Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/30/21

Area Forecast Discussion
National Weather Service La Crosse WI
1056 PM CDT Thu Jul 29 2021 .SHORT TERM...(This evening through Friday) Issued at 240 PM CDT Thu Jul 29 2021 Canadian wildfire smoke is being shuttled southward across the area in northerly upper level flow downstream of Rockies to High Plains upper ridge. The smoke is rather dense and is making it down near surface in areas of WI, IA and especially across MN where visibilities are being restricted to 1-5 miles. Air Quality Alerts are in place for MN and recently issued for IA as well. Satellite shows a marked decrease in smoke upstream over portions of southern Canada and the Arrowhead of MN, and HRRR Vertically Integrated Smoke suggests we could see some diminishing late tonight before another infusion of smoke on Friday with point source primarily fires near the Manitoba and Ontario border. Aside from the smoke, the only other forecast item of note is chance of rain, primarily Friday afternoon into Friday night. Better moisture, instability and lift is depicted to our south, thus any unfortunately rainfall amounts look to be light for some of our south/southwest counties in moderate to severe drought. The rain could limit highs Friday into the lower 70s in some areas south. .LONG TERM...(Friday night through Wednesday) Issued at 240 PM CDT Thu Jul 29 2021 Flow pattern aloft looks to remain stagnant with ridging entrenched out west and broad troughing east. This will lead to a continuation of northwest flow and generally a drier and cooler regime. Embedded within the northwest flow will be a couple of stronger shortwaves and rain chances. The first one still slated for Saturday PM/eve with an attendant cold front. Bulk shear has trended weaker from yesterday to around 20-25 kts 0-6km, while instability fairly unchanged with around 1000-1500 j/kg CAPE, but still sufficient to perhaps foster a few stronger storms potentially. The cold front will then usher in a cooler and drier airmass for the end of the weekend into the start of next week, with very pleasant highs in the 70s to near 80 and lows in the 50s. There is a signal for another stronger shortwave and cold front heading toward the middle of next week accompanied by rain chances. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1057 PM CDT Thu Jul 29 2021 The main concern for aviation is whether the wildfire smoke is going to remain in the area to produce additional visibility reductions Friday. Base on surface observations, most of this has been pushed west of the Mississippi River with the MVFR reductions confined to areas west of Interstate 35. The HRRR suggests the smoke will start to return to the area later Friday as the surface ride slips to the south allowing the winds to come back around to the southwest. This could bring some visibility reductions back into the area, but confidence on how quickly this may occur is not high enough to include in the last part of the forecast. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...McClure LONG TERM...McClure AVIATION...04
Area Forecast Discussion
National Weather Service Cheyenne WY
530 PM MDT Thu Jul 29 2021 .SHORT TERM...(This evening through Sunday) Issued at 405 PM MDT Thu Jul 29 2021 Forecast challenges deal with heavy rainfall and possible severe weather through Saturday in the short term. Currently...Frontal boundary lays across far northeastern Colorado to a surface low near Cheyenne and then from Laramie to just west of Casper this afternoon. SPC surface based CAPE on the order of 3000 J/KG down here near Cheyenne to around 2000 J/KG out by the storm ongoing just south of Arlington. Have been getting reports of heavy rain/flash flooding in a pretty data sparse area west of Laramie. Latest short term guidance showing storms developing west of the Laramie Range through the late afternoon, HRRR showing storms developing east of the Laramie Range across southern Platte and southern Goshen Counties around 02Z and continuing through at least 06Z tonight. Cheyenne and CFD may be spared thunderstorms this evening as we have been down in stratus all day. Any outflow boundaries from the north would really throw a wrench in the kept fairly high chance PoPs in the forecast for here. Best surge of monsoon moisture Friday with PWATS up near 1.3 inches at Laramie and Rawlins. Long skinny CAPE profiles on forecast sounding with little in the way of looking at heavy rain producers. WPC has a SLight Risk area identified for flash went ahead and issued a Flash Flood Watch for parts of Albany and eastern Carbon County. Will need to watch the Mullen burn scar area closely as they are right in the bullseye of this heavier precip Friday afternoon. .LONG TERM...(Sunday night through Thursday) Issued at 405 PM MDT Thu Jul 29 2021 Trends for next week have been on track for a gradual decrease in moisture across the southeastern CONUS, with a slight increase in temperatures through Thursday as an upper level ridge begins push eastward. Guidance has been a bit bullish with POPs, especially on Tuesday afternoon. PW anomalies have indicated a stronger decrease in moisture across with a lowering to 0.4 to 0.75 inches, with the GFS drastically reducing areal coverage of showers and thunderstorms. Went ahead and started trending POPs down 10% to account for this uncertainty. Can still see a chance for afternoon thunderstorms with brief northwesterly flow on Tuesday and several embedded shortwave throughout the week. Daytime highs are expected to increase, relative to the cooler weekend, with highs in the low 90s east of I-25 and in the mid to low 80s to the west. Overall, not too many fire weather concerns through the end of next week as minimum RH values remain above 20 percent and winds remain below criteria. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 523 PM MDT Thu Jul 29 2021 VFR conditions will continue for all TAF sites until 09Z for southeastern Wyoming and until 12Z for the western Nebraska Panhandle due to possible fog conditions. Thunderstorms will push eastward across the region starting at KLAR until 03Z and KCYS until 04Z. Light rainfall is possible for KCYS until 07Z and skies will remain BKN along with low cloud bases for all sites. Low visibility and MVFR conditions are possible for KRWL until 15Z and KCDR until 18Z. && .FIRE WEATHER... Issued at 405 PM MDT Thu Jul 29 2021 Minimal fire weather conditions over the next few days as monsoonal moisture surges into the area from the south. Expect widespread wetting rains Friday and Saturday across southern areas. Areas further north will see lesser amounts of rain...but humidity expected to remain high. Afternoon showers and storms expected on a daily basis through the weekend before monsoonal moisture shifts south back into Colorado. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Flash Flood Watch from Friday morning through Friday evening for WYZ105-110-114>116. NE...None. && $$ SHORT TERM...GCC LONG TERM...MD AVIATION...AW FIRE WEATHER...GCC
Area Forecast Discussion
National Weather Service Des Moines IA
648 PM CDT Thu Jul 29 2021 .DISCUSSION.../Tonight through Thursday/ Issued at 305 PM CDT Thu Jul 29 2021 Forecast Highlights: -- Sultry southern Iowa with a chance of storms into this evening -- Smoke sinking southward into Iowa this afternoon and tonight causing visibility reduction; lessening on Friday -- Showers and storms re-enter the state, particularly later Friday into Saturday morning -- Lower humidity, around seasonal temperatures Sunday into middle of next week Details: There are three main concerns in the near term forecast with heat (1) and storm chances (2) over southern Iowa and reduced visibility due to smoke from Canadian wildfires (3). Temperatures are well into the 80s if not the low 90s with high dewpoints in the upper 70s or low 80s over southern Iowa this afternoon. This is where the current heat index values are in the 105 to 110 degree range and will let the heat advisory continue until early this evening. The front that caused isolated showers and storms along I-80 and just south shortly after sunrise this morning and has continued to caused storms over southeastern Iowa and points southeast now resides near the Iowa/Missouri border. The front will serve as an area of convergence for possible scattered storm development back into central Iowa this afternoon and evening. The moisture rich airmass over southern Iowa has created a high instability environment with MLCAPE values eclipsing 4000 if not 5000 J/kg, but deep layer shear is marginal around or less then 25 knots at present. Still, storms that are able to form could become become severe. Forecast soundings show that as the boundary layer has warmed through the day, the moisture has remained fairly steady resulting in inverted v soundings with downburst gusty wind potential. In addition, given the high instability within the hail growth zone, severe hail is also possible. It does remain uncertain if storms will develop over our far southern counties or over northern Missouri. SPC mesoanalysis shows and forecast 700mb also indicate there is an area of 12C+ temperatures north of the front that will move over southern Iowa. Where 700mb temperatures are lower, like the RAP and HRRR forecast show now around 11 to 11.5C at KLWD, this may allow with convergence along the front to get storms to start around the 20z to 22z period. Will be monitoring the 1 minute imagery from GOES-East to see if any initial anvils orphan giving an indication to a cap that is weakening. Storms that do develop in Iowa will slowly move southeastward, but with the front stalling and lingering over southwestern Iowa activity may remain to some degree overnight over this area. Other concern today into tomorrow morning will be haze and near surface smoke from Canadian wildfires. 6z/12z HRRR smoke has been showing an extensive area of high smoke concentration not just aloft, but at the surface. This shows up best in the CIRA GeoColor RGB and particularly looking at the nadir view. The smoke is even visible easily at midday in the GOES-East visible channel, denoting just how high the concentrations are in the atmosphere. While we have typically added sky cover for the upper level smoke that causes an opaqueness to an otherwise blue sky, there have been surface visibility reductions over Minnesota. Those even moved into our far northwestern forecast area this morning with Estherville dropping down to 3 miles in haze, which there are at once again this afternoon. As the smoke moves down this afternoon into tonight, have haze and smoke in the forecast to account for the surface visibility impact. In addition, the Iowa DNR, which monitors air quality over Iowa, has decided to issue an air quality alert, which our office has relayed for the Iowa DNR. There should be a minimum in scattered shower and storm activity along the boundary south and west of Iowa Friday morning. As the mid- level ridge over the central US is gradually pushed back to the southwest of the area due to troughing pushing down over northeastern North America, this will allow for a shortwave trough to move over the state. This shortwave will help to invigorate convection along the surface front, which compared to 24 hours ago is farther northeast. Still, the highest chances for rainfall will be from northwest into southeast Iowa later Friday into Saturday. There could be a short window for a few strong storm with moderate instability Friday afternoon and higher deep layer shear over southwestern Iowa. On the heavy rainfall side, precipitable water values will top 2 inches over southwest Iowa with warm cloud depths over around 4500m. Forecast guidance shows that a swath of 1 to near 3 inches is possible from western into south central Iowa. Mitigating water issue concerns is the recent dry stretch with crops able to take quite a bit of rain in addition to 850-300mb flow that does strengthen overnight Friday. As a shortwave trough drops into the Great Lakes with surface low pressure moving through Ontario, a secondary cold front stretched back into our region will finally push through Saturday night. At this time, eastern Iowa and points eastward would be favored for scattered storms as this drops through the region. Sunday into the middle of next week, a large area of high pressure settles over the region. This will bring lower humidity and dewpoints and more seasonal temperatures through this period. As the high begins to move off to the east late in the week, moisture will begin to return to the region. && .AVIATION.../For the 00Z TAFS through 00Z Friday evening/ Issued at 647 PM CDT Thu Jul 29 2021 Main aviation impacts are going to be visbilility restrictions due to the wildfire smoke moving south behind frontal passage earlier today. MVFR visibilities will be most likely, but there will be periods dipping into IFR. Greatest threat being across northernmost terminals. Confidence decreases somewhat further south, but did add some visibility reductions into KDSM and KOTM for a time after 05z or so. Conditions should improve somewhat as the air mass mixes after 13-15z tomorrow. Also added VCSH to KFOD tomorrow afternoon as convection chances begin increasing. May need to expand to other sites as well, but will await 00z data to add confidence to the where and when. && .DMX WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 7 PM CDT this evening for IAZ070>075-081>086- 092>097. && $$ DISCUSSION...Ansorge AVIATION...Hahn
Area Forecast Discussion
National Weather Service Grand Forks ND
748 PM CDT Thu Jul 29 2021 .UPDATE... Issued at 748 PM CDT Thu Jul 29 2021 Surface high pressure will pushing across the area overnight and continue to move some of the lower level smoke from the area. Increasing westerly flow aloft will bring additional smoke into the area aloft in its stead. Expect northerly winds to turn light and variable overnight, and then increase form the south on Friday. An update Aviation Discussion is attached below. && .SHORT TERM...(This evening through Friday night) Issued at 250 PM CDT Thu Jul 29 2021 Poor air quality due to smoke continues at least into the evening, with localized visibility restrictions under 1 mile in the thickest areas of smoke. Regarding smoke/air quality: Northerly flow remains in place through this evening. Later this evening/overnight a mid level shortwave and associated surface low pass through SD and this will allow for low level flow to shift to the west-southwest and may bring a few light showers to our far southwest near the SD state line. Surface winds may remain light and variable, so while there will be some improvement (as already see in the northern RRV) smoke may become trapped below the nighttime inversion. HRRR smoke model is more optimistic as the night goes on, but past events we saw smoke impacts linger until breezier west-southwest winds developed and mixed out what smoke was trapped within the RRV. This would not be expected until after daytime mixing gets underway Friday morning. Friday-Friday night: A weak shortwave within NW flow passes main northeast, with weaker PVA during the afternoon/evening over our CWA. Westerly flow/WAA ahead of the associated cold front will allow for warmer temps and highs may reach the mid/upper 80s (cloud/smoke dependent). There isn`t a lot of moisture advection, but there may be enough instability/forcing for showers and thunderstorms to develop upstream and move southward into northeast ND and northwest MN before weakening/falling apart further south. Severe doesn`t appear to be favored, however there is some indication of pockets of MUCAPE 1500-2000 J/KG near the International Border during peak heating that may support isolated strong storms as the front passes. These are likely dependent on lapse rates/clearing and confidence isn`t high as moisture advection in the BL and aloft will be minimal. One unfortunate result of the cold front and building Canadian high pressure will be a return to long-fetch northerly flow from the Canadian wildfires in Manitoba/Ontario which will likely carry thick wildfire smoke back into our region late Friday night into Saturday morning. .LONG TERM...(Saturday through Thursday) Issued at 250 PM CDT Thu Jul 29 2021 Not much to talk about starting August. The last day of July will feature breezy northerly winds, keeping the more northerly locations along the international border in the 70s for highs. A ridge continues to dominate the upper levels. As the week begins, this ridge will shift back to our west. Unfortunately, the heat of the summer will continue for the foreseeable future with this pattern, as hot and dry conditions will continue. There is some hinting in the guidance that we could see some precipitation mid week next week, however, it will not be a drought buster. Confidence is low in terms of amounts and locations, so not much else can be said except we are seeing some signals for precipitation in the first week of August. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 748 PM CDT Thu Jul 29 2021 Expect generally VFR conditions across eastern ND and the Red River Valley corridor with variable visibility in smokey skies at low to mid levels aloft. Areas of MVFR vsbys in smoke will stretch across northwest and west central MN this evening and overnight... with conditions slowly improving from west to east by early morning. Winds will be light out of the north, becoming light and variable overnight, and turning from the south through the morning from the south. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ UPDATE...Gust SHORT TERM...DJR LONG TERM...AK AVIATION...Gust
National Weather Service Hastings NE
658 PM CDT Thu Jul 29 2021 .DISCUSSION...(This evening through Thursday) Issued at 344 PM CDT Thu Jul 29 2021 Overall scenario is a weak boundary that has stalled and bifurcated our CWA. This boundary is somewhat detectable using streamlines, and using dew point/heat index data to detect moisture pooling along the boundary. Deep layer shear is weak, but MLCAPE is moderate to high, and quite high along a very narrow corridor adjacent to the boundary that has all but stalled. Not much of a cap to bust today, and the past few runs of the HREF have indicated that a narrow corridor of 30-50 percent coverage of convection may occur, with quite efficient rainers in store. With the combination of high instability and low shear along the stalled boundary could actually spin up a couple of landspout tornadoes if cells last long enough in this pulsey environment. And of course a couple of strong to marginally severe storms are quite possible as well. This development will closely correlate to daytime heating, so when the sun sets this evening, it is only a matter of a couple of hours that the storms will lose their punch and decrease in coverage (if they develop). Already see CU fields near I-80, slightly north of the axis of highest POPS in the forecast. I did include 20 POPs as far south as parts of north central KS as HREF has stubbornly included this area to be watched, and sure enough, some CU have developed there as well. This boundary should eventually move north overnight a bit and will set us up for higher dew points on the Nebraska side, with dew points with more moisture pooling, but actually mixing out a bit farther south in KS. More storms could fire along the boundary tomorrow, with storms firing again near the boundary in a similar environment as today, but just focused a tad more into our north/northeast CWA. More strong to severe storms will be possible in the late afternoon and evening. A heat advisory has been issued for parts of south central NE and north central KS for the heat index. The HRRR smoke model strongly indicates we will have some smoke mix down tonight into Friday, focusing most of the smoke and smokey haze in our north. Finally cooling down Saturday behind the long awaited push south of the boundary as the upper ridge shifts a bit west and surface high pressure builds in from the north. Dew points will take an extra day to dry out, and for Sunday we will be noticeably drier and the more comfortable conditions will stick around for a good few days. Could see some storms firing in our south for Saturday as the front takes time to completely clear the CWA, and would not be out of the question for a strong storm to develop in our far south for Saturday afternoon as well. After the dry Sunday/Monday, small POPs return by late Monday night into Tuesday into mid week with return flow. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday) Issued at 648 PM CDT Thu Jul 29 2021 Fairly difficult forecast regarding ceilings and visibility. First for ceilings, we have MVFR ceilings that are irregularly shaped and have been quite stubborn in the vicinity all day, especially to the north and have at least temporarily set up in the KGRI area. Movement of this stratus is rather erratic and shape shifting, so predicting development is quite difficult as models do not seem to have a very good grasp. This does have the hallmarks of persisting for at least a few hours, judging by stratus history all day to the north. Also, we have a wildfire smoke problem with smoke mixing down to the surface originating from fires in Canada. HRRR smoke model indicates a lowering of visibility to MVFR for KGRI, and may be a touch earlier than what is indicated in the forecast if latest observations to the north are an indicator. Any shot at 1SM should remain north of both terminals. Wind should remain relatively light as flow near the surface boundary will be weak and flow aloft is weak as well. && .GID WATCHES/WARNINGS/ADVISORIES... NE...Heat Advisory until 9 PM CDT this evening for NEZ046>049-060>064- 072>077-082>087. Heat Advisory from noon to 9 PM CDT Friday for NEZ062>064- 075>077-085>087. KS...Heat Advisory until 9 PM CDT this evening for KSZ005>007-017>019. Heat Advisory from noon to 9 PM CDT Friday for KSZ006-007-018- 019. && $$ DISCUSSION...Heinlein AVIATION...Heinlein
Area Forecast Discussion
National Weather Service Goodland KS
543 PM MDT Thu Jul 29 2021 .SHORT TERM...(This evening through Friday night) Issued at 327 PM MDT Thu Jul 29 2021 Short term forecast concerns are going to remain hot temperatures with dry conditions and the possibility of smoke from forest fires over the western U.S. moving through the area. High pressure aloft remains centered over the central High Plains region during the day on Friday with a surface low consolidating over eastern Colorado that moves across the forecast area Friday night along with a cold front. Cooler temperatures are expected behind that cold front. Also concentrated behind that cold front, some of the smoke from fires over the western U.S. and Canada is being shown by the HRRR to be concentrated near the surface on the northern side of the cold front. The area of concentrated smoke near the surface may be enough for some folks to smell, create air quality issues, and produce areas of haze and reduced visibility in smoke if concentrations end up being high enough. Have decided to go ahead and bring smoke and haze into the area overnight Friday night into early Saturday morning. .LONG TERM...(Saturday through Thursday) Issued at 327 PM MDT Thu Jul 29 2021 The forecast focus shifts from hot temperatures to the possibility of additional haze and smoke from forest fires during the first part of the weekend, to the chances of showers and thunderstorms each day from Saturday through the middle of next week. Saturday and Sunday, the high pressure area that had been located over the Rockies and central High Plains retrogrades westward as a large ridge amplifies over the Intermountain region northward into western Canada. That amplified pattern breaks down through the upcoming work week as short wave troughs initially top the ridge on Monday and Tuesday and then end up plowing through the ridge by late in the week. Showers and a few storms are depicted by guidance as following the surface front across mainly the northern part of the forecast area Friday night into early Saturday with additional more numerous storms moving off the Front Range and developing along the frontal boundary as it moves south of the area Saturday late afternoon and evening. A similar setup is expected Sunday and Monday with storms developing mainly over the Rockies and moving eastward over the plains late each day as they dissipate, with storms being more numerous over the southern plains in closer proximity to the remnants of the frontal boundary. For Tuesday through Thursday, it looks like a northwest flow pattern sets up with several short waves moving through the flow that will help contribute to the development of mainly diurnal storms. Model consistency lessens through the week with the timing and locations of individual short waves. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 542 PM MDT Thu Jul 29 2021 KGLD expects to see VFR conditions during the 00Z TAF period. Winds at KGLD start south-southeasterly around 12 kts with occasional gusts up to 20 kts before winds decrease to around 8 kts at 02Z. By 07Z, KGLD winds look to turn southerly then increase to 12 kts at 15Z. At 17Z, the southerly winds at KGLD become 12G20 kts then decrease to around 11 kts by 22Z. KMCK also sees VFR conditions throughout the 00Z TAF period starting with southeasterly winds at 12 kts. At 02Z, winds at KMCK turn easterly around 8 kts then slow to 5 kts by 11Z. At 14Z, KMCK winds become southerly around 9 kts before increasing to 10G15 kts at 20Z. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...LOCKHART LONG TERM...LOCKHART AVIATION...076
Area Forecast Discussion
National Weather Service North Platte NE
619 PM CDT Thu Jul 29 2021 .SHORT TERM...(This evening through Friday night) Issued at 323 PM CDT Thu Jul 29 2021 Satellite shows two fairly potent UA disturbances moving through MT and WY this afternoon. The disturbances are the basis for likely thunderstorm chances Friday afternoon and Friday night. The disturbances will lift north and east through wrn SD tonight and move through ncntl Nebraska Friday and Friday night. The models suggest the first disturbance moving SD tonight would set off scattered thunderstorms across nrn Nebraska late tonight and Friday morning and the second disturbance arrives Friday afternoon or evening producing the best thunderstorm chance. h500mb-300mb winds aloft increase to 25 to 40 kts across ncntl Nebraska and a warm front will lift north Friday providing focus for storm development. Given the strong winds aloft and the excellent upper level support shown by the models, some amount of severe storm development appears likely. The only limiter might be lapse rates; temperatures at h500mb remain fairly warm, -7C or warmer. Storm hazards are primarily wind damage and perhaps isolated tornado development. Given the warm air aloft, large hail would seem to be a lesser concern. The models are in very good agreement opening up a warm sector across ncntl Nebraska Friday afternoon. The strong winds aloft, deep moisture and attendant warm front are the basis for the tornado concern. Precipitable water increases to over 1.5 inches ahead of storm development and this is the basis for WPC`s marginal excessive rainfall outlook. All of this storm activity should be south and east of ncntl Nebraska Saturday morning. Isolated to scattered thunderstorm coverage is in place this evening and overnight for the ongoing thunderstorms across across wrn and ncntl Nebraska. The 12z KLBF UA sounding suggested a high based or elevated thunderstorm chance. Given the very weak winds aloft- 15- 20kts at h500-h300mb, these storms have the potential to produce wind gusts and this is the basis for SPC`s day one marginal severe weather risk. The temperature forecast leans on the short term model blend plus bias correction. The produced lows mostly in the 60s and highs in the 80s north and 90s to near 100 south Friday. A surge of warm air and deeper mixing across srn Nebraska supports the very warm temperature forecast. Dew points are expected to fall somewhat in the afternoon and a check on heat indices suggest upper 90s. No Heat Advisory will be issued for this forecast but it will be close. Later forecasts could include a Heat Advisory along and south of Interstate 80 if dew points can remain in the mid 60s or higher throughout the afternoon. .LONG TERM...(Saturday through Thursday) Issued at 323 PM CDT Thu Jul 29 2021 Western and north central Nebraska will remain post-frontal Saturday and beyond. The robust area of thunderstorms across ncntl Nebraska Friday should send an outflow driven cold front through wrn Nebraska Saturday. Sunday and beyond, a fairly strong upper low will form near Hudson Bay and this will place wrn and ncntl Nebraska in a strong northwest flow aloft as strong subtropical high pressure aloft becomes centered over the cntl and srn Rockies. A reinforcing Canadian cold front will move through Nebraska Sunday. This back door cold front will push through the region and become stationary across ern WY and nern Colorado. The result will be several days of highs in the 80s and thunderstorm chances will be confined to wrn Nebraska where, presumably, storm activity firing across WY or the Black Hills will move south-southeast through wrn Nebraska at times. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 619 PM CDT Thu Jul 29 2021 A couple aviation weather concerns arise over the next 24 hours or so, including reduced visibility from haze/smoke and thunderstorms. The brunt of the smoke will likely stay over the northern terminals (KVTN to KONL) with visby improving overnight but falling again around sunrise. Isolated thunderstorms may affect southern terminals (KOGA to KLBF to KBBW) with tempo gusty erratic winds. Thunderstorm coverage will increase tomorrow morning and afternoon, mainly in the north. Some storms could be severe after 30/21z with large hail and wind gusts 50+ kts. && .FIRE WEATHER... Issued at 323 PM CDT Thu Jul 29 2021 A check on the 18z RAP and HRRR model near surface smoke forecasts suggests the thick plume of trapped near sfc smoke across ern SD this afternoon will drop south into northern Nebraska tonight and possibly remain in place during the day Friday. The models provide a 48 hour forecast and suggest the smoke will partially mix out Friday. The smoke is trapped in an inversion layer below 700mb. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...CDC LONG TERM...CDC AVIATION...Snively FIRE WEATHER...CDC
Area Forecast Discussion
National Weather Service Louisville KY
1113 PM EDT Thu Jul 29 2021 .Mesoscale Update... Issued at 1111 PM EDT Thu Jul 29 2021 Isolated to scattered thunderstorms have filtered into our southern Indiana and Kentucky Bluegrass counties and are approaching the Ohio River. Activity thus far has remained sub-severe, though one storm currently along the Orange/Harrison (IN) county line has shown supercellular characteristics and has been watched closely. Activity over the next hour or so will likely remain isolated to scattered, but we could see some additional storms drift in from the north overnight along the cold front. The overall strength of the convection overnight still has the potential to become severe given some favorable instability and modest shear in place, but at least up to this point weak capping in the low levels has kept things from getting too out of control. Issued at 920 PM EDT Thu Jul 29 2021 Isolated to scattered storms are starting to develop or enter into our southern Indiana counties. Most of this activity has been non- severe, but toward Crawford County, Illinois, there was a supercell that produced a TDS via KVWX. The environment across our southern Indiana counties remains very unstable above a weak inversion (>4000 J/KG MUCAPE), so if/when storms can overcome it and tap into the unstable air, they could quickly become strong or severe. Earlier in the day, models hinted at broken lines of strong to severe storms pushing into our region during the overnight hours. The latest HRRR runs indicate much of this activity may stay isolated to scattered in nature for the majority of the night, and given the latest radar trends, think this could be a viable solution. Severe potential also looks like it could persist a bit longer than originally thought and affect portions of south-central Kentucky through 08z-09z. One concern with more discrete activity overnight would be a lesser threat for severe wind potential and a higher threat for large hail and isolated tornadoes in supercells. Thankfully, deep layer and low level shear weaken as you go toward southern Kentucky, so the highest threats for severe potential continue to be across southern Indiana and northern/central Kentucky. Issued at 658 PM EDT Thu Jul 29 2021 AMDAR soundings within the past hour have indicated a weakening of the cap in the 900-800mb layer with winds now taking on a more northwesterly component. KLVX has also detected a couple of rogue cells that developed, though they have struggled to strengthen given the weak capping still in place. This activity is not anticipated to become strong or severe. Over the next hour or so, we may continue to see an occasional rogue cell go up across southern Indiana and central Kentucky. Activity currently in central Illinois and Indiana along a weak surface boundary will begin drifting into our southern Indiana CWA counties between 00-01z. Additional activity along a cold front just to its north will filter into the region around or after 03z. Strong to severe storms will be possible with that activity as it drifts southward. Issued at 515 PM EDT Thu Jul 29 2021 Recent AMDAR soundings from SDF indicate a fairly impressive cap remains in place (~23C near 800mb). A look at SPC mesoanalysis pages and high-res model guidance of 900-800mb fields indicate a warm `nose` of temperatures stretching from the central Plains into the lower Ohio Valley resulting in the strong cap. Winds currently at these levels are generally out of the west or west-northwest, so temperatures in these levels should not change much in the very near term, which means the cap should stay in place and prohibit storm development. It`s not until we get closer to 00z that we begin to see winds in these levels shift more northwesterly as a trough sinks in from the north. Cooler temperatures aloft associated with the trough will advect in and help to break down and weaken the cap. Convection currently in central Indiana and Illinois will drift close or toward our area over the next several hours, and depending on how organized it is and if there are any outflow boundaries or cold pools associated with convection, it could be enough to overcome a weakened cap. Threat for strong to severe storms will likely occur after 00z and persist into the early morning hours. && .Short Term...(This evening through Friday) Issued at 320 PM EDT Thu Jul 29 2021 ...Strong to Severe Storms Possible this Evening... So far this afternoon temperatures have warmed into the upper 80s and low 90s as of 2 pm EDT. Dew points were just oppressive in the mid/upper 70s. This was producing heat indices around 100 degrees, mostly west and along I-65 where we have the higher dew point values. This heat and moisture has created a very unstable atmosphere which will remain in place as we go into the evening setting the stage for the development of strong to severe storms. The Storm Prediction Center continues to keep the northern third of our CWA (county warning area) in a slight risk for severe thunderstorms. The main threat being gusty damaging winds and torrential heavy rain. Afternoon mesoanalysis shows sfc cold front stretching across northern MO into northern IN over Lake Erie. Radar was showing scattered development just south and along the boundary. South of the front was strong to moderate instability with CAPE values across central KY and southern IN ranging from 2500-3500 J/kg east of I-65 to 3500-4500 J/kg to the west. Model soundings were showing dry air aloft keeping our DCAPE between 800-1000 J/kg keeping the main threat gusty damaging winds in the strongest storms this evening. Current hi-res model guidance is showing a slower solution in the development of scattered to broken convection this evening. Updated timing looks to drop a broken to scattered line of storms southward into our southern Indiana and north-central Kentucky counties between 9 PM- Midnight EDT and pushing southward into southern KY in the early morning hours. As the storms work to along and south of the Parkway, guidance has been consistent in showing the activity to diminish as it reaches the TN/KY border by day break. Tomorrow will feature cooler and less humid weather for the end of the week. Dew points will fall into the low/mid 60s by the afternoon with afternoon temperatures in the low to mid 80s north of the parkways and mid/upper 80s south. .Long Term...(Friday night through Thursday) Issued at 315 PM EDT Thu Jul 29 2021 The long term forecast will see only minor changes. On Saturday, as a shortwave/cold front drops south, trying to amplify the trough over the eastern CONUS, a few showers and thunderstorms will be possible. With most of the available moisture towards the CWA`s southwest, believe the best chances of precipitation will be on the southwestern side of the CWA Saturday night before fading Sunday. Rainfall totals are expected to range from a hundreth of an inch in our southeastern Indiana and northeastern Kentucky counties to around three quarters of an inch near Bowling Green. Some isolated areas could see higher amounts under heavy downpours. Moving into early next week, northwest flow with surface high pressure remains over the CWA. This will suppress moisture to the south and drop dew points into the 50s across the CWA by Tuesday. With this pattern and lack of available moisture, believe mostly dry conditions will prevail through the end of the work week. However, the GFS does try to form an upper closed low over the region on Wednesday. This would increase precipitation chances towards the end of the week, but for now, don`t believe this is likely. Plans should be based on a mostly dry comfortable week with highs in the 80s and low dew points. && .Aviation...(00Z TAF Issuance) Issued at 659 PM EDT Thu Jul 29 2021 A broken line of showers and thunderstorms are may develop tonight ahead of a cold front and push through southern Indiana and central Kentucky. If a storm impacts a terminal site, expect gusty winds and briefly reduced visibilities and ceilings. Drier air will filter in behind the front and winds will turn to the north. VFR conditions are anticipated in the wake of the storms for the remainder of the forecast period. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Mesoscale...DM Short Term...BTN Long Term...KDW Aviation...DM
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
652 PM CDT Thu Jul 29 2021 .UPDATED for 00Z Aviation Discussion... Issued at 627 PM CDT Thu Jul 29 2021 && .SHORT TERM...(This evening through Friday night) Issued at 302 PM CDT Thu Jul 29 2021 The main impact today into tomorrow will be the continued smoke across Minnesota and Wisconsin. Smoke is present across all of the forecast area, but the smoke has not been going to the surface equally across all areas. For much of Wisconsin this smoke has remained aloft, but for much of Minnesota this smoke has made it down to the surface. This has resulted in the MPCA issuing an AQA for most of the state of Minnesota. North winds will continue to move the smoke across Minnesota today. HRRR smoke runs suggest that there will be some clearing of near surface smoke late this evening into tonight across parts of the state. The best chances for this clearing will be in the eastern parts of Minnesota, but the air flow could keep the smoke around for longer farther west. Outside of the smoke high pressure will limit chances for much wet weather today and tomorrow. A system passing off to our southwest could provide some rain showers in parts of southern and southwest Minnesota on Friday, but little QPF is expected. The good news in this forecast is that it does look like we will get a break from the heat and humidity today and tomorrow. .LONG TERM...(Saturday through Thursday) Issued at 302 PM CDT Thu Jul 29 2021 Northwest flow over this period will provide for a few chance for some active weather with shortwaves along the flow, but overall no widespread rain events on the horizon as Minnesota moves farther into drought. None of these shortwaves at the moment look to arrive with the necessary moisture to provide us much chance for rain. The best chances in this period are on Saturday, but these chances are mostly confined to western Wisconsin so they will provide little relief for the drought stricken areas. Smoke will remain a concern as well over the next week as fires continue in Canada and the western US. The main feature to watch for will be how much can make it to the surface. If it remains aloft than impacts will be limited to reddish suns and cooler temperatures. If it makes it the surface than the air quality will be poor like it is today across much of Minnesota. Finally temperatures look to be near to below normal through the weekend, but look to rise back into the near to above normal range by the middle of next week. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 627 PM CDT Thu Jul 29 2021 Areas of smoke will continue this evening. The latest HRRR guidance shows the lowest visbys moving to the southwest and exiting the region overnight. Otherwise expect some high clouds and northeast surface winds becoming more southerly on Friday. KMSP... Look for a few hours of MVFR visby due to the smoke this evening. Then expect VFR conditions to return overnight and last through Friday. /OUTLOOK FOR KMSP/ Fri...VFR. Winds SE 5-10 kts becoming SW. Sat...VFR. Winds NW 10-20 kts. Sun...VFR. Winds N 10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ SHORT TERM...NDC LONG TERM...NDC AVIATION...JRB
...Updated Aviation Forecast Discussion...

.DISCUSSION... Issued at 333 PM CDT Thu Jul 29 2021 Plenty of moving parts in the forecast. Two different airmasses in place. Smoke from northern wildfires. Chance of severe weather. Heat advisory for southwestern CWA. Visibility in parts of South Dakota and especially Minnesota is down to under three miles due to the wildfire smoke working in with the cooler air from Canada. HRRR has been consistently suggesting it will envelop the area this evening and overnight and may reduce visibility as low as 2 miles in parts of northeastern Nebraska. Heat indices this afternoon have been pushing well over 105 for much of the area and have meandered into excessive heat warning territory at times. Dewpoints have sneaked over 80F in parts of western Iowa. The front has been... well... stationary through much of the day but will sag south this evening and may produce some thunderstorms just north of the Kansas state line after 5pm. With the heat and humidity as high as it is, would be hard pressed to believe large hail would be any real threat, but PWAT values are in the 90th percentile for parts of the CWA and wet downbursts seem reasonable. The threat for severe weather is greater on Friday when an MCV over Wyoming will ride the ridge and help produce plentiful shear and quite the hodographs as revealed in guidance. Expecting storms to work northwest to southeast in the evening and overnight just north of the front. Hail and damaging winds are possible. Have foisted a heat advisory across Otoe, Saline, Seward, Lancaster, Gage, Jefferson, Gage, Pawnee, Johnson, Nemaha, and Richardson counties for Friday afternoon where heat indices will be improved versus today, but still peak near or just above 105F. Parts of northern Kansas will be warmer and an EXCESSIVE HEAT WARNING borders our southern counties. At the same time, some locations along our northern edge may fall shy of 80F for a temp. QPF for Friday night and Saturday morning will run between 1-3" for some areas and flash flooding due to training could be an issue... at least in localized areas. The drought conditions will help prevent widespread flooding concerns. The heaviest rain may fall along a line from O`Neil, NE to Omaha, NE to Lamoni, IA. Dry conditions and sub-seasonal high temps settle in for the remainder of the weekend after the showers and storms wrap up mid- day Saturday. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 611 PM CDT Thu Jul 29 2021 Convection had developed in southeast Nebraska, but is expected to remain well south of TAF sites. More convection is possible around 12Z as low level jet rides over frontal boundary, so have included at least a mention at all TAF sites. Low confidence and expected limited coverage precludes a stronger mention in TAFs. Otherwise areas of smoke spilling into northeast Nebraska could cause visibility restrictions at KOFK as per sites upstream Thursday afternoon. Fog is also possible at KLNK and KOMA as low level moisture lingers through mid morning. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...Heat Advisory until 9 PM CDT this evening for NEZ050>053-065>068- 078-088>093. Heat Advisory from noon to 9 PM CDT Friday for NEZ065-066-068- 078-088>093. IA...Heat Advisory until 9 PM CDT this evening for IAZ069-079-080-090- 091. && $$ DISCUSSION...Nicolaisen AVIATION...Dergan
Area Forecast Discussion
National Weather Service Phoenix AZ
532 PM MST Thu Jul 29 2021 .UPDATE... Updated 00Z aviation discussion. && .SYNOPSIS... Storm chances will increase from east to west across Arizona today with chances expanding into southeast California on Friday and persisting through Saturday. Main storm threats will be strong winds, blowing dust, and locally heavy rainfall. After near normal temperatures today, readings will dip to below normal through the upcoming weekend. Drying conditions starting Sunday will push storm chances back to only the eastern Arizona high terrain, with much of the area staying dry during the first half of next week. && .DISCUSSION... Monsoon activity will quickly increase today with multiple weather disturbances poised to affect the region. Current radar loops is already showing convective activity breaking out along the Rim/White Mountains with additional scattered storms now occurring across the lower deserts and over some the Gila County Burn Scars. The main driving force behind thus increase in monsoon storm activity is an westward advancing upper level trough currently moving across northern Mexico. This upper level trough is quite expansive in size and is analyzed as a closed low at 300mb and mostly as an open trough at 500mb. As it continues to track west northwest today into Friday it is forecast to weaken, but much if not all of Arizona is seen coming under broad difluent flow aloft as early as this afternoon. latest HRRR high-res model runs are showing storms spreading across SW AZ over the next few hours along with more activity moving into southern Gila County. As far as the greater PHX area, this morning`s clouds/virga seems to be limiting activity across that region at this hour, but latest SPC HREF model output does indicate storms attempting to move into that region from the east this evening. Storms will be capable of strong gusty winds with multiple outflows expected to form and locally heavy rainfall. With PWATs ranging from 1.3-1.6" and a modest 10 kt east southeasterly steering flow, this should keep storms fairly progressive likely minimizing the potential flood threat over the lower deserts. The biggest threats this afternoon and evening should be strong winds and localized blowing dust with the 12Z HREF highlighting a large area of 70-90% probability of greater than 35 mph winds across the majority of Arizona. Although the HREF shows a greater chance for this to happen across southern Maricopa and Pinal Counties, it could happen anywhere this evening as several outflows are expected. One large westward advancing outflow is likely to reach the Colorado River by late evening with additional showers and weak storms likely across southwest Arizona into southeast California during the early overnight hours tonight. Friday still looks to be another active monsoon storm day, but with less activity across eastern Arizona as some drier air works in from New Mexico. The weakening upper level trough slowly lifting northwestward through the Desert Southwest should still provide some upper level support, while a trough off the West Coast also provides additional ascent across southern California. Moisture levels Friday will improve over today in most locations with PWATs upwards of 2" across the western deserts, to 1.5-1.75" across much of south-central Arizona, but lowering closer to 1.25" in eastern Arizona. MUCAPEs Friday should also be higher likely ranging from 1000-1500 J/kg from Phoenix westward through southeast California. The storm threats Friday and Friday night is expected to transition more toward heavy rainfall and localized flooding, but southeasterly steering flow of 10-15 kts should keep storms from remaining stationary over one area for very long. Strong winds will continue to be a threat, but mostly in the form of storm downdrafts instead of outflows. Bulk shear also increases by Friday afternoon/evening across southwest Arizona and parts of southeast California, so a few longer lasting severe storms may be possible, along with a greater threat for flash flooding across that area, thus a Flash Flood Watch has been issued for that region. For Saturday, the inverted trough will become a non-factor as it lifts north, but the lingering trough off the West is forecast to send up another upper jet max out of the south. This jet should again provide broad ascent over much of the area on Saturday, but we begin losing moisture especially across the western deserts. Storm chances for Saturday are still quite uncertain, but NBM PoPs are mostly in a 30-40% range. The drier air working in from the southwest should overtake much of Arizona on Sunday likely limiting storm chances Sunday to the high terrain north and east of Phoenix. The first half of next week also looks to be quite dry and may only involve a few daily afternoon showers and storms across far eastern Arizona. Boundary layer moisture should also gradually lower with each day early next week as the subtropical high reforms initially just to our southwest before slowly drifting over southern California into Arizona by Tuesday or Wednesday. Although NBM high temperatures increase back to around normal readings early next week, would not be surprised if we will have to worry about some areas near excessive heat. If we do dry out the boundary layer next week and a 594dm 500mb ridge is overhead, excessive heat will be a possibility. && .AVIATION...Updated at 0030Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Convective impacts due to strong outflow winds and the potential for isolated to scattered showers and thunderstorms to develop along them over the next few hours will be the main impacts for the Phoenix terminals. A strong northeast outflow with 20-30 knot winds is currently moving through KSDL and should clear KDVT by 0030Z and PHX between 0045-0100Z. A slightly weaker, more easterly outflow is expected through KIWA, with a southerly outflow currently moving through the West Valley in this time frame as well. Given the uncapped environment and thus unstable airmass, we have at least 50% confidence that storms will develop along colliding outflows, with 30% confidence in TSRA at all TAF sites except KIWA where colliding outflows are a bit less likely. Thus, we have VCTS generally between 01-03Z for most of the TAF sites except KIWA where VCSH is in place. Confidence in thunderstorm development is highest in the West Valley due to the greatest potential for colliding outflows. Brief gusts in excess of 35 knots and blowing dust with MVFR visibilities will be possible with the northeast outflow, with isolated 40-50 knots possible with the strongest individual storm cells. SCT-BKN cloud bases down to 7-8 kft will be possible with these storms. Assuming storms develop early this evening, the overnight hours should be relatively inactive. Winds should retain easterly headings through early afternoon before veering to the west at 5-10 knots. Another round of isolated to scattered convection is possible late tomorrow afternoon into the early evening hours, though confidence only warrants VCSH at this time. Southeast California/Southwest Arizona including KIPL and KBLH: Convective impacts over the next few hours will be the main aviation impacts tonight. Shower and thunderstorm chances at KIPL and KBLH are around 20% through 02-03Z, with slightly better chances of VCTS at KBLH given ongoing convective activity. Wind gusts in excess of 40 knots will be possible with the strongest storm cells, though most should produce gusts closer to 25-35 knots. Another round of showers and thunderstorms is possible along E-NE outflows later tonight in southwest Arizona into the Colorado River Valley including KBLH, where another round of VCSH is included from 06-10Z. However, confidence is too low to include convection at KBLH at this time. Patchy blowing dust briefly reducing visibilities will be possible with any storms. Otherwise, winds will generally be southerly to westerly at KIPL and S-SE at KBLH. Winds will generally be around 10-15 knots with gusts to 20-25 knots possible overnight with showers at KBLH. Cloud bases should generally remain at or above 8-10 kft. && .FIRE WEATHER... Sunday through Thursday: Unsettled conditions are likely through Sunday with the last of the weather disturbances moving through the region. This should bring fairly widespread shower and storm chances on Saturday before more limited storms on Sunday. Shower and storm chances for Mon-Thu will be limited to a few storms during the daytime hours over the eastern Arizona high terrain. Main threats on Sunday will be strong thunderstorm winds, heavy rainfall and possible localized flooding. Temperatures will range from near to slightly below normals the bulk of the period. Minimum afternoon humidity values will range from 25-45% through the weekend before falling back to 15-30% early next week. Overnight recovery will be mostly good to excellent in a 40-80% range. Apart from thunderstorms, winds will favor typical daily upslope/drainage patterns. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Flash Flood Watch from Friday afternoon through late Friday night for AZZ530>533-535-536-538-539-559. CA...Flash Flood Watch from Friday afternoon through late Friday night for CAZ569-570. && $$ DISCUSSION...Kuhlman AVIATION...Hopper FIRE WEATHER...Percha/Kuhlman
Area Forecast Discussion...CORRECTED
National Weather Service Pueblo CO
345 PM MDT Thu Jul 29 2021 .SHORT TERM...(This evening through Friday) Issued at 340 PM MDT Thu Jul 29 2021 Hot and mostly dry conditions continue with thunderstorm activity focused across the valleys and Continental Divide this afternoon. Highest precipitable waters continue to reside to the west with best chance for locally heavy rain across the Continental Divide through this evening. Activity will wind down tonight with loss of heating. Friday looks fairly similar to today, with perhaps a slight increase in precipitable waters out west. Thunderstorms will develop over the mountains around noon with northeasterly steering currents keeping activity mainly over the mountains and valleys. Best thunderstorm chances will be across the Continental Divide where potential for locally heavy rainfall on the Chalk Cliffs will have to be monitored for a localized flash flood potential. Overall confidence is too low to issue a flash flood watch just yet. Will let later shifts assess CAMS models as event nears and hoist any necessary watches. Otherwise another hot day on tap for the plains with temperatures around 100 degrees for the lower Arkansas River valley. -KT .LONG TERM...(Friday night through Thursday) Issued at 340 PM MDT Thu Jul 29 2021 ...Flash Flooding may be an issue for Saturday and Sunday for the burn scar areas, and a slight chance that the urban areas could be impacted as well... For Friday...there will be a chance of afternoon and early evening thunderstorms over the central mountains. A few storms will be possible over the eastern mountains and a very slight chance over the I-25 corridor as well, but much more isolated in nature. For Saturday through Sunday...scattered to numerous thunderstorms will develop over much of the mountainous terrain, and showers or thunderstorms could develop during the early hours of the morning on Saturday over the plains and possibly later in the afternoon, with the I-25 corridor receiving the best chance. There could be localized flooding over the burn scar areas, and possibly over the urbanized areas during the later in the day on Saturday. On Sunday most of the shower and thunderstorm development will be confined to the mountains and southern areas of the CWA, especially during the afternoon and evening hours. For Monday through Tuesday...Scattered showers and thunderstorms will develop across much of the region during the afternoon and evening hours, some storms could become severe. Flash flooding will be possible over the burn scar and urbanized areas. Storms will be more likely over the plains on Tuesday. Detailed discussion: Friday... The ridge is continuing slightly retrograde back to the west with the axis becoming more negatively tilted by Friday. The center of the surface high positioned over northeastern Colorado. This feature, coupled with an upper level low over northern Mexico that is also propagating towards the west and is allowing drier air on the subsident side will keep most areas of our CWA warm and dry throughout Friday evening, as the brunt of the monsoonal moisture plume remains further to the west. There will be the enough moisture to allow for orographically induced convection over the central mountains and there could be enough residual moisture as well to cause a few storms to develop over the eastern mountains and over the I-25 corridor as well, however, these will be much more isolated in nature. With a strong ridge overhead and southerly flow over most areas, temperatures will be very hot, with triple digit heat likely over the lower Arkansas River Valley. Saturday and Sunday... As the negatively tilted ridge axis becomes more elongated over the northwestern CONUS, a longwave trough downstream over the northern plains is going to deepen and allow for some of the monsoonal moisture plume to be advected in from the northwest. This, along with an associated cold frontal boundary extending over the central plains with a developing surface low over the Great Lakes region, will help to produce forcing and help to induce convection over our area by the early morning and throughout the afternoon and evening on Saturday. The models are differing quite significantly now with the timing of the front, as well as the amount of moisture available over the plains. The HRRR and NAM have been much drier and quicker with frontal passage and not much in the way of precip over the central and eastern plains as the GFS and SREF. The timing could be crucial as to which areas will experience the most rainfall and if there is enough cooler air moving in behind the front, it could help to stabilize the lower levels too much and minimize the threat for much in the way of thunderstorms over the plains. Right now, the general consensus of frontal passage will now be much earlier than shown in previous model runs for the past few days, and have FROPA occuring for the northern areas of the CWA around 09Z to 12Z with a weak lee side meso-low developing over the central plains. Then the front will pass over the southern portion of the CWA by around 12Z to 15Z. The thunderstorms over the mountains could contain localized flash flooding in and around burn scars and some of the heavier showers and thunderstorms could cause flash flooding for urbanized areas, especially over the I-25 corridor. There doesn`t appear to be enough mid level shear showing up in the models, therefore the severe thunderstorms. For Sunday, the cooler air could cause most precip to more stratiform in nature as the lower levels remain too capped and stable for many locations. Winds will be primarily from the southwest ahead of the front and switch to the northeast. Along with the increase chance of measurable precip over most of the CWA, the frontal passage will also create a cooldown, with temperatures falling into the evening hours and max temperatures will be closer to around the seasonal average for most locations. -PS Monday through Wednesday... The monsoonal moisture plume will shift back towards the east as the axis over the Four Corners repositions itself over Colorado as the surface plateau high strengthens. This will allow for more showers and thunderstorms to develop over most areas, with the best chance being in the afternoon and evening hours over the mountains, and as the axis slowly shifts more to the east on Tuesday, this will give the plains a better chance of seeing convection further east towards the Kansas border. As the ridge also continues to slightly build back with a strengthening surface high pressure, expect max temperatures to gradually warm going into the middle part of next week with the best chance of thunderstorms over the plains by Wednesday. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 340 PM MDT Thu Jul 29 2021 KALS: VFR conditions are expected over the next 24 hours. Isolated rain showers and thunderstorms are possible tomorrow afternoon, but confidence is low in development. If a thunderstorm were to develop, the main impacts would be brief heavy downpours and erratic outflow winds. Otherwise at KALS, expect light and variable winds overnight, before increasing in magnitude tomorrow. KCOS and KPUB: VFR conditions are expected over the next 24 hours. Winds will become light and variable overnight and into tomorrow morning, before increasing early tomorrow afternoon. Skies will remain mostly clear through tonight and into tomorrow afternoon as well. && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...KT LONG TERM...STEWARD AVIATION...SIMCOE