Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/07/25


Area Forecast Discussion
National Weather Service Cheyenne WY
859 PM MST Mon Jan 6 2025 .KEY MESSAGES... - Winter Weather Advisories in effect for light snow with 2-4 inches possible for the I-25 and I-80 corridor including Cheyenne today through Tuesday. Locally higher amounts possible. - Active long term pattern continues through the week with multiple chances for light snow, mainly in the mountains. && .UPDATE... Issued at 852 PM MST Mon Jan 6 2025 No major changes made to the forecast as of 04Z this evening as the forecast remains on track. Mild adjustments made for the cloud coverage across the region with slight tweaks to PoPs around Cheyenne. The biggest change was adding the mention of freezing fog to regions along the I-80 corridor from the I-80 Summit east through Cheyenne County. Freezing fog should be patchy in nature and likely come to an end as the sun begins to rise. Most short range guidance shows fog coming to an end by 14Z. && .SHORT TERM /THROUGH TUESDAY/... Issued at 213 PM MST Mon Jan 6 2025 Latest upper air analysis depicts the trough axis, currently centered across the Ohio Valley, has continued to travel east as the closed low become absorbed into the main flow, with the next deep Pacific trough digging into the Intermountain West. Throughout the morning hours, an upper level disturbance embedded within the main flow pushed southeast around 09z this morning, allowing snow to develop in the morning hours, combined with winds being much lower than otherwise anticipated across Laramie county. Due to the minimal downsloping to help limit the snowfall from the periods of calm winds reported at the ASOS, snow persisted throughout the morning and afternoon hours. Attention in the short term forecast focuses on the next trough that is expected to come within range in the afternoon hours with active weather expected to persist as snow continues through late Tuesday. Forecast soundings continue to suggest light to moderate snow with this next system as low to midlevel moisture is well within the dendritic growth zone. This becomes much more evident in the lower counties across the CWA, with the moisture profile centered between -10c and -20C through early tomorrow afternoon. Should begin to see snow chances decrease late tomorrow afternoon once dry air becomes entrained in the midlevels. PWAT anomalies support this model solution, having PWATs around -1.5 sigma below climatology digging southward across northern Wyoming beginning around 12z Tuesday and into northern Colorado by 00z Wednesday. Therefore, will likely see precipitation beginning to clear from north to south, as the upper level trough begins to split into a closed low across southern Arizona. Some concerns persist across the northern counties in the Nebraska Panhandle with forecast soundings having a deep saturated layer, with the lowest levels within 0c to -10c up to 1km before dropping to -10c to -20c above 1km. In the event the midlevels become entrained with drier air a bit sooner than anticipated, could see freezing drizzle and freezing fog develop as have been observed a few days prior. Although, snow forecast seems the most reasonable solution for the Nebraska Panhandle with the inversion aiding in continued snow developing with dendrites falling though the layer and increasing growth from the supercooled liquid in the lower levels. Other areas to monitor will be the Laramie Valley, where favorable northwesterly flow will aid in increased upslope flow. Went ahead and continued trending PoPs upwards for the Laramie Valley through this evening before northeasterly flow takes hold and switches from upslope to downslope for that area. In addition, also bumped up QPF with the latest HiRes model guidance keeping totals upward to three inches for the city of Cheyenne to match Winter Weather Advisories in effect through tomorrow morning. Lastly, will need to monitor the Summit as well, with the latest HRRR indicating locally higher amounts possible. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... Issued at 213 PM MST Mon Jan 6 2025 The long term forecast remains on track with multiple fast moving systems expected to impact the CWA through the end of the week. The active pattern can be attributed to somewhat of a blocking high sitting in the Pacific off the coast of California. This strong ridge over the Pacific will extend as far north as southeast Alaska. This will cause any system that impacts the CWA to drop out of Canada from the north/northwest. Being from Canada these systems will bring colder temperatures and some precipitation chances. The first system will arrive Wednesday night, dragging a cold front along with it. Colder temperatures can be expected for Thursday as 700 mb temperatures behind the front drop to about -12C. This will lead to chilly temperatures with highs struggling to get to freezing on Thursday. Given that this system is from Canada, moisture values are rather unimpressive. Orographic lift will provide the mountains with a few inches of snow Wednesday night into Thursday, however, the lower elevations will likely not see any accumulation with this shortwave. Following quickly behind this system, another will arrive Friday night, bringing the potential for high winds and greater snow chances. With the onset of this system, in house guidance is pinging pretty high probabilities for high winds in the usual southeast Wyoming wind prones. This would be a gradient driven event with both elevated values for MSLP gradients as well as CAG-CPR 700 mb height gradients. As a result, winds aloft will respond, maxing out around 50 to 55 kts with good subsidence, so these winds could make it down to the surface. Timing of high winds will be late Friday night into Saturday morning. Precipitation will move into the CWA on Saturday. Precipitation looks a bit more widespread with this system, with snow chances likely outside of the high terrain. Will have to keep an eye on snow amounts as precipitation is expected Saturday and will linger into the day Sunday. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 437 PM MST Mon Jan 6 2025 An upper level disturbance is expected to move through the area this evening and overnight. This will bring another round of light to moderate snowfall to the region. Some of the snowfall may be heavy at times especially near the higher terrain (at or above 7kft) of the Laramie Range. Most locations will experience MVFR/IFR conditions with the higher terrain above 7000ft most likely seeing LIFR conditions. The snow should taper to flurries by mid morning Tuesday with ceilings generally climbing above 2kft. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Winter Weather Advisory until 8 AM MST Tuesday for WYZ116>118. NE...None. && $$ UPDATE...AM SHORT TERM...MRD LONG TERM...SF AVIATION...REC
Area Forecast Discussion
National Weather Service Dodge City KS
519 PM CST Mon Jan 6 2025 .KEY MESSAGES... - Unseasonably cold temperatures today for much of the area with fresh snowpack and light northerly winds. - Light snow is likely along and west of US-83 daytime Tuesday, but snow totals will be minimal. - Another chance of snow exists Thursday into early Friday, however uncertainty remains. && .DISCUSSION... Issued at 200 PM CST Mon Jan 6 2025 Midday water vapor satellite imagery and RAP upper air analysis reveal broad, longwave troughing envelops the entirety of the CONUS, with a couple vorticity maxima emanating through the flow; one near the Appalachians and another over the Pacific Northwest/far western CONUS. At the surface, high pressure has built into the central plains in the wake of the weekend storm, supporting widespread clear skies across southwest KS. Despite plenty of solar insolation, fresh snowpack and light northerly winds will keep most locations below freezing, with the only exception being far western KS near the CO border where little snowpack exists. Tonight will be quiet, with light winds but increasing clouds over the western zones leading to Tuesday morning lows ranging from near zero northeast to the mid-teens southwest. Early Tuesday, short range ensembles agree the western vorticity max will have dug southward to near Los Angeles by 12Z. As this happens, low-level upslope flow and moisture return in eastern CO and western KS will provide enough support for light snow to develop mainly along and west of US-83 and continue through much of the day. Snow totals look to be fairly minimal, with HREF probability of 1" of snow or greater reaching into the 50-70% range only in pockets of Hamilton and Stanton County, so 0.5-1" of snow appears to be a good bet. Daytime Wednesday, medium range ensembles suggest downsloping winds will return to southwest KS as surface high pressure slides southeast into the ArkLaTex region. This along with partly cloudy skies should foster a noticeable jump in temperatures with afternoon highs reaching into the low to upper 30s. On Thursday, ensembles are implying yet another chance for light snow will materialize across our area as a pair of vorticity maxima merge over northern Mexico and begin to eject onto the High Plains. However, disagreement remains between the two main global model ensembles, with the ECMWF EPS mean showing around 0.5-1.0" of snow while the GEFS mean has virtually nothing. Given the wave`s positive tilt and the strongest forcing being displaced well to our south, the GEFS solution seems to be the most realistic at the moment, but trends will be monitored. Over the weekend through the end of the period, ensembles agree broad, longwave troughing will remain in place over the CONUS, signaling below normal temperatures will continue for the foreseeable future. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 519 PM CST Mon Jan 6 2025 A few hours into the period, cloud cover will move into the forecast area from the west. Around 14Z, lower cloud cover will develop resulting in lowered flight categories excluding HYS. With the lower ceilings, GCK and LBL has a slight chance (10-20%) for light snow, but only minor visibility impacts are expected. && .DDC WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Springer AVIATION...KBJ
Area Forecast Discussion
National Weather Service Gray ME
1045 PM EST Mon Jan 6 2025 .SYNOPSIS... Temperatures will continue to run below normal through most of this week with mostly dry and breezy conditions as the storm track will be south of New England. There could be a slight warming trend toward the end of the week. && .NEAR TERM /THROUGH TUESDAY/... 1045 PM Update... Area webcams and AWOS observations indicate that light snow is falling across the mountains and towards the Canadian Border and therefore increased PoPs to account for this activity. Otherwise, just made some minor adjustments to temperatures and winds. In addition, the last several runs of the HRRR as well as NAM are showing a growing potential for a period of strong northwesterly wind gusts tomorrow afternoon/evening with locally higher gusts possible within downslope areas. As a result, blended some of this guidance into the forecast which brings gusts to near wind advisory criteria in some locations. Previously... 605 PM Update... Minor changes to reflect latest observational trends. Other than loading in the latest sfc observations and tweaking winds and sky cover, the inherited fcst remains on track. Previously... Coastal low continues to pass well to our S this evening, only producing some mid to highs clouds across the CWA. The system which will have a bigger impact on us later tonight into Wednesday will be the the double closed 500 MB lows over E Canad and their Fujiwara spin, as the W low shifts SE out of srn Quebec this evening and across N New England overnight. This will bring another round of clouds to the area and the chance of SHSN in the mtns, but the bigger effect will happen late tonight and Tuesday as we see upslope snows develop and winds increase again toward daybreak. Lows range from around 5 above in the N to 10-15 in the S. && .SHORT TERM /TUESDAY NIGHT/... Gusty NW flow picks everywhere a few hours after sunrise with gusts 25-30 mph common during the day Tuesday. Well see a fair amount of clouds early as the the flow remains unblocked right behind this system, but becomes more blocked later in the day. A few flurries are possible just downwind of the mtns, in the foothills as well. In the mtns there will be a period of time, probably midday to afternoon, as the flow becomes blocked, that the upslope SHSN will really surge, and several inches of snow will be possible in the favored upslope areas, and some of the notches as well. But most of the will be above 2500 ft. Still could see an inch or two spots in the valley areas, especially through the Whites Tuesday into Tuesday night. Highs on Tuesday range from 15-20 in the mtns to the mid 20s in the S, while lows Tue night will generally be in the +5 to +15 range. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... 04Z Tuesday Long Term Update.. There continues to be significant uncertainty in regards to a potential storm system this upcoming weekend with the GFS and its ensemble members the furthest north while the the ECMWF misses New England by a wide margin to the south and east. As a result, did not veer from the latest NBM given this forecast uncertainty. It will otherwise remain cool and breezy through much of the period. Previously... Overview: Broad cyclonic flow remains overhead through midweek, allowing breezy conditions, cool temperatures, and upslope snow showers in the mountains to continue. A change in pattern does not seem likely until the first half of the weekend. Details: Continued to increase precip chances in the western ME mountains and northern NH through mid to late week. The NBM is having a difficult time addressing this setup, and opted to instead use blended deterministic models which have been fairly consistent picking up on upslope snow for the NW slopes. With enough moisture in the low to mid levels, a consistent NW flow, and tight pressure gradient, the setup is there for light snow much of the week here. Will likely see gradual light accumulations...generally 1 to 4 inches in northern NH and far western ME...more at windward faces and spine of the Whites. Otherwise, a tight pressure gradient keeps winds gusty through the week, particularly during the afternoon hours where mixing deepens. This means some gusts to 30 mph Wed and Thurs afternoon for parts of southern NH and foothills, with up to 25 mph elsewhere. Amid the cool airmass, this may lead to wind chills remaining in the single digits, above and below zero, into midweek. Extended deterministic and ensemble guidance has been hinting at the next storm system to impact the east coast moving in during the Sat/Sun timeframe. There has been a wide spread of solutions as low pres forms over the southern Plains and tracks towards the east coast. Thus far, confidence in a final solution is very low as little consistency exists run to run and suite to suite. Spread of the low`s center can vary some 300 miles or more, and this has major implications for the forecast. Current assessment based on ensemble trend is the low taking a flatter course into the Atlantic off the Mid-Atlantic coast while some outliers cruise further north towards the Gulf of Maine. With a rather strong low developing over TX, there is more uncertainty how this maintains strength as it tracks east. Worth to track, but overall trend is supporting a shift of pattern (mainly ridding the region of broad cyclonic flow) late this week into the weekend. && .AVIATION /04Z TUESDAY THROUGH SATURDAY/... Short Term...Mainly VFR expected through Tue night,except at KHIE which will likely see periods of MVFR cigs beginning tonight through Tuesday, and perhaps some brief IFR in SHSN, especially on Tue afternoon. NW winds pick up again on Tuesday with morning with gusts to around 25 kts at times. Long Term...VFR with NW gusts up to 20 kts for much of the mid week. HIE will likely see chances for light SN through the week, tapering Friday. Can`t rule out some SHSN making their way out of the western ME mountains and northern NH, but these time frames may be short and restricted more towards the foothills, rarely further to the coast than AUG/LEW/IZG/CON. && .MARINE... Short Term...Weak low pressure crosses the waters tonight with strong NW flow behind it starting late tonight and continue into Tuesday night. Gales are expected on the open waters Tuesday and at least into Tuesday evening, with some to gusts approaching 40 kt. SCA conditions are expected in the bays. Light freezing spray continues into Tuesday night. Long Term...Within broad cyclonic flow, northwest winds and gusts remain in SCA criteria through mid week. There will be the chance for occasional gusts to Gale as well, primarily over the outer coastal waters Wed/Thurs. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Gale Warning from 7 AM Tuesday to 8 AM EST Wednesday for ANZ150-152-154. Small Craft Advisory from 7 AM Tuesday to 8 AM EST Wednesday for ANZ151-153. && $$ NEAR TERM...Tubbs SHORT TERM...Cempa LONG TERM...Cornwell
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
846 PM CST Mon Jan 6 2025 .KEY MESSAGES... - Lake effect snow--briefly heavy--shifting into Porter County will lead to snow-coated roadways and slick travel this evening. - Patchy freezing drizzle on the periphery of the snow band may lead to some slick spots on untreated surfaces across parts of Newton, Jasper, Benton, and Iroquois counties. - Chance (30-50%) for some accumulating snow Friday. && .UPDATE... Issued at 847 PM CST Mon Jan 6 2025 Primary lake effect band has shifted into northwest Indiana early this evening, and continues to gradually work its way eastward. Hourly rates are likely around an inch (plus) per hour in the heart of the band, although given the eastward progression, the residence time of these higher rates has generally been limited to about 60-90 minutes or less. Did boost snowfall amounts a few hours ago, although may not quite have been enough. That said, the main part of the band is shifting entirely into Porter County at this time, and will continue with targeted GNOWs and some harder messaging here with things expected to wind down through about 1 AM or so. Latest radar imagery shows things becoming a bit more cellular, and hires guidance depicts a gradual shearing apart of the band through the late evening. Brushed up PoP/weather trends through the night. Received a few reports of light freezing drizzle across our southern locales, and while our radar continues to overshoot this shallow precipitation, not seeing indications of significant visibility reductions with it which suggests this may not be heavy/persistent enough to cause significant travel impacts. Will continue to indicate some chances for freezing drizzle around the periphery of the lake effect band through the night, but things should be on the downtrend overnight. Carlaw && .DISCUSSION... Issued at 345 PM CST Mon Jan 6 2025 Through Tuesday Night: Lake effect precipitation continues this afternoon across the Chicago metro and points downstream. The coldest temperatures within the parent stratus deck have been sampled by aircraft to be around -10C just beneath a strong temperature inversion between about 4000 and 6000 ft AGL. This is right on the cusp of what is usually needed for efficient heterogeneous ice nucleation to occur and support snowflakes being the dominant/sole hydrometeor type falling out of a cloud deck, though through much of today, this has proven to just not be cold enough for snow to be our only precipitation type. Instead, we`ve had to deal with a mixture of poor quality snow and freezing drizzle, which is quite unusual for a lake effect event. Stronger mesoscale forcing along a convergence axis over Lake Michigan has fostered the development of a dominant precipitation band within the broader area of precipitation spilling inland. Precipitation within the heart of this band has been all snow, likely due to the stronger forcing fostering slightly deeper cloud depths, slightly colder in-cloud temperatures, and a greater degree of turbulence to support the activation of ice nuclei. This band remains flanked by a mixture of freezing drizzle and less efficient snowfall on both sides, and the expectation is for this to continue to be the case into tonight as this dominant band slides eastward into northwest Indiana. The overall degree of impacts from the main snow band and surrounding freezing drizzle remains somewhat of a question mark going into tonight. Regarding the snow... impacts (and snowfall accumulation amounts) would be maximized if the band were to stall over the same areas. However, the latest radar mosaic trends don`t look particularly promising for a dominant snow band sitting over the same locations and producing significant snowfall amounts, and the last couple of HRRR runs have also backed off from the `bullseye` 3+" amounts that it was outputting earlier in Lake and Porter counties in northwest Indiana. With low-level thermal profiles likely remaining too warm for the stratus deck to intersect the dendritic growth zone, snowflake quality will also likely remain poor through tonight, which may also deter snowfall totals from exceeding 3" even if the band were to stall out somewhat. Regarding the freezing drizzle... road impacts from this have appeared to be quite minimal over the past several hours as air and pavement temperatures have warmed closer to the freezing mark. Thermodynamic profiles will not change much tonight from what they have been today, so there is reason to believe that drizzle will continue in some capacity into tonight, but how expansive or persistent it will be remains uncertain. Temperatures will likely start to fall a bit after sunset, which may increase the odds that the drizzle starts freezing on pavement more effectively once again, but this is under the assumption that it will still be drizzling to begin with. There`s no straightforward way to handle winter headlines in borderline/high uncertainty setups like these, but with very little in the way of roadway impacts occurring the past several hours and low confidence in notable roadway impacts occurring tonight, felt that the best course of action at this time was to cancel the going Winter Weather Advisory for portions of the Chicago metro and instead put out a Special Weather Statement for locations where slippery travel from freezing drizzle and/or snow will remain a possibility late this afternoon into tonight. The evening shift will have to monitor observational trends closely and may ultimately need to hoist a short-fused Winter Weather Advisory if confidence in more notable roadway impacts occurring increases, but confidence in an advisory being needed for tonight was too low to warrant having one in effect right now. Any lingering lake effect precipitation in northwest Indiana should end by mid-morning tomorrow as the fetch over Lake Michigan becomes increasingly northwesterly. High temperatures tomorrow look to top out in the 20s across our forecast area. Ogorek Wednesday through Monday: A mid-level impulse over the high latitudes of central Canada is expected to dive southward across the western Great Lakes on Wednesday. While rather poor lower-level moisture should largely curtail the threat of any meaningful snow across much of the area, veering low-level flow over southern Lake Michigan is likely to setup the focus for another period of lake effect snow Wednesday into Wednesday night. The northwesterly fetch over the lake looks to favor the primary focus across northwestern IN and points eastward on Wednesday. However, while confidence is very low, we cannot rule out the possibility for some of this activity to try to work back westward towards the IL shore late Wednesday night into early Thursday before it dissipates. A surface ridge axis will pass across the area on Thursday, likely resulting in dry but continued cold conditions through the day. Thereafter, the next mid-level wave is expected to shift over the area Friday into Friday night as a secondary wave ejects northeastward from the southwestern CONUS. Forecast guidance continues to suggest these two waves will undergo phasing at some point late Friday into Friday night across the central CONUS, but differ on exactly when and where. The degree and timing of this phasing will ultimately influence the overall evolution of the system as it passes across our area late Friday. The current forecast favors a 30-50% chance for light snow for much of the area, with the highest chances currently along and southeast of I-55. This does not appear to be a big snow maker for our area, but some accumulating snow is certainly possible through Friday night. Temperatures through the period will remain seasonably cold, with highs mainly in the mid to upper 20s and lows in the single digits to the teens. KJB && .AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 541 PM CST Mon Jan 6 2025 Forecast concerns for the terminals... - Band of lake effect snow to impact northwest IN this evening and overnight resulting in some accumulation - MVFR ceilings to improve late this evening and overnight with VFR conditions expected for Tuesday A narrow band of lake effect snow has started to intensify as it pivots into northwest IN this evening. The lake effect snow is expected to result in sharp visibility reductions (around 1 SM) and snow accumulations generally in the 1-3 inch range as it traverses over GYY and nears VPZ towards midnight. While the band should gradually weaken as it moves east, guidance continues to show that at least some snow showers will persist across portions of northwest IN through the night (mainly east of GYY after midnight). Additionally, there also remains the potential for some freezing drizzle to occur on either side of the main lake effect band but cloud ice appears to be more abundant in IN think that main precipitation type should be snow. Elsewhere, expect the ongoing MVFR ceilings to gradually clear out this evening as drier air filters in from WI. However, some lingering lake effect clouds may result in periods of SCT to BKN MVFR ceilings through the night especially at GYY and possibly MDW. Otherwise, expect VFR conditions to prevail through the day on Tuesday with light northwest winds around 5-10 kts. Yack && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory until 9 AM CST Tuesday for the IL nearshore waters. Small Craft Advisory until 3 PM CST Tuesday for the IN nearshore waters. && $$ Visit us at weather.gov/chicago