Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/14/20

National Weather Service Hastings NE
1055 PM CDT Fri Mar 13 2020 .UPDATE... Issued at 1050 PM CDT Fri Mar 13 2020 Have made some minor adjustments to POP and WX grids based on radar, satellite and model trends. Thoughts below: 1) Have added some drzl/frz drzl. Areas without significant radar returns are probably seeing this due to lack of saturation in DGZ. These areas are transient and given marginal sfc temps near freezing, doubt there will be much impacts. Perhaps some lt glaze on elevated surfaces. 2) We`ve been in a lull late this eve, but models show uptick in QPF in the 06Z- 12Z time frame. Thus, have not made any significant changes to snow amounts. There`s still factors of warm ground and wet snow/low ratios fighting against higher amounts. Still think most areas in advisory will see 3-5", with some isolated areas near 6" still possible. However, so far, impacts to roads has been fairly minimal. 3) Didn`t make any headline changes on this shift, but may very well need to move up the end time as most, if not all, appreciable QPF should be done by ~15Z. Caveat to this could be lingering potential for fzdz. However, even by 18Z will likely see temps rise 1-2 deg, which combined with March sun angle, would be enough to eliminate icing threat. Will let midshift coordinate with neighbors on this potential update. && .SHORT TERM...(This evening through Saturday) Issued at 342 PM CDT Fri Mar 13 2020 Aloft: As has been the case since mid-Nov...mainly zonal flow remains over the CONUS. Aircraft wind obs and RAP dynamic tropopause analyses indicated anticyclonic WSW flow over NEB/KS. A shrtwv trof extended from the UT-CO border down into AZ. This trof will lift NE and cross the CWA late tonight into tomorrow AM. Heights will rapidly rise in its wake...with a broad ridge forming over the Plns in response to the next low diving S along the W coast. Surface: 1050 mb high pres over Wrn Canada extended SE into the Cntrl USA. The cool front that moved thru here Thu AM was over Cntrl TX and the Gulf Coast states. Weak low pres will form along that front tonight into tomorrow...while high pres conts to dominate acrs Srn Canada. That will keep E winds over the CWA thru tomorrow. Rest of this afternoon: Radar mosaic shows predominantly -SN overtaking the CWA. The leading edge is not reaching the ground due to low-lvl dry air. Where temps have climbed into the low 40s...the leading edge of pcpn reaching the ground was falling as -RA. Expect RA/SN to cont advancing NE. NDOT traffic cams indicated snow accumulating on grassy areas along Hwy 136 W of Riverton. Snow is probably accumulating over Gosper/Phelps counties as well. With temps above frzg and concrete/pavement still absorbing insolation...the snow was melting on contact. So roads were just wet attm. Tonight: Snow will overtake the entire CWA. Once the sun goes down and roads and temps cool...snow will begin accumulating on roads. Temps will fall to near 32F and hold steady. The latest blend of mdl QPFs came in a touch higher than prvs fcsts. Snow ratios were capped at 10:1 given near-frzg temp profile. That still resulted in some 6" amts over parts of Dawson/Gosper/Phelps/Furnas counties. Winter Wx Advy conts as posted at 4 AM...but the possibility of 6" amts necessitated upgrading Dawson/Gosper/Phelps/Furnas to a wrng. Given that this is a weak system...and no strengthening expected...and initial melting and compaction due to warm ground...most locations should remain at or below 5". Expect a gradient of 1-5" from SE-NW acrs the CWA with isolated 6" psbl in the warning area. Sat: Snow will taper off and end during the morning from SW-NE. There`s a chance a little snow could linger into early afternoon N and E of I-80...but the accumulating snow will be over. Highs in the 30s. Wind will not be a big issue with this system as there is no sfc low anywhere nearby. E 10-20 mph with some gusts around 25 mph at times. The wet character of the snow will minimize blowing and drifting. After the snow ends...remaining cldy. There is a chance that some patchy drzl could occur. .LONG TERM...(Saturday night through Friday) Issued at 342 PM CDT Fri Mar 13 2020 Aloft: Low-amplitude anticyclonic W-WSW flow will cont over NEB/KS thru a strong low sinks down the W coast...a low remains over Hudson Bay...and a subtropical high remains parked over the Caribbean. The W coast low is fcst to creep slowly inland Wed and this will back winds to SW over the CWA. Some acceleration is psbl Thu as another low dives into the backside of the longwave trof. The last 2-3 runs of the EC/GFS-FV3/CMC are now consistent on lee cyclogenesis Thu night with a new low forming and briefly intensifying over NEB. It is then fcst to weaken on its way into the upr Midwest Fri. Surface: The strong high over Srn Canada will head E Sun. A very wk cool front will form over the Nrn Plns Sun night and it will cross the CWA Mon eve. Behind this front...another big Canadian high will gradually slide ESE into New Eng by Wed. In the meantime...the cool front will become stationary over the Srn Plns. Lee cyclogenesis will begin over CO Wed. This will force the front to lift back N as a warm front. The CO low will intensify Thu. This is still a week there are timing/location diffs between the mdls...but that low is fcst to eject out acrs NEB/KS Thu night into Fri. The warm front will probably lift as far N as the state line. Meanwhile...a Canadian cold front will drop S Thu night and merge with this system...increasing the temp grad. Temps will average at or below normal thru next Fri. The chilliest day will be Sun. Don`t expect much increase in temps before Thu as this entire fcst is looking very cldy. We could see a temporary pop in temps Thu as the warm front gets close...but the cool front will quickly follow Fri. Precip: As with yesterday...NBM has a lot of pops/precip chances that I really don`t think are warranted for large portions of time between Sat night thru Mon night. Am not saying it will be completely dry...but whatever falls will be very light and minor. Changed the character of the precip to drzl as clds will be very shallow and all liquid/no ice. The next legit rain chances will arrive Tue night into Wed and then Thu-Fri. Rumbles of thunder still possible...espcly Thu night. This Thu-Fri system could be a soaker for S-cntrl NEB...espcly W and N of the Tri-Cities. Hvy wet snow will be psbl NW fringe of the CWA. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Sunday) Issued at 653 PM CDT Fri Mar 13 2020 Significant wx: Prolonged period of IFR conditions. Tonight: High confidence for IFR CIGs and VSBYs. Minimum CIGs and VSBYs could drop to LIFR at times during heaviest bands. E winds will gradually incr this eve, with gusts 20-25kt overnight. Expect 2-5 inches of snow accumulations during this time. Saturday: High confidence IFR CIGs through much, if not all of daytime hrs Sat. IFR VSBYs will most likely be ongoing at start of the period in continued -SN. Additional inch or so of accumulation expected 12-18Z. Eventually, expect VSBYs to improve to MVFR levels by mid to late morning as snow decr, but lingering boundary layer moisture and upslope component to winds may allow light fog to continue thru daytime. Expect continued IFR CIGs and return to IFR VSBYs Sat night. && .GID WATCHES/WARNINGS/ADVISORIES... NE...Winter Weather Advisory until 4 PM CDT Saturday for NEZ039>041- 046>049-061>064-074>077-083>086. Winter Storm Warning until 4 PM CDT Saturday for NEZ060-072-073- 082. KS...Winter Weather Advisory until 4 PM CDT Saturday for KSZ005-006. && $$ UPDATE...Thies SHORT TERM...Kelley LONG TERM...Kelley AVIATION...Thies
Area Forecast Discussion
National Weather Service Great Falls MT
859 PM MDT Fri Mar 13 2020 .SYNOPSIS... A major winter storm will continue to impact the Northern Rockies tonight and through the day on Saturday. Snow, blowing snow, and cold temperatures will accompany this storm, with the worst conditions expected across North Central and Central Montana. Near blizzard like conditons are even possible between the Rocky Mountain Front and Interstate 15 corridor tonight. && .UPDATE... The evening update has been published. Winter storm continues with the most impacts being observed just northwest of a Helena to Great Falls line. Periods of heavy snow and strong winds will continue in these areas for much of the night. Further east precipitation has been slower to materialize but it should increase during the overnight hours. No changes were made to the current winter headlines and only minor adjustments were made to the current forecast. && .AVIATION... Updated 600 PM MDT Fri Mar 13 2020 (14/00Z TAF Period) Snowy conditions with gusty winds are expected for the Central/North- central terminals through Saturday afternoon and likely the entire period for KLWT, and KHVR. This will result in widespread MVFR-LIFR. Winds will gradually become more northerly from west to east tonight into Saturday morning. The southwest terminals will likely observe falling ceilings tonight, with chances for snow showers increasing after 4Z. MVFR conditions can be expected with some IFR, mostly for KWYS. Mountian obscurations and aircraft icing is expected. && .PREV DISCUSSION... /ISSUED 609 PM MDT Fri Mar 13 2020/ Rest of this afternoon through Saturday night...the biggest concern and focus with the afternoon forecast has been on the winter storm now impacting the region, in addition to the potential for record to near record low temperatures Saturday night/Sunday morning across North Central and Central Montana. Snow has developed along the Rocky Mountain Front as expected early this morning, and has been slowly backing/advancing eastward over the plains of North Central and Central this afternoon. Easterly low to mid-level winds have and will continue (for portions of the evening) lead to precipitation shadowing immediately to the west of the Island Ranges (i.e. Sweet Grass Hills, Highwood, Bears Paw, Moccasin, Judith, Snowy, and Little Rocky), which will ultimately lead to lower snowfall totals of 4-7" here (portions of Eastern Cascade, Western Fergus, Eastern Chouteau, and Eastern Toole Counties). Elsewhere, snowfall totals by the end of the storm Sunday morning will generally range from 10-20" along west of the I-15 corridor and north of the Montana Highway 200 corridor, to 7-14" east of the I-15 corridor and across the remainder of North Central and Central Montana. Across Southwest Montana, lower elevation snowfall of 2-6" is generally expected, with 6-12" at pass level and in the mountains along the Idaho/Wyoming border. All of the Winter Storm Warnings remain in place across the region, and Winter Weather Advisories are now in place for all of Southwest Montana. Travel will become very difficult and hazardous this evening and during the overnight hours across North Central and Central Montana, especially along and west of the I-15 corridor. Here a push of 6hr pressure rises of 3-6mb along the Rocky Mountain Front combined with H850 winds of 25-35kts are expected to lead to a prolonged period of strong and gusty northerly winds. While blizzard conditions remain a possibility, especially between 00z-09z Saturday, confidence remains to low to issue blizzard highlights. None-the-less, intense snowfall rates of 1-2" per hour during this timeframe and at these locations combined with the winds will likely lead to near-blizzard like conditions. Finally, a very cold night is expected Saturday night/Sunday morning as a strong surface high settles over the area, with the potential for record or near-record temperatures. -Moldan Sunday through Next Friday...A shortwave moves northeast through southwest Montana Montana into eastern portions of plains during the day on Sunday. This will keep snow going over these areas with the most impacts being confined to the southwest. The Winter Weather Advisory issued for the southwest handles the anticipated impacts well. Upper level troughing remains over the region through next week for continued cooler than average conditions, especially considering the snow pack that should be in place after the storm this weekend. A mid-upper level low center within the broader upper trough is expected to slowly drop southward along the CA coast early next week before swinging through the SW US and eventually ejecting out into the central US Plains region late next week. This trajectory would keep the threat for significant precipitation mostly to the south of the forecast area, but some weak energy does looks to move through the region late Wednesday through Friday and the low lifting NE into the central US is close enough to bear watching as any shift northward in its track would bring greater precipitation chances to the forecast area. Temperatures will moderate through the first half of next week but likely max out in the 20s and 30s for most of north- central MT while warming into the 40s in SW MT valleys by Tuesday and Wednesday. As low pressure passes south of the region Thursday and Friday some colder air will likely be drawn south from Canada into Montana. && .PRELIMINARY POINT TEMPS/POPS... GTF 1 6 -10 13 / 100 100 100 40 CTB -8 0 -13 11 / 100 100 40 20 HLN 3 11 -2 23 / 100 100 80 50 BZN 14 27 5 30 / 30 40 80 80 WYS 16 33 19 39 / 70 100 100 90 DLN 20 32 13 34 / 20 30 70 70 HVR 12 20 4 20 / 100 100 100 40 LWT 16 22 0 18 / 90 90 100 80 && .TFX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 4 PM MDT Saturday Broadwater... Jefferson. Winter Storm Warning until 4 PM MDT Saturday Central and Southern Lewis and Clark. Winter Storm Warning until 6 AM MDT Sunday Blaine...Cascade... Chouteau...Fergus...Hill...Judith Basin...Liberty. Winter Weather Advisory from 6 AM Saturday to 6 PM MDT Sunday Beaverhead...Gallatin...Madison. Winter Storm Warning until 6 AM MDT Sunday Meagher. Winter Storm Warning until 4 PM MDT Saturday Eastern Glacier... Eastern Pondera...Eastern Teton...Northern Rocky Mountain Front...Southern Rocky Mountain Front...Toole. && $$