Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/01/20

Area Forecast Discussion
National Weather Service La Crosse WI
1106 PM CDT Mon Aug 31 2020 .SHORT TERM...(This evening through Tuesday) Issued at 300 PM CDT Mon Aug 31 2020 Forecast concerns in the short term will be extent of fog tonight and low temperatures, then small chance for showers and thunderstorms Tuesday. Rainfall this morning was heaviest across parts of Dodge, Olmsted, Winona, Houston, Wabasha, and La Crosse Counties where some spots picked up 2 to 3 inches of rainfall. The highest amounts were near Kasson with 2.8 inches in Olmsted County and 2.7 inches at Whitewater State Park in Winona County. The 12Z MPX upper air sounding was moist to around 450mb with 1.51 inches of precipitable water. Instability was limited around 300 to 500 J/kg and 0-6km shear was 61kts. The most active thunderstorms were pre-frontal, however with multiple rounds of showers and storms, they did put down some decent rains. The latest water vapor satellite imagery, visible satellite, radar, and observations show the showers and thunderstorms have moved out of the forecast area. The cold front has switched winds around to the northwest and at 2pm was located near... A few cumulus are filling in behind and the brisk northwest winds are ushering in dewpoints in the 40s and 50s for this afternoon. The shortwave trough is swinging through the Upper Peninsula of Michigan with a 90kt jet at 300mb keeping the precipitation progressive. Cirrus are already spreading across the Dakotas ahead of the next shortwave over the Rockies. Surface high pressure will build into the region tonight with winds becoming light and variable. With the wet ground and light winds, attention turns to potential fog formation. Some of the short range models highlight the parts of western Wisconsin for fog Tuesday morning. With the increasing clouds from the west overnight, this should help mitigate the fog somewhat. Did go ahead and include some fog mention for our western Wisconsin counties, but depending on the cloud cover, this may have to be expanded. Tuesday, the next shortwave trough will track across the Plains and into the forecast area. Isentropic lift increases across the forecast area with isolated showers possible. There is a hint at a narrow band from Minnesota into Wisconsin and another potential area from northeast Iowa into southwest Wisconsin. The northern edge of the instability could make it into our area, so did include isolated thunder mention. Lows tonight should mostly be in the 40s, with a few warmer spots in the lower 50s. High Tuesday will be cooler than normal in the lower to mid 70s. .LONG TERM...(Tuesday night through Monday) Issued at 300 PM CDT Mon Aug 31 2020 Westerly flow develops Wednesday ahead of the next approaching shortwave. Warmer temperatures are forecast with highs from the mid 70s to the mid 80s. The front pushes through Wednesday night into Thursday morning. For now have the chance for isolated showers and thunderstorms confined to north central Wisconsin. Highs Thursday should be in the 70s to lower 80s. The next cold front arrives Saturday night into Sunday and we have chance showers/isolated thunderstorms included in the forecast. Some of the extended forecasts have some colder temperature for Sept 8th and 9th. This will be a period to watch out for related to the potential for frost in frost favored areas. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1100 PM CDT Mon Aug 31 2020 High and mid clouds will move into the area overnight. These clouds continue to provide some uncertainty on whether KLSE will see dense fog overnight. In addition, the winds do not become favorable until late. Meanwhile, the temperature and dew point spread is around 6F which make it some what better for the possibility of dense fog. To further complicate things the RAP keep the boundary layer dry. Due to this uncertainty just went with BCFG. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...Zapotocny LONG TERM...Zapotocny AVIATION...Boyne
Area Forecast Discussion
National Weather Service Dodge City KS
604 PM CDT Mon Aug 31 2020 ...Updated Aviation Discussion... .SHORT TERM...(This afternoon through Tuesday night) Issued at 1200 PM CDT Mon Aug 31 2020 A refreshing preview of autumn, as noticeably cooler, and more impressively, much drier air invades SW KS. It has been quite some time since we have seen dewpoints fall well down into the 40s. The cold front has cleared Barber county as of late morning. The N/NE winds will continue to diminish quickly through this afternoon as weak surface high pressure builds over Kansas. Remaining stratus will also gradually dissolve this afternoon, with comfortable afternoon temperatures in the 70s. A strong shortwave diving into the Pacific NW/Idaho at midday, will evolve into a weak closed low near Grand Junction Colorado at sunrise Tuesday, then sink south into northern New Mexico Tuesday evening. Diffluence aloft ahead of this digging shortwave will supply synoptic lift over SW KS tonight through early Tuesday, with increasing clouds expected. With easterly components in the boundary layer and upslope flow, stratus is also expected early Tuesday morning. The challenge revolves around shower generation and precipitation chances with this system. Some models including ECMWF and the latest extended HRRR iterations develop scattered to even numerous showers during the morning/midday hours Tuesday. 12z NAM is almost bone dry. 12z GFS offers a compromise between these two extremes. Tried to take a middle ground approach with low chance/scattered category pops in the grids late tonight through midday Tuesday, but with the model disarray confidence is not great. Instability will be very weak; kept isolated thunder in the forecast, but would not be surprised if there was no lightning at all. Lows tonight in the upper 50s and lower 60s with light NE winds. The mild temperatures will continue Tuesday, as the cool airmass is maintained by light NE winds. Extra cloud cover and any showers (favoring the southern counties/Oklahoma border nearest the New Mexico upper low) will also work to keep temperatures below normal for the first day of September. Again, even if the wetter model solutions verify, instability will be nil to weak, and thunder will be limited. Expect afternoon temperatures in the 70s for most locales, with a few lower 80s where some partial sunshine can be realized. .LONG TERM...(Wednesday through Monday) Issued at 155 PM CDT Mon Aug 31 2020 Long term will feature an extended period of typical late summer/early autumn weather, with dry conditions prevailing and mild/comfortable temperatures. Weak closed midlevel cyclone near Clovis, New Mexico sunrise Wednesday will drift eastward into West Texas daylight Wednesday. The vast majority of rainfall with this system will remain south of Kansas, but can`t rule out a few showers grazing the Oklahoma border at times. Most locations will remain dry. With more sunshine, Wednesday will be warmer with maximum temperatures mainly in the lower to mid 80s. High confidence another long stretch of dry weather is on the way Thursday through Sunday. Strong high pressure aloft (596 dm) over Nevada on Thursday, is progged by 12z ECMWF to remain stationary over the Great Basin and strengthen to near 600 dm by Sunday. Heights climb over SW KS through this time, with no forcing for rainfall and few if any clouds. A weak dry cold front is expected Thursday with little fanfare, just a northerly wind shift. Afternoon temperatures in the 80s will be typical, as the core of the upper high and its associated heat will remain well west of Kansas. Long term models hint at a much stronger cold front early next week, and this feature will likely provide the next opportunity for widespread rainfall. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 602 PM CDT Mon Aug 31 2020 Clear skies and a northeasterly wind at less than 10 knots will begin the night but the persistent east to northeasterly flow overnight will bring low level moisture back into southwest Kansas after 06z Tuesday. Based on the latest BUFR soundings this low level moisture will lower ceilings into the IFR category after 09z Tuesday and a period of LIFR conditions will be possible between 12z and at 17z Tuesday. Areas of fog and drizzle will also be possible given the forecast depth of this low level moisture early Tuesday morning. Ceilings will gradually improve late Tuesday morning but given the depth of this low level moisture the clouds will linger through most of the afternoon as an east to northeasterly flow continues at 10 knots or less. There will also be a chance for some widely scattered early morning convection. && .PRELIMINARY POINT TEMPS/POPS... DDC 60 79 60 83 / 30 20 10 10 GCK 58 75 58 82 / 30 30 10 0 EHA 58 78 57 82 / 20 30 30 10 LBL 57 82 60 84 / 30 30 30 10 HYS 58 77 59 84 / 20 20 0 0 P28 65 83 64 82 / 30 30 20 20 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Turner LONG TERM...Turner AVIATION...Burgert
Area Forecast Discussion
National Weather Service Fort Worth TX
701 PM CDT Mon Aug 31 2020 .SHORT TERM... /NEW/ /Tonight through Tuesday Night/ Showers and thunderstorms have increased in coverage along a well defined cold front extending from near Midland to Vernon to Oklahoma City this evening. This activity should primarily remain across our far northwest counties and across parts of Oklahoma into the nighttime hours as mid level flow becomes a little more southwesterly. This should keep most of North and Central Texas precipitation free this evening. An axis of moderate instability is present from near Wichita Falls eastward along the Red River and across much of southern Oklahoma. To the south of this instability axis, low level moisture is a little less, but a strengthening low level jet should allow this to recover overnight. For the remainder of tonight, we`ll have the highest PoPs off to our northwest through midnight. The latest runs of the HRRR actually keep the bulk of the convective activity across Oklahoma overnight, but with low level warm advection becoming maximized via the low level jet just north of I-20, I have to think that some of this convection will tend to build southward toward morning. So we`ll continue the trend of showing increasing PoPs south of I-20 into early Tuesday morning. There will likely be a break in the convective activity as this initial complex weakens late tomorrow morning, but as an upstream shortwave digs into West Texas late tomorrow, additional showers and thunderstorms are expected to develop in the late afternoon/evening and move across North Texas overnight. Short term hazards... Heat Advisory... We`ll address the Heat Advisory which currently runs through Tuesday evening across a good chunk of North and Central Texas. As of now we`ll leave this unchanged, however, if it is more apparent that convection will continue southward through the morning hours, the northern portions of this advisory may be cancelled. To the south, it will still be quite hot and humid with highs in the mid/upper 90s and dewpoints in the mid 70s. Heat indices should easily exceed 105 degrees. Flooding Potential... Given the potential for deep convection to become locked onto a slow moving boundary overnight into Tuesday, the threat for localized flash flooding is increasing. We`re already seeing nearly stationary storm motion off to the northwest. With an increasing low level jet overnight, the threat will quickly increase across parts of the Red River Valley. There is some potential for 3-6" of rain overnight with any storms that are slow moving. We`ll issue a Flash Flood Watch for our Red River counties and include Young/Jack/Wise for now. This is basically everywhere north of the current Heat Advisory. This watch will also likely be modified to some degree over the next 24 hours. Severe Threat... The severe threat will primarily be this evening and tonight with convection tied to the front. Strong winds and hail will be the main threats. This threat will transition into a hydrologic threat late tonight through Tuesday. Dunn && .LONG TERM... /Issued 400 PM CDT Mon Aug 31 2020/ /Tuesday Night Through The Labor Day Weekend/ September is off to an active start as unsettled weather with increasing rain chances and temperatures near or below average for this time of year will punctuate the kick-off of meteorological fall. There are no significant chances to the long term forecast with this issuance. The best widespread rain chances continue to be Tuesday night through Wednesday across North Texas with more isolated/scattered activity across parts of Central and East Texas. Rain chances linger through the week as additional rounds of showers and thunderstorms remain possible into Labor Day weekend. An upper-level low will approach the Southern Plains from the Desert Southwest on Tuesday with west-southwest mid-level flow streaming across the state of Texas. Subtropical moisture transported by this southwest oriented flow will prime the region with precipitable water value in excess of 2", making heavy rain possible through the period. At the surface, a cold front will continue to move southward through the region late Tuesday and Wednesday. This boundary in addition to any remnant outflow boundaries lingering from the Monday night/Tuesday storms and large scale lift from the approaching shortwave should be sufficient for thunderstorms to develop across North and Central Texas. As this activity continues to move southeast into better moisture and instability, moderately deep layer shear may be sufficient for damaging winds and strong updrafts capable of hail. With ample moisture in place, all storms that develop will be efficient rain producers, with heavy rain likely which may lead to localized flash flooding issues and minor river flooding, especially in areas that received rainfall in the past few days. The heaviest rainfall is still forecast to fall along and north of the I-20 corridor where a widespread 2 to 4 inches of rain is possible with isolated accumulations of 5 to 6 inches possible through Wednesday night. The GFS continues to be more progressive with the trough axis advancing across the Southern Plains through the middle of the week. This would allow drier, post-frontal air to filter into the region bringing a premature end to rain and storm chances. The ECMWF continues to advertise a slower evolution with the trough axis stalling to the southwest of our CWA which would hold upper level support and moisture in place for storm chances to continue across the region into the holiday weekend. In the absence of any consensus among guidance, we will continue to favor the slower solution as recent runs of the GFS are trending somewhat slower. As mentioned in the short term discussion above, while the likelihood of a flood watch is increasing due to forecast potential for excessive rainfall we will postpone issuing a watch at this juncture. Regarding temperature through this period: While this system is not the deep push of cold air some of us are hoping for it will provide welcome relief from the excessive heat and humidity we have been muddling through recently. Expect cooler conditions with highs from the low to mid 80s along and near the Red River to the low to mid 90s in Central Texas. Lows will dip down into the 60s and 70s by early next week. 12 && .AVIATION... /NEW/ /00Z TAFs/ VFR will prevail through this evening, but increasing thunderstorm chances will occur later tonight through Tuesday along with widespread MVFR cigs overnight into Tuesday. A low level jet will transport moisture northward tonight resulting in MVFR cigs after midnight. Thunderstorms to the northwest should primarily ride along the Red River but will expand southward toward morning. We`ll have VCTS by 11Z in the Metroplex with prevailing TS around 14Z. There will likely be a break in the shower/storm activity through afternoon before rain/storm chances increase again Tuesday evening/night. At Waco, VFR will prevail this evening with MVFR cigs overspreading the region tonight. Thunderstorm chances will begin to increase Tuesday afternoon and continue through Tuesday night. Dunn && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 80 96 76 88 74 / 40 60 70 70 40 Waco 80 100 77 93 75 / 20 30 40 50 30 Paris 75 87 73 82 71 / 70 70 70 80 40 Denton 78 93 74 86 72 / 60 60 80 70 40 McKinney 78 94 74 86 72 / 50 60 70 70 40 Dallas 80 96 76 89 75 / 40 60 70 70 40 Terrell 78 97 75 89 73 / 40 50 60 60 30 Corsicana 79 96 77 89 74 / 30 30 40 50 30 Temple 79 99 77 94 74 / 10 20 30 40 30 Mineral Wells 75 96 71 86 69 / 60 60 80 70 40 && .FWD WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 8 PM CDT Tuesday for TXZ103>107-117>123- 131>135-144>148-157>162-174-175. && $$ 91
Area Forecast Discussion
National Weather Service Huntsville AL
937 PM CDT Mon Aug 31 2020 .NEAR TERM...(Rest of tonight) Issued at 937 PM CDT Mon Aug 31 2020 Calmer weather prevailed across most of the Tennessee Valley this evening, after a stormy afternoon and early evening. Shower and thunderstorm activity that occurred earlier has for the most part dissipated. At the moment, an area of light showers was heading ESE across parts of NW Alabama, from south of the Quad City to the Golden Triangle. Mid evening temperatures ranged in the 70s with light winds. Shower activity moving over NW AL was stronger convection a couple of hours ago, with the satellite indicating a remnant cirrus cloud shield tracking with the showers. Overall shower activity should end towards midnight. In mostly clear areas between those higher clouds, lower clouds and fog was beginning to form. Fayetteville was reporting variable visible from 2-5 miles and low clouds bases of less than 500 ft AGL. Given longer later summer nights, more patchy fog formation is possible tonight. Areas that received, say more than a tenth of an inch would be more susceptible for fog formation, as well as those normally fog prone locations, and places near large bodies of water. The RAP and HRRR were hinting that an approaching upper system could help generate isolated convection before daybreak over NW AL. Kept this possibility in the grids, but scaled it back somewhat. Showers will probably become more scattered to maybe numerous later Tue afternoon with more heating and resultant instability. .SHORT TERM...(Tuesday through Wednesday) Issued at 232 PM CDT Mon Aug 31 2020 Active pattern continues on Tuesday as a weak shortwave trough will shift NE from the lower Mississippi Valley and across the Mid-South and Tennessee Valleys. Additionally, a remnant outflow boundary from today`s convection will also stall over the area, serving as an additional focus for convection. The end result will be another round of scattered to numerous showers and thunderstorms from the mid/late morning through the afternoon. As is the case today, locally heavy rainfall/flooding will be the primary concern, along with the possibility of some localized gusty winds from a couple of strong storms. Would expect this activity to wane fairly quickly with the loss of heating and the fact that the aforementioned shortwave will have lifted well NE of the area after 00z. An upper-high over FL/GA will then attempt to briefly build in the Deep South on Wednesday. This ridge will help to keep a stronger frontal system stalled to our northwest (at least for the time- being), and subsequently result in a mostly dry day. In fact, the latest guidance indicates that Wednesday will likely be mostly sunny at times, with highs potentially reaching the lower 90s (and heat indices around 100 degrees). Given this, Wednesday may well be the warmest day of the week for most locations across our area. .LONG TERM...(Wednesday night through Sunday) Issued at 232 PM CDT Mon Aug 31 2020 The Tennessee Valley will remain wedged between a frontal system just to its north and west across the Ohio Valley/Southern Plains and a fairly strong Bermuda High that will attempt to remain established across much of the Deep South for the remainder of the work week. Behind this boundary much drier (more autumn-like) air exists, while continued warm, muggy conditions will exist ahead of this feature underneath the ridge. For Thursday and Friday, expect a gradual uptick in the coverage of convection as an upper-trough swings into the Ozarks and approaches the Mid South region. This feature will help to generate some scattered showers and storms along the aformentioned boundary just to our northwest which should be stalled along the I-40 corridor of TN. Eventually, this boundary will sag further south and east into the region on Friday afternoon and evening , but do not expect to see more than scattered thunderstorm chances once again as the stronger ridging aloft should win out. However, as mentioned above, a cooler, drier air mass does exist behind this boundary as the high retreats back off the NC/SC coast. As a result, we can expect an early taste of autumn this weekend, with lower RH and highs in the low to mid 80s -- to go along with plenty of sunshine and lower PoPs. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 703 PM CDT Mon Aug 31 2020 Shower activity that affected KMSL and KHSV continues to weaken as it moves eastward across NE AL. Other clusters of convection were nearing Cullman county from the west, and another area of storms was moving over north/central MS. The movement of both areas of storms appeared a bit south of due east. Shorter term model output generally have both areas dissipating during the course of the evening. Given both KMSL/KHSV both had a wetting rain (~1/4 of an inch or more), have included predawn patchy fog. Another approaching system and daytime created instability should bring more scattered to numerous showers/t-storms Tue afternoon. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...RSB SHORT TERM...AMP.24 LONG TERM...AMP.24 AVIATION...RSB For more information please visit our website at
Area Forecast Discussion
National Weather Service Wichita KS
644 PM CDT Mon Aug 31 2020 .SHORT TERM...(This evening through Tuesday night) Issued at 145 PM CDT Mon Aug 31 2020 Afternoon/evening storm activity in the CWA continues to be highly dependent on the location of the surface front. So far today, the front has been outpacing models in its southeast progression through the CWA. As the northern CONUS trough races out toward the northern Great Lakes region, the forward progression of the front may try to stall a bit as we head deeper into the afternoon. The front currently bisects the CWA in a line from approximately Maple City in Cowley County to Fall River in Greenwood County to Neosho Falls in Woodson County. Any locations along and southeast of this line should remain weather aware through the afternoon. For areas of southeast KS which remain along/ahead of the front and in the warm sector, large hail up to golf balls and damaging winds up to 65 mph will be possible. The unstable airmass over far southeast KS (according to RAP soundings) is characterized by MLCAPE of around 3000 J/kg, mid level lapse rate of 7.7 C/km, with 35kts of effective shear. SRH has backed off since previous runs as sfc winds have veered slightly, however, there would be a non- zero chance of a tornado anywhere outflow boundaries(s) intersect with the frontal feature which would locally (significantly) affect the SRH given ambient semi-favorable 3CAPE of around 100 J/kg. A few boundaries can be seen via satellite and radar currently bisecting the front, one moving NE out of OK and one moving SW from the complex that has moved out of northeast KS into southern MO. Model consensus keeps a decent baroclinic zone across the CWA tonight with no shortage of warm moist advection which should prompt some elevated convection tonight, mainly over the southern tier of counties. Looks like the moisture gradient will run just east and south of the KS turnpike before veering out over southeast KS toward the morning hours. Thinking that most of the activity should remain in the vicinity of the KS turnpike and points south and east. There are quite large differences between model derived elevated instability, for instance NAM pushing 4,000+ J/kg MUCAPE vs RAP indicating 2,500 J/kg MUCAPE. In either case, 1-6km shear of 20- 30kts would support some strong to severe storms tonight. Though there is some uncertainty in the degree of instability, thinking the strongest storms would be capable of golf ball sized hail and damaging winds to 60 mph, with 700-500 directional shear being a less favorable factor. Localized flooding from heavy rainfall will also be possible. If the front continues to move southeast this afternoon and evening, aided by outflow, and continues further south into Oklahoma, there is a chance that tonights area of elevated convection would also then shift south, so this will need to be monitored as we move through the evening hours for any updates. Tomorrow again, is very dependent really on where the cold front ends up tonight. There`s a pretty good chance that it remains to outpace models and ends up south into Oklahoma. The front should start to try and work back north tomorrow as a warm front as it gets influenced by the the deep upper trough that will have dug its way into the Great Basin by late morning tomorrow. Thinking the northward progression of the now warm front may not make it across the OK/KS border tomorrow. Whether it does make it, or it doesn`t, there doesn`t seem to be too much difference in terms of impacts. Would expect that the environment be pretty worked over in general from overnight convection so the severe threat would remain rather isolated in nature. Should the front remain to our south tomorrow, would still expect warm advection induced showers and storms to impact the southern few rows of counties. Scattered shower/storm activity may linger through Tues night-early Wed. .LONG TERM...(Wednesday through Monday) Issued at 145 PM CDT Mon Aug 31 2020 Another deep trough will push through the northern CONUS and drive the southern stream trough out of the Great Basin and into the southern Plains late Wed into Thu. It could mean a few more showers and storms as the next cold front swiftly moves through the region Thursday. Meanwhile, a western CONUS ridge will be building each day through the extended, propelling the area back into northwesterly flow aloft. This setup will bring much drier conditions back to the area through the weekend with temperatures trending up into the mid 80s. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 638 PM CDT Mon Aug 31 2020 A cold front was stalled over southeast Kansas this evening and will remain in the area before slowly pushing southward. Meanwhile low level moisture northwest of the front will yield low clouds in the IFR category late tonight into Tuesday morning. Storms look to redevelop over southeast Kansas late tonight and linger into the morning hours. The low clouds will be stingy and could begin to scatter out by Tuesday afternoon. && .PRELIMINARY POINT TEMPS/POPS... Wichita-KICT 67 83 65 84 / 50 40 20 20 Hutchinson 63 80 62 84 / 40 30 20 10 Newton 65 80 63 83 / 40 40 20 10 ElDorado 66 82 65 81 / 60 50 20 20 Winfield-KWLD 68 84 67 81 / 60 40 40 40 Russell 60 77 59 85 / 20 20 10 0 Great Bend 61 77 60 83 / 30 20 10 0 Salina 63 78 61 86 / 30 30 10 10 McPherson 63 79 61 84 / 30 30 10 10 Coffeyville 70 83 69 82 / 60 50 40 50 Chanute 69 82 67 82 / 60 60 30 40 Iola 68 82 67 83 / 60 60 20 30 Parsons-KPPF 70 83 69 82 / 60 60 30 40 && .ICT WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...KMB LONG TERM...KMB AVIATION...CDJ
National Weather Service Wilmington OH
859 PM EDT Mon Aug 31 2020 .SYNOPSIS... A series of upper level disturbances will bring occasional chances for showers and thunderstorms through Thursday. A cold front will push through the region Thursday night into Friday, ushering in a cooler and drier airmass by the end of the week. && .NEAR TERM /THROUGH TUESDAY/... A mid-level trough is currently moving across Wisconsin, with broad and generally unfocused southwesterly boundary layer flow ahead of the trough over the Ohio Valley. Weak 925mb theta-e advection appears to match up near the top of the boundary layer as determined by the 00Z KILN sounding, with just enough lift to spark some widely scattered showers this evening. As this theta-e advection appears likely to persist through the overnight, perhaps slightly more focused in the northwest ILN CWA after 06Z, a 20 percent chance of showers will be maintained through the overnight hours. Fog is the other concern overnight, with the light surface flow and plentiful moisture (dewpoints in the upper 60s to around 70). Guidance products and HRRR projections suggest fog will become fairly widespread overnight, with at least some chance of dense fog, particularly along and southeast of the Interstate 71 corridor. As mentioned previously, the lack of really solid clearing will be one limiting factor, so confidence in getting more than patchy dense fog is still not particularly high. It is also possible that stratus will develop by 12Z, further complicating the sky/visibility forecast. Previous discussion > We are still seeing some showers across our far south this afternoon in an area of some weak low level convergence. With some very weak mid level energy also pushing east across the region, will linger some slight chance pops into early evening for areas mainly to the south of the Ohio River. Will then dry things out overnight as some very weak mid level ridging tries to translate east across the region. In relatively light flow at the surface and with lingering boundary layer moisture, several of the models are suggesting the possibility for some widespread fog development later tonight. This may be somewhat dependent on how much clearing we end up with as we head into tonight but will at least allow for some areas of fog development later tonight. Lows tonight will be in the mid to upper 60s. && .SHORT TERM /TUESDAY NIGHT/... Mid level short wave energy will lift northeast from the mid Mississippi Valley Tuesday and across the upper Ohio Valley into Tuesday night as a frontal boundary sags slowly toward our area from the northwest. The potential for some lingering clouds Tuesday morning may affect how much we are able to destabilize through the afternoon. However, with temps into the mid 80s and dewpoints slowly rising into the upper 60s/lower 70s, sbcapes in the 1500 to possibly 2000 J/KG range may be possible through late afternoon. This combined with the approaching short wave, will lead to an increasing chance of showers and thunderstorms from the west later Tuesday afternoon into Tuesday night. Increasing low and mid level flow ahead of the short wave will also lead to an increase in deeper layer shear heading into Tuesday night. As a result, there may be a small window late Tuesday afternoon into early Tuesday evening where a few stronger storms may be possible, with gusty winds being the main threat. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Instability builds on Wednesday as the fa remains in the warm sector of a surface Low , but models are in moderate disagreement with the amount of CAPE. The GFS brings in 2000+ J/kg of CAPE over most locations while the NAM limits it to counties along and south of Ohio River. Decided to lean towards the NAMs resolution for Wednesday as it appears storm coverage will be more isolated further north. A deepening H5 trough on Thursday will usher in a wave of PVA and interact with a cold front sinking from the north, so keeping PoPs likely throughout the afternoon / evening. Models push out the precip by Friday morning as high pressure out of the northwest settles in. Cooler and drier air will ensue to start the weekend. The H5 trough in the GFS is slightly more deep / enhanced compared to the Euro, leading to forecasted temps about 5 degrees cooler for Friday and Saturday. Went with a blend of the two across the fa, but generally leaned towards the cooler side, more in line with the GFS. Temps start to warm up on Sunday as the upper trough dampens and flow becomes more zonal. Still anticipate dry conditions to persist with limited forcing in place. Scattered rain showers will return early on Monday with another approaching cold front and upper trough digging into the Mid- Atlantic. The GFS currently moves the precip out by end of morning, so started decreasing PoPs in the afternoon. Afterwards, anomalously low 850mb temps begin to advect into the fa, cooling off surface temps rapidly heading into Monday night. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/... Generally VFR conditions are expected at the start of the overnight period, but these conditions will deteriorate after 06Z, with fog and stratus expected to develop. MVFR to IFR ceilings and visibilities appear very likely for all TAF sites (though KDAY may be more MVFR than IFR). A period of LIFR conditions, possibly including dense fog and low stratus, appears possible at KLUK/KILN/KCMH/KLCK during the 08Z-12Z time frame. This set of TAFs has been adjusted to include some lower visibilities and ceilings than the last update. Visibilities should improve after 12Z, but low ceilings may persist for another few hours. VFR conditions are expected for all TAF sites by late morning or early afternoon. Some showers and thunderstorms are expected by mid to late afternoon, but with uncertain timing and only scattered coverage. Thus, a VCSH will be included in the TAFs, with specifics left for later updates. OUTLOOK...Thunderstorms will be possible at times through Thursday. MVFR conditions are possible again on Wednesday morning. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...JGL NEAR TERM...Hatzos/JGL SHORT TERM...JGL LONG TERM...Clark AVIATION...Hatzos
Area Forecast Discussion
National Weather Service Marquette MI
736 PM EDT Mon Aug 31 2020 .SHORT TERM...(This evening through Tuesday) Issued at 352 PM EDT MON AUG 31 2020 Water vapor satellite this afternoon shows a distinct dry punch aloft over Wisconsin and the western UP, this associated with a strong negatively-tilted mid-level short wave that is lifting northeastward across the western UP and Lake Superior. At the surface, this takes the shape of a narrow trough accompanied by a tight wind shift as evidenced by south winds at Passage Island (east end of Isle Royale) and NW winds at Rock of Ages (west end of Isle Royale). Strong fgen is providing maple lift for showers moving across the area. Initially, these were in a broader, more stratiform area. However in the past hour or so some scattered heavier showers have developed over western Marquette County where SPC Mesoanalysis indicates up to 250 J/kg MUCAPE. Even the most generous HRRR sounding wrt instability keeps ELs below the hail growth zone, and with cloud-phase satellite showing only very little ice growth, felt ok keeping thunder out of the forecast. However, some briefly heavier rainfall rates will be possible the next couple of hours. This evening, precip will clear out from west to east as the front races through. Initially skies will be clear, allowing for some cooling. However, satellite and models show a thick patch of cirrus racing in from the west that will move over the area by late evening, inhibiting cooling somewhat. Still, given the cool air aloft behind this front it will be a seasonably chilly night (lows in the 40s interior and 50s lakeshores). Despite today`s rainfall, think that we will maintain a few kts of gradient wind which, along with this cirrus, should prevent much if any fog from forming. Tomorrow, temps begin warming aloft again, from about 8 C in the morning to about 11 C by late afternoon at 850 mb. However, this comes as the next short wave (this one much more strung out) bring more mid-level cloud cover in by afternoon, keeping temps from warming too much. Highs should make it into the low 70s across the board. .LONG TERM...(Tuesday night through Monday) Issued at 355 PM EDT MON AUG 31 2020 At the start of this forecast period, Upper Michigan will be sitting in between two bouts of precip to the NW and SE. The one sliding northeastward to the southeast of the area may skim portions of the far southeastern U.P., with this round courtesy of being triggered by the leading edge of an upper trough axis swinging overhead. To the NW, that precip is more directly associated with the trough axis itself as an upper jet moves in. This jet/trough looks to weaken as it crosses the Upper Great Lakes, with not a whole lot of atmospheric moisture accompanying it, thereby reducing more widespread precip chances with this system. Brief benign period then occurs before the next, potentially more robust system knocks on the door, although similar to how the models have been handling these more fall-like system tracks as of late, may be a bit overdone, particularly the GFS. Nonetheless, it`ll be windy with some rain in the area, but the extent of the wind and rain is yet to be seen. All of the models are in agreement in intensification of the low, but differ on its track (i.e. if further north, less rain chances, lower wind speeds). Stay tuned, particularly those with marine interests (see below). In the extended period, the pattern looks to remain unsettled with repeated visits from shortwaves and other disturbances, keeping the chances for rain somewhat persistent. Not a washout every day by any means, but just nuisance-type shower activity is what is currently looking to occur. As for temps, it will wobble between near to a few degrees below normal through the entire forecast period, with the warmest day likely happening on Wednesday. If a fan of the warmer temps, enjoy it while it lasts as early next week could usher in much cooler weather. Expect 40s and 50s for lows through the period. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 732 PM EDT MON AUG 31 2020 VFR conditions expected at all terminals through the forecast period. Southwest wind gusts of 20-25 knots could develop in the afternoon, mainly at KIWD and KCMX. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 422 PM EDT MON AUG 31 2020 The active pattern continues. A sharp trough/occluded front is moving quickly northeastward across the lake this afternoon. Southerly winds out ahead of it have been in the 20-30 kt range, now confined to the eastern half of the lake, while immediately behind the trough there has been a quick wind shift to westerly and an hour or two period of gales. Have observed gale force gusts at the western lake buoy, Rock of Ages, and Houghton this afternoon, however winds have already relaxed back into the 20-30 kt range at all three of these sites. Winds will continue to relax into the 15- 20 kt range this evening and through the day tomorrow. Winds, particularly across the western portions of Lake Superior, will be on the increase late tomorrow night into early Wednesday with a few gusts to gale-force possible. Elsewhere across the lake, gusts look to generally range in the 25 to near 30 knot range. By early Thursday, more widespread gale-force gusts look likely, spreading from west to east as the day progresses. However, there is some uncertainty as to just how high these gusts will get given some model discrepancies in the track of the low pressure system responsible for these winds. Regardless of these finer details, expect gales for this time period, tapering off by late Thursday into early Friday. For the first half of the weekend, gusts should top out around 20 knots, with the next system of interest potentially ushering in higher winds toward the tail end of next weekend. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Beach Hazards Statement until 9 PM EDT this evening for MIZ014. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...RJC LONG TERM...lg AVIATION...Voss MARINE...RJC/lg
Area Forecast Discussion
National Weather Service Reno NV
306 PM PDT Mon Aug 31 2020 .SYNOPSIS... Temperatures remain near normal through Tuesday. Winds turn easterly this evening into Tuesday helping to ease smoke impacts for many spots for at least the next couple days. An unusually warm air mass takes hold mid-week through the Labor Day weekend with temperatures likely to reach near record highs starting on Thursday. Very low chances for thunderstorms return to the Sierra next week. && .DISCUSSION... It looks like we will finally see a better scouring of smoke/haze in western and west-central Nevada starting later this evening, with the Sierra possibly having to wait until late tonight or Tuesday to see the same. Before late evening, west-northwest flow for the Sierra into western NV may allow some additional smoke transport to begin; however, after about 9 PM north to northeast flow deepens such that additional smoke transport should be cutoff and keep air quality from deteriorating too badly as compared with previous nights. On Tuesday, haze should decrease or even dissipate for improved visibility as solid easterly flow is expected to keep most smoke in California. Speaking of California, it may take longer than western NV to scour smoke/haze in the Tahoe area as lighter winds overnight could allow for smoke to remain in the Basin/Martis Valley until mixing ensues on Tuesday. For Mono County, a similar situation is possible although easterly flow may keep a small area under the smoke gun in and to the west of the Antelope Valley. Temperatures will remain around average through Tuesday before we begin a substantial warm-up heading into the Labor Day weekend. Overnight lows in valleys will be able to cool off efficiently for at least the next few nights as winds diminish and the dry air mass settles in. For mid-week through the Labor Day weekend, an unusually strong area of high pressure will build across much of the western US including CA-NV. Deterministic GFS/ECMWF solutions continue to show heights rising to 595-600 DM with very warm positive 2 meter temperature anomalies. The MEX guidance still shows multiple days (starting Thursday) at or above 100 degrees for western NV cities, with the MEX pushing 90 degrees for Truckee and South Lake Tahoe. Our latest day to hit 100 degrees at KRNO is September 4th, which was set last in 2017. So, if the guidance holds, we would be looking at multiple days for records including the latest day to reach 100 degrees in a year. The one consolation will be the dry airmass and the shortening days which will allow overnight temperatures to at least cool back into the 40s Sierra valleys and 50s to mid 60s for warmer lower valleys. Be prepared for unusually hot afternoons this Labor Day Weekend. As far as thunderstorms, normally this magnitude of heat will generate thunderstorms eventually as daily mixing and weak moisture advection allow for enough instability to overcome the very warm temperatures aloft. The first hint at storms is this weekend, but probabilities remain low suggesting they will be very isolated and mainly confined to the Sierra. -Snyder/Hohmann && .AVIATION... * Northeasterly flow behind a passing cold front is bringing slowly improving visibility with less smoke to many areas today. Expect this trend to continue tonight into Tuesday following latest HRRR Smoke guidance. Still a bit of haze so slant-wise visibilities will remain iffy. Areas of MVFR smoke conditions expected in the Sierra (e.g. TRK, TVL, MMH) through this evening but those should clear out to VFR by daybreak Tuesday as NE flow increases. * Most areas should remain VFR Wednesday with N/NE flow however some sneaky westerlies could bring haze/smoke back into Sierra spots such as SVE, TRK, TVL late in the day. * Unusually strong ridge of high pressure overspreading the region for the coming holiday weekend will bring near-record temperatures and isolated mountain t-storms or buildups. Some density altitude considerations possible as well. -Chris && .FIRE WEATHER... * Gusty N/NE winds will continue into this evening. With unusually low humidity, some spots of critical conditions are possible in wind prone areas of the Eastern Sierra and into the Highway 95 corridor. Not widespread nor long enough duration for warnings but still awareness should be elevated into this evening. * Humidity recoveries should be dramatically better for much of W Nevada and NE California (+30% in zone 423 where MaxRH was as low as 14% this morning!). Parts of Tahoe and the Eastern Sierra however will have similar or slightly lower MaxRH values vs last night. Gusty NE winds will persist overnight on mid-slopes and ridges around the region, which could impact ongoing fires. Flow relaxes Tuesday morning after daybreak. * Still looking at a rather impressive heat wave starting Thursday and lasting through the holiday weekend. Near record daytime temps are likely especially Saturday into Monday. This is also when guidance is showing larger areas of high Haines with dry/unstable conditions. This could yield plume dominated fire behavior even with only typical zephyr breezes. Isolated t-storms and buildups are expected over the high terrain each afternoon. -Chris && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$ For more information from the National Weather Service visit...