Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/07/20

Area Forecast Discussion
National Weather Service Denver/Boulder CO
810 PM MST Mon Jan 6 2020 .UPDATE... Issued at 806 PM MST Mon Jan 6 2020 Main concern tonight through Tuesday morning revolves around the high wind potential for the foothills. Current observations showing wind gusts mainly ranging in the 30-50 mph range with a few higher gusts around 60 mph. Radar imagery showing some enhancement of mountain wave across western Boulder county with highest winds remaining over higher elevations. Latest water vapor imagery and QG diagnostics indicate best subsidence will be after midnight tonight through mid morning on Tuesday and this will coincide with best shear profile for an amplified mountain wave. In addition, forecast soundings indicate strengthening stable layer at 750 mb through the night. Latest HRRR showing peak wind gusts between 08z-15z with max speeds of 60-70kt during this period. Will maintain the high wind warning through Tuesday morning. Elsewhere, winds have decreased over the plains but still some gusty winds up to 35 mph, mainly near the Wyoming border. UPDATE Issued at 451 PM MST Mon Jan 6 2020 Have issued a high wind warning for the Front Range foothills for tonight through Tuesday morning. Looks like another shot of high winds for the foothills tonight through Tuesday morning. Local wind programs are favoring high wind gusts up to 75 mph tonight. This event will be more of a chinook type wind as forecast soundings showing increasing stability at 750mb while cross sections showing cross barrier flow increasing to 50-60 this evening. The subsident flow will not be as strong as the past 2 nights but QG products still showing max subsidence at 12z on Tuesday in the light to moderate range. Shear profile also expected to improve this evening for an amplified mountain wave as the 100kt jet over us now will shift east of Colorado while nose of next jet segment noses into the Nebraska Panhandle by 12z Tuesday. High resolution models of HRRR/RAP showing potential of 60-70kt wind gusts through about 15z on Tuesday, with best potential for the damaging winds after midnight tonight. && .SHORT TERM...(This evening through Tuesday) Issued at 123 PM MST Mon Jan 6 2020 Strong winds continue across the northeast plains of CO this afternoon with moderate mid level subsidence over the northeast plains with peak gusts in the 50-60 mph range earlier today but those stronger gusts are becoming more localized. Will continue with the High Wind Warning this afternoon but see the stronger gusts start to gradually weaken the rest of the afternoon, as the upper trough continues to shift eastward. Highway cams not showing much in the way of impacts regarding snow and strong winds in the mountains so have cancelled the Winter Weather Advisory. Models still show some residual moisture in the high country overnight so will keep isolated to scattered snow showers mentioned on the higher northwest facing slopes, but dry elsewhere. In and near the foothills, strong and gusty downslope winds will continue overnight, with localized gusts in the 60-70 mph range possible. Since these stronger gusts should be more localized, no additional high wind highlights planned for the foothills tonight. Dry northwesterly flow can be expected through the day on Tuesday. It will remain windy in the mountains and foothills but the magnitude of the peak gusts will be less, around 50 mph. Over the northeast plains, breezy at times with temperatures back above normal, in the lower to mid 50s. .LONG TERM...(Tuesday night through Monday) Issued at 350 PM MST Mon Jan 6 2020 Upper ridging is over the forecast area Tuesday night. West- southwesterly flow aloft is in place Wednesday with an upper through to move into the CWA late day. The upper trough axis is just east of the CWA by 12Z Thursday morning. Southwesterly flow aloft comes after that with the next upper trough getting into the CWA by 12Z Friday morning. There is weak upward vertical velocity over the CWA Tuesday night. It gets a bit stronger on Wednesday. By late Wednesday evening, subsidence is over the forecast area. Upward motion returns later Thursday through Thursday night. The low level winds are a mix of normal diurnal trends and downsloping much of the time. Concerning high winds, there is a bit of a mountain wave set-up Tuesday night, but it is not significant. For moisture, it is sparse Tuesday into Wednesday. By Wednesday evening, it increases in the mountains. This continues Thursday, with some moisture getting into the plains later in the afternoon. There is fairly deep moisture in place over much of the CWA Thursday night into Friday morning. There is no measurable precipitation on the QPF fields until late Wednesday. There are some limited amounts over the plains areas Wednesday night through Thursday night. There is a tad over some of the plains Thursday night. No pops through Wednesday morning. Will go with "chance"s in the mountains Wednesday night into Thursday morning, then "likely"s Thursday afternoon and evening. For the plains willsgo with "slight chance"s Thursday night. No highlights. For temperatures, Wednesday`s highs are 1-3 C warmer than Tuesday`s readings. Thursday`s highs are 1-4 C cooler than Wednesday`s. For the later days, Friday through Monday, models have the upper trough pushing east of the CWA by Friday evening, with upper ridging moving in. By late Saturday, continuing into Monday an upper trough is over the CWA. It is unsettled, with mainly snow for the mountains through the weekend. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 806 PM MST Mon Jan 6 2020 VFR with some mountain wave cloudiness through Tuesday morning. Surface winds will be erratic through the morning given the mountain wave formation with strongest winds expected at BJC, especially after midnight. Could see some of the stronger winds spread out towards DIA later tonight/Tuesday morning but overall confidence is low to medium. Overall winds will decrease Tuesday afternoon and less winds then we had today. && .BOU WATCHES/WARNINGS/ADVISORIES... High Wind Warning until noon MST Tuesday for COZ035-036. && $$ UPDATE...Entrekin SHORT TERM....Coop LONG TERM.....Koop AVIATION...Entrekin
National Weather Service Hastings NE
522 PM CST Mon Jan 6 2020 .SHORT TERM...(This evening through Tuesday) Issued at 1229 PM CST Mon Jan 6 2020 Aloft: Animations of WV imagery and RAP tropopause analyses indicated modestly-amplified zonal flow over the CONUS. A wk shrtwv trof was over the Nrn/Cntrl Plns. As this trof heads into the TN Vly tonight...some amplification will occur in its wake in combination with a ridge building along the W coast. As a result...W flow will become NW over NEB/KS. Surface: 1024 mb high pres was over the OH Vly. A wk trof was moving thru NEB/KS associated with the feature aloft. This trof will move E along with its upr-lvl counterpart. High pres will emerge into TX and strengthen to 1030 mb. The influence of this high will extend N into NEB/KS. Rest of this afternoon: Sunny. Mild temps with highs in the 40s. W-NW winds will be gusty at times...espcly W of Hwy 281. Tonight: Mostly clr this evening...then incrsg mid-high clds after 06Z. Lows still above normal...mostly in the 20s. Tue: Partly-mostly cldy to start but becoming sunny. Highs svrl degs above normal with 40s over S-cntrl NEB and low 50s over N-cntrl KS. .LONG TERM...(Tuesday night through Monday) Issued at 249 PM CST Mon Jan 6 2020 Aloft: The ridge building along the W coast tonight will advance E and crest over the Plns Wed morning. A shrtwv trof will follow Thu morning. This trof will initiate a pattern change...with a longwv trof dvlpg and becoming locked-in over the Wrn USA. The flow over NEB/KS will remain from the SW thru Mon. A shrtwv trof is fcst to eject out of the mean Wrn trof Fri night...and there may be another 1 or 2 thereafter...but mdl disagreement within the broad Wrn trof lowers confidence on timing. Surface: A cold front was currently over Cntrl Can. This front will move S and E. It will move into NEB/KS late Tue and stall from NW-SE. Meanwhile...a cool front will move onshore in the W. This front will cross the Wrn USA and advance acrs NEB/KS Wed night. Low pres will form along this front and head acrs the GtLks. This will yank truly cold air S into the Cntrl Plns Fri...with strong high pres over the Nrn Plns. Return flow will dvlp Sat-Sun as that high moves into the Ern USA. It appears the next cold front could move thru next Mon. Temps: Continued milder than normal thru Thu...then turning colder beginning Fri. Fri-Sat will be colder than normal. Sun-Mon are uncertain...but probably will trend back to near normal. Cold Outlook: Believe this upcoming cold snap is just the beginning. Since mid Nov we`ve had it pretty easy in the temp department. Temps have averaged way above normal for the last 7 weeks...and temps typically swing back-and-forth on 30-60 day cycles. So we are due for a big downturn that it likely to last a while. All of the operational mdls and their ensemble means (EC/GFS/Bias-corrected GFS/CMC/JMA - Japanese Met Agency) are fcstg the PNA pattern turn strongly negative and remain negative for the foreseeable future. A -PNA pattern has a deep Wrn USA trof which favors colder temps here as the mean polar front becoming stalled just S and E of the CWA. Some of this cold will be Arctic in nature at times. Expect to eventually see a lot more daytime highs below frzg. Since this warm spell began...GRI has only seen 11 days with highs at or below frzg. Precip: Basically dry. There might be some snow shwrs or flurries around Fri. Snow: we need to watch Fri and Fri night for accumulating snow potential. There are a non-trivial number of EC and GFS ensemble members that indicate a lgt-mod snowfall could occur. Some operational EC runs have shown this potential over the last 3 days. However...there is no run-to-run consistency. It will all depend on how the upr trof evolves...whether it wraps up and strengthens...or it remains suppressed with the precip shield SE of the CWA. Even if that occurs...some members are still indicating a lgt snowfall with the Nrn stream part of the trof. Stay tuned. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Tuesday) Issued at 520 PM CST Mon Jan 6 2020 Quiet weather with VFR conditions are forecast for this TAF period. Main concern lies with LLWS, which looks to occur right off the bat. Have LLWS in through 07Z, with models in good agreement with the potential tapering off after that time. Otherwise, generally westerly winds are expected through the mid- morning hours tomorrow, before turning more northwesterly for the final few hours of this TAF. Speeds look to top out around 10-15 MPH. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ SHORT TERM...Kelley LONG TERM...Kelley AVIATION...ADP
National Weather Service Morristown TN
948 PM EST Mon Jan 6 2020 .UPDATE... EVENING UPDATE. && .DISCUSSION... Surface low pressure was strengthening over the MS/AL/TN border region this evening. Satellite imagery shows an expansive stratus shield spreading into eastern Tennessee over the last few hours, with further evidence of a strengthening system noted in an area of cooling cloud top temperatures on infrared imagery. Regional radar composites show some isolated to scattered returns showing up in northeast Mississippi, as well as northward into middle Tennessee. This matches up well with the latest HRRR and RAP model runs, both of which show precipitation filling in rapidly over the next 3-4 hours. There`s not much to change with the evening update, at least not anything that would represent a meaningful difference to the forecast. Models continue to indicate that showers will spread across the forecast area between midnight and roughly 6 am. Temperatures will be too warm to support any wintry precip reaching the ground initially, but as the system and associated cold front pass through around daybreak the column cools quickly and a changeover to a rain/snow mix will be possible on the back side of this disturbance in the northern areas. There remains a healthy amount of uncertainty with how this will play out though. By the time model soundings show a profile supportive of a wintry mix making it below 3000 ft in elevation or so, moisture levels aloft will be drying out rapidly, leading one to wonder how much wintry precipitation there will be at all outside of the mountains. Given the level of uncertainty, still think the best way to handle this for the time being is the SPS that the day shift issued. Overall the forecast is on track and will freshen up the SPS and zones shortly. CD && .PREV DISCUSSION... /ISSUED 646 PM EST Mon Jan 6 2020/ SHORT TERM...(Tonight and Tuesday)...Difficult forecast for tonight as a fast moving weak low pressure system tracks east-northeast across our area, bringing a quick shot of precipitation. Precip type should be all rain for much of the area, but northern areas and especially some of the higher terrain is a more difficult call. Ensemble guidance has been trending toward a much lower probability of significant snow, and a look at model soundings indicates that the warm air will not be pushed out until shortly before drying begins. Confidence is not high on snow totals for areas like SW VA and the central/northeast mountain peaks, but will show these areas mixing with and changing to snow with some light accumulations. Will issue an SPS highlighting this snow potential, but confidence is still too low to issue any advisory at this point. The precipitation will end fairly quickly with a mostly dry afternoon Tuesday as clouds decrease. Temperatures will still be near seasonal normals on Tuesday. LONG TERM...(Tuesday night through Monday)...No impactful weather is expected mid and late week, but periods of heavy rain will occur from the end of the week into the weekend with temps much above normal. The mid/upper trough across the eastern CONUS will lift out Tues night and Wed allowing heights to rise across the TN valley and southern Appalachians as surface high pressure slides into the deep South. Clearing skies and a relaxing pressure gradient Tues night will allow for the coldest night of the week with lows dipping into the upper 20`s/low 30`s. The low level flow gradually veering to southeasterly Wed as the surface high slides farther ESE combined with continued mostly clear skies will boost highs into the upper 40`s to near 50 across northeast TN, southwest VA, and the northern plateau with low/mid 50`s across the central and southern valley and southern plateau. Strong mid/upper longwave troughing digging into the Rockies Wed night and Thurs will amplify strong ridging over the eastern CONUS with the axis of the ridge shifting east with time. The surface high will shift offshore of the SE coast, so this pattern will cause strengthening deep layer southerly flow and WAA. Lows will stay in the low/mid 30`s in most areas Wed night warming into the mid/upper 50`s Thurs with a few 60 degree readings likely. As the western CONUS trough shifts farther east into the Plains Thurs night, surface low pressure will move across the upper Midwest and northern Great Lakes dragging a cold front toward the Mississippi and OH valleys. East coast ridging will hold strong, so this frontal boundary will become quasi-stationary across the Mississippi and OH valley regions Fri into Sat. Strengthening southwesterly H3 jet dynamics as energy emanates from the base of the trough will parallel this boundary Fri and Sat causing strong dynamic forcing and tremendous moisture transport to our west with PWATs exceeding the maximum daily values. This will set up a swath of heavy rainfall over those areas. The question remains how much rain will we eventually see in the southern Appalachians region as the upper trough and surface front finally shift through? Increasing isentropic upglide will generate expanding shower coverage late Thurs night through Fri, but this rain will be light. The heaviest rain will move in Fri night through early Sat night as cyclogenesis takes place in the Ark-La-Tx and tracks NE increasing the forcing across our region. WPC QPF across our region Thurs night through early Sun has trended much lower today with generally 1 to 2.25 inches west of I-75 and 0.50 to 1 inch farther north and east. This seems reasonable given that the GFS is starting to trend more toward the slower and stronger scenario that has been advertised by the ECMWF the past few days regarding the final shortwave that will eject from OK to the OH valley between Fri night and Sat night causing the aforementioned surface cyclogenesis and finally pushing the boundary east through our region. This negatively tiled shortwave should hang the boundary to the NW longer before rapidly swinging it through our region late Sat into early Sun causing the swath of heaviest rain (and possible convection given some CAPE) to be progressive in our area. Given the possibility for some convection and PWATs likely to exceed the maximum climatological value of 1.25 inches, we will continue a mention of localized flooding Fri night through Sat night in the HWO. Rain will quickly end from W to E Sat night as the cold front moves east and drier air filters in. Slight chance pops for a few showers will continue in NE areas through early Sun morning. Not much airmass change behind this system with highs in the upper 60`s to near 70 Fri and Sat only dropping to the low 60`s Sun. The next system moves in Sun night and Mon with slight chance pops Sun night expanding to chance to likely Mon. Temps will remain much above normal. && .AVIATION... 00Z TAF DISCUSSION. Potent incoming system will result in widespread MVFR flight categories tonight, with possible IFR conditions at KTRI as well. MVFR conditions and -RA will arrive at KCHA around 08z or so, KTYS by around 10z, and at KTRI by the 11z-12z time frame, lasting about 4-6 hours thereafter. A fairly quick return to VFR levels is forecast at all terminals tomorrow, with gusty west winds accompanying the clearing. Included some IFR conditions at KTRI around daybreak. Some -RASN could occur as the freezing level drops within 1,500 ft AGL, but confidence not high enough to include in the TAF at this time. Elsewhere only rain is expected. CD && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 41 53 32 56 36 / 70 10 0 0 0 Knoxville McGhee Tyson Airport, TN 38 49 32 52 32 / 90 70 0 0 0 Oak Ridge, TN 39 49 31 52 32 / 90 60 0 0 0 Tri Cities Airport, TN 34 43 29 47 30 / 80 90 0 0 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$