Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/18/22

If you`ve made it this far into the forecast discussion and are
hoping for more engaging forecast details, you might be a tad
disappointed, as we`re in for a rather uneventful few days on the heels of today`s snow. That said, it`s certainly worth emphasizing the anomalously cold air mass that will linger over Colorado as we enter the weekend. Friday night will be very cold once again with clear skies and remaining snow cover keeping lows in the single digits for the lower elevations. Cold air pooling will likely be significant in the high mountain valleys, particularly Middle and North Park where snow cover will be more likely. Have lowered nighttime temperatures there, where the thermometer could drop into the negative teens. We`ll begin a gradual transition to milder and more seasonal conditions over the weekend and into Monday under weak ridging building in from our west and mostly sunny skies. Temperatures will steady early next week but we`ll remain dry at least through Tuesday. Details become fuzzy by the middle of next week. Deterministic guidance varies in its solutions, ranging from a closed low over Arizona to much more progressive, weak shortwave over Colorado. Ensembles are not at all bullish on precipitation chances, which would favor the mountains if anything. A handful of solutions produce some measurable snow east of the Front Range but really the signals are quite meager at this point. Just chance PoPs currently for Wed-Thu period, primarily for the mountains. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 435 PM MST Thu Nov 17 2022 ILS and MVFR/IFR conditions will continue through the evening and overnight. The early afternoon lull is now over, with snow quickly developing and intensifying across the terminal sites over the past hour or so. Ceilings and visibilities should fall a little lower this evening as heavier snow moves in. There could be some brief LIFR conditions depending on where the heavier bands develop tonight. Snow will gradually wind down tomorrow morning. Ceilings should rise through the morning hours with VFR conditions expected a little before noon. Winds will remain fairly light out of the northeast tonight and will become more variable tomorrow. && .BOU WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 9 AM MST Friday for COZ031-033>036- 040-041-043-045. Winter Storm Warning until 9 AM MST Friday for COZ038-039. && $$ UPDATE...Hiris SHORT TERM...Danielson LONG TERM...Rodriguez AVIATION...Hiris
Area Forecast Discussion
National Weather Service Lincoln IL
712 PM CST Thu Nov 17 2022 .SYNOPSIS... Issued at 212 PM CST Thu Nov 17 2022 A cold front will move across the region this afternoon through tonight bringing a few widely scattered snow showers to central Illinois. Temps are expected to fall to around 20 degrees tonight behind the front, then will only warm into the mid to upper 20s north of I-70 Friday. South of I-70 is expected to reach the lower 30s. Overnight lows are expected to dip into the teens and single digits Friday night and Saturday night. && .UPDATE... Issued at 712 PM CST Thu Nov 17 2022 A cold front was pushing east of the I-55 corridor early this evening. Water vapor imagery indicated a shortwave moving into northwest IA. Lift ahead of the wave combined with steeper lapse rates behind the front to produce scattered rain and snow showers over the northern CWA. As temperatures cool below freezing a few slick spots will be possible, especially where briefly heavier snow showers put down a light accumulation, likely a half inch or less. IR satellite data showed cloud cover extending northwest through central and northern IA, thus mostly cloudy skies persisting overnight will keep lows mainly in the 20s with upper teens where any clear pockets develop. After a lull in the winds along the frontal zone, brisk west-northwest winds are already gusting 20-30 mph west of the IL River and these will spread east over the remainder of the CWA tonight. && .SHORT TERM...(This evening through Friday) ISSUED AT 212 PM CST Thu Nov 17 2022 This afternoon, low pressure is in place across the Great Lakes resulting in cyclonic flow and cloudiness over much of the Midwest. A cold front is currently moving across the Illinois River Valley and will continue to push across central Illinois through the evening. In its wake, steepening low level lapse rates will allow weak instability to develop which will support some isolated to widely scattered snow showers. Overall forcing remains weak which will help keep coverage low, but given the depth of the steep lapse rates which result in equilibrium levels near the top of the snow growth zone, an isolated moderate or heavy snow shower couldn`t be ruled out. HREF ensemble max snow totals do show the potential for a couple narrow, isolated swaths of around an inch of snow which seems reasonable if instability is realized. Most of the area should only see flurries or a dusting of snow, but within these isolated stronger showers, visibility will be greatly impacted and quickly go down to a quarter mile or less within a short period of time. RAP snow squall parameter values top out between 3-4 roughly along and north of a Havana to Paris line further highlighting the potential for some heavier bursts of snow. By Friday morning, mid level height rises begin to overspread the region while at the surface, high pressure spreads southeast from the northern High Plains across the central Great Plains and to the middle Mississippi Valley. This combination of factors will keep central Illinois dry through the day Friday, albeit cold with highs generally in the mid to upper 20s north of I-70 and lower 30s south. .LONG TERM...(Friday night through Thursday) ISSUED AT 212 PM CST Thu Nov 17 2022 Deep, closed upper low remains over Hudson Bay to start the day Saturday but a strong shortwave rounding the base of the trough over the Great Lakes will finally help nudge the system to our east as it lifts to New England Sunday. Temperatures will start off quite cold Saturday morning, in the teens across all of central Illinois, and will only warm into the upper 20s north of the Illinois River and 30s south. Meanwhile, surface high will build over the mid Mississippi River Valley Saturday night into Sunday morning allowing skies to clear as cyclonic flow finally exits the region. Favorable radiational cooling conditions will be in place and some locations could dip into the single digits Sunday morning, with lows in the teens elsewhere. The surface ridge axis will shift to the upper Ohio River Valley by late Sunday with southwest flow overspreading portions of the Midwest in its wake. This will allow temperatures to moderate through the first half of next week. 40s return to the forecast Monday followed by 50s Tuesday and Wednesday. Attention turns back to the west Thursday as a strong shortwave emanating from the Pacific Northwest digs across the Great Plains to the mid Mississippi Valley. A surface low develops in response and tracks across the region Thursday and Friday. At this time there remain rather significant differences in timing and placement of this system which leaves forecast details uncertain. NBM P-type probs favors rain with this system, but do at times show the potential for snow or a wintry mix. Meanwhile, the ECMWF/EPS hints at more of an alberta Clipper like setup favoring snow. This system will bear watching in the coming days as details come into better focus. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 523 PM CST Thu Nov 17 2022 Scattered snow showers will affect the terminals this evening, most concentrated at KPIA-KBMI where tempo MVFR ceilings and visibilities are forecast. There is a low chance that IFR visibility will be seen in the heavier showers, as has been noted in a couple obs out of eastern IA. Outside of the showers VFR ceilings will lower to MVFR from 05-07z at KPIA-KBMI-KCMI. There is a low chance that these ceilings will affect KSPI-KDEC but are not included in this set of TAFs. The MVFR ceilings are forecast to persist through 17-18z, then go VFR through afternoon. Winds will be persistent from the west at 10-20 kt. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...25 SYNOPSIS...Deubelbeiss SHORT TERM...Deubelbeiss LONG TERM...Deubelbeiss AVIATION...25
Area Forecast Discussion
National Weather Service Louisville KY
944 PM EST Thu Nov 17 2022 .Forecast Update... Issued at 925 PM EST Thu Nov 17 2022 Cold front approaching the I-70 corridor this evening, but its bark on radar is worse than its bite in sfc obs as there is still a fair amount of precip evaporating before it reaches the ground. Still looking for this boundary to press southward through the night, and push through southern Indiana and Kentucky on Friday morning. Min temps are a little tricky overnight as we could still drop a couple more degrees, but we should flatline by about midnight as clouds increase and the boundary layer becomes more mixy. Temps should level off in the mid/upper 20s for most. Models have not had a good handle on snow coverage with any of the systems this week, so the precip forecast is fairly low-confidence. Will stick with a 20 POP for isolated snow showers, with the best chances near the I-64 corridor from Louisville to east of Lexington, and perhaps another max W/SW of Elizabethtown as the front lights up over western Kentucky. No major changes to the previous forecast, but any more focused areas of precip will bear watching overnight. && .Short Term...(This evening through Friday) Issued at 225 PM EST Thu Nov 17 2022 Low level clouds over southern Indiana and north central Kentucky continue to erode late this afternoon. Expect skies to become only partly cloudy by this evening before more clouds build in after midnight ahead of an approaching cold front. Temperatures look to drop into the lower 20s late tonight. A cold front will begin approaching from the northwest late tonight and likely push into the region during the early morning hours tomorrow. Some models indicate we could see a narrow band of light snow flurries or showers develop ahead of the front. The HRRR has been most consistent with this light snow tomorrow morning while other short range models keep us dry. In this type of environment, can`t rule out some isolated snow showers dropping a quick dusting of snow ahead of the front so did continue isolated light snow shower mention for tomorrow morning. Skies will become partly cloudy tomorrow afternoon with breezy westerly winds behind the front. High temps look to stay in the 30s to around 40. .Long Term...(Friday night through Thursday) Issued at 154 PM EST Thu Nov 17 2022 Very Cold Weekend... The nose of a dome of Canadian high pressure will poke into the Ohio and Tennessee Valleys Friday night and Saturday morning, taking temperatures down into the teens for many with mostly clear skies and nearly calm winds. This will be followed by a quick cold frontal passage Saturday evening, but the boundary will be weakening and will have very little moisture with it (PWAT 0.18"), so no precipitation will accompany its passage. However, behind the front a new, stronger dome of high pressure will move into the region and supply us with temperatures Sunday morning a few degrees colder than what we will have seen Saturday morning, with everyone dropping into the 10-19 degree range (still above record lows). Holiday Week... Dry weather will continue at least through mid-week as that surface high settles into the southeast United States and deflects an approaching Monday cold front off to our north, passing through the upper Great Lakes. By the holiday a cut-off 5H low will be in the vicinity of the Gulf of California while a northern upper trough tries to dive southeast from the Prairie Provinces. This is far out in the forecast and the models will struggle with how these systems interact. As of now, the deterministic runs have slowed down the advancement of precipitation, though there are enough individual ensemble members to support keeping low PoPs in the forecast for Turkey Day. Temperatures will moderate as the week goes along, so by the time Thanksgiving arrives we should have daytime temperatures in the 50s, and for now we just have plain rain in the forecast. Thunder chances will hold off well to our southwest. && .Aviation...(00Z TAF Issuance) Issued at 625 PM EST Thu Nov 17 2022 IMPACTS: Potential for snow showers early Fri morning at SDF and LEX CONFIDENCE: Low to moderate Expect mainly VFR conditions through the valid TAF period. Wind direction will back to SW this evening ahead of a weak cold front. There is some hint that we could squeeze out a few snow showers at SDF and LEX, mainly from the pre-dawn hours through mid-morning. Models have not handled this well all week, so will go cautiously forward with a PROB30 to highlight the potential impact, mainly on ground operations. Prevailing vis even in snow showers should be MVFR, with cigs remaining VFR. Winds will veer to due west with the fropa, with afternoon gusts just either side of 20 kt. The low-end VFR strato-cu deck in the morning should scatter out as the afternoon progresses. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...RAS Short Term...AMS Long Term...13 Aviation...RAS
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
842 PM CST Thu Nov 17 2022 .UPDATE... Issued at 820 PM CST Thu Nov 17 2022 Current surface observations show that the cold front is just south of the I-44 corridor in Missouri and I-70 corridor in Illinois. As discussed earlier, the signal for low-level frontogenesis was trending weaker, and that trend has so far been verifying per recent RAP analysis. Additionally, soundings across the area based on the RAP analysis show only shallow layers of saturation in the lower atmosphere primarily outside of the dendritic growth zone, leading to a lack of ice crystals aloft. Therefore, our confidence in snowfall continues to decrease. I still have a low chance of snow across portions of southeastern Missouri and southwestern Illinois over the next couple of hours to account for the weak low-level frontogenesis there, but I feel the worst case scenario is a dusting on grassy and elevated surfaces in those parts of the CWA. Spotty sprinkles/flurries are more likely this evening into the early overnight hours before drier, post-frontal air moves in and drys out the lower atmosphere. Elmore && .SHORT TERM... (Through Late Friday Night) Issued at 228 PM CST Thu Nov 17 2022 Deep, cyclonic flow will persist across the Midwest through Friday and beyond as time-mean upper-level longwave troughing remains over the Great Lakes. In a continued parade of mid-level shortwave troughs navigating the cyclonic flow, two shortwave troughs will traverse the Midwest this afternoon and overnight. The first shortwave trough has forced a cold front southeastward into the CWA that has reached northeastern MO and west-central IL this afternoon and will continue through the rest of the CWA through the evening. Passage with the onset of strong low-level CAA and some stratocumulus with scattered flurries, or initially sprinkles. Beside flurries, a frontogenetical band of light snow still appears possible from south- central MO to southwestern IL behind the front as well. But latest short-range model guidance has trended toward weaker and less organized low-level frontogenesis translating to lighter associated QPF, generally 0.01" or less. The latest HREF LPMM still has a swath of just over 0.01" across portions of southeastern MO and southwestern IL but is attributed nearly entirely to its time-lagged members. Therefore, the current expectation is for even the highest snowfall rates to be too light for anything more than a dusting accumulating on grassy and untreated surfaces. Any flurries should exit the CWA by Friday morning, along with a potential brief break in stratocumulus for mainly the southern two thirds of the CWA; however, some expansion back southward appears possible through the morning. Strong low-level CAA from overnight is anticipated to place an anomalously cold airmass across the Midwest with 850-hPa temps settling in the low-negative teens to mid- negative teens C. These remarkable 850-hPa temps are between the minimum and 1st climatological percentile. As a result, Friday`s high temps should only warm into the mid-20s to mid-30s F and near KUIN and KCOU`s daily record minimum high temps, especially if stratocumulus is more prevalent. Low-level WAA initiating Friday night should begin releasing the CWA from the clutches of this cold airmass. In fact, low temps Friday night in the mid-teens to low-20s F may occur during the first half of the night as the WAA strengthen and surface pressure gradient tightens beneath mostly clear skies. Pfahler .LONG TERM... (Saturday through Next Thursday) Issued at 228 PM CST Thu Nov 17 2022 Deep, cyclonic flow will continue through Saturday with the passage of another mid-level shortwave trough and southeastward-advancing cold front. Timing of this cold front will be crucial in determining Saturday`s high temps, marking the quick transition from low-level WAA to another shot of CAA. Most model guidance has the front bi- secting the CWA around midday, leading to a large areal spread in high temps from the upper 20s F in northeastern MO to the mid-40s in southeastern MO. Moisture is forecast to be more limited with this cold front than its predecessor, precluding precip but a few flurries cannot be ruled out. The CWA should be spared the core of this post-frontal cold airmass, but conditions favorable for efficient radiational cooling (i.e., mostly clear skies and light/calm winds from a nearby surface anticyclone) could still allow low temps Saturday night to fall into the teens F CWA-wide. These temps will likely come short to daily records, though. Sunday into Monday, global model guidance advertise the time-mean upper-level longwave troughing becoming more progressive and finally departing the Great Lakes, leading to more zonal flow across much of the central CONUS. Large-scale subsidence from height rises behind this longwave troughing is anticipated to quickly translate Saturday night`s surface anticyclone eastward into the eastern CONUS. The resulting flow pattern will favor low-level southwesterly or southerly flow and WAA, with temps moderating to near average on Monday. There is consensus that the first half of the week will also remain dry with only a compact mid-level shortwave trough passing south of the CWA late Monday into Tuesday. The next opportunity for precip across the CWA will be around Thanksgiving Day, but global model guidance continue to depict vastly different evolutions between upper-level troughs in the northern stream and those in the southern stream with little run-to- run consistency. The leading WPC Cluster Analysis clusters (75%) both contain dominant northern stream troughing over the central CONUS. The other cluster has more dominant southern stream troughing hanging back across the Four Corners Region. The nature and track of any trough or troughs will have large implications for the exact sensible weather across the CWA during this timeframe, which is highly uncertain. Pfahler && .AVIATION... (For the 00z TAFs through 00z Friday Evening) Issued at 527 PM CST Thu Nov 17 2022 A cold front is currently moving southward through the region, having already passed over KUIN, KCOU, and KJEF and currently in the vicinity of KSUS, KSTL, and KCPS. The front is expected to be moving through the latter three terminals at the start of the period, with winds quickly shifting to out of the northwest with its passage. Additionally with the passage of the front is the chance for a quick hit of light rain or snow. Confidence is high that this precipitation will be light enough to not impact visibilities, and snow that falls will at worse provide a dusting on grassy and elevated surfaces near these terminals given above freezing near-surface and ground temperatures. Flurries can be expected around KUIN through this evening given deeper moisture residing near that terminal. Drier air will move into the region behind the front through tonight, eroding much of the lower cloud cover from over the terminals. The exception to this is KUIN, where confidence remains high that a brief period of MVFR ceilings will occur Friday morning. These lower ceilings will remain well to the north of the other local terminals, including KSTL. Elmore && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Phoenix AZ
456 PM MST Thu Nov 17 2022 .SYNOPSIS... Cool and dry conditions will prevail through at least the first half of next week with only occasional periods of high clouds tonight through Friday afternoon and again early next week. A weak and dry weather system passing through the region on Saturday will bring another round of breezy winds, particularly across portions of southeastern California. Temperatures will continue to run 5 to 10 degrees below normal with lower desert highs mostly in the upper 60s and lower 70s. A warming trend is then anticipated by late next week as high pressure builds across the intermountain West. && .DISCUSSION... Latest water vapor imagery and RAP streamline analysis reveal a dry northwesterly flow predominating across the Desert Southwest. This is again resulting in sunny skies along with below normal temperatures and dewpoints in the teens and twenties. Model clusters show little difference through the weekend and indicate another shortwave trough will drop southward out of the Rockies and towards Arizona Friday and Friday night. PWATs remain well below normal and there is no chance of rain associated with the trough. Instead the main impact will be another period of breezy/windy conditions, particularly Saturday across southeastern California and further east across the foothills of Pinal County Sunday morning. However, while ECMWF EFI values suggest gusty conditions are likely, peak gusts will likely remain well below Wind Advisory criteria. && .PREVIOUS DISCUSSION... The weather pattern will begin to change by early next week as the ridge over the Western U.S. weakens enough to start to allow for more progressive and stronger weather systems to move across the Northern Pacific, eventually reaching the Pacific Northwest. This will likely bring decent precip across the Pacific Northwest, but model ensembles show dry westerly flow persisting across our region through the first half of next week. NBM temperature guidance for the first half of next week does show a very slight uptrend in temperatures, but highs will still mostly stay in the lower 70s. For the latter half of next week, a stronger ridge is favored to move out of the Central Pacific, potentially reaching our region around next Friday. If this were to happen, we could see highs approaching 80 degrees over the western deserts to the mid to upper 70s in the Phoenix area. && .AVIATION...Updated 2356Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Very light winds will prevail through the TAF period, with speeds generally aob 7 kts. Periods of variability are likely with these light winds. Otherwise, directions will favor typical diurnal trends. A late and brief W to WNW shift is anticipate this evening before returning to E tonight. High clouds will increase heading through the overnight hours with perhaps some isolated light virga developing above 15-20 kft across the area. Skies then clear up by midday Friday followed by another round of high clouds Friday evening. Southeast California/Southwest Arizona including KIPL and KBLH: Winds through the next 24 hours will mostly remain on the light side (aob 8 kts) with periods of light and variable winds at times. Otherwise, high clouds will increase through this evening with perhaps some light virga developing above 15-20 kft across the area. Skies clear after sunrise Friday. && .FIRE WEATHER... The weather pattern through the first half of next week will heavily favor cooler than normal and dry conditions over the region. Winds through the weekend will at times be breezy with gusts of 20-25 mph likely, favoring southeast California and the Arizona high terrain. The strongest winds are likely to be across southeast California Friday night through Saturday afternoon when localized gusts to 30-35 mph may be possible. Moisture levels will remain quite low through the period with daily MinRHs in the teens across the western districts to 15-25% across the eastern districts. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Hirsch PREVIOUS DISCUSSION...Kuhlman AVIATION...Benedict FIRE WEATHER...Kuhlman