Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/31/20

Area Forecast Discussion
National Weather Service Aberdeen SD
934 PM CDT Fri Oct 30 2020 .UPDATE... Issued at 934 PM CDT Fri Oct 30 2020 Increased lows overnight. Otherwise, the rest of the forecast looked good. UPDATE Issued at 657 PM CDT Fri Oct 30 2020 00z aviation discussion updated below. && .SHORT TERM...(This Evening through Saturday Night) Issued at 229 PM CDT Fri Oct 30 2020 Stratus and fog remain entrenched over central SD this afternoon. A slow erosion from the south of the stratus field is expected to continue into this evening. The clouds have markedly affected temperatures today and are posing a headache for hourly temp guidance this evening. Went with HREF for both sky cover and hourly temps, though even it may be a little high until winds kick in. A front will sweep through the Dakotas tonight. South to southwest winds ahead of the front will be breezy with some enhancement expected along the Sisseton Hills and Coteau as the H85 winds shift to the southwest. Drier air with steeper lapse rates will push in behind the front. However, an upper trough with shortwave energy will, too, and may bring some increased mid level cloud cover for the morning. Any clouds will limit mixing and gustiness. As winds shift to the northwest behind the front, the pressure gradient be a difference of about 10 mb across the state which is not as strong as models indicated yesterday. Lapse rates remain steep at 7-9 with inverted V soundings. 6z model runs were weaker, overall, than 12z runs. The GFS still maintains 70kts at 700 mb and a 50 kt corridor at H85 at 21z which is similar to yesterday`s model guidance. Only the 12z RAP BUFKIT soundings showed Lemmon, Mobridge, or Pierre briefly gusting to 50 kts between 21 and 23z. It would require mixing to 3500 to 4000 ft, which is unlikely in the valleys. Cannot completely rule out an isolated gust on one of the ridges during the late afternoon, though. Decided with neighbors to go with an area-wide wind advisory and message the potential for isolated higher wind gusts. It does look like a slam-dunk for a high end wind advisory provided the clouds clear out as models indicate in the afternoon. High pressure then builds in at the sfc Saturday night. .LONG TERM...(Sunday through Friday) Issued at 229 PM CDT Fri Oct 30 2020 A surface ridge axis will move east across the area on Sunday while a warm air advection pattern begins to take shape. This will be the onset of rather mild air that will stream across the region through Thursday of next week. Given the 850mb temps in the mid teens combined with favorable west to southwest mixing winds, decided to lean towards the warmer end of guidance for high temperatures. This ended up being a few degrees warmer than inherited NBM guidance after blending in warmer solutions. Only thing to worry about would be any residual snow cover across central/north central SD into the Glacial Lakes region come Monday or even into Tuesday. Hard to say how much will be left by that time, given the expected highs during the short term period. May need to make some adjustments in the coming days, but expect most of the snow to be gone or close to it by the start of next week. As for precipitation chances, the pattern looks rather dry for the upcoming week and do not see anything concerning. && .AVIATION...(For the 00Z TAFS through 00Z Saturday Evening) Issued at 657 PM CDT Fri Oct 30 2020 Terminals KABR,KATY,KPIR,KMBG A surface cool front will sweep quickly across the region tonight into Saturday morning bringing very strong northwest winds on Saturday. Strong llws is expected this evening into Saturday morning until the mixing layer deepens and the strong winds mix down. The llws will be from the southwest tonight and from the northwest early Saturday with wind speeds up to 50 knots to 2000 feet. Otherwise, VFR conditions are expected through Saturday. ***Construction to improve taxiways at both KABR/KPIR terminals may cause an occasional temporary visibility reduction due to blowing dust (bldu), mainly during daytime hours UFN. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...Wind Advisory from 1 PM CDT /noon MDT/ to 8 PM CDT /7 PM MDT/ Saturday for SDZ003>011-015>023-033>037-045-048-051. MN...Wind Advisory from 1 PM to 8 PM CDT Saturday for MNZ039-046. && $$ UPDATE...Mohr SHORT TERM...Wise LONG TERM...TMT AVIATION...Mohr
Area Forecast Discussion
National Weather Service Bismarck ND
1019 PM CDT Fri Oct 30 2020 .UPDATE... Issued at 1012 PM CDT Fri Oct 30 2020 Several SPS`s have been issued for wind gusts up to 55 mph that have accompanied some light rain making it into western North Dakota. Focus for strong winds is shifting southward as the cold front pushes southeast. The trend this past hour has been for the max wind gusts to diminish slightly, with upstream wind gusts in the 30 to 40 mph range behind the frontal trough. With the bulk of the current pressure rises forecast to remain to the west of the state, we`ll refrain from making any headline changes at this time with overall winds expected to stay sub-advisory criteria for now. UPDATE Issued at 849 PM CDT Fri Oct 30 2020 A line of showers have developed along strong 850mb frontogenesis over northeast Montana. These showers have a recent history of producing several 50 to 60 mph wind gust reports as well as 75 mph at the Glasgow MT airport. The GGW 00Z observed sounding features an inverted V signature with dry adiabatic lapse rates up to near 500mb atop a shallow boundary layer inversion. RAP forecast soundings in NW North Dakota show a similar dry sub-cloud layer developing, though with a more substantial inversion given colder surface temperatures. As 850mb winds rapidly increase over the next hour or so atop northwest North Dakota, there is the increasing potential for strong gusty winds to be associated with the aforementioned showers. Though this may be tempered by cooler surface temperatures, the inversion on the forecast soundings is shallow and may not fully prevent the momentum transfer of stronger winds aloft. The northwest portions of North Dakota from McKenzie county northward should watch for strong gusty winds in the next one to two hours, with increasing uncertainty further east. UPDATE Issued at 712 PM CDT Fri Oct 30 2020 00Z surface analysis places upcoming cold front from northeast through south central Montana, currently past Malta and Lewistown. Pressure falls ahead of the frontal trough have maintained breezy southerly/southeasterly winds across much of North Dakota. Warm air advection overrunning the cool surface layer has also maintained a very shallow surface inversion, responsible for lingering stratus and fog over south central North Dakota. Guidance is not in great agreement about when this near-surface layer finally drys out, with RAP drying by 03Z, GFS by 05Z, and NAM not until almost 12Z. Based on the 00Z observed BIS sounding, the stratus layer is not terribly deep at just over 1000 feet. But with the RAP continuing 850mb WAA until 08Z, this stratus/fog may stick around this evening. We issued a short-term SPS for areas of dense fog based on road cameras and surface obs, but this may need to be re-issued based on how trends play out. No need for changes to messaging for tomorrow`s winds. We`ll see how upstream observations and 00Z guidance comes in but current forecast and headlines look good. && .SHORT TERM...(This evening through Saturday) Issued at 140 PM CDT Fri Oct 30 2020 Two strong cold fronts and associated gusty winds are the highlight of the short-term. Ahead of an approaching low pressure system strong warm air advection will kick in. Breezy southerly winds will keep temperatures from falling too far tonight with readings generally in the 30s. The first cold front will sweep through around midnight tonight. This will shift winds out of the west, but only increase them marginally. The stronger cold front (and main pressure rises) will arrive Saturday morning. Although a few cold advection showers can not be ruled out near the Canadian border, it is likely most areas will stay dry Saturday. A downsloping wind component, strong Cold air advection behind the cold front, isallobaric forcing and afternoon mixing all have the potential to come together and produce sustained winds around 35 mph and gusts to 55. There are some indications that winds could be even stronger, however, there are some factors that could limit the higher end potential of this event. Thus, a Wind Advisory has been issued as confidence is high in widespread Wind Advisory level winds, but not great enough for the higher end potential to warrant a High Wind Warning at this time. Timing, mixing and cloud cover are factors that could limit the higher end potential of winds. With the surface low tracking to our north, the strongest pressure rises will be noticed across northern North Dakota, however,cloud cover could limit mixing. Additionally, the 12 UTC guidance suite has the cold front and pressure rises moving through a bit earlier than previous runs. This could also limit the highest potential as the strongest cold air advection could be east of the area by the time peak heating/mixing kicks in. With that said...if these factors don`t contribute then wind gusts over 60 mph will be possible. .LONG TERM...(Saturday night through Friday) Issued at 140 PM CDT Fri Oct 30 2020 A dry, warming trend highlights the long term. Highs in the 60s will be common across much of the forecast area Monday through Wednesday, with a 70s not out of the question over the southwest. The broad upper level ridge responsible for this nice weather, begins to flatten by the middle of the week with more seasonable temperatures and perhaps a hit or miss shower by next weekend. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 712 PM CDT Fri Oct 30 2020 LIFR stratus continues at KBIS through part of the evening. Not a lot of confidence in when this stratus should improve to VFR, though an upcoming cold front and wind shift early Saturday morning should do the trick. The question will be is if this stratus can dissipate before then. The TAF may need to be amended if trends show the stratus continuing after 03Z. Otherwise the main issue will be LLWS associated with a strong cold front tonight. Winds at 1500-2000 feet increase to around 50 kts. Wind shear diminishes as surface winds increase Saturday morning, with strong northwest surface winds gusting to around 50 kts expected. FEW to SCT at 3k ft may develop behind the front during the day Saturday. && .BIS WATCHES/WARNINGS/ADVISORIES... Wind Advisory from 10 AM CDT /9 AM MDT/ to 7 PM CDT /6 PM MDT/ Saturday for NDZ004-005-012-013-017>023-025-031>037-040>044. Wind Advisory from 1 PM CDT /noon MDT/ to 7 PM CDT /6 PM MDT/ Saturday for NDZ045>048-050-051. Wind Advisory from 7 AM to 7 PM CDT Saturday for NDZ001>003- 009>011. && $$ UPDATE...AE SHORT TERM...AJ LONG TERM...AJ AVIATION...AE
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
814 PM MDT Fri Oct 30 2020 .UPDATE... Issued at 805 PM MDT Fri Oct 30 2020 02z surface analysis had low over southern SK with pre-frontal trough into central WY and cold front into central UT. Water vapour had fast-moving shortwave trough moving across central MT. Not a lot of moisture to work for CWA. Effect of this system main concern for update. Previous ensemble guidance didn`t show high wind probabilities being that high, but latest RAP/HRRR indicate 3-5mb/3hr pressure rises during peak heating Saturday along with modest cold air advection, subsidence, and deep mixing. This setup should tap into 40-50kt 850mb (60kt 700mb) winds over the northwest SD plains from K2WX-KRAP creating high wind warning speeds. Could also have some gusty winds with pre-frontal trough, especially over the lee side of the Black Hills overnight, but gradient across the Black Hills only 3-4mb with 40kt boundary layer wind, which is usually not enough to cause troubles. && .DISCUSSION...(This Evening Through Friday) Issued at 147 PM MDT Fri Oct 30 2020 Shortwave ridging ongoing across the region as a potent ridge topping impulse dives into the Northern Plains. Decent mixing coupled with terrain effects around the Black Hills has allowed temps to rise into the 60s and lower 70s in NE WY and far western SD. Breezy conds will continue tonight there esp in the eastern BH foothills where near adv winds may develop for a couple hours ahead of the sfc trough. This will hold temps up there most of the night. Otherwise, fog and low clouds has finally mixed out over the far NE where snow cover has limited mixing. Patchy fog may redevelop there overnight given lingering BL moisture and snow pack. Clipper will shift east across the region Sat, with gusty NW winds developing behind the front esp by late morning as diurnal mixing ensues. Fast moving nature of the system has resulted in the core of the strongest winds aloft shifting east faster, thus not lining up with peak heating as well as earlier progs were indicating. Forecast models are not in consensus with wind speeds, wit the HRRR and NAM much weaker than the RAP and GFS. Hence, confidence in a warning is not high enough to upgrade the high wind watch at this time and will defer to later shifts. Did switch the watch to an adv for eastern areas with concerns on mixing per lingering snow cover and overall less wind in progs. The potential still remains for a period of warning level winds in far western SD, esp from 2WK to RAP. Much cooler conds expected Sat, with a warming trend beginning Sunday and persisting into the middle of next week. Mean ridging then progged through much of the following week with temps well above seasonal norms. Highs will likely reach into the 70s a couple days, esp Tues in the lee of the Black Hills into scentral SD where a few 80s are certainly possible. Dry pattern will continue with no chances for precip in the next seven days. Cold and snowy weather looks to return toward next Sunday-Monday as a deep upper trough develops over the western CONUS and cold air advects SE into the Northern Plains. Sfc cyclone likely early the following week (Nov. 8-10), which would likely support snow accums in a portion of the region, where exactly remains unknown for now. && .AVIATION...(For the 00Z TAFS Through 00Z Saturday Evening) Issued At 524 PM MDT Fri Oct 30 2020 VFR conditions will dominate the weather through the period. A sharp cold front will bring gusty southwest winds ahead it over the higher elevations tonight and then gusty northwest winds behind it later tonight into Saturday. Wind gusts from 30-45kts are likely Saturday on the SD plains with locally higher values from K2WX to KRAP. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...Wind Advisory from 10 AM MDT /11 AM CDT/ to 6 PM MDT /7 PM CDT/ Saturday for SDZ014-032-043-044-046-047-049. High Wind Warning from 6 AM to 6 PM MDT Saturday for SDZ001-002- 012-013-031-073. Wind Advisory from 6 AM to 6 PM MDT Saturday for SDZ025-026-072. WY...None. && $$ Update...Helgeson DISCUSSION...JC AVIATION...Helgeson