####018012843#### FXUS63 KJKL 131035 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 535 AM EST Sat Dec 13 2025 .KEY MESSAGES... - Areas of dense freezing fog will affect mainly the mid to high terrain of much of eastern Kentucky south of the Mountain Parkway this morning. - Another light, to possibly moderate, snowfall is on its way for this evening into early on Sunday, mainly north and east of a Stanton to Jackson to Whitesburg line. - An arctic airmass moves into our region for late tonight and Sunday with significantly below normal temperatures and bitterly cold wind chills on tap. - Nearer to, if not above normal, temperatures can then be expected from Tuesday through the end of next week. && .SHORT TERM...(Today through Sunday) Issued at 515 AM EST SAT DEC 13 2025 09Z sfc analysis shows an area of deep low pressure to the north of Kentucky with an approaching cold/Arctic front off to the northwest of the state. Ahead of this impactful boundary, earlier clear skies and the recent snow allowed areas of dense fog and a low stratus to develop through much of eastern Kentucky generally along and south of the Mountain Parkway nearly to the Tennessee border. With temperatures for much of that area at 32 degrees or less this has resulted in dense freezing fog. Accordingly, a Dense Freezing Fog Advisory is in effect until 13Z. Otherwise, temperatures are running in the upper 20s to lower 30s across the JKL CWA. Meanwhile, amid mostly light westerly winds, dewpoints are running in the upper 20s to lower 30s, as well, with most places reporting near 100 percent RH on account of the fog - though a little bit of a dewpoint depression shows up north of the Mountain Parkway. The models, and their individual ensemble suites, are still in pretty good agreement aloft through the short term portion of the forecast. They all depict a large eastern trough at 5h centered north of the eastern Great Lakes. This feature amplifies greatly through the next 24 hours with a sharp pivot southeast that sends an impressive node of mid-level energy through the lower Ohio Valley and much of Kentucky by 12Z Sunday. This wave and its height falls sweep over eastern Kentucky later tonight through Sunday morning before departing to the east. This process will be enhanced by the right rear entrance of a 3h jet streak passing just north of the Ohio River between 00 and 06Z tonight. This extra enhancement will contribute to the lift available for the sfc system and its snow as it passes through. The still pretty small spread among the models generally supported using the NBM as the starting point of the forecast grids with minimal adjustments needed - mainly to include more of the CAMs details in PoPs along with some terrain enhancement late this afternoon through Sunday morning. Sensible weather features a very active 24 to 36 hour period for eastern Kentucky with what appears to be the grand finale of this recent bout of colder than normal start to the cool season. We start off this morning with the potential trouble caused by the dense freezing fog for most of the area south of the Mountain Parkway - perhaps lingering into the mid morning hours in some places. Earlier the SPS for this concern was upgraded to a Dense Freezing Fog Advisory as the threat lingered. Next up, the Arctic front will blow in here starting late this afternoon in the north and then dropping southeast through the night with its enhanced lift from upper level dynamics likely able to give the northeast quarter of the JKL CWA some 1 to 2 inches of snow - perhaps as much as 3 inches in northern Fleming County. Falling temperatures through the column will lead to climbing SLRs making for fluffier snow that should maximize its fairly meager QPF. Accordingly, a Winter Weather Advisory is in place for that portion of eastern Kentucky from late this afternoon (in the northwest) through this evening and into the morning on Sunday. The blustery northwest winds behind the front will bring in easily the coldest air of the season so far with single digits expected towards dawn west and wind chills sub zero for those parts of the area. This prompted the issuance of a Cold Weather Advisory based on the different climatological regions of eastern Kentucky with the southernmost tier having slightly milder criteria for an advisory. The CW Advisory starts at 1 am tonight for the western and southern counties running through 1 pm on Sunday. Should the cold air come in a bit quicker or winds stay up enough post frontal this may need to be extending areal-ly through the rest of the CWA. Either way, Sunday will be a bitterly cold day in that Arctic air mass with afternoon temperatures only in the mid teens northwest and low 20s in the southeast. This is a very complicated situation into Sunday morning with overlapping advisories in effect. Definitely a day to stay weather aware and prepare for the snow and cold to come tonight. The changes to the NBM starting point were primarily focused on adding in more details for the PoPs from the latest CAMs guidance and some terrain enhancement to the snow later tonight. .LONG TERM...(Sunday night through Friday) Issued at 530 AM EST SAT DEC 13 2025 While one more night of bitterly cold weather is expected at the beginning of the long term forecast period, a prominent pattern shift is poised to produce much milder conditions for the upcoming work week. The northwesterly flow responsible for the advection of an arctic airmass into the forecast area at the end of the short term forecast is expected to back towards the west and then the southwest as the week progresses. The resultant return of ridging and midlevel height rises favor a warming trend before two late- period storm systems approach. Warmer antecedent temperatures will limit the potential for widespread winter weather with these two systems, a welcome relief from the snowy and cold start to December. When the period opens on Sunday evening, the ground will likely be covered in a dry, powdery snow. Northwesterly mid-/upper-level flow will remain in place for one more night around the backside of an eastward-propagating trough. At the surface, a high pressure system will be passing directly overhead. Together, these features favor efficient radiational cooling, and MinTs are accordingly forecast to drop in the single digits area-wide by Monday morning. However, the surface high's proximity will keep winds light and variable and reduce the wind chill effect. Models collectively depict 850mb temperatures warming above the -10 degrees Celsius threshold in this time frame. Therefore, confidence in reaching Cold Weather Advisory criteria is lower on Sunday night than it is on Saturday night/Sunday morning. Higher-terrain locations near the Virginia state line are most likely to do so, but decided hold off on issuance for now. Interests are still encouraged to bundle up for the Monday morning commute though, as these low temperatures are 20- 25 degrees cooler than climatological averages for mid-December in Eastern Kentucky. Surface flow becomes southwesterly on Monday as the high pressure system settles into the Southeastern CONUS. The winds aloft will weaken and adopt more of a westerly component, and 850mb temperatures should finally climb above freezing on Monday afternoon. Under mostly clear skies, surface temperatures in the southern half of the forecast area should recover into the mid 30s. The cold air will hang on for the longest in areas north of the Mountain Parkway, where the snowpack is highest and where there could be some cloud cover. Thus, one more day of freezing high temperatures appears likely in our northern counties. There is some model disagreement on the magnitude of potential ridge-valley MinT splits on Monday night into Tuesday. Some of the available deterministic MOS guidance drops valley locations into the single digits again, but the ensemble probabilities for temperatures less than 10 degrees Fahrenheit are less than 20 percent. The coarser- resolution long term forecast guidance doesn't necessarily pick up on small-scale local geographic effects, but the bias-corrected baseline NBM guidance populated widespread MinTs in the lower half of the 20s. For this forecast package, temperatures were bumped into the upper teens in the typically colder shaded/sheltered valley locales as a middle-ground solution. If higher-resolution guidance reinforces confidence in the more dramatic splits, future forecast packages may require further edits. Quasi-zonal flow aloft and the southern surface high will keep the sensible weather quiet on Tuesday and during the daytime hours Wednesday. Southwesterly winds will become breezy in response to a system passing well to the north of the forecast area. This displaced disturbance looks rather weak and moisture starved, but it should still foster a noticeable mid-week warming trend. The entire forecast area should warm up above freezing and perhaps into the 40s on Tuesday afternoon, allowing any remaining snow to melt off. Increasing cloud cover could limit the amount of radiational cooling on Tuesday night, and ridge-valley temperature splits look less likely then. Pre-midnight lows near freezing are possible, but the persistence of warm air advection should result in temperatures in the mid 30s by the time the run rises on Wednesday morning. Expect afternoon highs to warm further into the upper 40s/lower 50s. A second, stronger disturbance will dig into the Great Plains on Wednesday night into Thursday, leading to renewed precipitation chances in the forecast area. With surface temperatures well above freezing, any overrunning precipitation with this system's warm frontal passage will fall as rain. The warm air advection regime is expected to strengthen behind that boundary. The flow aloft will become southwesterly ahead of the approaching trough axis, and southerly to southwesterly surface winds will strengthen amidst a tightening pressure gradient. Southwesterly wind gusts of 25-30mph are possible out ahead of the system's cold front. High temperatures in the mid/upper 50s will yield widespread rain showers, and some convective activity cannot be ruled out. The negative tilt of the parent troughing aloft and a strengthening 850mb jet points towards potentially favorable shear parameters, but modeled instability remains meager due to slower dewpoint recovery. Model trends will need to be monitored closely with this late-week system, but for now, the set-up favors generic gusty rain showers amidst seasonably warm highs in the upper 50s/near 60. Once the cold front sweeps through the area on Thursday night, temperatures should quickly drop into the 30s. The colder airmass will also be drier though, and a widespread changeover to snow on Friday is not anticipated. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) ISSUED AT 1250 AM EST SAT DEC 13 2025 Dense fog and freezing fog, due to stratus build down and/or where there has been some snowmelt will impact TAF locations such as KJKL, KLOZ, KSJS, and KSME at times through 14Z. Low clouds at IFR or lower will also hold on at all sites and nearby ridgetop locations into dawn. Some small improvement can be expected into the afternoon, even as a cold front nears and moves across eastern Kentucky, with some MVFR and IFR reductions lingering in the northern portions of the area through the end of the period. Snow is also forecast to develop in the more northern locations before the end of the day, and this could affect KSYM after about 23Z. Generally, light and variable winds are expected through the period. && .JKL WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 3 PM this afternoon to 10 AM EST Sunday for KYZ044-050>052-059-060-104. Cold Weather Advisory from 1 AM to 1 PM EST Sunday for KYZ044- 050>052-058>060-068-069-079-080-083>087-104-106-108-111. Freezing Fog Advisory until 8 AM EST this morning for KYZ058-059- 068-069-079-080-108>118-120. Winter Weather Advisory from 7 PM this evening to 1 PM EST Sunday for KYZ106>110-112-113-115-118>120. && $$ SHORT TERM...GREIF LONG TERM...MARCUS AVIATION...JP/GREIF ####018004944#### FXUS65 KRIW 131038 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 338 AM MST Sat Dec 13 2025 .KEY MESSAGES... - Mainly dry conditions today with wind decreasing through the day. - Well above normal temperatures and dry conditions for Sunday and Monday. - The next system approaches midweek next week with the next chance of snow in western Wyoming and strong to high wind across central Wyoming. && .DISCUSSION... Issued at 1258 AM MST Sat Dec 13 2025 If there has been something persistent for the past couple of days, it has been the Wyoming Wind Machine. It has been working overtime for the past five days or so, and it continues tonight as well. We do have a few gusts approaching high wind, but these are mainly on bluffs where impacts are few to none. And there is some good news in the forecast in this regard. The jet stream that has been responsible for the wind will begin to retreat to the north today and 700 millibar winds get cut from 30 to 50 percent. This should allow wind to decrease through the day, with most places to see at most, breezy conditions (at least by Wyoming standards). There may be just enough lingering jet energy for some showers across northern Johnson County, but any accumulation would only be a dusting with all showers over by noon. The other question will be temperatures. Areas south of the Owl and Bridger Creek range will have another mild day with some locations into the 50s. The wind has also mixed out over Natrona County, so temperatures should be above normal again. Johnson County remains rather cold and we have kept them in the 20s for high temperatures. Sunday and Monday will be dominated by flat ridging that will bring a continuation of dry conditions. It will also bring a warm up, some locations rather dramatically. This could especially be the case at Buffalo, which could be 35 to even 40 degrees warmer than today as the cold air gets scoured out. And, it turns out the Wyoming Wind Machine will only be down for maintenance this afternoon and evening, as the wind increases again in the favored southwest flow areas, mainly from Muddy Gap through Casper. However, the chance of wind gusts past 40 mph is at most 1 out of 3 and this is only at wind prone locations like Wyoming Boulevard and the high bluff locations with little impact. Things get active again for the middle of next week as the next Pacific cold front and trough approach from the west. No surprise, today's guidance has come in a bit slower today, so chances of precipitation have been lowered for Tuesday. The main impacts now look to be on Wednesday. Wind will begin to increase on Tuesday, but the main impact looks to be Wednesday. This looks similar to earlier this week with a good set up for high wind. There will be a tight pressure gradient across the area with the front approaching. The real driver of it will be a powerful jet stream, possibly over 150 knots, that will be over the area on Wednesday. The 700 millibar winds are shown as high as 75 knots. Ensemble guidance shows at least a 1 in 2 chance of wind gusts past 50 mph on Wednesday as well. It is too early for highlights, but there is a greater than 3 out of 4 chance for some High Wind Watches or Warnings to be issued for this event. This also looks to be a decent snow maker for the western mountains, with probabilistic guidance giving a greater than 9 out of 10 chance of over 6 inches of snow. Downsloping flow would keep areas east of the Divide largely dry, although some showers may occur with the passage of the front. This should bring in some cooler air, but it should still be above normal temperatures-wise given the Pacific origin of the air. Another Pacific system may then approach for another chance of rain and snow on Friday. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 330 AM MST Sat Dec 13 2025 VLIFR conditions will continue at KWRL, rapidly improving by 18Z. LLWS conditions are expected to have retreated away from KCOD and KCPR and be more located over the Absaroka and Wind River Mountains through 18Z. Wind gusts around 25kt continue at KRIW and KRKS, with a 40% chance of gusts around 35kt at KRIW through 15Z. The winds at KRIW will decrease by this time, before increasing again by 18Z. Winds will be light (10kt or less) at all other terminals through the period. The winds at KRIW and KRKS will decrease by 00Z and 02Z, respectively. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on smoke, icing and turbulence forecasts. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Hattings AVIATION...LaVoie ####018005570#### FXUS65 KBYZ 131039 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 339 AM MST Sat Dec 13 2025 .KEY MESSAGES... - Snow band shifts to the south and west this morning from being centered on Forsyth to Broadus at 6AM to being centered on Roundup to Sheridan by 9AM. Light snow amounts under 1 inch expected for these areas between 6 and 12 AM. - Cold conditions continue today with high temperatures in the single digits and teens for the lower elevations (eastern MT). - Warmer and drier weather expected to return by Sunday through early next week. Expect rapid snowmelt into early next week. - Periods of strong winds for foothills gap locations including Livingston and Nye starting tonight and lasting through the foreseeable future. Strong winds across Southeast Montana Wednesday. && .DISCUSSION... Today through Saturday... The snow band is expected to drift to the south and west this morning from being centered on Forsyth to Broadus around 6 AM to Roundup to Sheridan by 9 AM. This snow band will only be remnants of the strong band we have experienced over the last few days with additional snow amounts expected to remain under 0.5 inches. The NBM is giving locations in Bighorn County the best chance (10-30%) of receiving greater than 0.5 inches of snow from this band. Wind will be the main impact over the next 7 days. Tonight into Sunday morning will see the Idaho Falls to Lewistown pressure gradient increase into the 13-16 mb range with 700 mb winds of 30-35 kts. This brings a 50-75% chance for winds greater than 60 mph for gap areas such as Livingston and Nye. It will be a similar setup Sunday night into Monday with wind gusts near 60 mph. 700 mb winds continue to increase throughout the day Monday with a pressure gradient getting into the 15-20 mb range. This is leading to local wind guidance giving Livingston a 30% and 60% chance of getting a wind gust over 75 mph Monday night into Tuesday and Tuesday night into Wednesday. Periods of strong winds are expected to continue through the end of the week. Wednesday, an intense Clipper system is expected to pass through southern Alberta and Saskatchewan. Its main impact will be to bring strong winds across southeast Montana. The deterministic GFS is indicating 700 mb winds of 70-90 kts and 850 mb winds of 50-60 kts. ECMWF meteograms are showing winds near to above 50 kts across the forecast area. EFI tables show values of 0.8-0.9 indicating an anomalous event. The NBM is giving the plains of eastern Montana a greater than 50% chance for a wind gust over 50 mph. Strong winds can also be expected along the foothills with local guidance giving Big Timber and Harlowton 40-50% chances of getting a gust over 60 mph. Precipitation potential has increased with this system with the NBM giving lower elevations a 20-40% chance of receiving greater than 0.1 inches of precipitation. Temperatures remain cold for much of the region today with temperatures in the single digits and teens east of Billings. Locations along the foothills will be warmer in the 20s and 30s F due to downsloping winds. Upper level ridging works into the region Sunday increasing temperatures significantly into 40s F for most locations and 50s F along the foothills. Temperatures are expected to remain seasonal or slightly above seasonal over the next week. A cold front Wednesday is expected to bring a brief cooldown to the plains of eastern Montana Thursday before rebounding Friday. Torgerson .AVIATION... A passing disturbance will push cold air and snow back to the southwest through the morning hours. Although snowfall will be less intense than it has been over the past 24 hours. As the cold air surges back to the west, low stratus, light snow, and fog will bring MVFR to IFR conditions back into central areas including KBIL and KSHR. For KBIL the diminished conditions will impact the early morning push. Expect conditions to improve to VFR through the afternoon hours. SW winds will increase along the western foothills tonight, including KLVM, with gusts of 30-40 kts possible. STP && .PRELIMINARY POINT TEMP/POPS... Tdy Sun Mon Tue Wed Thu Fri ------------------------------------------------------- BIL 020 010/045 031/046 040/050 036/048 023/041 031/048 5/S 00/B 00/B 01/B 26/O 11/B 23/O LVM 046 033/055 034/055 041/052 036/048 025/043 031/050 1/B 00/N 00/N 02/R 47/O 12/S 45/O HDN 020 007/042 021/045 034/048 033/047 020/041 026/048 6/S 00/B 00/B 01/B 26/O 21/B 23/O MLS 011 001/039 023/041 034/045 029/044 015/035 022/043 5/B 00/U 00/U 00/B 23/O 11/B 11/E 4BQ 018 011/044 026/044 034/049 033/049 020/039 028/048 8/S 00/U 00/U 00/B 14/O 11/B 11/E BHK 007 904/042 024/045 032/046 027/043 008/030 017/042 2/B 00/U 00/B 00/B 24/O 10/B 11/E SHR 029 016/053 026/053 034/055 032/051 017/041 025/050 5/S 00/U 00/U 00/B 15/O 21/B 11/B && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...Winter Storm Warning in effect until 8 AM MST this morning FOR ZONES 31-32. Winter Weather Advisory in effect until 8 AM MST this morning FOR ZONES 33-36-37. WY...None. && $$ weather.gov/billings