorms, but short-range models are showing some moderate low-mid level frontogenesis behind the front into early Wednesday morning. Will keep low chance/slight chance PoPs in the forecast behind the front tonight, ending from northwest to southeast through 12Z Wednesday to cover this. This looks like a nice strong cold front, with temperatures dropping 20 degrees or more in the cold sector. Expect lows Wednesday to be 15-20 degrees below this morning`s readings in the upper 40s to mid 50s, and highs similarly around 15 degrees cooler in the upper 60s to low 70s. Carney .LONG TERM... (Wednesday Night through Next Tuesday) Issued at 330 PM CDT Tue Sep 25 2018 By early Wed night, the ridge axis of a broad surface high pressure center will stretch from southwest to northeast across the region. Looking aloft, one PV anomaly is forecast to remain in TX/OK near the base of an upper trough axis while a much stronger one sinks southward into ND/MN and eventually develops into a low pressure system. The surface ridge axis will be nearly overhead for most of the night, but mid/high cloudiness associated with the TX/OK disturbance will interfere with what would otherwise be good radiational cooling conditions. Overnight lows are forecast to fall into the mid-40s to low/mid-50s across the area with the coldest temperatures in the northwestern CWA where the least cloudiness is expected. This will likely be the coolest night out of the next several, especially if less cloud cover occurs and leads to better radiational cooling conditions. The aforementioned strong PV anomaly over ND/MN continues moving southeastward into the western Great Lakes on Thu/Thu night and develops into a low pressure system before lifting northeastward into Canada. This low pressure system will send a cold front into MO/IL on Friday, but the upper forcing across our area appears limited due to the distance from the surface and upper lows. Any rain showers associated with this front would be limited to the northern CWA and likely sparse to widely scattered in coverage. Models then depict a 1025+ hPa surface high settling into the region behind this front which will ensure quiet and mostly dry conditions over the weekend. Models diverge late this weekend regarding their handling of a closed upper low which approaches the northern California coast. Despite the timing and evolution differences, models are in vague agreement that lee cyclogenesis associated with this system produces a developing surface low near the Rockies which lifts the effective frontal boundary northeastward through the CWA on Sunday/Monday. The combination of the warm frontal passage and rising heights aloft downstream of the upper trough will lead to warming temperatures for Sunday through next Tuesday. Moisture convergence associated with a low-level jet could produce isolated to scattered SHRA/TSRA early next week. Kanofsky && .AVIATION... (For the 00z TAFs through 00z Wednesday Evening) Issued at 655 PM CDT Tue Sep 25 2018 Showers and thunderstorms are struggling to develop along a cold front now just east of UIN and COU. This is looking less likely to directly impact the STL metro TAF sites during the evening. Another interesting development from some model guidance is development of an area of showers behind the front that could affect all TAF sites during the late evening and overnight hours. Will be evaluating this soon and updating rain chances as needed. Look for a period of MVFR ceilings behind the cold frontal passage this evening, otherwise, VFR conditions will prevail at the TAF sites through the valid period. Light SW surface winds will veer NW and become gusty to 20-25kts behind the front, diminishing some during Wednesday. SPECIFICS FOR KSTL: Kept a token VCTS mention for now through 03z although it is looking less likely with time. Otherwise, the cold front is set to move through around 03z followed by surface winds veering NW and becoming gusty with several hours of MVFR ceilings as well. We are looking into the potential for another better round of showers overnight between 07-11z and may need to upgrade to prevailing or TEMPO as needed. Otherwise, VFR conditions will settle in by sunrise Wednesday and continue through the remainder of the valid period. TES && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Nashville TN
755 PM CDT Tue Sep 25 2018 .UPDATE... FOR EVENING DISCUSSION. && .DISCUSSION... Lower level convergence zone appears to be working slowly across eastern middle TN at this time. Rainfall rates of up to an inch per hour are falling along the central Plateau. Movement is rather slow to the east. Will go ahead and increase pops for areas along that central Plateau. Otw, the western two thirds of the mid state is experiencing a break right now. But looking up stream, a cold front stretches from IL southwest through eastern OK. Pressure rises are indicated in the post frontal sector, so the front is on the way. Currently, vort advection is neutral over our western two thirds. Later tonight, curvature and shear spikes will become more n-s oriented. This will enhance a positive tilt in regard to the vort advection fields. As the developing pva aligns with the frontal and pre frontal forcing, convection coverage will pick up later tonight. At 12z, frontal position progs are such that the boundary will be working through our northwestern counties. Latest HRRR data shows the marked precip covg increase holding off until aft 09z. Will adjust weather and pop grids accordingly. Remainder of the grids appear to be in good shape. Update out shortly. && .AVIATION... 00Z TAF DISCUSSION. CKV/BNA/MQY/CSV...Expecting only some VCSH potentially for CKV/BNA/MQY thru 26/08Z. As sfc front approaches mid state after 26/06Z and then sags slowly sewd into cntrl portions of mid state by 26/18Z, another round of shwrs/tstms is likely to occur. As sfc front is expected to push well southeast of mid state region by 26/24Z, look for some drier air to work into at least northwestern parts of mid state region. However, with a continuance of southwesterly flow aloft anticipated, look for the potential of shwrs to hang around all terminals expect CKV thru 26/24Z. Current VFR ceilings will degrade to generally low end MVFR/IFR ceilings. CKV may see a return to VFR ceilings by 26/21Z. SW sfc winds will veer slowly to the NW as sfc front progresses thru the mid state region. && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION......21 AVIATION........31
Area Forecast Discussion
National Weather Service New York NY
1035 PM EDT Tue Sep 25 2018 .SYNOPSIS... A warm front will slowly move north of the area tonight, followed by a cold front Wednesday and Wednesday night. High pressure returns on Thursday and then builds to the north on Friday as a wave of low pressure passes to the south. A stronger high pressure builds from the west over the weekend and then offshore early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Significant flash flooding continues across New Haven, Middlesex, and New London Counties in CT. Once the heavy rain band moves to the east in the next hour or two, the flash flooding threat will diminish. However, it will take some time for the water to recede as rainfall amounts have been quite impressive. Several locations in SE CT have reported over 6 inches of rain in a relatively short amount of time. A Public Information Statement has been issued listing some rainfall totals so far with this event. There will be a more limited threat for heavy downpours after midnight. PoPs will be decreased accordingly, but with a continued moist southerly flow and warm front nearby, PoPs will still remain in the chance range. Will need to watch the early morning hours as the HRRR and 3-km NAM show some regeneration of heavy rain, mainly along Long Island and SE CT. Winds should remain high enough at the coast to keep fog from becoming widespread tonight. Inland areas north of the warm front may see fog become more widespread and possibly dense. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Areas of fog during the early morning hours will dissipate as heating and mixing commences. Scattered showered in the morning will become more widespread as the day progresses with a pre- frontal trough developing and followed by a cold front during the eve. Moderate instability and 30-40kt of 0-6km bulk shear has warranted SPC to place the entire area in a slight risk for severe weather on Wed. The main threat is damaging winds. Heavy rain will once again be a concern although the storms should be moving and the upper pattern does not appear to be conducive for training storms. However, urban and small stream flooding cannot be ruled out. Showers/tstms end from W to E Wed night with dry weather returning behind it. There is a high rip current risk for the Atlantic beaches Wednesday. && .LONG TERM /THURSDAY THROUGH TUESDAY/... The synoptic pattern through the long term will be characterized by a large, mean trough over the northern CONUS. The upper trough may flatten later this weekend and lift back into Canada early next week as ridging rebuilds over the east. High pressure will briefly build over the region on Thursday and then lift to our north on Friday. The cold front that moves across late Wednesday into Wednesday night stalls to our south. A broad SW flow aloft and some shortwave energy may interact with this front and develop a wave of low pressure along it Thursday night. This wave likely passes to our south and east on Friday. Have continued to keep PoPs in the slight to low chance range. Thinking the surface high will continue to ridge down into the region preventing much in the way of precipitation. The low moves offshore late Friday into Friday night with a stronger high building into the region for the rest of the weekend. This high will likely move offshore early next week with the approach of the next frontal system. Temperatures should average near normal through the long term period with highs in the upper 60s and lower 70s and nighttime temperatures mainly in the lower and middle 50s. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... Warm front will clear nrn portions of the area by 12-14z. A cold front passes Wed eve. Rain tapers off thru 5-6z from w to e. Heaviest shwrs invof KGON. Cigs still expected to lower to ifr all areas overnight, with some brief breaks to vfr thru 4-6z. Winds will continue to diminish this tngt. Light and variable winds likely across the Lower Hudson Valley. S-SW winds of 10 to 15 kt expected on Wed, becoming nw behind the cold front Wed ngt. .OUTLOOK FOR 00Z THURSDAY THROUGH SUNDAY... .Wednesday night...Showers/tstms with MVFR or lower at times, mainly in the evening. .Thursday...VFR. .Thursday night-Friday morning...MVFR possible, low chance of showers. .Friday afternoon-Sunday...VFR. && .MARINE... SCA remains in effect through 1am for the Eastern Sound and Eastern LI Bays. Winds will continue to diminish there and should be below 25 kt around or just after midnight. Gusts on the ocean waters have diminished below 25 kt, although seas will remain above 5 ft through Wed night. Winds are likely to remain below SCA levels Thursday through the weekend on all area waters. Ocean seas on Thursday into Thursday night will remain elevated above 5 ft, but then should remain 3-4 ft from Friday into the weekend. && .HYDROLOGY... The potential for significant flash flooding remains for the next few hours across southeastern Connecticut. Additional rainfall amounts of 2 to 3 inches with locally higher amounts cannot be ruled out in the heaviest band of showers across New London County. Outside of the heaviest band of showers, rainfall amounts will be significantly less. Scattered tstms Wed/Wed eve have the potential to produce heavy rainfall however urban and small stream flooding appears to be the potential threat at this point. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...High Rip Current Risk through Wednesday evening for NYZ075-080- 081-178-179. NJ...None. MARINE...Small Craft Advisory until 1 AM EDT Wednesday for ANZ330-340. Small Craft Advisory until 6 AM EDT Thursday for ANZ350-353- 355. && $$ SYNOPSIS...24/DS NEAR TERM...24/DS SHORT TERM...24 LONG TERM...DS AVIATION...JMC MARINE...24/DS HYDROLOGY...24/DS EQUIPMENT...
Area Forecast Discussion
National Weather Service Paducah KY
853 PM CDT Tue Sep 25 2018 .UPDATE... Issued at 851 PM CDT Tue Sep 25 2018 Performed a second iteration of PoPs/Weather/Sky/QPF adjustments for the rest of tonight. Surface/low level moisture convergence remains weak and the lack of deep layer moisture and instability inhibiting deep convection this evening. The HRRR and RAP guidance appear to have consistent signals regarding convective development overnight. Some slight spatial adjustments were made to the model output to reflect current rainfall trends this evening and overnight. Plan to remove mention of damaging winds associated with convection in the Hazardous Weather Outlook. The best potential for any wind damage concerns would be isolated to wind gusts associated with the cold frontal passage late tonight impacting trees or other weakened structures in areas with saturated ground the past couple of days. UPDATE Issued at 616 PM CDT Tue Sep 25 2018 Aviation update. See section below for the public forecast update. UPDATE Issued at 602 PM CDT Tue Sep 25 2018 Made some significant short term adjustments to PoPs/Weather/QPF for the WFO PAH forecast area this evening and overnight. At this point, could not justify keeping 40-50% PoPs in the forecast for the next few hours. From a surface based perspective, there is some decent theta-e convergence and up to 2700 j/kg LAPS surface based CAPE over southeast Illinois and southwest Indiana in ahead of the convection in southeast Illinois, but this area has been worked over fairly well, so temperatures for surface lift and renewed convection are marginal. Elsewhere, theta-e convergence is weak and there is lower dewpoints advecting into southeast Missouri. Will not rule out pockets of scattered showers and isolated to scattered thunderstorms in advance of the cold front tonight. Until more organized lift and forcing can be in place, cannot rationalize widespread coverage of chance POPs at least through the midnight hour. Will make adjustments as the front gets closer to the WFO PAH forecast area. The HRRR/ESRL HRRR convection allowing models (CAM`s) have shown quite a bit of consistency since yesterday evening on the progression of the convective, heavy rain producing, band today and the widely scattered convection this evening. && .SHORT TERM...(Tonight through Thursday night) Issued at 114 PM CDT Tue Sep 25 2018 Warm front that has pivoted northeast of FA has allowed warm conveyor belt of high theta-e air to train across southeast IL/southwest IN with efficient rains. Embedded elevated instability resulting in occasional thunderstorms has heightened the locally heavy rain risk, which continues this pm. Afterwards, we`ll be warm sectored, and watching pm destabilization in the west. Marginal risk day1 svr still exists for our north/west. Cold fropa entering nrn MO at this writing, and we`ll see height falls/speed shear aloft increasing in difluent upper flow as front approaches. However, it won`t be reaching PAH FA/making passage til later tonight, when surface destabilization wanes. Anticipate showers/some continuing risk of thunder, with main impact gusty frontal shift winds/maybe locally heavy rains. Fropa brings Fall like change to airmass, with dew points still poised to drop thru the 50s Wednesday, and upper 40s to invade the entirety of the FA by 12z Thursday. This will be our first true taste of Fall. .LONG TERM...(Friday through Tuesday) Issued at 221 PM CDT Tue Sep 25 2018 Models are in fairly good agreement showing a surface high over the upper Mississippi valley Friday night, then centering it over the southern Great lakes region by 00z Sunday. The overall trend of a slower moving high results in a slower warm up for the weekend, with winds remaining easterly into Saturday night and becoming southerly on Sunday. Temperatures will now remain below seasonal normals through Saturday, moderating back to seasonal values by Sunday. A frontal boundary situated to our north early in the work week and increasing low level moisture due to our southerly winds will give us a gradual increase in shower and thunderstorm chances Monday into Tuesday. Our slight to low chances on Monday will be primarily diurnally driven, then chances will increase late Monday night into Tuesday as the boundary sinks a little farther south. Our early week temperatures will be few degrees above normal, with readings in the lower 80s, and dew points will climb into the upper 60s to around 70 degrees. && .AVIATION... Issued at 616 PM CDT Tue Sep 25 2018 Front will push southeast across the area overnight. SSW winds up to 10 kts ahead of it, NW winds becoming N, with some gusts 18 to 22 kts or so expected behind the front. Around 09z the front should be along a KEVV- KPAH line, clearing west KY by 12z. Scattered showers and a few storms possible up to fropa, but chance too low to include in the terminals. There may be a period of MVFR cigs along and behind the front for a few hours. Otherwise expect mainly VFR conditions ahead of the front, and from mid morning Wednesday on into the afternoon hours. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$ UPDATE...Smith
...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Wednesday) Issued at 308 PM CDT Tue Sep 25 2018 As of 18Z Tuesday afternoon a neutrally tilted, midlevel trough was positioned across the northern Plains with broad cyclonic flow across the central Plains. An attendant surface trough extended from eastern WI through northeast KS into west TX. Scattered thunderstorms have developed within the last hour across northern MO/southern IA where better midlevel moisture and forcing for ascent reside. Scattered showers and storms are possible across northeast KS through the afternoon and early evening. RAP and HRRR forecast soundings suggest upwards of 2,000 J/kg of MLCAPE will reside across east-central KS by mid to late afternoon, along with 40-50 kts of effective shear. This combination could pose a damaging wind and hail threat. Additional elevated thunderstorms are possible behind the surface trough as sufficient residual low level moisture will reside for upwards of 1,000 MUCAPE to reside across northeast KS. Sufficient effective shear values will remain greater than 30 kts, which could support a large hail potential into the early evening hours. As the main midlevel trough moves east and the surface trough exits the area to the southeast, all shower and thunderstorm activity will come to an end from northwest to southeast early this evening. Gusty northerly winds between 20 and 30 MPH will decrease after sunset to below 10 MPH. Cold air advection combined with plentiful radiational cooling due to clear skies should yield a cool start to Wednesday morning with lows in the mid to upper 40s. A pleasant Wednesday is expected as the surface ridge axis moves overhead, yielding sunny skies and light winds. High temperatures are progged to remain in the upper 60s to near 70. .LONG TERM...(Wednesday night through Tuesday) Issued at 308 PM CDT Tue Sep 25 2018 PV anomaly diving south-southeast along the northern Rockies helps reinforce the surface ridge over the southern Plains Wednesday night into Thursday keeps the lower troposphere dry despite a return of southerly winds. Modest warm air advection should bring highs back into the mid 70s for most areas Thursday. The next upper wave rotating southeast through the mean trough brings another Canadian cold front through the area Thursday night and Friday with precipitation chances low with precipitable water values remaining below normal. Best chances again look to be in northeastern areas closer to the deeper forcing with the upper wave. Chances do increase Friday night into Saturday with isentropic upglide developing over the front as mid/upper flow becomes more zonal. Differences on the post-frontal anticyclone`s intensity give rise to varying solutions on precipitation potential but any amounts look to be light. Confidence in temperatures for these periods is not high with timing differences on the front Friday, persistence and depth of cloud cover, and cloud/precip potential Saturday. The mean upper trough shifts east early next week though confidence in the pattern in the western U.S. in specifics in the timing and location of waves there is not high. West to southwest upper flow over the central and northern Plains should bring predominantly southerly winds and above normal temps in place. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 633 PM CDT Tue Sep 25 2018 For the 00z TAFs, VFR conditions are expected with diminishing winds and gradually scattering cloud cover this evening. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Baerg LONG TERM...65 AVIATION...Hennecke