Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/30/17

Area Forecast Discussion
National Weather Service Denver/Boulder CO
826 PM MST Fri Dec 29 2017 .UPDATE... Issued at 806 PM MST Fri Dec 29 2017 Surface cold front has sludged through much of northeast Colorado this evening with a brisk east to northeast winds over the area. With the shallow upslope in place, GOES16 night imagery showing stratus deck rapidly developing from Denver northward to the Wyoming border. Expect the low clouds to envelope much of the plains. High resolution models are not doing well with this low cloud development except the NAMNest which seems to have the most accurate depiction as it evolves this evening. Will be making some adjustments in cloud cover and fog development based on evening trends. Even more complicated is how much clearing and scouring out of the cloud deck happens later tonight and Saturday morning. Models are quite varied on this but for now going to lean on the later morning clearing based on latest HRRR as areas Denver northward not going to see much downslope flow developing until later morning. Still expect strong and gusty west winds but mainly confined to mountain passes and higher exposed east slopes. Winds this evening have been in the 30-45 mph range and this should hold through much of the night and then some increase Saturday morning. Not expecting high winds as lack of stability and increasing shear will not allow deep wave amplification. && .SHORT TERM...(This evening through Saturday) Issued at 300 PM MST Fri Dec 29 2017 Most wind in the higher terrain have slowed in speeds, with the exception of Berthoud Pass and areas around Georgetown where gusts of 65 to 80 mph still occur. With the exception of Berthoud Pass weather station at almost 12500 feet, expect all other areas to be below warning criteria within the next hour, so an expiration of 3pm will be fine. Winds will remain elevated along the east slopes of the Front Range mountains and foothills through the night, with gusts of 30 to 50 mph still possible. This will keep temperatures moderated in these areas, with minimums likely to the 25 to 35 degree range. An arctic airmass is pushing southwest over the northeastern plains currently, with temperatures falling quickly into the teens to 20s. Areas of stratus and fog will follow later this evening. At this time, the arctic push is expected to push through the northern urban corridor down to around Broomfield then out to Denver International Airport arcing around into Lincoln County initially. Then a surface trough will build in and the airmass will likely retreat slightly east. There is a very slight chance to see some light freezing drizzle or flurries over the far northeastern corner according to forecast soundings, but the lower levels aren`t as wet as Id want, so did not add this to the forecast at this time. Minimum temperatures in this arctic airmass will be in the teens to single digits, and even below zero over the far northeast corner. Tomorrow, flow aloft turns slightly more westerly to bring warmer temperatures at 700 mb. However, with the cold airmass over the most of plains, temperatures will likely be similar or maybe a few degrees cooler than today`s readings along the southern urban corridor where the arctic airmass will either have very little lag time to none. Further north and east, temperatures will be much colder as the airmass will be slow to scour out, if at all. Late in the afternoon, a jet max will approach to bring a slight chance of snow to the far northern mountains. .LONG TERM...(Saturday night through Friday) Issued at 300 PM MST Fri Dec 29 2017 Northwest flow continues over the state with an upper ridge in place over the western coast. By Saturday night the shallow stratus deck will be in place over the plains. Persistent cold temperatures and cloud cover will continue through Sunday. Mountains will see light snow through the afternoon on Sunday with just a few inches in accumulation possible. For the plains upper air soundings show a mostly dry profile but with enough ice nucleation to bring light snow by Sunday afternoon with flurries possible into Sunday night. A drier airmass will move in for the mid to upper levels with the column will remain cold enough for the formation of flurries on the plains into Monday morning. Temperatures on Sunday will stay below normal with highs in the 20s. For Sunday night into Monday temperatures will dip into the single digits and well below zero on the eastern plains. These temperatures combined with winds from 5 to 10 mph will create wind chill readings of -22 to -28 degrees. These conditions could cause frostbite for individuals that are outside and uncovered in less than 10 minutes. Clouds and cool temperatures will persist through the day Monday with some light flurries possible over the plains. Highs will stay in the 20s with overnight lows continuing to be in the low single digits. Tuesday will see a slight pattern shift as the upper ridge moves further into the Great Basin and a trough drops out of the north. This dry feature will not produce much precipitation and will seeing greatly increasing subsidence behind it helping to increase temperatures back to normal. NW flow will return on Wednesday with weak moisture in the Northern mountains helping to bring a slight chance of snow to the higher elevations Wednesday into Thursday. A cold front on Thursday could help to increase chances of snow over the urban corridor but will have to see how models resolve these features. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 806 PM MST Fri Dec 29 2017 With early evening frontal passage winds have shifted northeast at KDEN and more north and northeast at BJC/APA. Stratus deck has been rapidly developing and just into KDEN and will soon be in BJC and APA. Confidence is on the lower side on fog development(how dense?) and stratus dissipation Saturday morning. For now will lean on the later clearing at DEN with lack of downslope component until Saturday afternoon. Will have some temporary conditions of 1/4 FZFG at Denver but overall confidence is low to medium. && .FIRE WEATHER... Issued at 300 PM MST Fri Dec 29 2017 In terms of weather conditions, there is concern tomorrow for South Park, the southern foothills and onto the Palmer Divide, zones 214, 216 and 241. Humidity will be in the low teens with gusty west winds of 25 to 40 mph. However, in terms of fuels conditions, South Park looks to have good enough snow cover via webcams. As for southern foothills and Palmer Divide and looking at fire indices, only one RAWS station is at a Very High rating, where the rest are at Moderate and Low ratings. Therefore, decided not to issue a Red Flag Warning for those zones. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Entrekin SHORT TERM...Kriederman LONG TERM...Bowen AVIATION...Entrekin FIRE WEATHER...Kriederman
Area Forecast Discussion
National Weather Service Burlington VT
917 PM EST Fri Dec 29 2017 .SYNOPSIS... Below normal temperatures will continue through this weekend and into much of next week. Winds will not be as strong as the past couple of days and as a result wind chills will not be a concern. However, there will be two periods of gusty northwest winds and very cold temperatures, this Sunday and Monday and again for the middle part of next week, that will result in wind chill issues. && .NEAR TERM /THROUGH SATURDAY NIGHT/... As of 908 PM EST Friday...1027mb sfc high pres over SLV/Western Dacks has resulted in clear skies and light winds...with temperatures quickly reaching expected low temps already. Have updated to adjust temps down by 2 to 4 degrees...along with parts of central/southern VT...where Rutland is already at -9F. Meanwhile...both Ogdensburg and Edwards are near -20f with slk at -10f. Expect as clouds increase after 04z...temps will level off and slowly rise after midnight across slv/western dacks. Difficult to adjust some areas which are experiencing rapidly falling temps...while clouds/winds prevail over northern VT and parts of the eastern cpv near BTV holding temps btwn 0f and -5f. Bottom line most locations between -10f and -20f with some slightly lower and higher values possible. Very light snow/flurries continue near BTV and MPV...from lake effect moisture/instability...but latest RAP 13 and BTV 4km soundings show low level moisture decreasing btwn 04z-06z tonight. Have continued to mention chc pops for light snow thru 04z...then tapered off. Only a dusting of new snow is expected. Previous discussion below: Light snow will be ending this evening as upper level shortwave pushes East of the north country. Skies will gradually clear. Overnight lows will range from the negative single digits to negative twenties. Clouds will increase across the region on Saturday with another upper low crossing our Northern zones. Better shortwave energy will stay south of our forecast area, but do have a chance of light snow mentioned in the forecast. Maximum temperatures Saturday will range from the single digits to teens above zero. Clouds remain in place Saturday night though light snow should be ending. Overnight min temps will range from the single digits below zero in the Champlain valley to teens below zero. MPV has a shot at breaking min temp records tonight and tomorrow night, and MSS may reach the min temp record tomorrow night. && .SHORT TERM /SUNDAY THROUGH MONDAY/... As of 321 PM EST Friday...Northwesterly flow will commence once again Saturday night into Sunday, bringing yet another shot of cold air into the North Country to end 2017. As the upper-level shortwave departs to the east, expect some peaks of sunshine Sunday. The sun will be deceiving however, as daytime high temperatures will cap in the low single digits in valley locations and remain below zero elsewhere. In addition to the increasingly colder air, expect some higher momentum northwesterly winds to mix down to the surface Sunday through Monday. This will create some wind chill concerns as even fairly light winds in temperatures this cold can create bitter wind chills. Decreasing cloud cover will allow temperatures to drop down to the negative teens Sunday night (New Years Eve). Those with outdoors New Years Eve/New Years Day plans should be prepared for bitter cold and plan in advance to wear many layers and take precautions against frostbite. Monday (New Years Day) will bring similar temperatures to Sunday, if not a few degrees colder. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... As of 321 PM EST Friday...Tuesday and Wednesday will feature a brief respite from the widespread below zero temperatures, although temperatures will still be around ten degrees below seasonal norms. The better chances for some snow return Thursday, followed by another surge of arctic air that will bring a return of the bitterly cold temperatures by the end of next week. Details...A fairly potent shortwave over western Canada will dive down to the Mississippi River Valley Wednesday, amplifying and sharpening the broader longwave trough over the eastern US. Ahead of the wave, a weak southwesterly low-level jet will transport some warmer air northward to New England. This will allow for a slight warming trend Tuesday and Wednesday with daytime high temperatures climbing a few degrees each day. By Wednesday, high temperatures will be in the teens above zero, which will feel quite warm compared to the recent frigid spell. Some light snow showers are possible Tuesday and Wednesday as weak disturbances rotate through the flow, however moisture is very limited and any accumulations will be minimal. By Wednesday evening, the forecast becomes more complex and uncertain. The sharpened trough will take on a slight negative tilt as it moves over the Eastern Seaboard. At the same time, southern stream energy will rotate northeastward out of Florida. There is some potential for the two systems to phase and spin up a coastal low Thursday, however recent model runs are trending away from this solution. Current thinking is that the southern shortwave will generate a surface low pressure system, however the low will stay too far east in the Atlantic to be of much impact to the North Country. If the coastal low does indeed miss us completely, we will still see some chances for precipitation Thursday as a weak clipper moves through from the west. Once the trough axis moves off the coast Thursday night, we`ll see yet another push of cold air into New England and temperatures will return to 20 to 30 degrees below normal by Friday. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... Through 00Z Sunday...VFR conditions with local MVFR at BTV and RUT will prevail through much of the overnight hours. Light snow and ceilings around 2500 ft will persist at BTV and RUT through approximately 05z, then expect all sites will be VFR through 15Z Saturday. Another round of light snow will bring the threat of MVFR conditions, particularly to SLK and RUT, from 16z Saturday on. Winds will be light and variable much of the period. Outlook... Saturday Night: Mainly VFR, with local MVFR possible. Chance SHSN. Sunday: VFR. NO SIG WX. Sunday Night: VFR. NO SIG WX. New Years Day: VFR. NO SIG WX. Monday Night: Mainly VFR, with local IFR possible. NO SIG WX. Tuesday: Mainly MVFR, with local IFR possible. Chance SHSN. Tuesday Night: Mainly MVFR, with local VFR possible. Chance SHSN. Wednesday: Mainly VFR, with areas MVFR possible. Chance SHSN. && .EQUIPMENT... The KTYX (Montague NY) radar will be out of service into the weekend and possibly early next week as a motor and power supply have failed. Parts are on order and are scheduled to arrive tomorrow. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Evenson NEAR TERM...Neiles/Taber SHORT TERM...RSD LONG TERM...RSD AVIATION...Hastings EQUIPMENT...WFO BTV
Area Forecast Discussion
National Weather Service State College PA
1014 PM EST Fri Dec 29 2017 .SYNOPSIS... Multiple arctic intrusions will ensure well below normal temperatures continue into the first week of 2018. A quick- hitting, fluffy snowfall is expected tonight into Saturday, followed by occasional intrusions of lake effect snow. && .NEAR TERM /THROUGH SATURDAY/... The anemic clipper is working its way across eastern Ohio and western Pennsylvania. Best IR enhancements are in Ohio and West Virginia at 0300 UTC. Some of the coldest tops since the wave was in IL/IN. The HRRR and RAP continue to produce about 0.10 inches of QPF across most of the southern 2/3 of our forecast area. Some spots in 0.20 in the southwest mountains and a few location mainly in south-central areas. This event will probably support 16 to 20 to ratios. So light fluffy snow spreading west to east overnight. Most locations should see 1 to 2 inches of fluff by about midday. RAP/HRRR would imply snow around midnight in Somerset county reaching the Harrisburg/York areas in the 6 AM range. With the clipper the higher QPF is in the southwest mountains in the 0.2 to 0.3 range. Most other areas are in the general 0.1 range. So advisories with clipper are for 3-5 or so in the southwest mountains and around 2 inches or so in the southern tier counties. Similar snow expected in central areas but advisory requires 3 inches of snow. In the northwest a longer lasting LES event will bring snow over a longer period of time. Roads in the southeast probably will be snow covered by 7-8 AM for Saturday commute which is pretty low and shoppers. Snow tapers off outside LES and upslope areas pretty fast. One hour snow in the HRRR and RAP is pretty much over outside of Lancaster County and the Laurels. And of course there is LES issues in Warren county. && .SHORT TERM /SATURDAY NIGHT/... LES continues in NW PA. Cold/arctic air poised to move in and overnight lows below 0F likely along our northern tier. Mainly single digits central areas. Possible some isolated 0F reading with the fresh snow SW mountains. Southeastern areas too will get in on the cold act with lows mainly in the lower teens. Rural areas that catch 2 inches of snow could dip below 10F! There may be a windchill advisory issue by Sunday morning and on into Sunday. But not at this time as we have a WSW up so it can wait. && .LONG TERM /SUNDAY THROUGH FRIDAY/... As the ridge build over the western United states an amplified trough will continue to deepen. this elongated trough will extend westward. this will maintain the unseasonable cold temperatures which at times will be subzero, with dangerously low wind chill values during periods of strong persistent wind gradient over the region. Persistent lake effect and orographic snow showers are expected to continue next week. The ensemble mean and deterministic models are in fair agreement on the position of a low over Hudson Ba and a deepening trough bring another weather system through the region mid to late week. The best moisture remains off shore but a clipper type system could bring another period of snow showers through the later half of next week. High temperature departures on Sunday will range from 20 to 30 degrees below normal. Lows Sunday night will be in the negative and positive single digits with -5F to -20F wind chills into Monday morning. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... For 00Z TAF package, some minor changes, but mainly just more groups added after 18Z Saturday. System to the west of PA will quickly bring light snow to the area late tonight into Saturday afternoon. VFR conditions will give way to MVFR and IFR conditions later tonight. As the system pulls east of the area Saturday afternoon, winds will shift to the west and become gusty. While eastern areas will clear out across the east later Saturday afternoon, cold air aloft and winds aloft from the northwest, will result in some snow showers across the mountains, mainly at BFD and JST. Sites like AOO and UNV may see some, but most likely after 00Z Sunday, as wind shift line aloft shifts eastward. Outlook... Sun...Scattered snow showers and areas of reduced cigs and vsbys, mainly across the northern and western mountains of PA. Mon-Tue...VFR most of the area, but chance of snow showers across the northwest. Wed...No sig wx. && .CTP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 6 PM EST Saturday for PAZ004-005. Winter Weather Advisory from 3 AM to 1 PM EST Saturday for PAZ010-017-024-033>036-056-057-059-063>066. && $$ SYNOPSIS...RXR NEAR TERM...Grumm SHORT TERM...Grumm LONG TERM...Ceru/Steinbugl AVIATION...Martin
Area Forecast Discussion
National Weather Service Grand Forks ND
923 PM CST Fri Dec 29 2017 .UPDATE... Issued at 921 PM CST Fri Dec 29 2017 Minor adjustments made to ambient and apparent temperatures...wind chill warning criteria being met across portions of northeastern North Dakota and will increase in coverage over next several hours. Reduced sky cover across the region. Re-issued WSW to remove advisory wording from earlier in the day. UPDATE Issued at 640 PM CST Fri Dec 29 2017 Solid wind chill advisory criteria across the CWA as temperatures begin to plummet toward wind chill warning criteria, which should be met for most of the area by late evening. Already seeing temperatures across the north in the 15 to 20 below range...with 12 mph winds. Have made minor adjustments to next three hours of temps with no change to MinT well as updating winds with latest RAP guidance and re-calculating Apparent Ts. Light snow over FAR at beginning of shift is to the south now and should end within the next hour. && .SHORT TERM...(This evening through Saturday) Issued at 309 PM CST Fri Dec 29 2017 Main concern in the short term is dangerous wind chill values developing overnight and into Saturday, persisting through the weekend. Wind Chill Warning is in effect for tonight through Monday morning. While this is not an unusual airmass for the Northern Plains, this stretch and magnitude of extreme cold is more typical of the mid January to February timeframe and has not occurred for the past few years. Aided by persistent northwest flow aloft, a dry, frigid Arctic airmass and strong high pressure build into the Dakotas and Montana tonight. This airmass remains entrenched in the area through the weekend. Saturday looks to be the coldest day of the stretch, as a strong jet streak digs the upper level trough over the Great Lakes. Despite increased sunshine on Saturday, diurnal heating is weak this time of year and the atmospheric pattern will very much inhibit warming, allowing for highs to only reach the teens below zero. .LONG TERM...(Saturday night through Friday) Issued at 309 PM CST Fri Dec 29 2017 Upper level northwesterly flow is expected to continue through the extended forecast period. With a strong blocking high pressure ridge over the western CONUS, only weak shortwave troughs are likely to impact the region. These will bring quick surges of colder, arctic air and light precipitation chances. Model guidance agrees on the overall pattern, but differences in timing and surface low track brings low confidence to any precipitation chances over the extended outlook. Surface ridging is expected over the Dakotas and Montana Saturday night into Sunday. This will push colder arctic air southward into the region. Morning lows in the -25 to -30 range are expected for Sunday morning with dangerous wind chill values from -40 to -50. Sunday afternoon highs from -10 to -15 are likely, dropping to overnight lows near the -20 mark. Dangerous wind chills will continue through Monday morning until temperatures begin to climb near the zero mark across the region. A gradual warming trend is expected mid week as winds turn more southwesterly and advect in warmer air. An upper level shortwave on Tuesday will bring a cold front through the region, dropping temperatures back down below zero and bringing light snow chances to northwest Minnesota. After a cooler Wednesday, temperatures will likely rebound again for Thursday into the single digits as winds turn more southerly ahead of another clipper low dropping out of Canada. This shortwave will bring light snow chances to the region, though model guidance disagreement gives low confidence in the placement and timing of any precipitation. Regardless, overall impacts are expected to be low at this time with the more impactful weather coming over the New Year`s weekend with the dangerously cold temperatures. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 640 PM CST Fri Dec 29 2017 VFR. Extreme cold will have impacts on starting small aircraft throughout the weekend, pre-heating engines will be necessary. Removing aircraft from heated hangars will result in some immediate light frost developing on skin. General aviators should treat wind chill warning this weekend the same as if traveling by ground transportation, with appropriate emergency gear available in case of an emergency. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...Wind Chill Warning until 9 AM CST Monday for NDZ006>008-014>016- 024-026>030-038-039-049-052>054. MN...Wind Chill Warning until 9 AM CST Monday for MNZ001>009-013>017- 022>024-027>032-040. && $$ UPDATE...Speicher SHORT TERM...BP LONG TERM...AM AVIATION...Speicher
National Weather Service Jackson KY
1010 PM EST Fri Dec 29 2017 .UPDATE... Issued at 1010 PM EST FRI DEC 29 2017 Have updated the forecast based on radar trends and latest near term model guidance - particularly from the HRRR and NAM12. Accordingly, have backed off on the snow showers and flurries through the rest of the night. Have also updated the temperatures with the latest blended model data and current obs/trends. The updated grids have been sent to the NDFD and web servers. A fresh set of zones and updated HWO have also been issued. UPDATE Issued at 700 PM EST FRI DEC 29 2017 23z sfc analysis shows relatively weak low pressure throughout the area with a mid level shortwave crossing the Ohio Valley along with some limited moisture this evening. This has already brought a band of snow to locations generally along and north of Interstate 64. With a fleeting shot at whitening the roads in the far north - pavement temperatures in the low 30s - did issue a briefs SPS tracking the healthier parts of this snow band. Additional light snow showers will be possible through the night, but mainly confined to just flurries. Temperatures currently are sub freezing for most of the area - generally in the mid to upper 20s. Dewpoints, meanwhile vary from the low 20s north, with the snow, to the mid teens elsewhere as the winds are generally light and variable. Updated the grids to adjust the PoPs and Wx forecast with this initial snow band and in its wake - per radar trends and latest HRRR guidance. Also tweaked the near term T and Td grids to incorporate the latest obs and trends. These have been sent to the NDFD and web servers. && .SHORT TERM...(This evening through Saturday night) Issued at 345 PM EST FRI DEC 29 2017 An upper level shortwave is currently passing through the northern extent of the Great Lakes this afternoon, exiting overnight. At the surface, this will translate to a low pressure system which will be located over the Lower Great Lakes. This low pressure system is expected to remain nearly stationary through tomorrow (Saturday) afternoon before finally shifting eastward. A cold front is trailing southeast of this low, currently located just along and north of the Ohio River and through the state of Ohio. This front will shift southeast into our region this evening and overnight, where it will become stationary through Saturday morning. It will lose considerable strength at this point, with the majority of the precip still forecast to remain closer to the parent low and northern extent of the cold front. Forecast models are all in good agreement that there will be a sharp cutoff line of QPF across north KY, with most of the QPF being centered over Ohio. The question is how much of this QPF will actually make it into our northern counties. While models are in good agreement, any slight shift north or south could result in our northern counties seeing an inch or more or snow, or no snow at all. As it is now, tried to match up with neighboring offices to our north, as well as latest hi-res and long range model guidance for QPF. If anything, models are trending down across our region, which would result in no snow, so ended up hand drawing some low end amounts which equated to between a dusting and 0.7 inches of snow (highest amounts closest to ILN and RLX borders). This is still a bit lower than the previous forecast. Evening shift will continue to monitor as the snow moves into the region in case any updates in these amounts need to be made, including any issuances for an SPS or greater headlines. Given low confidence and impacts, only included mention in HWO at this time. Lingering snow and snow flurries will be possible into the day tomorrow, shifting to far eastern KY before exiting as the cold front shifts southeast of the region. An upper level low will traverse the Great Lakes during the day tomorrow, resulting in lowering heights across the region and strengthening NW flow, pulling much colder air from Canada into the Ohio Valley. Meanwhile, at the surface, a strong area of high pressure will move southeast from Canada and into the Dakotas. Its expanse will be very broad, encompassing much of the Ohio Valley and Kentucky behind the exiting cold front Saturday afternoon. Winds will become more northerly across KY on the front edge of this high pressure system, combining with the ongoing NW flow to pull more arctic air into the region. As such, expect temps to start bottoming out once again as we head into Saturday night, with lows expected to be in the single digits to low teens across the CWA despite some lingering cloud cover across the region. .LONG TERM...(Sunday through Friday) Issued at 411 PM EST FRI DEC 29 2017 Expansive high pressure that originated in Canada will continue to slowly shift southward, with its influence eventually spanning much of the central and eastern Conus throughout the course of the extended period. Generally northern flow will be in place across Kentucky during this time, as we will be placed on its SE fringes. Meanwhile, aloft, a digging trough will be in place across the Great Lakes and Ohio Valley, slowly shifting eastward throughout the extended, with nearly meridional flow in place at times. This will result in a strong pull of arctic air straight southward into the state and some of the coldest temperatures we have seen since last January. Unfortunately it appears as though the coldest temperatures will also coincide with the New Years holiday. Lows New Years Eve into New Years morning will be in the single digits, with lows the following night possibly even a few degrees colder. Highs most days during the extended will be in the teens and low 20s. By Wednesday of next week, a surface low will develop behind the high pressure system, shifting southeast under the continued influence of NW flow aloft. This will result in a developing cold front which will also shift southeast and move into the Ohio Valley, traversing KY Wednesday night. While ultimately this system will weaken in the face of such a strong area of high pressure, with no weather impacts other than some passing clouds across the region, it will result in more Srly flow and warmer temps in the upper 20s and low 30s during the day Wednesday. NW flow behind the passing system will then quickly bottom out temperatures once again Wednesday night back into the single digits and low teens. The cold snap and arctic airmass will then continue into the remainder of the extended forecast and even after. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) ISSUED AT 725 PM EST FRI DEC 29 2017 High clouds will remain in place across the region through the night, stemming from a weather system located to our north. Light snow will be possible on our northern and eastern fringes from this through the night. Look for some slight chances of light snow for the rest of the area during the day Saturday as a cold front presses through eastern Kentucky. Have included some VCSH for this in the TAFs but expect only very brief and limited vis restrictions. MVFR cigs, though, are expected to move in on Saturday along with and ahead of that front and remain in place until near the end of the TAF period for most spots. Winds will generally be light and variable, under 5 knots into Saturday morning before switching to the west and northwest at up to 10 kts by mid afternoon following FROPA. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...JMW LONG TERM...JMW AVIATION...JMW
Area Forecast Discussion
National Weather Service Lake Charles LA
1000 PM CST Fri Dec 29 2017 .DISCUSSION... Latest high res runs indicate a gradual increase in light shower activity later tonight as WAA develops on increasing srly flow ahead of coastal trof along the TX coast...however local 00z sounding showed a fair amount of low-level dry air, at least in relation to recent moisture trends. In the end, have elected to go against the HRRR and stay with inherited slim POPs only for parts of sern TX. Elsewhere, inherited grids/zones look in good shape as well based on latest obs/trends...thus no update is planned for this evening. 25 && .PREV DISCUSSION... /issued 603 PM CST Fri Dec 29 2017/ DISCUSSION... For 00z TAF issuance. AVIATION... VFR conditions have persisted this afternoon and are forecast to continue through this evening as the cloud deck builds in from the west. CIGS are progged to gradually lower to MVFR overnight into Saturday in response to increasing low-level moisture. Winds will be light and variable overnight, becoming easterly tomorrow. Saturday, areas of drizzle will overspread the area from west to east beginning around sunrise as a weak trough of low pressure moves over the Texas coast and stalls over the area. Hires guidance indicates fog development as early as tomorrow afternoon, so expect visibilities reduced to IFR at all sites beginning in the afternoon hours and continuing through the evening. RACKLEY PREV DISCUSSION... /issued 341 PM CST Fri Dec 29 2017/ DISCUSSION... A ridge of high pressure continues to be located to our north, while a cold front is across the central Plains states, and a frontal boundary is across the southern Gulf of Mexico. A weak wave or trough of low pressure is trying to develop off the south Texas coast, and it will move up the Texas coast tonight, eventually bringing scattered rain showers into southeast Texas after midnight tonight or tomorrow morning. This system will stall out over our coast, keeping rain chances in the forecast Saturday and Saturday night, before a strong high pressure system starts to move south out of the northern Plains, and pushes it back further out in the Gulf. So the rain ends Sunday, before the freezing temperatures kick in late Sunday night into Monday morning. Expect to see a hard freeze Monday through Thursday mornings across much of the forecast area, thanks to the strong high pressure system parking over the central US. With these cold temperatures, expect to see hard freeze warnings, and likely wind chill advisories as well. The cold air will affect the coastal waters as well, where gale conditions are possible by Sunday night into Monday. In addition, with such strong northerly flow, a low water advisory may be required for the Sabine-Neches and Calcasieu ship channels during periods of low tides. Erickson && .PRELIMINARY POINT TEMPS/POPS... AEX 40 53 39 41 / 10 30 40 30 LCH 46 58 47 52 / 10 50 40 30 LFT 44 56 47 50 / 10 50 40 40 BPT 48 60 49 53 / 20 50 40 30 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...None. TX...None. GM...None. && $$
Area Forecast Discussion
National Weather Service Norman OK
959 PM CST Fri Dec 29 2017 .UPDATE... Lowered forecast low temperatures slightly, and quickened cooling in the hourly temperature grids. && .DISCUSSION... The cold front has arrived into northwestern Oklahoma. Temperatures have dropped quickly down to 24-25 degrees in Garfield, Major and Alfalfa Counties where winds are relatively light. These temperatures may rise a bit again as northerly winds increase and mix slightly warmer temperatures to the surface (as occurred farther northwest at Buffalo and May Ranch mesonets), but that will only be temporary as cold advection will continue overnight. Have quickened the pace of cooling with the frontal passage by trending hourly temperature grids toward the HRRR forecast. Overall, this adjustment lowers the forecast min temperature slightly in general. Of note, the forecast low temperature grids are technically valid for the low temperature through 15Z (or 9 AM CST). Some areas may actually reach slightly lower temperatures just after 9 AM on Saturday morning. && .PREV DISCUSSION... /issued 555 PM CST Fri Dec 29 2017/ DISCUSSION... AVIATION... VFR ceilings in northwestern Oklahoma and MVFR ceilings in central and southern OKlahoma will likely lower to IFR later tonight after the arrival of a cold front and shift to north winds. Fog is expected in southwestern Oklahoma and adjacent parts of northern Texas. Light freezing drizzle is expected at times Saturday morning. Any freezing drizzle, fog, and low cloud conditions will clear from the north on Saturday afternoon across the northern part of Oklahoma. PREV DISCUSSION... /issued 342 PM CST Fri Dec 29 2017/ DISCUSSION... Overall not a lot of changes were made to the forecast. Low clouds remain across roughly the eastern two-thirds of Oklahoma and parts of western north Texas this afternoon. Further clearing may occur this afternoon, especially across western Oklahoma. This evening, areas of fog may develop across southwest Oklahoma and western north Texas as winds decrease ahead of a strong cold front. Some of the fog may be dense. A little unsure about freezing fog or what impact the fog may cause as temperatures fall below freezing in west central Oklahoma by midnight. For now will leave as areas of fog. As the front moves across the area tonight, any dense fog will dissipate by sunrise Saturday. Model soundings continue to show a rather shallow moist layer behind the front. Perhaps enough lift will occur that patchy freezing drizzle may develop late tonight into Saturday. Enough cooling across roughly the northern half of Oklahoma may result in mainly snow with better chances of freezing drizzle across southern Oklahoma and north Texas. As a trough moves across the Pacific Northwest and into the northern and central Rockies, the bulk of a very cold airmass will build southward into the central and southern Plains Sunday into Monday. Wintry precipitation chances should increase again Saturday night into Sunday. Soundings indicate the best opportunity for freezing drizzle or light snow will be across the southern third of Oklahoma and northwest Texas where a deeper moist layer is expected. By Sunday afternoon/evening, dry weather is expected with very cold temperatures. The main story this weekend into early next week will be well below average temperatures. On Sunday into Monday, the very cold air will combine with rather breezy conditions to produce bitterly cold wind chill values. At this time, it appears that a Wind Chill Advisory will be required for the north half/two-thirds of Oklahoma (Sunday into Monday). Dry and cold weather is expected to prevail Tuesday into at least Thursday of next week. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 25 29 15 20 / 0 10 10 0 Hobart OK 24 30 15 23 / 0 10 10 0 Wichita Falls TX 31 33 22 27 / 10 10 20 0 Gage OK 16 26 9 18 / 0 10 10 0 Ponca City OK 18 26 9 17 / 0 10 10 0 Durant OK 37 39 26 28 / 10 10 20 10 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && $$
Area Forecast Discussion
National Weather Service Topeka KS
723 PM CST Fri Dec 29 2017 .UPDATE... Issued at 723 PM CST Fri Dec 29 2017 Updated the forecast to include a mention of very light freezing drizzle or flurries this evening. Radar is picking up on some light returns along the KS river. Additionally a few OBS are showing visibilities of 2 to 3 miles. After a few calls, the light returns on radar appears to be some light mist or fog. I don`t think this should last for very long as the models show downglide increasing behind the front. However there potentially could be a few slick spots develop on untreated roads. && .SHORT TERM...(This evening through Saturday) Issued at 230 PM CST Fri Dec 29 2017 Isentropic lift concentrated across northeastern Kansas has produced a few areas of flurries/sprinkles which were noted on radar mostly across western Missouri, although a few areas across far eastern Kansas also saw some precipitation. Kept this mention of flurries in far northeastern Kansas through the early evening. With temperatures struggling to reach above freezing, a few spritz of freezing drizzle may also occur in this area. With roadways well below freezing, this could cause hazardous driving conditions wherever this occurs. Any chances for this precipitation are expected to end by early evening with dry conditions for the rest of the period. For tonight, winds shift from the north and temperatures plummet back to the single digits with the exception of east central Kansas. Gusty winds behind the front tonight bring wind chills down between -1 to -14 across the entire area. Temperatures do not recover much during the day, with highs ranging still from the single digits in northern Kansas to the teens in east central Kansas. One the light of the forecast for tomorrow is that skies may briefly clear during the afternoon hours. .LONG TERM...(Saturday night through Friday) Issued at 230 PM CST Fri Dec 29 2017 Bitterly cold and dry conditions still look to be the main story of the beginning of the extended forecast period. The first shot comes Saturday night where low temperatures range from +1 to -5 across the area. Wind chills across the entire area will range from -12 to -19 degrees by Sunday morning. Surface high pressure of 1055mb continues to work its way into the area Sunday. Temperatures barely nudge up into the single digits on New Year`s Eve with enhanced cold air advection continuing to spill into the area. Sunday night into Monday morning looks to be the coldest of the period with low temperatures ranging from -8 to -15 across northeastern Kansas. When accounting for wind chills, values of -24 to -31 are likely making this cold snap potentially dangerous. For now, have issued a Wind Chill Watch for the entire outlook area from Saturday night through Monday morning to highlight this threat. New Year`s Day also looks to be in the single digits, with the aforementioned high pressure sliding over eastern Kansas by Monday night. Monday night looks to be the last of the nights with some wind chills below -15. From here, temperatures rebound into the 20s for the rest of the week with no precipitation to speak of. && .AVIATION...(For the 00Z TAFS through 00Z Sunday) Issued at 457 PM CST Fri Dec 29 2017 Main question is when MVFR CIGS will lift above 3 KFT. RAP and NAM are fairly progressive with improving CIGS, but obs indicate a rather broad MVFR deck across most of NEB and into southern SD. Because of this think the RAP and NAM may be a little to quick in improving CIGS. Chances for precip appear to be pretty small so once the CIGS improve, think VFR conditions will prevail through the afternoon Saturday. && .TOP WATCHES/WARNINGS/ADVISORIES... Wind Chill Watch from late Saturday night through Monday morning for KSZ008>012-020>024-026-034>040-054>056-058-059. && $$ UPDATE...Wolters SHORT TERM...Heller LONG TERM...Heller AVIATION...Wolters
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
434 PM MST Fri Dec 29 2017 .DISCUSSION...(This Evening Through Friday) Issued at 209 PM MST Fri Dec 29 2017 Broad cyclonic flow continues across much of the CONUS as very cold air sits across the northern Plains into the Great Lakes region and Northeast. Northwest flow aloft persists across the region, with a series of weak waves pushing through. Surface analysis shows arctic high pressure across Alberta sliding southeast toward the Dakotas. Temperatures have been steady or falling across the CWA. KUDX radar has been showing snowfall persisting through the day across the southern Black Hills. Snow has been increasing over the last hours across the northern Black Hills and adjacent plains. Models show leeside convergence enhancing the snowfall through the rest of the afternoon across the southeastern to eastern portions of the Black Hills and foothills. With snow already falling across portions of the Hills, will move up to the start time of the Winter Weather Advisory to when the afternoon package is issued. Rest of the headlines are in good shape at this point. Snow will increase in coverage this evening and continue through Saturday afternoon. The best snowfall rates are expected to be tomorrow late morning into the afternoon as a strong upper waves pushes through the Dakotas. Additional snowfall amounts ranging from 2 to 6 inches are expected across much of northeast Wyoming and western South Dakota. Behind the departing wave, dry weather will move into the region and continue through much of next week. Very cold temperatures are also expected through Monday. Sunday is still expected to be the coldest day, with highs ranging from 5 above to 10 below. The coldest night for most locations will be Monday morning, with lows ranging from 10 below to 30 below zero. Wind chills that morning could range from 20 below to 45 below zero. Will have to continue to monitor for possible future headlines. Much warmer air will advect in by Tuesday with highs much closer to seasonal averages but still slightly below. These temps will generally continue through much of next week. && .AVIATION...(For the 00Z TAFS Through 00Z Saturday Evening) Issued At 434 PM MST Fri Dec 29 2017 Through the overnight hours, MVFR/IFR conditions are expected within a broken band of snow oriented northwest to southeast across our area. For now, have GCC with IFR VSBYS through most of the night, though there will likely be some periods where snow weakens and VSBYS temporarily improve. Generally expect snow band to lift northeastward away from GCC as we approach daybreak, leading to improved conditions on Saturday. Given short-term model agreement, suspect that RAP will see a brief lull/weakening in snow over the next two or three hours before returning to MVFR/IFR conditions later tonight through much of Saturday. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...Winter Weather Advisory until 11 PM MST Saturday for SDZ001-002- 012-024>026-028>030-072-074. Wind Chill Advisory from 11 PM MST /midnight CST/ this evening to 11 AM MST /noon CST/ Saturday for SDZ027-041>044-046-047- 049. Winter Weather Advisory from 11 PM this evening to 11 PM MST Saturday for SDZ013-014-031-032-073. WY...Winter Weather Advisory until 11 PM MST Saturday for WYZ054-056- 057-071. Wind Chill Advisory from 11 PM this evening to 11 AM MST Saturday for WYZ055-058. && $$ DISCUSSION...13 AVIATION...Sherburn