Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/24/21

Area Forecast Discussion
National Weather Service Albuquerque NM
943 PM MDT Fri Jul 23 2021 .UPDATE... Water vapor shows upper level low over E NM tonight with flow curving around it from the east and northeast over C and W NM where large scale lift exists to support thunderstorm activity. This activity continues to decline both in intensity and coverage so any flash flooding will be due to ongoing runoff. Forecast shows a decreasing trend in PoPs which looks to be on track as dry slow from the east works across C NM and to the west. Upper level low will likely meander and perhaps combine with another low over AZ. This will allow for deeper southerly flow through the atmosphere with plenty of moisture for another round of storms tomorrow. Activity may be focused more over W NM than central but will depend upon how much the atmosphere recovers and becomes unstable again. We will likely need another flash flood watch to cover any flood potential tomorrow as the same areas that got heavy rainfall and flooding today will probably have it tomorrow. WPC keeps slight to moderate excessive rainfall outlook over W/SW NM which makes sense given the trends with the upper low and antecedent conditions. 39 && .PREV DISCUSSION...557 PM MDT Fri Jul 23 2021... .AVIATION... 00Z TAF CYCLE Area radar are busy this evening with scattered to numerous storms over much of central and western NM. Water vapor imagery shows upper low over Santa Rosa NM with the bulk of the storms on the west side of that low. This low will continue to be supportive of storms through the next 24 to 36 hours which will make timing convective events at terminals a challenge. HREF has upper low slowly moving west towards AZ putting NM in a more favorable southerly upper level flow and PWAT supportive of convection. KGUP/KFMN...Will need to monitor for storms the next 3-6 hours as storm motions will be towards these terminals. Hi-res models have decent handle on storms affecting these sites this evening. Once storms clear...several guidance including GLAMP show ceilings dropping to MVFR for KGUP through the morning hours. Another round of storms again tomorrow afternoon. KSAF/KLVS...Storms impacting KSAF now through the next few hours and then clearing up. KLVS should be east of the storms and not have any impacts through the night. Look for storms to initiate again tomorrow around 18Z but could be as early as 16-17Z. KABQ/KAEG...thinking TSRA are done for the evening hours so will keep TAFS VFR. Concerned HRRR runs showing activity beginning in the late morning hours so have mention of VCSH at 17Z. Just have little confidence as it will take some time for the atmosphere to recover from today`s convection. Given the upper low and day time heating that is possible, but may take more heating for it to happen. Hopefully newer guidance for 06Z TAF will provide more confidence. KTCC/KROW...terminals should stay VFR. HREF shows most of the convection over C and W NM with maybe an isolated storm in spots of E NM so confidence is low in any storms affecting these terminals. 39 && .PREV DISCUSSION...336 PM MDT Fri Jul 23 2021... .SYNOPSIS... With a low pressure system moving westward across the state, combined with abundant low-level moisture, the threat for localized heavy rainfall and flash flooding will be a concern through Saturday. These storms will be mainly focused along and west of the central mountain chain. Heading into Sunday, storm coverage will begin to decrease through next week, but daily rounds of showers and thunderstorms will still continue through next week. && .DISCUSSION... SHORT TERM...(TONIGHT THROUGH SATURDAY NIGHT)... Lots going on this afternoon with severe weather and flash flooding in central areas and storms now developing in the west. Expect more in the way of severe weather and flash flooding well into tonight. This is thanks to the upper low in eastern NM. It is helping to produce high PW values, up to 2000+ Capes, -7 LI`s and effective bulk shear up to 40 knots, promising a busy period into tonight. The upper low will trek across the state tonight into Saturday, then it will turn southwest into into AZ later Saturday and Saturday night. We will continue with the Flash Flood Watch currently in effect for all of western and central NM through tonight. We will issue another Flash Flood Watch for Saturday into Saturday night with this package for a smaller area of our west and southwest zones. These areas will still be impacted by the upper low. Elsewhere scattered to numerous showers and storms will occur, expect the far eastern plains where activity will be isolated, and possibly rain free in Curry and Roosevelt Counties. The threat for severe weather will be less Saturday as we lose the shear component. LONG TERM...(SUNDAY THROUGH FRIDAY)... By Sunday, the upper-level low will have scooted westward over Baja California. Meanwhile, the high will elongate and shift north into CO/WY. Drier air will begin to work its way into the northern part of the state, leading to a downtick in storm coverage for Sunday. On Monday and Tuesday, the high makes a trek southeastward into Kansas/Nebraska, with scattered storms focusing over western and central areas. The flow becomes more favored for east-southeast steering flow. Wednesday and Thursday feature even less convection, as the high remains over the Great Plains and continues to bring in drier air. Temperatures will gradually rise in most areas of the state as the high strengthens. Despite the highs placement, a traditional monsoon stream of moisture does not seem to materialize. Compared to yesterdays 12z models with the immobile high to our northeast, the 12z GFS and ECMWF are now in decent agreement that the high meanders back to the west and tries to re-station itself over the Four Corners region by late next weekend. CHJ/31 && .FIRE WEATHER... Heavy rain from thunderstorms will produce widespread wetting rain, some of it heavy, producing an inch or more of rain in 30 minutes, and large hail is also possible through this evening. This weather is thanks to an upper low over eastern NM. It will move across the state well into tonight with more soaking rain and potential flash flooding. With the upper low moving into AZ, Saturday should not be as active, aside from the Northwest and West Central Highlands closest to the low, where widespread wetting/soaking rains are likely. High pressure to our east will move toward NM late this weekend and early next week. The high will shift back east Tuesday and beyond and strengthen. We will see a subtle decrease in storm activity Sunday through much of next week, but overall it will still be relatively active. CHJ && .ABQ WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch until 6 AM MDT Saturday for the following zones... NMZ201>204-210>226. Flash Flood Watch through Saturday evening for the following zones... NMZ205>209-241. && $$
Area Forecast Discussion
National Weather Service La Crosse WI
1054 PM CDT Fri Jul 23 2021 .UPDATE... Issued at 942 PM CDT Fri Jul 23 2021 A complex weather pattern unfolding over the regional tonight with overall weak forcing. At 9 pm, broad southerly flow continued to hold dewpoints in the low 70s across the area. The cold front to the northwest is slowly becoming more organized along a KINL- KABR-KRAP line with northwest flow clearly behind it...and lower dewpoints. Warm frontal convergence over northern MN erupted storms several hours ago which are moving southeast near Duluth at this time. Over South Dakota, weak shortwave trough energy is trying to organize instability with a fair amount of warm air aloft limiting mid-level lapse rates to 6.5C per SPC mesoanalysis. These lapse rates are widespread over the entire pre-frontal region. MUCAPE is out there in 2-4k J/Kg range but most is elevated and the analysis seems a bit overplayed for the lapse rates in place. To boot, the wind shear across the area is poor and little storm organization is expected. The main rain chances overnight will come from weak shortwave trough energy oozing east now causing precipitation across South Dakota. Cloud tops and lightning activity continues to show development. There should be enough weak forcing with the SD trough, cold front, and elevated instability evolving eastward to keep a likelihood of showers and sct storms north of I-90 for the 3-9 am period. The HRRR model run-to-run consistency has been giving and taking all night so the lesson seems to be concentrate on the bigger picture forcing and instability. Consistent signals have been in the energy emanating out of SD and observational data supports this. The Duluth convection may clip northcentral WI as well. Overall, updated the northern rain chances to 80 percent and increased the rainfall amounts. Rain chances still fall southward but have increased the I-90 corridor for light rain in the 50-60% chance range. Storms should be garden variety overnight and no severe thunderstorms are expected. && .SHORT TERM...(This evening through Saturday) Issued at 210 PM CDT Fri Jul 23 2021 Latest water vapor satellite imagery shows shortwave ridging over the Upper Great Lakes region. Subsidence underneath ridge is allowing for mostly sunny skies per visible satellite imagery. Temperatures have warmed into the middle to upper 80s per latest 18z metars. Tonight...Shortwave trough over the Northern Plains states is expected to track across northern Wisconsin and the Upper Peninsula of Michigan. The latest 23.12z NAM/GFS/RAP increase moisture transport/convergence this evening and tonight across the northern half of the forecast area. Showers/storms are expected to develop in association with the shortwave trough and move across mainly the northern half of the forecast area. The latest 23.12z NAM/23.16z RAP show 20 to 25 knots of 0-3km shear and 0-6km Most Unstable CAPE of up to 1500 j/kg across the far northern parts of the forecast area. A few of the storms will be strong to severe with damaging winds the main threats. Locally heavy rainfall is also precipitable water values approach 2 inches. The shortwave trough and associated cold front push southeast and east of the forecast area by 18z Saturday. The 23.12z GFS/NAM suggest warmer air aloft advects into the forecast area behind cold front with 925mb temperatures warming to plus 26 to plus 28 degree celsius by 21z Saturday. The 23.00z NAEFS show plus 1 to 2 degrees standard anomalies across the forecast area. High temperatures are expected to rise into the upper 80s to middle 90s at most locations. The combination of dewpoints in the lower 70s or 70...heat indices will be 95 to 105 across much of the forecast area. .LONG TERM...(Saturday night through Friday) Issued at 210 PM CDT Fri Jul 23 2021 The main weather story in the extended will be the very warm to hot temperatures through Wednesday with periodic rain chances. The 500mb pattern has the forecast area in northwest flow aloft Saturday night through Friday. This puts the regional vulnerable to shortwave troughs that move through the flow, however there are no real high confidence periods where widespread soaking rains forecast. Periodic rain chances occur starting Sunday night. The GEFs plumes are quite dry and generally a half an inch or less for both KRST and KLSE through the end of July. The EC EPS is similar. They both have some outliers with wider spread starting next Thursday night. Temperatures during this prolonged period are not expected to be record-breaking, but still above normal. Highs Sunday through Wednesday should range from the lower 80s to the lower 90s and in the 80s still for Thursday and Friday. We expect a break in the high humidity Sunday and Monday, however dewpoints climb again Tuesday and Wednesday. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 1053 PM CDT Fri Jul 23 2021 Convection has developed this evening over South Dakota along a surface trough ahead of an incoming short wave trough. All the hi-res meso-scale models suggest this activity will hold together overnight as it moves east toward the area. There should be some weakening of the activity as it moves past the best instability gradient and into the mid-level warm air in place over the region. This should result in mainly showers with some embedded thunderstorms probably impacting both airports, with the chances a little bit better for KRST than KLSE. Will throw in a short tempo group with some MVFR conditions at KRST while holding with VCTS and VFR at KLSE for now. Once this activity moves past in the morning, VFR conditions should return and then remain through Saturday evening. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ UPDATE...Baumgardt SHORT TERM...DTJ LONG TERM...Zapotocny AVIATION...04
Area Forecast Discussion
National Weather Service Columbia SC
1033 PM EDT Fri Jul 23 2021 .SYNOPSIS... Drier weather is expected for the weekend, as seasonally low PWs work into the region. By Monday, PWs are expected to gradually increase ahead of an approaching cold front. Scattered to numerous showers and thunderstorms are then expected from Monday through Wednesday evening. Uncertainty then develops by Thursday and Friday. Temps will be near normal - highs in the 90s and lows in the 70s. && .NEAR TERM /UNTIL 8 AM SATURDAY MORNING/... High pressure continues to ridge into the area from the north with low level ENE flow and mid level NW flow leading to drier air moving over the forecast area as PWATs in the northern forecast area have dropped to below 1.5 inches. Surface trough over the Upstate with a sliver of higher moisture developed some isolated convection this evening but by after sunset, any lingering showers or storms are expected to dissipate. Lows a bit cooler tonight, dropping into the upper 60s and low 70s. && .SHORT TERM /8 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... The short term period is looking fairly benign, and should set up for a really nice weekend across the CWA. General troughing is expected to continue dominating the eastern US, and with that will be a surface high pressure influencing the region. This will move eastward from the Ohio Valley into the Atlantic by Sunday, but will help to push some lower (1.3-1.5") PW air into the region for Saturday. Additionally, flow will be weak throughout the atmosphere, with backing wind profiles in model soundings indicative of weak cold air advection. Overall, I can`t rule out a weak/isolated shower Saturday, especially across our northwestern counties. One fly in the ointment to a beautiful forecast would be the presence of haze from smoke. HRRR-smoke products push the smoke westward tomorrow, but I wouldn`t be surprised if more stayed around the area given weak atmospheric flow. Either way, highs look seasonal - in the lower 90s most places. Overnight, lows should be a bit below guidance with lower dewpoints across the area. Expect lows in the upper 60s to around 70. Sunday looks to be more of the same, albeit with some increasing moisture. Ensemble guidance continues to suggest low chances of instability developing, and forecast soundings fall in line with that as well. Without any obvious forcing mechanisms in place, Sunday should be another benign day. Highs will be a touch warmer as heights rise a bit, topping out in the low and mid 90s. Overnight, lows should be back to where they have been with higher surface dewpoints returning. Expect low 70s. && .LONG TERM /MONDAY THROUGH FRIDAY/... Little has changed with the long term period over the last day or so, with the exception of some increased uncertainty with the pattern towards the end of the period. Overall, it looks seasonal with regards to temperatures and rain chances. By Monday, PWs will begin increasing again as heights rise slightly and southerly and southwesterly flow increases. This will be ahead of a cold front that will drag through the region during the week. Troughiness is expected to follow this in the eastern US through Wednesday/Thursday as shortwaves reinforce the parent trough over the Northeastern US. Some uncertainty develops with how this evolves towards Friday as some ensemble members show a more amplified trough by the end of the week, which would change the forecast. Will side towards an expectation of rising heights during this time. Sensible weather will be very seasonal. Monday will be quite warm with slightly rising heights and southwesterly flow ahead of the front. Some isolated showers & storms may keep this in check, but I`m expecting mid 90s everywhere. Tuesday-Wednesday looks active, with widespread showers and thunderstorms developing along the front. Ensemble guidance indicates >70% chances of 1000 j/kg of CAPE developing both days, giving confidence that we`ll see numerous storms develop both days. This should limit overall high temps a bit, and I`m going slightly below guidance. There is a good bit of uncertainty on Thursday and Friday, owing to pattern evolution questions and uncertainty about where the front will eventually set up. I really don`t think the front will push through the area, and expect at least scattered shower/storm chances to remain. Highs will continue to be in the 90s throughout the week, with lows in the 70s. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... Visibility has been reduced a bit due to haze/smoke from the Western U.S. wildfires. As the upper trough along the eastern seaboard shifts east tonight, the smoke may diminish. The trend in LAMP guidance has been less fog/haze early Saturday morning with MVFR just before sunrise. HRRR Smoke product continues show some smoke across the area producing hazy conditions overnight with vsby improving from east to west beginning around 06z. Will continue mention of MVFR at AGS 09z-12z due to persistence. Mostly clear skies overnight as surface high pressure ridges in from the north. Scattered cumulus with bases 4kft to 6kft expected to develop Saturday afternoon. Winds will be E/SE 10 kts or less. EXTENDED AVIATION OUTLOOK...Early morning restrictions possible at fog prone sites AGS/OGB. Scattered showers and thunderstorms Tuesday and Wednesday as a frontal system moves into the area. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$
Area Forecast Discussion
National Weather Service Cheyenne WY
442 PM MDT Fri Jul 23 2021 .SHORT TERM...(This evening through Sunday) Issued at 221 PM MDT Fri Jul 23 2021 Latest radar/satellite loop was showing the frontal boundary continuing to surge south across northeast Colorado and recently exited the southern Nebraska panhandle. Behind this boundary convection has continued to develop along and just behind the boundary. However, this convection has been fizzling out across south of the CO/WY border during the last hour or so. A couple of possible reasons for this convection deteoriating is due to a warm nose aloft and limited cape depicted by the HRRR and local soundings. In addition, we are also seeing a cirrus shield over Laramie County. This cirrus shield may keep things capped for a little while longer, but still cannot rule out some isolated thunderstorms developing mainly along and south of a Laramie to Scottsbluff line late this afternoon and early this evening with lighting and heavy rainfall being the main threats. Otherwise, we will see showers and thunderstorms clear out fairly quickly after sunset. Cannot rule some patchy fog in the North Platte River Valley tonight, but most places will be partly to mostly cloudy with a broad swatch of mid and high clouds across southern Wyoming. The precipitable water values will be quite a bit less tomorrow over areas mainly over the southern half of our forecast area, due to good subsidence building in behind the shortwave. We will need to keep our eyes on another shortwave transversing across southern Montana and northern Wyoming tomorrow. This feature may trigger some scattered thunderstorms over the northern sections of our forecast area. For now, we are continuing to favor a downward trend on the thunderstorm chances. Saturday night and Sunday will see the upper level ridge continue build over the area which will tend to suppress any convection lower the precipitable water values along with a return of warmer temperatures. .LONG TERM...(Sunday night through Thursday) Issued at 230 AM MST Fri Jul 23 2021 The medium range models/ensembles are in good agreement with the building of the upper ridge (~597 dm) over the Central Rockies next week. Monsoonal moisture will be suppressed early in the week, but return by the middle of the week as the ridge drifts east into the High Plains. Expect dry conditions Monday. Isolated to scattered mainly diurnal showers and thunderstorms are forecast Tuesday through Thursday. The severe weather threat will remain low due to weak shear. Locally heavy rain will be possible east of the Laramie Range with precipitable water values around an inch. Well above normal temperatures are forecast early in the week with 700 mb temperatures between 16 and 20 degrees Celsius. High temperatures Tuesday and Wednesday will range from the lower 90s to lower 100s. A weak backdoor front will push into the plains Thursday lowering high temperatures into the lower and mid 90s. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 439 PM MDT Fri Jul 23 2021 Cold front well south in Colorado this afternoon has kept much of the monsoonal moisture south of us. Pretty stable air over southeast Wyoming and Nebraska thunderstorms look to be minimal tonight. VFR conditions overnight. && .FIRE WEATHER... Issued at 221 PM MDT Fri Jul 23 2021 The upper level ridge is expected to continue to dominate the area this weekend into early next week. This will allow for low afternoon humidities (15-25 percent) and high mixing heights around 8-12kft. Wind speeds will remain fairly light and variable. A subtle pattern change is expected at the end of the week as the upper level ridge slides southeast into the central Plains and brings deeper moisture and northwest upper level flow which may favor better precipitation chances. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...REC LONG TERM...MAJ AVIATION...GCC FIRE WEATHER...REC
Area Forecast Discussion
National Weather Service Des Moines IA
804 PM CDT Fri Jul 23 2021 .UPDATE... Issued at 804 PM CDT Fri Jul 23 2021 A warm and humid, but quiet evening is in store across the region. With some residual smoke around, some locales are likely to see a vibrant sunset. Temps are still running in low to mid 80s, as of 8pm with dewpoints ranging from the upper 60s to lower 70s. Keeping our eye on a few features attm. First - showers and storms are ongoing across portions of SD into far western MN. Still expecting a weakening line of showers and isolated thunderstorms to dribble into northern Iowa very early on Saturday morning /3am- 6am/. No severe weather is expected, although a few of these higher based cells could produce gusty winds. Most areas will pick up only very light amounts of rainfall. Second - decided against any expansion of the Heat Advisory at the moment. Current forecast of 95F at KDSM is on the high side of temperature guidance envelope on Saturday, and expecting a fair amount of clouds around so we might even be a touch too high. The one caveat is dewpoint pooling ahead of the front. Currently forecasting Tds from 70-75F which appears reasonable. However, if more widespread mid 70s show up - we could then approach heat indices around 105F. The midshift will have one more look tonight in case of drastically different trend. && .DISCUSSION.../Tonight through Friday/ Issued at 237 PM CDT Fri Jul 23 2021 Key Points: -Heat and humidity settles across the area this weekend through the upcoming week. Peak heat this weekend will occur Saturday with a Heat Advisory in effect over southern Iowa. -Spotty chances for convection Saturday morning, then perhaps Monday and Thursday, though impacts remain fairly low Details: Smoke from wildfires across western portions of North America continues to create hazy skies over Iowa and especially eastern Iowa, as seen on GOES-East true color imagery this afternoon (or taking a peek out the window). Latest HRRR runs indicate that this higher concentration of smoke aloft should clear the area overnight, with better - albeit still slightly hazy - conditions on Saturday. Overnight a shortwave trough will traverse the ridge with a weak line of precipitation to move across northern Iowa in the early morning hours. Better forcing remains north of the area, however a broken line of showers or perhaps thunderstorms will still travel across northern counties. CAM guidance remains mixed regarding whether activity will be squashed by midday (HRRR, ARW, Fv3, RAP) or progress into central and southern Iowa later in the afternoon (NAMnest, NSSL-WRF). For now have sided with majority and kept the afternoon precipitation chances fairly low since forcing remains weak and may struggle to overcome the cap. Of greater concern Saturday is the heat as afternoon temperatures climb into the mid 90s and dewpoints sit in the low 70s. Heat indices, especially across southern Iowa, will top out around 100- 105 so a Heat Advisory remain in effect Saturday across southern Iowa. Hot and humid conditions settle in through the upcoming week thanks to a western US ridge that doesn`t budge much. Heat is expected to peak again this Wednesday when high will reach the upper 90s and dewpoints will likely be in the 70s area-wide. The forecast remains fairly subdued outside of heat impacts. there is a window for precipitation on Monday as another shortwave moves across the area, however models struggle with timing and placement of this system. The airmass certainly supports more than sufficient instability and shear is around 30-40 kts, however with a cap in place convection may struggle. Any storm that does manage to get going would certainly have severe potential. Following that the next window for precipitation at this time appears to be Thursday though details are fuzzy at this time frame. && .AVIATION.../For the 00Z TAFS through 00Z Saturday evening/ Issued at 618 PM CDT Fri Jul 23 2021 Mainly VFR conditions are forecast this period. Plume of thicker mid/upper level smoke continues to push ewd with mostly clear skies this evening. A weak frontal boundary currently extending from SD into MN will slowly sag swd into IA overnight. A weakening line of showers and thunderstorms is expected to impact northern Iowa, including KMCW and possibly KFOD. Cloud bases should remain VFR with only brief/transient reductions to visibility possible. Otherwise, the remainder of the area will just see periods of mainly mid-level cloudiness. There is a low probability of a few thunderstorms developing across southeast IA Saturday afternoon, but highest threat is east/south of KOTM. Southwest winds will shift n/nwly behind the front by Saturday evening. && .DMX WATCHES/WARNINGS/ADVISORIES... Heat Advisory from noon to 8 PM CDT Saturday for IAZ062-073>075- 081>086-092>097. && $$ UPDATE...Fowle DISCUSSION...Hagenhoff AVIATION...Fowle
Area Forecast Discussion
National Weather Service Grand Forks ND
1007 PM CDT Fri Jul 23 2021 .UPDATE... Issued at 1005 PM CDT Fri Jul 23 2021 Cluster of thunderstorms along the ND/SD border near Eureka/Ashley moving east...some earlier wind reports of 55-68 mph in the Linton/Wishek area. Seems a bit less now. Hail threat seems greatly diminished though attm. But will watch these as they move east. In general with 500 mb wave moving thru general support for some shower and t-storms eastward thru far SE ND and eventually WC MN overnight. border thru 06z. && .SHORT TERM...(This afternoon through Saturday night) Issued at 320 PM CDT Fri Jul 23 2021 Short term weather impacts include potential for scattered severe thunderstorms this afternoon and evening, with near critical fire weather conditions possible Saturday. Surface trough axis has acted as a focus for early thunderstorm development this afternoon, with high Td values in the 70s along/east of this supporting ML CAPE 1500-2000 J/KG and heat index values near 100F. Weak forcing associated with subtle waves within mid level westerly flow and PWATs 1-1.5" are supporting isolated to widely scattered activity this afternoon. Main period of forcing is still this afternoon with the main frontal passage, but at that point there is potential that Td values will be decreasing along with instability lowering potential severe threat between the trough axis and frontal zone as this transitions east. Latest trends in HRRR has picked up on this showing weakening trends in coverage/intensity by 00-01Z. Due to at least elevated instability and better forcing though I wouldn`t want to rule out original CAM solutions supporting clusters forming during the evening hours. Effective shear 30-40kt and straight hodographs clouds support supercells/splitting, but due to weak low level shear/higher bases tornado threat is limited (though can`t be ruled out). Primary threats in this environment will tend to be damaging winds to 75 mph/hail to 1.75". PWATS 1-1.5" and slower storm motions along surface boundaries does raise the possibility for localized heavy rain/excessive rain threat. Rest of tonight-Saturday: After the cold front passes there will be a slight drop in temps aloft but a much greater change in Tds and drier/stable air aloft. While westerly BL flow keeps above average temps in place it will tend help scour out any smoke and HRRR smoke model keeps smoke out of our area (possibly the most clear conditions we`ve had in weeks at the surface and aloft). Sunny skies and westerly BL flow will support efficient mixing and potential for temps in the lower 90s, RH values in the 20-30 percent range, and gusty winds 20 to 35 mph (highest mixing potential in northeast ND). This raises the possibility for near critical fire weather conditions across the region. The best chance for critical fire weather conditions will be dependent on rain this evening and winds within or west of the RRV. .LONG TERM...(Sunday through Friday) Issued at 320 PM CDT Fri Jul 23 2021 Summary... Upper level ridge in the south west and southern United States continues to take hold bringing hot conditions. Troughs move up and over the ridge through the early and middle part of the week increasing the chances for showers and storms. Near the end of the week ensembles hint at the ridge moving eastward pushing the track of the troughs further north bringing drier and warmer air into the region. The week ahead... Conditions look to be dry throughout Sunday, with temperatures in the upper 80s to lower 90s. RH values remain fairly low in the 30s, with winds on the lighter side. Warm and dry conditions provide elevated fire concerns for the afternoon, but not as elevated as Saturdays impact since winds will be on the higher side. As we head into the early part of next week another trough makes its way up and over the ridge out in the south west. The frontal boundary associated with the trough encounters CAPE values in the 1500-2000 j/kg range. Moisture flow turns more southerly allowing for a stream of higher dew points into the 60s toward our area. Taking a look at ensemble soundings shear has been decent in both directional and speed components through multiple runs. Effective shear in the low and mid levels are around 25-35kts. Lapse rates look decent, but very between different ensembles bringing low confidence in that category. The exact timing of the system is different between runs, with some bringing the trough through early eliminating the daytime heating ingredient which is a key component in initiating storms. Precipitation amounts of exceeding 0.1 inches continue to lie between 40-60% for western MN and eastern ND. Continued chances for precipitation and storms are possible mid week before the ridge begins to push further east increasing heights and tracking troughs further north. This would bring drier conditions and a continuation of the heat. Temperatures through the long term remain consistent with highs in the upper 80s to lower 90s. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 718 PM CDT Fri Jul 23 2021 VFR expected thru the pd as skies clear overnight/Sat AM and winds turn more west to northwest all areas. Sct tstorms remain psbl but most likely not impact any TAF sites after 02z. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ UPDATE...Riddle SHORT TERM...DJR LONG TERM...Spender AVIATION...Riddle
Area Forecast Discussion
National Weather Service Green Bay WI
753 PM CDT Fri Jul 23 2021 Updated aviation portion for 00Z TAF issuance .SHORT TERM...Tonight and Saturday Issued at 236 PM CDT Fri Jul 23 2021 The latest RAP analysis and satellite/radar imagery show a rather ill-defined warm front extending across northern Minnesota and northeast Wisconsin early this afternoon. Northeast of this front, winds are southeast off Lake Michigan, which is setting up a weak convergent zone over northeast WI with the prevailing southerly flow. Mixed layer instability is 600-1000 j/kg, but it is yet to be seen if convergence is strong enough to produce a shower or storm given mid-level shortwave ridging overhead. Will leave a slight chance in the forecast. Also added a chance to far north- central WI where a cell developed just south of Bayfield. Further west, a prefrontal trough extends across the northern Plains into eastern Manitoba. As mid- level height falls overspread this region, thunderstorms are expected to develop during the middle to late afternoon hours along this trough before spreading southeast into the area late tonight. The severe weather chance with these storms is the main forecast concern. Tonight...If any storms develop this afternoon near Lake Michigan, they should fizzle relatively quickly this evening. Given the weak forcing, don`t think a strong or severe storm is possible. Then attention turns towards the potential for severe storms as they move in from the northwest towards late evening or overnight. The cams/href indicate a slower arrival of the strongest convection, most likely after midnight, although could have a few cells popping up over north-central WI ahead of the main line. The slower timing reduces the severe threat somewhat and consequently, SPC lowered the threat from a slight risk to a marginal risk over north-central WI. In general, storms will be undergoing a gradual weakening trend as they move southeast across northeast WI overnight. Most unstable capes of 1000-1500 j/kg and effective shear to 25 kts will lead to an isolated severe threat over north-central WI as the storms arrive overnight. Damaging winds will be the main threat. Otherwise, it will be a warm and muggy night with lows ranging from the upper 60s to lower 70s. Saturday...Thunderstorm activity will be ongoing at the start of the morning from northeast to central WI. It will continue to weaken through the morning hours, possibly dissipating or exiting by the end of the morning. The surface cold will trail the convection and will move across northeast Wisconsin during the afternoon. Thunderstorm and severe weather chances along the front will be conditional in the afternoon, dependent upon the duration of thunderstorm and resultant cloud cover left over from the morning. The later arrival of the precip tonight will not help thunderstorm redevelopment in the afternoon, but perhaps a few hours of clearing could occur, resulting in instability in the 2500-3000 j/kg range according to models. This instability coupled with deep layer shear of 35-40 kts could lead to severe storms if sufficient heating occurs. Highs will range from the middle 80s to lower 90s. .LONG TERM...Saturday Night Through Friday Issued at 236 PM CDT Fri Jul 23 2021 The main forecast concern will be the potential for severe thunderstorms toward the middle of next week. Weak high pressure will dominate the region for the end of the weekend and the early part of the next work week, with mainly dry but very warm weather expected. A warm/stationary front will bring a renewed chance of thunderstorms Monday night into Tuesday night, with a cold frontal passage occurring sometime Wednesday into Wednesday night. Through this period, strong daytime instability (CAPE 2000-3000+ j/kg) and strong deep layer shear (35-50 knots) will be supportive of organized severe thunderstorm development, though confidence is low in the timing and coverage. CIPS analogs (centered on 00z 7/28) support the threat. After the cold front shifts south, Canadian high pressure will bring mainly dry conditions for Thu/Fri, along with less humidity and temperatures closer to normal. && .AVIATION...for 00Z TAF Issuance Issued at 753 PM CDT Fri Jul 23 2021 VFR conditions will prevail at least through about 06Z with occasional patches of mid-level clouds drifting southeast across the forecast area. A few isolated showers and thunderstorms may also develop near the UP/WI border during the evening hours with some brief MVFR CIGS/VSBYS. After midnight a complex of thunderstorms over northcentral Minnesota will gradually work its way into far northcentral WI and central WI after midnight. Latest shorterm model guidance suggests this complex of storms will eventually work its way SE across the remainder of the forecast area through the early morning hours, and eventually exit eastern Wisconsin by mid- morning Saturday. Confidence remains low on exactly how the convection will evolve during the early morning. Central and northcentral TAF sites will likely see few hours of MVFR CIGS and VSBYS with the thunderstorm activity. The storms will be strongest across central Wisconsin before weakening as they move into eastcentral Wisconsin after daybreak. Additional shower and thunderstorms are possible by early afternoon over eastern WI associated with cold frontal boundary passage, but this will be conditional on how quickly the atmosphere can recover from earlier storms. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM.....MPC LONG TERM......Kieckbusch AVIATION.......ESB
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1044 PM EDT Fri Jul 23 2021 .SYNOPSIS... Air quality should improve somewhat over the weekend while afternoon showers and thunderstorms increase in coverage and intensity through Monday. A backdoor cold front builds into the forecast area early next week, bringing more active weather at least through Tuesday. && .NEAR TERM /THROUGH SATURDAY/... As of 1030 PM: Still a few cells popping up near the escarpment and across the western Upstate, but not as much coverage as earlier runs of the HRRR and NAMnest were advertising. The current forecast looks largely on track. Did bump up sky cover a little bit to line up with trends. Otherwise, no changes were needed with this update. Isolated showers may linger well into the night, especially in upslope areas, as a moist, low level southerly flow continues. This flow may also help low clouds to develop near or just after sunrise. Mountain valley fog and stratus is expected once again. Lows will be near to slightly above normal. Heights rise slightly through the period in the northwesterly flow aloft as a short wave ridge moves over behind a departing trough. Guidance generally agrees on a lee trough developing and some weak upper divergence moving through despite the slight increase in heights. The guidance disagrees on the resulting coverage of convection. They do agree that the mountains have the best chance, but some guidance moves the convection off the mountains and across the Piedmont during the late afternoon. Others show only isolated to low end scattered across the Piedmont. Have gone with the guidance blend which favors the mountains and foothills, with less coverage over the Piedmont. Highs will be near to slightly below normal. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... As of 145 PM EDT Friday: With a 500mb ridge entrenched over the western CONUS, Sunday`s opportunity for synoptic forcing will be severely restricted. A Bermuda high over the western Atlantic will help to maintain southerly surface flow...which in turn will help PWATs ramp up to near 2" by Monday afternoon. A deep 500mb trough will spread eastward, though the best DPVA will remain well north of our CWA. Global models at least indicate some enhanced QPF response starting Sunday night and extending through Monday evening, ahead of a slowly-advancing cold front swooping in from the north. PoPs on Sunday afternoon are largely restricted to slight/chance in the mountains and foothills, as points east appear to be increasingly well-capped in model soundings, which should inhibit widespread coverage of convection despite modest SBCAPE of 500-1000 J/kg. Monday afternoon should fare somewhat better as increased moisture content, lowered LFCs, and less-stable profiles allow for more scattered showers and embedded thunderstorms to crop up ahead of the advancing front. Activity gradually winds down late Monday night into Tuesday morning, as the front attempts to clear the region. For now, have lowered temps a degree or so to more closely match the latest guidance, which seems to be trending toward slightly cooler temps for the next few days. This does little to offset the unseasonably warm temps forecasted for the weekend. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 200 PM EDT Friday: Upper ridging continues to dominate the western half of the CONUS. Following Monday night`s frontal passage we should at least see some improvement in air quality, as the intrusion of continental air clears out any residual low-level smoke/haze in the area. There`s a good bit of uncertainty in the forecast following this fropa, however, as the models haven`t yet reached a consensus on whether the front clears the Carolinas entirely or stalls for a bit. What`s clear is that the Bermuda high refuses to budge, and as such we should retain our diurnally-driven afternoon convection on Tuesday and Wednesday afternoon - something that the presence of a stalled boundary might work to enhance. Late week may feature the arrival of another robust midlevel trough, which would drive a wave of renewed precipitation by Friday afternoon. Expect temps to remain at least a few degrees above normal throughout the medium range forecast. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... At KCLT and elsewhere: Scattered showers and tstms will continue into the evening near the Blue Ridge escarpment, so VCTS will be carried at KAVL/KGSP/KGMU for the first few hours of the 00z TAFs. From there, showers may linger, but overall coverage should diminish overnight. Another concern will be how much fog and low stratus develops outside the usual mountain valleys. For now, think the TAF sites will be mostly VFR outside any precip. Greater coverage of convection is expected Saturday, with the usual diurnal trend of starting in the mountains, and then expanding/drifting E/SE into the Piedmont by early evening. Going with PROB30 for all sites for TSRA. Winds will be light thru the period, generally out of the SE to SW. Outlook: Diurnal thunderstorm chances will steadily increase through early next week. Early morning fog or low stratus will be possible each day, primarily in the mountain valleys. Confidence Table... 02-08Z 08-14Z 14-20Z 20-00Z KCLT High 100% High 100% High 100% High 100% KGSP High 100% High 95% High 95% High 100% KAVL High 93% Low 44% High 100% High 100% KHKY High 100% High 100% High 100% High 100% KGMU High 100% High 97% High 93% High 100% KAND High 100% High 97% High 95% High 100% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables are available at the following link: && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...MPR NEAR TERM...ARK/RWH SHORT TERM...MPR LONG TERM...MPR AVIATION...ARK
Area Forecast Discussion
National Weather Service Gray ME
1019 PM EDT Fri Jul 23 2021 .SYNOPSIS... Scattered showers and thunderstorms are across the region this afternoon and will wane as the sunsets. High pressure will build in with clear skies tomorrow. A front will approach the region overnight Saturday and cross the area on Sunday morning bringing widespread rain and thunder. && .NEAR TERM /TONIGHT/... 1015PM UPDATE... Only remaining cloud cover left out there is associated with two small areas of continued shower activity. This will continue to decrease in coverage through the remainder of this evening with little if any additional rainfall expected. With a mostly clear sky and calm winds, we should see good cooling tonight. Areas that had rain this evening will be most susceptible to fog formation and this has already occurred in some spots. 730PM UPDATE... It seems the most active of the convective activity has subsided. Outflow still pushing southwest across York County and through central New Hampshire. This is the most likely area for further convection this evening. Even this, though, is on the decrease. Areas that had rain this evening will be prone to fog overnight. Otherwise no significant changes in forecast thinking. ORIGINAL DISCUSSION... Scattered showers and thunderstorms persist across the region this afternoon as upper level trough keeps freezing levels low. Most of these storms are Pulse type, quick to intensify and quick to pass. With the low freezing levels have had reports of hail and expect some very isolated wind damage with the strongest cores collapsing. Convective initiation is very much tied to the diurnal heating and thus expect the reverse later this evening with coverage rapidly decreasing after sunset. HRRR has done a good job with the timing and general coverage of the convection and have leaned on it for the PoP for the next several hours. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... Overnight after storms decrease we`ll see clear skies. Satellite reveals a broad area of dry air to our west and expect temperatures to fall rapidly as a result. Lows will drop the low 50s with some northern valleys in the 40s. While it`s generally dry, midday dew points are in the 50s and expect fog to form in the CT river valley, and possibly up into the northern Androscoggin. For Saturday expect clear skies with high pressure. A robust seabreeze will likely push inland as far as Sebago lake and keep temperatures cooler along the coast. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Low pressure will be passing well north of the area as it travels through central Quebec Sunday morning, with a warm front associated with the system approaching the area at this time. Widespread shower ahead of the front will be ongoing Sunday morning. The rain will mostly end across western New Hampshire by the early afternoon as the region tries to break into the warm sector behind the warm front. The warm air is notoriously stubborn to actually make it in with these type of set ups, but if and where it does make will stand the best chance of seeing a few stronger thunderstorms Sunday afternoon as the cold front approaches. Areas farther east into Maine will likely hold onto the showers for more of the afternoon hours, thus minimizing the risk of storms across these areas. The front will most likely be clearing the coastline by Monday morning, with our trough dominated pattern continuing for the foreseeable future. Next week will continue to be characterized by temperatures generally near to below normal, with frontal passages roughly every other day and broad surface high pressure in between. High pressure looks to be in control for Monday, with seasonable highs and mainly sunny skies. A cold front will approach later Tuesday, likely brining a round of afternoon showers and thunderstorms. The front will likely clear the area on Wednesday, yielding clearing and improving conditions during the daytime on Wednesday as weak high pressure builds into the area for Wednesday night and Thursday. Another front will likely approach the area by late next week, but it`s too early to tell and there is significant model divergence on where and when the low will track through, so at this time I`m keeping an increased chance of POP`s for the end of the time period. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... Short Term... Fog tonight is most likely in valley locations affected by evening rainfall. That includes Whitefield but confidence is lower for Lebanon. Otherwise expect VFR conditions through Saturday. Long Term... Widespread showers will bring restrictions Sunday morning, lasting through most of the afternoon across eastern terminals, while western terminals see a period of VFR/MVFR conditions Sunday starting late morning before scattered thunderstorms develop in the late afternoon hours. VFR conditions return Monday, with another chance of showers and storms returning Tuesday afternoon. VFR conditions likely return later on Wednesday. && .MARINE... Short Term... Calm winds and seas will hold through the start of the weekend. Long Term... A front will cross the region on Sunday morning with rain, and thunderstorms. Winds will go NW behind the front. && .TIDES/COASTAL FLOODING... High astronomical tides will bring water levels just to minor flood stage across New Hampshire and southwest Maine. With calm seas and little wave action have opted for a Coastal Flood statement to highlight the elevated water levels. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM UPDATE...Kimble SHORT TERM...Curtis LONG TERM...Curtis
Area Forecast Discussion
National Weather Service Indianapolis IN
1145 PM EDT Fri Jul 23 2021 ...Updated Aviation Discussion... .Forecast Update... Issued at 933 PM EDT Fri Jul 23 2021 While isolated convection across the western portions of the forecast area has dissipated, persistent convection continues across the far northeast area. However this is showing signs of weakening as heating is lost. Upped PoPs where needed for this convection. With nothing to really sustain the convection after the heating is lost, expect it to continue to weaken and dissipate, and will allow PoPs to lower this evening with this trend. Given how slowly its weakening though, did extend PoPs in time a bit across portions of the northeast. Elsewhere just made some tweaks to hourly forecasts to match current trends. && .Short Term...(This evening through Saturday night) Issued at 244 PM EDT Fri Jul 23 2021 Much of the focus for weather later today and tonight will be on an exiting complex of thunderstorms that has moved now into northwestern Ohio. Latest GOES16 visible satellite imagery is showing a diffuse outflow boundary that is now stretching from south of Muncie up through Lafayette. This boundary has been a focal point for convection this afternoon with showers and a few rumbles of thunder ongoing. Don`t think that any widespread convection will occur, but do think that the latest HRRR runs showing isolated showers looks very reasonable with this area of enhanced lift across an area with over 2000 J/kg of surface CAPE. Surface visibilities haven`t been impacted by the hazy conditions today and don`t expect much through the rest of the day. During the overnight hours, convection will gradually dissipate with the loss of diurnal heating. Low clouds associated with peak heating should also be gone by 10 PM with mostly clear skies outside of the continued thin smoke layer. Do think that areas of ground fog are likely again tomorrow morning with the mostly clear skies and gradually increasing surface moisture levels. Any fog that forms will be brief. During the daytime hours, a few showers and storms are possible during peak heating, but think that any convection would be later in the day when a more robust convective system may drift as far south as the northern counties. SPC placed that area in a Marginal Risk which seems fairly reasonable at this time with the potential for an MCS to dive further south that models currently suggest in order to tap into the better instability. Exact timing is very uncertain with the potential anytime from late evening through the overnight hours. In addition to the precipitation chances, temperatures and surface dew points will gradually continue to rise with highs reaching the low 90s in spots tomorrow along with max heat indices greater than 100. && .Long Term...(Sunday through Friday) Issued at 244 PM EDT Fri Jul 23 2021 Much of the extended period will be highlighted by a stagnant... classic mid summer pattern as deep upper level ridging remains quasistationary focused over the central and southern Plains. While the Ohio Valley will reside on the periphery of the ridge through much of next appears very warm and humid conditions will be the norm with the potential for periodic isolated to scattered convection on most days driven by mesoscale details that have yet to be worked out at this stage. The best threat for storms at any point throughout the extended likely focuses on Sunday in association with a weak southward moving boundary. The boundary will interact with a hot and unstable airmass to initiate scattered storms that will gradually focus near and south of Interstate 70 by late day and into Sunday night. The boundary will settle into the lower Ohio and Tennessee Valleys before washing out on Monday...close enough to maintain a low threat of convection across southern counties through the day. By Tuesday and Wednesday...the threat appears even lower as weak high pressure attempts to expand into the region. While the northwest flow regime aloft cannot be ignored...the presence of the surface high presents enough uncertainty into the forecast to go dry both days at this time. The upper level ridge appears to retrograde slightly by late week as a sharpening trough amplifies over eastern Canada. This in turn will sharpen the northwest flow in between the two features and across the region...potentially opening the door for a greater influence from waves traversing through the flow to produce convection or even convective clusters. There are hints of a stronger surface low tracking to the northeast of the region as well with the possibility of a trailing frontal boundary back into the forecast area. Really impossible to pin anything definitive down for the 5-7 day period at this point...but it seems entirely plausible all things considered that higher pops will eventually be needed at some point in the Wednesday night through Friday period with a greater potential for storms over parts of the region. Highs in the upper 80 and low 90s will be common through the period with even higher readings in spots. A cooldown back to more near normal temps does appear on the horizon by next weekend. && .Aviation...(06Z TAF Issuance) Issued at 1145 PM EDT Fri Jul 23 2021 IMPACTS: - MVFR visibility likely at most sites at times overnight - Low VFR cumulus will develop again Saturday. - Some convection possible, mainly after 250300Z. DISCUSSION: Some MVFR ground fog is likely at KLAF and KHUF overnight, with KBMG also possible. Current thinking remains that KIND will avoid the fog. Additional cumulus will develop on Saturday. Brief MVFR ceilings cannot be ruled out during the morning. Convection is possible Saturday evening, spreading from north to south. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ Update...50 Short Term...White Long Term...Ryan Aviation...50
Area Forecast Discussion
National Weather Service Louisville KY
726 PM EDT Fri Jul 23 2021 ...Updated Aviation Discussion... .Short Term...(This evening through Saturday) Issued at 300 PM EDT Fri Jul 23 2021 North-northwesterly winds aloft along the eastern edge of the central CONUS ridge will continue to filter upper level smoke from western US wildfires across our region. At the sfc, broad sfc high pressure currently stretching across the Ohio Valley will slowly slide eastward into New England tomorrow, changing our winds from an ENE flow this afternoon and evening to more of a SE flow by tomorrow morning. However, by tomorrow afternoon, sfc winds will be southwesterly, which will help bring warmer and more humid air to our region. Dry wx remains in the forecast for tonight and into tomorrow. A weak stationary frontal boundary stretches across the Mid-Atlantic and cuts up through western Kentucky and into IL/IN. Most near-sfc smoke looks to cling to this boundary through this evening and into tomorrow. For our region, HRRR Smoke guidance suggests most smoke will be 6000ft and above, primarily due to a shallow inversion that is located around 850mb (5000ft). Could see an isolated shower/storm outside of our CWA to our west or south tomorrow afternoon, but with model soundings suggesting we`ll have convective temperatures in the mid-upper 90s, we won`t reach that to fire off any convection in our region. We could have a shower sneak into our southwestern CWA, but not entirely confident that will happen either so will leave dry wx grids for this forecast package. Winds look to go calm overnight under clear skies, so once again could have some early morning patchy fog possible south of the Pkwys, but not expecting this to cause too many issues. With southwesterly winds picking up tomorrow afternoon, temps will rise to the upper 80s and low 90s. .Long Term...(Saturday night through Friday) Issued at 318 PM EDT Fri Jul 23 2021 ...Saturday Night through Tuesday Night... Upper level pattern looks to start off with a broad ridge over western US with an upper trough axis moving out of New England. This will place the Ohio Valley within a northwest flow regime. Within this northwest flow pattern, a short wave trough axis is forecast to move through the southern Great Lakes and weak frontal boundary will drop southward through the region on Sunday. This should result in shower and thunderstorm activity returning to the region. Highest coverage looks to be on Sunday afternoon as the front drifts through the region. In terms of severe risk, the overall setup remains generally marginal. Best bulk wind shear will remain within the faster flow well to our north. We will have a build up of instability in the afternoon. PWATs will be up near 2 inches, so storms will be capable of torrential rainfall, gusty winds, and lightning. Convection should diminish in coverage Sunday night with the loss of heating. The front will slowly push through southern KY on Monday and we`re likely to see a gradient of PoP from south to north. The lesser chances will be across southern IN with the greatest chances down near the KY/TN border region. The front should slowly drop into Tennessee on Tuesday. However, will keep some low chance PoPs going for southern KY with the front in the area. If future model runs push the front further south, then subsequent forecasts may trend drier. As for temperatures, highs Sunday and Monday should top out in the upper 80s to near 90 with overnight lows in the upper 60s to around 70. Highs on Tuesday will again reach the upper 80s to near 90. ...Wednesday through Friday... By mid-week, the western US ridge is forecast to strengthen and build eastward. Center of the ridge looks to develop across the high Plains. The eastern nose of this ridge may push into the western part of the Ohio Valley for Wed/Thu for a time, but I suspect that a deepening trough axis over the northeast will shove it back to the west a bit. This would leave the Ohio Valley in a notorious northwest flow regime with the possibility of mesoscale convective systems dropping in from the northwest. The timing of those are very uncertain at this time frame, but there are strong signals in the data that we`ll be dealing with it by the end of the week. As for temperatures, much of the temperature forecast depends on the amount of upper level ridging building into the region. Confidence on temperatures is lower than average here. For now, am going to go a little more conservative than the ever increasing blended temps. I think upper 80s and lower 90s are a safe bet through this time frame with overnight readings in the upper 60s to the lower 70s. && .Aviation...(00Z TAF Issuance) Issued at 725 PM EDT Fri Jul 23 2021 VFR conditions are expected throughout most of this TAF cycle with the exception of potential MVFR VIS in fog at BWG and HNB. Latest surface analysis continues to show high pressure centered over the eastern Great Lakes with a weak boundary running N-S through W KY. Best chance for fog development will be along and on the warm side of this boundary with HNB likely experiencing longer and greater restrictions. Otherwise, Saturday will be another VFR day with light SW winds. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Short Term...CJP Long Term...MJ Aviation...CG
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1044 PM CDT Fri Jul 23 2021 .SHORT TERM... (Through Late Sunday Night) Issued at 311 PM CDT Fri Jul 23 2021 Currently aloft, the CWA is under weak northwest flow thanks to a broad ridge positioned over the western United States. At the surface, the area of high pressure responsible for our recent weather continues to drift slowly eastward away from our CWA. This feature has kept southerly flow sustained over the Middle Mississippi Valley today, which in turn has advected warm, moist air into the region. This has allowed heat index values to reach the mid to upper 90s for most locations, with a few more degrees of warming left in the day. Also, these warm and humid conditions have allowed for the atmosphere to become quite unstable over the CWA. Here, current SPC mesoanalysis shows 2,500-3,000 J/kg of SBCAPE that a subtle short wave has tapped into to produce isolated showers mainly across southeastern Missouri. As the shortwave moves through the Middle Mississippi Valley, I expect the chance for isolated showers and maybe a brief, weak thunderstorm to continue mainly over southeastern Missouri through early evening. The 12z HREF and recent HRRR runs have also shown convection further northward over the St. Louis metro area and into portions of western Illinois. Given the passing shortwave and how unstable the environment is, I feel this is a reasonable solution, and have expanded a slight chance of convection into these areas through early this evening. Tonight into tomorrow morning, another round of fog/haze is possible, as the smoke from the western wildfires has been slow the clear the CWA. Guidance currently gives me confidence that conditions tonight and tomorrow morning will be better than what was experienced last night with the smoke clearing to the east, but I can`t rule out some lingering pockets of haze/fog late tonight and tomorrow morning. During the day tomorrow, continued southerly low-level flow will keep temperatures warm and humidity high. Current indications are that temperatures will at least reach the low 90s area wide, with some locations reaching the mid 90s. This will be the case particularly in the St. Louis metro area, where heat index values are anticipated to reach 105 during the afternoon, and the current Heat Advisory looks to be on track. Later in the day, a cold front will approach the CWA from the north, bringing with it the chance of isolated to scattered convection. Model solutions differ on the timing of the front, with faster solutions pushing the front and associated convection into portions of northeastern Missouri and west-central Illinois during the evening. The timing of slower solutions would bring the front and convection into this portion of the CWA later overnight. Widespread severe storms are not anticipated, but with some guidance showing around 25 kts of 0-6 km bulk shear, I can`t rule out an isolated damaging wind gust and some hail with storms that form with the front. The differences in frontal timing continue on Sunday, leading to much uncertainty in how warm temperatures will get. If the front is slower, a repeat of Saturday`s temperatures will be possible across much of the region. If the front is faster, the frontal passage and associated cloud cover and convection will help subdue temperatures. I currently do not have confidence in either solution, and the current temperature forecast reflects a blend of both with a lean toward the warmer solution. If the slower front solution becomes reality, the heat advisory may need to be continued and possibly expanded on Sunday. Instability will be sufficient along the front for convection, but 0-6 km bulk shear looks to be 20 kts or less, so severe weather is not anticipated. Elmore .LONG TERM... (Monday through Next Friday) Issued at 311 PM CDT Fri Jul 23 2021 For Monday, the western upper-level ridge mainly stays in place, but surface conditions are not as steady. Deterministic guidance has varying solutions for the progression of the front and the surface high behind it, which has lead to a notable increase in the spread in ensemble guidance surface temperatures on Monday. Like the forecast for Sunday, and more progressive front would help curb temperatures by a couple of degrees and reduce humidity, where a slower solution would lead to the CWA remaining just as warm and humid as over the weekend, as well as linger the chance for scattered convection. These different solutions impact our weather through Tuesday and Wednesday. WPC cluster analysis shows all four clusters supporting the western ridge staying mostly in place. This gives me confidence in NAEFS and EPS guidance holding 850 mb temps around 21 degrees C, supporting surface temperatures across the CWA in the low to mid 90s. However, the placement of the aforementioned front and post- frontal high will determine how humid we`ll get, and therefore, what heat index values will be. Some guidance has the front stalling to the south of the CWA and easterly/northeasterly flow around the surface high keeping higher dewpoints shunted south. Other guidance has uninhibited southerly low-level flow over the CWA, advecting greater moisture into the area. If the first solution is realized, the CWA will still see highs in the low to mid 90s, but relatively lower humidity, whereas if the second solution is realized, highs will be in the mid 90s and humidity levels will be uncomfortable. Solutions begin to diverge considerably near the end of the extended period. Ensemble guidance differs on the phasing of the western ridge, the evolution of a trough over the eastern U.S. and its associated shortwaves, and the potential passage of another cold front through the CWA. This leads to much uncertainty as to how warm temperatures will remain at the end of the week or if a potential break from the heat is in store. Elmore && .AVIATION... (For the 06z TAFs through 06z Saturday Night) Issued at 1044 PM CDT Fri Jul 23 2021 VFR flight conditions expected through the forecast period. Otherwise, light south winds will veer to the southwest to west and increase to near 10 kts by 17z Saturday. Also, diurnal cu will develop across the region through the afternoon hours, before dissipating towards sunset. Precipitation chances will be on the increase Saturday night, mainly over northern portions of the forecast area as a cold front approaches. For now confidence is low that precipitation will develop over KUIN before 06z Sunday, so kept TAF dry for now. Byrd && .LSX WATCHES/WARNINGS/ADVISORIES... MO...Heat Advisory from noon to 8 PM CDT Saturday for Jefferson MO- Lincoln MO-Saint Charles MO-Saint Louis City MO-Saint Louis MO. IL...Heat Advisory from noon to 8 PM CDT Saturday for Calhoun IL- Jersey IL-Madison IL-Monroe IL-Saint Clair. && $$ WFO LSX
Area Forecast Discussion...UPDATED
National Weather Service Twin Cities/Chanhassen MN
700 PM CDT Fri Jul 23 2021 .SHORT TERM...(This evening through Saturday night) Issued at 249 PM CDT Fri Jul 23 2021 A warm front resides over far NW MN over northern WI while a cold front is draped over ND into MT, associated with a low pressure center over southern Manitoba. Squarely within the warm sector of this system is the WFO MPX coverage area. This has allowed areas under full sun to reach the low-mid 90s for highs (while areas under cloud cover are still in the 85-90 degree range with still several hours of warming available). With dewpoints into the upper 60s to lower 70s, this has allowed heat index values to climb to the 95-100 degree range for much of the area. However, this has also allowed MUCAPEs to climb to over 2000 j/kg for much of the area, particularly in western MN where values are 3000-4000. This available instability will be tempered a bit going into tonight as the cold front drifts closer to the area but the bigger concern will be an upper level shortwave expected to move across Manitoba/Ontario through northern MN/WI late this evening into the overnight hours. While the cold front will help enhance low-level convergence, increasing low-level jetting in conjunction with the arriving disturbance will enhance divergence aloft, allowing for loosely-organized clusters of storms to develop overnight in western MN and progress eastward through sunrise in eastern MN and western WI. Bulk shear will increase to around 30kt, so there is still some potential, isolated at best, of some strong to severe storms with damaging wind gusts or large hail overnight. The storms will diminish in coverage and shift east after daybreak as the cold front sweeps through the area, resulting in clearing skies behind his system. However, "clear" skies refers to the lack of cloud cover. HRRR Smoke model indicates a swath of upper level wildfire smoke returning to the area behind the cold front so while there may be little to no cloud cover, hazy skies will likely result and make for filtered sunshine during the day Saturday. As for temperatures, very little drop in temperature from today to tomorrow for highs is expected behind what is essentially a "cold" front. Highs will be more in the upper 80s to lower 90s, rather than hitting the mid 90s as today. That said, much less humid conditions are expected as the cold front will bring much drier air into the region as it passes through. Thus, this will make for slightly more tolerable conditions in terms of heat index. Therefore, once the Heat Advisory expires later today, no additional advisories will be needed for Saturday as heat index values will top out 90-95 degrees, highest of which will be east and south of the Twin Cities metro. .LONG TERM...(Sunday through Friday) Issued at 249 PM CDT Fri Jul 23 2021 Not much has changed during the long term period, the upper ridge slowly builds east out of the Great Plains into the Upper Mississippi valley. Locally, we`ll continue to experience above normal temperatures through the middle of next week. As per the previous AFD, the 12Z guidance continued the trend with a deepening trough across eastern Canada by the end of the week, with slightly cooler temperatures for next weekend. How far west the upper ridge retreats will be key for temperatures next weekend. A strong upper ridge develops over the center CONUS with heights reaching 597+ dm by mid week. We`ll remain on the edge of this ridge throughout the long term. This set up allows for potential shortwaves to move along top of the ridge, favoring the development of potential convective complexes. Forecast models like to develop convection during this pattern and as a result the NBM has 20-30 PoPs each night until Thursday. On Monday, moisture return kicks in and the humidity returns as dew points increase into the 60s. For us, the warmest temperatures arrive on Tuesday and Wednesday. Barring any convective debris or dense smoke layers, highs in the low to upper 90s and dew points in the upper 60s and lower 70s are expected. A frontal passage Wednesday night could trigger a round of thunderstorms across the region and provide some relief for temperatures on Thursday. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 700 PM CDT Fri Jul 23 2021 VFR this evening, then showers and thunderstorms build late this evening and track across central/southern MN and western WI overnight. MVFR or IFR conditions possible with the showers and storms. KMSP...TSRA chances increase after 06Z through about 11Z. IFR conditions possible within heavier cores. Skies clear quickly Saturday morning with much drier air moving in. /OUTLOOK FOR KMSP/ Sun...VFR. Wind W 5-10 kts. Mon...VFR. Slight chc SHRA/TSRA. Wind S 5-10 kts. Tue...VFR. Wind SW 5-10 kts. && .FIRE WEATHER... Issued at 249 PM CDT Fri Jul 23 2021 While scattered convection is expected overnight, the hit-and-miss nature of the thunderstorms plus short-duration rainfall is not expected to make any appreciable dent in the ongoing drought. In addition, the strong drop in dewpoints with highs still in the 90s will force RH values to 20-25 degrees for much of the coverage area, particularly west of I-35 and north of I-90. However, winds look to fall short of Red Flag criteria with speeds of 15-20mph and gusts 20-25mph. In addition, collaboration with MNCC officials indicated that the increase in humidity recently has allowed some smaller fuels to be reinvigorated, helping mitigate fire weather concerns despite the overarching drought. Thus, we have agreed to issue a Fire Danger (Special Weather) Statement to highlight the Critical RH and near- Critical RH values expected on Saturday. Should rainfall be less than advertised overnight, the situation could change and additional collaboration with surrounding offices and fire weather officials may be needed. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...Heat Advisory until 8 PM CDT this evening for Anoka-Blue Earth- Brown-Carver-Chippewa-Chisago-Dakota-Hennepin-Isanti-Kanabec- Kandiyohi-Lac Qui Parle-Le Sueur-McLeod-Meeker-Nicollet-Ramsey- Redwood-Renville-Rice-Scott-Sherburne-Sibley-Washington- Watonwan-Wright-Yellow Medicine. WI...Heat Advisory until 8 PM CDT this evening for Polk. && $$ SHORT TERM...JPC LONG TERM...BPH AVIATION...Borghoff FIRE WEATHER...JPC
...Updated Aviation Forecast Discussion...

.DISCUSSION... Issued at 223 PM CDT Fri Jul 23 2021 Synopsis: A heat advisory is in effect tomorrow for southeast Nebraska and southwest Iowa. Maximum afternoon temperatures are expected to remain above 90 degrees for the next 7 days. Temperatures at or above 100 degrees are expected Tuesday and Wednesday. Today and Tomorrow: Most locations in the forecast area have reached at least 90 degrees so far this afternoon. Maximum temperatures should peak in the 91 to 99 degree range with the warmest temperatures along the NE/SD border. Dew point temperatures have outperformed by 2 to 4 degrees so far today which will increase the effects of the heat. The increased moisture will likely result in many locations reaching a heat index of 100 degrees. Mid-level height falls are forecast across the northern Plains in response to a couple of shortwaves moving eastward. One of those shortwaves in combination with a surface frontal boundary may lead to some non-severe thunderstorms along the NE/SD border. The best chances for precipitation will be between 10 pm tonight and 6 am tomorrow morning. Rainfall amounts of less than a tenth of an inch are expected. Tomorrow, the HRRR smoke model indicates a higher presence of smoke across Nebraska and Iowa. The smoke may not be noticeable at the surface as it`ll be mostly aloft. The increased smoke in combination with height falls in the mid-levels may lead to slightly cooler temperatures than today. Temperatures will still be above 90 and dew point temperatures of least 70 degrees will result in a muggy afternoon. Sunday and Monday: Sunday and Monday will be the cooler days in the forecast period. Another weak mid-level shortwave is forecast to move through Nebraska and Iowa. A few non-severe thunderstorms will be possible Sunday evening into Monday morning. Whether precipitation is realized, temperatures these two days will depend on how much cloud cover develops from the passage of that weak shortwave. Tuesday through Thursday: Medium range guidance is still in good agreement in the intensification of a mid-level ridge across the central CONUS. NAEFS analysis of temperatures from 850 hPa up to 500 hPa show temperatures at those levels to be at least in the 99th percentile of climatology. All signs point to Tuesday and Wednesday being dangerously hot days. Maximum temperatures are expected to top 100 degrees in many locations. Minimum temperatures won`t drop below 75 degrees in southeast Nebraska and southwest Iowa. If the forecast doesn`t change, a heat headline will be needed for these two days. Some relief from the triple digit heat is forecast for Thursday. The mid-level ridge retrogrades to the West Coast leaving the central portion of the country in northwest flow. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 1028 PM CDT Fri Jul 23 2021 VFR conditions are expected through the TAF cycle. A weak frontal boundary is forecast to drift south overnight and will provide a subtle wind shift turning winds from southwest to north. There is a remote possibility that a few showers could develop along this boundary overnight to just past sunrise on Saturday. Did add a TEMPO group for KOFK but left KOMA and KLNK dry at this point. A few sprinkles are possible Saturday morning at these sites, but any associated clouds should remain at VFR category. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...Heat Advisory from noon to 8 PM CDT Saturday for NEZ051>053- 066>068-089>093. IA...Heat Advisory from noon to 8 PM CDT Saturday for IAZ079-080-090- 091. && $$ DISCUSSION...Fajman AVIATION...Kern
Area Forecast Discussion
National Weather Service Reno NV
1133 AM PDT Fri Jul 23 2021 .SYNOPSIS... Smoke and haze from multiple wildfires will continue to produce areas of reduced air quality over the next few days. Temperatures will gradually rise into the weekend with highs pushing above 100 degrees for most lower valleys by Saturday. Confidence is increasing for showers and thunderstorms returning to the region Sunday through much of next week. && .Discussion... * Smoke and haze with air quality impacts likely through the weekend for much of the region. * Hot temperatures return for lower valley areas with triple digit heat in the mix again. Some heat-health impacts possible. * Monsoon moisture will begin to build along the Eastern Sierra into southern Lyon/Mineral Counties Sunday with chances for isolated to scattered thunderstorms. Impacts include localized heavy rain, with higher risk of debris flows, especially for burned areas. An easterly wave will progress across the desert southwest through the weekend while high pressure strengthens across the Great Basin and northern California. This wave will help to eventually sweep up monsoon moisture into the eastern Sierra and western Nevada with increasing chances for shower and thunderstorms late this weekend into next week. For now through, the warming trend continues into the weekend with high temperatures around 5-8 degrees above typical late-July values, upper 80s-lower 90s for the Sierra and into the triple digits for western Nevada valley locations. If the hotter temperatures don`t get you to take a break indoors this weekend, then the smoke and haze certainly should. Weaker westerly winds the next few days will limit smoke/haze clearing across western Nevada and the Tahoe Basin today and Saturday. Multiple ongoing wildfires, Dixie and Fly in Plumas County and Tamarack in Alpine/Douglas Counties, will continue to produce smoke the next couple of days. The trend will be for increasingly poor visibility and air quality conditions, especially as winds shift west to northwesterly overnight. Latest HRRR smoke simulations funnel the smoke directly into Reno-Tahoe tonight into early Saturday. Keep those windows closed tonight! The next order of business headed into the weekend will be the potential for showers and thunderstorms as monsoon moisture begins to make a push for the region. Shower and thunderstorm potential will be rather isolated today and Saturday, with the best potential confined to far southern Mono and Mineral counties. Precipitable water parameters really ramp up by late Sunday into next week with values between 0.8 - 1.0 inches. These values are quite anomalous for the eastern Sierra and western Nevada. Confidence is high for the moisture to inundate the region, but the nature of showers or thunderstorms have yet to be determined. There doesn`t appear to be an obvious trigger or mechanism, for now, to facilitate deep convection, but that can change in these situations. We will continue to highlight the following risks with thunderstorms/showers for next week: (1) lightning may impact fire suppression, firefighter safety, or new fire starts (2) heavy rain: increased threat for flash flooding and increased risk of debris flows in steep terrain or burned areas. Areas south of Highway 50 have the best potential through Monday of receiving a wetting rain or thunderstorm, and the chances will expand northward for Tuesday and the remainder of next week. -Edan && .AVIATION... Greatest impacts through the weekend will be smoke/haze from ongoing wildfires. KMMH looks to largely avoid any big impacts, but most other terminal sites are likely to experience degradation in visibility. The worst visibility reductions with smoke ceilings will be at KCXP-KMEV (due to the Tamarack fire) and near Lake Almanor- KSVE-KLOL-KNFL (from the Dixie and Fly fires). All other terminals may only experience slantwise visibility reductions with periods of lower surface visibility. Westerly flow weakens today which will limit smoke clearing out of the Tahoe Basin and Sierra Front. There will be some improved mixing late in the afternoon for KTVL/KTRK/KRNO, but conditions will likely stay relatively poor for KCXP and KMEV. Smoke from the Dixie and Fly fires in Plumas County will flood into western Nevada late tonight into early Saturday as flow gradually shift west and northwest. Sunday may be very similar with little change in the wind direction early Sunday. The flow Saturday could bring smoke to all areas north of KMMH, with similar conditions for Sunday. For this afternoon and evening, there may be a few stray thunderstorms around KMMH and the White Mountains eastward as well as Saturday afternoon. There are slightly better chances (15-20%) Sunday from KBAN-KHTH south. A moisture push early next week will bring increasing chances for showers and thunderstorms across the eastern Sierra and western Nevada. -Edan && .FIRE WEATHER... No significant changes to the ongoing fire weather forecast. The gradual heating trend continues through the weekend with late afternoon/evening winds gusting into the 20-25 mph range. For northeast CA, humidity recovery will continue to be poor to moderate at best until the bulk of the moisture surge arrives early next week. For the eastern Sierra up to Tahoe, recoveries will improve faster as moisture builds on the edge of an approaching monsoonal push. A few buildups are anticipated in these areas today and Saturday with an isolated thunderstorm for southern Mono into southern Mineral Counties. Thunderstorm and shower potential will be on the increase Sunday and through next week. Ensemble simulations are showing a decent push of monsoonal moisture into the eastern Sierra, Tahoe Basin, northeast CA and western Nevada with precipitable water values nearing 1.00" for some locations. There is a high probability for localized wetting rains with an increased potential for flash flooding. Steep terrain and burned areas will be the locations to keep an eye out for flash flooding and higher risk for debris flows. Lightning will also pose a danger to ongoing fire operations. Hohmann/Edan && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$ For more information from the National Weather Service visit...
Area Forecast Discussion
National Weather Service Sacramento CA
103 PM PDT Fri Jul 23 2021 .SYNOPSIS... Dry weather with temperatures warming into the weekend. Chances for mountain thunderstorms in the northern Sierra return late weekend into early next week. && .DISCUSSION... A brief period of northerly winds has pushed fire from the Dixie and Fly fires south into central valley. This was picked up pretty well by HRRR smoke. Expect a little of a delta breeze later this evening to push it back north and east. Have added it to forecast though for this afternoon and evening. Beyond that forecast still on track which is that upper level ridge will retrograde back over California slowly. Monsoonal moisture will begin effecting the far southern portion of our forecast area in the Sierra with isolated thunderstorms. PW`s looking pretty high so they shouldn`t be dry but will for sure have gusty winds and brief downpours. && .EXTENDED DISCUSSION (Tuesday THROUGH Friday)... Large area of high pressure will dominate the forecast during the extended period. Monsoonal moisture and instability will likely lead to at least isolated thunderstorms. Timing and coverage is always tricky with these patterns but for now pretty high confience activity will remain in mountains and upper foothills. Have expanded coverage of pops a bit Tuesday to include higher terrain of Shasta County. Otherwise for the most part chances are for Sierra south of I-80. Rasch && .AVIATION... VFR conditions are generally forecast to prevail over the next 24 hours. Exception would in the mountains and foothills where areas of IFR visibilities and mountain obscurations are possible as a result of wildfire smoke. Winds generally less than 12 kts except gusts up to 25-30 knots in the vicinity of the Delta. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
530 PM MDT Fri Jul 23 2021 .DISCUSSION...(This Evening Through Friday) Issued at 1230 PM MDT Fri Jul 23 2021 The latest water vapor images and RAP model 500-mb height analysis showed an upper high anchored over the Southwest U.S. with quasi-zonal flow across the CWA. One short-wave trough was evident over central/eastern WY and it was associated with considerable cloud cover. This will dampen heating and thus result in less MLCAPE and more MLCIN than previously expected. Better insolation was over central SD, which should be more favorable for later convective development. Otherwise, another short-wave trough was moving across central MT in association with a 70-90kt jet streak. Q-vector convergence supports stronger lift with this system; lapse rates, CAPE, and 0-6km bulk shear will be better with this wave, and thus convective development appears better. Based on this and the CAMs it seems probable that weaker storms will form over the BLKHLS, with strong-to-severe storms (and supercells) over parts of northwestern into central SD, and then some severe storms with a wind threat over south-central SD where inverted-V soundings, a weak boundary, and weaker 0-6km shear exist. PWATs of 150-200 percent of average favor locally heavy rain, but the lack of a focusing boundary and mean winds of 15-20kt should preclude organized heavy rainfall. Otherwise, these storms/small MCSs should be mostly east of the CWA by 04z. Convection will be relatively diminished Saturday and Sunday as the monsoonal moisture plume is shunted south of the CWA. However, some warm advection and steeper lapse rates over the southwestern CWA will favor elevated storms late Saturday, and possibly Sunday too as monsoonal moisture creeps back into the CWA. Monday through Wednesday look to be exceptionally hot as the Southwest U.S. upper high builds northward. Record highs and record high lows appear likely on Tuesday based on the latest ensemble and NBM guidance. The main limiting factor is the potential for smoke to reduce insolation. The upper ridge then appears to retrograde Thursday and Friday as upper low pressure deepens over the Hudson Bay area. Monsoonal moisture also should spread back across the CWA. This will bring a modest reprieve from the heat along with slightly better chances of showers and thunderstorms. && .AVIATION...For the 00Z TAFS Through 00Z Saturday Evening Issued At 523 PM MDT Fri Jul 23 2021 Thick band of mid level clouds streaming over southwestern into central SD will shift to the east overnight, leaving mostly clear skies Saturday. Thunderstorms moving across northwestern SD. Heavier smoke is moving into northeastern WY and will spread across the area, reducing visibility occasionally. && .FIRE WEATHER... Issued At 1230 PM MDT Fri Jul 23 2021 Minimum relative humidities will fall to 10-15 percent on Monday and Tuesday across northeastern WY and northwestern SD as high temperatures soar into the upper 90s and 100s across most of the area. However, at this time it appears that wind speeds will remain below red flag warning criteria. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ DISCUSSION...Bunkers AVIATION...55 FIRE WEATHER...Bunkers
Area Forecast Discussion
National Weather Service Las Vegas NV
230 PM PDT Fri Jul 23 2021 .SYNOPSIS...Moist and unstable air will remain in place through the weekend, providing fuel for thunderstorms. A large circulation moving in from Arizona will likely bring additional moisture and more extensive thunderstorm development across the entire region especially late Sunday into Monday. && .UPDATE...Another monsoon day for the desert Southwest, though coverage was less than what we have seen the past few days. Main areas that saw afternoon convection were through Lincoln County as well as eastern Mohave County. Some training storms with high rainfall rates did cause some flash flood concerns in southeast Mohave County, but further north the concern was more about the potential for strong winds. An outflow developed from decaying storms in southwest Utah later this afternoon as has been tracking southeast through eastern Lincoln County, northeast Clark County and northern Mohave. Along the outflow, gusts 40 to 50MPH have been reported. In addition, the outflow has allowed for additional thunderstorms develop as it unzips the atmosphere and allows for the extra kick to cause thunderstorm initiation. Moderate confidence that this outflow will continue to track southwest through much of Clark County and the Lake Mead area. With current mesoanalysis showing MUCAPE values still over 1000 J/Kg, additional isolated to scattered thunderstorm development is possible over the next few hours as the outflow moves through. The storms are moving quickly and diminish fairly soon after initiation, so the threat for flash flooding is not high. However, DCAPE values remain in the 1500-2000 J/Kg range over Clark County and the Lake Mead area, and dry air was noted both in the low levels as well as above the main cloud layer. A few downdrafts and sudden gusty winds 40-50 MPH are possible with these storms. The other area of concern tonight is in eastern Mohave County. A complex has been pushing west through Arizona and is almost at the county border. This area of precipitation should continue to push west tonight, and though the complex should diminish over the next few hours, high PWAT values over this region could cause some heavy rain and isolated flash flooding. A couple of the Warn on Forecast ensemble members do show "paintballs" of 1 in/hr rain rates around the Valentine and Fort Rock area, and there is a non-zero probabilities of over an inch QPF through central Mohave County until 06Z on the HREF 3hr PMMs. Precipitation may linger through southern Mohave overnight before ending Saturday morning, but the heaviest and most widespread precipitation should be through 06Z. && .SHORT TERM...tonight through Sunday. A favorable setup continues to come together for thunderstorms to converge around northeast Clark County early this evening and push down the I-15 corridor which will likely impact Lake Mead and possibly the Las Vegas Valley. The HRRR and various HREF members continue to show this trend which should materialize between 7 PM and 11 PM PDT/MST. The main threat would be winds 40-50 mph, and possibly higher. Heavy rain and localized flash flooding will also be possible, but the storms should be progressing toward the southwest fairly quickly. Storms should continue developing after midnight as the outflow boundary pushing southward through Mohave County. Saturday and Sunday will see the approach of the large slow moving inverted trough moving westward across Arizona which will produce thunderstorms propagating from northeast to southwest. The latest HREF members indicate an organized cluster of storms Saturday evening bringing the threat of heavy rain and flash flooding to central and southern Mohave county and the nearby Colorado River Valley from Laughlin-Bullhead City to Lake Havasu. Favorable conditions will continue for large organized clusters of thunderstorms into Sunday. A Flash Flood Watch is in effect Saturday afternoon through Sunday evening for Mohave County and the Colorado River Valley from Lake Mead to Lake Havasu. As the wave slowly progresses, the potential for numerous thunderstorms with heavy rainfall may expand into southern Nevada and eastern San Bernardino County by Sunday night. && .LONG TERM...Monday through Friday. The latest ECMWF and GEFS ensemble means indicate the axis of the easterly wave will be centered about over southeast California and northwest Arizona by 12Z Monday then will continue lifting toward the northwest during the day. This will be favorable for generating showers and thunderstorms on the leading edge of the ridge which will increasingly favor western San Bernardino and Inyo counties along with south central Nevada Monday afternoon and evening. Convection should diminishing on the back side of the wave and the forecast area will be under a general southeast flow Tuesday through Friday with moisture decreasing somewhat, but there will still be sufficient for afternoon showers and thunderstorms the rest of the week. && .AVIATION...For McCarran...Thunderstorm formation on area mountains to the south and west of the Las Vegas Valley are possible today. Prevailing wind speed and direction should veer from 160 to 220 through the afternoon with speeds generally around 8 kts. However, storm formation could result in wind shifts as well as gusty winds from their direction this afternoon. Between 03 and 08Z this evening, there is a chance of a gusty northeast outflow reaching the terminal. Confidence regarding timing and strength is low at this time, and will continue to update the TAF accordingly. SCT-BKN cloud bases down to 10 kft possible. For the rest of southern Nevada, northwest Arizona and southeast California...Focus area for storms today are in Lincoln/Mohave counties and Mohave County tonight. Storm formation is possible on Clark County mountains that could result in wind shifts and gusts from either the southeast or west this afternoon. Otherwise, storm formation is not anticipated directly over any terminals, with diurnal wind patterns otherwise expected. SCT-BKN cloud bases down to 10 kft possible. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ UPDATE...Nickerson SHORT TERM/LONG TERM...Adair AVIATION...Varian For more forecast information...see us on our webpage: or follow us on Facebook and Twitter