Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/30/23


AREA FORECAST DISCUSSION
National Weather Service Hastings NE
526 PM CST Wed Nov 29 2023 ...Aviation Update... .DISCUSSION...(This evening through Wednesday) Issued at 419 PM CST Wed Nov 29 2023 -- KEY MESSAGES: * Turning colder again the next few days: After a Wednesday that ended up being even a few degrees milder than expected, things will take a turn for the colder (but not OVERLY cold) these next few days, with highs 30s-40s Thurs and 30s area-wide Fri. * Pesky and still-uncertain snow chances for at least parts of our coverage area (CWA) mainly Thurs night-Fri AM and again Sat: Although MOST of our CWA will surely remain snow-free Thurs night- Fri AM, especially our extreme southeast zones bear watching for a "sneaky" snow event. Saturday snow potential is even more uncertain, but is at least non-zero and bears watching. * A MAINLY dry forecast Sun-Wed: Our official forecast remains void of any "mentionable" (15+ percent) chances/PoPs at this time, but latest model data suggests that especially Monday could eventually need some chances for what would probably be light rain (not snow) for parts of the CWA. * Warming trend next week: Confidence is high that after "bottoming out" temp-wise Fri-Sat, that a gradual warming trend returns Sunday onward, with highs at least well into the 40s Sun-Tues and 50s to near 60 Wed. -- PRIMARY CHANGES WITH THIS "FORECAST PACKAGE" VERSUS THE PREVIOUS (OVERNIGHT) ONE: Although there were no truly "major" changes, the main ones include: 1) Some small snow chances (20%) were introduced to a few far southeastern counties for Friday daytime, BUT the better snow chances in that part of our CWA clearly looks to focus Thursday night. 2) High temps were nudged up slightly (only a few degrees at most) for Thursday and also for Sun-Tues (and quite possibly not enough for the latter). -- PRIMARY FORECAST CHALLENGES/UNCERTAINTIES: By far our main uncertainties center around the two aforementioned snow chances. 1) Will go into more detail in short-term-specific paragraphs below, but for being within 30-36 hours now, confidence in snow potential mainly for our far southeast CWA is unfortunately lower than one would hope. Quite frankly, our southeast corner (particularly Mitchell County KS area) could see anything from a nuisance dusting (currently our official forecast) up to perhaps a "sneaky" few inches (not in our current forecast, but within the realm of possibility). Fortunately, confidence IS HIGH that the vast majority of our CWA (especially Nebraska) should skate by snow-free. Given the potential for POSSIBLE accumulating snow especially in our extreme southeast, have opted to introduce a mention to our latest Hazardous Weather Outlook (HWOGID). 2) Unlike #1 above, we still have a few days to "figure out" Saturday`s snow potential (or lack thereof). Fortunately, the latest 18Z NAM has come in much less-snowy than its 12Z predecessor (which we were already considering an outlier anyway), but the ECMWF/GFS also imply that a pesky mix of light snow (and/or a rain/snow mix) could occur across parts of the CWA. Given this is still 3 days away and models depict varying solutions, opted to "force" at least a mention of possible sprinkles/flurries into the forecast for the ENTIRE CWA, to go along with formal 20% chances for precipitation in some areas. -- GENERAL OVERVIEW OF THE LARGE-SCALE WEATHER PATTERN THROUGH THE 7-DAY FORECAST: Starting things off, we reside "in between" main jet streams in a split-flow pattern, with the northern stream riding along the Canadian border, while the southern stream jet rides along the far southern fringes of the continental U.S. (CONUS). From Thursday night through Saturday, our various/uncertain precipitation chances will be tied to a series of shortwave troughs initially riding up into our region from the southwest, with the primary/larger scale trough axis finally passing east of our region by Sunday and putting us under northwesterly flow aloft. As mentioned above, both the ECMWF/GFS currently suggest that a quick-moving northwest-flow wave could bring a chance of at least light precip (probably rain) to especially our northern zones Monday, but this is far enough out in time/uncertain enough that our official forecast remains dry for now. By Tues-Wed, confidence is higher in our going dry forecast, as especially the ECMWF depicts a large-scale ridge building into the Central Plains (if this trends hold, our going high temp forecast for Wed mainly in the low-mid 50s could EASILY end up being 5+ degrees too cool). -- SHORTER TERM FORECAST DETAILS FOCUSED SOLELY ON THESE NEXT 36 HOURS (through late Thurs night/sunrise Fri): - Current/recent weather scene as of 330 PM: Kudos to preceding night shifter for nudging up high temps for today a bit, and not that ANYBODY complained, but highs still ended up "overachieving" our forecast by a few degrees, with most of the CWA on track to top out somewhere in the 56-61 range. Although these slightly-warmer-than-expected temps and low dewpoints drove relative humidity values down into low-mid 20s percent range in most areas, fortunately for fire weather concerns it was not overly windy, with most places this afternoon reporting southerly sustained speeds 10-15 MPH with occasional gusts to around 20 MPH. Although the first part of the day featured a bit more passing high cirrus, if anything this afternoon has featured more widespread sunshine than expected. In the big picture of the mid-upper levels, water vapor imagery and short term model data confirm that our area resides under broad, quasi-zonal (west-east) flow, well to the northeast of an upstream shortwave trough swinging through southern CA/northern Baja. - This evening-overnight: It will remain dry and mostly clear, with the main feature being the passage of a modest (not overly-intense) cold front. Prior the front`s arrival, this evening will feature fairly light (5-15 MPH) south-southwesterly breezes. Then, post-midnight the front will move in, turning winds to out of the north-northwest, but still not all that strong (still 5-15 MPH). By sunrise, this front will be through all but perhaps the far southeast fringes of our CWA. One thing that is not in our official forecast, but does bear watching, is the possibility for a narrow zone of at least patchy fog to develop ahead of this front very late tonight, primarily southeast of a Hebron-Osborne KS line. At least for now, the "fog signal" in most model data is weak enough that have opted to omit from official forecast. Temperature-wise, hourly trends could be a bit tricky, as many areas (especially north) will likely bottom out closer to midnight than sunrise, as the modest increase in post-frontal northerly breezes toward sunrise could easily stabilize temps or even cause them to rise slightly. Officially though, made minimal change to lows, with most areas aimed between 23-28 degrees. - Thursday daytime: High confidence that our entire CWA will remain dry through sunset. However, that`s where the similarities between today and tomorrow end, as Thursday will not only be 15-20 degrees cooler than today, but it will feel colder yet due to breezy north- northeast winds. There will also be more mid-high level cloud cover than today...not truly overcast, but legitimately more partly to mostly cloudy. In the mid-upper levels, the shortwave trough currently over the Desert Southwest will steadily track northeastward from southern AZ/NM around sunrise, to the TX Panhandle/western OK area by sunset, with any precipitation from this wave remaining "safely" to our south. Temperature-wise, actually nudged up highs 1-2 degrees from previous most areas, but still only ranging from upper 30s north-northwest to mid 40s south- southeast. North-northeast winds will be sustained 15-20 MPH/gusts 20-30 MPH. - Thursday evening-overnight: As already touched on above, while this should be a pretty straightforward and dry night for the vast majority of our CWA (high confidence), there is still quite a bit of uncertainty regarding snow (perhaps wintry mix?) potential for especially a few of our KS counties (particularly Mitchell/Osborne/Jewell). In the big picture, various models (NAM/GFS/ECMWF) are all in pretty good agreement swinging the heart of the mid-upper trough along a track from south central into eastern KS as the night wears on. However, models and their ensembles continue to waver slightly (really no more than 25-50 miles) on the EXACT placement of the far north-northwest fringes of the precipitation shield associated with this system. If it tracks just a bit farther south, perhaps Mitchell County gets a dusting of snow/sleet at most (perhaps starting briefly as cold rain), but otherwise zero impacts for our CWA. However, any northward nudge (as suggested by latest NAM and to a slightly lesser degree ECMWF) would bring at least light snow potential at least as far north as an Osborne- Hebron line, with perhaps as much as a few inches of snow to especially Mitchell County. At least for now, our official forecast leans toward the less-snow side of the possibilities, with less than 0.5" snow mainly in Mitchell County only, but even the latest 18Z HRRR has started to increase our snow potential (both amounts and areal coverage) into more of our southeast zones. As mentioned, this would likely be a quick transition from rain to snow (if it doesn`t start as snow), with perhaps brief sleet, but am not too concerned about freezing rain. While snow amounts remain a bit uncertain, confidence in TIMING is actually fairly high, with nearly all possible snow falling between 9 PM-6 AM. Briefly touching on other departments, low temps were nudged very slightly upward if anything, ranging from upper teens far west to low-mid 20s far east-southeast. IF snow does end up becoming an issue in our southeast, there could be some modest/minimal blowing snow issues, due to breezy (but not overly- strong) north-northeast winds sustained 10-15 MPH/gusting 20-25 MPH. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday) Issued at 522 PM CST Wed Nov 29 2023 VFR conditions are expected for the next 24 hours. Winds will switch from the south to the north by 12z and will remain out of the north to northeast through the rest of the period. Wind gusts are expected by the late morning hours. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ DISCUSSION...Pfannkuch AVIATION...Schuldt
Area Forecast Discussion
National Weather Service Goodland KS
427 PM MST Wed Nov 29 2023 .SHORT TERM...(This evening through Friday) Issued at 107 PM MST Wed Nov 29 2023 At the start of the short term period, the latest RAP analysis shows the CWA having a westerly flow aloft being underneath an upper air ridge with a trough over the western CONUS. Current satellite imagery and surface observations report dry conditions across the CWA with some scattered high clouds. Going through the rest of today, models show the flow over the CWA turning west-southwesterly by the evening hours with the western trough moving over AZ/NV/UT. At the surface, near critical to critical fire weather conditions continue along and west of KS-27 with south-southwesterly winds gusting up to around 25-30 kts and minimum RH values in the lower to middle teens. Winds look to slow down a bit in the evening ahead of a cold front approaching the region around midnight. Dry conditions look to continue through the rest of the day as well. Overnight lows are forecast to be in the upper teens to middle 20s range. On Thursday, forecast guidance shows the CWA gaining a southwesterly flow before the afternoon as the trough continues its eastward progress. This trough begins to weaken a bit during the evening and pass over the CWA over before another trough develops in the western CONUS. At the surface, the aforementioned cold front passes through the region in the morning allowing for some breezy northerly winds gusting up to around 25-30 kts in some locations behind the frontal passage. During the evening hours, a surface low looks to move northeast through OK into southeastern KS allowing for a slight chance of flurries in the southeastern quadrant of the CWA late in the day. With the cooler air moving into the region behind the cold front and cloud cover increasing, daytime highs on Tuesday are expected to be in the middle 30s to lower 40s followed by overnight lows in the lower to upper teens and minimum wind chills in the single digits. For Friday, models show the CWA having a southwesterly flow throughout the entire day with the newer trough moving eastward and having its axis over the Rockies late in the day. At the surface, mostly dry conditions are expected throughout the day as the surface low departs farther east. Models show the increased cloud continuing through the afternoon limiting daytime heating and keeping temperatures on the cooler side. The ECMWF`s latest run shows a slight chance for light snow in in the afternoon mainly in eastern CO, but opting to keep PoPs low for now as other models do not agree with this at the moment. Daytime highs expect to be in the middle 30s to the lower 40s with overnight lows in the middle to upper teens. .LONG TERM...(Saturday through Wednesday) Issued at 1208 PM MST Wed Nov 29 2023 Relatively benign conditions forecasted for the long term period. Some flurries/sprinkles are possible on Saturday. Greater uncertainty going into next week with the potential for shortwaves. Guidance is currently suggesting that an upper trough is forecasted to be present across the Eastern CONUS for most of the period with an upper ridge forecasted to begin building into the Western CONUS. This will keep the Tri-State area in northwest flow aloft which will make conditions a little more uncertain as smaller waves could move through the flow into the area until the ridge moves far enough east or another upper trough develops. For Saturday through Tuesday, conditions are likely to remain seasonable with near average temperatures (highs in the 40`s and 50`s) and a chance for a few flurries and sprinkles (mainly on Saturday). For Saturday, there are a few ensemble solutions showing chances for accumulating snow mainly for eastern portions of the area. However, with a wide range in guidance (greater uncertainty) and the current trend in guidance, I am not inclined to believe these solutions yet and have put sprinkles and flurries in the forecast for now (mainly favoring Northwest Kansas). Some upper level moisture and cooler temperatures are likely over the area Saturday, but the near surface air may be too dry for any accumulations. For Wednesday and beyond, there is some uncertainty as to how much influence the trough will have over the area. Currently going with the trend of the ridge moving over the area Wed/Thur which would keep conditions dry and warmer (highs near 60 or warmer). If a trough moves in faster or deamplifies the ridge, seasonable temperatures and some chances for precipitation would be more likely for the mid part of the week. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 418 PM MST Wed Nov 29 2023 VFR conditions will prevail for both KGLD and KMCK through the TAF period. Winds will remain fairly light through the first half of the night as a cold front moves through the area. Wind direction will slowly shift front the south to the north-northwest during the first 6-9 hours of the period. Winds are expected to pick up at KGLD near 9Z with gusts around 20 kts being possible through the rest of the period. KMCK will see similar wind speeds starting around 16Z. More clouds are expected to move into the region near 16-18Z and will slowly begin lowering cloud bases, but no impacts to categories are expected before 0Z Thursday evening. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...076 LONG TERM...KAK AVIATION...CA
Area Forecast Discussion
National Weather Service Northern Indiana
654 PM EST Wed Nov 29 2023 .SYNOPSIS... Issued at 219 PM EST Wed Nov 29 2023 Highs will be in the mid 40s to low 50s Thursday, before a cold front sweeps through late Thursday night into Friday bringing cooler temperatures and widespread rain chances. The weekend will be seasonable with additional rain showers. Scattered rain (and maybe snow) shower chances persist into early to mid next week. && .SHORT TERM...(This Evening through Thursday) Issued at 219 PM EST Wed Nov 29 2023 One more cold night is in store with lows in the mid 20s. With winds slightly elevated up to 10-15 mph early Thursday morning, wind chills will be in the upper teens. The cold is short lived as highs climb above average tomorrow. WAA and southwesterly winds will transport increased moisture and warmer temperatures northward from the Gulf. As a result, temperatures quickly warm throughout the morning and early afternoon, with highs in the upper 40s to low 50s. As an area of low pressure advances northeast out of Oklahoma, rain chances increase late Thursday night and especially into Friday morning. Following in the footsteps of the previous forecasters, the forecast continues to be tweaked to delay the onset of the most widespread rain. Between 00Z to 12Z Friday, rain should remain light and scattered, before increasing in coverage and becoming more widespread between 12-18Z Friday as the low approaches. Many of the short range models, particularly the HRRR and NAM, show this trend as well. Forcing is rather weak with the system, as convection develops along the WAA axis. QPF with this system should yield around half to three quarters of an inch by Saturday morning. && .LONG TERM...(Thursday Night through Wednesday) Issued at 219 PM EST Wed Nov 29 2023 Additional precipitation chances persist through the long term forecast range as a series of 500 mb shortwaves pass through the CWA. During the day Saturday, it will be dry. However, as the backside of the low moves through on Saturday afternoon, another wave of precipitation develops along a 500 mb shortwave that moves in from the southwest. We will see mostly rain late Saturday night into Sunday, as temperatures will be above freezing in the upper 30s, but some snowflakes could mix in at times. Some snow showers (perhaps lake effect in nature) will be possible as well Tuesday and Wednesday. && .AVIATION...(For the 00Z TAFS through 00Z Thursday Evening) Issued at 653 PM EST Wed Nov 29 2023 Quiet aviation weather this cycle, but conditions are expected to deteriorate just beyond this forecast valid period into Thursday night. A split flow type pattern across western CONUS will yield a very progressive northern stream that will allow next broad upper trough to drive a cold front across southern Great Lakes Thursday night. Southwest flow will increase in advance of this cold front later tonight into Thursday, with southwest gusts of 20 to 25 knots once again late Thursday morning into mid afternoon Thursday. Better low level moisture return will bypass the terminals to the northwest through late Thursday afternoon which will keep VFR conditions in place through 00Z Friday. It still appears as though a very narrow temporal window for marginal LLWS in the 12Z-16Z timeframe Thursday morning before better low level mixing occurs, and have maintained this mention with the 00Z TAFs. An axis of better moisture transport should begin to lift across west central IN by 00Z, with rain expected to overspread the terminals during the mid to late evening on Thursday. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...Small Craft Advisory from 9 AM to 4 PM EST Thursday for LMZ043. && $$ SYNOPSIS...Johnson SHORT TERM...Johnson LONG TERM...Johnson AVIATION...Marsili Visit us at www.weather.gov/iwx Follow us on Facebook...Twitter...and YouTube at: www.facebook.com/NWSNorthernIndiana www.twitter.com/nwsiwx www.youtube.com/NWSNorthernIndiana
Extended Forecast Discussion...

Looking into the extended, the cool blast behind the above mentioned clipper will be rather short lived as a warmer pattern is likely to redevelop across much of the CONUS. Much of this will be driven by the MJO which will be heading into phases 3/4/5 during this period. While the NAO and AO are forecast to remain negative, the MJO and the expected +EPO pattern will likely help sustain the warm pattern. Updated signal analysis from last week suggests the next signal passage coming in the 12/10-12 time frame. Given the MJO and teleconnection pattern the main storm track looks to be from the southern Plains into the Great Lakes. Another bout of moderate rainfall looks likely here with another possible cool down behind that. Longer range data continues to be in pretty good agreement with a colder pattern developing toward the late part of December as those models suggest that a ridge will develop across the western US with deeper troughing setting up across the east. The timing to this pattern remains uncertain due to uncertainties on how large the upcoming MJO pulse will be. While the ensemble mean from the GFS and Euro push the MJO into phases 4/5 and then collapse it rather quickly, there are some ensemble members that have larger orbits through phases 4/5/6 and do not get over to phase 7/8 until late month. Additionally, the Pacific Jet will play a major role in the possible pattern change for late month. As of this writing, the Pacific Jet is forecast to remain extended and strong through the month which will greatly diminish the probability of a west coast ridge popping up. On the other hand, if the Pacific Jet were to retract a bit more to the west, then the possibilities of the west coast ridge developing will increase. && .Aviation...(00Z TAF Issuance) Issued at 623 PM EST Wed Nov 29 2023 Impacts/Confidence: - High confidence in gusty SW winds on Thursday - Medium confidence in LLWS at HNB and SDF tonight Discussion...VFR conditions will continue through this TAF cycle at all terminals. As stated in previous discussions, an enhancement of the low-level wind field is expected tonight as a disturbance moves across the northern portion of the Great Lakes. Winds at 925-mb will be around 30-35 knots from the SSW while surface flow will be weak (around 5-6 knots) and from the south. Therefore, the combination of speed and directional shear will warrant the inclusion of a LLWS group for HNB and SDF from the second half of tonight to the first morning hours. As for model guidance, the RAP, NAM and to a lesser extent the HRRR support the such inclusion. For tomorrow, still anticipating gusty (18-22 knots) SW winds from 15 to 22Z with calmer winds by sunset. The cloud deck will stay in the mid to upper levels with increasing low-level, VFR clouds after sunset. Extended Outlook...There is a non-zero chance of MVFR ceilings and another LLWS event Thursday night. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...ALL Short Term...CSG Long Term...MJ Aviation...ALL
Area Forecast Discussion
National Weather Service Pocatello ID
248 PM MST Wed Nov 29 2023 .SHORT TERM...Tonight and Thursday Afternoon visible satellite imagery shows an ample snowpack in place across much of the Snake Plain and especially into the Magic Valley from recent winter storms. In addition to that, just a few mid/high clouds streaking across the region this afternoon as we enjoy ample sunshine. Despite the sun, temperatures are chilly though with highs this afternoon in the 20s and 30s regionwide. The weather pattern remains stagnant with the only concern tonight being for areas of fog, once again. Increasing cloud cover tonight, as we begin to feel the effects of the next weather system, could lessen this potential somewhat. Clouds will be more commonplace tomorrow with precip chances sneaking into the central mountains by around sunset tomorrow and overspreading the rest of the region as we approach the daylight hours Friday AM. Until then, expect daytime temps to remain on the cold side of normal by around 10 degrees or so. McKaughan .LONG TERM...Friday through Wednesday Our quiet weather under high pressure comes to an end as we close out the week and head into the weekend. On Friday and Saturday, we get a bit of a 1-2 punch as two shortwave troughs moves through Idaho. By breaking into Friday and the weekend, we can see that Friday, while it will bring snow to the area, is the "weaker" punch of the two. Snow totals for Friday will be about 1 to 2 inches in the eastern Magic Valley and Snake Plain and about 3 to 5 inches up in the mountains. Probabilistic data from the NBM shows about a 40 to 50 percent chance of at least an inch in the Magic Valley and Snake Plain by midnight Friday night versus about a 20 percent chance of at least 2 inches of snow. For the mountains, it`s about a 40 to 60 percent chance of at least 4 inches of snow versus about a 30 percent chance of at least 6 inches of snow. The wind will also be increasing on Friday with gusts approaching 30 to 35 mph, with about a 20 percent chance of reaching 40 mph in the eastern Magic Valley and Snake Plain. At this point, we are holding off on issuing any headlines, as snow totals themselves for Friday look borderline advisory levels. We will take a closer look at it tonight/tomorrow and make the final call. The next wave of moisture that arrives for the weekend is able to tap into some juicier Pacific moisture and cold air is still in place through Saturday and into Sunday. Our 48 hour snow totals from Saturday morning to Monday morning will be a bit higher. In the eastern Magic Valley and Snake Plain we`re looking at about a 30 to 50 percent chance of at least 2 inches of snow and about a 10 to 20 percent chance of at least 4 inches of snow. In the mountains (generally above 7500 ft), it`s a 50 to 70 percent chance of 12 inches of snow and a 20 to 40 percent chance at least 18 inches of snow. Totals on the peaks will likely be higher at the NBM shows about a 20 percent chance of 24 inches of snow above 8500 ft. The wind will be cranking on Saturday with gusts between 30 to 40 mph in the eastern Magic Valley, Snake Plain, and Arco Desert. The NBM is showing a 50 to 70 percent chance of gusts at least 40 mph from Burley up to Rexburg and about a 20 to 30 percent chance of gusts around 45 mph in the same area. Sunday and Monday will still be breezy with gusts around 20 to 30 mph and snow will slowly taper off throughout Monday with most of us dry by Monday night/Tuesday morning as high pressure slowly begins to build in over the area once again. We will likely need some winter weather headlines for at least Saturday in the next day or so. AMM && .AVIATION...18Z Wednesday through 18Z Thursday VFR conditions are in store for the rest of the afternoon and this evening. However, patchy dense fog returns to the area once again tonight/Thursday morning. It`s most likely near BYI and PIH where the NBM is already pinging a 20 to 30 percent chance of CIGs less than 500 ft. The latest NAM and HRRR data is starting to suggest about a 30 percent chance that fog could also make it up to IDA. We will need to keep an eye on that as we go through the rest of today as it could reduce VIS and CIGs to IFR conditions at IDA if the fog makes it to the terminal. So, that could be a change to watch for in the next TAF issuance. Cloud cover will be on the increase later today and through Thursday as our next system begins to move into the area. Winds remain light today and most of tomorrow, but that will change on Friday along with the arrival of snow. AMM && .PIH WATCHES/WARNINGS/ADVISORIES... Air Stagnation Advisory until noon MST Thursday for IDZ059-061- 065. && $$