Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/11/19

Area Forecast Discussion
National Weather Service Hastings NE
853 PM CDT Tue Sep 10 2019 .UPDATE... Issued at 853 PM CDT Tue Sep 10 2019 Some comments regarding mainly thunderstorm chances rest of tonight: The short version: Not to make too big of a deal out of (currently) only 20 percent chances, but in short, have "flip-flopped" any small chances for storms tonight in our northern zones from PRE-midnight to POST- midnight. By "northern zones" we are generally talking near/north of the Highway 92 corridor, as the forecast for the rest of our coverage area (CWA) remains dry as before. More details: It`s been an almost eerily-quiet evening thus far within our coverage area CWA, although this was largely expected. As expected, a fairly expansive cluster of strong to severe thunderstorms has blossomed to our north-northwest within north central/northwest Nebraska along the main warm frontal zone. In addition, more subtle forcing sparked a few rogue storms both to our southwest (northwest KS) and southeast (northeast KS), although this southern activity has since largely faded with the setting sun. Based on reliable-looking short term models (namely HRRR) and radar trends, it`s become increasingly-obvious that our northern zones will likely get through at least midnight storm- free. As a result, have pulled any formal mention of showers/storms before then. However, while the previous forecast was dry in our north for the post-midnight/late-night hours, have now introduced a small chance for this time frame, as especially the HRRR is suggesting that some convection could build down along a southward-oozing outflow boundary. Because this is a fairly low- confidence scenario for now, have only gone with 20 percent PoPs (slight chances) at this time, but the overnight shift will have to keep an eye on this. Fortunately, am not thinking that any late night storms that MIGHT invade our north would be severe, but some gusty winds/small hail cannot be ruled out. For now have not extended any of these slight Pops beyond 12Z/7AM, but this will also be something to watch in case any activity "leaks" into the Wed daytime forecast period. Of lesser consequence, a few final notes about the overnight forecast: 1) Based largely on trends observed trends from last night (and given stronger/steadier southerly breezes most areas tonight), nudged up overnight lows 1-2 degrees in most areas, with the majority of the CWA expected to drop no lower than 69-73 degrees. 2) IF late-night outflow and possible storms do make it into our northern counties, then the wind field there will likely become considerably more easterly than southerly, with an easterly component perhaps lasting well into the daylight hours before a southerly wind becomes established again. This may not be well- captured in current forecast grids/products ,so outflow trends/influences will need monitored. && .SHORT TERM...(This evening through Wednesday) Issued at 345 PM CDT Tue Sep 10 2019 Upper air and satellite data show continued southwesterly flow in place across the region...set up between high pressure centered roughly over the TN/Carolinas region and low pressure/troughing affecting much of the west/NWrn CONUS. Outside of a weak thunderstorm that clipped far western Dawson County earlier this afternoon and some light precip moving into Jewell County, things have been dry across the CWA...with partly cloudy to mostly clear skies. At the surface, a warm front has been gradually working its way north with time, and currently sits draped across far northern portions of the CWA. To the south of the front, the rest of the CWA has continued breezy southerly winds, with gusts in the 20-25 MPH range. Hasn`t been any surprises with temperatures, 3PM obs range from the mid 80s to lower 90s. Overall, no significant changes were made to the forecast for tonight and into tomorrow...which for most locations remains dry. There is expected to be an increase in thunderstorm activity through the rest of this afternoon through tonight, but models remain in good agreement showing those best chances focusing to the north of the CWA. The sfc front continues to push north with time, and convergence along the nose of a 40-50 kt LLJ will keep most activity out of our area. It`s close enough that wasn`t comfortable no having any PoPs in the forecast, so do have 20% chances still across our north. More isolated/scattered activity will also be possible off to our west through tonight, but models are in pretty good agreement keeping it off to the west. Kept the daytime hours tomorrow dry, there is good agreement showing the better chances holding off after 00Z, as a stronger system swings through the Plains. May be a close call for those far WNWrn areas late in the afternoon. It`s looking to be another breezy day, with low pressure deepening over NErn portions of CO. The main frontal boundary spends the day off to the NW of the CWA, the resultant southerly winds look to be in the 20-25 MPH range, with gusts over 30 MPH. No big changes to forecast highs for tomorrow, which will again be in the mid 80s to lower 90s. .LONG TERM...(Wednesday night through Tuesday) Issued at 345 PM CDT Tue Sep 10 2019 At this point, the best chances for widespread precipitation for over the next week looks to come Wednesday night. The upper level system currently impacting the W/NW CONUS is shown by models to keep pushing east with time. By 12Z Wed, the trough has moved well into the Rockies, emerging onto the northern/central High Plains by 00Z...this timing helping keep the area dry during the daytime hours. Between 00Z-12Z Thur, models show a closed 500mb low developing over the MT/WY/ND/SD, with the southward extending trough axis swinging into the Central Plains. Thunderstorm activity is expected to push through the area with the surface cold front, and looks to clear all but eastern portions of the CWA by 12Z Thurs. Models continue to show the potential for strong/severe thunderstorms during this period, especially early- on across the western half of the CWA. Damaging winds/large hail would be the primary threats...heavy rain will also be possible, but activity should be pretty progressive in nature. Outside of some lingering activity during the morning on Thursday, the rest of the day...and most of the extended period dry. Models show the main upper level system continuing to make its way east, leaving more zonal flow in its wake through the weekend...turning more southwesterly once again for the start of next week. Forecast does have a couple low chances PoPs in there, late Friday night and again late Saturday night, but confidence in timing/location is not high. As far as temperatures go, highs drop back into the 70s on Thursday in the wake of the cold front...before warming back up into the 80s/low 90s for the latter portions of the extended period. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday) Issued at 703 PM CDT Tue Sep 10 2019 Confidence is very high in VFR ceiling/visibility through the period, with mainly only limited mid-high level clouds. Although the chance for a VERY random/isolated shower is not necessarily zero, it is far too low to justify TAF inclusion. By far the main story through the period will be breezy/gusty southerly winds (likely some of the strongest non-thunderstorm speeds observed around here in a few months), along with a period of low level wind shear (LLWS) this evening into Wednesday AM. Surface winds: A fairly consistent southerly direction will prevail, with sustained speeds averaging 12-16KT/gusts 18-22KT through most of the period. However, these speeds will kick up another notch for the latter hours of the period on Wednesday afternoon, commonly sustained around 20KT/gusting 25-30KT. LLWS: Despite surface winds remaining somewhat elevated, have maintained a mention of moderate LLWS for the entire 03-14Z time frame, as southerly winds within the lowest 1,500 ft. AGL will accelerate to around average around 45KT, resulting in generally 30-35KT of shear magnitude. && .GID WATCHES/WARNINGS/ADVISORIES... NE...None. KS...None. && $$ UPDATE...Pfannkuch SHORT TERM...ADP LONG TERM...ADP AVIATION...Pfannkuch
Area Forecast Discussion
National Weather Service Huntsville AL
831 PM CDT Tue Sep 10 2019 .NEAR TERM...(Tonight) Issued at 831 PM CDT Tue Sep 10 2019 While virtually the entire CWA is now rain-free, we have additional clusters of thunderstorms edging up against southeast DeKalb County from NW GA into Cherokee County. Unsure if these will enter our forecast area as the HRRR suggests over the next few hours. Thus, will leave a low PoP this evening in northeast AL. Otherwise, may have to introduce patchy fog as well given the very moist boundary layer conditions, especially for area that received rainfall this afternoon and early evening. .SHORT TERM...(Wednesday through Thursday) Issued at 230 PM CDT Tue Sep 10 2019 This weak convergence boundary moves north into Kentucky and Tennessee on Wednesday, so left out precipitation chances on Wednesday. Overall, high temperatures should remain in the mid 90s, with some afternoon cumulus development expected. However, it still looks very humid with afternoon dewpoints values remaining in the lower 70s primarily. So heat index values look to remain between 100 and 104 degrees. Could see a few 105 values, but not enough to warrant a heat advisory at this time. Not much change in the overnight conditions Wednesday night, with a humid airmass still in place and lows only drop into the upper 60s/lower 70s. Several models forecast the upper ridge to strengthen more right over the Tennessee Valley on Thursday. 925 mb temperatures also climb a bit higher to between 25 and 27 degrees again. Believe that a return to highs in the mid to upper 90s will be the result over northern Alabama. It looks as though enough mixing of drier air will occur to keep dewpoints a bit lower and keep heat index values between 100 and 104 degrees on Thursday. .LONG TERM...(Thursday night through Monday) Issued at 230 PM CDT Tue Sep 10 2019 Lows around 70 degrees are expected Thursday night. Friday looks very similar and may be a tad hotter but drier. Wouldn`t be surprised to see a 99 high or two. Again heat index values in the afternoon will be close to advisory criteria but likely still between 100 and 104. Friday night into the weekend, a frontal boundary and boundary ahead of it push southeast and into northern Alabama. How much moisture that ends up along the front is a bit uncertain, but kept a 20 to 30 percent pop in Friday night into Saturday. The cloud cover and any precipitation should keep highs a bit lower in the lower to mid 90s. Drier and cooler air is expected to move into the area behind the front Saturday night into Sunday. Lows in the mid 60s to lower 70s are expected. A return to a wetter pattern may occur next week, but models are very divergent. For now went with low scattered chances of showers and precipitation. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 628 PM CDT Tue Sep 10 2019 A few light showers will at least be in the vicinity of either terminal through 3Z to 5Z this evening. Broken high CIGS will give way to clear skies shortly after midnight. This and light winds should allow patchy fog to form tonight. For now dropping VSBYS into the MVFR realm after 09Z. Guidance shows KMSL dropping to 2SM (or possibly lower) between 10Z and 12Z. Will have to watch for the formation of denser fog at either terminal. VFR conditions should return by 15Z at both terminals and continue through the TAF period. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...17 SHORT TERM...KTW LONG TERM...KTW AVIATION...KTW For more information please visit our website at
National Weather Service Jackson KY
1016 PM EDT Tue Sep 10 2019 .UPDATE... Issued at 1010 PM EDT TUE SEP 10 2019 Hourly grids were freshened up based on recent observations and trends. The main changes were to hourly temperatures and dewpoint curves to better align with the observations. Some convection is still occurring in parts of Middle TN and the Cumberland Plateau of TN and in portions of central KY. As the night progresses this should continue to weaken and probably dissipate. Some guidance, such as recent RAP runs and 0Z HRRR and 01Z HRRR suggest a bit of convection is possible overnight developing over or near the west and north. Earlier HRRR runs did not have this and the RAP generally trended toward less activity from 21Z to 0Z runs. Given the presence of upper level ridging centered in the Appalachians and time of day would be limiting factors to this potential. A shortwave does appear to pass by to the northwest and GFS and NAM runs show some height falls overnight as well. At this time, we have continued with some 5 to 10 percent pops in the northern and western areas overnight to early on Wed as some convection cannot be completely ruled out during that time. This potential will continue to be monitored and if confidence in this were to increase, pops would be increased in those northern and western areas. UPDATE Issued at 815 PM EDT TUE SEP 10 2019 Diurnally driven convection that was occurring over our southwest counties has dissipated over the past couple of hours. Some convection is still ongoing over central KY and parts of Middle TN and the TN Cumberland Plateau. At this time, we expect that convection to dissipate as it attempts to move northeast as the atmosphere stabilizes as we are now past sunset. Temperatures remain warm, especially on the ridges and in more open terrain locations. However, several valley locations have dropped into the 70s bringing relief from today`s record warmth. No significant changes were needed at this time. && .SHORT TERM...(This evening through Wednesday night) Issued at 400 PM EDT TUE SEP 10 2019 19z sfc analysis shows high pressure in place through eastern Kentucky with strong ridging aloft. This kept the skies sunny and allowed for record highs throughout the area. In fact, with JKL hitting 97 degrees we have now set the highest temperature on record for September. Certainly portions of the area being in a drought that is worsening has contributed to this heat. Dewpoints, meanwhile, in the low to mid 60s, have kept heat indices from exceeding 100 degrees in too many places, but still it is quite hot, especially for this time of year. With nearly as hot temperatures expected through Friday will highlight the heat concerns in the forthcoming HWO. A stray shower/future thunderstorm is trying to develop near the Cumberland Plateau and could linger just across the border into McCreary or Whitley County. Winds are mostly light from the west to southwest with a few places seeing gusts up to 20 mph. The models remain in excellent agreement aloft through the short term portion of the forecast as they depict the 5h ridge peaking over the Tennessee Valley and Southern Appalachians. This will keep most of the energy off to the north and west of the area for the period, but some weakness in the height fields to the north of the area on Wednesday could affect Kentucky. Given the model agreement have again favored the NBM as the starting point for all the grids along with some consideration to the NAM12 PoP and QPF fields on Wednesday. Sensible weather will feature a warmer night than last, but still able to see a ridge to valley temperatures split to set up along with more river valley fog towards dawn. Likewise, similar conditions can be expected on Wednesday night. During the day - hot temperatures will again be the rule with low to mid 90s expected but more in the way of clouds and a potential for spotty showers or storms at peak heating should keep it from being a complete repeat of today. The scattered convection on Wednesday will not be a certainty but conditions appear favorable given some upper support and the fact that even some air mass thunderstorms are developing in the far south this afternoon. Did again adjust the temperatures from the NBM for spot highs on Wednesday and also to incorporate the expected ridge to valley differences each night. As for PoPs and QPF - did not adjust them much from the near 20 percent values and light QPF for Wednesday afternoon - more spread included. .LONG TERM...(Thursday through Tuesday) Issued at 315 PM EDT TUE SEP 10 2019 The trend of extremely warm weather will continue on through the end of the extended period. Southerly flow and partly cloudy skies will initially lead to the hot weather. Even though we may see a few showers and storms across the area on Friday, these should not occur until late in the day, and should allow temperatures to once again rise to near record values. The overall trend in the extended is for daily chances of late day showers and storms and warmer than normal temperatures. A poorly defined frontal boundary is forecast to stall out across the region over the weekend and will be the trigger needed for shower and storm activity. Winds will be primarily from the south or southeast during the period, which will contribute to the expected warm weather. Highs will range from the low to mid 90s the first couple of days in the extended, with max values mostly in the upper 80s after that. Nightly lows will average in the mid to upper 60s across the area. The best chances for rain should be over the weekend, as the front stalls over the area. The rain chances should last through the day on Monday. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) ISSUED AT 820 PM EDT TUE SEP 10 2019 With upper level ridging and surface high pressure dominating the region, mainly dry weather will continue for at least the first 18 hours of the period. Isolated convection is expected to develop during the last 6 hours of the period. Chances and confidence in this are too low to include at this time. Few clouds near 5kft AGL were included at all sites during all or portions of the last 6 hours as more in the way of cumulus development is expected on Wednesday as compared to today at the very least. Winds will remain out of the south to southwest during the first 15 to 18 hours of the period, before becoming west. However, outside of any convection, speeds will remain below 10kt. Patchy river valley fog will develop around or after 6Z and affect some locations as late as 13Z, but this is not expected to affect any of the TAF sites. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...GREIF LONG TERM...AR AVIATION...JP
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
901 PM CDT Tue Sep 10 2019 .UPDATE... 900 PM CDT While all is quiet this evening with a mid summer-like warm and humid air mass in place, things *could* get more active later tonight and into or even through Wednesday morning. It`s a tricky/low confidence forecast regarding convective trends, as potential available forcing is pretty subtle amidst high MUCAPE and little capping. 00z RAOBs at DVN and ILX featured ~3000-3500 j/kg of MUCAPE, mean mixing ratios of 14.5-15 g/kg, high freezing levels near 14kft and anomalously high PWAT values near 1.75". The main uncertainty is whether there will be enough forcing to kick off convection over the area and/or convection festering into the area on outflows. Given the strong instability above stabilizing boundary layer, it won`t take much to get thunderstorms to go, but forcing mechanisms are less clear, leading to a wide range of solutions on near term and high-res CAM guidance. A few weak short-waves may approach the region overnight into early Wednesday, one lifting northeast from Kansas City area and another near St. Louis that will lift northeast across central Illinois and into central Indiana. Models are varying given lower magnitude of the forcing. Our official forecast is relatively similar to afternoon forecast package and favors the northern wave possibly kicking off storms near the Wisconsin border after midnight with outflows then potentially aiding in scattered storms trending southward with time toward I-88 and even I-80 corridor or south during Wednesday morning. Interestingly, RAP is much more aggressive than recent HRRR runs, which initializes with RAP as initial conditions. Despite the uncertainty, should storm coverage increase tonight into Wednesday morning, could be a localized flooding threat given high PWATs and mixing ratios along with high freezing levels (warm cloud processes). As such, the WPC updated 01z day 1 excessive rainfall outlook maintained a Marginal Risk for I-80 and north. Also can`t rule out the southern wave kicking off thunderstorms in southeast CWA, as shown on latest HRRR and new 00z 12km NAM, though new 00z 3km NAMNest is much less aggressive than 18z run. Finally, exact evolution of thunderstorms or lack thereof will certainly have potential to significantly impact high temperatures on Wednesday for at least portions of the area. This will especially be the case if wind direction is augmented by outflows, while warmer temps will be possible if convection is lacking. For now, trended slightly lower with high temps, particularly north of I-80. At this time, appears best chance to reach 90 again will be south tomorrow, but certainly still possible north. Castro && .SHORT TERM... 329 AM CDT Through Tonight... Following the passage of a warm front lifting north across the CWA has spread unseasonably warm, humid air across the region. Temperatures across the region should top out this afternoon in the upper 80s to lower 90s with sfc dewpoints in the upper 60s to middle 70s. Latest radar and satellite imagery indicate the main cu development across nwrn IL into ern IA with a sct line of showers from sern WI to ern IA. Some of these showers could linger into the early evening with an isolated cell potentially developing into a short-lived thunderstorm, but with the main forcing and low-level jet focused more to the west into IA, expect much of the area to be dry through the evening and into the overnight hours. The main window of opportunity for more widespread showers and thunderstorms should be after midnight and more likely toward the pre-dawn hours. The high res guidance is divided into 2 camps, with either developing an MCS over srn WI and then diving into nrn IL or a more restrained solution with activity more confined to the area invof the warm front with outflow and and a lower coverage of shra/tsra, but also sagging south into the northern portions of the CWA. Have trended the latest update more toward the latter solution, but there does still remain the chance that the former solution could develop as well. In either case, there should be ongoing convection for the morning rush hours, with the main question being how far south that the activity will push. Currently, feel that much of the activity will be along and north of I-80, at least into tomorrow morning. With the warm/moist airmass already in place and a persistent swly fetch of warm/moist air expected to continue through the night, expect unseasonably muggy conditions tonight, with lows in the 70s. && .LONG TERM... 224 PM CDT Wednesday through Tuesday... Wednesday and Thursday...Challenging forecast with regards to temperatures and thunderstorm chances as a warm front continues linger across the region. Model guidance through the day on Wednesday does suggest that the front will remain north of the WI border through the day with any earlier in the day convective outflow likely shifted back north of our area, with the exception possibly being right near the lake shore across NE Illinois. Therefore warm and humid conditions should be able to develop/redevelop following any remnant morning precipitation each of the next few days. Guidance would tend to favor areas north into WI for development during the day, but with this development being a bit more robust, we could be in pattern where convective outflow will drive into NE Illinois during the later afternoon/evening. These details are certainly challenging to pinpoint at this distance, and much will hinge on where the composite outflow/synoptic boundary ends up based on convection Wednesday afternoon. Portions of the area are in a Marginal risk for severe storms on Wednesday afternoon/evening. Suspect during the day any development would be more isolated away from I-90 north or I-88 north, and even there it could be low coverage. Competing influences with an increasing low level jet Wednesday night and cool northeast outflow should inhibit the front from diving back south across the remainder of the area, and therefore and lends some credence to another warm and humid day Wednesday, with more uncertainty Thursday as it appears we would maintain some form of onshore flow. Areas south should warm without issue. Our next more organized front is slated for later Thursday. The timing is important locally as it will likely play a significant role in how widespread/intense convection will be. A slower system would be a more diurnally unfavorable timing of fropa locally (overnight Thursday into early Friday morning) for more intense/widespread convection, while a faster system (which seems unlikely), could place convective timing into the evening hours Thursday, a bit closer to more favorable time of day. There is also the possibility of prefrontal warm sector development, whereas if that were to occur would favor thunderstorms, but even so the shear is more tied to the upper trough and front. Therefore highest severe probs are currently upstream of our area. Friday through Monday...The strong surface cyclone will Friday should be breezy and much less humid with any lingering showers in the eastern CWA likely to end in the morning. Current forecast for the weekend is dry with moderating trend, though the latest GEM and ECMWF suggest a shortwave could kick off convective in the region Sat night into Sunday morning in advance of a northward returning warm front, but neither is too overly excited, and the higher probs will be NW CWA, mainly west of the Chicago area (and more so I-39). There is still a fairly good signal in the majority of the medium range guidance on the eastern CONUS upper ridge re- strengthening early next week, not to the strength of the current ridge, but its amplitude appears to be larger as a deep trough develops in the west. This pattern would suggest additional warm and humid days next week, maybe not to degree of this week, the amplitude of the pattern is one that would keep the lower Great Lakes mostly dry. KMD && .AVIATION... For the 00Z TAFs... Quiet conditions with light SW winds are expected through at least the early overnight hours under plenty of mid to upper level clouds. Two clusters of convection are possible late tonight into Wednesday morning. A veering low-level jet to the west overnight will focus convection into southern WI late tonight. Much of this activity should remain north of the Chicago metro terminals, but possibly affect RFD. A second cluster of convection with a small mid-level disturbance is also possible across portions of northern IL into northwest IN generally in the 11-15Z period Wednesday. Confidence remains low on if this convection will develop, so have maintained a PROB30 TS for the Chicago metro sites until newer guidance is available and observational trends are more apparent after 00Z. Winds on Wednesday will depend on potential convection during the morning. If convection fails to materialize, gusty SW winds can be expected most of the day. However, if convection does occur in the morning, a period of SE winds will likely occur behind the convection for several hours before gusty SW winds develop. Finally, a boundary shifting south across the area by late Wednesday evening is expected to initiate scattered convection, so have used a VCTS to convey this in the ORD/MDW TAF. Kluber && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
735 PM CDT Tue Sep 10 2019 .Updated for 00Z Aviation Discussion... Issued at 725 PM CDT Tue Sep 10 2019 && .SHORT TERM...(This evening through Wednesday night) Issued at 348 PM CDT Tue Sep 10 2019 Short term concern is severe convective threat Tonight and Wednesday night along with the heavy rain/flash flood threat. Sky finally broke out to attain forecast highs around 80 over much of the southern CWA. Sunshine will give way to increasing clouds this evening from the southwest along with increasing rain/thunder threat into the southwest area before 06z in the southwest and working east into west central WI after 09z. Various HIRES models continued their trend of developing convection over South Dakota/Nebraska region and shift east ahead of the propagating trough and development of low level jet into southwest MN late. High PW`s to 1.75(2 to 3 standard deviations above normal) into southern MN by 12z Wed should provide some decent rainfall rates. The current QPF forecast has 1 to 2.5 inches into a small part of south central MN through 18z Wed. Contemplated flash flood watch for the southern 2 tier of counties along I-90 but believe convective system that does develop over South Dakota will be progressive through early Wed morning. Latest HRRR model trend does develop linear complex as it moves into southern MN late. Will need to monitor for severe convective wind threat per SPC Day1 outlook. System moves east during the early morning and should weaken as it moves east. Then convective setup for Wednesday afternoon and night will depend on overall movement of surface warm front. At the moment the front is forecast to remain over the southern third of the area through the afternoon. At least lower 80s expected into south central MN with 70s into southern MN with some 60s over the far northern CWA. Should see convection fire by late afternoon along/north of the front with all modes of severe weather possible along warm front and at least a wind threat with the propagation of the cold front. Heavy rainfall will remain a threat with another 1 to 2 inches possible over eastern central MN into a portion of west central WI. Flash flood threat may lift into this region if warm front lifts fast enough north into early Wed evening. Will have to monitor model trends for possible flood headline this period. .LONG TERM...(Thursday through Tuesday) Issued at 348 PM CDT Tue Sep 10 2019 We will not be out of the woods with the threat for severe weather and heavy rainfall on Thursday. At daybreak Thursday, the mid/upper trough is progged to be over the western Dakotas, with the surface low entering southwestern Minnesota. Expect showers and thunderstorms to be be ongoing Thursday morning as overrunning continues. We really don`t look to see a break until the cold front passes Thursday night. Given PWATS still nearing 2 inches, heavy rainfall will remain a concern. The severe weather threat will be contingent on where boundaries are located and how much instability we can tap into. Showers look to be possible on Friday in the cyclonic flow behind the departing trough, primarily over central MN/WI. Zonal flow then develops for the weekend, which will mean an overall trend to drier weather but we can`t rule out a hit or miss shower. A deepening trough over the western CONUS induces mid-level ridging over the north central CONUS early next week. This will mean a return to above normal temperatures with highs in the upper 70s and lower 80s looking likely for Monday and Tuesday. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 725 PM CDT Tue Sep 10 2019 VFR conditions this evening but thunderstorms across South Dakota will move eastward overnight and should affect KRWF and KMKT, but could reach as far north as KMSP, KRNH, and KEAU. Expect low clouds to continue for Wednesday, and could see additional showers and thunderstorms. KMSP... VFR conditions this evening but thunderstorms across South Dakota will move eastward overnight and could affect KMSP for the morning rush. The model guidance has been a bit slow, so sped up the timing of the thunder. Expect low clouds to persist for Wednesday, and could see additional showers and thunderstorms. /OUTLOOK FOR KMSP/ THU...MVFR with IFR/TSRA possible. Wind SE at 10 bcmg SW at 20 kts. FRI...VFR/MVFR possible. Wind W at 20G30 kts. SAT...VFR with MVFR/TSRA possible. Wind S at 10G20 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && $$ SHORT TERM...DWE LONG TERM...LS AVIATION...JRB
Area Forecast Discussion
National Weather Service Pueblo CO
305 PM MDT Tue Sep 10 2019 .SHORT TERM...(This evening through Wednesday) Issued at 305 PM MDT Tue Sep 10 2019 SW upper flow over the area for another day, as deep trough slowly edges eastward through the Pacific NW. Surface trough remains in place over the sern plains, with weak convergence and very unstable air mass producing some isolated thunderstorms along and east of the boundary. Farther west, still waiting for wrn CO convection to reach the Continental Divide as of 21z, though with very dry low levels still in place, initial round of storms will contain more wind than rain as activity pushes newrd into the region. Tonight, HRRR keeps convection going in the far se until 03z or so, before storms weaken as they shift into KS/OK. A few CAMs keep at least isolated storms going well into the night along the Continental Divide, with a few cells even reaching the Sangres after 06z, so will retain low pops in the forecast for mainly the higher peaks into Wed morning. On Wed, upper trough lifts e-ne through the nrn Rockies, while w-sw flow deepens across CO. Still a threat of some thunderstorms near the Continental Divide, especially earlier in the day, before moisture is swept away by strengthening wly flow. Looks like too much downslope flow elsewhere for convection, though a storm or two may fire toward 00z along the surface trough near the KS border. Wly flow and deep mixing should lead to another day of very warm to hot temperatures, with readings deep into the 90s across the eastern plains. .LONG TERM...(Wednesday night through Tuesday) Issued at 305 PM MDT Tue Sep 10 2019 Wednesday Night and Thursday Morning: Isolated showers will exist over the far eastern plains at the beginning of the long term forecast period (Wednesday at 6PM MDT). CAPE values over the far eastern plains will be around 1,500 to 2,000 J/kg with 0-6 km bulk shear values around 20-30 kts. The hodograph doesn`t seem to conducive for sustaining severe storms, with a slightly curved profile, but the main characteristic is speed shear profile. DCAPEs around around 1,500-2,000 J/kg, so gusty winds are likely under any of the storms that form. So overall, severe criteria hail isn`t really expected, but is possible, but the main impact of concern are severe criteria wind gusts. The storms will likely dissipate or move out of Colorado by midnight. An upper level trough will propagate over the region overnight, which will lower the 700 hPa temps to right around freezing, which means... snow over the higher peaks of the northern continental divide. Early Thursday morning a cold front will propagate over the eastern plains, but PW and RH fields reveal that the passage should be dry, with gusty northerly winds as the main impact. Some drier air will remain over the western half of the region, so low temperatures will be chilly over the shear mountain valleys. Places like Creede and Westcliffe will see overnight lows in the low 30s. The plains will be in the low to mid 50s, the mountain valleys in the upper 30s to low 40s, and the mountains in the 20s to low 30s. Thursday: With the front passed, temperatures will be around average for the first time in a while. High temperatures over the eastern plains are expected to be in the low 80s, the mountain valleys in the low 70s, and the mountains will be in the 40s to 60s. The atmosphere will be stable, so now showers or thunderstorms are expected throughout the day on Thursday. The northerly winds will shift to the east during the evening hours, which could create some clouds over the mountains and the potential for low clouds over the plains. Friday: A tight pressure gradient over the eastern plains will cause gusty winds during the afternoon hours, and will advect low level moisture from the south, which will set-up a weak dryline. Some isolated thunderstorms are possible over the Colorado and Kansas border. Everywhere else is expected to be dry. Temperatures will warm up again to above average, but temperatures are still expected to be cooler than what we`ve been experiencing. Saturday through Tuesday: An upper level low will try and makes its way across the Great Basin and over Colorado in the extended term. The result will be southwesterly flow over Colorado, which means that fire weather conditions will be possible. The limiting factor will be how strong the surface winds get. Saturday and most of Sunday is expected to remain dry, but low level moisture from the Pacific will advect ahead of the previously mentioned upper level low, which will bring showers to the Continental Divide. Temperatures will be well above freezing, so no snow is expected while the trough is to the west of the region. Similar conditions will remain for Monday and Tuesday. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 305 PM MDT Tue Sep 10 2019 VFR at all taf sties the next 24 hrs, as any convection will stay either over the mountains near the Continental Divide, or over the sern plains near the KS border. Strong cold front will pass through KPUB and KCOS Wed evening, leading to a period of strong north winds overnight into Thu morning. && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...PETERSEN LONG TERM...SKELLY AVIATION...PETERSEN
Area Forecast Discussion
National Weather Service Sacramento CA
325 PM PDT Tue Sep 10 2019 .SYNOPSIS... A weather system will bring a chance of showers and isolated thunderstorms to the mountains this afternoon and early evening. Below average temperatures continue into mid-week. A wind shift will provide a warm up and potential smoke issues for the Valley from surrounding fires. Dry weather returns for the end of the week while a stronger system passes through early next week bringing cooler weather and potential precipitation. && .DISCUSSION... A closed upper low centered along the Washington/Oregon border is carrying a band of shortwave energy through interior northern California. As this disturbance sweeps through, showers and isolated thunderstorms continue to fire over the mountains with occasional lightning strikes already observed in many of the stronger cells. While current observational data and dual-pol radar estimates show hourly rates up to a quarter inch, some isolated heavier amounts are possible within the heftier cores. Also cannot rule out the potential for small hail and gusty winds with the threat winding down by the mid-evening per recent high- resolution guidance. Outside of the mountain showers, the Valley has remained mostly sunny with below average temperatures, generally staying in the upper 70s to low 80s. After the longwave trough passes to the east, a shift in the local wind fields is anticipated which will impact the wildfire smoke transport. On Wednesday, synoptic gradients support a shift to a light northerly flow while turning more east-northeasterly overnight. Consequently, recent HRRR smoke plume simulations show a bit of smoke moving back toward the Valley. For Thursday and Friday, an offshore ridge will swiftly advance through the region affording a marked warm up. While a shortwave passes through the Pacific Northwest early Friday, it should produce little to no impact to the sensible weather. High temperatures each day will feature mid/upper 90s across the Valley with 70s being more commonplace over the higher terrain. This is roughly 5 to 10 degrees above average for early September. ~BRO && .EXTENDED DISCUSSION (Saturday THROUGH Tuesday)... While Saturday will prove to be another warm day across the region, big changes loom ahead as a significant pattern change unfolds for early next week. This particular feature actually has an origin over the Bering Sea (west of Alaska) with the system eventually reaching the Washington coast by Sunday morning. The GFS/ECMWF/CMC ensembles and deterministic solutions are in decent agreement, albeit with timing issues as the GFS/GEFS mean are quicker. Fairly impressive 24-hour height falls are shown, roughly in the 10 to 12 dm range, with 500-mb heights being 1.5 to 2 standard deviations below climatology. At a minimum, this upper trough will provide a significant cool down with Valley high temperatures likely in the mid/upper 70s on Monday/Tuesday (10 to 15 degrees below average). What remains to be seen is how much precipitation spreads over the region as there are some rather robust solutions (i.e., 12Z GFS). The mountains and foothills should see some showers and thunderstorms with the Valley being more of an unknown. Abundant dry air underneath cloud bases typically makes accumulating rainfall difficult this time of year over the Valley. For now will maintain the best chances across the higher terrain. ~BRO && .AVIATION... VFR conditions are expected for the next 24 hours except for possible MVFR/IFR conditions from isolated thunderstorms through 05z and from smoke near wildfires. Winds will generally be 12 knots or below except for gusts up to 25 knots in the vicinity of the Delta tonight and over higher terrain through 04z this evening. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$