Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/08/23

Area Forecast Discussion
National Weather Service Denver/Boulder CO
826 PM MST Sat Jan 7 2023 .UPDATE... Issued at 820 PM MST Sat Jan 7 2023 Quiet evening today under mostly clear skies, except in the high country where the bank of high clouds is beginning to make its way overhead. Those clouds will continue marching east but are doing so rather slowly. With light winds in place a few patches of fog currently over NE/KS, have increased the patchy fog coverage overnight mainly for the S. Platte River Valley. Otherwise, no changes to the forecast. && .SHORT TERM...(This evening through Sunday) Issued at 244 PM MST Sat Jan 7 2023 We`re settling in for a quiet night as the remnants of clouds from last night`s shortwave drift out of the northeast corner. High clouds will start to spread in over the mountains this evening, and onto the plains by the early morning hours. This should allow for some drop in temperature this evening, but then restrain the cooling later tonight. The main question for tonight is the extent of fog, as there`s been quite a bit of evaporation/sublimation from the snowpack over northeastern Colorado. It will be a battle between the cooling, the clouds, and a tendency for 10 knot south to southwest winds in the boundary layer. For now, we`ve just got a few patches of fog forecast, but we could wind up having quite a bit more if the clouds are late and the wind is light enough. On Sunday, we should have quite a bit of high level cloud cover, which together with the remaining snow will limit our warming to a few degrees over today`s highs. The exception will be in the areas with more wind, mainly North and South Parks and the east slopes of the Front Range down into the foothills. These areas will be warmer and may also have very dry air descending. The HRRR is showing humidities down around 10 percent in South Park in the afternoon. The current forecast has all this pretty well in hand and the minor adjustments made this morning look sufficient. .LONG TERM...(Sunday night through Saturday) Issued at 244 PM MST Sat Jan 7 2023 Upper level high pressure over the Rocky Mountain Region will bring mostly dry weather and above normal temperatures to the forecast area from Sunday night through Tuesday. The mountains could see a chance of snow on Tuesday as increased moisture moves into Colorado from the west. Wednesday into Thursday morning, a Pacific storm system will move across the state with snow in the mountains and a chance of rain and snow on the plains. The consensus of the models is that the 500 MB low will close off over Southeastern Colorado by 00Z Thursday and then move eastward into South Central Kansas/North Central Oklahoma by midnight Wednesday night. As for impacts across the forecast area, they are as follows: The mountains should see mainly light snow with this event due to poor orographic flow. However, the combination of ample moisture and QG lift should help somewhat. Overall, snowfall amounts are expected to range between 1 and 6 inches with this event. For the plains, impacts seem somewhat limited at this time due to the lack of cold air, the quick movement of the storm and the surface low pressure being displaced too far to the south over Oklahoma. As a result, the strength of the winds on the back side of the low appear to be quite weak with an unimpressive upslope flow east of the mountains. Therefore, most of the precipitation could be rain with mainly light snow accumulation by Thursday morning. The exception to this may be across the Palmer Divide which is under better QG lift and due to its higher elevation will be colder. Therefore, portions of the Palmer Divide have the potential to see a period of heavier snow late Wednesday afternoon and evening which could result in hazardous travel. There is still quite a bit of uncertainty with this storm and it bears watching for any changes in its track. Dry and warmer weather is expected across North Central and Northeastern Colorado Friday into the weekend as a large upper level ridge of high pressure builds over the Rocky Mountain Region. && .AVIATION...(For the 06Z TAFS through 06Z Sunday night) Issued at 820 PM MST Sat Jan 7 2023 VFR through Sunday with light winds. Small possibility of patchy fog overnight in the plains, but unlikely to impact KDEN. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Rodriguez SHORT TERM...Gimmestad LONG TERM...jk AVIATION...Rodriguez
Area Forecast Discussion
National Weather Service Duluth MN
539 PM CST Sat Jan 7 2023 .DISCUSSION...(This evening through Friday) Issued at 258 PM CST Sat Jan 7 2023 A relatively quiet period is expected through the next week with above normal temperatures. The fog and stratus has burned off for most this afternoon with some stratus lingering in the Arrowhead and parts of northern Wisconsin. The core of an area of high pressure will be south of the Northland tonight and the pressure gradient will strengthen. We expect some fog again tonight but we don`t expect it to be widespread given there will be a bit more wind. We do expect some stratus to form and followed closer to the RAP which was picking up on that. A shortwave will be moving through the area as well tonight which should help produce some clouds. We don`t expect precipitation though as there isn`t very much moisture. RAP soundings show some shallow moisture with it rather dry above. There will be more clouds on Sunday but highs will again be a bit above normal. The rest of the week will feature a few shortwaves moving through the region. We have some small POPS Wednesday into Thursday and significant precipitation is unlikely. High temperatures will warm a bit more and be several degrees above normal. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 535 PM CST Sat Jan 7 2023 This should be another bear of an aviation night with ample low level moisture albeit thin and transient. Covered the TAFs with a hint that stratus/fog will form, but confidence in when and where is fairly low as model consensus guidance has been all over the place and generally trending towards better conditions though not entirely convinced that that will be the case. LLWS will cross the Arrowhead around midnight. && .MARINE... Issued at 258 PM CST Sat Jan 7 2023 Southwest winds will increase this evening with gusts around 25 knots developing over portions of the nearshore waters. Waves will build and Small Craft Advisories have been issued for portions of the nearshore waters into Sunday. Winds will veer Sunday into Sunday night to west or northwest, decreasing Sunday night. Winds will be less than 10 knots on Monday. && .PRELIMINARY POINT TEMPS/POPS... DLH 4 21 11 25 / 0 0 0 0 INL 10 23 8 24 / 0 0 0 0 BRD 3 23 10 25 / 0 0 0 0 HYR 1 23 8 28 / 0 0 0 0 ASX 8 26 13 28 / 0 0 0 0 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. LS...Small Craft Advisory until 7 PM CST Sunday for LSZ140-141. Small Craft Advisory from 11 PM this evening to 9 PM CST Sunday for LSZ146-147-150. && $$ DISCUSSION...Melde AVIATION...Wolfe MARINE...Melde
National Weather Service Hastings NE
534 PM CST Sat Jan 7 2023 ...Aviation Update... .DISCUSSION...(This evening through Saturday) Issued at 416 PM CST Sat Jan 7 2023 -- Key Messages: * The vast majority of the 7-day forecast looks to be pretty quiet weather-wise, with really only two possible concerns on our "radar" at this point: 1) chance of at least transient areas of fog/possible dense fog tonight into Sunday AM...2) a fairly strong (but quick-hitting) storm system that COULD bring a bit of wintry precip to at least parts of our coverage area (CWA) Wed evening-Thurs AM (FAR too soon to get too "worked up" about this). * Temps for the 7-day as a whole look to average out ROUGHLY 3-5 degrees above early-January normals, as we just keep rolling along in a "not overly warm/but far from frigid" weather pattern. This means highs well into the 30s/40s most places on most days, with some 50s even likely on a few days especially near/south of the state line into KS. * None of the next 7 days look particularly windy (especially by winter standards), with the overall-strongest winds likely to accompany the aforementioned later-week weather system, but even then, projected gusts only look to top out around 30-35 MPH. -- More detailed overview/highlights of the entire 7-day forecast (including all discussion of Days 3-7 Tues-Sat): 1) General overview of the large-scale upper air/surface pattern and any notable model differences: On the whole, the latest ECMWF/GFS runs are in pretty darn impressive agreement through the next week, bolstering confidence in the overall-theme of our going forecast and lessening the chances of getting "zinged" by notable surprises. In the upper levels, we`ll start off with several days of a mix of broad riding or quasi-zonal (west-east) flow until the arrival of the aforementioned Wed-Thurs system. In the wake of that system, a rather large-scale upper ridge is projected to build over the central CONUS Fri-Sat, giving increasing confidence in another period of dry/warming conditions into next weekend. At the surface, fairly light westerly breezes will prevail Sun-Mon (setting the stage for a decent little warm-up), with winds then turning easterly and/or southerly ahead of the aforementioned system, followed by modestly-stronger northerly winds in its wake Thurs, and finally a flip around back to southerly breezes by Saturday. 2) Precipitation overview (more on the Wed evening-Thurs system): High confidence in our going dry forecast for tonight-Wed daytime, and then again Thurs night-Saturday. That obviously leaves the aforementioned Wed evening-Thursday daytime system as the only period to feature official precip chances (PoPs), which remained fairly similar to previous forecast...mainly in the 20-40 percent range (lowest north/highest south). Not going to spend a ton of time droning on about a system still solidly in the Day 4-5 time range, but here are some basics: - This looks to be a fairly strong system, with both the ECMWF/GFS depicting a closed 500 millibar low. It also looks to be a quick-mover, with the eastern edges of the main system/lift entering western parts of the Plains Wed afternoon-evening and departing the region eastward into the Midwest/Mid-South by Thurs afternoon-evening. As a result, we`re currently looking at only a 12-18 hour window of opportunity for possible precip. - At least for now (still subject to shift, of course), the ECMWF/GFS solutions track the main upper/surface lows to our south, generally along the KS/OK borders. This is why our southern zones (especially KS zones) are most favored for measurable precip and our northern zones least favored. - IF precip does indeed end up affecting our CWA, amounts don`t look overly-heavy, with latest ECMWF ensemble painting only 0.05-0.10" QPF across most of our Nebraska zones, and 0.10-0.20" in our KS zones. - However, IF precip does indeed materialize locally, this could be yet another "headache" with precip type, with raw/initialized forecast grids suggesting a varied mix of rain, snow and even freezing rain/sleet. Given this system is still several days out and given the inherent uncertainties in mixed types, collaborated with neighboring offices to keep the OFFICIAL forecast as a "simple" rain/snow mix for now. 3) Temperature overview: Already touched on some of this in the Key Messages bullet above, but not only is there a strong signal for at least these next 7 days to average modestly warmer-than-normal, but ECMWF ensemble data and CPC 8-14 day outlook depicts fairly high confidence in at least slightly-warmer-than-normal temps persisting right on into Week 2 as well (technically covering Jan 15-21). Getting back to these first 7 days, after comparing our official forecast to some raw numerical guidance (and also after seeing temps already today over-achieve a bit), this forecaster is sensing that we are probably not aiming warm enough on several upcoming days (in other words, our official forecast may be too cool). Of course, the continued existence of generally 1-5 inches of snow cover within roughly the northwest half of our CWA complicates manners (cooler over the snow/warmer in our snow-free southern/eastern zones), but odds favor a lot of this now melting fairly steadily these next few days. On one last temp note, if anything confidence is pretty high that Thursday will be the coldest day of the next week in the wake of the departing system, but even then we are still talking highs low-mid 30s most areas (far from frigid by January standards). -- With the main messages/highlights of the entire 7-day outlined above, will conclude with some shorter-term details focused solely on the first 48 hours/4 forecast periods: - Current/recent weather scene as of 330 PM: Overall, not a bad January day across our CWA. Despite plentiful mid-high level clouds (skies ranging partly cloudy to outright- cloudy), high temperatures in many (not all) places have exceeded our early-AM forecast by 3-5 degrees, with highs ranging from low- mid 30s in most of our north (except for a few upper 20s in our far northeast), to the low 40s in our KS zones. Also, despite plentiful elevated radar returns (the beam detecting precip well above the surface), we have seen no ground-truth of flurries actually reaching the ground, and have maintained the going dry forecast through the rest of the day. In the mid-upper levels, water vapor imagery and short term model data depicts our CWA on the back-side of a compact-but-moisture-starved disturbance currently centered over the NE/KS/IA/MO border area, with upper riding off to our west over the Rockies, and another well-upstream trough off the Pacific Coast. At the surface, adding to the decent conditions today have been unusually-light winds for this time of year, with our CWA along the southwest periphery of departing surface high pressure centered over the IA/MN border (which pushed much colder air into northeast Neb this morning), and a warm front with light southerly winds developing into our western CWA. with little exception today, wind speeds have averaged no more than 5-10 MPH from variable directions in the weak pressure gradient. - This evening-overnight: By FAR the concern (but also the main question mark) is the possibility for at least localized/brief fog and/or dense fog development, especially over the snow-covered areas of our north/west. In the mid-upper levels, the aforementioned system just to our east will continue its slow departure overnight, its center reaching the IA/MO/IL border by sunrise. As it pushes farther way, our deck of mid-high clouds will gradually depart this evening, with the latter part of the night averaging mostly clear. At the surface, light southerly breezes will prevail this evening, but the passage of a weak surface trough will turn breezes westerly post-midnight, with speeds remaining no more than 5-10 MPH. As a result, we have definite pros/cons for fog development. The clearing skies and elevated low-level moisture especially over the lingering snow cover in our north/west would be favorable for fog development, BUT the overnight shift toward more west-southwesterly breezes (downslope) is typically rather unfavorable for fog development...especially of the widespread/dense variety. In the end, opted to maintain the previously-introduced chance of "patchy fog" for mainly the northwest half of the CWA (which appears most favored), but pulled the official mention from the southeast half (hopefully the right move?). Have been watching HRRR visibility progs closely today, which suggest at least brief/transient dense fog is possible north/west, but confidence in dense fog is only medium-at-best, especially given the aforementioned westerly breezes and fact that models often struggle with fog potential over snow-cover. Just in case though, opted to officially introduce the possibility for at least patchy dense fog to our Hazardous Weather Outlook (HWOGID). Temp-wise, nudged lows up a few degrees from previous forecast, ranging from teens north to low 20s south. - Sunday daytime: Once any possible (not sure thing) fog burns off in the morning (HRRR suggests it could linger as late as around 10 AM in our northeast zones), this looks to be a seasonably-pleasant day with plenty of late-morning/early-afternoon sun giving way to gradually increasing high level clouds from the west in the afternoon. Breezes will average westerly around 10 MPH. After seeing temps over-achieve a bit today, feel tomorrow could easily feature a bigger warm-up than previously expected and actually boosted highs a good 3-5 degrees over snow-free areas (less-so where snow cover lingers). The net result will be a fairly decent gradient from mid-upper 30s north to low-mid 40s central (Tri Cities) to upper 40s-low 50s near/south of the state line. - Sunday night: While more patchy fog cannot be completely ruled out, did not have enough confidence to add to official forecast, especially with continued light southwesterly breezes. Under only passing mid-high level clouds, low temps are aimed similar to a few degrees warmer than tonight (most of the CWA 17-24). - Monday daytime: Despite the passage of a weak/moisture-starved upper wave, we should remain dry with only a batch of passing mid-high level clouds. Although did not raise highs as much as was done for Sunday, feel we could easily be aiming a bit too cool given continued west-northwesterly breezes...a touch stronger than Sunday with sustained speeds 10-15 MPH/gusts around 20 MPH. For now, only nudged up highs 1-2 degrees over previous most areas, aiming from low-mid 40s north (aiding in continued snow melt), to upper 40s-low 50s again south. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Monday) Issued at 520 PM CST Sat Jan 7 2023 Broken midlevel clouds moving through the area currently will thin out tonight, potentially allowing some patchy fog to develop late tonight into Sunday morning. Confidence is not in this occurring, but the HREF ensemble does indicate > 50 percent probability of sub-VFR visibility/ceilings in the early morning. As such, included a period of 4SM fog. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ DISCUSSION...Pfannkuch AVIATION...Mangels
Area Forecast Discussion
National Weather Service Lincoln IL
746 PM CST Sat Jan 7 2023 .SYNOPSIS... Issued at 309 PM CST Sat Jan 7 2023 An area of low pressure tracking from eastern Oklahoma into the Ohio River Valley will bring a period of light wintry precipitation to central Illinois tonight into Sunday morning. Snow will be the primary precipitation type north of the I-70 corridor, with total accumulations of less than 1 inch. A mix of rain and snow is anticipated further south, with little or no snow accumulation. && .UPDATE... Issued at 745 PM CST Sat Jan 7 2023 Evening balloon sounding from our office shows a substantial dry layer from 900 mb up to 600 mb. Leading edge of the precipitation is inching toward Taylorville and Mattoon this hour, but ceilings have been in the 10,000 foot vicinity and little precipitation is likely reaching the ground at this point. HRRR forecast soundings for Springfield show the lower atmosphere showing some more steady moistening after 9 pm, and the higher precip chances will begin late evening between I-72 and I-70. However, forecast soundings over areas near/north of I-74 struggle to close the dry air gap overnight. Some potential for accumulations up to an inch from Winchester to Taylorville where some narrow banding potentially sets up, but overall accumulations still look to be a half inch or less over the forecast area. Recent updates were mainly to adjust the timing of the snow chances over areas near/north of I-74 overnight. && .SHORT TERM...(This evening through Sunday) ISSUED AT 309 PM CST Sat Jan 7 2023 20z/2pm surface analysis shows high pressure across Minnesota while a 1018mb low spins over western Arkansas. The pressure gradient between these two features is creating a cool/dry NE flow across central Illinois, which will initially act to keep light precip currently developing across Missouri at bay. Given ample dry air below 700mb, think it will take a couple more hours before any precip begins reaching the ground across the far S/SW KILX CWA. Despite temps well above freezing, think enough evaporational cooling will occur within the atmospheric column to support light snow...with a mix of light rain/sleet south of I-70 as the precip begins toward sunset. Once the column moistens more sufficiently, the primary precip type north of I-70 tonight will be light snow...with a mix of rain/freezing rain/snow further south. As has been advertised for the past several model runs, forcing with this system will remain weak and deep-layer moisture mostly absent. As a result, am expecting only minor snow accumulations of 1 inch or less north of I-70 tonight into Sunday morning. Secondary and untreated roadways will likely be snow-covered and slick during the morning, but any snow/ice will rapidly melt on the roads toward midday as temps climb above freezing. Based on how much time it will take to moisten the dry airmass, have hit PoPs hardest overnight into early Sunday morning when high chance to likely PoPs are warranted. The light wintry precip will come to an end from west to east by Sunday afternoon as highs top out in the middle to upper 30s. && .LONG TERM...(Sunday night through Saturday) ISSUED AT 309 PM CST Sat Jan 7 2023 Mild and dry conditions are anticipated Monday through Wednesday with highs well into the 40s...and even lower 50s south of I-70. The next system of interest will come into the picture by the middle of the week as a short-wave trough currently over the central Pacific Ocean crosses the Rockies and a surface low develops over western Kansas by Wednesday morning. The exact track of the low remains somewhat in question: however, model consensus continues to suggest it will skirt across parts of central Illinois on Thursday. Given this particular trajectory, conditions will likely be warm enough for rain until the low exits and pulls colder air back into the area late Thursday night into Friday morning. Will continue to monitor the system with subsequent model runs as it will have much more moisture to work with than the current system. Latest projections indicate rainfall of one half to three quarters of an inch across all of central Illinois. Once the low exits, a return to cool/dry weather with temperatures in the 30s is expected for next Friday and Saturday. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 525 PM CST Sat Jan 7 2023 South edge of MVFR cloud deck appears to have stopped along a KSPI-KTIP line early this evening, but there is some potential for it to sag a bit further south with time. HREF probabilities of MVFR ceilings increase to around 40-50% at KDEC/KCMI by 04Z. IFR conditions expected to develop after 06Z, though KCMI will be more on the edge and will keep ceilings above 1,000 feet there at this time. Area of light snow will be edging northeast into parts of central Illinois around late evening, but northern extent near KPIA/KBMI a bit more in question and most likely to be after 07-08Z there. Any snow will diminish from west to east Sunday morning, and ceilings likely to rise above 3,000 feet toward late afternoon near KPIA/KSPI. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Geelhart SYNOPSIS...Barnes SHORT TERM...Barnes LONG TERM...Barnes AVIATION...Geelhart
Area Forecast Discussion...UPDATED
National Weather Service Indianapolis IN
657 PM EST Sat Jan 7 2023 .Forecast Update... Issued at 657 PM EST Sat Jan 7 2023 Radar echoes across Illinois are associated with sloping midlevel moist layer and weak ascent immediately south of a deformation preceding an upstream shortwave trough in southwest Iowa. The ascent is fairly weak owing to stronger flow being relegated to lower latitudes, and generally weak pressure advection on the 295-300-K isentropic charts. Furthermore, the sub-cloud layer is quite dry. Most METARs have ceilings around 7-9-KFT, and only one has reported precipitation (KFWC/Fairfield). None of the higher density of personal weather stations have indicated measurable amounts as of this writing. As the band of modest midlevel ascent and moisture move northeastward into central Indiana, some sprinkles are likely. RAP soundings through the rest of the evening show favorable wet bulb profiles for snow, but precipitation intensity is unlikely to be heavy enough to saturate to the wet bulb temperature. Thus the ambient temperature profile shown in the models should be more representative of what precipitation type we will see for any hydrometeors that are able to reach the ground. Thus, we have trended the initial precipitation type this evening to mostly rain (or sprinkles) for most areas through midnight. It wouldn`t take much for dendrites to resist melting via localized thermal augmentation through evaporative processes, however, particularly with heavier echoes on radar. Another consideration is that already near/north of I-70, roughly, temperatures are at or just below freezing. We`ll have to watch this closely but we`re fairly confidence at this time that any rain or snow that makes it to the surface will be sub-measurable and shouldn`t cause impacts. Furthermore, above freezing temperatures today with solar radiation has ground and road surface temperatures above freezing, per latest MRMS/NSSL subfreezing road temperature probabilities, and we should also remain in a marginal temperature range where latent heat of fusion will be a factor as well. All other forecast elements look fine at the moment. && .Short Term...(This evening through Sunday) Issued at 215 PM EST Sat Jan 7 2023 High pressure to the northwest of central Indiana was nosing into the area, providing dry conditions this afternoon. Some lower clouds were across northern portions of the area, but these had stalled their southern expansion. Rest of this afternoon... Lower clouds will hang around the north this afternoon, with some slow decrease from the south possible. Elsewhere will see sunshine, with some mid and high clouds arriving late. Tonight... Ahead of an approaching upper trough, isentropic lift will move in from the southwest tonight and spread across the forecast area. There will be some decent mid-level moisture with this lift, but the the lower levels of the atmosphere will remain pretty dry. Precipitation amounts will be light and coverage will be patchy given the overall lack of deep moisture. Precipitation type based on temperature profiles looks to be a mix of rain and snow, but wouldn`t rule out some very light freezing rain if moisture isn`t deep enough to get into the colder air to form ice crystals. With light amounts and only patchy precipitation, do not expect much if any impacts. Will keep PoPs in slight chance to low end chance category. Low temperatures will be in the upper 20s north to lower 30s south. Sunday... The upper trough will move across the area during the day, with a surface low well off to the south. Broad forcing will move across the area with the trough, and there is some hints at deformation in the mid levels which could add additional forcing. However, once again the limiting factor will deep moisture. There will be more than tonight, but it still won`t be great. Thus, will keep PoPs no higher than chance category. With an increase in moisture, ice crystals will be more prominent in the cloud layer on Sunday. This will mean precipitation starting as snow, and depending on temperatures at a location, some of this will melt and create a rain/snow mix or just plain rain. If deformation is stronger than expected, wouldn`t be surprised to see isolated snow amounts over a half inch on Sunday, but at the moment believe amounts will only be a tenth or two. Temperatures will rise into the middle 30s to around 40, which will help keep any impacts from the precipitation minimal to non- existent. && .Long Term...(Sunday night through Saturday) Issued at 215 PM EST Sat Jan 7 2023 Monday through Wednesday... Westerly WAA will help build upper level ridging over the Midwest early this week, along with some low level height falls over the northern Plains. As a weak surface cyclone develops to the NE, low level flow will shift back towards southerly, further promoting the progression of above seasonal temperatures over the region. To supplement this warm air mass will be broad subsidence from the upper level ridge leading to mostly sunny skies. All in all, expect pleasant weather Wednesday with highs in the mid to upper 40s. Thursday through Saturday... A surface low associated with a more impressive upper trough could bring a better chance for precipitation late next week. Ensembles show around a 50-60% chance for probability of QPF > 0.5inches. In addition PWAT anomalies are 200% above normal during this period. Favorable forcing from the surface low and parent wave combined with sufficient moisture return supports likely POPs late next week. Although rain is likely, low confidence remains in regards to timing, location of the trough, and rainfall amounts due to model ambiguity. A majority of the ensemble spread places central Indiana within the warm sector of this system, but there still remains slim possibilities for frozen precipitation given the amount of cold air behind this system. Any low track deviation southward would increase chances for below freezing temperatures late Thursday into Friday. Given the greater possibility of a low track NW of central Indiana, well above seasonal temperatures on Thursday are likely. A strengthening southerly LLJ will likely push temperatures into the 50s for most of the region. Variability for temperatures increases into next weekend and will depend on a multitude of undetermined factors, including the aforementioned low track. && .Aviation...(00Z TAF Issuance) Issued at 625 PM EST Sat Jan 7 2023 Impacts: * MVFR persistent with early morning breaks at LAF * Lowering ceilings and eventually MVFR by late morning or early afternoon elsewhere * Light rain or snow showers possible briefly later tonight, and again Sunday afternoon Discussion: Stratus should remain across northern portions of the area including KLAF through the evening and into tonight. There could be a brief window where this retreats and temporarily returns to VFR during the morning. Meanwhile, thicker mid cloud deck will overspread the area but we should remain VFR until late morning or early afternoon. Onset of MVFR is uncertain but it does seem later than earlier forecast indicated so we have nudged the start time forward a couple of hours. Refinements will be needed and at least a temporarily MVFR period earlier than currently indicated cannot be ruled out. With the initial push of midlevel moisture will be the chance of brief light rain or snow showers, but the best chance of meaningful precipitation currently appears to be during the midday and afternoon hours with a low probability of brief visibility reductions in light snow during that time frame. Winds will coincidentally back slightly to more northerly. Afterwards, MVFR ceilings will probably linger through the remainder of the TAF period. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ Update...BRB Short Term...50 Long Term...Updike Aviation...BRB
Area Forecast Discussion
National Weather Service Northern Indiana
715 PM EST Sat Jan 7 2023 .SYNOPSIS... Issued at 715 PM EST Sat Jan 7 2023 Light snow may be possible Sunday but no accumulation is anticipated. Otherwise dry conditions persist through Wednesday with highs slowly climbing into the 40s. Rain is expected late Thursday. && .SHORT TERM...(This Evening through Sunday) Issued at 259 PM EST Sat Jan 7 2023 Latest hi-res forecast soundings show ample moisture trapped under a strong idea support by 12Z KDTX sounding which showed saturated conditions from near-surface to 750mb. This will likely maintain mostly cloudy conditions into tonight. A few peeks of clearing may be possible through the evening as low level ridge axis passes and flow becomes more southerly but overall tough to erode that much moisture under an inversion in January. Updated the cloud forecast accordingly. Any partial clearing of low clouds this evening will be replaced by increasing mid/upper level clouds late tonight in advance of the next system. Some quick radiational cooling is possible if clouds do briefly scatter but nudged overnight lows up slightly given expectation for limited breaks. Previously noted trend toward a drier/more suppressed wave on Sun continued in 12Z guidance with serious doubts regarding any measurable precip. Vort max of interest is currently being stretched from Kansas to Illinois as confluent upper jet streak pulls rapidly eastward. Best precip chances expected to remain just south of our area where better moisture convergence will reside. However, not comfortable going entirely dry just yet as some guidance members show some weak, elevated fgen clipping areas south of US-30. Given substantial dry air noted from 925-700mb in the wake of strong subsidence...doubt this will be much more than flurries and have further lowered PoP`s/QPF. With highs in the mid 30s...most precip would likely fall as snow but have difficulty sticking, particularly on the roads, so no impacts anticipated. && && .LONG TERM...(Sunday Night through Saturday) Issued at 259 PM EST Sat Jan 7 2023 Bulk of the upcoming week remains quiet with largely split flow aloft and a ridge building around midweek. Will have to keep an eye on Tue as a weak shortwave zips through the region with a corresponding brief/minor uptick in low level isentropic ascent and theta-e advection. Held close to NBM with PoP`s around 10 percent but this may be worth a low chance mention in future forecast updates. Precip type would likely be liquid given degree of WAA pushing highs into the 40s so no impacts regardless. Next decent chance of precip remains late Thu into Fri as more formidable Pacific trough eventually works eastward. Deterministic and ensemble guidance in relatively good agreement for this time range...supporting likely PoP`s in latest NBM. Of course the big question will be exact precip amounts and thermal profiles which remain much more uncertain. Still looks like primarily rain given slow arrival of just marginally cool air but a mix is likely as precip exits on Fri. Highs slowly climb into the mid/upper 40s ahead of this system returning closer to normal by next weekend but not particularly cold. && .AVIATION...(For the 00Z TAFS through 00Z Sunday Evening) Issued at 712 PM EST Sat Jan 7 2023 Overcast with strong 900 mb subsidence inversion holding firm across northern Indiana. Focus again on whether higher end MVFR of little consequence or lower end with fuel/alternate rules applying be prevalent. Consensus of HRRR and LAV guidance for gradual lowering of ceilings overnight and will bring KSBN down to OVC015 at midnight. KFWA on cusp of critical ceilings and could creep back above 020 next few hours or even briefly scatter out as back edge of stratocumulus nears from the south but anticipate clearing advance to halt amid very weak boundary layer flow. Also, weak/gradual upslope through Maumee Valley and general overall trend points to lower ceilings dominant, at least until midday Sunday. Thereafter, some erosion of low level inversion as mid level circulation/shortwave, currently over northern Missouri, tracks eastward into northern Indiana. Increased moisture and lift within 3-6km layer associated with shortwave suggests seed- feeder mechanism may be in place for some light snow and have included mention at KFWA with KSBN remaining on northern periphery of best mid level moisture. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SYNOPSIS...Murphy SHORT TERM...AGD LONG TERM...AGD AVIATION...Murphy Visit us at Follow us on Facebook...Twitter...and YouTube at:
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
840 PM CST Sat Jan 7 2023 .UPDATE... Issued at 836 PM CST Sat Jan 7 2023 Isentropic ascent to the north of a baroclinic zone across the lower MS Valley and low level frontogenetic forcing is contributing to banded as well as showery precipitation in a west-east corridor of precipitation running along/parallel to I-70. The greatest coverage of precipitation, which is snow with a number of mobile east-northeast moving bands, is stretching from northern Boone County through southern Pike County MO into central Macoupin County where forcing is greatest and lapse rates are moderately steep. South of I-70 the precipitation is light, scattered and showery and has included rain and brief bursts of sleet. A number of ACARS soundings from KSTL has been showing gradual erosion of the elevated warm layer but still supporting mixed p-types. The RAP has been resolving the forcing and favored location for precipitation rather well since late afternoon. The expectation is as the upper low currently in extreme SW IA slides east-southeast tonight the low-mid level flow will veer to more westerly resulting in weakening upglide and a northeastward shift of the main area of banded precipitation. This should begin in earnest in the 03-06z time frame and really accelerate overnight. A band of 1-2 inches of snow and potential isolated amounts of 3 inches or so still looks on target along an axis from northern Boone County into northern Greene County. Impacts from the snow have been locallized. Road conditions have been quite variable with some slick and snow covered roads to just partially covered roads. Even with the main forcing/bands shifting northeast the remainder of this evening, weak forcing with the upper low will still bring a chance of light snow/showers to portions of eastern MO and western IL overnight into early Sunday morning. Glass && .SHORT TERM... (Through Late Tonight) Issued at 226 PM CST Sat Jan 7 2023 Early this afternoon, water vapor imagery revealed an upper level disturbance moving eastward across northern Missouri. This was reflected at the surface by a low centered just south of Branson, MO, with a warm front extending into the Ohio River Valley. Frontogenetical forcing on the north side of the low, along with falling heights aloft and modestly steep mid-level lapse rates, resulted in a band of scattered rain/snow/sleet showers extending from east-central KS to St. Louis, and an area of virga over northern MO. As the low drifts to the east this evening and overnight, the band of frontogenesis/low level convergence will move further into the Mid-Mississippi Valley. These features are expected to become increasingly aligned with stronger mid/upper level support and slightly steeper lapse rates, and will very likely result in a band or a few bands of enhanced precipitation. High resolution guidance continues to support this idea, with the vast majority of models showing an axis of 0.15-0.25" of QPF somewhere in Missouri to the east of Highway 63 and the north of Interstate 70. Obviously band placement is once source of uncertainty with this forecast. Another questionable aspect of this forecast is precipitation type. Temperatures have risen to near or above freezing for much of the areas this afternoon, but are largely supporting sleet or snow as of this writing. Temperatures will only fall farther this afternoon and evening, but somewhere across our south, will likely be too warm to support any frozen precipitation. It`s still uncertain where the rain/snow line will set up, but for the time being, it looks like areas south of I-70 will see mostly rain or rain and sleet, with areas further north seeing mostly snow and sleet. For areas that do see snow, snow-to-liquid ratios represent another forecast challenge. Forecast soundings continue to show limited moisture in the DGZ, and I`ve struggled to find a forecast sounding with much lift in the DGZ. Moreover, relatively warm ground temperatures will further limit accumulations. Given these factors, I anticipate SLRs to generally remain well below climatology (12:1). However, forecast guidance often struggles to handle these mesoscale bands, and I wouldn`t be surprised to see SLRs within the band briefly approach climatology, resulting in snowfall amounts topping 2" in some areas. Precipitation will begin to taper off by midnight as the surface low weakens and frontogenetical forcing wanes. BSH .LONG TERM... (Sunday through Next Saturday) Issued at 226 PM CST Sat Jan 7 2023 This evening`s system will move east of the area by tomorrow morning, leaving rising heights and increasingly dry air in its wake. Initially cool and cloudy conditions with NNW winds will give way to clearing skies and more westerly winds, boosting temperatures back toward just above normal. On Monday, a shortwave will move into the Northern Plains and Upper Mississippi Valley. This will spur weak surface troughing over the Plains, further backing low level winds over our region and drawing in warmer air. Continued WAA and limited moisture advection is expected to push temperatures well above normal on Monday afternoon. The above shortwave will continue to push southeastward on Tuesday, dragging a weak cold front into the region. The majority of forecast guidance shows only weak cold air advection behind the front on Tuesday, with notably drier air pushing into the region. Mostly clear skies will counter the weak CAA, and should keep afternoon temperatures on Tuesday afternoon 10-15 degrees above normal. The warmup will continue into Wednesday due to a combination of rising heights aloft and increasingly southerly low level flow. On Wednesday night and Thursday, forecast guidance is in strong consensus depicting a closed low moving from the Four Corners region into the Southern Plains. The associated surface low will hook from the OK/TX panhandles into the Mid-Mississippi Valley on Thursday, bringing widespread precipitation to the region. Unsurprisingly, there are notable differences in the track and timing of the low, which introduces considerable uncertainty to this portion of the forecast. Anything from thunderstorms ahead of the low to snow on the back side of the low is on the table, so this will be a system to watch over the coming days. Upper level ridging and dry northwest winds behind the mid-week system should help dry things out beginning on Friday. The northwest winds will also push temperatures back toward normal for the weekend. BSH && .AVIATION... (For the 00z TAFs through 00z Sunday Evening) Issued at 543 PM CST Sat Jan 7 2023 A potpourri of precipitation is ongoing across the area as we approach 00z. The greatest coverage of perception is generally north of I-70 and south of KUIN, thus inbetween the terminals. KCOU and KJEF will see bands of light wintry precipitation (-RA/-SN/-IP) through 03z or so, occasionally bringing MVFR flight conditions. The St. Louis metro terminals (KSTL/KSUS/KCPS) will see more showery precipitation including rain showers, and at times potentially short bursts of sleet. By 03z or so the majority of the precipitation should be lifting northeastward and at that time could impact KUIN, although the greatest coverage is expected to remain south of them. From late evening through overnight and into early Sunday morning flight conditions will deteriorate as the result of lower ceilings with stratus. If we see any snow after 06z, it generally should be light, not long- lived and non- impactful. Improving flight conditions to VFR is expected on Sunday afternoon as stratus slowly clears NW to SE. Glass && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Morristown TN
942 PM EST Sat Jan 7 2023 ...New UPDATE... .UPDATE... Issued at 934 PM EST Sat Jan 7 2023 Forecast on track this evening with only minor adjustments to temperatures. Lowered Tri-Cities from 34 to 33 for an overnight low due to recent hourly temp/dewpoint trends. In the grand scheme of things this doesn`t make much of a difference though as temperatures begin to slowly warm after midnight due to increasing southwest flow. Due to the warming, any precip that moves in late tonight/early morning will still be in the liquid form. This is validated by latest HRRR and HREF runs which continue to show any wintry precip east of the east TN mountains. Will send new zones for temp adjustment. && .SHORT TERM... (This evening through Sunday) Issued at 308 PM EST Sat Jan 7 2023 Key Messages: 1. Rain likely on Sunday as a low pressure system moves across the area. 2. Lingering light mountain showers/snow showers/rime ice Sunday night within the weak northwest flow with drier conditions arriving around Monday morning. Discussion: Closed upper low will open into a broad upper trough and move eastward on Sunday in response to an approaching southeastward moving shortwave across the northern Great Plains. A strengthening 130 kt upper jet streak at 300 mb will stretch SW to NE from the Tennessee Valley through the Central Appalachians placing our forecast area within the right-entrance region favorable to upper-level divergence. The LLJ will respond by strengthening early Sunday with convergent low-level flow across our area as 850 mb winds reach 30 to 40 kt with precipitation being likely throughout the day. We should have fairly good moisture return across the region with PW values of 0.9 to 1.0 inch around the 90th climatology percentile. Overall, 0.5 to 0.75 inch of rain is probable across the region with some locally higher amounts. While some breezy conditions may be possible across the highest elevations, this does not appear to be a mountain wave event with high-impact winds. As the surface low tracks across the area late Sunday afternoon, winds begin to shift to the west and northwest with CAA in the wake of the cold front. Some lingering orographic precip will be possible across the mountains of East Tennessee and southwest Virginia as 850 mb NW flow of 10 to 20 kt creates some localized lift along the terrain. However, precipitation will be light with shallow moisture exiting the region. Any snowfall will likely be less than one inch and generally at or above 4000 feet elevation with rime ice likely being more widespread than snow across the higher terrain because of the shallow moisture mostly below the DGZ. && .LONG TERM... (Sunday night through next Saturday) Issued at 308 PM EST Sat Jan 7 2023 Key Messages: 1. Mountain snow showers Monday morning followed by high pressure through Tuesday and again on Wednesday. 2. Strong cold front will begin to impact the area Thursday. 2. Overall, temperatures expected to remain near or just above normal through the period. Discussion: Following a low pressure system exiting off to our east, subtle riding aloft and surface high pressure will settle in later Monday into Tuesday. Day 4 or middle of the day Tuesday has been tricky the past few model runs with a rather weak shortwave to our north. It has bounced back and forth between a dry system or one that will quickly bring a slight chance of showers to parts of the area Tuesday afternoon and evening. The one model that surely sticks out like a sore thumb right now is the 12z run of the GFS; more moisture and the low center survives across the Great Lakes. The last few hours of the 12z NAM somewhat follows. The Canadian and Euro, however, show the surface low dissipating all together. Alas, not an impactful system if it comes to fruition. Wednesday will be dry ahead of a deepening upper level low, as ridging will build in and dominate the day. This will also translate with temperatures as well where Wednesday and Thursday will trend the warmest for the period. Thursday into the first part of the weekend appears to be a pretty dynamic system developing with widespread to numerous showers and possible strong winds over the higher terrain. We will see how this unfolds as this isn`t until the day 5/6 time period. && .AVIATION... (00Z TAFS) Issued at 626 PM EST Sat Jan 7 2023 Rain showers move in late tonight and into tomorrow morning across the forecast area, lowering CIGs at all sites. CHA is currently VFR but expect MVFR around midnight, then IFR by sunrise. CIGs lift back to MVFR tomorrow afternoon. A mix of VFR and MVFR are expected at TYS and TRI this evening and overnight, then CIGs drop to prevailing MVFR tomorrow morning and remain through the period. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 44 54 37 52 / 80 90 10 0 Knoxville McGhee Tyson Airport, TN 41 53 37 48 / 70 90 50 10 Oak Ridge, TN 41 51 35 49 / 60 90 30 10 Tri Cities Airport, TN 33 48 36 45 / 50 90 80 10 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...SR LONG TERM....KS AVIATION...SR