Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/02/16

Area Forecast Discussion
National Weather Service La Crosse WI
529 PM CST Thu Dec 1 2016 .UPDATE... Issued at 322 PM CST Thu Dec 1 2016 With the latest RAP soundings, showing a saturated sounding up to 1.5 km and some omega (ahead of a short wave trough moving south through Minnesota) in this layer, added drizzle to the forecast through midnight tonight. && .SHORT TERM...(This evening through Friday) Issued at 220 PM CST Thu Dec 1 2016 At 2 PM, a closed low was located over eastern Ontario and western Quebec. With this low moving away from the area, much of the area has been dry this afternoon. The only thing that we will have to watch tonight is a weak short wave moving south through northern Minnesota. The radars have been pretty quiet with this system. However, there was a recent report of unknown precipitation at Aiken MN. With the soundings not showing much lift across the region, opted to keep the forecast dry for now. The only other issue tonight looks to be the low temperatures. With persistent cloud cover and neutral temperature advection, the MOS temperature look too cold. As a result, did a trajectory analysis to see where this air mass was this morning. This revealed that this air mass was over northern Minnesota and the temperatures were near 30F this morning. Due to this, opted to raise the low temperatures closer to these values tonight. .LONG TERM...(Friday night through Thursday) Issued at 220 PM CST Thu Dec 1 2016 From Saturday night into Sunday evening...the 01.12z models continue to show that a short wave trough will move east through the region. Soundings continue to show that the temperatures aloft and at the surface will be cold enough for the precipitation to start out as snow. However there is some indication in the NAM that there may be a lack of icing initially which could could result in maybe some patchy freezing drizzle. With surface temperatures warming into the mid and upper 30s on Sunday, the boundary layer will sufficiently warm for the snow to change to either a mix of rain and snow or to all rain. As far as snow totals, the SPC plumes show that most of the models have snow totals ranging from a dusting to maybe up to a half inch. Beyond Monday, the models continue to show a wide variety of solutions. Some show that the northern and southern streams will phase over the region. This would result in a strong low moving through the Midwest. Meanwhile, other models show no phasing at all. In this scenario, we would be split and would see no precipitation at all. With the 01.12z ECMWF was running 3 hours late due to a power failure, did not get a chance to look at that model at all. As far as the temperatures, the models continue to show that the 850 mb temperatures will plunge into the -10C to -15C range. While this will be cold, it is not that unusual for December. The models continue to show a large spread with standard deviations up to 7. This is a result of uncertainty on the snow extent across the region. If the ground remains snow free, high temperatures would range from the mid-20s to the mid-30s. If we become snow covered, we would see high temperatures anywhere from the teens to the mid- 20s. Due to this uncertainty, just stayed with model blends for now. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 529 PM CST Thu Dec 1 2016 No significant changes are expected to occur through Friday. The area of low pressure south of Hudson Bay will remain nearly stationary which will maintain the low level cyclonic flow over the Great Lakes Region. With lots of low level moisture stuck in this flow, the clouds will remain in place with little movement in the ceiling heights expected for an extended period of MVFR conditions. There could also be a little bit of drizzle this evening as a mid level short wave trough rotates over the area. Not expecting this to produce any visibility restrictions, so for now, will keep this out of the forecasts. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ UPDATE...Boyne SHORT TERM...Boyne LONG TERM...Boyne AVIATION...04
Area Forecast Discussion
National Weather Service State College PA
1011 PM EST Thu Dec 1 2016 .SYNOPSIS... A large and deep storm system will move slowly through Quebec over the next couple of days keeping a prolonged period of cool northwest flow over the local area. High pressure will build in for a brief time Sunday before the next frontal system approached early next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... No big changes late this evening as lake effect regime continues tonight. Lake clouds and flurries hugging areas along and north of the PA/NY border this evening are showing a slight southward drift. Latest HRRR in good agreement with this trend for the backing flow upstream flow evidence in northeast Ohio should bring this to fruition. Expect an increase in snow shower activity after midnight across the north. Boundary layer and sfc marginally cold and bands not expected to become very organized. However...a light accumulation will be seen over my northern tier overnight. Some sprinkles still mixed in in areas where lighter precip rates occur. Mins will be fairly uniform throughout...ranging from the lower 30s northwest to the lower to middle 30s elsewhere. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... The cold NW flow will remain air in place for Friday, but again the cold air is unimpressive so NW snow shower activity is not expected to amount to more than nuisance amounts. With high temps expected to be above freezing, most areas will ave a hard time making any snow stick at all. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... As low continues to move further east into the Canadian Maritimes, lake effect snow showers over the NW mtns will gradually wind down on Sat. But one last shortwave Fri night could be enough to extend snow bands into parts of the central mtns for a time. Sunday brings a brief respite as high pressure moves over the state. By late Sunday into the overnight, a period of light snow is possible as a northern stream shortwave races through the region with a burst of warm advection. QPF looks to be on the order of a tenth of an inch or less, but occurring overnight many places could see their first coating of snow of the young season by Mon morning. Another ridge moves through on Monday as progressive weather pattern becomes more active. On Tues there is decent agreement in bringing the SW US upper low up through the OHIO Valley as a shearing out shortwave and diffuse surface low. Unless cold air damming traps enough chilly air in the low levels to make for some freezing rain, the precip type with this midwest system looks to be mainly rain. The end of the week brings some model disagreement with the GFS/GEFS being faster than the ECMWF with the next large upper trof and frontal system. Either way, precip looks like a good bet around the Thu/fri period as all solutions eventually bring this trough through. So predictability is increasing, but timing issues remain. Best bet for precip at this point is mainly rain over the SE as decent push of warm air lifts ahead of the system, with a rain/snow mix further north where warm air will not infiltrate as much. Behind the trough, looks like a chilly weekend in store with a potential sharp dropoff in temps. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... Widespread MVFR to low end VFR CIGs will persist through the overnight over the favorable cold advection/upslope region from KBFD to KJST (and possibly extending briefly at times into the KUNV/KAOO areas), with VFR, BKN-OVC conds across the east scattering out late across the Lower Susquehanna Valley airfields - KMDT, KLNS, KMUI and KTHV. An initial mean WSW wind flow in the boundary layer will keep lake effect snow showers mainly north of the PA/NY border through 05Z Friday. Last several runs of the HRRR and BUFKIT time/height cross-section continues to show a slight (10-15 degrees) veering to the mean wind within the sfc-850 mb layer (to about 280-285 deg) which will cause the bands of enhanced lake effect snow showers to shift slowly south from the Western Southern Tier counties of NY, into NW Pa at times late tonight and Friday. Thus, IFR vis reductions appear likely, and will become more persistent at KBFD very late tonight into Friday. Outlook... Fri-Sat...MVFR CIGS and ocnl SHSN accompanied by IFR vsbys at KBFD/KJST. Mainly MVFR to low-end VFR cigs and VFR vsbys at KAOO, KUNV and KIPT. Sct-Bkn VFR Cigs and VFR vsbys expected to continue at KMDT and KLNS. Sun...Slight chance of light snow/reduced vis at night. Mon...No sig wx expected. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Gartner NEAR TERM...DeVoir/Gartner SHORT TERM...La Corte/Gartner LONG TERM...La Corte/RXR AVIATION...Lambert/Gartner
...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Friday) Issued at 208 PM CST Thu Dec 1 2016 A quiet weather pattern will persist through tonight and tomorrow with generally zonal H300 flow in place tonight, transitioning to more southwesterly flow tomorrow as a broad longwave trough moves into the western CONUS. Trended towards the ADJ/MOS guidance for lows tonight given the minimal changes in the air mass and last night`s lows. There is some uncertainty with regards to low temps in the south with both the NAM and RAP developing a patch of altostratus over SE KS that barely skirts the CWA. Weak northerly surface flow should keep highs tomrrow similar to today with increasing clouds late ahead of our weekend storm system. .LONG TERM...(Friday night through Thursday) Issued at 208 PM CST Thu Dec 1 2016 For the long term, we are continuing to deal with the evolution of the long wave upper trough over the central US, timing and impact of shortwave energy and the eventual first intrusion of arctic air into Kansas early next week. All operational models continue to spread moisture north across the southern plains northeast of an upper low over northern Mexico and breaking out precipitation by Friday afternoon south of Kansas. The moisture, weak lift and mainly light precipitation continues spreading north across eastern Kansas on Saturday. Meanwhile, a shortwave in the northern stream is forecast to cross the central plains Saturday night and Sunday morning shifting the moisture and precipition east of the area. The models have been somewhat consistent with this weak system over the past couple of days. Much of the precipitation should be rain, but there is a risk of a wintery mix especially early Saturday and Sunday mornings, but winter weather impacts are not expected. The models are in fair to poor agreement with the movement the northern Mexico upper low and the eventual arrival of the arctic air in northeast Kansas. We are confident that the upper low will be kicked out by shortwave energy moving south on the western side of the large upper trough early next week. As the upper low approaches, light rain is forecast to develop and it should remain liquid until the arrival of deep cold air behind the front. With respect to the arctic air, the models have been very inconsistent with the passage of the front. The 12Z GFS is now the most aggressive with the cold air which is totally different than yesterday. The new GFS has the cold air being drawn down behind the exiting upper low over the Missouri Valley Monday night while the old ECMWF and Canadian are much slower with boundary not drawing the cold air into the exiting upper low. The end result is low confidence with the timing of arrival of the cold air, but there is high confidence that it will arrive between Monday night and early Wednesday. After the deeper cold air moves in, the precipitation type should be snow. Given the high degree of uncertainty, will forecast low to moderate pops for light snow/rain in the extended from late Monday night through early Wednesday. At this point, there is no clear indication that the snow would be impactful or not given the low confidence in the various model solutions. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 459 PM CST Thu Dec 1 2016 VFR conditions are likely through the TAF period with light winds. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Skow LONG TERM...Johnson AVIATION...Barjenbruch