Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/25/24


Area Forecast Discussion
National Weather Service La Crosse WI
540 PM CST Tue Dec 24 2024 .KEY MESSAGES... - Cloudy conditions continue into the weekend with high temperatures rising into the 40s, nearing 50F south of I-90 by Saturday. Low temperatures rise above freezing by Thursday night, remaining above freezing into next week. - A period of freezing drizzle is possible (0-20%) Wednesday afternoon into the overnight hours, largely dependent on temperature. - Precipitation chances (50-80%) return Thursday into Friday with rain being the expected precipitation type. Additional chances for precipitation continue into next week. && .DISCUSSION... Issued at 210 PM CST Tue Dec 24 2024 Cloudy Conditions and Warming Temperatures Ample low level moisture is depicted in nearly every model solution in the surface to ~3kft layer through the rest of the week. This suggests the low stratus of today will stick around as we head into the weekend. The biggest discrepancy in cloud amounts remains between the 24.06z GEFS and 24.06z EPS for Wednesday in the which some GEFS members suggest the potential for clear skies today into Wednesday while others indicate overcast skies. The EPS members are in much better agreement, with every member indicating 100% sky cover throughout the week. The GEFS members join in on this solution by late Wednesday. Some members of both ensembles begin to indicate some clearing on Sunday. Winds turn southeasterly to southerly on the backside of departing high pressure and upper ridging tonight and will begin to advect warm air into the region tonight and Wednesday. High temperatures begin to climb above freezing and into the 40s towards the end of the week in response, with areas south of I-90 possibly reaching 50F by Saturday as the NBM suggests a 40-80% probability of exceeding 45F. Ensemble guidance is in good agreement regarding temperatures over the next several days, with only a 2-5 degree spread in the 25th-75th percentiles in the NBM and GEFS/EPS. Thinking that we may trend towards the 75th percentile for temperatures over the next few days though given the expected cloudy skies and persistent southerly winds. Freezing Drizzle Potential The threat of freezing drizzle remains for the afternoon and overnight hours of Christmas day. As previously mentioned, model soundings depict a well saturated surface to ~3kft layer. The RAP indicates a region of isentropic ascent within this saturated layer on the 280K theta surface, moving northward with time which may provide enough lift for precipitation to fall. The 24.12z HREF joint probabilities of temperatures < 32F and measurable precipitation range from 0-20%, so this is not a high confidence scenario. Whether any precipitation is freezing or not will be largely dependent on how warm the low levels get Wednesday afternoon and how warm they remain into Thursday morning. Precipitation Chances Thursday and Friday and Again Next Week A 500hPa trough currently off the west coast of the United States as seen in water vapor imagery will move eastward into the intermountain west and eject into the plains on Thursday before propagating northward Thursday night into Friday. Forcing associated with this trough combined with PWATs in the 99.5th percentile for this time of year brings the chance for measurable precipitation to the area (50-80%), which is expected to be all rain given the previously mentioned warm air advection ahead of this feature. The axis of highest QPF is currently expected from northeast Iowa into central Wisconsin with total mean amounts of 0.25-0.3 inches within this axis although 0.2 inches is possible elsewhere. NBM probabilities suggest a 40-50% chance of exceeding 0.3 inches within this axis of higher amounts areas and a 20-30% chance to exceed 0.5 inches. Additional shortwaves traverse through the mean flow over the weekend such that precipitation chances continue throughout the weekend and may bump up the overall precipitation amounts through the weekend. The next best chances for precipitation return early next week as another 500hPa trough moves into the region. There is still quite a bit of uncertainty surrounding this next system as deterministic guidance has various solutions regarding timing and location. The WPC cluster analysis is still in good agreement regarding this trough/system developing, but the uncertainty in track and timing leads to multiple possibilities for precipitation type. The current track seen in the NBM suggests a wintry mix scenario across our area, but details regarding this possibility will continue to become clearer in the coming days. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 533 PM CST Tue Dec 24 2024 Surface high pressure remains over the region with MVFR ceilings for much of the area, but also some thinning or patchy breaks over parts of southwest Wisconsin. The 24.12Z HREF has a signal for areas of fog from the Missouri River Valley into northwest IA and western MN/northern WI. Patchy 40-70% probabilities locally for 3sm or less. Low level moisture remains in place tonight and with increasing low level moisture transport Wednesday evening, when the depth of the moisture increases. Most of the forecast soundings/hi-res models show lowering of ceilings from MVFR to IFR this evening or overnight. The 900mb winds are somewhat elevated, but have patchy fog in for now for parts of southeast MN and northeast IA and north of I94. Winds remain light and variable or light southeast tonight and Wednesday. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Falkinham AVIATION...Zapotocny
Area Forecast Discussion
National Weather Service Dodge City KS
536 PM CST Tue Dec 24 2024 .KEY MESSAGES... - Continued above normal December high temperatures for SW Kansas. - Forecasted fog Wednesday and Thursday mornings. - Slight rain chances (10-40%) Thursday and Friday. && .DISCUSSION... Issued at 317 PM CST Tue Dec 24 2024 The forecast area this week will be entertained by a few low pressure systems. The first of which moved through SW Kansas earlier on Tuesday and has dug into Oklahoma. Outside of lingering cloud cover near the OK/KS border, the systems`s influence is primarily done impacting the forecast area. RAP Mesoanalysis shows some upper- level ridging building and moving in to fill the vacuum of the exiting system. Synoptically that pattern will hold until late Wednesday. In the meantime, Tuesday will feature clear skies and nearly everywhere reaching highs into the 50s (>75% chance). Models and ensembles continue to seem confident in Fog chances Wednesday morning. The forecasted fog has taken on a "U" with the heaviest areas in the far east of the forecast area on one end and up through Garden City on the other. Whether that exact shape takes hold is hard to pin down, but the overall fog chances are around 40% from ensembles. It should be noted the HRRR is very aggressive with large areas of <0.25 mi visibilities. Temperatures Wednesday are expected to be similar to Tuesday if not a couple degrees cooler due to some cloud cover. The next notable system arrives very early Thursday although trends continue to look worse for the CWA with regards to meaningful precipitation. Latest runs of ensembles continue to push the track south and results in rain chances diminishing even further. Chances for accumulations are only above 25% in the four southeastern counties, and even those counties are at a 50/50 chance from national ensembles. What was once looking like light widespread rainfall a few days ago now appears to be confined to only the southeast where rain chances are not even certain. Extrapolating these trends could result in almost no rain for all of SW Kansas. Regardless of the rain widespread visibilities are expected for nearly the entire forecast period as fog/low stratus develops Thursday morning and is stubborn to clear. Following into Friday, ensembles have a mid-level shortwave trough developing and moving into SW Kansas. Precipitation chances with this system has held firm at a 25-40% chance for accumulation via ensembles. There is not clear consensus among longer ranged models with the ECMWF being much wetter than the NAM or GFS. Considering the last few systems have leaned on the drier side of guidance, take Friday`s chances with a hint of skepticism until Thursday`s system clears out. The modeled lower-levels are warm enough to prevent snow from being a reasonable possibility at this point in time. After Friday, the weekend consensus is dry and warm, well above normal. Highs could reach into the 60s with a 75% chance near the KS/OK border and between a 40-75% chance elsewhere from long ranged ensembles. Ensemble trends are getting more optimistic of another low pressure system passing through the northern zones Monday. The next chance for precipitation occurs with the system heading into Tuesday as well as the first meaningful potential for wintery precipitation. That being said, large uncertainty exists and will need to be honed in future forecasts. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 524 PM CST Tue Dec 24 2024 Clear sky across most of the area through the evening will be replaced by invading stratus overnight. As time gets toward morning, the stratus should deteriorate to LIFR or even VFR category as the HREF probability for less than 1000 ft cigs is coming in from 50 to 75% at Hays and Liberal. && .DDC WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...KBJ AVIATION...Russell
Area Forecast Discussion
National Weather Service Grand Forks ND
1003 PM CST Tue Dec 24 2024 .KEY MESSAGES... - Dense fog tonight through Wednesday morning. - Above average temperatures mid to late week will contribute to 30% chance for light rain or wintry mix Friday to Saturday, mainly within Minnesota. && .UPDATE... Issued at 1003 PM CST Tue Dec 24 2024 Dense fog continues to be reported within the counties under a dense fog advisory, while light fog and low clouds prevail to the east. There is still the small area in west central MN with 1/2sm vis, but this has not expanded and BL winds 10-25kt are likely playing a role in limiting dense fog development along and east of the Red River Valley up to this point. CAMs and related blends continue to try to show dense fog development in these areas (after initializing on current obs) and this is just not happening yet. I remain skeptical in widespread dense fog impacts east of the current advisory, and am comfortable just monitoring trends and expanding/extending if it become necessary. UPDATE Issued at 701 PM CST Tue Dec 24 2024 Dense fog is already being reported at KDVL and Valley City within the earlier clearing area, in line with locations where the Dense Fog Advisory is in place. To the east where winds are stronger lighter fog is being reported, however guidance continues to show an expansion of dense fog across our entire region over the next 6hr. Obs haven`t matched this trend in CAMs where winds are higher (likely helping with mixing) and each new run of CAMs have delayed this expansion of dense advection fog. I`m still not confident enough in advisory expansion at this time, but will continue to monitor. && .DISCUSSION... Issued at 256 PM CST Tue Dec 24 2024 ...Synopsis... Water vapor imagery this afternoon shows weak upper trough passing through the eastern Dakotas into Minnesota, migrating eastward. Behind this departing upper trough is shortwave upper ridging building into the Northern Plains. This is ahead of deep upper troughing extending over the Pacific coast. At the surface, high pressure centered near the WI/MN/IA region is helping increase the pressure gradient over eastern Dakotas into western MN. The increase in pressure gradient is bringing breezy southerly winds, particularly within the Red River Valley. This is producing drifting and blowing snow, and will continue to do so until the gradient eases some this evening. With the shortwave upper ridging building toward our area, the pressure gradient easing with and temperatures decrease tonight, dense fog is forecast to redevelop tonight into tomorrow. More details on fog potential can be found below. Shortwave upper ridging over our area will be short lived with part of the deep upper troughing currently over the Pacific coast migrates into the Northern Plains by late Wednesday. This will help increase the pressure gradient, and as such another bout of breezy southerly winds are forecast by Wednesday afternoon into evening. This brings another chance for drifting and patchy blowing snow, particularly within the Red River Valley. With this incoming trough, subtle increase in low level moisture and forcing aloft will bring a chance for freezing drizzle/mist late Wednesday into early Thursday. Questions remain on if enough low level moisture will be enough to generate precipitation, lowering confidence on potential impacts to travel conditions late Christmas into early Thursday. As the upper troughing moves through Thursday, ensemble guidance weakens the trough by Thursday, with upper ridging/southwesterly flow building aloft. This comes ahead of a stronger upper trough moving into the Upper Midwest out of the Southern Plains around Friday-Saturday. More on this found below as well. ...Dense fog through Wednesday morning... As temperatures decrease amid radiational cooling within portions of eastern ND, confidence is highest here is where dense fog will form tonight. This is backed by higher probabilities in dense fog as offered by guidance like 12Z HREF and recent HRRR runs. Thus a Dense Fog Advisory has been issued for areas in eastern ND west of the Red River Valley through Wednesday morning. There is still a chance for dense fog elsewhere tonight, however confidence is not yet high enough to issue any advisories out yet. This is part of an extended period of dense fog amid freezing temperatures that started early this week, and has resulted in rime ice/hoar frost accumulation on exposed objects, including power lines. With additional frost accumulation possible if not likely within dense fog tonight/Wednesday morning, this may introduce potential impacts to power infrastructure should large accumulation of frost continue onto power lines. From a historical perspective, power-related impacts from frost accumulation isn`t uncommon in North Dakota. However, details on how much accumulation or duration of dense freezing fog that typically lead to these impacts remains uncertain. There remains uncertainty in how frost accumulations have faired in areas with winds between 10-20 mph, as well as sunshine in portions of eastern ND. Recent webcams show there has been some shedding of frost accumulations in places like northeast ND. This may indicate some areas have `reset` in their accumulations, and lowers chance in impacts to power infrastructure. However, confidence remains degraded in coverage of this `reset` and compounds uncertainty in impact potential after additional frost accumulation tonight/Wednesday morning. Yet another additional layer of uncertainty is how potential freezing drizzle between Wednesday and Friday may play into this. Previous events of long duration freezing fog leading to large frost accumulation followed by light rain/drizzle has led large impacts from power outages, notably in western ND in 2009. Confidence in freezing drizzle to occur in our area should increase, especially by late Thursday. ...Light rain and wintry mix potential Friday to Saturday... With general upper ridging/southwest flow aloft late this week, relatively mild temperatures are forecast to advect over the Northern Plains from the High Plains via chinook wind processes. General increase in moisture is strongly suggested by ensemble guidance around Friday in association with the incoming stronger Southern Plains trough. These combine to promote above average temperatures near the freezing mark along with increase chance in precipitation. Most ensemble guidance favors liquid as dominant precipitation type Friday to Saturday based on above freezing temperatures at the surface. However, confidence is lowered in temperatures, mainly because recent trends in guidance the last few days have shown a warm bias, likely due to struggles in handling milder temperatures over current widespread snowpack in our area. Thus, confidence in strictly rain is lowered. It is possible temperatures could be closer to freezing or below freezing bringing a chance for wintry mix. There could be a period of freezing drizzle to also precede steadier precipitation Friday to Saturday. These could bring some winter impacts to the region, although confidence is low in more refined details at this time. Most ensemble guidance still favors Minnesota locations to hold relatively best chance for precipitation Friday to Saturday (30%), with overall amounts remaining light as bulk of stronger, more consolidated forcing is advertised to move closer to the western Great Lakes region. There remains the possibility of weaker waves to move out of the Northern Rockies into the Northern Plains around this time, also offering some potential for light precipitation late this week. Temperatures look to trend closer toward average getting into early next week as the upper trough migrates east and flat, northwesterly flow settles into the region. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 526 PM CST Tue Dec 24 2024 There is currently a few clearing regions in northeast ND and north central MN, otherwise MVFR to IFR ceilings are already in place with fog (1-6sm) across eastern ND and northwest MN. Low level moisture will continue to advect into the region due to southerly flow and with radiational cooling the stratus and fog will fill in and dense fog (1/4sm) will begin to develop. The best chance for dense fog will be towards KDVL, however there is a chance for all location to at least have LIFR ceilings and 1/2sm vis into the morning hours Wednesday. There is a signal for improvement during the daytime period (at least with visibility), however VFR conditions if they develop would likely be for a brief period before low stratus and MVFR to IFR conditions redevelop by the evening hours. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...Dense Fog Advisory until noon CST Wednesday for NDZ006-007-014- 015-024-026-028-038-049-052-054. MN...None. && $$ UPDATE...DJR DISCUSSION...CJ AVIATION...DJR
Area Forecast Discussion
National Weather Service Topeka KS
534 PM CST Tue Dec 24 2024 .KEY MESSAGES... - Dense fog is forecast to develop this evening and persist through the Morning Christmas Day. - The active weather pattern continues through the end of the week with chances for light rain. && .DISCUSSION... Issued at 208 PM CST Tue Dec 24 2024 An active weather pattern with a series of shortwaves affecting the area is complicated by a shallow cold airmass as seen by the stratus that slowly moved southwest into the area. The RAP and NAM have been consistent in this shallow cold and nearly saturated airmass continuing to expand southwest tonight. And as long as the ridge axis remains over the forecast area, the low clouds and fog are probably going to continue being the main sensible weather. Forecast soundings and CAMs are in good agreement for the stratus to lower and limit visibilities in dense fog. So will go ahead and issue an advisory beginning this evening and continuing through the morning. Santa will be glad to have Rudolph on his sleigh tonight. An overall lack or forcing or vertical motion suggests visibilities will be the only impact through Christmas Day. Some freezing fog across parts of northern KS may deposit some ice on elevated surfaces. But surface streets should be alright with soil temps still around 40 degrees. A warm air advection pattern sets up Wednesday night and more of the models are starting to show some QPF in the 06Z to 12Z Thursday time frame. So have some slight chance POPs for measurable precip. The expectation is for mainly drizzle to develop as isentropic upglide increases lift within the stratus deck. Additionally the warm air advection is forecast to keep temps above freezing, so the drizzle should be all liquid. Better forcing and stronger vertical motion is progged to impact the area Thursday afternoon and evening. This is when the forecast has higher POPs and outright rain. Additional shortwaves are forecast to move through the central plains Friday and into Saturday. The NBM keeps some chance POPs into Friday night which seems reasonable. A little more spread in timing of the waves increases uncertainty in the POP forecast and how quickly precip chances come to an end. So have stuck with the NBM and POPs less than 20 percent on Saturday. The models seem to be coming to a similar idea for a wave to dive southeast through the plains on Monday, but differ on the track of the wave. Ensembles from the 00Z runs suggests chances for precip may be a little better (30 to 50 percent) than what the NBM and official forecast has. But until the operational runs show better agreement in the track of the system, will stick with the NBM. Will need to keep an eye on this as models do show some colder air moving in with the wave. So there is some potential for rain changing over to snow. So far the 00Z ensembles show the potential for any snow accumulations over a half inch to only be 10 to 20 percent. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 534 PM CST Tue Dec 24 2024 Save for very early at MHK, confidence is high in IFR or worse conditions at all sites through this forecast with surface ridge extending from high pressure to the northeast only nudging east while slowly modifying and a damp shallow airmass oozing southwest at this writing. Main issue is when and how low conditions will go and then rise again. Have kept close to previous forecast and closer to the RAP which has a better handle on the situation, with VLIFR conditions by 09Z and little improvement until around 16Z. Minor boundary layer mixing and relatively warm ground temperatures could be enough to keep conditions LIFR however. && .TOP WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory from 10 PM this evening to noon CST Wednesday for KSZ008-KSZ009-KSZ010-KSZ011-KSZ012-KSZ020-KSZ021- KSZ022-KSZ023-KSZ024-KSZ026-KSZ034-KSZ035-KSZ036-KSZ037-KSZ038- KSZ039-KSZ054. && $$ DISCUSSION...Wolters AVIATION...Poage
Area Forecast Discussion
National Weather Service Tulsa OK
917 PM CST Tue Dec 24 2024 ...New UPDATE... .KEY MESSAGES... Updated at 916 PM CST Tue Dec 24 2024 - Areas of fog and drizzle persisting thru the night mainly SE OK to NW AR. - Another dreary, cloudy day expected Christmas Day, with a few light showers and/or drizzle possible, especially far eastern OK and NW AR. - Showers and isolated storms return Thursday into Thursday night. - Drier, sunnier, and warmer this weekend. && .UPDATE... Issued at 916 PM CST Tue Dec 24 2024 As forecast, the nearly stationary clearing line to the north and west of Tulsa is showing signs of a retreat westward, especially across southern KS. Confidence in dense fog development is not high enough in NE OK to maintain mention at this time. Thicker fog has developed down near the Red River, but confidence in a widespread dense fog event is not high. Areas of fog mention will be maintained there. Aside from some minor tweaks, no other changes needed to the forecast at this time. Lacy && .UPDATE... Issued at 622 PM CST Tue Dec 24 2024 The main update made this evening was to reduce/remove thunder potential over far SE OK. Convection has largely shifted south and east of the region down into TX. Still some potential for dense fog mainly to the north and west of Tulsa later tonight where low clouds have cleared. The clearing line has become more or less stationary now with the loss of daytime heating. Recent runs of the HRRR also suggest that this clearing line will back up to the west a bit later on tonight. If current obs trends hold and the HRRR has the right idea, the potential for dense fog in NE OK will be low. Will continue to monitor this evening. Lacy && .SHORT TERM... (The rest of this afternoon ) Issued at 141 PM CST Tue Dec 24 2024 Slow moving upper low moving across north Texas this afternoon will continue to trudge eastward tonight. Persistent band of light to moderate rain with occasional lightning strikes will continue to push slowly to the southeast through early this evening, but light showery precipitation is likely to persist on through tonight for much of southeast OK and northwest AR. Behind that a shallow cool and basically saturated airmass will linger, with areas of light drizzle and some fog making for a rather dreary, albeit mild, Christmas Eve. Some breaks in the stratus deck have been noted near the OK/KS border this afternoon and any areas that see significant clearing will be susceptible to dense fog development this evening. More likely scenario still looks to favor a persistent cloud deck and less fog potential, but will need to monitor closely. Temperatures won`t fall much tonight and have nudged forecast low above the NBM. && .LONG TERM... (Tonight through Tuesday) Issued at 141 PM CST Tue Dec 24 2024 AS the upper low continues to make slow progress east, showers will continue to gradually decrease during the day across far eastern OK and northwest AR, with persistent cloud cover and patchy drizzle/fog over the remainder of the area. This results in a short thermometer again for Christmas Day, and as such have undercut the NBM values by a few degrees. In the meantime another system currently moving onto the western U.S. will be approaching. Increasing warm advection Wednesday night may result in expansion of light showers back across a good part of the area, though any amounts would be very light. Eventually by Thursday afternoon the influence of this system will be felt, bringing an end to the drizzle and fog, but also with expanding corridor of light to moderate showers and some embedded thunderstorms. While models have struggled with the evolution of this system, the higher thunder and attendant severe weather chances still appear focused across central and eastern TX, and possibly into southeast OK by afternoon and evening. While locally heavy rainfall is possible, this system will be more progressive and shorten the duration of significant rainfall. The progressive pattern continues into the weekend as another system immediately follows on Friday. At his point the limited moisture return looks to keep rain chances limited and generally confined to areas farther east Friday night into early Saturday. BY this time, the sun should finally make an appearance and once it does, daytime temps will warm well above average with more typical diurnal ranges. The next notable system beyond that is forecast to move into the Plains about Monday. Winds should increase notably ahead of the system, followed by considerably cooler temperatures to start the new year. At this point precip chances look focused to the northeast of our forecast area. && .AVIATION... (00Z TAFS) Issued at 523 PM CST Tue Dec 24 2024 IFR/LIFR cigs to prevail for much of the valid TAF period, along with IFR/MVFR vsbys in fog. Brief periods LIFR/VLIFR vsbys will be possible, mainly across the NW AR sites between 09-15z when at that time the aforementioned prevailing cig and vsby categories can be expected for the remainder of the TAF period. && .PRELIMINARY POINT TEMPS/POPS... TUL 43 51 48 59 / 0 10 20 60 FSM 48 57 51 62 / 40 30 20 60 MLC 46 56 50 62 / 30 20 20 70 BVO 37 50 43 59 / 0 10 10 50 FYV 43 57 47 62 / 30 30 20 50 BYV 45 52 48 58 / 40 30 20 50 MKO 46 53 50 59 / 20 20 20 70 MIO 42 52 48 60 / 10 10 20 50 F10 45 53 48 59 / 10 10 20 70 HHW 52 58 52 62 / 20 20 10 80 && .TSA WATCHES/WARNINGS/ADVISORIES... OK...None. AR...None. && $$ UPDATE...30 SHORT TERM...14 LONG TERM....14 AVIATION...23