Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/08/20

Area Forecast Discussion
National Weather Service Duluth MN
911 PM CST Mon Dec 7 2020 .DISCUSSION...(This evening through Sunday) Issued at 342 PM CST Mon Dec 7 2020 Our quiet weather pattern continues with a warm up through the week and Wednesday looks like our next best shot at seeing some sun. We are still examining this coming weekend for our next shot at some snow and cooling temperatures. Light snow this morning has largely tapered off other than some brief lake effect snow showers along the North Shore of Lake Superior. The stratus deck in place at the moment will likely continue through this evening into tomorrow as the upper level shortwave over the region slides to the east. The strong inversion currently in place will also lend itself to areas of fog across much of eastern Minnesota tonight. Southwest flow will build tomorrow becoming gusty at times. This will begin to advect in both clearer skies and warmer temperatures. Wednesday should see mostly sunny skies and highs near 40, though daytime solar heating could push those temperatures up a couple more degrees. Cloudier skies look to come back by Thursday as northerly flow returns and temperatures respond accordingly with temperatures beginning to decrease. We are currently monitoring the possible track of a system that will move through the upper Midwest this weekend forced by a deep trough and associated jet stream in the upper levels. Due to the nature of the snow bands associated with this type of storm, a shift in the track by a hundred miles can make the difference between 10 inches and a trace of snow, so we are waiting until model ensembles come into better agreement before making snowfall accumulation predictions. However due to the northeast flow that will likely set up, we may be able to count on Lake Superior to ramp up lake effect snow production through the weekend for the South Shore of Lake Superior. We should also see a rapid temperature decrease as this system passes and we settle into more winter-like temperatures for at least a couple days. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 555 PM CST Mon Dec 7 2020 Widespread IFR/LIFR conditions covered most of the Northland this evening. We expect most areas will see the visibility drop tonight before some improvement late tonight into Tuesday morning. The RAP is depicting the low ceilings well this evening and forecasts clearing from west to east as 950-900MB winds veer and increase with a passing low level trough. It`s always a challenge determining if the models are too quick with the clearing and this is especially true at night and in the cold months. We followed the general trends of the RAP but didn`t clear as fast as it suggests. && .MARINE... Issued at 911 PM CST Mon Dec 7 2020 The pressure gradient will strengthen overnight into Tuesday as a frontal boundary and trough move across Lake Superior. Southwest winds will increase to 10 to 20 knots with gusts around 25 knots and perhaps a couple to 30 knots. The wind will be strongest and wave response highest along the Bayfield Peninsula and a portion of the North Shore, mainly north and east of Taconite Harbor. Expect the wind and waves to diminish Tuesday evening as they veer to west. Winds will become west to northwest later Wednesday and remain 15 knots or less into Thursday. && .PRELIMINARY POINT TEMPS/POPS... DLH 28 39 26 39 / 0 0 0 0 INL 26 38 24 38 / 0 0 0 0 BRD 27 41 28 42 / 0 0 0 0 HYR 27 40 24 42 / 0 0 0 0 ASX 29 41 28 42 / 0 10 0 0 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. LS...Small Craft Advisory from 6 AM Tuesday to midnight CST Tuesday night for LSZ121-140-146. Small Craft Advisory from 6 AM to 6 PM CST Tuesday for LSZ141- 147. && $$ DISCUSSION...Levens/PA AVIATION...Melde MARINE...Melde
Area Forecast Discussion
National Weather Service Grand Forks ND
918 PM CST Mon Dec 7 2020 .UPDATE... Issued at 916 PM CST Mon Dec 7 2020 With observations from Detroit Lakes to Fergus to Elbow Lake a half mile or less this last hour went ahead an issued a dense fog advisory through the overnight. Light winds will continue with a saturated airmass in place. UPDATE Issued at 545 PM CST Mon Dec 7 2020 Low cloud clearing is starting to get overrun by high clouds spreading southeast. Low clouds remain Roseau to just east of Mahnomen to just east of Fergus Falls. HRRR 925 mb RH maintains an eastward clearing overnight but this evening it may halt as winds sfc-925 mb remain very light until after midnight. Will monitor for any fog development and also temperatures. && .SHORT TERM...(This evening through Tuesday night) Issued at 338 PM CST Mon Dec 7 2020 Impacts this period limited to some fog redevelopment over west central Minnesota lakes country this evening. HRRR short term model handling the clearing of low clouds eastward well and used for sky cover trends thru this evening. Low clouds clearing from Roseau to Elbow Lake and it will clear gradually eastward reaching far eastern fcst area by 06z. 925 mb winds turning WSW and in the 20 kt range helping to bring in drier air from the west. Brief period where fog may reform in west central MN so included some patchy fog but not expected widespread or dense fog at this time due to the pickup in 925 mb winds allowing for a bit of mixing. West wind 5 to 10 kts tonight in E ND with warmer air moving esp at 925 mb and will expect to see the higher terrain west of the Red River valley remain near or a bit above freezing tonight, esp Walhalla area. Tuesday will see high clouds, thin some in the aftn. West wind 5 to 15 mph. Not a strong west wind, and some high clouds may affect temperature rise. Still though anticipating highs in the 40s with some low 50s psbl in parts of E ND. Fair Tuesday night. .LONG TERM...(Wednesday through Monday) Issued at 338 PM CST Mon Dec 7 2020 Highlights within in the later half of this week include continued seasonably warm temperatures Wednesday into Thursday. This is followed by a trend towards possibly seeing some accumulating precipitation Thursday into Friday, and possibly this weekend. Cooler temperatures closer to seasonal normal is also expected beyond Thursday. Large, anomalous ridging centers itself over the region Wednesday into Thursday continuing our recent warmth and dry conditions. Ridging breaks down as upper troughing develops into the western CONUS late in the work week. Some guidance hints at a leading shortwave trough Thu/Fri bringing the potential for some light precipitation. This is followed by a potential Colorado low-type system moving out of the Central Plains and into the Upper Midwest. Details like track and strength of this system, as well as its interaction with the leading wave still remains unclear. Variance in QPF within ensemble guidance is markedly large, making it difficult to make conclusions on the low/high end amounts, precipitation type, and location of heaviest precip. Regardless, most guidance does suggest in this overall pattern change with precip likely somewhere within the Northern Plains and Upper Midwest. But given the impact footprint Colorado lows typically bring to the aforementioned regions, monitoring the forecast would be prudent. With upper troughing expected late into the week, cooler temps are expected bringing conditions closer to seasonally normal, ie highs && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 545 PM CST Mon Dec 7 2020 Bemidji clearing timing is uncertain...thinking still around 06z/07z but at night clearing of low clouds is uncertain. Thief River Falls and west will see high clouds thru Tuesday. Light winds this evening then more westerly late tonight into Tuesday 5 to 15kts, though locally higher in NE ND Tues aftn. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...Dense Fog Advisory until 6 AM CST Tuesday for MNZ027-028-030-031- 040. $$ UPDATE...JK SHORT TERM...Riddle LONG TERM...CJ AVIATION...Riddle
Area Forecast Discussion
National Weather Service Paducah KY
955 PM CST Mon Dec 7 2020 .UPDATE... Issued at 955 PM CST Mon Dec 7 2020 Made some sky adjustments mainly to account for the progress of the clearing line according to the most recent satellite imagery. Still not sure if the clouds will surge southward through the whole area overnight, so delayed it a bit more. With prolonged clear skies and light winds, fog is going to be a concern overnight until and if the low clouds return. Used the NBM visibility grids as a guide as no other guidance is the least bit bullish on fog tonight. Managed to get some patchy fog in the grids as a first start, but it could become more widespread and pretty thick, if/where the low clouds don`t make it. UPDATE Issued at 656 PM CST Mon Dec 7 2020 We have reconsidered the cloud trends as discussed in the Aviation section earlier. With little flow in the low-levels, the slow eastward progression of the clearing line may continue at least through the evening. It looks to be making better progress over Kentucky. The Sky grids have been adjusted to this thinking through the evening, and then blend to the original mostly cloudy everywhere thinking by sunrise. Not completely sold on the clouds increasing from the north overnight, but have plenty of time to make further adjustments if necessary. The latest HRRR data was used for temperature and dewpoint trends through the night and into Tuesday morning, as they were the best match for our thoughts on sky trends. This results in temperatures holding nearly steady in the EVV Tri State through the night. Lows are now only expected to reach the middle 30s, while much of southeast Missouri and adjacent portions of southern Illinois and the Purchase area of Kentucky will likely drop into the mid to upper 20s with good radiational cooling expected. UPDATE Issued at 526 PM CST Mon Dec 7 2020 The AVIATION section has been updated for the 00Z TAF issuance. && .SHORT TERM...(Tonight through Wednesday night) Issued at 248 PM CST Mon Dec 7 2020 Rain-free conditions expected through mid week time frame. Much of the region along/east of the MS River has been plagued by cloud cover trapped beneath a low level temperature inversion today, keeping things on the chilly side even for early December. A weak and moisture starved upper mid level short wave will drop south within the steep northerly flow pattern tonight, bringing more in the way of cloud cover. This may help to hold temps up a bit, but most locations will still fall to between 25 and 30 by daybreak Tue. Hoping to break out into some sunshine during the day Tuesday as mid/upper level ridging begins to take place. Should help readings climb back close to normal during the afternoon. Will mark the start of a warming trend that will continue into mid week and beyond. .LONG TERM...(Thursday through Monday) Issued at 248 PM CST Mon Dec 7 2020 Our primary impact during the long term looks to be tied to a system moving through Friday into early Saturday. We remain dry on Thursday, as we await shortwave energy over the southwest U.S. that will lift northeast into the Great Lakes region through Saturday. At the surface, low pressure is expected to develop in the OK/KS vicinity Thursday night before migrating into the Great Lakes on Saturday. As it does so, a cold front will be pushed eastward across our area. Models are in decent agreement on the frontal passage occurring Friday night into Saturday morning. Our primary period of rain looks to begin in our western counties Friday afternoon and exit our eastern counties Saturday afternoon. 12z model runs continue to struggle to generate much in the way of instability, so have kept thunder mention out. However, wouldn`t be surprised if we eventually needed an isolated mention. QPF amounts at the moment look to average in the 0.75" to 1" range. Model solutions differ over the weekend with regards to a secondary wave lifting northeast across the TN/OH Valley regions. The Canadian and several GEFS ensemble members indicate this 2nd system occurring sometime in the Saturday night through Sunday period. However, there is not good agreement and a good chunk of models indicate dry conditions in the wake of the late week system. Went ahead and left in the NBM PoPs which generated a slight PoP across portions of the region Sunday into Sunday night given the uncertainty. Temperatures begin the period well above normal, with many areas reaching the 60s on Thursday and Friday. Sunshine will be plentiful on Thursday, but the increased southwesterly low level flow will help offset the lack of sun on Friday. Continued to side with readings above NBM numbers and closer to the 75th to 90th percentile given we tend to over perform in these types of situations. Cooler conditions return for the weekend into early next week, with highs only reaching the 40s again by Sunday and Monday. && .AVIATION... Issued at 526 PM CST Mon Dec 7 2020 The back edge of the low clouds has pushed just east of the MS River, but not sure how much further it is going to make it. Left the ceiling in at KPAH. Looking upstream, it should eventually spread back to the west over KCGI late this evening. It also looks like ceilings should trend lower (into MVFR) through the night, with KMVN, KCGI and KPAH seeing at least a few hours in the lower half of MVFR in the morning. With the final in a series of upper disturbances moving through tonight, some final clearing should spread eastward over most of the region through the afternoon. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$ UPDATE...DRS SHORT TERM...GM LONG TERM...SP AVIATION...DRS
National Weather Service Raleigh NC
935 PM EST Mon Dec 7 2020 .SYNOPSIS... A series of shortwave lows aloft will swing through the mid-Atlantic through Tuesday. High pressure will once again build into the area from the west through the middle of the week as the sub-tropical ridge builds through the Southeast US. && .NEAR TERM /THROUGH TONIGHT/... As of 935 PM Monday... Although some weak radar echoes remain across the eastern portions of the forecast area, no precipitation is being reported at automated stations as of 9pm. Have kept in the inherited slight chance of rain/snow across the Triangle through early morning that the HRRR was insistent on showing for several runs - although it has started trending away from that, and do not have any accumulation in the forecast anyway. Skies have been slow to start clearing, but as the upper level trough axis moves east, this should allow clouds to start clearing. Bridges may become a little icy overnight where roads remain wet and temps fall into the 20s. Lingering northwesterly winds behind the front may keep the atmosphere mixed enough in some places to only lower temps to the low 30s overnight, however sheltered areas should radiationally cool to the mid to upper 20s as skies clear behind the front. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... As of 330 PM Monday... One last upper-level trough will move from the OH Valley Tuesday morning across NC Tuesday afternoon, however the moisture and dynamics will be lacking and the weather will be dry for the day. Surface high pressure will build from the Mississippi Valley towards the central Appalachians, creating mostly clear skies, northwesterly surface flow and cold advection with highs limited to the mid to upper 40s in the afternoon. High clouds will be on the increase Tuesday night, however lows should still radiationally cool into the mid to upper 20s. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... As of 305 PM Monday... Surface high pressure initially centered over the Gulf of Mexico will shift east to the western Atlantic from Wednesday through Friday. Aloft, an upper trough will then give way to height rises and an upper ridge over the Eastern US by late week, pumped up by the next deep trough that will be moving across the central US. This pattern will result in mostly sunny skies and dry conditions for central NC through Friday, along with warming temperatures through the week. Forecast highs are in the lower-to-mid-50s on Wednesday and upper-50s to mid-60s (5-10 degrees above normal) on Thursday and Friday. Lows in the 30s are expected on Wednesday and Thursday nights. Clouds will be on the increase Friday night, with lows in the 40s. Both the GFS and ECMWF are in good agreement that a deep upper trough and associated cold front will then approach from the west on Saturday, with surface low pressure moving NE into the Great Lakes region. A coastal front will also be moving inland into central NC Friday night and Saturday. Thus it appears the area may be in a relative dry slot on Saturday, with the best chance for showers in far western zones (from the approaching upper trough) and far eastern zones (from the coastal front), where the forecast has slight chance POPs. The best chance for showers across the entire region looks to be Saturday night into early Sunday. QPF looks light at this time, around a tenth to a quarter inch at most, but that could change. While the operational runs of the 12z GFS and ECMWF continue to quickly bring through the cold front and end precipitation chances by Sunday afternoon, most GFS ensembles are much slower with the front, keeping precipitation across the area into Monday. Thus continue slight chance POPs Sunday night into Monday. Southerly flow ahead of the cold front will result in mild temperatures with highs in the 60s on Saturday, before it starts to cool down to near normal by Sunday night and Monday, depending on the exact timing of the cold frontal passage. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... As of 705 PM Monday... 24 hour TAF period: Precipitation has ended at INT/GSO. A line of sprinkles/flurries is moving through RWI/FAY, while another small area of precipitation may redevelop during the late evening in the vicinity of RDU. GSO/INT are already VFR, the remaining sites should see lifting ceilings by midnight and VFR conditions for the rest of the TAF period. Northwest winds will be gusty at INT briefly this evening, then some wind gusts up to 20 kt will be possible at INT/GSO/RDU Tuesday afternoon. Looking ahead: VFR conditions will prevail through end of the week. The next disturbance will move across the region this weekend. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...KC/JJT NEAR TERM...Green/JJT SHORT TERM...JJT LONG TERM...Danco AVIATION...Green/JJT