Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/17/21

National Weather Service Sioux Falls SD
1028 PM CDT Thu Sep 16 2021 .UPDATE... Issued at 931 PM CDT Thu Sep 16 2021 Quick update this evening on the ongoing convection risks. We`re beginning to see elevated post frontal convection from across an area from Gregory to Huron and Watertown. These storms are forming in an area of moderate mid-lvl lapse rates, MUCAPE lifted from the 700 mb surface near 1500 J/KG, and somewhat modest effective shear around 30 knots. HRRR/RAP continue to pick up on this development reasonably well, with the HRRR being a bit slow as usual. We`ll continue to see rapid development over the upcoming two hours along this axis given expansive ACCAS field, and have adjusted PoPs accordingly. The questions overnight is how far east activity will remain strong or severe. The area with the greatest potential for more organized wind, will be with a thunderstorm cluster moving into south central South Dakota where there is a higher degree of dry air below the lifting layer further east, and only a modestly stable boundary layer immediately post frontal. Further north towards highway 14, feel the main threat would be from marginally severe hail at times given more stable boundary layer. While lapse rates and MUCAPE values trend downward as you reach I-29 overnight, even weakening thunderstorms could still pose a marginal severe wind risk into western Minnesota and Iowa given better perpendicular alignment of 700 mb flow to the orientation of the convection and that modest DCAPE layer. && .SHORT TERM...(This Evening through Friday) Issued at 310 PM CDT Thu Sep 16 2021 Breezy pre-frontal winds have occasionally gusted between 35-45 mph so far today with a gradual decrease expected into the evening hours. This is ahead of an incoming cold front that currently runs from roughly Webster, SD to Valentine, NE. This boundary is moving into an environment that very well may stay capped to any surface parcels although occasional forecast soundings show at least minor hints that surface development is possible with north central Nebraska standing the best chance. Should surface based development occur along the front through the early evening hours (unlikely), between 2000-2500 J/kg of MLCAPE and around 40 kts of deep layer shear would support supercell structures and all modes of severe weather. What seems far more likely to occur is CI waits until closer to mid evening as a subtle wave ejects out of the Nebraska Panhandle with parcels originating on a boundary in the 800:700 mb layer. This activity will have similar values of MUCAPE initially (decreasing into the overnight) along with 30-40 kts of effective shear (increasing as you move further post- frontal). In terms of hazards with any elevated storms... initial updrafts may pose a threat of large hail up to 1.5 inches in diameter and may very briefly take on quasi-supercell characteristics. Upscale development should rather quickly occur with updraft interference reducing the hail threat. With DCAPE values between 1000-1400 J/kg, should transition to more of a damaging wind threat up to 70 mph with any organized clusters, particularly ones that can organize with more of a north to south orientation more favorably aligned perpendicular to the 700 mb flow. Corfidi vectors look to keep enough progression and 3 hr flash flood guidance between 2-3 inches should keep the excessive rainfall risk on the lower end. With this said, PWATs do peak around the 90th percentile of climatology so any sustained training could result in localized amounts in excess of 2 inches. This is further supported by the LPMM from the HREF. All of the above mentioned risks are captured by a Slight/Marginal from SPC and Marginal from WPC. Could still see some lingering showers across NW IA around daybreak Friday before the front clears our forecast area by mid day. Behind the front, cool surface high pressure will result in a rather fall- like day with temperatures in the mid 60s to mid 70s. .LONG TERM...(Friday Night through Thursday) Issued at 310 PM CDT Thu Sep 16 2021 Upper level ridging builds and moves east through the weekend keeping our region void of any precipitation and with temperatures working back to the warm side of normal. Deterministic GFS continues to run on the warm side and generally above its ensemble mean and thus will hedge away from this solution. Generally expect mid 70s to mid 80s Saturday with more widespread 80s to lower 90s for Sunday. Should also see a noticeable southerly wind through the weekend. Amplified troughing slides across the Northern Plains for the first half of the work week. Depending on eventual timing, could very well see some additional convection chances for the second half of Monday into Monday night with locations near/east of I-29 currently most favored. Cooler temperatures settle in by the middle of the week with 60s to lower 70s for Tuesday and Wednesday. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1024 PM CDT Thu Sep 16 2021 Convection will continue to track east overnight, impacting most of the region. Some stronger winds are possible along and south of Interstate 90, with marginally severe hail at times. Localized MVFR ceilings may briefly accompany the elevated frontal passage through daybreak, but generally we may continue to see VFR conditions. Based on observations further northwest, also possible to see a period of 30 knots winds briefly Friday morning. Skies will take a bit of time to clear through the day on Friday, with winds remaining quite breezy. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ UPDATE...Dux SHORT TERM...Kalin LONG TERM...Kalin AVIATION...Dux
Area Forecast Discussion
National Weather Service Goodland KS
638 PM MDT Thu Sep 16 2021 .SHORT TERM...(This evening through Saturday) Issued at 340 PM MDT Thu Sep 16 2021 At the start of the short term period, the CWA looks to have a mostly west-southwesterly flow aloft with an upper air trough to the north-northwest and an eastward moving subtropical trough to the south on Thursday. Also worth noting is a shortwave disturbance moving through the base of the first trough during the late evening and overnight hours. At the surface, areas around the NE border and adjacent northern Yuma county may see a chance for isolated showers and possible severe thunderstorms this evening (starting ~00Z) with an approaching cold front associated with the aforementioned upper air disturbance. Strong winds look to be the primary hazard with an inverted-V RAP forecast sounding seen this evening in northern Yuma county as storms may possibly be high based. Model based DCAPE values this evening look to be at or over 1500 J/kg this evening in these areas with effective bulk shear approaching 40 kt. SBCAPE and MLCAPE values staying are not expected to be too high though (around 500 J/kg) with some CIN seen in the area to overcome. Thursday`s overnight lows expect to range between the upper 40s and and lower 60s. On Friday, the CWA sees westerly flow during the day as both upper air troughs look to move eastward with a ridge building over the Rockies in the evening hours. At the surface, breezy to windy conditions look to continue from Thursday night into Friday morning behind the cold front though there appears to be little chance for precipitation. Some models show wind gusts potentially reaching 40 mph in some areas. Model guidance also shows that cloud cover sticking around for most of the day particularly in the southern portions. Max temps on Friday were decreased a bit as there may not be as much daytime heating. The strong northerly winds look to veer and lessen a bit going into the evening hours as models show a 1020mb surface high moves over the CWA overnight. Friday`s daytime highs currently look to be in the middle 60s to lower 70s with the overnight lows staying in the 50s. Going into Saturday, the upper air ridge looks to make its way over the CWA. This will bring warmer daytime highs to CWA at the surface in upper 80s to lower 90s range with mostly sunny skies during the day. While minimal chances for precipitation are seen again, there may be some elevated fire weather concerns west of the CO border during the afternoon hours with minimum RH values just under 20% are possible. The limiting factor for fire weather concerns on Saturday looks to be the winds with forecasted maximum wind gust values not reaching criteria in these areas. Overnight low temperatures on Saturday range between the middle 50s and middle 60s. .LONG TERM...(Sunday through Thursday) Issued at 154 PM MDT Thu Sep 16 2021 At the start of the period, southwest flow prevails aloft between an upper ridge over the eastern CONUS and a trough entering the Pacific Northwest. This pattern shifts eastward on Sunday, with the ridge still having influence over our area, leading to dry and warm weather. This changes on Monday however, when the west coast trough advances into the Plains, sending a cold front through the region. The disturbance brings chances for rain showers to the forecast during the afternoon and nighttime hours. Will need to monitor for some breezy north winds behind the boundary as well. The frontal passage is anticipated to bring a nice cool down in time for Tuesday, with dry weather under surface high pressure. The upper trough exits the Plains midweek and is quickly replaced by a ridge. As a result, current forecast calls for dry and warming conditions on Wednesday and Thursday. The temperature forecast during the long term period is subject to change due to uncertainty in the timing of Monday`s front. As it stands, highs should fall from the upper 80s/low 90s on Sunday to the upper 60s/low 70s for Tuesday. Temperatures warm on Wednesday (upper 70s/low 80s) and Thursday (80s). Low temperatures take a dip, falling from the 50s/60s Sunday night to the 40s for much of the area for the remainder of the period. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 615 PM MDT Thu Sep 16 2021 VFR conditions and breezy south winds will prevail this evening and most of tonight -- until 09-10Z Friday morning -- at which point a cold front will surge southward through the Tri-State area. Winds may become light/variable (for a brief period of time) immediately preceding the frontal passage.. but will abruptly shift to the N-NNE and increase to 25-35 knots w/gusts up to 40-45 knots in the immediate wake of the frontal passage.. around 09-10Z. Strong northerly winds will usher IFR/MVFR ceilings (~1,000 ft agl) into the region shortly thereafter.. by sunrise. MVFR ceilings will linger through the remainder of the TAF period.. though bases may gradually increase from ~1,000 ft to 2,500 ft AGL during the afternoon. Strong NNE winds will shift to the NE and decrease to 20-25 knots by 15-16Z, further decreasing to 10-15 knots by early afternoon (~19-20Z). && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...076 LONG TERM...JBH AVIATION...VINCENT
Area Forecast Discussion
National Weather Service Memphis TN
814 PM CDT Thu Sep 16 2021 .UPDATE... An upper-level cyclone is nearly stationary over the Southern Plains this morning, inching eastward toward the Arklatex by this time tomorrow. Despite this trough approaching, 500mb geopotential heights are forecast to increase slightly as the low slowly fills beneath a broad ridge. Precipitable water is currently in the neighborhood of 1.75` across the region per the latest GOES estimates, but further moistening of the column is anticipated over the next 24 hours. Fairly widespread low clouds are expected tonight and this should limit the fog potential. Nonetheless, patchy fog was included across much of northeast AR, the Bootheel, and west TN. A few showers are possible late tonight as broad isentropic ascent develops across the area, but rain chances will increase after sunrise once surface heating commences. We are expecting a fair amount of convective coverage tomorrow given the moist air mass. The height rises mentioned above may continue to limit instability, maintaining more showery precipitation as opposed to numerous thunderstorms. The severe weather potential remains low with this activity, but some localized heavy rainfall cannot be ruled out. The 12z HREF LPMM QPF fields corroborate this potential. Basically, some areas may get an inch or two while others get none. Summer in the Mid- South! MJ && .PREV DISCUSSION... /issued 347 PM CDT Thu Sep 16 2021/ Rainy weather appears in store for the Midsouth on Friday, ahead of a slow-moving weak upper low over east TX. Precipitable water (PW) values in excess of 2 inches will surge north from the gulf coast in advance of this feature. BY 18Z Friday, the GFS, NAM and HRRR depict 2.1 to 2.3 inches PW along and south of I-40. An inverted surface pressure trof extending from the Arklamiss up the MS delta will provide some focus for convection, along with numerous boundaries from differential surface heating. Instability will wane Friday night, but scattered showers will likely continue, with the upper low nearly stalled over AR. Coverage of showers and thunderstorms will increase Saturday, aided by by surface heating. The upper low will likely have weakened a bit Sunday. Given its position over the Ozarks, scattered showers and thunderstorms still a good bet over the Midsouth Sunday afternoon. The weak upper low will finally lift out in advance of an approaching longwave trof over the northern and central Great Plains. Medium range model solutions for this feature differed quite considerably from yesterday, when consensus depicted the upper trof as a slow-moving closed low. Today`s solutions depict this feature as more progressive, but still rather deep upper trof. As such, midlevel height falls begin impinging on the Midsouth earlier than previously forecast, driving an associated Pacific surface cold front through the Midsouth Tuesday night. By midday Wednesday, post-frontal surface dewpoints cool to near 60F, and precipitable water values fall to around a quarter inch over east AR and west TN. NBM PoPs hung on to high end chance PoP Wednesday afternoon, likely a result of older blended model members. If current deterministic and ensemble mean solutions hold, sunny skies and low humidity should arrive to the most of the Midsouth by Wednesday afternoon. Dewpoints in the 50s will set the stage for some autumn-like low temps in the 50s Thursday and Friday of next week. PWB && .AVIATION... /00z TAFs/ Widespread low clouds continuing to persist throughout the area, especially near KTUP. IFR conditions spreading in from the south this evening. Ceilings lifting to MVFR around 15Z. Isolated showers will start pushing in from the south around 17Z through the end of the TAF period. Confidence is low on exact location of showers so continued mention of VCSH at all TAF sites. Winds generally easterly between 5-10kt. CAD && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$
...Updated Aviation Forecast Discussion...

.DISCUSSION... Issued at 349 PM CDT Thu Sep 16 2021 Today and Tomorrow: Clear skies, warm temperatures, and strong south winds are dominating the area today. As of 3 pm, many areas have reached 90 degrees or are inching toward it. Temperatures are expected to peak in the low 90s. The warm temperatures won`t continue into tomorrow as a cold front will move through the area tonight. Storms are expected to develop behind the front with initiation near 1 am. This is a bit later than what was forecast from the morning forecast package. Any storm development won`t fully be able to take advantage of the instability enhanced by today`s plentiful sunshine. ML CAPE values this afternoon are expected to top out near 2000 J/kg. By time of storm initialization, that ML CAPE should have dropped below 1000 J/kg. Storms are expected to be elevated, but with high LCL and LFC heights, it may be difficult for strong storms to develop. If any strong storms do develop, the shear profile could support severe criteria hail initially. The hail potential should drop off quickly after midnight. The HRRR and RAP show DCAPE values between 1000 to 1500 J/kg before midnight which is supportive of a severe wind gust threat. If storms can be sustained, strong winds would be the primary concern after midnight. The front will slow, and perhaps even stall out over southern Nebraska and Iowa tomorrow morning. Shear vectors parallel to the boundary and precipitable water values near 1.5" support a marginal risk for excessive rainfall. CAM models suggest a secondary line of precipitation will develop across southern Nebraska and travel along the stalled boundary into southwest Iowa. This secondary line of precipitation could linger into the late afternoon. For tomorrow, outside of early day precipitation, expect strong northerly winds behind the front with gusts up to 25 mph. Those winds should begin to diminish in the early afternoon. Depending on your location, temperatures should be 10 to 15 degrees cooler tomorrow than today. Saturday and Sunday: A ridge is forecast to build over the Plains this weekend leading to clear skies, no precipitation, and warming temperatures. Highs on Saturday are forecast to be in the mid 80s while Sunday should see temperatures in the low 90s. Monday through Wednesday: The primary weather concern in this period will be a deep upper level trough that is expected to impact the northern Plains on Monday. The GFS/ECMWF/Canadian are in good agreement on timing, but do differ in precipitation placement. The best lift for precipitation appears to be to the north and east, but there is about a 55% chance for rain across the area. The attendant cold front will result in cooler temperatures. Though, that will be cooler relative to the previous few days, as the cool down will result in temperatures right around the climatic normal. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 622 PM CDT Thu Sep 16 2021 Still breezy across the area now, but winds will quickly diminish this evening with gusts falling below 20 knots by sunset. A chance of thunder is still possible for all three sites. KOFK could see severe weather but confidence is slipping. With the scattered nature of the storms, have kept mention out of TAFs as confidence falls. Best chance at KOFK and lesser chances at KOMA and KLNK. Low level wind shear is expected to be in place after 03Z Friday until about 11Z. LLWS will be near FL019 at about 30 to 35 knots. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Fajman AVIATION...Nicolaisen
Area Forecast Discussion
National Weather Service Shreveport LA
1011 PM CDT Thu Sep 16 2021 .SHORT TERM.../Tonight/ The evening sfc analysis indicates that the remnant sfc low of what was left of Nicholas is centered between LCH and LFT, with an extensive wrap-around cu field persisting well to the N over much of N LA and Lower E TX. The latest satellite imagery indicates that the cu field has begun to expand back to the W around the low level circulation, as it slowly begins to lift N overnight into Cntrl LA. Sct convection which has been persistent this evening along the attendant weak H850 inverted trough axis over Cntrl LA into SW MS, has gradually been showing some signs of weakening, although additional convection redevelopment can not be ruled out overnight as this inverted trough continues to lift N into N LA/Srn AR through daybreak Friday. The latest HRRR keeps any convection development isolated to widely sct at best, as does the 18Z GFS, which overall continues to be the better performer with this system given the considerable wedge of dry air aloft that persists over the area. Thus, have reduced pops a bit over NCntrl LA/SCntrl AR overnight, tapering down to low and mid chance. Have also scaled back pops to slight chance over SW AR/extreme NW LA/Ern TX, with redevelopment more probable after daybreak Friday as the sfc-H700 low becomes centered over N LA. The only changes needed to min temps tonight were to lower readings across portions of SE OK/adjacent SW AR, but otherwise, the remainder of the forecast is on track. Zone update already out...grids will be available shortly. 15 && .PREV DISCUSSION... /issued 725 PM CDT Thu Sep 16 2021/ .AVIATION... VFR conditions will continue this evening, as an extensive cu field lingers across N LA/much of Lower E TX/SCntrl AR. Cigs will be more hit and miss this evening across portions of NE TX/SW AR/SE OK, as they begin to scatter out. MVFR cigs should redevelop by mid to late evening over portions of NCntrl LA, spreading W into Srn AR/NW LA and into extreme Ern TX overnight affecting all terminals with the exception of TYR. These cigs should lower/become IFR or LIFR late over N LA/portions of Deep E TX and SCntrl AR, as the low level circulation associated with the remnants of Nicholas shifts N into Cntrl LA by/prior to daybreak. Isolated -SHRA may develop late tonight across N LA/SCntrl AR near and N of the approaching sfc low, and have inserted VCSH mention for MLU after 09Z, before inserting mention for ELD at 13Z. Along with the lowering cigs, vsbys may lower as well in -DZ/patchy FG, primarily affecting NCntrl LA. Only slow improvement to cigs are expected Thursday morning, with IFR/MVFR cigs hanging tough through at least midday before more marked improvements are seen. MVFR cigs should linger through the remainder of the TAF period though across much of N LA/SCntrl AR, with sct convection expected to increase from late morning through the afternoon over N LA/SW AR, and thus have continued VCTS mention for the SHV/MLU/TXK/ELD terminals. Convection should be more isolated across E TX, and thus have left any thunder mention out of these terminals for now given the low confidence. The convection should diminish during the evening with the loss of heating, although MVFR and eventually IFR cigs should redevelop again over much of the area by late evening through late Thursday night. ENE winds around 5kts this evening will become Lt/Vrb by mid to late evening. Look for winds to become NE around 5kts after 15Z. /15/ && .PRELIMINARY POINT TEMPS/POPS... SHV 73 85 71 88 / 20 60 30 80 MLU 72 83 71 85 / 40 70 40 90 DEQ 68 88 69 87 / 10 20 20 30 TXK 70 85 71 86 / 10 40 20 40 ELD 69 80 68 85 / 30 70 40 70 TYR 70 90 70 89 / 10 10 10 30 GGG 71 88 70 87 / 10 20 20 50 LFK 71 89 70 89 / 10 30 20 60 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...None. LA...None. OK...None. TX...None. && $$ 15