Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/13/22

Area Forecast Discussion
National Weather Service State College PA
1038 PM EST Wed Jan 12 2022 .SYNOPSIS... Mainly dry weather will last into Thursday with just some scattered snow showers and flurries over the Alleghenies of Northern and Western PA overnight. A better chance for snow showers and a light accumulation arrives across the Central and Western Mountains of the state late Thursday and Thursday night as a compact but deepening upper trough drops SE across the Middle Ohio River Valley. Colder weather returns Friday and lasts through the weekend. Light snow/showers are possible over the Alleghenies tonight and could make a dusting of snow there. We are continuing to monitor the winter storm potential later Sunday into Monday. Way too early for any details. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Plenty of thick and higher based altostratus with virga covered much of the region this evening, with thicker, layered and lower based NS clouds streaming across our NW zones with some light snow/snow showers. The weak upper trough and llvl warm advection creating this spotty light precip will weaken/shear out to the ENE late tonight/early Thursday, perhaps giving a light coating of snow to some places to the northwest of the 1-99/RT 220 corridor. Latest RAP and HRRR guidance are quite spotty on precip/snow accums tonight. Temps are the mildest this evening just SE of the Allegheny Front where a weak downslope south to SW flow accompanied an earlier onset to the thicker clouds, compared to the Susq Valley where readings are 5 to 10 deg F cooler in many locations. The relatively thick cloud cover and light SW sfc wind should keep it milder than normal across much of the area tonight. The coldest locales will be in the east where the wind should stay light for the rest of the overnight. Mins in the 20s for most places. However, the ridgetops of southern PA should stay AOA 30F. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... A sharpening upper trough drifting SE across the Ohio Valley and toward the Central Appalachians will have just enough cold air in the blyr and mid/upper level forcing to produce thick, multi-layered seeder-feeder clouds and some snow showers/few brief periods of steady light snow across mainly the western Mtns late thursday afternoon and night. Will have to keep a close eye on the potential evolution of a transient, mesoscale FGEN band of moderate snow across the Wcentral or SW mountains closer/just to the north of the mid level low track. For now, a light coating Central and NW around one inch across the higher terrain of the Laurels appears probable by late Thursday night. Maxes in the u30s-m40s prior to the onset of the cooling precip will be 5-10F above climo (again). Cold air advection will then bring the 8H temps down into the -4C to -8C range and generate some lake effect clouds and sct -SHSN by sunrise Fri. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Below normal temperatures will return for late in the week through the weekend and into next week as an upper low swinging through Hudson Bay combines with the deepening trough off the Delmarva Coast (and freshening northerly llvl flow) to bring our next shot of Arctic air (and likely the coldest temps of the Winter so far) to much of Central PA Fri night through Sat night. The leading edge of this associated cold front will push into the Commonwealth Thursday night, keeping high temperatures Friday in the lower 20s across the northern tier of PA while locales near the Mason-Dixon line warm into the mid and upper 30s ahead of the front. The greatest chc shot of any snow/rain showers accompanying this arctic boundary looks to be across the Alleghenies where upslope will help enhance the lift locally. Drier air should prevail across the Susquehanna Valley as a storm off the mid- Atlantic Coast results in some relatively drier air advecting in on its far northwest flank. Dry and quite cold conditions will occur for Saturday into early Sunday as surface ridging builds south into northeast PA. Low temperatures Saturday and Sunday mornings look to dip into the single digits for many, with a good bet of some below zero readings throughout the perennial colder rural valleys of the Central and North as extensive radiational cooling occurs. Focus then turns quickly to the potential high impact and widespread Winter Storm whose service reflection will be moving NE up along the I-95 corridor Sunday into early Monday. Initially P-type should be all snow and last for at least the first half of the even, even across the SE half of the state, where minor changes in the storm track could equate to major differences in precip types and snow accum. Highest confidence for a plowable and high impact snowfall exists across the Central and Western Mtns ATTM, however, this doesn`t rule out the potential for the heaviest snow to occur near the I-81 corridor. Phasing of the initial split flow and significant northern and slightly lagging nrn stream energy is handled quite well with respect to timing and location by GFS and EC along with their ensembles. We increased pops 80-95 percent for the meat of the storm Sunday night. Main message is to pay attention to forecasts over the next several days as/if confidence in details emerges. This certainly has the makings of the largest storm of the winter thus far, but much can change over the next 5 days. Have increased pops significantly for Sunday into Monday, while also highlighting the storm potential in the Hazardous Weather Outlook. Post-storm will likely feature a period of gusty northwest winds and lake effect snow showers as cool temperatures remain in place. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... Not a lot of change for the 00Z TAFS. Most of the area will see VFR conditions with dry weather into Thursday. Western areas will likely see lower CIGS later tonight into Thursday, with perhaps a few snow flakes. Outlook... Thu night-Fri...Restrictions west in -SHSN. Sat...No sig wx. Sun...Possible restrictions late in -SN. Mon...Possible restrictions early in -SN. Improving conds second half of day. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert/Dangelo NEAR TERM...Lambert/Dangelo SHORT TERM...Lambert/Dangelo LONG TERM...Guseman/Lambert/Gartner AVIATION...Martin
National Weather Service Sioux Falls SD
504 PM CST Wed Jan 12 2022 .SHORT TERM...(This Evening through Thursday) Issued at 251 PM CST Wed Jan 12 2022 Similar to yesterday, temperatures have risen to near or above the NBM the percentile, reaching the 40s to mid 50s by mid afternoon. Seasonably mild conditions will continue overnight and through Thursday. Northwest flow aloft brings another weak shortwave from the Canadian Prairie toward northern WI tonight. Associated with this disturbance, occasional HRRR and NAM runs try to eek out very light precipitation in southwest MN late tonight, but model soundings largely suggest forcing will be too weak to saturate a deep enough layer for precipitation to develop. With substantial mid and low level dry layers, increased cloudiness would be the main impact with little to no ice nuclei introduction. Maintained flurries but sfc temperatures hovering around near or below freezing mark could mean potential for a few slick spots if anything reaches the sfc. Thursday will be the last in this string of milder days as strong ridging upstream edges closer to the region. Although we`ll mix some into warmer air aloft, CAA behind the departing sfc trough will inhibit heating from insolation Thursday morning. Based on persistence over the past few days and potential to again mix higher than expected, bumped highs up to NBM 75th percentile. Look for highs to be slightly cooler than the past few days, reaching the 30s to upper 40s. .LONG TERM...(Thursday Night through Wednesday) Issued at 251 PM CST Wed Jan 12 2022 For late Thursday night through Friday night, the main impact is widespread snow accumulations as a strong clipper tracks from the Canadian Rockies southward through the High Plains. On Thursday night, a strong LLJ ramps up WAA ahead of the approaching sfc trough extended N-S through the western Dakotas. The past few sets of model runs continue to agree with tracking the 700mb low right near or east of the I-29 corridor, suggesting the most prolonged WAA regime and mid level frontal forcing will linger longest near and east of the I-29 corridor. Temperatures aloft should cool enough with the approaching wave for deep column saturation (including through the DGZ) to bring snow spreading in from the north Friday morning. Expect periods of snow to impact travel through the day Friday and especially Friday afternoon and night. The latest 00z/12z guidance also supports a slightly slower and stronger wave, which would keep snow lingering through Friday night. Snow amounts are still quite uncertain for the Friday system. Snow amounts are likely to be notably lower in south central SD (than further east), where mid level dry air and weaker forcing may bring a light wintry mix/glaze of ice to areas north of I-90 Friday morning. 06z/12z GEFS ensemble guidance continues to shift higher probabilities of >=6" of snow further west, now into areas east of the James River Valley, though the GEFS plumes still have a wide spread (low confidence) in totals for any one location. Conversely, the 12z Euro ensemble guidance holds those better chances of higher (6+) totals east of I-29. Given the slightly increased confidence in higher amounts from the deterministic and GEFS guidance, opted to add counties along the I-29 corridor to the Winter Storm Watch. Additionally as the sfc trough drifts southeast, the trailing tight pressure gradient will mean north winds at 10 to 20 mph with gusts up to 35 mph. Collaboratively bumped up winds to NBM 90th percentile for Friday afternoon and night. Gusty winds while snow and temperatures are falling Friday evening may make difficult travel conditions as patchy blowing snow reduces visibility. Those planning regional travel Friday through early Saturday will want to monitor the forecast closely as the weekend draws nearer. By Saturday, temperatures will drop considerably with wind chills below zero looking increasingly likely Saturday morning. Strong Arctic high pressure, in the top 10% of NAEFS guidance for this time of year, will build through Saturday with decreasing winds and followed by highs only reaching the teens and 20s. GEFS guidance favors a subtle warm up Sunday before a weak (likely dry) frontal passage. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 503 PM CST Wed Jan 12 2022 VFR through the period. Big changes late Thursday night into Friday with snow likely. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...Winter Storm Watch from late Thursday night through Friday evening for SDZ039-040-055-056-062-067. Winter Storm Watch from Friday morning through late Friday night for SDZ071. MN...Winter Storm Watch from late Thursday night through Friday evening for MNZ071-072-080-081-089-090-097-098. IA...Winter Storm Watch from late Thursday night through Friday evening for IAZ001. Winter Storm Watch from Friday morning through late Friday night for IAZ002-003-012>014-020>022-031-032. NE...Winter Storm Watch from Friday morning through late Friday night for NEZ014. && $$ SHORT TERM...BP LONG TERM...BP AVIATION...08
National Weather Service Hastings NE
1002 PM CST Wed Jan 12 2022 .UPDATE... Issued at 1002 PM CST Wed Jan 12 2022 Update to increase wind gusts a bit to match up more with the RAP, near 20 mph or so behind a trough passing through tonight. && .DISCUSSION...(This evening through Wednesday) Issued at 255 PM CST Wed Jan 12 2022 Overview... We get one more really nice day tomorrow, at least nice by January standards, with highs back into the 50s on Thursday. A strong cold front will bring gusty winds, much cooler weather, and a mixed bag of precipitation to the area Friday through Saturday morning. However, this will be a quick hitting system and we should rapidly rebound into the 40s for highs on Sunday and Monday, with perhaps more 50s by Tuesday. The next cold front could bring cooler weather by around the middle of next week. Thursday... We over achieved on temperatures today and would not be surprised if we are warmer than most of the models again tomorrow. Therefore, went a little above the NBM for high temperatures. Overall just another great day. Friday through Saturday... A strong cold front will enter our northwestern zones Friday morning and then race southeast across our forecast area Friday afternoon. The chance for precipitation Friday morning is low and would most likely be rain if we see anything with northeastern zones being more favored for precipitation. We could see a little bit of a mixed back of precipitation Friday afternoon as temperatures cool behind the cold front. Although freezing drizzle/freezing rain, sleet, and snow will all be possible Friday afternoon and early evening, the most likely frozen precipitation type will be snow. The chance for freezing rain will further transition more into a chance for snow as we get into the Friday late night hours. Precipitation chances throughout this event will be highest east of our forecast area with the winter storm watches out across Iowa, and higher snow chances over eastern Nebraska. Our eastern zones could see some light precipitation, but some western zones may remain dry or see only trace amounts. The NBM seems too low with snow chances Saturday morning given the forecast location of a closed 500 mb low just to our south. The 12Z ECMWF indicates the possibility for some light wrap around snow Saturday morning. Therefore, increased snow chances above the NBM Saturday morning. Also increased the wind speeds above the NBM Friday through early Saturday. Strong wind resulting in blowing snow could be an issue for areas that see an inch or so of snowfall. Saturday will be the coldest day of the week behind the cold front with highs only in the 20s. Sunday through Tuesday... The cold air will push east and the next clipper will largely miss us to the east so we can expect moderating temperatures due to a western United States upper ridge and westerly/northwesterly downslope flow. The timing of the next cold front is rather uncertain this far out and could come as early as Tuesday, which would mean our forecast temperatures on Tuesday could be too high. Wednesday... We should be behind the next cold front and thus cooler again. This clipper also doesn`t appear to have much if any precipitation threat with it. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday) Issued at 558 PM CST Wed Jan 12 2022 Main issue for this forecast will be LLWS behind a surface trough passing through tonight. Wind aloft will be strong enough aloft behind the trough to include this issue, assuming there is a certain amount of decoupling to prevent much of these winds to translate to the surface. Given RAP wind gusts do not values over 20 KTS while 850 mb winds are forecast at 35-40 KTS by some models, this would indicate the potential for LLWS being an issue during a block roughly near 09Z to 15Z Thursday. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ UPDATE...Heinlein DISCUSSION...Wesely AVIATION...Heinlein
Area Forecast Discussion...UPDATED
National Weather Service Twin Cities/Chanhassen MN
924 PM CST Wed Jan 12 2022 .UPDATE... Issued at 924 PM CST Wed Jan 12 2022 The forecast remains steady for Thursday night and Friday`s winter storm, for now. 21Z RAP and 00Z HRRR have shifted their bands quite a bit to the east, but the remaining 00Z guidance so far have not. Did not make too many changes for now while the rest of the guidance trickles in. Rarely do models make drastic changes within this time range unless there is a clear trend. It will be interesting to see if 06Z or 12Z models make the same jump or if the HRRR and RAP had some issues. It is a little peculiar this clipper would make such a deep dive almost due south given the current flow pattern. If the trough doesn`t end up as deep and positively-tilted throughout the Plains as is currently forecast by several models, then a more typical track to the southeast could probably be expected like that of the RAP and HRRR. The 500 mb pattern at 48 hours is surprisingly different between the HRRR/RAP and everything else. Ensemble spread is still fairly large, but the GEFS does seem to be tightening its gradients a little. Given low confidence with emerging trends (if any), left the forecast alone for now aside from extending the watch through Friday evening. && .DISCUSSION...(This evening through Tuesday) Issued at 349 PM CST Wed Jan 12 2022 Temperatures have overachieved today across portions of central and southern Minnesota under clearing skies. While it feels positively spring like here in the Twin Cities, the record high for today is well out of reach at 48 degrees. Cloud cover will increase through this evening with a weak disturbance bringing a chance for some scattered snow showers. There`s a slight chance for a period of wintry mix across western and central Minnesota where thermal profiles suggest a warm nose hanging around through the overnight. However, anything that does fall will be light, so little to no precip accumulation is expected. Some patchy fog is also possible overnight across eastern Minnesota and western Wisconsin where we still have some decent snowpack. Lastly, whatever managed to melt during today`s warm up may create some slick spots as things refreeze overnight. Thursday will be cooler as CAA fills in behind tonight`s disturbance with highs in the mid 20s north to low 30s south. We will remain dry through the early evening, but cloud cover will persist ahead of our next system working in from the west. Thursday late evening is when things begin to get interesting. Snow chances commence a few hours prior to midnight in western Minnesota and chances will pick up through the night as the system spreads eastward. By 6AM, nearly all of west central and south western MN should expect snow to be ongoing. By noon, the snow will continue to spread further east and include the Twin Cities. The Metro and west central Wisconsin will see the best chance for snow between 7AM and noon. As the day goes on, snow chances will linger and then cease by late evening. At this time, the range of snow totals over the seven county Twin Cities metro is less than ideal, with our lower end forecast being less than 2 inches and the higher end potentially dumping upwards of 5-6 inches. This range should tighten up as we near the event. Counties that are currently in the Winter Storm Watch will see the most snow, with a potential for 9+ inches in areas that fall within the heaviest band. West central WI will see the least amount of snow, with the potential of seeing no more than a dusting. As goes with all winter events a few days out, the exact track of the low can still shift slightly, despite consistent model agreement at this time. Unfortunately for those in the seven county Metro, a slight shift could be the difference between 1 inch of snow and 5 inches of snow. Again, as the event approaches, this uncertainty will shrink. For now, we are decently confident that areas west of the MN/WI border will see at least an inch of snow. With fresh snowpack from Friday and Canadian high pressure settling in, Saturday will be cold and dry. Temperatures rebound a bit Sunday toward mid January normals and will remain there to start the week. Our next chance of precip doesn`t come until late in the period on Tuesday. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 607 PM CST Wed Jan 12 2022 VFR this evening with some MVFR cigs developing late tonight and Thursday. Fog is possible late tonight at AXN, but confidence is fairly low due to lack of low clouds upstream and steady northwest winds. KMSP...MVFR cigs are possible Thursday afternoon, otherwise no concerns. /OUTLOOK FOR KMSP/ Fri...IFR/-SN likely. Wind E 10 kts. Sat...VFR. Wind N 5-10 kts becoming S. Sun...VFR. Wind SSW 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...Winter Storm Watch from late Thursday night through Friday evening for Blue Earth-Brown-Chippewa-Faribault-Kandiyohi-Lac Qui Parle-Martin-Nicollet-Pope-Redwood-Renville-Sibley-Stevens- Swift-Watonwan-Yellow Medicine. WI...None. && $$ UPDATE...Borghoff DISCUSSION...Dye/Marten AVIATION...Borghoff