Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/05/20

Area Forecast Discussion
National Weather Service Denver/Boulder CO
927 PM MDT Tue Aug 4 2020 .UPDATE... Issued at 900 PM MDT Tue Aug 4 2020 Enough instability exists across the I-25 corridor along with a weak shortwave trough for showers and storms to continue this evening. They will be sub-severe as the instability and shear are not sufficient to generate strong enough updrafts. PoPs were kept until midnight as the storms are expected to dissipate around that time. Considering how well the storms in Larimer and Weld Counties have held together along with the storm complex in southeast Wyoming, it is not out of the question that a few showers and storms persist past midnight near the Colorado/Wyoming border. Otherwise, the forecast remains on track. && .SHORT TERM...(This evening through Wednesday) Issued at 229 PM MDT Tue Aug 4 2020 Still expecting a fairly active afternoon. Best chance of severe thunderstorms will be along and east of the I25 corridor this afternoon and evening. ML CAPE 1500-2000 j/kg with Bulk Shear 35-45 kts this afternoon. Airmass is still capped over the plains, but that should be done shortly. Storms fairly well from northwest to southeast across the forecast area. Latest HRRR still develops the strongest thunderstorms out of WY after 3 pm, and into the Denver, Castle Rock and Limon areas 5-7 pm. Can`t rule out some outflow boundaries triggering off more thunderstorms further west. Large hail and damaging winds the main threat, but sufficient shear for a short lived tornado or two. Most of the thunderstorm activity should be done by 10 pm with some lingering showers through midnight. The upper ridge will be centered along the AZ/NM border this afternoon will shift more into the eastern NM by Wednesday afternoon. This will allow for the northwesterly flow aloft to have more of a westerly component to it on Wednesday, The ML CAPE and Bulk Shear values are fairly similar for the northeast CO on Wednesday. SPC has northeast CO in another Marginal/Slight Risk category Wednesday. Only difference, is that the focus may shift more to the northeast plains. .LONG TERM...(Wednesday night through Tuesday) Issued at 115 PM MDT Tue Aug 4 2020 Scattered to numerous showers and thunderstorms are expected across the eastern plains early Wednesday evening. With MLCAPE of up to 2000 J/kg and Bulk shear near 40 knots some of the storms are expected to be strong to severe. Isolated showers and storms will remain possible into the early evening along the Front Range. Except for a few showers over the eastern plains, all the convective activity is expect to dissipate or be east of the area by midnight. The upper level ridge axis will drift east over the Central Rockies on Thursday. A drier west/southwest flow aloft will prevail under this pattern. Precipitable water values fall below a half inch across the higher terrain and Front Range. A surface trough sets up over eastern Colorado Thursday afternoon. To the east of this, southeast winds will transport low level moisture into the area with dew points staying the 50s. This will lead to MLCAPE of 2000 J/kg. Bulk shear will be a little less, around 35 knots. Still could see some strong to severe storms here through the early evening. With the drier air in place, high temperatures are expected to climb into the lower 90s along the Urban Corridor. On Friday, the upper level ridge continues to slowly drift eastward and will be centered over the Central Plains. This will put Colorado under a southwesterly flow aloft. The surface trough is expected to be near the eastern Colorado border with Nebraska and Kansas. Dry westerly flow across the area is expected to result in dry conditions and warm temperatures. Highs should reach the lower to mid 90s for most of northeast Colorado. A few high based showers and storms can`t be ruled out over the higher terrain. If this convection forms, it will produce more wind than rain. For the weekend, the upper level ridge over the Central Plains Saturday will retrograde west over the Center Rockies Sunday due to a trough tracking across southern Canada. For our weather, dry west to southwest flow aloft and at the surface will prevail. This is expected to keep very warm and dry conditions in place. Dry conditions will persist into early next week as the upper level ridge remains parked over the region. Highs will continue to be very warm with 90s over northeast Colorado. Chances for precipitation continues to be very low. It anything forms, it will be high based and produce little if any rainfall. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 900 PM MDT Tue Aug 4 2020 VFR is expected through Wednesday evening. There remains some instability this evening which is leading to a few showers and storms developing across northern Colorado. These showers and storms are not expected to impact any of the terminals but it can`t be completely ruled out. Otherwise, southeasterly winds will veer toward drainage tonight. Tomorrow, winds will veer toward to northeast and will increase in the afternoon. Showers and storms may develop during the afternoon and early evening which could bring strong winds and hail to the terminals. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Danielson SHORT TERM...Cooper LONG TERM...Meier AVIATION...Danielson
Area Forecast Discussion
National Weather Service Dodge City KS
615 PM CDT Tue Aug 4 2020 ...Updated aviation discussion... .SHORT TERM...(This afternoon through Wednesday night) Issued at 1200 PM CDT Tue Aug 4 2020 Midlevel clouds across the eastern zones as of midday will continue to dissipate into a cumulus field through this afternoon, beneath continued NWly flow aloft. SE winds will continue to increase through this afternoon, gusting 30-35 mph at times. Temperatures will continue to trend well below normal, in many zones just getting close to 80. SW zones will be well into the 80s. All zones will be dry through about 7 pm this evening. Scattered convection is expected to develop along the Front Range this afternoon, with NWly flow subsequently spreading the activity toward SW KS tonight. Latest HRRR iterations and other CAMs suggest storms will be along the CO/KS border by 8 pm. The highest risk of large hail/damaging winds will be across these far western zones (roughly west of US 83), and relatively early this evening per SPC`s 1630z outlook. With time and with eastward extent, any discrete storms will evolve into clusters, and also become strongly elevated, with 12z NAM progging near zero surface based CAPE in SW KS tonight. With modest elevated CAPE/NW flow aloft, expect some activity to survive into at least the central zones by midnight. With an unfavorable environment with eastward extent, confidence is less say east of US 283. Pops are in the likely category for much of the western/central zones tonight. Short term models suggest stratus will fill in behind the storms Wednesday morning, with sunrise temperatures once again in the upper 50s and lower 60s. Below normal temperatures will continue Wednesday afternoon, ranging from the lower 80s east, to mid 80s SW zones. Daylight Wednesday will be dry, with lighter SEly winds. A strong 594 dm upper high is forecast to be centered near Midland, Texas Wednesday evening. More weak shortwaves rounding the northern periphery of this high will probably encourage more nocturnal thunderstorms late Wednesday night/early Thursday morning. Pops are mainly in the chance category after midnight, favoring the E/NE zones per the NAM/ECMWF solutions. .LONG TERM...(Thursday through Tuesday) Issued at 143 PM CDT Tue Aug 4 2020 The balance of the long term will be quiet and dry as the subtropical upper anticyclone expands its influence across the plains. Temperatures will begin showing a warming trend Thursday, with max readings in the upper 80s and lower 90s. Friday will be noticeably hotter, with 12z ECMWF building a 594 dm ridge centered over SW Oklahoma. NBM`s max temp grid of upper 90s was accepted for Friday, with some triple digits along the Oklahoma border. Saturday promises to be at least as hot, before models forecast the upper high to ever so gradually weaken Sunday through Tuesday, with a few degrees of cooling each day. NBM sprinkles some slight chance pops here and there in the long term. Did not remove them, but the prospects of organized rainfall/convection appear minimal with little if any forcing. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 615 PM CDT Tue Aug 4 2020 There is some uncertainty as to the track and coverage of thunderstorms moving out of eastern Colorado this evening. Most of these storms may track across far southwest Kansas into the OK/TX Panhandles. Additional thunderstorms could develop across portions of central and southwest Kansas toward south central Kansas between 04z-06z before tracking into Oklahoma later tonight. Given the uncertainties, will carry VCTS at the terminals but will hold off on any prevailing coverage at this time. There is also some small potential for MVFR cigs to develop later tonight across southwest Kansas. && .PRELIMINARY POINT TEMPS/POPS... DDC 59 84 63 88 / 70 10 50 0 GCK 59 83 62 88 / 70 10 40 0 EHA 61 87 63 92 / 60 10 30 10 LBL 61 88 64 94 / 70 10 30 10 HYS 59 81 63 86 / 30 10 30 10 P28 61 82 65 91 / 60 20 40 10 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Turner LONG TERM...Turner AVIATION...Gerard
Area Forecast Discussion
National Weather Service Goodland KS
1000 PM MDT Tue Aug 4 2020 .SHORT TERM...(This evening through Wednesday night) Issued at 205 PM MDT Tue Aug 4 2020 A Severe Thunderstorm Watch is in effect through 9 PM MDT for Yuma, Kit Carson, and Cheyenne Counties in Colorado as well as Sherman, Wallace, and Greeley in Kansas. 500mb RAP analysis and water vapor imagery showed a ridge prevailing over the western half of the country with a trough dominating the eastern CONUS. This pattern placed the region under northwest flow, with a shortwave approaching from Wyoming. Earlier convection cleared the area by mid morning, leaving cloud cover across the eastern part of the region. At 2:00 PM MT, temperatures ranged in the 70s to low 80s, with breezy south winds gusting around 30 mph along the Colorado border. A line of weak storms had also developed over the northeastern CWA. As the aforementioned shortwave moves towards the region, southerly flow at the surface filters moisture into the High Plains. Diurnal heating will aid thunderstorm development along the Front Range during the afternoon hours. With 40 to 50 knots of shear, MLCAPE around 2,000 J/kg near and west of the Colorado border, and steepening lapse rates, scattered severe thunderstorms are expected, with the best chance along and west of the Colorado border. Severe storms are also possible east of this line; however, coverage would be more isolated. Storms developing along the Rockies should gradually work their way east/southeast through the evening hours. Supercells will be possible initially, with a clustering storm mode favored in the evening. Large hail, damaging winds, and locally heavy rainfall resulting in flash flooding are all hazards. All of that being said, today`s cloud cover has had an impact on daytime heating thus far (especially in the east) which may have an effect on storm chances through the evening. Currently, it looks as though storms will exit the region to the southeast around midnight. Temperatures fall into the mid 50s to low 60s with partly to mostly cloudy skies tonight. Temperatures climb into the mid to upper 80s on Wednesday as the upper ridge builds east into the Plains. Another round of thunderstorms is forecast from the late afternoon into the evening as a shortwave works through the northwest flow around the northeastern periphery of the ridge. Storms should develop along the Rockies once again and move east across the area through the evening. Scattered severe storms will be possible along and west of a line from Flagler, Colorado to Haigler, Nebraska. Isolated severe storms could spread east from this line into adjacent northwest Kansas and southwest Nebraska. Large hail and damaging winds will be the main threats. Locally heavy rainfall may also occur. Expect low temperatures in the upper 50s to low 60s. .LONG TERM...(Thursday through Tuesday) Issued at 229 PM MDT Tue Aug 4 2020 At the beginning of the forecast period on Thursday, forecast guidance shows the Tri-State region under an upper air ridge which is between an upper air low in the Pacific Northwest and another low over eastern Ontario. This ridge is amplified by an upper air high over southwestern TX and Mexico. This ridge persists over the area into Friday, but models show that the Pacific Northwest low begins to move east across Canada suppressing the amplitude of the ridge. There is some model discrepancy as the ECWMF has this Canadian low a little more east than where the GFS has this low placed. This pattern continues until Saturday when an upper air trough associated with the Canadian low moves into the Northern Plains and pushes the ridge east of the Tri-State area leaving a generally westerly flow aloft starting Sunday. This upper air pattern continues for the remainder of the forecast period. At the surface, model guidance shows warmer temperatures returning to the Tri-State area due to the ridge aloft and winds coming from the south through the weekend. Thursday evening shows a slight chance of isolated showers and thunderstorms associated with an upper level shortwave moving through the ridge for the areas west of the CO/KS border. Areas along and east of the CO/KS border expect to see a slight chance of showers and thunderstorms associated with a upper level shortwave troughs on Saturday and Tuesday. There is also a slight chance of showers and thunderstorms possible for areas east of Hwy 27 on Sunday and Monday as well due to upper level shortwave troughs passing through the area. As the warmer temperatures return during the forecast period, there is a chance for possible fire weather conditions on Friday for the western portions of Yuma, Kit Carson, and Cheyenne counties of CO as RH values are expected to be below 20%. However, current model guidance shows that expected wind gust values for Friday do not support elevated fire weather conditions. High temperatures for the Tri-State area are expected to warm into the upper 80s by Thursday followed by highs in middle 90s through the weekend and highs in the lower 90s on Monday and Tuesday to finish the forecast period. Low temperatures will remain in the lower to middle 60s across the Tri-State area during the forecast period with the exception of Monday and Tuesday when the CO counties of the Tri-State area are expected to see lows in the upper 50s. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1000 PM MDT Tue Aug 4 2020 KGLD, vfr conditions expected from taf issuance through about 09z with winds from the south under 10kts. From 10z-14z there is medium confidence of stratus clouds and sub vfr cigs developing over the terminal some some light reductions in visibility. A brief period of south winds around 12kts with some higher gusts expected from 22z-00z. After 00z there is medium confidence in an organized cluster of strong to potentially severe thunderstorms moving through or near the terminal somewhere in the 03z-06z timeframe. Erratic wind gusts and potentially very heavy rainfall are possible which could produce sub vfr conditions. KMCK, vfr conditions expected through the period. Winds through the period from the south to southeast at speeds 10kts or less. Similar to KGLD there is medium confidence in an organized cluster of strong to potentially severe thunderstorms impacting the terminal sometime in the 03z-06z timeframe. There is a bit higher confidence in thunderstorms actually impacting the terminal so have added some sub vfr visibility reductions in moderate rain. Erratic wind gusts likely as it moves through. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...JBH LONG TERM...076 AVIATION...99
Area Forecast Discussion
National Weather Service North Platte NE
656 PM CDT Tue Aug 4 2020 .SHORT TERM...(This evening through Wednesday night) Issued at 240 PM CDT Tue Aug 4 2020 A weak shortwave is evident late this morning across northern WY per WV imagery. This will slowly track southeast through the afternoon. Mid-level lift and weak WAA continues to aid in some scattered elevated showers and isolated thunder. A leeward surface trough will be located across eastern WY southward to near the Denver metro by late this afternoon. Persistent upslope flow and lift associated with the shortwave will lead to the development of scattered thunderstorms near the surface trough. These will attempt to push eastward into the Nebraska Panhandle early this evening. Sufficient instability should be present in this area along with 35-40 kts of 0- 6km bulk shear. This should allow for storm organization with a few supercells producing large hail possible initially. The last several runs of the HRRR have brought the activity about as far east as Highway 2 (near Ogallala) by mid evening. After mid-evening convection quickly diminishes as convection tries to push farther east. This could be due to earlier cloud cover and less instability with eastward extent. There is at least some chance that convection could become elevated and continue moving east/southeast through the night, but models have been struggling with this scenario. In fact, most of the HREF members have activity done by late evening in our area. The low-level jet really isn`t very strong tonight and there is a lack large scale lift. For these reasons will lower pops some tonight and focus chances mainly this evening across portions of west central and southwest Nebraska. Another round of convection is expected to develop along the leeward surface trough across eastern WY into northern CO Wednesday afternoon. Most models actually have more robust development tomorrow (compared to today). Better instability also exists farther east with activity moving farther east Wednesday evening. Activity Wednesday evening could be supported by a better shortwave which is indicated in the NAM. 0-6km shear is once again sufficiently strong (30-40 kts) for storm organization. Otherwise warmer temperatures (mid to upper 80s) expected Wednesday as heights slowly rise with the upper ridge building northward. The axis of the ridge will be oriented south to north across the Rockies. Low-level moisture will also be slowly increasing with dew points rising into the lower 60s. .LONG TERM...(Thursday through Tuesday) Issued at 240 PM CDT Tue Aug 4 2020 Upper level ridge axis gradually shifts eastward and will be centered along the western High Plains by Saturday morning. As heights continue to rise and the flow aloft decreases, so will the scattered thunderstorm chances. Temperatures will continue to warm with highs in the 90s most areas by this weekend. Rather humid conditions expected as well with upper 60s to lower 70s surface dew points working there way to the west into western Nebraska by Friday into Saturday. The ridge may flatten a little by early next week as a stronger shortwave with flow aloft increasing from the west a bit. A weak cold front could also move southward into the area by Monday which could provide focus for scattered storms once again. Highs cool slightly by early next week into the mid 80s to around 90F. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 635 PM CDT Tue Aug 4 2020 VFR conditions expected to prevail at both TAF sites through the period. Backing winds are expected at VTN into tomorrow afternoon with the approach and passage of a cool front. Watching convective debris north of LBF, but left out mention for now with lower confidence in its progression southward. Even if this convective debris does make it into LBF, CIGs are still expected to remain VFR. Don`t anticipate the need to include even VCTS at LBF with the thunderstorm activity to the northwest expected to diminish over the next couple hours. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Taylor LONG TERM...Taylor AVIATION...Brown
National Weather Service Morristown TN
957 PM EDT Tue Aug 4 2020 .UPDATE... EVENING UPDATE. && .DISCUSSION... A weak boundary is located across the central valley this evening with a few convective rain showers. These showers are forecast to dissipate with the loss of daytime heating and a stabilizing boundary layer which is what CAMs such as the HRRR indicate. With satellite imagery already showing a clearing sky for most areas, fog is expected to develop across river valleys and areas that received rain this afternoon. Forecast continues to progress as expected and only made minor adjustments to hourly forecast elements. JB && .AVIATION... 00Z TAF DISCUSSION. Showers and thunderstorms expected to dissipate after sunset with clearing conditions. Fog is forecast to develop along river valleys, and this will impact TRI. Guidance is in agreement with IFR/LIFR fog late tonight and early Wednesday morning near TRI, so included in the TAF for TRI. Fog development is less likely at TYS and CHA, but is possible with recent rainfall this afternoon. Included MVFR fog potential for CHA and TYS, but lower vis will be possible. Additional showers and thunderstorms will be possible at all TAF sites Wednesday afternoon, but the probability is low enough to include in a Prob30 group for tsra. JB && .PREV DISCUSSION... /ISSUED 329 PM EDT Tue Aug 4 2020/ SHORT TERM...(Tonight through Wednesday)... Scattered showers continue across the TN valley this afternoon in part due to a strengthening jet entrance region over the southern Appalachians in response to Isaias phasing with a large scale trough anchored over the Great Lakes region. Forecast soundings from across the CWA showed a notable warm layer in place around 15,000 ft or so earlier today, and this was forecast to essentially remain in place through the afternoon and evening hours. With meager instability in place updraft maintenance has struggled, with few showers on the whole extending much beyond the 15-16k ft AGL mark. Showers that did manage to break through that warm layer have gone on to produce some brief gusty winds, supported by DCAPE values in the 800 J/kg range. However lack of robust updrafts means that there hasn`t been much to work with in regards to large precipitation cores and resulting damaging winds. If there were an area to be leery of through the evening it would be the TN valley between the Knoxville and Chattanooga metro areas and along the I-75 corridor where sun has been most prevalent. This area has the best overlap of instability and DCAPE values. Tonight, showers will largely follow a diurnal pattern, dying off quickly after sunset this evening. A cold front is draped NE-SW across the TN valley this afternoon and will shift east of the Appalachians late tonight. However, there isn`t a strong push of dry air behind this. Thus with the lack of strong dry air advection and the scattered rain from today, think that fog and low clouds will be somewhat prevalent again late tonight into the pre-dawn hours tomorrow. The forecast accounts for this. Tomorrow, expect another round of showers, though mostly over the mountains, as the region remains beneath cyclonic upper flow as well as upslope flow across the mountainous area. High res guidance does show rain chances extending into the valley later in the day, but lesser chances are warranted there. CD LONG TERM...(Wednesday Night through Tuesday)... The region will remain underneath persistent longwave cyclonic flow through the late week and into the weekend. Several perturbations will likely rotate through this flow but forecasting timing is of low confidence. A moist and unstable airmass will be in place each day this week which results in afternoon showers and thunderstorms Thursday, Friday, and Saturday afternoon. Temperatures will remain near normal Thursday through Saturday. Start to see a pattern change during the late weekend period as a ridge of high pressure aloft begins to nudge north and east out of the plains. Upper level heights will increase in response to this. Afternoon showers and thunderstorms will be possible. Temperatures should warm in response to increased heights aloft. Early next week, the ridge will begin to break down in response to a trough moves out of the Pac NW. Low level winds will veer toward the southwest advecting low level moisture northward. Lowered heights and moisture should contribute to afternoon showers and thunderstorms Sunday through Tuesday. The lack of any upper level support or low level boundaries should mean that strong to severe potential will remain very low. Temperatures will continue to be above normal for early next week. Highs in the lower 90s are forecast. This combined with higher dewpoints may allow heat index values to approach 100 degrees. Diegan && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 69 89 69 91 70 / 10 30 10 30 10 Knoxville McGhee Tyson Airport, TN 67 88 68 89 68 / 20 40 20 50 20 Oak Ridge, TN 67 87 66 88 68 / 20 30 10 40 10 Tri Cities Airport, TN 62 85 63 86 65 / 10 50 30 60 20 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$