Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/30/21

Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
601 PM MDT Sun Aug 29 2021 .AVIATION... 00Z TAF CYCLE Scattered thunderstorms will favor the northeast half of NM this evening and overnight with isold MVFR cigs/vsbys and terrain obscurations in the stronger storms with very heavy rain, hail and gusty downburst winds. A quasi-line or cluster of storms is forecast to move swd through portions of ne and east-central NM aft 30/00Z, which may remain relatively intact through 30/06Z before possibly reaching KROW thereafter. Potential for areas MVFR cigs/patchy br from the east slopes of the central mt chain to the TX border 30/10Z- 15Z. As drier mid-level air works in from the northwest on Monday, afternoon thunderstorms will be isolated mainly mts and central highlands including KCQC. 33 && .PREV DISCUSSION...243 PM MDT Sun Aug 29 2021... .SYNOPSIS... Scattered to numerous thunderstorms across central and eastern New Mexico will gradually diminish in coverage late this evening. Another round of hit and miss storms is expected Monday and Tuesday as temperatures warm a few degrees above normal. An increase in moisture from the eastern Pacific may allow for an increase in thunderstorms and heavy rainfall Wednesday and Thursday, especially for western and central New Mexico. This influx of moisture will also allow for temperatures to cool several degrees. && .DISCUSSION... SHORT TERM...(TONIGHT THROUGH MONDAY NIGHT)... Showers and storms have developed over the higher terrain as well as over portions of east central NM where an outflow boundary has already been expelled from the cluster of storms there. The HREF suggested the east central plains would see this area of storms initially then would be impacted this evening by another cluster that was to progress through parts of northeast NM first. Several runs of the HRRR also latched onto the idea there would be a cluster that moved southward mainly between the central mountain chain and the Pecos Valley this evening and overnight. The 18Z NAM also keeps this evening/overnight cluster tracking over the same area, so there is some consensus. Therefore will leave the Flash Flood Watch as is but with the slow and erratic storm motion, any cell could produce heavy rain and flash flooding if it hits a vulnerable area. Otherwise, there may be some patchy fog from the east slopes of the central mountain chain to the TX border late tonight and have added that to the weather grids. Monday should feature a bit of a downturn in activity with the southwest mountains and central mountain chain the focus areas for storms. The northwest and north central tend to dry out a little and a weak lee trough will replace the low level east winds observed this afternoon. Highs on Monday will be near normal, with the east seeing a few degrees of warming over today`s highs. Lows will be a few degrees above average. LONG TERM...(TUESDAY THROUGH SUNDAY)... Deterministic models as well as their ensembles are in very good agreement with the H5 high building over NM on Tuesday. With pressure heights rising to about 589dam and 700mb temperatures warming, high temperatures will rise as well and are expected to be a few degrees above late August normals for most of the area. With this high overhead, PWATs will fall below an inch, and this will lead to a relative downtick in storm coverage. Moisture won`t be completely scoured out though, and isolated to widely scattered convection will mostly favor the western and northern high terrain and adjacent highlands. A pattern shift is expected starting Wednesday thanks to now Tropical Storm Nora. Nora will be tracking northward along the west coast of Mexico early this week and is currently forecast to be a tropical depression by early Thursday as it nears the northern Gulf of California area. Meanwhile, a trough moving inland into the PacNW and increasing southwesterly flow ahead of it will allow for the aforementioned H5 high to shift back to the east over OK and TX. This opens the door for quite the tropical moisture plume courtesy of Nora to develop over the southwest U.S. The moisture plume develops over AZ first on Tuesday and then shifts into western NM on Wednesday. By Thursday, the moisture plume develops over NM and PWATs are forecast to climb to the 1.1 to 1.3 inch range with some models (most notably the ECMWF) even forecasting PWATs higher. This is well above the 90th percentile for early September which is around 0.99" and could even rival daily record PWATs. What all this means is precipitation chances will rise starting Wednesday and then become more widespread over northern and central NM Thursday. And with these anomalously high PWATs, heavy rainfall and flash flooding may become a big concern. WPC is already highlighting a slight risk in the Day 3 ERO in southern AZ to account for this increasing moisture. Confidence is then lower in the upper-level pattern Friday and through the weekend. Deterministic models and their ensembles keep the H5 high well to our east through the weekend, but they are having a more difficult time in resolving the general troughing pattern that sets up over the western CONUS. Still, the moisture doesn`t look to be going anywhere so an active pattern looks to be on tap as we head into early September. 15 && .FIRE WEATHER... Storm coverage has increased this afternoon, especially over east central New Mexico, but the Northwest Plateau will remain mostly dry with only a few cells. Locally heavy rain which could lead to flash flooding is possible, as cell motion will be slow and erratic, especially later this afternoon and evening as outflow boundaries develop. There will likely be a decrease in the number and areal coverage of storms on Monday except for the west central and southwest high terrain where scattered to numerous storms are again forecast. Tuesday looks to be the least active day with the center of high pressure aloft over New Mexico and storms confined to the central mountain chain westward. Both maximum and minimum humidities decrease over northwest and north central New Mexico Monday and Tuesday. On Wednesday, an upper trough moving into SoCal will nudge the upper high far enough to our east to allow a stream of moisture into Arizona, which will reach western New Mexico later in the day. The plume progresses into central and northern New Mexico Thursday and Friday and increases the potential for more widespread showers and storms. Thereafter, model differences start to appear, although it looks like at least isolated, if not scattered convection stretched from the southwest mountains to the northeast plains will persist through the weekend. Fair to poor ventilation is featured Monday and Tuesday for many areas across western and central New Mexico. Widespread poor rates are forecast across the west and central Thursday and Friday. && .ABQ WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch until 4 AM MDT Monday for the following zones... NMZ208-209-212-214-215-221>226-229-232-233-239>241. && $$
Area Forecast Discussion
National Weather Service Bismarck ND
941 PM CDT Sun Aug 29 2021 .UPDATE... Issued at 941 PM CDT Sun Aug 29 2021 Little change was needed to the overnight forecast once again, but we did expand the slight chance of thunderstorms Monday afternoon and evening further north and east, adding much of central ND into the potential. Guidance suggests low-level moisture return beneath steepening midlevel lapse rates on the leading edge of an elevated mixed layer will yield considerable bouyancy by afternoon, while deep-layer shear would favor potential organized, severe updrafts. Synoptic-scale forcing and low-level convergence are both currently forecast to be weak, so this represents a conditional severe-storm risk, and some caution is advised in considering more aggressive CAMs like the 00 UTC HRRR given those factors. However, evidence is increasingly supportive of the need to begin communicating the possibility that such a scenario could come to fruition, even if it`s highly conditional on uncertain convective initiation. UPDATE Issued at 609 PM CDT Sun Aug 29 2021 All we did with this update was blend recent observed trends and NBM data into hourly forecast fields through the night, with very little change. Expect diurnally-driven cumulus fields to wane as the boundary layer cools and stabilizes this evening, leaving a quiet and seasonably cool night. && .SHORT TERM...(This evening through Monday) Issued at 219 PM CDT Sun Aug 29 2021 Current surface analysis places high pressure over northern Wyoming into Montana, with low pushing over Ontario, keeping a west to northwest breeze over much of our area. Upper level analysis places trough sliding into the Great Lakes region, with rather zonal flow to our west. A broad area of fair weather cumulus has developed over our region, otherwise quiet weather continues. For tonight, clouds will diminish with the loss of daytime heating. Thereafter, a quiet night is expected. On Monday, the day will start out quiet. During the afternoon, instability will be on the increase, particularly over the southwest, with good shear in place. This sets the stage for the possibility of a severe storm or two, but ample forcing to produce a storm remains in question. Therefore, have gone with a slight chance of thunderstorms, but if one does develop it could become strong. Better chances remain well to the south of our area. .LONG TERM...(Tuesday through Sunday) Issued at 219 PM CDT Sun Aug 29 2021 On Tuesday ridging enhances over the area as upper low drops south through British Columbia. Ridge slides east as the first of multiple waves from this system push through the area, bringing shower/thunderstorm chances. This system then slowly meanders easterly bringing chances for precipitation through the week. As for severe potential, the best chances continue to be Wednesday when ample instability and shear are forecast to be in place during the afternoon and evening hours. Will have to keep an eye on this on future forecasts. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 941 PM CDT Sun Aug 29 2021 VFR conditions will prevail through the 00 UTC TAF cycle. A low probability of thunderstorms exists in southwestern and central ND Monday, mainly after 18 UTC, as instability returns. However, uncertainty in forcing mechanisms for storms precluded us from including any mention of them in the 00 UTC TAFs. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...CJS SHORT TERM...JJS LONG TERM...JJS AVIATION...CJS
Area Forecast Discussion
National Weather Service Boise ID
828 PM MDT Sun Aug 29 2021 .DISCUSSION...HRRR smoke model has proved correct bringing the smoke aloft back into our CWA from the southwest today. Monday looks worse as HRRR shows near-surface smoke also increasing from the southwest. Northern Harney County may be spared with westerly flow aloft there keeping most of the smoke out, but Baker County will be directly downwind of the Bull Complex Fire in north- central Oregon and will receive some of that smoke. Aside from the smoke our Idaho zones will be sunny and very warm again Monday while Oregon zones begin to cool down as a weakening Gulf of Alaska upper trough comes inland. A dry surface cold front will pass through eastern Oregon Monday and western Idaho Monday night, followed by cooler temps in all areas Tuesday. Current forecast has this. No updates. && .AVIATION...Mainly VFR. Wildfire smoke layers over much of southeast Oregon and southwest Idaho could degrade visibility at times. Surface winds: variable 10 kt or less. After 30/1800Z, becoming W-SW 10-20 kt with gusts to around 25 kt, except W-NW 5-15 kt in the Snake Plain. Winds aloft at 10kft MSL: SW 10-25 kt. && .PREV DISCUSSION... SHORT TERM...Tonight through Tuesday night...Conditions will remain dry across the region through the period. A west to southwest flow over the area will transport smoke, advancing through southeast Oregon this afternoon, further into the region tonight and Monday. The thicker smoke layers aloft and eventually surface smoke will be south and east of a Burns-Ontario-Cascade line by Monday. A trough will push into the Pacific NW on Tuesday bringing cooler temperatures but with flow aloft remaining out of the southwest would expect to at least keep smoke layers aloft. Temperatures will be a few degrees above normal Monday, cooling to several degrees below normal on Tuesday. LONG TERM...Wednesday through Sunday...Southwest Idaho and southeast Oregon will remain on the interface between a cool upper level trough over southern British Columbia and Alberta and a strong upper level ridge containing hot temperatures and monsoon moisture to the south and east. Afternoons will feature breezy west-northwest winds through the period. Temperatures will be around 5 degrees below normal on Wednesday, warming to normal by Saturday. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && $$ DISCUSSION...LC AVIATION.....SH PREV SHORT TERM...DG PREV LONG TERM....KA
Area Forecast Discussion
National Weather Service Indianapolis IN
1144 PM EDT Sun Aug 29 2021 ...Updated Aviation Discussion... .Forecast Update... Issued at 942 PM EDT Sun Aug 29 2021 This evening, a broken line of thunderstorms continues across northern sections of central Indiana, with isolated convection to the south. The storms in the north are being forced by some prefrontal convergence and some vorticity aloft. Storms have been pulse like in nature with perhaps some gusty winds and small hail. The forcing will continue tonight, especially north, closer to the vorticity and the front. Will go with higher end chance PoPs there tonight. Less forcing south will lead to slight chance or low end chance PoPs there. Confidence is not has high in the south with the weaker forcing and the latest trends in hi-res models to back off on coverage there. Mixed Layer CAPES of 2000-2500 J/KG will keep the threat of gusty winds and small hail around. Adjusted sky cover and hourly temperatures as needed based on latest trends. && .Short Term...(This evening through Monday night) Issued at 302 PM EDT Sun Aug 29 2021 This Evening/Tonight... CAMS are struggling a bit with convective initiation this afternoon. Showers and thunderstorms have formed rather quickly over the last hour and are more widespread than models were projecting. Despite the persistency, thunderstorms are expected to remain below severe levels though this afternoon and evening without any significant dynamics. Current convection is mainly being diurnally driven in the warm, moist environment as a weak influx of moisture continues on the back side of high pressure dome. That will, however, change tonight as a cold front drops into the forecast area. This additional forcing could be enough to trigger some isolated strong to severe thunderstorms (mainly north) overnight, which is highlighted by the Marginal Risk per SPC. HRRR starts keying in on re-initiation of convection around Mon 01/02Z over the northern counties with cold front, eventually shifting southward toward daybreak. Monday/Monday Night... The aforementioned cold front will eventually be met with the northward propagation of Ida on Monday morning, stalling it a bit. The surge of moisture from Ida will eventually overtake the southern third of central Indiana on Monday afternoon with PWAT values approaching 2 inches and a Slight Risk in the excessive rainfall forecast. Flooding will be a threat across the southern tier of counties. Elsewhere, the effects of Ida will be less pronounced over the northern portions of central Indiana. So, will trend toward categorical Pops Monday afternoon over the southern counties with likely Pops to the north. With the cold front and extensive rainfall, the heat wave will finally break on Monday as highs drop a bit into the mid to upper 80s. And, overnight lows Monday night will dip into the mid to upper 60s. && .Long Term...(Tuesday through Sunday) Issued at 302 PM EDT Sun Aug 29 2021 The remnants of Hurricane Ida will be passing by central Indiana to the southeast on Tuesday...with an abundance of clouds and continued scattered to numerous showers impacting the region. Beginning early Wednesday...the pattern will transition to dry and more seasonable as Ida shifts off to the east and a broad high pressure ridge builds in. The best chance for rain throughout the extended period will be on Tuesday as what is left of Ida passes through the Tennessee and Ohio Valleys. The track of the remnant low has solidified from middle Tennessee into the central Appalachians...with the bulk of the broad area of rain remaining to the southeast of the region. The diffuse cold front however will still be in the southern half of the forecast area on Tuesday with the potential for tropical moisture to advect north into the area and interact with the front. A mid level deformation axis will align north of the track of the remnant low...likely aligning across southern Indiana and Ohio and potentially impacting far southern portions of the forecast area. While the potential for beneficial rainfall is there through Tuesday night...any flood concerns will be localized considering antecedent soil conditions which are quite dry over the last 6 weeks or so. Any rain will depart Tuesday evening as the low pressure moves away from the region. A broad high pressure ridge will expand into the Ohio Valley beginning Wednesday and remain through the end of the week. With a predominant E/NE low level flow...expect seasonable temperatures with a nice drop in the humidity levels from what we have felt over the last 10 days or so. Upper level troughing initially midweek will lift out by Friday into the weekend with heights rising. The ridge will center over the Ozarks and lower Tennessee Valley over the weekend with central Indiana on the periphery. Some discrepancies exist between long range guidance... but the most likely scenario at this point is a frontal boundary setting up north of the region over the weekend with just isolated diurnal convection impacting the forecast area as southerly surface flow returns. This front to the north may have a more substantial impact locally by the tail end of the holiday weekend but confidence is low in any specific solution at this time. && .Aviation...(06Z TAF Issuance) Issued at 1144 PM EDT Sun Aug 29 2021 IMPACTS: - Scattered convection should diminish toward sunrise, then more convection Monday afternoon into Monday night. - MVFR fog possible near sunrise, especially at KLAF. DISCUSSION: Scattered convection should weaken overnight. Will include VCTS for the first part of the TAFs, then allow for a lull. More scattered to numerous convection will develop by Monday afternoon and continue into Monday night with a cold front in the area. MVFR or worse conditions are possible in convection. Other than perhaps some brief MVFR conditions in fog near sunrise, VFR conditions are expected for much of the TAF period outside of convection. Winds may become variable during the day Monday thanks to convection and the front in the area. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ Update...50 Short Term...TDUD Long Term...Ryan Aviation...50
Area Forecast Discussion
National Weather Service Louisville KY
940 PM EDT Sun Aug 29 2021 .Forecast Update... Issued at 940 PM EDT Sun Aug 29 2021 In the near term, convection across southern Kentucky continues to drift northward. Over the 15-20 minutes, we`ve seen it start to weaken and gust out. We expect this activity to last for another hour and mainly affect Logan/Simpson/Warren/Allen counties. Some additional showers and storms will continue to move northeast through Adair county and may get into southern Taylor, and perhaps Casey county prior to diminishing. None of the storms are severe, but brief heavy rainfall, some gusty winds, and lightning will be the primary threats. Moving to the overnight period, a surface cold front extending from northern Missouri into central IL continues to move slowly southward. Regional radars show some convection firing along it. Earlier model runs in the day suggested that convection would continue to grow along the front and drift southward overnight, possibly getting into our southern Indiana counties. Much of the guidance has backed off this idea now and really keep the best chances of storms up near the I-70 corridor. Given the relative good short term agreement, will back off PoPs tonight south of the Ohio River, but will maintain at least a slight chance of showers/storms across our southern IN counties. Overnight lows will range from the upper 60s to the lower 70s. Moving into tomorrow, we should start off mostly dry, though I can`t rule out some renegade showers/storms in the morning across the region. Convective activity should increase during the afternoon hours as the frontal boundary to the north pushes down into the region and tropical moisture from Ida works northward into the region. There is a signal in the late afternoon data (Euro and 18Z GFS) that suggest we could see the development of a Predecessor Rain Event (PRE) across portions of the area tomorrow afternoon. A PRE is an organized area of heavy rainfall that develops in connection with water vapor originating in the vicinity of a tropical cyclone, but this area of rainfall is separated from the tropical cyclone by a large distance. In general, PRE`s are difficult for forecast models to predict correctly, but there are several precursors that are being predicted by the models for tomorrow afternoon. We`ll be within the right rear entrance region of a 200 hPa jet, we will be downstream of an approaching 700 hPa trough axis, we`ll have a low-level front approaching from the north and we will be on the periphery of an approaching tropical plume of moisture. Lastly, the 925 hPa theta-e ridge axis is forecast to be east of the area, along the Apps. Indeed, the 18Z GFS, the 12Z Euro, and even tonight`s 00Z HRRR runs suggest that thunderstorms will develop across central/southern Indiana tomorrow afternoon. These storms may slowly drift southward with individual cells moving eastward. This could result in a swath of training thunderstorms. With that plume of tropical moisture advecting in from the south, PWATs should surge above 2 inches. This would result in storms containing very heavy rainfall that could result in localized flash flooding. As noted above, numerical models often struggle with the placement of PREs, but given the pre-cursors outlined above, it stands to reason that we may have a good shot at getting one of these somewhere along and north of the I-64 corridor. As of this writing there is still too much uncertainty to delineate where widespread flash flooding could occur. While I do think the area at most risk is mainly along and north of the I-64 corridor, it remains uncertain if the highest risk will be across southern IN or a little further downstream across SE IN, southern OH, and perhaps into WV. This activity should weaken through the late evening hours, but additional convection associated with the actual remnants of Ida will then move into southern KY and spread northward across the state overnight and into Tuesday. The late afternoon model tends have continued to push the axis of heavier rainfall with the remnants of Ida to the east. This is likely due to the westerlies being a little stronger than earlier predicted which is allowing the center of the system to pass a bit more to our south and east. As of now, the best chances of heavier rainfall still look to occur on Tuesday and continue through Wednesday. The axis of highest QPF looks to favor areas east of a Bowling Green to Lexington line. No headlines will be issued with this forecast. However, if model trends continue to hold, a Flash Flood Watch for portions of the region will be considered on the overnight shift. && .Short Term...(This evening through Monday) Issued at 344 PM EDT Sun Aug 29 2021 Tonight, an approaching cold front, that is currently pushing southeast through southeast Iowa, will continue pushing a line of showers and thunderstorms towards the Lower Ohio Valley. Chances of precipitation will continue increasing across the northern half of the CWA during the overnight hours. This isn`t too exciting by itself, but as the front begins to interact with the remnants of Hurricane Ida, things get more interesting. As the outer bands of Ida push moisture northward, the moisture will fan out along the front and cause moisture to pool. PWATs will climb to around 2.5", and with plenty of instability and warm temperatures, expect efficient rainfall. This will likely result in very high rain rates with thunderstorms along this front tomorrow afternoon. Flooding could become an issue if showers remain over an area too long. Still believe the areas along and north of Interstate 64 are most likely to see these heavier showers. After collaboration with neighboring offices and WPC, we decided against a Flash Flood Watch. Recent dry conditions have caused low river levels and dry soils. Flash flood guidance remains over 3" for 3 and 6 hour rainfalls across many of the possibly affected areas. These will be evaluated during later shifts. Under partly cloudy skies, temperatures will drop into the low to mid 70s with a few rural areas possibly seeing the upper 60s. Tomorrow, clouds continue to build through the day as precipitation increases, but even with the clouds and rain temperatures should reach the mid to upper 80s. .Long Term...(Monday night through Sunday) Issued at 317 PM EDT Sun Aug 29 2021 ...Heavy Rainfall and Minor Flooding Possible Monday Evening into Early Wednesday... Area of showers and storms with heavy downpours Monday afternoon ahead of Ida and south of a cold front draped from northern Missouri through central Illinois to northern Indiana will continue into the evening hours over southern Indiana and north central Kentucky. PWATS over 2" pooling along the length of the lower Ohio Valley along with very weak shear indicates locally heavy downpours can be expected. There is good model agreement among operational runs and ensemble envelopes over the first 72 hours of the forecast period taking the center of Ida through the Tennessee Valley, putting us on the left side of the track, which is typically where the heaviest rain occurs in this pattern. We`ll also be located near the right entrance region of an upper jet streak over the Great Lakes and that east- west front over the Midwest will still be drifting towards us from the north, eventually meeting up with Ida. Soundings show almost no CAPE and continued weak shear as we get into Tuesday and Wednesday with deep warm cloud depths of 13-15 thousand feet. Precipitable water values will continue over two inches, especially south of the Ohio River. There continues to be higher confidence in placement of the heaviest rainfall amounts (storm total Monday evening through early Wednesday morning) than there is in amounts. It still appears that the heaviest rain will fall south of the Ohio River, especially southern and eastern sections of central Kentucky. Recent progs have sped the system up slightly, so where we previously had totals of 4-6" they are now more in the 3-5" range. Still plenty of rain! Also it is important to note that rainfall rate can be just as important, if not moreso, as a flooding threat. If we do realize flooding issues Tuesday-Wednesday it will likely be local flooding from intense rates, and perhaps training, rather than from the overall rainfall totals. One thing that we do have working in our favor is antecedent conditions. While there have been spotty summertime showers and storms with heavy downpours recently, overall we have been on the dry side...especially in the Lake Cumberland region and southern Bluegrass where some of the heaviest rainfall is expected. The Drought Monitor shows some areas of D0 across southern Indiana, extreme north central Kentucky and southern Kentucky. Ensemble river forecasts from the NAEFS and HEFS actually show very little river flooding later this week...with a few spots possibly going into minor flood. Looking at the year as a whole, rainfall has been near to slightly above normal, which has allowed for plenty of green, healthy vegetation that can help to soak up rainfall. So, given all of the above, and after having spoken with surrounding offices, will continue to advertise heavy rain in the forecast but will hold off on a watch for now for the early Tuesday - early Wednesday time period. Of course, each shift will continue to look at things and make decisions accordingly. How much rain we get tomorrow afternoon and evening, and where exactly is falls, will have some bearing on choices regarding watch issuance and placement. ...After Ida... The rest of the forecast looks comparatively quiet as high pressure noses down from Canada and translates to the East Coast. We may start to see another system move in by the weekend...but for now will keep PoPs low. && .Aviation...(00Z TAF Issuance) Issued at 743 PM EDT Sun Aug 29 2021 Scattered convection is ongoing near and ahead of a cold front across Illinois and Indiana, and weakening storms will approach southern IN around 05z tonight. However, do not have confidence TSRA will make it to HNB or SDF before weakening. Separately, ongoing convection near the TN border may sneak into the vicinity of BWG in the first hour of the TAF before storms diminish with sunset. Otherwise, skies start the period relatively clear with increasing clouds associated with decaying convection early Monday. TSRA impacts are much more likely Monday afternoon and evening, especially the northern 3 terminals (HNB/SDF/LEX). Some of these storms will be capable of gusty winds and torrential rainfall. && .Hydrology... Issued at 327 PM EDT Sun Aug 29 2021 The remnants of Hurricane Ida are expected to bring heavy rain to the Ohio and Tennessee valleys through at least Tuesday night and possibly into Wednesday. In addition to local flooding during the heavy rain, minor river flooding may follow the rain for a few days later this week. At this time the forecast calls for 3-5" of rain generally along and south of the Ohio River...with 2-4" possible north into southern Indiana. Today`s 6hr FFG values are 2-4", and 1hr values are 1.5- 2.5". Flash flood guidance numbers are fairly uniform across the area. Those numbers will likely change as we experience shower and thunderstorm activity this afternoon through Monday evening ahead of the main event. It`s also important to keep in mind that flash flood guidance is the amount of rain, over a given time period, that will cause small streams to flood. Locations with poor drainage, low spots, and urban cityscapes may begin to flood at values below flash flood guidance. Fortunately most area rivers are very low as we go into this event. Nevertheless, rivers will have to be watched as this system moves through. Right now the most likely basins to experience heavy rain and potential minor flooding include the Cumberland, Barren, Green, Rolling Fork, Salt, Kentucky, and Licking. Heavy rains are expected in the upper Ohio basin and may cause a reaction in the Ohio River in central Kentucky as the water moves downstream. Contributions from tributaries flowing into the river from the south will add to the overall volume of water in the mainstem Ohio. && .Climate... Issued at 1130 AM EDT Sun Aug 29 2021 The remnants of Hurricane Ida are expected to bring heavy rain to the Ohio and Tennessee Valleys Tuesday, possibly lingering into Wednesday in eastern parts of the region. Daily rainfall records may be in jeopardy. Rainfall Records for August 31: Bowling Green 1.83" in 2017 (ahead of former Hurricane Harvey) Lexington 2.09" in 2013 Louisville 1.21" in 2018 The wettest August day on record at Bowling Green is 3.53" set on the 5th in 1975. The rainfall record for Lexington on September 1 is 2.04" set in 2017 (ahead of former Hurricane Harvey) && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update.......MJ Short Term...KDW Long Term....13 Aviation.....EBW Hydrology....13 Climate......13
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
905 PM EDT Sun Aug 29 2021 .SYNOPSIS... A front stalled near the Blue Ridge Mountains will retreat northeastward as a warm front overnight. A cold front will slowly approach from the Great Lakes Monday into Monday night. This front will stall overhead during the middle of the week as the remnants of Ida approach from the Tennessee River Valley. The cold front and remnants of Ida should move offshore late in the week, giving way to building high pressure for next weekend. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Latest analysis shows a stalled frontal boundary lingering along the Blue Ridge as high pressure remains displaced across the southeastern US. Meanwhile, a weak shortwave continues to push eastward across the CWA this evening. A few earlier showers and thunderstorms across the Alleghenies have dissipated as a capping inversion has developed albeit the decent amount of surface CAPE remaining. More so, areas along and east of the Blue Ridge have been more stable throughout much of the day. The latest HRRR has captured the dying showers quite well and aligns more or less with the current thinking. The stalled boundary will gradually lift northward overnight through tomorrow as a warm front. While general stability should hold throughout much of the overnight hours, some of the HREF/CAMs have spotty showers/thunderstorms redeveloping overnight due to the shortwave advection interacting with the boundary. More so, there remains a theta-E ridge across eastern portions of the area. Thus, do think that there could be spotty showers/thunderstorms that redevelop overnight, but should be rather short lived. Otherwise, expect mostly dry, yet humid conditions overnight with areas of patchy fog developing. Lows expected in the upper 60s to mid 70s. && .SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/... ...PREVIOUS DISCUSSION... A cold front approaching from the Great Lakes will slowly move toward and eventually into the Mid- Atlantic Monday into Monday night. There is uncertainty in the extent of any early morning cloud cover and shower activity, and that will play a role in how unstable it gets and how strong or widespread thunderstorms will become later in the day. There is a bit of a modest enhancement to the flow aloft expected, so storms may have a bit more organization to them. Gusty to damaging winds and a few instances of flooding are possible. By Tuesday, the remnants of Ida will be moving northeastward across the Tennessee River Valley. Meanwhile, Monday`s front will be stalling overhead. This likely sets the stage for scattered to numerous showers and thunderstorms, with the probability of more widespread and potentially heavy rain increasing markedly after midnight Tuesday night. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Please reference the National Hurricane Center for the latest details on the track and strength of Ida. Ida will likely continue to be steered northeast by an approaching trough during the middle of the week. It is becoming increasingly likely that our region will be affected. There is an increasing flood/flash flood risk with a potentially prolonged period of heavy rainfall from showers and thunderstorms Wednesday into Wednesday night. The track will determine the placement, extent, and severity of flooding and/or severe thunderstorm and tornado threats. There is also a threat for tidal flooding depending on the track of the remnants. Mainstem river rises and additional flooding is possible late in the week even after the heaviest rainfall has gone. The remnants` track and intensity is still a bit uncertain. It should be moving away by Thursday. This will set the stage for a couple of refreshing days as Canadian high pressure surges southward. Daytime temperatures will be in the upper 70s and lower 80s with dew points in the 50s. Overnight lows will be in the 50s to around 60, with some 40s possible in the mountains. Return flow may result in a slight warming trend by Saturday, but precipitation is forecast to hold off at this time. && .AVIATION /01Z MONDAY THROUGH FRIDAY/... Generally VFR conditions early this evening under a light southerly flow. However fog is expected to develop mainly after midnight tonight and can be locally dense in nature. Do think fog/low stratus affects the terminals overnight but to what extent is unknown. Have MVFR/IFR CIG/VSBYs in the forecast but am most confident in restrictions at MRB/CHO. Elsewhere, confidence on restrictions remains low. In any case, any fog/low stratus should burn off by 12-13Z with VFR conditions returning. Additional showers and thunderstorms are possible Monday afternoon and evening and Tuesday afternoon, perhaps becoming more widespread later Tuesday night as the remnants of Ida approach. Please refer to the National Hurricane Center for details on Ida. Wednesday`s forecast will depend on the remnants of Hurricane Ida, but heavy rain, thunderstorms, and low ceilings are all possible. Improving conditions should arrive by Thursday. && .MARINE... Generally light flow is expected through Tuesday, though periodic showers and thunderstorms could result in locally gusty winds, higher waves, and lightning strikes. Winds may increase Wednesday into Thursday as the remnants of Hurricane Ida pass through the region, but details remain uncertain at this time. Please refer to the National Hurricane Center for details on Ida. && .TIDES/COASTAL FLOODING... Slightly above normal tide levels persist. While most sites should remain below minor flood stage, anamolies at Annapolis have continued to rise. Observations have followed the CBOFS forecast quite well, which signals Annapolis getting into minor flood stage late tonight. Therefore, have issued a Coastal Flood Advisory just for Annapolis through 06Z. Anomalies should decrease a little for the first part of the week, but increasing southerly winds ahead of the remnants of Ida could result in tidal flooding around midweek. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...Coastal Flood Advisory until 2 AM EDT Monday for MDZ014. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...SOUZA/DHOF NEAR TERM...SOUZA SHORT TERM...DHOF LONG TERM...KLW AVIATION...SOUZA/KLW MARINE...DHOF/KLW TIDES/COASTAL FLOODING...SOUZA
Area Forecast Discussion
National Weather Service Shreveport LA
1006 PM CDT Sun Aug 29 2021 .UPDATE... The first outer rainband associated with Hurricane Ida continues to diminish in strength as it slides westward across the ArkLaTex at this hour. None of the activity in this rainband reached severe criteria, though it was responsible for producing steady rainfall and gusty winds as high as 35 kts. The RAP13 and HRRR agree that this rainband will continue to weaken and should dissipate entirely by 04Z. There is some disagreement regarding rainfall coverage and timing with subsequent rainbands, as the totals will depend heavily on Ida`s track and speed, however the latest guidance is trending towards lowered probabilities of tropical storm force winds and reduced rainfall accumulations, keeping the bulk of the moisture to the east of the Four State Area. Revised PoP grids with the best possible short term compromise through 12Z, maintaining PoPs for the current rainband, and trending values downward for the subsequent waves. Based on the latest trends, the Flash Flood Watch and Tropical Storm Warning have been cancelled, effective immediately. /26/ && .PREV DISCUSSION... /issued 630 PM CDT Sun Aug 29 2021/ AVIATION... Mainly VFR conditions expected across area terminals through the forecast period with the exception of MVFR ceilings possible across MLU beginning late 30/09Z as tropical cyclone Ida moves through western Mississippi. Ida will support elevated north to northeast winds of up to 15 knots with higher gusts on Monday across the MLU/ELD/SHV/TXK terminal sites with lesser values across the east Texas terminals. Otherwise, rainband convection could bring tempo thunderstorms across Louisiana and Arkansas terminals this evening. /05/ && .PRELIMINARY POINT TEMPS/POPS... SHV 76 90 74 96 / 30 50 10 10 MLU 75 80 72 93 / 80 90 50 20 DEQ 73 91 71 94 / 20 30 10 10 TXK 75 90 72 94 / 20 40 10 10 ELD 72 86 69 92 / 50 70 30 10 TYR 75 92 75 95 / 10 10 0 10 GGG 73 92 72 95 / 20 20 10 10 LFK 74 93 74 97 / 20 30 10 30 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...None. LA...Flash Flood Watch through Monday evening for LAZ014-021-022. Tropical Storm Warning for LAZ014-020>022. OK...None. TX...None. && $$ 26/05
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Area Forecast Discussion
National Weather Service Sacramento CA
214 PM PDT Sun Aug 29 2021 .SYNOPSIS... Hot and very dry today and Monday turning cooler through the rest of the week. Gusty southwest to west winds early this week will bring critical fire weather conditions to the northern Sierra and southern Cascades. && .DISCUSSION... GOES-West fire temperature product is showing intense heat signatures associated with the Caldor Fire this afternoon. A brief period of critical fire weather conditions is expected late this afternoon over ridgetops, as trough forms off the Coast. Wind gusts up to 20 mph has been observed so far across the high Sierra and southern Cascades this afternoon. Valley afternoon highs will will range from the upper 90s to around 103, resulting in moderate heat risk. Ensembles and cluster analysis indicate that an upper trough will gradually deepen into mid-week. This will switch the wind pattern to more onshore, which will gradually thin out the smoke the rest of today, especially for the Delta/Southern Sacramento Valley per latest HRRR smoke model. A stronger onshore flow/southwest winds will get going Monday, which should push the smoke eastward out of the Valley and much of the foothills. The deepening trough will bring increasing fire weather concerns to the northern Sierra and southern Cascades early to mid-week. The strongest winds are expected in the afternoon and evening hours. Southwest to west wind gusts of 20 to 35 mph are possible. These winds combined with very low humidity and extremely dry fuels will lead to critical fire weather conditions. A Red Flag Warning has been issued for the northern Sierra and southern Cascades as well as portions of the eastern foothills from 11 AM Monday through 11 PM Tuesday, given the potential for rapid spread of new or existing wildfires. Elevated fire weather conditions may continue into Wednesday due to locally gusty winds and low humidity. Practice fire safety. Highs will remain above seasonal normals through Monday. Then, temperatures will cool back into the mid 80s to mid 90s during the Tuesday-Wednesday timeframe. && .EXTENDED DISCUSSION (Thursday THROUGH Sunday)... Cluster analysis is in good agreement troughing over the region will likely remain in place at the start of the extended forecast period. By early next weekend, some differences emerge in forecast model solutions. There is some indication of a closed low developing, generally located off the Central Coast of California. This could potentially lead to below average temperatures across the region. Interior Northern California could see temperatures 5 to 10 degrees below climatology. Breezy onshore winds are also possible at times in the afternoon and evening hours, particularly through the Delta and higher elevation terrain. && .AVIATION... Areas of MVFR possible due to area wildfire smoke. Gusts 15 to 30 kts vicinity Delta and high Sierra. Elsewhere, winds generally under 12 kts. && .STO WATCHES/WARNINGS/ADVISORIES... Red Flag Warning from 11 AM Monday to 11 PM PDT Tuesday for Burney Basin and Northeast Plateau in Shasta County Including Northwest Lassen NF north of Lassen NP-Eastern Portion of Shasta/Trinity NF-Northern Motherlode From 1000 to 3000 Ft. Includes portions of Nevada-Yuba-Placer-Amador and ElDorado Units-Northern Sierra Foothills from 1000 to 3000 Ft. Includes portions of Shasta-Trinity and Butte Units-Northern Sierra Including Lassen NP and Plumas and Lassen NF/S West of the Sierra Crest (West of Evans Peak-Grizzly Peak-Beckworth Peak)- Northern Sierra Including the Tahoe and ElDorado NF/S West of the Sierra Crest-Southern Motherlode From 1000 to 3000 Ft. Includes portions of Calaveras-Tuolumne Unit-Stanislaus NF West of the Sierra Crest. && $$
Area Forecast Discussion
National Weather Service Las Vegas NV
1216 PM PDT Sun Aug 29 2021 .SYNOPSIS...Hot temperatures and isolated thunderstorms are expected through Monday with Excessive Heat Warnings in effect for much of the region. Moisture will be increasing through the middle of next week aided by the remnants of Nora. This moisture will lead to better chances for shower and thunderstorm activity in Mohave County today, expanding west and north into southern Nevada through mid-week. && .DISCUSSION...Through next Sunday. Typical monsoon pattern expected with storms firing over the higher terrain of Clark, Mohave and San Bernardino Counties into this evening and again Monday afternoon/evening. Gusty outflow winds and brief heavy rain main concern with storms. Did blend in a higher percentage of the camPoPs for the rest of today through Monday. Above normal temperatures persist with an excessive heat warning covering parts of our area through Monday evening. Tuesday afternoon through Wednesday still looks to be our most favorable period for showers and thunderstorms as additional dynamics come into play. Models all show a weak disturbance situated near 30N/120W early Tuesday morning. Stronger trough entering the Pac NW poised to draw this feature inland across the area late Tuesday afternoon through Wednesday. Developing jet streak and associated divergence aloft will provide some additional lift. As for models. GFS and its ensemble members continue to support a wetter scenario for southern Nevada and eastern California with highest QPF values still plotted across northwest Arizona. Believe latest NAM and EC and its members continue to underplay the situation as associated dynamics will be overspreading PW values between 1" and 1.5". WPC Day 3 QPF (5 pm Tue - 5 pm Wed) depicting 0.50"-1.25" for the eastern half of Mohave County. The Colorado River Valley, southern Nevada and eastern California mostly a 0.50" or less. No hydro headlines will be issued with this package as discussed in a collaboration call with WPC and AZ offices. Residual moisture Wednesday night and Thursday will keep additional chances for showers and thunderstorms largely confined to Mohave County, but can not rule out a few storms lingering over eastern Nevada. Mainly dry conditions with temperatures near normal Friday into the Labor Day Weekend. The exception is in Mohave County where lingering moisture could still ignite a few showers and thunderstorms. && .AVIATION...For McCarran...Light winds favoring an easterly direction will remain before giving way to some southeasterly winds this afternoon around 22-23Z. Expect winds around 10-12 knots with some occasional gusts around 15-20 knots lasting through 01-02Z. Thereafter, winds will shift to more of a south-southwest direction, eventually becoming light and variable overnight. Low confidence, but there is a very small chance for an isolated storm to develop just south of the Las Vegas Valley along the McCullough Range which may bring lightning within 15 miles of KHND. Not anticipating any storms to develop in the Las Vegas proper this afternoon, but will be possible tomorrow afternoon. Some FEW to SCT aoa 12 Kft is expected, primarily along the higher terrain this afternoon with more cloud cover possible tomorrow. For the rest of southern Nevada, northwest Arizona and southeast California...Isolated to scattered thunderstorms are possible later this afternoon and again tomorrow across southeastern portions of our region, including in and around the Colorado River Valley. Low confidence on storms impacting KIFP and KEED directly, but vicinity thunderstorms maybe within 15 miles at times both afternoons. Main concern would be strong outflow winds impacting the terminals, potentially bringing gusts up to 30-40 knots. FEW to SCT aoa 12 Kft will be possible in this region. Further north and west, expect light winds following typical wind patterns. Skies will be mostly clear with some FEW aoa 12 Kft across some of the higher terrain in the western Mojave Desert. Although, haze from distant wildfire smoke will reduce slant range visibility at times, especially across the Sierra, western Mojave Desert and parts of the southern Great Basin. Less confident on the potential for smoke/haze to impact KBIH tonight, with some signal of smoke coming in from the north-northeast, the smoke may not make it to the Owens Valley overnight tonight. If it does, the HRRR Smoke indicates it may be more dense, dropping vsbys to around 4-5 SM. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ DISCUSSION...Pierce AVIATION...Peters For more forecast information...see us on our webpage: or follow us on Facebook and Twitter