Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/21/18

Area Forecast Discussion
National Weather Service Denver/Boulder CO
819 PM MST Thu Dec 20 2018 .UPDATE... Issued at 809 PM MST Thu Dec 20 2018 Downslope winds expected to develop along the east slopes of the Front Range and as well as the foothills late tonight and Friday ahead of a relatively weak approaching short wave trough. This already reflected well in the grids so no update is planned at this time. && .SHORT TERM...(This evening through Friday) Issued at 310 PM MST Thu Dec 20 2018 A dry and cool airmass is in place over the state this evening as an upper ridge is in place over the state. Satellite imagery shows the next batch of mid-level moisture heading our way to be out over Nevada this afternoon. Brisk northwesterly flow aloft will continue tonight with gusty winds over the higher mountain ridges. Through tomorrow, short and medium range models show the upper ridge flattening with flow aloft becoming more westerly. This will advect warm air across the state and set up a brief chinook wind situation through the afternoon hours. The HRRR model shows areas of gusty winds extending out from the foothills during the afternoon hours. Model cross sections show most of the wind remaining over the higher foothills, but with a well mixed airmass in the afternoon, we should see some gusty winds from the foothills out to about the I-25 corridor for a few hours. . Gusts of 40 to 50 MPH will be possible. Temperatures on the plains are expected to warm into the upper 50s and lower 60s. By late in the afternoon, the HRRR shows the winds rapidly diminishing. No highlights for the time being. .LONG TERM...(Friday night through Thursday) Issued at 310 PM MST Thu Dec 20 2018 Colorado will be under the influence of a moderate northwest flow aloft from Friday night through Monday. Plenty of moisture, orographic lift and occasional upper level disturbances caught up in this flow will produce periods of snow and breezy to windy conditions across the high country through this period. The first shortwave should produce snow in the mountains Friday evening through Saturday with drier weather on Sunday due to weak upper level ridging. The next system should produce another round of snow across the mountains from late Sunday through Monday. The plains should remain mostly dry through this period with near to slightly above normal temperatures. However, some light snow will be possible across the plains on Saturday due to weak upslope flow and QG lift. For Christmas Day and Wednesday, models show a powerful storm system deepening across the western U.S then moving across the Four Corners Region and Central Plains States. This system has the potential to produce significant snowfall and blizzard conditions across northeastern Colorado. Models have come into better agreement over the past 24 hours, however, there is still quite a bit of uncertainty with the track of this system which would greatly affect snowfall amounts. The 12Z GFS has the most favorable track for heavy snowfall and shows the 500 MB low tracking from the Four Corners Region Tuesday evening into extreme southeast Colorado by noon Wednesday and into north central Kansas by Thursday morning. This solution could produce total snow amounts between 8 and 12 inches across the Front Range Urban Corridor and 1 to 2 feet across much of the plains on Wednesday. However, the experimental GFSF3V (which will become the operational GFS next month) has a much less favorable track further to the south with much less snow amounts. The ECMWF and GEM have similar tracks to the GFS with not quite a bit of snowfall. We will have to continue to closely monitor possible changes in the track of this storm system over the next few days. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 809 PM MST Thu Dec 20 2018 VFR will prevail through the period. Winds are in the process of following the normal diurnal trends and remain light enough that they should have a minimal impact on airport operations tonight. Downslope winds may spread towards BJC by late Friday morning with some gusts in the 25-35 kt range possible after 18z. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Cooper SHORT TERM...Dankers LONG TERM...jk AVIATION...Cooper
Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
555 PM CST Thu Dec 20 2018 .UPDATE... Issued at 548 PM CST Thu Dec 20 2018 Updated for the 00z Aviation Discussion below. && .SHORT TERM...(This evening through Friday) Issued at 329 PM CST Thu Dec 20 2018 A cold front draped across the Northland this afternoon will continue its southward trek tonight while a surface ridge builds eastward into the Upper Midwest. Low stratus is expected to linger for most locations overnight. With skies remaining cloudy, think most of the guidance is too cool over my northern zones. Have raised lows to the low teens in northeast Minnesota with readings in the low 20s in northwest Wisconsin. Northerly winds will keep a potential for lake effect snow over portions of northern Wisconsin, including Ashland, Iron, and Price counties. With shallow upstream moisture and limited lake delta-Ts, don`t expect much in the way of accumulation. Another few tenths of an inch are possible through Friday. The high pressure ridge will slide eastward into the Northland for the end of the work week. Think it will be difficult to clear the stratus, so have held onto a minimum of 50% sky cover through Friday over much of the area. Overcast skies will be likely over northwest Wisconsin with northerly winds keeping lake-induced clouds overhead. Highs will top out near 20 in northeastern portions of the Arrowhead to the upper 20s across our southern zones. .LONG TERM...(Friday night through Thursday) Issued at 329 PM CST Thu Dec 20 2018 A weak system crosses the Upper Great Lakes on Saturday into Sunday and will bring light snowfall accumulations to mainly northern Minnesota (1-2" or so). This is followed by a cool down where light forcing may squeeze a few flurries out here and there. The coldest air arrives overhead Christmas morning in conjunction with a weak short wave which may offer some Christmas flurries. This feature is a little weaker today compared to yesterday, so have backed off on the wording a bit. The main story continues to be the potential for a system after Christmas. Model trends have been relatively stable with most deterministic operational solutions in fair agreement. This gives more confidence to some sort of winter system being in the area, but it`s still too early to flesh out specifics. The GFS Ensembles still vary widely among their different members which lends to a hesitance in advertising this storm too strongly attm. Still quite impressed with the handling of the system among the different deterministic models this far out and their run to run consistency is also impressive. It will be interesting to see how this evolves. Temperatures remain on the warm side of normals throughout the extended period. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 555 PM CST Thu Dec 20 2018 The main focus for this evening and overnight continues to be the MVFR/IFR ceilings that remain in place. Some of the high- resolution guidance wants to scour out this low stratus deck later this evening from north to south, but we`re thinking the stratus will linger through the nighttime hours as the RAP model 950 mb level relative humidity, which has captured the current cloud cover very well, lingers some higher moisture through the night, so leaned heavily on this. Gusts will gradually diminish overnight as the low-level inversion builds, which should also help to keep the stratus deck in place. RAP and NAM model soundings both hint at a return to VFR conditions during the late morning and afternoon hours Friday. && .MARINE... Issued at 329 PM CST Thu Dec 20 2018 Small craft criteria winds and waves will cover portions of the forecast area through Friday morning while waves remain high through Saturday morning along the South Shore. A larger system may arrive after Christmas packing gales, but still too early to tell where it will track and its intensity. && .PRELIMINARY POINT TEMPS/POPS... DLH 17 25 16 27 / 0 0 10 20 INL 14 21 11 26 / 0 0 20 50 BRD 19 28 19 29 / 0 0 10 20 HYR 22 28 17 30 / 0 0 0 10 ASX 24 27 19 29 / 10 10 10 10 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. LS...Small Craft Advisory until 4 AM CST Friday for LSZ140-146-147. Small Craft Advisory until 10 PM CST this evening for LSZ141-142. Small Craft Advisory until 10 PM CST Friday for LSZ148. && $$ UPDATE...JTS SHORT TERM...Huyck LONG TERM...Wolfe AVIATION...JTS MARINE...Wolfe
Area Forecast Discussion
National Weather Service Marquette MI
617 PM EST Thu Dec 20 2018 .SHORT TERM...(This evening through Friday) Issued at 422 PM EST THU DEC 20 2018 Concerns tonight into Friday involve ptype issues and lake enhanced snow amounts for west and north central counties. WV imagery and RAP analysis indicated a mid/upper level trough from Hudson Bay through northwest Ontario and Minnesota to eastern Texas. At the surface, a trough/cold front has worked its way through the nw half of Upper Mi. One area of light rain ahead of the front was still lifting through eastern Upper Mi late this afternoon while light mixed pcpn was occurring over the west. Tonight and Friday, with the advance of colder air behind the front pcpn will continue to switch over to mostly snow late this afternoon into this evening over the west half counties. Dry slotting into central and eastern counties could result in drizzle this evening with a gradual change over to a mix of freezing drizzle/snow overnight. Any light glaze of fzra/fzdz would likely be over far eastern Marquette into Alger counties with likely less than .1 inch of ice accumulation. Lake enhanced snow will develop tonight especially where the upslope northerly flow is strongest over west and north central higher terrain as 875-900 mb temps fall near -10C over the west this evening and overnight for north central counties. Given marginal CAA barely cold enough for adequate ice nuclei, expect low SLR ratios closer to 10/1. This will result in one to two inches of wet snow accumulation for most locations with perhaps 3-4 inches over the Michigamme Highlands tonight into Fri. Drying at mid- levels from the west during the day on Friday will result in snow quickly tapering off with minimal additional accumulation. Expect min temps in the 20s tonight with highs Friday from the mid 20s west half to lower 30s south central and east. .LONG TERM...(Friday night through Thursday) Issued at 241 PM EST THU DEC 20 2018 Broad upper level troughing from central and eastern Canada across the Great Lakes results in a colder weather pattern through the weekend and early next week. Then, attention just beyond Christmas turns to developing western Conus trough and the possibility for first widespread accumulating snow in quite some time across much of Upper Michigan late Wednesday and/or Thursday. Though it is day 7 and the upper level system is still west of Alaska, that system certainly bears watching as it could impact travel after the holiday. Friday night into Saturday: Cold northerly low-level flow in wake of the trough moving through today may still support light lake effect snow showers/flurries Friday night over mainly north central. Stays blustery good part of Friday evening with north winds over 25 mph, strongest over north central around Marquette and Munising. Given a north wind may be breezy down toward KI Sawyer as well. Saturday looks quiet as high pressure ridge crosses. Saturday night through Christmas: Shortwave crossing southern Manitoba into Ontario along with sfc low will support a batch of light snow mostly over Keweenaw Saturday night and possibly spreading across rest of north and eastern Upper Michigan on Sunday. Mostly light snow but as this system passes and winds turn w-wnw Sunday aftn into Sunday night, lake enhanced snow may increase over Keweenaw and in snow belts east of Munising. Quick hitter but actually does get kind of chilly with H85 temps down to -14c and with lake temps of +4c that pushes delta t/s to around 18c. Forecast soundings show inversions up to 8-9kft. For a change, decent amount of DGZ is within the lake moist convective layer. Sure seems that conditions would be favorable long enough for advisory level snowfall to occur in the areas favored by wnw winds. Inversions fall quickly on Monday and into Christmas Day so although light LES will continue in wnw flow areas near Lake Superior, not looking at much for accumulations. Temperatures this weekend into early next week will end up at or slightly above normal with highs mostly in the mid to upper 20s and lows in the teens to lower 20s. Wednesday-Thursday: Wednesday will start out with light LES for wnw flow areas near Lk Superior but then LES will shut down as winds become more e-se ahead of approaching system. Later Wednesday night and maybe as late as later Thursday (per 12z ECMWF) more widespread wintry precipitation may affect much of Upper Michigan. Stronger lead shortwave trough will support strong lee Rockies cyclogenesis/sfc low Wed. Sfc low will deepen as it crosses the southern Plains then maintain similar intensity as it lifts toward western Great Lakes Wed night, through again the latest ECMWF is much slower with this solution, not bringing the sfc low into our area until late Thursday at a weakened state. Certainly could see a period of at least moderate wet snow as the system lifts toward Upper Great Lakes and maybe the snow would then change to mix of wintry precip or only rain. Really tough to get into the specifics this far out though considering main system will not move onshore over northwest Conus until Monday at the earliest. Guess the main takeaway at this point is those with travel plans in the region just after Christmas will want to keep eye on later forecasts as we get closer to this time frame. Probably not a good idea to get too locked into any one specific model solution at this time as there will likely be significant changes into next week between the models/ensembles and even run-to-run variations of the same model. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 617 PM EST THU DEC 20 2018 A prolonged period of low cigs and/or visibilities will continue this forecast period for all sites. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 422 PM EST THU DEC 20 2018 A trough passage today followed by deepening low pres lifting nne toward the Lower Great Lakes, will lead to a period of stronger nnw- n winds this afternoon into Friday. Some gale force gusts over central and eastern portions of Lk Superior will be possible late today into Friday as colder air arrives behind the trough, but doesn`t appear that the gales will be widespread or long lasting enough to have a gale warning out. N-NW winds to 30 kts continue into Friday, strongest over the east half. Winds diminish to 25 kts or less by Saturday as sfc high pressure ridge briefly crosses. Another trough crosses the area on Sunday, but even then winds should remain only up to 25 kts late Sunday into Sunday night. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Voss LONG TERM...JLA AVIATION...07 MARINE...Voss
Area Forecast Discussion
National Weather Service Nashville TN
819 PM CST Thu Dec 20 2018 .UPDATE... FOR EVENING DISCUSSION. && .DISCUSSION... Surface low has moved to our east, so we`re getting plenty of wrap-around moisture this evening and overnight and into tomorrow. Radar imagery currently shows a break in the rain across much of Middle Tennessee, although the HRRR keeps generally light precipitation over the mid state the remainder of the night. Rain will start to exit the region tomorrow morning. Current forecast grids are in good shape so no changes are planned this shift. && .AVIATION... 00Z TAF DISCUSSION. Poor flying conditions as all mid-state terminals continue to deal with IFR or worse. KCSV is running VLIFR and will likely remain that low throughout the night. Categories will improve very slowly Friday, with rain ending from west to east. Winds will be light out the north for a couple more hours before gusts begin to spread across all terminals about 06Z. These breezy NW winds will persist through the remainder of the TAF cycle. && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION......08 AVIATION........Unger
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
408 PM MST Thu Dec 20 2018 .DISCUSSION...(This Evening Through Thursday) Issued at 147 PM MST Thu Dec 20 2018 Upper level analysis shows a deep trough over the eastern states, and a ridge building over the west. Skies are mostly sunny across the region. At the surface, winds are westerly around 10-15 mph, and temperatures are in the 40s. Upper ridging over the northern plains will be short-lived, as a fast-moving wave sweeps in from the Pacific Northwest on Friday. Some light rain/snow showers could skirt the northern third of the CWA on Friday, with little to no snow accumulations. Winds will become gusty behind the cold front Friday afternoon. Models are showing 3-6 mb/3 hr pressure rises across portions of western SD, and CAA is expected to be stronger than that of yesterday. NAM and GFS forecast soundings show 30 to 45 kt winds mixing down, especially around the Rapid City area, and the HRRR has 40 to 50 kt gusts possible from Meade County down through Jackson and Bennett. May need a Wind Advisory, but since this isn`t expected until tomorrow afternoon - and maybe only for a few short hours - will let later shifts determine if the next model runs also support this. Cooler air will settle into the region for the weekend. Highs will be in the 30s to lower 40s Saturday through Christmas Eve, with dry conditions expected. Still watching the potential for a post-Christmas snowstorm across the region. The 12Z ECMWF has slowed down the track of the low, and aligned it more with the Canadian and GFS, keeping it farther south and east than the 00Z EC run. These solutions continue to place most of the snowfall across Nebraska and eastern SD, but our CWA could still see some significant snowfall. At this time, it looks like snow will start moving into the CWA Christmas afternoon/evening, exiting Thursday afternoon/evening. However, there is plenty of time for the track and timing to change. && .AVIATION...(For the 00Z TAFS Through 00Z Friday Evening) Issued At 408 PM MST Thu Dec 20 2018 VFR conditions are expected through the forecast period. Ahead of a quick moving system, winds will increase late tonight in northeastern Wyoming along with increasing mid-to-high level clouds. Much of the region will see winds turn northwesterly and gust to 30-35 knots by late Friday morning into the afternoon after cold front passes through the region. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ DISCUSSION...Pojorlie AVIATION...Eagan