Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/02/20

Area Forecast Discussion
National Weather Service Bismarck ND
1020 PM CDT Wed Apr 1 2020 .UPDATE... Issued at 1020 PM CDT Wed Apr 1 2020 We`ve upgraded far south central ND to a Winter Storm Warning in respect to the rapidly-maturing heavy snow band centered across western SD as of 03 UTC. Guidance remains quite dispersive with the placement of this band overnight, but extrapolation suggests it will reach an axis centered on Logan and McIntosh Counties. Convective elements in south central SD also appear likely to merge with the frontogenetically-driven mesoscale band and will likely yield 1" per hour snowfall rates in a narrow axis which should reach into south central ND after midnight CDT. Recent RAP cycles and the 00 UTC NAM best-reflect recent trends, so we chose to weight the overnight forecast closer to them, which resulted in increased PoPs as far north as Bismarck/Mandan before 12 UTC. We also sped up the start time of the Winter Weather Advisory from Bowman and Hettinger to Bismarck/Mandan to 3 am CDT based on the observed trends. Note however that this is an evolving scenario, and a tight gradient in snowfall amounts is possible with this initial band, so confidence in forecast details is still modest outside of far south central ND. Pending later observational trends, the Winter Storm Warning may need to be extended further northeast into Stutsman and surrounding counties, as well. UPDATE Issued at 712 PM CDT Wed Apr 1 2020 Quick update to let the Winter Weather Advisory in the northwest and far north central expire as scheduled at 00 UTC in line with the latest observational trends. UPDATE Issued at 538 PM CDT Wed Apr 1 2020 We increased PoPs for predominantly snow across central ND through about 03 UTC with this update to reflect ongoing radar and surface observation trends. Namely, convectively-enhanced snow showers are persisting in the post-frontal regime, particularly where midlevel lapse rates exceed 7 C/km and where RAP-based soundings show non- zero, though weak MUCAPE aloft. Precipitation is being aided by midlevel frontogenesis as well. Guidance suggests midlevel lapse rates will become more stable by mid evening as the post-frontal air mass cools further, and the initial frontogenesis will also weaken. Otherwise, no changes to headlines or the rest of the forecast are being made at this time, though we fully expect to let the Winter Weather Advisory in northwest and far north central ND to expire as scheduled at 00 UTC. We`ll be monitoring mesoscale trends from SD into far south central ND closely later this evening to assess how the next round of potential banded precipitation may evolve overnight. && .SHORT TERM...(This evening through Thursday) Issued at 220 PM CDT Wed Apr 1 2020 As an upper level shortwave continues to rotate north and east, snow across the north will continue to taper off through the evening. Further south, expect some rain and snow showers to persist through the afternoon and into the evening, potentially mixed with some light freezing rain and/or sleet. As the snow has continued to diminish, we elected to go ahead and convert the Winter Storm Warning across the far northwest to an Advisory. With light snow still lingering in these areas, will keep the Advisory going for now. After a brief lull in activity, another shortwave rotates around the base of a western trough into south central North Dakota tonight. Precipitation across the far south central and southern James River Valley will likely start as rain, transitioning to a wintry mix of rain, freezing rain, and snow, and then eventually to all snow. At times on Thursday, snow may mix with freezing drizzle across the southern James River Valley as forecast soundings suggest the loss of ice aloft periodically. Yet another wave rounds the base of the trough into southwestern and south central North Dakota during the late morning hours on Thursday, spreading accumulating snow across portions of the southwest and much of the central. When all is said and done, 4 to 6 inches of snow is likely across the James River Valley with ice accumulations of up to a tenth of an inch. Further west and north (including the Bismarck/Mandan area), confidence is increasing in accumulations reaching the 3 to 5 inch range. Because of this, we have elected to expand the Winter Weather Advisory area west and north, although we will not begin the Advisory in these areas until 12z on Thursday. The only other change was to up the start time of the Advisory over the James River Valley to 03z Thursday as guidance has come better in line regarding onset timing. Expect cold temperatures on Thursday with highs in the 20s. .LONG TERM...(Thursday night through Wednesday) Issued at 220 PM CDT Wed Apr 1 2020 Snow will begin to diminish to the east late Thursday night into Friday morning as the main vort lobe finally pushes out of western and central North Dakota. A subtle upper ridge moves in Friday afternoon which will lead to subsidence and widespread clearing. The ridging will also start to slowly moderate temperatures again after a chilly morning, mainly in the teens. Friday will see highs in the 30s, and we will see highs this time frame back into the 40s again through the rest of the weekend. A progressive pattern continues and various weak waves will bring chances of light rain and/or snow through Sunday night, but details and exact timing remain unclear at this time. A more substantial warm-up comes back into the forecast by the beginning of the next work week with widespread highs in the 50s and 60s by Tuesday. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 712 PM CDT Wed Apr 1 2020 MVFR ceilings will gradually improve to VFR from west to east this evening through 06Z with KJMS possibly remaining MVFR (with brief periods of IFR) overnight, though this is less certain. Conditions deteriorate for the far south-central and James River Valley, including KJMS, early Thursday morning with chances for snow. Periods of heavier snow could drop KJMS cigs/vsby to IFR in the 12-18Z time frame. Gusty northwest winds continue for all of western/central North Dakota through the TAF period. && .BIS WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 7 AM CDT /6 AM MDT/ Thursday to 7 AM CDT /6 AM MDT/ Friday for NDZ005-012-013-019>023. Winter Weather Advisory until 7 AM CDT /6 AM MDT/ Friday for NDZ025-036-037-045-048-051. Winter Weather Advisory from 3 AM CDT /2 AM MDT/ Thursday to 7 AM CDT /6 AM MDT/ Friday for NDZ034-035-041>044. Winter Storm Warning until 7 AM CDT Friday for NDZ046-047-050. && $$ UPDATE...CJS SHORT TERM...ZH LONG TERM...ZH AVIATION...AE
Area Forecast Discussion
National Weather Service Cheyenne WY
926 PM MDT Wed Apr 1 2020 .UPDATE... Issued at 922 PM MDT Wed Apr 1 2020 Minor updates to this evenings forecast as temperatures really falling rather quickly across our northern zones. Douglas down to 21 degrees and Chadron 26. Dropped temperatures several degrees for overnight lows. Do feel rest of forecast is on track. DOuglas had some pretty heavy snowfall up there with WYDOT webcams showing snow covered roads there and at Natural Bridge. Updates have been sent. && .SHORT TERM...(This evening through Thursday) Issued at 323 PM MDT Wed Apr 1 2020 A few showers popping up across southeastern Wyoming and the western Nebraska Panhandle this afternoon ahead of a strong cold front, now draped across northwest Wyoming. Some of these showers may produce lightning and strong gusty downdraft winds with soundings showing an inverted-V profile and CAPE of 200 to 500 J/kg mainly along a Cheyenne to Scottsbluff line and to the south. It`s possible that may also see pea-sized hail in the mix this afternoon, however, inverted-V profiles are conducive to melting in the lower levels. And to the north of this line, clouds and virga have likely led to a moistened layer that may stymie any thunderstorm activity this afternoon. The cold front to the northwest will slowly make its way southeast, supported by a favorable synoptic setup that will increase frontal forcing and banded precipitation ahead of and along the front. Hi-Res models seem to have a strong grip on the forecast, thus the forecast is strongly skewed towards the HRRR and NAMNest models. Both of these models have strong bands of precipitation moving into Niobrara, Converse and Carbon Counties this evening with snow falling heavily along these bands. Heaviest snow amounts will fall across Niobrara and Converse Counties this evening and continue through early Thursday morning, with snow continuing behind the bands over the course of the day. To the south across Carbon County, bands of heavy snow will form around midnight and continue to impact the county, and northern Albany County, through the early afternoon, again continuing to snow behind the snowbands. Further south and east of a Carbon-Converse-Niobrara line, the forecast becomes a little more tricky as there will likely be an extended period of mixed precipitation tonight and tomorrow morning. This may lead to a light glaze to the north, and to the south along the I-80 corridor, ice accumulations of up to a tenth of an inch. Soundings indicate a low, moist and cold lower layer, leading to mixed precipitation, freezing drizzle, ice accumulation, and frozen thick fog, leading to a rime layer over elevated surfaces tonight and tomorrow morning. As the dendritic zone moistens, precipitation will transition to snow. This transition will begin to the northwest of this mixed precip area along the isentropic boundary as the cold air mass behind it sinks further southeast. Chadron will transition earlier to snow around sunrise; Scottsbluff and Cheyenne around noon Thursday, and Sidney by mid- afternoon. Behind this boundary, expect snow accumulation to continue, but to lessen over time, finally tapering off from the northwest after midnight. Have placed little weight on GFS/EC banding as the frontal passage occurs as the NAM and all Hi-Res guidance shows banding breaking down once the band makes it south of that aforementioned Carbon-Converse- Niobrara line. Several Winter Storm Warnings and Advisories have been issued to cover the threats expected with this system. Please see their text for further details. A few things of note: Snow amounts may be heavier across the I-80 Summit, the I-80 Arlington area, and across northern Platte and Goshen Counties due to these bands and maybe an earlier transition to snow as the dendritic zone saturates. Have conveyed these concerns to the evening shift as they may need to be upgraded/issued as we move into the event. Not expecting winds greater that about 20 mph overt the course of the event, which will lessen the blowing snow threat that usually gets us in trouble across the roadways. Still, the banded snow will lead to heavier snow rates, about 2-3 inches per 3 hour period, which will lead to snow-packed roads and hazardous travel conditions. Precipitation will have tapered off over the course of Thursday night and Friday morning. But the cold air mass behind this system will have filtered in for cold Friday morning temperatures ranging from 5 to 15 degrees across the High Plains and adjacent Mountain Terrain. Clear to partly cloudy skies Friday will allow afternoon temperatures to warm into the 30s. .LONG TERM...(Thursday night through Wednesday) Issued at 323 PM MDT Wed Apr 1 2020 Overall a fairly quiet weather pattern expected with no major system affecting the CWA. It will be warming up over the weekend as the upper flow gradually turns southwesterly with just a few showers possible over the higher mtns. The mild pattern should persist into early next week as a weak upper ridge builds over the area ahead of an upper low that will sink slowly southward off the Cal coast. Weak impulses will rotate around this low and across the area and bring some rain and snow showers to mainly western parts of the CWA at times, with the best coverage looking to be on Tuesday. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 521 PM MDT Wed Apr 1 2020 Wyoming TAFS...VFR at Rawlins until 03Z, then IFR until 16Z, then MVFR. Wind gusts to 25 knots from 03Z to 16Z. VFR at Laramie until 06Z, then IFR until 18Z, then MVFR. Wind gusts to 25 knots from 06Z to 13Z. VFR at Cheyenne until 04Z, then IFR until 18Z, then MVFR. Wind gusts to 32 knots until 04Z, then to 25 knots after 04Z. Nebraska TAFS...MVFR at Chadron until 03Z, then IFR until 16Z, then MVFR. VFR at Alliance until 02Z, then MVFR until 04Z, then IFR until 18Z, then MVFR. Wind gusts to 37 knots until 02Z, then to 30 knots after 02Z. VFR at Scottsbluff until 04Z, then IFR until 18Z, then MVFR. Wind gusts to 38 knots until 02Z, then to 28 knots after 02Z. VFR at Sidney until 04Z, then MVFR until 06Z, then IFR until 18Z, then MVFR. Wind gusts to 34 knots. && .FIRE WEATHER... Issued at 323 PM MDT Wed Apr 1 2020 Cold with a wintry mix expected through early Friday morning, with little fire concerns through the short-term. Will begin a warming trend over the weekend with temperatures reaching into the 50s next week. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Winter Weather Advisory until midnight MDT Thursday night for WYZ116. Winter Weather Advisory until 9 PM MDT Thursday for WYZ104>106- 109>111-113. Winter Storm Warning until 9 PM MDT Thursday for WYZ101>103-112- 114. Winter Weather Advisory from 6 AM to 9 PM MDT Thursday for WYZ115. NE...Winter Weather Advisory until midnight MDT Thursday night for NEZ002-095. && $$ UPDATE...GCC SHORT TERM...AB LONG TERM...RE AVIATION...RUBIN FIRE WEATHER...AB
National Weather Service Hastings NE
943 PM CDT Wed Apr 1 2020 .UPDATE... Issued at 940 PM CDT Wed Apr 1 2020 Based on observations and the HRRR`s faster movement with the cold front, have sped up the passage of the front through the forecast area. The hourly temperatures looked to be fairly good, although I`m not sure if it`ll get quite that warm in the southeast. The 00z HRRR and even the 00z NAM show the front through the majority of the forecast area by 18z Thursday. Mainly sped up the wind forecast to show the frontal passage. Also included a bit more coverage for drizzle late tonight/early Thursday. Think the chance for drizzle as this front moves in tonight towards morning is fairly good and tried to increase that potential after 9z. && .SHORT TERM...(This evening through Thursday) Issued at 358 PM CDT Wed Apr 1 2020 The biggest issue in the short term involves a slow-moving, yet strong cold front that will begin moving through our CWA perhaps toward 05Z Thursday (midnight tonight), and will not clear our CWA until perhaps 23Z Thursday (6pm Thursday). Timing of the front through the tri-cities is shaping up to be roughly 7 am at Kearney to around 9 am at Grand Island, and 10 am in Hastings, NE from current best estimates from short-term numerical models. This will probably mean a morning high in the lower 50s for the tri-cities, before dropping like a rock through the afternoon into the 30s by mid to late afternoon. NAM surface temperatures suggest that we could start getting to freezing or below for places like Ord as early as 1 pm Thursday. These times should not be taken as an exact forecast, but rather as estimates by looking at latest trends in short term and high resolution models. Our thinking will almost surely change a bit as we get closer to Thursday/Thursday night and we can tell more exactly where and how fast the cold front seems to be moving. Inverted and saturated low-level along with stubborn mid-level dry air could create a bit of a headache for freezing drizzle potential as surface temperatures drop below freezing during the afternoon and evening from northwest to southeast. It appears that at least elevated surfaces stand a good chance at a bit of ice accumulation during this period. For the tri-cities, it appears this may start occurring as early as 6-7 pm Thursday as cold air advection ensues. Warm ground temperatures will probably resist a quick freeze up initially, but even so, eventually ground temperatures could start to get cool enough to allow perhaps a bit of icing on roadways by overnight Thursday night before ending early Friday morning as the surface high helps scour out our precipitation chances. To add to the complexity, we could saturate mid-levels from time to time to give us a few snowflakes added as well, although it does not appear that this would be a big snow producer in the post-frontal regime. .LONG TERM...(Thursday night through Wednesday) Issued at 358 PM CDT Wed Apr 1 2020 Overall synoptic pattern continues to be rather active, bringing in multiple waves kicked out by a mean trough over the northwestern CONUS. Temperatures could be a virtual roller coaster over the course of the long term, starting out cold, turning much warmer, and cooling at bit by the end by Wednesday. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday) Issued at 634 PM CDT Wed Apr 1 2020 VFR conditions currently with breezy south winds will change by the end of the forecast to IFR and breezy north winds. Breezy south winds will decrease this evening as the sunsets and they will remain light until the front moves through Thursday morning into early afternoon at the terminals. The front will change winds to the north and be breezy. Ceilings will decrease after 09-10z from MVFR to IFR around sunrise. There is a chance for light rain or drizzle during the morning hours, but confidence is not high on how this will develop and have left the forecast dry for now. While I cannot guarantee the forecast will stay dry, the best chance for preciptiation is after the 24 hour valid period of these TAFs. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ UPDATE...Billings Wright SHORT TERM...Heinlein LONG TERM...Heinlein AVIATION...Billings Wright
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
520 PM MDT Wed Apr 1 2020 .DISCUSSION...(This Evening Through Wednesday) Issued at 232 PM MDT Wed Apr 1 2020 Deep NW CONUS upper trough and associated front side jet continues to dig into the region as a potent cold front surges south. Decent moisture advection south of the region will set the stage for a period of moderate to heavy snow over parts of the area, with concentrated FGEN expected to support a band of heavy snow across a small subset of the region. LSA increasing across the region as the upper jet noses east. This will continue to support scattered showers over the SE half through the afternoon with windy conds as the cold front shifts south. As the main upper trough starts to shift closer the region. LSA will increase with precip becoming more widespread. Main concern tonight will be an expected area of concentrated FGEN. Hires models have been picking up on this to some degree. However, given the strong cold frontal surge ongoing across the region, prefer the NAM solution (as opposed to the RAP HRRR) as to where the strongest concentrated FGEN will develop. Both the 12Z and 18Z runs continues to display a robust band from southern Weston county NE into central SD. Snowfall amounts in the band will be intense for a period with strong lift centered in the DGZ where steep mid level lapse rates will be in place. Would not be surprised if there is some thunder in this band given the intense nature of lift combined with steep mid level lapse rates, With adjusted QPF for this concern, opted to upgraded the adv for the area where the expected convective band will develop. Winds dont look too bad, but given the degree of CAA combined with expected snowfall, patchy to areas of reduced vis and drifting can be expected. Further SE over scentral SD, dry slotting will support freezing rain at times with little to no snow accums. There will be the potential for a tenth or so of ice accums, mainly on elevated sfcs. This system will begin to exit the region tomorrow afternoon west-east with precip ending. Clearing on the backside will set the stage for very cold temps, esp in the west and over deeper snow cover. Temps there could drop below zero. Semi-active but warmer flow in store after Friday, with temps in the 50s and 60s again by early next week. && .AVIATION...(For the 00Z TAFS Through 00Z Thursday Evening) Issued At 510 PM MDT Wed Apr 1 2020 Conditions continue to deteriorate across the area with showers and ISOLD TSRA over south west and south central SD. MVFR conditions continue with IFR/LIFR conditions spreading across northeastern WY, the BLKHLS and much of west this evening and central/southern SD later tonight. This storm will bring widespread, accumulating snow to the area with IFR and LIFR conditions through midday Thursday. As the storm begins to move out late Thursday, conditions will begin to improve slowly from west to east. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...Winter Storm Warning until midnight MDT Thursday night for SDZ024-028-029. Winter Weather Advisory until 6 AM MDT Friday for SDZ043-044. Winter Weather Advisory from 1 AM Thursday to 7 AM CDT Friday for SDZ046-047-049. Winter Weather Advisory until midnight MDT Thursday night for SDZ027-030-041-042-074. Winter Weather Advisory from 9 PM this evening to midnight MDT Thursday night for SDZ001-002-012. Winter Storm Warning until midnight MDT Thursday night for SDZ013-014-025-026-031-032-072-073. WY...Winter Storm Warning until midnight MDT Thursday night for WYZ057. Winter Weather Advisory from 9 PM this evening to midnight MDT Thursday night for WYZ071. Winter Storm Warning until 3 PM MDT Thursday for WYZ055-056-058. Winter Weather Advisory until 3 PM MDT Thursday for WYZ054. && $$ DISCUSSION...JC AVIATION...MLS