Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/01/21

National Weather Service Albany NY
1034 PM EDT Tue Aug 31 2021 .SYNOPSIS... A comfortable night expected across the region under variable cloudiness as weak high pressure comes across upstate New York. However, the remnants of Ida across Tennessee and Kentucky are forecast to approach Wednesday into Wednesday night with a period of rainfall, especially south of the Adirondacks. The wet weather is expected to end during Thursday as a brisk northerly wind evolves. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... As of 1030 pm, with this forecast update, PoPs were tweaked in the 09-15Z timeframe to allow for a faster increase over the southern tier of counties based on the latest couple of runs of the HRRR/NAM3. It does appear that Fgen will bring in precip by 12Z if not a bit earlier. Also increased cloud cover once again based on latest obs showing thickening cirrus. Temps have fallen off quickly over the North Country where clouds are thinner, so we adjusted the temps in the near term as well. These should stabilize as the clouds thicken. Previous discussion... As of 4 pm, diurnally driven CU/SC deck seen in the GOES imagery was under a thin and opaque CI/CS. As the loss of daytime heating occurs, so will the decrease in CU/SC but the CI/CS will likely linger across southern areas. There will be an increasing trend from south to north overnight as combination of Ida and ongoing convection along the frontal zone near I80 begins to advect northward. Overnight lows will be a challenge as portions of the Dacks may be a bit cool with mid-upr 40s to lower 60s for the mid-Hudson Valley and southern Litchfield County. Looking at the latest HRRR, the chance for rainfall increases a bit toward the southern zones near sunrise as mid-upr flow becomes increasing confluent across these areas. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/... .A Flash Flood Watch expanded to include northern Berkshire County and remains in effect for Greene, Columbia, Ulster, Dutchess, Litchfield and southern Berkshire counties from Wednesday afternoon through Thursday afternoon... Extensive collaboration today between neighboring offices and national centers as we closely watch the approach and potential impacts from Ida. 12Z NCEP Model Suite and international guidance have trended northward with expected FGEN, upper jet dynamics and expected QPF. Rain is expected to increase from south to north as the combination of increase interaction with frontal boundary and isentropic lift gets underway. The rain shield will likely have a sharp cut-off where portions of the Dacks may remain mainly dry from this event. Cross sections depict a rather impressive FGEN band(s) may develop and impact the southern 1/2 or 1/3rd of the region late Wednesday into Wednesday night. Local research from colder season events, suggest rainfall rates could be rather significant and a layer of negative EPV seen in the cross sections south of Albany could aid in precipitation efficiency. Due to the northward shift, and per coordination, we expanded the flash flood watch to include northern Berkshire County. The other concern could also be the wind gust potential, especially across the terrain. Latest 18Z run of the HRRR and NAM3km surface wind gust forecast suggests values of 30-40kts across portions of Ulster, Dutchess and Litchfield Counties. But a closer look at forecast point soundings, boundary layer may remain just stable enough to limit mixing potential. Regardless, we will make a mention in the HWO given the hazard of wet soil and any higher wind gust(s) could topple trees. The rain should quickly exit to the east of the CWA shortly after 12Z Thursday. Thereafter, a brisk northerly flow of drier and cooler air mass advects into the region. H850 temperatures drop back into the single digits as mixing layer heights climb to aid with close to 20kt gusts...especially into the Hudson River Valley locations. High temperatures Wednesday will only reach the mid-60s to mid- 70s with lows Wednesday night in the upper 40s to near 60. Highs Thursday will range from the lower 60s in some higher terrain areas to the lower 70s in some valleys. Lows Thursday night in the upper 40s to mid-50s. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... As the remnant low from what was once Ida lifts across Atlantic Canada, a large closed off upper level trough will be over northern New England and will be slowly moving towards the Gulf of St. Lawrence for Thursday night through Saturday. Although this closed low will be far enough to the northeast to avoid any rainfall for our area, its cyclonic flow will influence the area with a cool, northerly flow. The lower heights will keep temps aloft rather low as well, which will keep daytime temps in the mid 60s to mid 70s across the area. Overnight lows will generally be in the 50s, although some upper 40s are possible for the highest terrain on Thursday and Friday nights. While it should be dry, there will be some diurnal cumulus that forms thanks to chilly temps aloft. The closed low will move away for Saturday night into Sunday, allowing the flow aloft to flatten out and temps aloft to rise. However, another upper level disturbance north of the Great Lakes will begin approaching the area and this may allow for some showers and possibly a thunderstorm for late Saturday night into Sunday. Best chance may wind up being north/west of the Capital Region, especially during the diurnal favored afternoon hours on Sunday. Temps should be slightly milder for Sunday, with highs mainly in the lower to middle 70s across the area. Dewpoints may be creeping back up into the 60s by late Sunday as well. As the upper level disturbance slides across southern Canada, will keep slight to low CHC POPs across the area for Monday into Tuesday, especially during the daytime hours. Any precip looks fairly scattered in coverage and mainly brief in duration. Temps will remain seasonable, with valley temps still reaching into the mid 70s for daytime highs. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... High clouds will thicken and gradually lower tonight as upper level moisture associated with the remnants of TC Ida approaches. Clouds should be relatively less thick at KGFL which will allow a window for some radiational fog/mist to develop, especially after 06Z (but possibly sooner). VFR conditions should prevail otherwise, but a few high-based showers will be possible at KPOU/KPSF late tonight toward sunrise Wednesday. Flight conditions may deteriorate fairly quickly at KPOU as a rain associated with tropical moisture and a frontal circulation spreads in. Brought in MVFR cigs/vsby at 14Z and kept levels there through the day, but would not be surprised if some brief IFR conditions occurred depending on where the heaviest rain bands set up. Conditions should fall to MVFR at KPSF later in the afternoon as the front inches northward, and currently expect KALB to remain VFR through the TAF period with the lower cigs/vsbys staying just south. Rain is expected to remain south of KGFL through the TAF period. Heaviest rainfall and worst flight conditions are still expected just after the 00Z TAF cycle. Winds will be light and variable, becoming north to northeasterly around 5 kt Wednesday (increasing to around 10 kt late in the period at KPOU). Outlook... Wednesday Night: High Operational Impact. Chance of RA. Thursday: Moderate Operational Impact. Chance of RA. Thursday Night: No Operational Impact. NO SIG WX. Friday: No Operational Impact. NO SIG WX. Friday Night: No Operational Impact. NO SIG WX. Saturday: No Operational Impact. NO SIG WX. Saturday Night: No Operational Impact. NO SIG WX. Sunday: Moderate Operational Impact. Chance of SHRA. && .FIRE WEATHER... Mainly dry, seasonable and less humid conditions are expected across the region through tonight under a partly to mostly cloudy sky. Rain associated with Ida will brush portions of the region Wednesday into Thursday with a period of moderate to heavy rain likely for areas south and east of Albany. Drier and fall-like weather then moves in to end the week. RH values rebound to 90 to 100 percent tonight. RH values only lower to 60 to 80 percent on Wednesday. Wind will be out of the west 7-14 mph with some higher gusts possible through this evening, then become variable at 7 mph or less tonight through Wednesday. && .HYDROLOGY... A comfortable night expected across the region under variable cloudiness as weak high pressure comes across upstate New York. However, the remnants of Ida across Tennessee and Kentucky are forecast to approach Wednesday into Wednesday night with a period of rainfall, especially south of the Adirondacks. The wet weather is expected to end during Thursday as a brisk northerly wind evolves. A Flash Flood Watch was extended to include northern Berkshire County and remains in effect for Ulster, Dutchess and Litchfield counties and has been expanded to include Greene, Columbia and southern Berkshire counties. Storm total rainfall of 2 to 4 inches in these areas could result in flash flooding. Some river rises are expected with some possible rising to flood stage, as latest NERFC highlights significant river flooding possible for Ulster, Dutchess and Litchfield Counties. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...Flash Flood Watch from Wednesday afternoon through Thursday afternoon for CTZ001-013. NY...Flash Flood Watch from Wednesday afternoon through Thursday afternoon for NYZ058>061-063>066. MA...Flash Flood Watch from Wednesday afternoon through Thursday afternoon for MAZ001-025. VT...None. && $$ SYNOPSIS...BGM NEAR TERM...BGM/Thompson SHORT TERM...BGM LONG TERM...Frugis AVIATION...Thompson FIRE WEATHER...BGM/Rathbun HYDROLOGY...BGM/Rathbun
Area Forecast Discussion
National Weather Service La Crosse WI
1040 PM CDT Tue Aug 31 2021 .SHORT TERM...(This evening through Wednesday) Issued at 236 PM CDT Tue Aug 31 2021 Early this afternoon a shortwave trough was passing across eastern Iowa with upstream ridging developing across the northern plains. Most of the associated showers have remained just south of the local area, although some thicker mid/high clouds were impacting northeast Iowa into southwest Wisconsin with A few showers/sprinkles possible through the afternoon. As the wave continues to pass to the southeast, the clouds will decrease late this afternoon with mostly clear skies heading into tonight. Tranquil weather will continue into Wednesday as mid-level ridging gradually builds eastward, while Canadian high pressure centered to the northeast will advect seasonably dry air across the region. Some patchy fog could develop once again tonight in favored valley/low-lying areas. Little change in thermal fields is expected through Wednesday with lows tonight mainly in the upper 40s and 50s and seasonable highs Wednesday in the 70s to low 80s. .LONG TERM...(Wednesday night through Tuesday) Issued at 236 PM CDT Tue Aug 31 2021 The next chance for some rain continues to be centered on Thursday night into Friday. The upper level ridge axis will be retreating off to the east allowing a short wave trough to come out of the Desert Southwest and move across the region. As it does, it looks to start getting ingested into a large upper level low moving across southern Canada, that some of the models are suggesting could cause the wave to start breaking apart and loosing energy. There should still be enough left of the wave to produce at least some weak pv advection in the 500-300 mb layer late Thursday night into Friday morning, with the better forcing going off to the north. This same weakening trend is evident in the low levels as a weak area of low pressure along the incoming cold front looks to dissipate as it approaches the area early Friday morning. However, before it does, there is a decent signal that the activity could produce some locally heavy rains. The instability looks to very low, so most of the activity should just be showers, but there is a good low level moisture transport feed into the region ahead of the short wave trough. Precipitable water amounts should increase into the 1.5 to 1.75 inch range, with the 31.00Z NAEFS indicates is close to 2 standard deviations above normal. With warm cloud depths of 4 to 4.5 km, would expect the showers to be efficient rainfall producers. Fortunately, this system looks to be progressive and with the line coming in oriented north/south the potential for training looks to be rather low, so would not expect this to be much of a flash flooding threat. Once this system clears out of the region, the weather through the upcoming weekend into early next week looks to be rather tranquil. A couple of small chances for some rain with passing systems both Sunday and Monday afternoon. Friday looks to be coolest day with highs mainly in the 60s with seasonable highs mainly in the 70s otherwise. And as a sure sign that fall in approaching, overnight lows look to consistently drop into the 40s and 50s. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1040 PM CDT Tue Aug 31 2021 Cigs: generally skc/sct conditions through the period. Some potential for a few hour window of bkn002 at KLSE, centered around 12z, in response to fog developing in the river valley. This outcome is highly dependent on the low level wind field...with some meso models suggesting they will be too high, while the RAP is trending a bit lighter (favoring low cigs). More on that below... WX/vsby: another clear, light sfc wind night will promote fog in the river valleys. Winds just off the sfc though increase to 10+ kts by 300 ft or so in the NAM/HRRR soundings, holding there through the night. This generally prevents any fog spreading off the river and onto the airport. That said, trends over the past few hours in the RAP is a decrease in these winds overnight...suggesting a greater likelihood of some vsby impacts and associated low cigs. For now, going to lean the forecast toward the low cigs rather than lower vsbys - but as always in these scenarios - which watch trends closely and update as needed. Winds: light easterly through the period, getting a bit more southeast on Thu. && .HYDROLOGY... Issued at 236 PM CDT Tue Aug 31 2021 The flood waters continue to slowly recede with water levels having gone down enough to drop the warnings along the Turkey River. Warnings remain in place along portions of the Black and Yellow Rivers. See the latest flood statements for details. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...JM LONG TERM...04 AVIATION...Rieck HYDROLOGY...04
Area Forecast Discussion
National Weather Service Boise ID
830 PM MDT Tue Aug 31 2021 .DISCUSSION...Upper trough passing by to our north has cleared smoke out of the northwest half of our CWA. The smoke, from several large wildfires fires in eastern California, still covers the southeast corner of Oregon, and Idaho south of Boise-Salmon. According to the HRRR smoke model, northwest winds will clear the near-surface smoke out of all of southwest Idaho overnight, but will bring lesser amounts in from the northwest Wednesday. Meanwhile, smoke aloft is forecast continue into Wednesday except in northern-most areas. Northwesterly flow at the surface and aloft should keep the denser California smoke away through Friday, but southwesterly flow after that may bring it back into at least our southern areas. Other than the smoke, we see another clear, cool night as the upper trough passes by, then similar temps to today on Wednesday and Thursday before warming Friday and Saturday. Current forecast has this so no updates. As for our next rain we see no realistic chance through at least next Wednesday when GFS brings a weak Pacific trough inland. But even that looks doubtful as ECMWF maintains a dry upper ridge through the end of next week. && .AVIATION...Mainly VFR. Areas of MVFR in the Magic Valley due to wildfire smoke. Smoke reducing visibility aloft and in the mountains south of a KREO-KBOI-KSNT line. Surface winds: variable 10 kt or less overnight. Winds aloft at 10kft MSL: W to SW 10-20 kt. && .PREV DISCUSSION... SHORT TERM...Tonight through Thursday night...An upper trough along the WA/Canada border will track eastward on Wednesday while a weaker trailing low will swing through the Intermountain NW on Thursday. Neither of these systems will bring a chance for precipitation but they will keep temperatures slightly below normal through Thursday. Mid-upper level flow will act to confine the smoke across southern portions generally south of a Burns- Ontario-Stanley line. LONG TERM...Friday through Tuesday...Zonal to southwest flow aloft will develop Friday through Sunday associated with upper level ridging over the Desert Southwest and troughing across Canada. Temperatures on Friday will be 3-5 degrees below normal behind a departing upper trough, then rebound to several degrees above normal Saturday and Sunday. Smoke from wildfires in California and Oregon may be transported into our area under this flow pattern. The upper ridge will amplify Monday and Tuesday across the Great Basin, with the flow aloft becoming northwest and bringing a couple degrees of cooling. Dry conditions will continue through the period with breezy afternoon winds. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && $$ DISCUSSION...LC AVIATION.....SH PREV SHORT TERM...DG PREV LONG TERM....ST
Area Forecast Discussion
National Weather Service Denver/Boulder CO
732 PM MDT Tue Aug 31 2021 .UPDATE... Issued at 707 PM MDT Tue Aug 31 2021 Updates were added to include surface smoke increasing in northern counties such as Weld and Larimer through Wednesday morning. Sustained winds and wind gusts were increased across the eastern plains to include the potential of a boundary set up stretching across the county warning area (CWA). Maximum temperatures in the mountains were decrease to reflect the incoming moisture through the late afternoon to evening. && .SHORT TERM...(This evening through Wednesday) Issued at 350 PM MDT Tue Aug 31 2021 Satellite pictures are showing some developing convective clouds over the mountains, foothills and Palmer Ridge. Radar was showing a couple of weak cells over far eastern Lincoln County. Models have the upper ridge to push southeastward tonight and Wednesday with increase southwesterly flow aloft by Wednesday afternoon. There is weak upward vertical velocity progged for the CWA in the synoptic scale tonight and Wednesday. Models bring in some of the mid and upper level moisture into the CWA tonight. The lower level moisture doesn`t get into the western CWA until Wednesday afternoon. There is no low level moisture over the plains tonight or Wednesday. Will bring pops into the western CWA by Wednesday afternoon. QPF fields are not excited about precipitation amounts. There is more west of the forecast area. Concerning smoke, the HRRR model shows a decrease with the smoke over the CWA on Wednesday. Will leave it out. For temperatures, Wednesday`s highs look 2-5 C cooler than today`s. .LONG TERM...(Wednesday night through Tuesday) Issued at 229 PM MDT Tue Aug 31 2021 We`ll have the shortwave and deepest moisture coming over our area Wednesday night. The timing isn`t great for strong convection, and the moisture is accompanied by warming in the mid levels. Forecast soundings for 00Z Thursday actually have an inversion around 500 mb. So while we`ll have 1-1.25 inches of precipitable water at the peak, other factors such as the prospect for sustained strong updrafts as well as mean winds around 15 knots do not favor heavy rainfall. The greatest threat would likely be just a blob of moderate to heavy rain that takes some time to move across a spot, or a couple of shower bands that are close together in time, that could produce a half inch to inch of rain in an hour or two. This would more likely be decaying convection that formed in western Colorado earlier in the day. This would still be a problem for our new burn areas, but the flooding risk looks low otherwise. We`ll still have fairly high PoPs for when this forcing moves over. Another complication is that as the lift moves over the I-25 corridor, there will also be post-frontal winds that will likely have a downslope component. Thursday is looking a little drier, as the deep moisture will be shifting east of our area. The EC and NAM are more aggressive with this that the other models. If they`re right, there will be quite a bit less convection on Thursday as CAPEs will only be a few hundred J/kg over the mountains and the plains will be weakly capped. For Friday, it appears there`s another weak shortwave trough. Mid level moisture is limited, but we will likely have more moisture again over the plains from low level southerly flow. The steering winds are still probably at least 15 knots, so the flash flood threat will not be that great. There could also be some threat of severe storms on the plains this day with CAPEs up to 1000 J/kg and an adequate hodograph. It will be drier and warmer for the weekend, though some lingering moisture and convergence could produce diurnal Front Range storms on Saturday. It could be quite hot and dry again for Sunday and Monday. There`s decent agreement on a shortwave dropping over the ridge into the northern plains about Tuesday that would bring some cooling. Our model blend looks alright with all of this. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 525 PM MDT Tue Aug 31 2021 VFR conditions will persist through the TAF period at all terminals. Tonight, a shortwave will bring wind gusts up to 21kts to KDEN and KAPA through 07Z. Wildfire smoke will continue to impact slant visibility aloft; although, it will begin to decrease through Wednesday afternoon due to incoming showers. Challenges within the forecast begin Wednesday afternoon as incoming moisture arrives in the mountains but struggles to reach the TAF sites until 0Z. Direction of sustained winds are also a forecast challenge due to a boundary short-term models have placed within the area of the TAF sites. Depending on the placement of the boundary through Wednesday afternoon, sustained winds could become northerly instead of southerly at KAPA and vice versa at KDEN through early Thursday morning. && .HYDROLOGY... Issued at 350 PM MDT Tue Aug 31 2021 There will no threat of flash flooding tonight and Wednesday morning. With increasing moisture over the mountains Wednesday afternoon, the chance of showers and thunderstorms will increase there. There will be a slight threat of flash flooding over the burn areas during the late afternoon. There will be an increased risk of heavy rainfall over the mountains Wednesday evening as an upper level trough with better moisture moves across the area. Rainfall rates of up to an inch in an hour will be possible even though storms should be moving. This will create a moderate flash flood risk for the new burn areas, while the threat elsewhere will be low. For Thursday and Friday, scattered storms are expected over the mountains. They should have decent storm motions, but could produce brief heavy rainfall and a low flash flood risk for the burn areas. Drier weather is expected this weekend with little or no thunderstorm activity. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...AD SHORT TERM...RJK LONG TERM....Gimmestad AVIATION...AD HYDROLOGY....RJK/Gimmestad
Area Forecast Discussion
National Weather Service Grand Forks ND
630 PM CDT Tue Aug 31 2021 .UPDATE... Issued at 630 PM CDT Tue Aug 31 2021 There are just a few cumulus clouds left across the FA early this evening. The setting sun is also showing a little bit of high level smoke, which is much thicker over eastern Montana and western South Dakota. The HRRR model shows this thicker smoke pushing into the area tonight into Wednesday. Winds were also pretty gusty over the western Dakotas, and that will also spread into the FA Wednesday. && .SHORT TERM...(This evening through Wednesday Night) Issued at 305 PM CDT Tue Aug 31 2021 Minimal impacts in the short term with attention being primarily in the long term wrt to storms and heavy rainfall potential. With western high plains troughing developing overnight will see southeasterly winds persist helping keep temps a bit warmer than the past couple morning`s with lows in the mid and upper 50s. As the pressure gradient tightens with the approach of the western SFC trough winds will increase Wednesday with southeasterly gusts at 25 to 35mph. Highs will be in around 80 with increasing upper level clouds moving into the area in the late afternoon. Models continue to key in on a lead shortwave ejecting NE in the mean flow from SD into SE ND and as it does will see thunderstorm chances increase late Wednesday fueled by an increasing low level jet. If a complex does develop activity may lift northeast into SE ND late in the evening or after midnight. If this occurs there will be the possibility of marginally severe wind or hail overnight. .LONG TERM...(Thursday through Tuesday) Issued at 305 PM CDT Tue Aug 31 2021 Moderate to Heavy Rain Chances... Wednesday night through Friday morning a trough moves in from the Pacific NW, with a quick moving shortwave ahead of the main system. Monsoonal moisture is driven through the low to mid levels into the northern Plains, with PW values approaching 1.25-1.75inches. Along the front associated with the trough temperature/moisture advection is strong across ensembles. Frontogenesis is relatively strong along the front, with the potential for a deformation zone developing allowing for the prolonged rain to continue past the front. Cluster analysis shows higher confidence in the chances for heavier rain, but lacks in the axis of formation of the precipitation. This is caused by the timing and propagation of the system. Faster and earlier passage doesn`t allow for further moisture/temperature advection into the northern valley limiting precipitation amounts. While a slower progression would allow for moisture to flow further toward the International border, with higher instability. This allows for higher amounts to spread across a majority of the region. Current ensembles indicator the faster propagation, with higher rain rates along I-94 points SE. At this time, chances for exceeding 0.5 inches across the area is 40-80%. High end scenario is exceeding 3.0 inches, which falls in around a 10-20% chance for areas south and east of Fargo. The Holiday Weekend... Conditions turn cooler and drier through the weekend, with highs in the mid 70s as a ridge builds west. Conditions remain dry through the holiday before rain chances increase next week. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 630 PM CDT Tue Aug 31 2021 This set of TAFs still has minimal impacts. The main issue will be increasing wind speeds Wednesday morning. The strongest winds will be felt Wednesday afternoon. Left out any mention of precipitation due to low confidence, but something is possible around KDVL by late Wednesday afternoon. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ UPDATE...Godon SHORT TERM...JK LONG TERM...Spender AVIATION...Godon
Area Forecast Discussion
National Weather Service Goodland KS
540 PM MDT Tue Aug 31 2021 .SHORT TERM...(This evening through Thursday night) Issued at 249 PM MDT Tue Aug 31 2021 Across the region this afternoon, skies are mainly sunny, albeit for the high thin veil of smoke that has been draped over the area today. A line of cumulus has formed on a boundary over portions of Kit Carson/Cheyenne counties and extending back west of Limon. Temps are currently in the 90s area-wide, albeit for extreme northwest Yuma county where upper 80s are present. With a surface low/trough meandering over the CO/KS border, winds are light for all except eastern locales where southerly flow prevails. For the remainder of the afternoon into this evening, the wx focus remains on fire wx concerns with low RH readings over portions of the area, and the threat for some thunderstorms to develop. First off, with winds light not looking for any major fires to take place, although we have monitored since spot fires have cropped off over the past several days. For thunder chances, some activity is getting going confined to south of the Interstate. The latest HRRR, NamNest have been showing some differences to start...coverage and so on for this activity, but the HRRR seems to be panning out better, albeit an hour or so early. While there might be some pea- sized hail and locally heavy downpours, the main threat looks to be strong wind gusts from the high DCape values on the SPC analysis and inverted-V soundings over the area. The activity is set to shift eastward and dissipate around the 03z Wednesday timeframe. Have opted for a 20 pop for isolated coverage this afternoon/evening, thinning out as the evening progresses. Despite the smoke thinning out afternoon sunshine some, it does not seem to be mixing to the ground, so will leave out mention at this time in the forecast tonight. Going into Wednesday, the upper ridge that had been over the south central portion of the country for the past several days, amplifies over the Plains on Wednesday and eventually shifts east enough to set up a SW flow aloft. At the surface, lee-side trough sets up over the eastern Rockies, and with high pressure east, a tight southerly gradient will ensue during the day. Gusts up to 30-40 mph are possible. The combined surface/upper flow will give the region a dry afternoon, allowing for fire wx concerns to crop up. Please refer to the Fire Wx section below. By Wednesday night on into Thursday night, precip chances on the rises area-wide. The aforementioned lee-side trough begins a trek eastward Wednesday night, in tandem with a shortwave. These will allow for some rw/trw to form. Initially in the west but coverage expands east going into Thursday as the trough shifts over the CWA and stalls as a frontal boundary. This will be the focus for further development. Some of the storms that do develop, mainly east, could be strong to severe, prompting a Marginal Risk area from SPC. For temps, highs on Wednesday still expected to remain above normal in the mid to upper 90s. On Thursday, increased chances for clouds/precip will have highs range only in the 80s, warmest areas east and south. Overnight lows will range mainly in the 60s tonight and Wednesday night. By Thursday night, mid 50s to mid 60s. For heat indices, 90s on Wednesday with highest numbers east, 80s on Thursday. Please refer to the Climate section below for information on the near record/record high temperature potential. .LONG TERM...(Friday through Tuesday) Issued at 242 PM MDT Tue Aug 31 2021 At the start of the extended period, forecast models show the CWA beginning with west-southwesterly flow aloft being between an upper air trough to the north and a subtropical ridge to the south. By Saturday, the CWA`s flow aloft has turned westerly as the top of the southern ridge moves over the CWA. On Sunday, the ECMWF shows the upper air flow turning northwesterly as the front part of a ridge over the Pacific Northwest moves over the CWA with a trough moving over the Northern Plains/Great Lakes/New England regions. The ECMWF more or less shows this pattern continuing into Monday and Tuesday as well. While the GFS depicts this same pattern as the ECMWF for Sunday through Tuesday, it also shows an upper air trough developing over UT on Sunday evening that moves over southeastern CO on Monday morning and continues southeast into TX by Tuesday. The situation will be monitored in future runs as long term models show some differences going into next week. At the surface, the CWA looks to see chances for precipitation to start the long term period with the remainder seeing relatively dry conditions. The CWA sees sees chances for showers and thunderstorms during the afternoon and evening hours of Friday ahead of a backdoor cold front that is expected to move across the area. Saturday shows chances for diurnally-driven precipitation for the southwestern half of the CWA as models display a moist air mass moving in from the south at 800 mb. As previously mentioned, Sunday through Tuesday look to stay mostly dry with possible elevated fire weather concerns seen on Monday for areas along and west of the CO border. Current forecasted minimum RH values look to go as low as 16% in parts of this area, but the limiting factor looks to be winds as they do not look to meet criteria at this time. This will be monitored in case conditions change. Also worth noting, models suggest another possible backdoor cold front moving through the CWA on Tuesday. As this is late in the extended period, timing of this possible front remains uncertain should the pattern pan out. The Tri-State area should see high temperatures on Friday in the low to middle 80s followed by Saturday seeing high temperatures around the 80 degree mark. Sunday`s highs expect to be in the middle to upper 80s followed by Monday warming to the lower 90s. Tuesday`s daytime highs return back to the lower 80s. Tri-State area overnight lows for Friday, Saturday and, Monday look to stay between the middle 50s to lower 60s. Overnight lows on Sunday stay in the upper 50s to lower 60s range with Tuesday night lows being in the lower to middle 50s. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 535 PM MDT Tue Aug 31 2021 VFR conditions are expected through the forecast period at KGLD. Visibility may be slightly reduced to 6SM due to smoke in the area. Winds become southerly overnight under 12kts. Winds remain southerly on Wednesday, increasing to 14-18kts with gusts to 25kts by 17Z. At KMCK, expect a wind shift from east to southeast between 02Z and 04Z as an outflow boundary moves through the region. Widespread thunderstorms are not expected at this time. Winds become easterly after midnight, turning to the southeast by mid- morning. Winds increase tomorrow evening to 14-18kts gusting to 25kts. && .FIRE WEATHER... Issued at 249 PM MDT Tue Aug 31 2021 Today, Elevated to Near Critical fire weather conditions are expected along and west of Highway 27 this afternoon. Humidity values will reach criteria in the lower to mid teens, while winds will stay below criteria. On Wednesday, Near Critical fire weather conditions are expected along and west of Highway 27 in the afternoon. Winds expected to reach or exceed criteria(30-40 mph), while humidity values will only drop into the upper teens to around 20 percent. && .CLIMATE... Issued at 249 PM MDT Tue Aug 31 2021 Here are the sites with potential to reach or break record highs for Tuesday, August 31st: Goodland KS 102F/1985+ Burlington CO 99F/1985 Yuma CO 101F/1948 (+) denotes multiple years for a record && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...JN LONG TERM...076 AVIATION...AW FIRE WEATHER...JN CLIMATE...JN
Area Forecast Discussion
National Weather Service Pendleton OR
847 PM PDT Tue Aug 31 2021 .UPDATE...A low pressure system over northern Washington is forecast to drift into n Idaho overheard. A few showers were associated with the low pressure but these are expected to remain north of the region and the breezy winds from earlier are forecast to lessen overnight. With the decreasing winds and mainly clear skies this will allow for good radiational cooling and temperatures are forecast to dip into the 40s with upper 20s and 30s across the higher elevations. Minor changes were done to sky and temps and winds and now the present short term forecast appears on track. && .PREV DISCUSSION... /issued 440 PM PDT Tue Aug 31 2021/ SHORT TERM...Tonight through Thursday night...An upper trough will continue to slowly move across the region tonight and Wednesday. This will keep temperatures on the cool side with breezy afternoon winds, especially along the Cascade gaps and passes into the adjacent valleys to the east. However, there will be less wind on Wednesday than today, and temperatures will be a degree or two warmer than today. The deterministic models are in good agreement with the short range ensembles such as the HREF, SREF and HRRR with the movement of this trough. The trough will linger a bit on Thursday and then exit to the east Thursday night into Friday. Expecting mostly clear and cool nights with frost in the higher mountain valley/meadow locations tonight and again Wednesday night. A slow warming trend will continue into Thursday and going into the extended forecast period. Lower elevation max temperatures will climb into the mid 70s to lower 80s by Thursday afternoon, and mid 60s to mid 70s in the mountains. Air Quality Advisories/Alerts will remain in effect for Yakima County and Deschutes county due to smoke from regional wildfires through at least midday Wednesday. 88 LONG TERM...Friday through Tuesday...An upper ridge will build over the region behind the departing upper trough on Friday. This will cause a more pronounced warming trend to take place Friday and Saturday according to the NBM guidance. The deterministic and ensembles are still in good agreement with this pattern as it evolves. Also, WPC Cluster Analysis shows not much variance each day in the extended period, especially on day 6 and 7. Afternoon maximum temperatures by Saturday will be in the lower to mid 80s...possibly approaching 90, in the lowest elevations and 70s to lower 80s in the mountains. However, there will be a slight chance of showers in the central WA Cascades and east slopes, as the upper ridge transitions to a more west to northwest zonal flow type pattern on Saturday through Sunday. However, precipitation amounts are expected to be very light. There will be a slight cool down in temperatures as well on Sunday and Monday. After that, a stronger upper high pressure system is advertised, by both the deterministic models and their ensembles, to develop by late Monday into Tuesday, with another warming trend beginning on Tuesday. This upper high pressure system may eventually have the potential to bring the forecast area back up into the 90s next week, but it is too far out into the future to have high confidence in that. In any case, summer looks like it will hang on into the first part of September, as is often the case in this region. Regional wildfires will likely continue to cause smoke issues during the extended period as well. 88 AVIATION...vfr conditions will persist at all taf sites for the next 24 hours. However brief wind gusts between 20 to 25 kts are possible at taf sites kdls and krdm and kykm until around 04z. && .PRELIMINARY POINT TEMPS/POPS... PDT 40 72 44 77 / 0 0 0 0 ALW 45 75 48 80 / 0 0 0 0 PSC 47 76 50 81 / 0 0 0 0 YKM 40 75 46 80 / 0 0 0 0 HRI 44 76 47 81 / 0 0 0 0 ELN 44 75 46 79 / 0 0 0 0 RDM 32 73 38 75 / 0 0 0 0 LGD 42 73 42 75 / 0 0 0 0 GCD 38 79 41 80 / 0 0 0 0 DLS 48 79 54 84 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...97 LONG TERM....99 AVIATION...97
Area Forecast Discussion
National Weather Service Phoenix AZ
511 PM MST Tue Aug 31 2021 .UPDATE...Updated 00Z aviation discussion. .SYNOPSIS... Scattered to widespread showers and thunderstorms will occur today over the entire region before mainly being confined to southwest and south central Arizona tonight into Wednesday. Locally heavy rainfall capable of producing flash flooding is expected, but localized damaging wind gusts will also be possible. A Flash Flood Watch is in effect through late tonight for southeast California and Yuma and until late Wednesday night for the rest of southwest and south central Arizona. A drying trend will begin on Thursday, but lingering chances for isolated storms will remain over the Arizona high terrain into the weekend. Well below normal temperatures are expected through Thursday and warming back near or just below normal by the weekend. && .DISCUSSION... Abundant moisture is being observed and analyzed across the region this afternoon with deep southerly flow. A 19Z sounding in Yuma sampled 2.1" PWATs and mesoanalysis shows most of the lower deserts around 2" with 14-16 g/kg mean mixing ratios. This will result in efficient rain producing showers and storms through this afternoon and continuing through Wednesday. 1-2"/hr rain rates will be common, with isolated higher rates in stronger showers and storms. The 18Z sub-hourly HRRR is even suggesting the potential for 3-4"/hr rates with this afternoon`s storms in parts of southeast CA and southwest AZ. This will surely lead to rapid runoff into creeks/streams, washes, and low-lying areas with the potential for flooded roadways. One thing that is already evident with ongoing storms is the tendency to redevelop and persist over the same areas for extended periods. This will only added to the flooding concerns and drive up localized rainfall amounts. This is expected to be a common feature across the region through the event with the deep southerly flow and enhanced dynamic forcing. The same 19Z Yuma sounding also calculated over 2000 J/kg SBCAPE and it has already been realized in the area with strong storms having developed. There is a threat for wet microbursts through the afternoon with the high moisture content, instability, and DCAPE values over 900 J/kg. So, in addition to the flash flood threat there is a marginal severe wind threat. The 12Z HREF has a 70% chance for wind speeds in excess of 35 mph and 10% chance for speeds over 58 mph in Imperial County. With this strong of winds, there will also be a threat for blowing dust and/or sand, which could lead to reduced visibilities. The severe wind threat decreases east of the Colorado river, but strong downdraft winds will still be possible with any storms through this event. Most active areas of showers and storms through the rest of the afternoon are favored out in southeast CA and southwest AZ, as well as in the northern AZ high terrain and southeast AZ, before transitioning more to south-central AZ later this evening. 12Z HREF is showing the greatest potential for heavy rain in Maricopa, Pinal, and Gila counties Wednesday morning with 3 hr neighborhood probabilities (for PMM) of greater than 1" of rain reaching 40-50% between 2 AM and 11 AM. Upslope regions and terrain features are likely to experience the highest rainfall totals, but there is still uncertainty in where bands of heavier rain will align, especially over the lower desert locations like the Valley. Based on the latest forecast from WPC and HREF QPF is expected to increase quickly east of Phoenix. Most likely rainfall in Phoenix continues to come down and is now only showing around 0.1-0.6" (higher to the east), but again there is still a 10% chance (based on NBM) some localized areas could receive 1.5-2" and there is equally a 10% many areas receive no measurable rain. The biggest concern Wednesday morning will be the potential for burn scar flooding, especially the highly prone Telegraph burn scar. Catastrophic flooding is certainly a possibility as the 12Z HREF LPMM is suggesting the potential for QPF up to 4-6" in this area. In coordination with WPC a moderate area for excessive rain was introduced this morning to cover the areas of greatest concern. .PREVIOUS DISCUSSION... Much drier air aloft should spread over much of the area Wednesday night into Thursday as PWATs fall to around 1.0-1.2" in south central Arizona and even lower further west, likely ending rain chances across the lower deserts by Thursday morning. Another upper level trough is forecast to approach the California coast late in the week, keeping our region mostly under southwesterly flow aloft. Lingering boundary layer moisture should prevail over the higher terrain of eastern Arizona Friday into the weekend keeping at least slight chances for afternoon storms in the forecast. Model ensembles are also starting to agree on another round of monsoonal moisture and storm chances moving back into the region late in the weekend into early next week. && .AVIATION...Updated at 0011Z South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: There are multiple aviation weather concerns through the TAF period. Latest radar imagery is showing an area of light-moderate rain/showers moving into the Phoenix area at this hour. The stratiform nature of the rain appears to be keeping TS well off to the east of the terminals at this point, but an isolated TS cannot be ruled out. The main impact from the rain early this evening will be to lower CIGS at times, perhaps as low as BKN040 with lower SCT layers at times in the heavier showers. Winds through the early evening are expected to remain out of westerly direction, with some gustiness at times. Latest High-res models are showing that -RA/- SHRA will diminish somewhat after 03-04Z as the 1st batch of rain moves off to the north, but confidence in the timing of this semi- break is low-moderate at best. A more substantial period of showers is anticipated to begin shortly after midnight, then continue into the early/mid morning hours on Wednesday. Chances for a sanguined period of CIGS aob 4k feet (with lower SCT layers) are in the 30-40% range. An isolated TS cannot be ruled out, but confidence is far too low to include TSRA/VCTS in any of the TAFs at this point. Wind directions during this period are a bit uncertain, but likely will favor a light southerly direction at this point. Gradual improvement in the CIGS is expected during the late morning/early afternoon hours on Wed as drier air moves into the region from the west. Winds are expected to become westerly by late afternoon as well. Wed evening will feature clearing skies with a more typical diurnal easterly wind returning by mid/late evening. Southeast California/Southwest Arizona including KIPL and KBLH: There are multiple aviation weather concerns through this evening. Storms and showers over the region are expected to continue to affect the KIPL area thru about 02-03Z and the KBLH area thru about 05-06Z. Direct storm impacts will include lightning, strong downbursts, and temporarily reduced cigs and visibility. Drier air moving in from the south will then bring clearing skies and end the TS threat by late tonight. Dry conditions are then forecast for Wed with just some SCT-BKN mid-level CIGS in the TAFs. Once the TS activity ends, winds at KIPL will become mainly southeasterly and southerly at KBLH thru the remainder of the TAF period. && .FIRE WEATHER... Thursday through Monday: After wetting rains fall across much of the region on Tuesday and Wednesday, drying conditions are expected from west to east on Thursday to temporarily end rain chances for all but the eastern Arizona high terrain. After mostly slight chances for isolated showers and thunderstorms across the higher terrain on Friday and Saturday afternoon, storm coverage should increase across the higher terrain by Sunday or Monday. Outflows from these storms and another potential weather disturbance from the east may trigger storms over the lower deserts of south central Arizona on Sunday and the entire region on Monday. Winds will generally follow diurnal trends aside from stronger gusts in thunderstorm outflows. Minimum Minimum RHs will remain above 25-30% for south central Arizona, whereas southeast California and southwest Arizona may briefly dip to 15-20% on Friday and Saturday. Maximum RH values will recover into a 40-70% range for most locations each night. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Flash Flood Watch through late Wednesday night for AZZ530-531- 533>563. Flash Flood Watch through late tonight for AZZ532. CA...Flash Flood Watch through late tonight for CAZ560>570. && $$ DISCUSSION...Benedict PREVIOUS DISCUSSION...Hopper/Kuhlman AVIATION...Percha/AD FIRE WEATHER...Hopper
Area Forecast Discussion
National Weather Service Reno NV
242 PM PDT Tue Aug 31 2021 .SYNOPSIS... Breezy conditions on Wednesday bring lingering concerns for rapid fire spread for portions of the Sierra and far western Nevada. Lighter winds are on tap Thursday into early next week. Smoke and poor air quality will continue to plague portions of northeast CA and western NV. A gradual cooling trend is expected through Thursday before temperatures gradually warm through the weekend. && .DISCUSSION... An upper low over the northwestern CONUS and southwestern Canada will slowly move northeast into the central Canadian provinces Wednesday-Thursday. A residual weak trough will remain over the West late week before an upper ridge strengthens over California and Nevada over the weekend into early next week. After above average highs today (lows remain seasonably cool to chilly), the residual trough will serve to keep temperatures moderated to near average through Friday before they gradually rise through Monday under the building ridge. Highs look to top out around 4-8 degrees above average (valleys 80s to lower 90s) early next week. Winds through Wednesday along with smoke for the foreseeable future continue to be the main concerns for northeast CA and western NV. Details below... * WINDS: Breezy southwest-west to continue into this evening with gusts 25-35 mph, locally to 40 mph, in valley locations and up to 50 mph over high ridges across northeast CA and far western NV. Winds are lighter out in west-central NV at this time but should pick up some for late afternoon and evening as the pressure/thermal gradient maximizes. The breezy conditions will cause lake chop, today in particular when advisories remain in effect for some area lakes. Winds on Wednesday will be lighter than today, more similar in speeds to what we saw on Monday with gusts 20-30 mph, locally up to 35 mph in wind prone locations. Lighter winds still are expected for Thursday as some cooling across the region diminishes thermal gradients. Friday into early next week, generally light winds are on tap. * SMOKE: Based on what occurred last night and this morning along with the latest HRRR smoke models, the places that look to be hardest hit (longest duration, worst air quality) from Caldor Fire smoke through early Thursday include areas near/south of Highway 50 across western NV, and north of Alpine County including Lake Tahoe for eastern CA. As happened this morning, substantially degraded air quality looks to work its way into the Reno-Sparks area again Wednesday morning and probably Thursday morning as well, although afternoon westerly winds should again clear the air for Wednesday afternoon and evening. Downwind of the Dixie Fire, areas across portions of Lassen and Plumas counties into northern Washoe County and east into Pershing and northern Churchill counties look to be most affected. As we go into late week, flow in the smoke-bearing layer up to around 700 mb go more southerly. While smoke modeling is not yet available (only goes out to late Thursday morning), the flow aloft along with lighter surface flow would suggest worsening smoke and air quality for areas north of Lake Tahoe and into the Reno-Sparks area as daytime mixing works smoke aloft from the Caldor Fire down into valleys. -Snyder && .AVIATION... Greatest concerns through Wednesday across northeast CA and western NV continue to be gusty SW-W winds and the continued smoke and haze. Wind gusts into this evening should peak 25-35 kts. Winds at FL100-140 forecast to be sustained around 20-35 kts through Wednesday with turbulence across and downwind of the Sierra. A shear layer may also be present tonight and Wednesday morning downwind of the Sierra as winds remain elevated aloft. Winds will be slightly weaker for Wednesday, similar to yesterday`s speeds with gusts 20-25 kts. Smoke to continue to bring terrain obscuration and slantwise visibility reductions to many areas. Based on HRRR smoke models, the places that look to be hardest hit through Wednesday include areas from KTVL-KMEV-KNFL with sub-minimum landing criteria likely for large amounts of time for KTVL/KMEV. Also, as happened this morning, substantially degraded VIS (MVFR at least) looks to work its way into the KRNO area again Wednesday morning before the air clears for the afternoon with westerly winds. Downwind of Dixie, areas across portions of Lassen and Plumas Counties into northern Washoe County and east toward KLOL and KWMC look to be most affected. -Snyder/Dawn && .FIRE WEATHER... * Red Flag Warnings continue through this evening for northeast CA including the Dixie Fire, Tahoe Basin including the Caldor Fire, and into northwest NV for gusty winds and low humidity. * Gusty winds and low humidity will exacerbate ongoing fires and increase the threat of significant fire growth for much of the region. Please listen to all advice from local authorities, especially if you are in the path of the Caldor and Dixie Fires. * Red Flag Warnings remain in effect through Wednesday evening for the Tahoe Basin (including the Caldor Fire), Sierra Front, and northern Mono County. * Poor overnight recoveries for mid slopes and ridges occurred overnight and are expected again tonight. Wind gusts are starting to surface across the region with observations generally in the 25-30 mph range. This will continue through the early evening with the strongest gust potential of up to 30-40 mph through about 6-7pm this evening particularly along US 395/I-580 along the Sierra Front. As a dry slot moves across the region, a very dry and unstable air mass is currently overhead yielding an environment supportive of plume dominated growth with a Haines index of 5-6 in place region wide. Winds remained elevated in thermal belts and along ridgelines overnight and similar conditions are anticipated tonight as well. Winds will be a bit weaker Wednesday, similar to what was experienced Monday with gusts 25-30 mph, locally to 35 mph in wind prone locations. Unstable conditions will also prevail on Wednesday, which along with the very receptive fuels means the high fire danger continues through Wednesday. Fuentes/Dawn && .REV Watches/Warnings/Advisories... NV...Red Flag Warning until 11 PM PDT Wednesday for Lake Tahoe in NVZ420-421. Lake Wind Advisory until 9 PM PDT this evening NVZ003-004. Red Flag Warning until 11 PM PDT this evening NVZ458. CA...Red Flag Warning until 11 PM PDT Wednesday for Lake Tahoe in CAZ272. Lake Wind Advisory until 9 PM PDT this evening CAZ073. Red Flag Warning until 11 PM PDT this evening CAZ270-271-278. && $$ For more information from the National Weather Service visit...
Area Forecast Discussion
National Weather Service Springfield MO
702 PM CDT Tue Aug 31 2021 .SHORT TERM...(This evening through Wednesday) Issued at 215 PM CDT Tue Aug 31 2021 Remnants of convective complex were rapidly falling apart over southern MO early this afternoon as it moved into less favorable atmospheric conditions. Still could see a few showers/storms develop along the outflow over southern MO this afternoon. CAMS models develop some additional convection tonight, but are having a difficult time with placement of convection. The HRRR seems too far east, as the better instability and moisture should be over our far western CWA late tonight. Will continue low end pops over the western half of the CWA for now. Lows tonight should dip into the mid 60s in the east and around 70 out west. Upper ridge will then begin to build into the area on Wednesday and should end the precipitation chances. Temperatures will range from the mid 80s in the northeast to the mid 90s in the southwest. The southwest corner of MO and the southeast KS counties may be around 100 for the heat index on Wednesday. .LONG TERM...(Wednesday Night through Tuesday) Issued at 215 PM CDT Tue Aug 31 2021 The upper level ridge axis will be from Texas into the western great lakes on Thursday. Will see temperatures from the mid 80s in the east to the low 90s out west and possibly some mid to upper 90s heat index values out west. From Thursday night through Saturday, we`ll see a shortwave trough push across the northern plains, upper Mississippi valley and into the Great Lakes region which will flatten out the ridge and bring a surface front into the area Friday night into Saturday. The front will aid in scattered shower/thunderstorm development late Friday into Saturday in the upcoming holiday weekend. High pressure behind the front will slide to the east of the area on Sunday with a return to southerly winds on Sunday night and Monday. Another shortwave will track southeast across the upper Mississippi valley on Tuesday bringing another cold front into the area with additional rain chances. Less confidence in temperatures in the later periods with larger variance in ensembles. Sticking with the NBM at this time which continues to yield mid 80s to low 90s across the area. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 652 PM CDT Tue Aug 31 2021 KSGF/KJLN/KBBG tafs: Generally VFR for the period with two possible brief exceptions. High based/sparse coverage showers/thunderstorms may develop in the 10z-14z time frame over parts of southwest Missouri in response to lift with a veering low level jet/flow and elevated instability. Some light ground fog/haze will also briefly be possible toward 12z in some low terrain areas/lakes with weak low level winds/surface (radiational) cooling. Otherwise, light northeast-east winds will continue with a ridge of high pressure extending from the western Great Lakes to the Ozarks. && .SGF WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && $$ SHORT TERM...Lindenberg LONG TERM...Lindenberg AVIATION...DSA
Area Forecast Discussion
National Weather Service Topeka KS
548 PM CDT Tue Aug 31 2021 ...AVIATION UPDATE... .DISCUSSION... Issued at 304 PM CDT Tue Aug 31 2021 Outflow from the early-day convection has pushed southwest into south-central Kansas and southern Missouri as of 19Z. Modest lee troughing was over the central and northern High Plains under better westerlies still to the north. Weak surface high pressure and easterly flow was over the upper Mississippi Valley with some areas of stratus. Upstream water vapor imagery showing a large upper low over southern British Columbia and another weaker wave off Baja with several areas of convection in western Mexico. As the old tropical system continues northeast out of the southeastern states and the northwestern low nudges east, upper flow locally become more northerly as surface winds back to a east- northeast direction. Models continue to struggle on where the best resulting isentropic lift will focus tonight with decent signals on the 310 and 305 K surfaces, though most solutions have it in far eastern Kansas into western Missouri and have increased precip chances in the eastern counties. Instability also varies considerably, though the mean would less than 1000 J/kg. Effective shear also limited by weak overall flow and this combination should keep any storms from being too strong. Can`t rule out some training convection in this setup for some locally heavy amounts with PW values around 1.5 inches. Any precip should weaken in the early morning though another round can`t be completely ruled out Wednesday night but ascent is weaker. The western circulations earlier noted work east and northeast, respectively, tonight into Thursday. A weak front is nudged into the area Thursday night into Friday as very warm air aloft and quite high and deep moisture advects in. PW values from the NAM and GFS are near record values though ESAT values near not quite as impressive but trending up. CAPE values get limited somewhat as a result and the main impact from this front could be heavy rain with the front becoming aligned with the upper flow Thursday night into Friday along with some indications of another shortwave passing Friday night. The Canadian low moves into the Great Lakes by late Saturday and should help usher drier conditions in for the remainder of the holiday weekend. Thursday looks to be warmest day of this forecast with some locations returning to the mid 90s ahead of the front. Labor Day may also be on the warm side as southwest winds look to return ahead of another front in northwest flow Tuesday. && .AVIATION...(For the 00Z TAFS through 00Z Thursday) Issued at 548 PM CDT Tue Aug 31 2021 The RAP and NAM continue to show a narrow axis of isentropic upglide near the terminals overnight. Forecast soundings indicate a fair amount of elevated instability with some bulk shear, but the CAMs are not that excited about coverage of storms and are hit or miss with regards to the terminals. May include a VCTS in the forecast and wait to see where the upglide sets up to be more specific. An easterly low level wind is expected to advect a moist boundary layer into central KS overnight. This should lead to some MVFR stratus forming through the mid morning hours. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION...65 AVIATION...Wolters
Area Forecast Discussion
National Weather Service Las Vegas NV
801 PM PDT Tue Aug 31 2021 .SYNOPSIS...Moisture from the remnants of Nora will lead to a risk of heavy rain through Wednesday. A Flash Flood Watch is in effect for parts of Clark and San Bernardino Counties and all of Mohave County. Deep moisture exits to the east later this week for decreasing chances for thunderstorms. However, that may be brief as moisture and storm chances could return by the end of the holiday weekend. && .UPDATE...Scattered thunderstorms will continue through the evening and into the overnight period mainly east of the I-15 corridor. Some of the storms this evening over San Bernardino and Mohave counties have been producing rainfall rates in excess of 2 inches per hour indicating the ample moisture that remains in place, and no changes have been made to the Flash Flood Watch that is currently in place. The deeper moisture will begin to move farther east tomorrow decreasing the heavy rain threat from west to east. Additionally, the latest HRRR smoke model continues to show smoke from the Caldor fire moving into Esmeralda county overnight and the weather grids have been updated to reflect this. No other major changes to the grids were needed this evening. && .PREV DISCUSSION... 109 PM PDT Tue Aug 31 2021 .SHORT TERM...through Thursday night. Multiple circulations evident on satellite loop today, with at least two MCVs over our CWA and the main upper low spinning just west of Baja. New convection has been a little slow to develop, but the extra lift from the circulations plus the eroding debris clouds will allow storms to pop this afternoon, mainly near and east of a line from Morongo Valley to Mount Charleston to Rachel. Instability should persist much of the night, and there should be just enough shear to keep storms going all night with a threat of pulse severe, but not long lived organized severe. Flash flooding remains the biggest concern, as the aforementioned instability and shear coexist with deep tropical moisture (precipitable water of 1.5 inches as far north as Laughlin and 1.8 inches at Lake Havasu City as of late morning). The areal extent of the Flash Flood Watch looks good, but the timing may be in question. As the upper low off of Baja slowly drifts inland tomorrow, the deepest moisture should be redirected farther east, possibly ending the flash flooding threat early. However, there is not enough confidence in this to change the valid time of the Watch. Will monitor and cancel early if needed. Once the flash flooding risk is finally over Wednesday night (or perhaps earlier), Thursday will see precip chances limited to the eastern half of Mohave County and possibly the Spring Mountains. Temperatures will be below normal today and Wednesday, especially in areas that see clouds and rain, with a warming trend beginning Thursday as the moisture shifts east. .LONG TERM...Friday through Tuesday. Dry conditions are expected Friday and Saturday with weak southwesterly flow in place across the area. Both the GFS and ECMWF ensembles are showing high pressure rebuilding across the Four Corners region by the end of the weekend. Southeasterly monsoonal flow associated with this high will push higher PWAT levels into the Colorado River Valley by Sunday afternoon, returning the chance of thunderstorms to Mohave County. Moisture should spread further west Monday and Tuesday, increasing thunderstorm chances across southern Nevada and eastern California. && .AVIATION...For McCarran...Increasing confidence that there will be moderate impacts due to thunderstorms in or around the Las Vegas Valley today. Best chances for thunderstorms impacting KLAS & surrounding terminals will be between 22-01Z today. Vicinity showers and thunderstorms will be possible thereafter as well, potentially remaining through Wednesday morning. Potential impacts associated with storms in and around the Las Vegas Valley include brief heavy rainfall that could result in reduced visibility over the terminal, gusty outflow winds, and lightning. Outside of thunderstorm influences, winds should be favoring a southeast to southerly direction around 8-10 knots with occasional gusts to around 15-20 knots through the afternoon. Winds will decrease overnight, becoming light and variable. SCT to BKN aoa 10-12 kft this afternoon with BKN aoa 7-8 Kft persisting overnight. There`s a non-zero chance that ceilings could drop to around 5 Kft overnight/early tomorrow morning. For the rest of southern Nevada, northwest Arizona and southeast California...Isolated to scattered thunderstorms are possible again this afternoon, with better chances later tonight across southeastern portions of our region, including in and around the Colorado River Valley and potentially KDAG. High confidence on storms impacting KIFP, KEED at some point tonight between 03-07Z Wednesday. Low confidence on any storms impacting KDAG directly, but vicinity thunderstorms maybe within 15 miles at times. Main concern would be heavy rainfall reducing visibilities over the terminals, outflow winds, and frequent lightning. SCT to BKN aoa 10-12 kft this afternoon with BKN to OVC aoa 7-8 Kft persisting overnight for KIFP & KEED. There`s a non-zero chance that ceilings could drop to around 5 Kft overnight/early tomorrow morning impacting KIFP & KEED. Further northwest, expect FEW-SCT aoa 12 Kft with some occasional breezy winds in the afternoon. That said, haze from distant wildfire smoke will reduce slant range visibility at times, especially across the Sierra and parts of the southern Great Basin. Not anticipating smoke/haze to impact KBIH overnight tonight/early tomorrow morning at this time. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ UPDATE...Planz SHORT TERM...Morgan LONG TERM...Planz AVIATION...Peters For more forecast information...see us on our webpage: or follow us on Facebook and Twitter