Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/18/21

Area Forecast Discussion
National Weather Service Boise ID
848 PM MDT Sat Jul 17 2021 .DISCUSSION... Smoky and hot conditions continue. Earlier this afternoon, isolated thunderstorms moved over southern Twin Falls County but have since dissipated. A Heat Advisory is still in place for Sunday for the Snake Plain and Boise Mountains. Monsoonal moisture will move northward into the area by late Sunday night/Monday morning, bringing increased cloud cover a slight chance of precip. && .AVIATION...Generally low VFR. Areas of MVFR due to wildfire smoke. Significant visibility restrictions aloft due to smoke layers. Surface winds: SW-NW 5-15kt through 04Z, becoming variable 10kt or less after 04Z. Winds aloft at 10kft MSL: southwest 10-20 kt. Density altitudes will remain high due to hot temperatures. && .PREV DISCUSSION... SHORT TERM...Tonight through Monday night...Hotter Sunday as the upper ridge continues to amplify to our east. A Heat Advisory remains in effect for Sunday afternoon and evening in the Treasure Valley, Western Magic Valley, and Upper Weiser River Valley. Mid- level monsoon moisture will develop isolated thunderstorms near the NV/ID border Sunday afternoon and evening, but especially Monday and Monday evening. Cloud cover will keep temperatures warm Sunday night and Monday night, but will also lower daytime temperatures on the Idaho side on Monday. HRRR smoke model continues to put smoke over eastern Oregon from the Bootleg Fire in southern Oregon and two large fires in northeast California. Relatively less smoke is forecast over southern Idaho with few if any fires in northeast Nevada. LONG TERM...Tuesday through Saturday...Above normal temperatures and smoky conditions will continue through the long term under southwest flow aloft and a strong upper level ridge over WY and CO. Weak disturbances in the periphery of the upper ridge will generate thunderstorms on Tuesday and Wednesday. Monsoon moisture will continue to stream northward from the south through the week, keeping a threat of thunderstorms over the Idaho zones. Southeast Oregon will remain dry, as the monsoon moisture stays to the east. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Heat Advisory from noon to 9 PM MDT Sunday IDZ012>014-016-033. Fire Weather Watch from Monday afternoon through Monday evening IDZ423-426. Red Flag Warning until 11 PM MDT Sunday IDZ401>403-421. OR...Heat Advisory from noon MDT /11 AM PDT/ to 9 PM MDT /8 PM PDT/ Sunday ORZ064. && $$ DISCUSSION...SH AVIATION.....SP PREV SHORT TERM...LC PREV LONG TERM....KA
Area Forecast Discussion
National Weather Service Denver/Boulder CO
837 PM MDT Sat Jul 17 2021 .UPDATE... Issued at 833 PM MDT Sat Jul 17 2021 Ongoing scattered showers and thunderstorms across the northeast plains of Colorado. Still some marginally severe storms now across eastern Morgan county and moving into portions of southern Logan and Western Washington counties. Main impacts will continue to be heavy rain, hail and strong wind gusts. Expect the majority of the thunderstorms to diminish after midnight but the HRRR keeps a few storms moving across the far northeast plains well after midnight. Will keep in some low pops to account for this. Further west over the Front Range and mountains convection has ended for the night. && .SHORT TERM...(This evening through Sunday) Issued at 205 PM MDT Sat Jul 17 2021 As expected, we`re getting fairly widespread but weak convection over the mountains where there is mid level moisture but also a little warm layer that`s limiting CAPE. The plains remain weakly capped but should get warm enough for isolated storms to pop late this afternoon, most likely near the northern border. CAPEs should range from 600-1200 J/kg and with limited shear, only the strongest storms should approach severe limits. We still expect a few storms to form under the lift from a jet streak that passes north of us overnight. These will likely form in southeast Wyoming or the Nebraska panhandle and move southeast, possibly coming across the northeast corner of Colorado. Uncertainty remains about just where this will be, and whether there will be enough energy for any severe threat since they will be moving into progressively cooler but moister air overnight. This activity could run out of steam, but the HRRR trend has been to maintain them most of the night. We`ve added some low PoPs east of Sterling and Akron into the early morning hours in case the storms survive and are that far west, but the better odds are earlier and further northeast. For Sunday, the biggest change is that the mid level winds are lighter and are going north and northeasterly, bringing drier air above a shallow moist layer over the plains. As a result, the moisture mixes out over the western part of the plains. Over the mountains there`s a bit less storm activity, but it will also likely be slow moving so the resulting areal coverage should be less. Still a little potential for localized heavy rain but there`s less of everything to work with so the flood threat will be getting small. We`re showing similar high temperatures, but it could be slightly warmer due to later and less cloud cover. .LONG TERM...(Sunday night through Saturday) Issued at 205 PM MDT Sat Jul 17 2021 It is all upper ridging for the CWA Sunday night through Tuesday night. Models show the upper ridge center around the northwest corner of Colorado Sunday night and Monday. Then it is over central Colorado most of Tuesday. Tuesday night, the center is over the Four Corners. The ridge axis is oriented north-south Sunday night into Monday. Then is stretches more southwest to northeast Tuesday and Tuesday night. The flow aloft is weak north and north-northwesterly all five periods. The low level winds should be normal diurnal trends; drainage at night and some easterly component during the afternoons. Concerning moisture, precipitable water progs show values in the 0.5- 0.8 inch west to 0.90-1.30 east through the 5 periods. Will keep some minor pops in the mountains late day Monday, with better chances there Tuesday afternoon and evening. The lapse rates show a decent cap over the eastern half of the CWA during the afternoons and evenings through Tuesday night; so no pops. Temperatures look to be a bit above seasonal normals through the period. Looking ahead at the later days, Wednesday through Saturday, models keep the upper ridge centered over Colorado. It does flatten somewhat Friday and Saturday. The flow aloft is very weak, and out of the east or northeast Thursday night in Saturday morning. Will keep the "scattered" pops going in the mountains and foothills for the late day periods. Less pops over the western plains and almost nothing for the eastern plains. Temperatures remain a tad above seasonal normals. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 833 PM MDT Sat Jul 17 2021 Convection has ended for the night at local terminals as winds have shifted back to a southerly component. Looks drier on Sunday with less threat of convection and will not include any mention of TS. Most of the activity will be west and south of the terminals so could see some outflow winds. && .HYDROLOGY... Issued at 205 PM MDT Sat Jul 17 2021 Slow moving thunderstorms are expected over the mountains this afternoon and again Sunday afternoon, but limited moisture and storm strength will keep the threat of burn scar flash flooding low. Overnight storms over the northeast corner of Colorado could produce localized heavy rain of 1 to 2 inches in 1 to 2 hours with a low threat of minor flooding. Less moisture in the early part of the week will further reduce the threat of burn scar flooding. Moisture will eventually increase again in the middle or later part of the week. Fairly decent moisture will keep "scattered" pops going in the mountains into next weekend. The flow aloft will be weak so heavy rainfall may cause flooding, especially in the burn areas. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Entrekin SHORT TERM...Gimmestad LONG TERM....RJK AVIATION...Entrekin HYDROLOGY....Gimmestad/RJK
Area Forecast Discussion
National Weather Service Cheyenne WY
451 PM MDT Sat Jul 17 2021 .SHORT TERM...(This evening through Monday Night) Issued at 212 PM MDT Sat Jul 17 2021 The main concern with this forecast is the chances of severe weather tonight. Latest radar loop was showing a cluster of showers and thunderstorms continuing to develop over the Snowy Range. This is bringing some beneficial rainfall (.10-.15) during the last couple of hours. The good thing is that there is not much lightning and precipitation rates have been fairly low especially over the burn scar. Would expect these showers and storms to continue to build east as the mid level shortwave continues to translate east this evening. The main question is if these storms will be able to become severe as the shortwave approaches the Nebraska panhandle. Currently, instability is fairly low with cape values generally ranging from 1000-1500j/kg along and just east of the Laramie Range in Wyoming. This area may see some gusty winds under this shower and thunderstorm activity. However, as you approach the far eastern Nebraska panhandle CAPES are around 2500-3000j/kg. Pressure falls are very subtle which is limiting the southeast flow, but we still may see a couple of strong to severe storms in the eastern Nebraska panhandle. Not too impressed with the effective shear (30-35kts) with the bulk of the shear in the 5-7km layer which may be enough to produce some rotation in the mid levels and yield to some larger hail up to golf ball size. The HRRR reflectivity show these storms moving out of the area by around 03z-05z. Another concern is the slow movement of these storms especially when the low level flow begins to increase in response to the pressure falls this evening and causes these storms to deviate more to the southeast. The upper level ridge will continue to build over the area during the next couple of days which will bring light winds and more capping to the region. As a result, the convection chances will become more isolated in nature along with warmer temperatures. .LONG TERM...(Tuesday - Friday) Issued at 247 AM MDT Sat Jul 17 2021 Very hot & dry conditions persist through much of next week w/ the bulk of mid-level energy remaining to the north of the CWA. 700 mb temperatures are progged to climb to near +18 deg C across a large portion of the area, so highs in the 90s to 100+ F should be quite common. Heat Index values are currently projected to fall short of the 105+ deg F threshold, but it is entirely possible that we will need to consider Heat Advisories for some zones with daytime highs near/exceeding 100 with lows failing to fall below 70 F. Certainly an unusually hot pattern for our area. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 441 PM MDT Sat Jul 17 2021 VFR to MVFR conditions likely for all terminals through the forecast period. Main concerns exist today with thunderstorm potentials through the late evening to nighttime hours. Current radar imagery has cells developing along the I-25 corridor and traveling eastward. Main threats include strong and erratic winds near any thunderstorm activity and large hail possible. Moving into tomorrow, the severe threat is expected to shift further eastward just outside of the CWA. There will be a chance for some low level fog along the eastward fringes of the Panhandle with plenty of moisture from the overnight storms, variable light winds, and clear overnight skies. Confidence is low at this time for fog development with most HighRes models indicating most of the better conditions remain out east. As a result, went ahead and started slightly dropping visibilities for the terminals in the Panhandle. && .FIRE WEATHER... Issued at 212 PM MDT Sat Jul 17 2021 Hot and dry conditions can be expected through Tuesday. Cannot rule out some isolated showers/tstms which may result in some dry lightning, but wind speeds will remain fairly light except for some low level wind enhancement over Pine Ridge at night. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...REC LONG TERM...CLH AVIATION...MD FIRE WEATHER...REC
Area Forecast Discussion
National Weather Service Dodge City KS
703 PM CDT Sat Jul 17 2021 ...updated aviation... .SHORT TERM...(This evening through Sunday) Issued at 313 PM CDT Sat Jul 17 2021 An upper level area of high pressure sits above the Central Rockies with small pieces of energy sliding around its periphery and into the Central Plains. Towards the surface, a weak frontal boundary will slide south and position itself along the KS/OK border this afternoon and remain there through tomorrow. A few storms may form along this boundary this evening, otherwise expect partly cloudy skies across western Kansas. Precipitation chances slide into central Kansas by tomorrow with continued partly cloudy skies. As for temperatures, lows tonight look to range form the mid 60s west to around 70 degrees east. Highs tomorrow are once again expect to reach to around 90 degrees. .LONG TERM...(Sunday night through Saturday) Issued at 313 PM CDT Sat Jul 17 2021 Precipitation chances continue across central Kansas through Monday, otherwise expect partly to mostly cloudy skies. Drier conditions then are expected throughout the remainder of the long term forecast as the upper level high shifts eastward and above the Plains with high pressure being the dominate feature at the surface. As for temperatures, highs will generally be in the 80s to around 90 degrees through Wednesday then 90s for the remainder of the long term forecast. Lows will generally be in the 60s with a few 70s across central Kansas as we head into the late part of the week. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 701 PM CDT Sat Jul 17 2021 Surface stationary boundary was stretched from just north of EHA to near DDC and eastward, with light southeasterly winds south of the front and light southwesterly winds to the north. A scattered cu field around 5-8kft, and most of this should dissipate with the loss of insolation, supported by a widening of T-Td on HRRR forecast soundings. Some of the CAMS support increased chances for convection toward 10-13 Z timeframe in north central Kansas, most likely near the HYS terminal as scattered storms moved southeast from the front range of WY/CO overnight. There could be thunderstorms in the vicinity - or any activity is just as likely to be well to the east out of the vicinity. && .PRELIMINARY POINT TEMPS/POPS... DDC 68 91 67 89 / 20 40 40 20 GCK 66 91 65 89 / 20 30 30 20 EHA 65 92 65 90 / 30 40 40 10 LBL 66 91 66 89 / 20 40 40 20 HYS 67 89 65 87 / 30 50 50 20 P28 70 90 69 88 / 20 50 60 40 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Hovorka_42 LONG TERM...Hovorka_42 AVIATION...Russell
Area Forecast Discussion
National Weather Service Grand Forks ND
1001 PM CDT Sat Jul 17 2021 .UPDATE... Issued at 949 PM CDT Sat Jul 17 2021 Attention continues to be on the convection in SW Manitoba which has been decreasing rather rapidly in the past hour based on lightning activity and radar reflectivity. Otherwise temps this late summer evening ranging from 65 to 75. UPDATE Issued at 624 PM CDT Sat Jul 17 2021 Dry evening and overnight expected as any convection so far remains north of the international border in SW Manitoba. Little instability or shear exists to support storms to move southeast towards the FA. Will need additional development and then potential llj to feed storms overnight which would then move south into the instability. HRRR continues to hint at this possibly overnight with scattered showers or storms in the Devils Lake basin overnight. && .SHORT TERM...(This evening through Sunday night) Issued at 254 PM CDT Sat Jul 17 2021 Smoke and any stray showers or thunderstorms moving into our counties will be the primary challenges for the period. The upper ridge over the Rockies and western Plains will continue to build through the weekend, but several weak embedded shortwaves will continue to be possible. These ridge riders will continue to bring a few stray showers and thunderstorms to the Northern Plains, similar to the previous few nights. The question is where and when the convective activity will occur. Some convection has already developed over northwestern ND up into Canada, moving very slowly east. Instability is focused mainly over western and central ND, with very little over our counties. Deep layer bulk shear is minimal. Will continue to keep some very low POPs over our far western border tonight in case any activity from central ND or southwestern Manitoba strays into our CWA, but any rain will be isolated. Most of the smoke this afternoon has stayed at the higher levels, with improved air quality so let the AQA expire. Will continue to monitor for any additional mention of smoke or haze needed. The upper ridge will continue to amplify into tomorrow, so think that temps will be another degree or so warmer, even with the possibility of smoke reducing warming just a bit. Continued to keep highs in the upper 80s to low 90s. Another weak ridge rider will begin to move down into the area Sunday night. Current CAMs and global models bring most of the activity into our northern CWA from Canada, but with weak flow under the ridge uncertainty is high. Better instability for Sunday evening although deep layer bulk shear is still weak so could again see a few slow moving isolated cells. .LONG TERM...(Monday through Saturday) Issued at 254 PM CDT Sat Jul 17 2021 Ridging remains anchored over the Four Corners region through the Monday to Friday period, with warmer than average temperatures expected to continue. H5 heights will approach 595 Dm to 600 Dm over the southwestern CONUS during this time frame, with the ridge slowly flattening over the course of the week. This will allow shortwaves to begin pushing across the northern reaches of the CWA along the International Border. The chance for weather related impacts will be low; however, uncertainty surrounds the potential strength of any thunderstorm activity that develops. High temperatures will climb into the lower to middle 90s each day, with the caveat that the upper extent of the temperature potential will be limited by wildfire smoke that remains in the column. In the event that smoke is less prevalent, we could see higher temperatures given the favorable pattern. Although there are precipitation chances next week, much of the guidance keeps the activity scattered and mainly limited to northwestern Minnesota and the northern Red River Valley. Convective activity could bring brief heavy showers across the small footprint where development occurs. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 624 PM CDT Sat Jul 17 2021 SE winds overnight and again tomorrow will generally be 10kts or less with a few afternoon gusts to 20kts in the valley. VFR conditions with elevated smoke persisting. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ UPDATE...JK SHORT TERM...JR LONG TERM...Lynch AVIATION...JK
Area Forecast Discussion
National Weather Service Goodland KS
934 PM MDT Sat Jul 17 2021 .SHORT TERM...(This evening through Sunday) Issued at 234 PM MDT Sat Jul 17 2021 Latest upper air analysis shows the ridge over the Great Basin. Rotating around the ridge are small short wave troughs. Smoke from the wildfires in CA and OR is rotating around the ridge and will likely be moving over the forecast area by Sunday. At the surface a subtle boundary was in place north of Limon to Akron. Cumulus clouds have started forming along this boundary. Tonight models have delayed the start time of the storm activity from what the prior shift saw. However, models have also weakened the strengthen of the short wave trough as it moves over the west part of the forecast area. Due to the subtle weather features that could have a large impact on the forecast, confidence is moderate with the current forecast. Aside from whether storms will form, the main question is how far south will storms last once they move into the forecast area. Given this consideration, have lowered rainfall chances through the rest of the evening as the storm activity moves southward. Hazards tonight will be hail up to 1" and wind gusts to 60 MPH. The hail threat will be short lived due to the deep layer shear declining as storms move south into the forecast area. Storm motion will be very slow, so heavy rainfall, and possibly flash flooding, may occur. Overnight an upper level short wave trough may move through the eastern part of the forecast area. Elevated instability looks favorable for storm development. Despite elevated CAPE over 1000j/kg, the weak winds appear too weak to support large hail. There is also the question of when these storms move through, or if they will remain east of the forecast area like last night. Don`t have enough confidence to change the timing of the storm activity tonight from the prior forecast. Have noticed in the past that models tend to hold onto overnight storm activity too long, so this may be happening again. Looking at the RAP MCS maintenance probabilities, the probabilities are increasing for the western part of the forecast area, and are trending more into the morning hours over the eastern part of the forecast area. This does raise confidence that storms will occur over the west, and raises the question of whether storms will occur over the eastern part of the forecast area later than forecast. Sunday morning there could be some lingering storm activity over the east as the upper level short wave trough continues southeastward. Am thinking this is the best chance for rainfall for the day. Sunday night model data is rather messy regarding when and where the next upper level short wave trough will move through. Could be over the east during the evening, or the west during the overnight hours. Due to the lack of consistency, decided to leave the forecast as is. On a sidenote model consensus has the higher rainfall chances over the eastern part of the forecast area. Temperatures for this part of the forecast will change little. Winds will be fairly light from the south or southeast direction. .LONG TERM...(Monday through Saturday) Issued at 115 PM MDT Sat Jul 17 2021 The extended period begins with a highly amplified ridge over the western CONUS and a long wave trough over the Great Lakes and extended into the Mid-Atlantic region. For Monday, some showers and possibly a storm may be ongoing from previous day convection mainly over Graham county, however confidence is low at this time. Additional storms may develop during the afternoon hours with a weak disturbance; however this will all depend on how far the ridge ends up propagating east during the day. If a storm would be able to develop gusty to strong winds and heavy rain would be the primary hazards with DCAPE around 1400 J/kg and PWATS near 1.5 inches. However, my confidence in that scenario at this time is quite low and have refrained from including in this forecast package due to the low certainty. The high temperatures for the day look to be in the upper 80s to low 90s with overnight lows in the 60s. The rest of the forecast period looks to be dry with a warming trend as the ridge moves to the east and situates itself directly over the plains. The relative coolest day of the period is forecasted to be Tuesday as a weak cold front moves through the area dropping afternoon highs in the mid 80s to low 90s. Wednesday highs rise into the mid 90s before triple digit temperatures make a return to the majority of the area on Friday and Saturday. RH values for Thursday and Friday may need to be watched as well for elevated fire weather conditions across our Colorado counties as winds may be gusty during the afternoon. Forecasted RH values are in the low 20s currently, but with the ridge and numerous other runs of guidance indicating potentially hot temperatures, the RH values may drop in future forecast packages. && .AVIATION...(For the 06Z TAFS through 06Z Sunday night) Issued at 926 PM MDT Sat Jul 17 2021 KGLD expects to see VFR conditions throughout the 06Z TAF period. Winds at KGLD start southeasterly around 7 kts before becoming southerly around 7 kts at 12Z. By 17Z, KGLD winds return to south- southeasterly around 10 kts. KMCK starts the 06Z TAF period with VFR conditions and southeasterly winds around 7 kts. At 13Z, KMCK winds increase to around 11 kts before turning southerly at 19Z. By 23Z, winds at KMCK expect to become east-southeasterly at 8 kts. KMCK sees a slight chance for thunderstorms near the terminal around 00Z through the end of the period, but will not include in TAF due to low confidence at this time. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...JTL LONG TERM...TT AVIATION...076
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
927 PM CDT Sat Jul 17 2021 .UPDATE... 927 PM CDT No changes to going forecast this evening. Only minor tweaks to hourly gridded fields based on satellite/radar and surface obs trends. Baggy mid-level trough continues to drift slowly southeast across the region this evening. Weak low level circulation noted earlier in satellite imagery across northern Indiana appears to be becoming more diffuse with time, with RAP mesoanalysis initialization wind fields in the 925-850 mb layer becoming somewhat more easterly. Isolated nearly stationary showers/thunderstorms which had been occurring east of our area across northern IN have recently waned with the diurnal loss of low level instability. GOES-16 nighttime microphysics RGB does depict low level cloud cover spreading west across northwest IN/southern Lake Michigan into northeast IL, and this will likely continue into tonight, within the moist easterly flow above the boundary layer. Weak ascent within this layer and may allow for some spotty sprinkles or drizzle to develop as low clouds expand westward, with areas along/south of I-80 across northwest IN and east central IL most favored for this spotty light precip. Otherwise, dry conditions with partly to mostly cloudy skies can be expected elsewhere. Going forecast has all of the above well in hand this evening. Only grid tweaks were to adjust low chance pops and cloud cover a bit based on satellite/radar trends this evening. Ratzer && .SHORT TERM... 240 PM CDT Through Tonight... A fairly quiet Saturday continues across the area. Residual low level moisture has been pesky to depart over Lake Michigan and areas along and east of I-57, where generally cloudy conditions persist this afternoon, keeping temperatures lower to mid 70s and 10 degrees below normal for the middle of meteorological summer. Elsewhere highs are peaking around 80 away from the lakeshore. Within the low clouds, isolated light showers have developed in northwest Indiana, assisted by subtle convergence at and below 850 mb. Satellite visible imagery does show a broad low level circulation in the boundary layer wind field aiding congested stratocumulus over northwest Indiana. Expect to see isolated showers, mainly light, continue in this area into late afternoon or early evening. The thunder potential looks low (less than 10 percent) with mlCAPE in excess of 500 J/kg mainly confined to just east of the CWA. Further to the west over north central Illinois, a non-exciting cumulus field highlights a corridor of mid 60s dew points and slight low level speed convergence. Cannot rule out a shower or two developing, but that would be about it. For tonight the conundrum becomes lower clouds. After clouds had pulled away from the Illinois shore area around noon, they have since retrograded back. This is a sign the 850-950 mb flow is becoming more easterly as the weak inverted trough/circulation feature moves slowly southwestward across northern Indiana. With low clouds expected to remain over the lake and northwest Indiana into east central Illinois going into evening, can envision how some of this will expand/retrograde westward over a good part of the area after dark. Guidance has been trending toward that solution more through today. Some of the clouds are likely to be of a few thousand feet depth in northwest Indiana into east central Illinois, as well as possibly up into the Chicago metro. Given the low level profiles and some weak ascent, would not be too surprised to rattle out some spotty light drizzle again. If there were to be some clearing of any of the aforementioned areas after dark, there would be low temperature-dew point spreads favoring fog development. At this time though given the trend toward more cloudy, fog is a low confidence solution. MTF && .LONG TERM... 240 PM CDT Sunday through Saturday... The upper trough which has been impacting our weather for the past several days will have one more day of influence before shifting off to the south Sunday night. The associated surface low will be well off to the east toward New England by Sunday morning but a weak surface inverted trough axis will trail it and arc back into the local area. This will provide some very modest low level convergence which may be enough, when combined with modest lower level isentropic ascent, to generate some spotty showers Sunday morning into early Sunday afternoon. Modest instability develops toward midday so thunder would also be a small possibility. A warm nose aloft may inhibit anything from developing but the favored area would be generally along and south of I-80. Will continue with minimal slight pops to cover this small potential. Otherwise expect highs in the lower 80s with the exceptions being near the Lake Michigan shore where low to mid 70s are expected and areas along and south of roughly US-24 where cloud cover should be most persistent and result in highs closer to 80. The main upper ridge which has been in place for quite some time over the western U.S. and Canada will remain in place with a secondary west-east oriented upper ridge replacing the upper trough that will be departing the local area. This will also allow surface high pressure to build in Monday yielding quiet weather. Quiet weather continues into Tuesday but there continues to be good agreement on a weak cool front pushing down the lake later Tuesday afternoon. Highs will warm into the mid or even upper 80s ahead of this front. With the high to the south there is not really any moist return flow or significant moisture influx so shower/thunder potential should be minimal at this point but it remains something to watch. Slight cooling will occur for Wednesday with highs in the lower to mid 80s with flow off the lake keeping lakeshore areas in the 70s. The upper flow doesnt really change much through the rest of the week aside from the western ridge broadening somewhat at times. Northwesterly flow aloft will continue to bring periodic but rather subtle troughs across the area which will mean more windows of opportunity for low shower/thunder chances through late week. Warmer air will likely work back into the area with mid and upper 80s for highs and more humid conditions developing with 70 degree dewpoints expected to return. MDB && .AVIATION... For the 00Z TAFs... 627 PM...Only forecast concern is mvfr cigs this evening. Mvfr cigs continue near Lake Michigan and into northwest IN and are expected to slowly lift and scattered by late evening but low confidence, especially for gyy. Its possible mvfr cigs may continue for areas south of the terminals overnight into Sunday morning. A vfr cu field is expected Sunday which will dissipate with sunset Sunday evening. Northeast winds around 10kt will slowly diminish this evening, possibly turning more northerly overnight. Winds will turn back to the northeast or easterly Sunday with speeds back to 10kt. cms && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
631 PM CDT Sat Jul 17 2021 .UPDATE... Issued at 551 PM CDT Sat Jul 17 2021 Latest surface analysis places the sluggish cold front that is aiding convection across southern MO right near the southernmost tier of counties in the CWA. Despite the storms moving at a glacial pace in the absence of notable steering flow, they are typically short-lived. However, they will be monitored through the night for any flash flooding potential. Behind the weak front, slightly drier air is being ushered into eastern MO and western IL. With 70F+ dew points now impinged south of St. Louis, fog potential should be limited to southeast MO/southwest IL along with river valleys. High clouds from ongoing convection in southwest MO may also weaken radiational cooling tonight and keep fog potential even more limited. Tomorrow`s forecast remains on track, with one minor addition of slight chance PoPs across west-central IL during the afternoon. CAMs, global models, and high-res ensemble guidance hint that a localized area of higher moisture could provide enough CAPE to spark isolated showers/storms. They should be short-lived in the absence of notable forcing, and the threat will diminish after sunset. MRB && .SHORT TERM... (Through Late Sunday Night) Issued at 251 PM CDT Sat Jul 17 2021 The cold front responsible for the showers and storms experienced the last couple of days has made its way just south of the CWA, and high pressure is centered over the Midwest. Residual boundary layer moisture just behind the front and 1,500-2,000 J/kg of SBCAPE per SPC mesoanalysis has allowed for convection to form in portions of central and southeastern Missouri. RAP soundings from these areas show poor lapse rates and a warm nose at roughly 700-600 mb, limiting convective growth. Therefore, I expect convection that forms in these areas to remain weak and short lived. Our focus for this evening and overnight is the upper-level shortwave and MCV seen over eastern Kansas presently. It is expected that the MCV will continue its southeastward trajectory, skirting the southwestern and southern portion of the CWA this evening and overnight. The 12z HREF kept convection well confined to portions of southeastern Missouri and southwestern Illinois, but recent HRRR runs have edged convection a little further north toward the I-70 corridor as the MCV passes by. Given the aforementioned lapse rates over the CWA and generally unfavorable environment for convection, I`m not sure I buy in to this recent, more northerly solution just yet. That being said, I`ve taken somewhat of a middle ground and edged the chance of scattered showers a little further north than the previous forecast and kept them going longer tonight. With limited instability and 0-6 km shear around 15 kts, convection will remain weak and thunder will be limited. However, precipitable water over southeastern Missouri and southwestern Illinois is around 1.5-1.75", and if heavier showers move over areas that saw high rainfall totals recently, an isolated flash flood threat may be realized tonight, but I have low confidence in that at this time. Additionally, with the relatively same airmass in place over the CWA tonight as was last night, I can`t rule out another round of patchy fog. Current surface obs show dry air pushing into the CWA from the northeast, but I`m uncertain with how far this will make it into the CWA. I currently have patchy fog in the forecast mainly for portions of southeastern Missouri and southwestern Illinois where surface moisture is higher thanks to recent rainfall. Tomorrow`s convective trends largely depend on what happens tonight, but confidence remains high that the best chance for isolated to scattered showers and maybe a brief thunderstorm to occur is over portions of southeastern Missouri where boundary layer moisture will remain sufficient for convection. Temperatures will remain below normal thanks to the post-frontal high pressure remaining centered over the Midwest. Elmore .LONG TERM... (Monday through Next Saturday) Issued at 251 PM CDT Sat Jul 17 2021 Through the first half of the upcoming work week, the upper- level pattern will hold, with a trough over the eastern U.S. and an amplified ridge over the western half of the country. This will keep the Middle Mississippi Valley in northwest flow aloft, and at the surface, an area of high pressure will keep winds northeasterly at the surface. This setup will help keep temperatures at or below normal through Wednesday. For Thursday through the end of the extended period, ensemble guidance shows the western ridge building eastward. In response, the surface high will drift eastward and return southerly low-level flow to the CWA. This flow will advect warm, moist air into the region, leading to an increase in temperatures and humidity by the week`s end. Ensemble solutions diverge near the end of the period with the expansion of the ridge relative to the Middle Mississippi Valley, leading to uncertainty with weather at the surface - particularly rain chances. With the increase in boundary layer moisture and uncertainty with the upper- level flow, I can`t rule out a low chance of convection over portions of the CWA, but my confidence is higher in a mostly dry forecast for the week`s end. Elmore && .AVIATION... (For the 00z TAFs through 00z Sunday Evening) Issued at 551 PM CDT Sat Jul 17 2021 VFR conditions are currently forecast at all terminals through the valid TAF period, however indications of brief MVFR CIGs do appear in the guidance. A weak cold front is now draped across southern MO and far- southern IL, with slightly-drier air behind the boundary. This drier air, coupled with high clouds from convection in western MO, should counteract the potential for fog redevelopment tonight at the terminals. Guidance is also hinting at MVFR CIGs approaching the terminals tomorrow morning, but it appears that the best chances for this stay clear of the sites. That being said, SCT MVFR wording was left in at all terminals to hint that clouds could be that low. Winds will remain relatively light and generally northeasterly through the period. MRB && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Marquette MI
755 PM EDT Sat Jul 17 2021 .SHORT TERM...(This evening through Sunday) Issued at 228 PM EDT SAT JUL 17 2021 Overall quiet weather day across the region. With high pressure dominating the scene, clear skies and light winds have persisted through the day. With the ample sunshine, most areas climbed into the 70s to low 80s. Haze from the forest fires upstream in Canada has once again drifted over the region. For most of the day, the haze has been isolated to Lake Superior and the Keweenaw. Much of the same is expected tonight. Dry conditions and light winds will allow temps to fall into the 50s inland with some high 40s possible at the traditional cold spots. By the lakeshores, the warmer water should moderate air temps, preventing lakeshore communities from largely escaping the 60s. Tomorrow, the high will sink south some. With the mid-level winds continuing to transport smoke from the upstream fires over the region, expecting another hazy day. HRRR smoke products even suggest some of this mixing to the surface in the interior portions of the UP and along the Lake Superior lakeshores. This makes sense given dinural mixing. Warming aloft will allow for temps to be a few degrees higher tomorrow, with most seeing 80s. Lakeshores east of Marquette have the best shot of staying in the 70s. Interior locations should climb into the mid-upper 80s. .LONG TERM...(Sunday night through Saturday) Issued at 310 PM EDT SAT JUL 17 2021 The overall large-scale long-term pattern will consist of western CONUS ridging and downstream troughing from Hudson Bay into the Canadian Maritimes. Between these features, upper-level NW flow is expected to rule the long-term period over the Upper Midwest and Upper Great Lakes. Monday looks like it will be the warmest day of this recent warm stretch with afternoon 850 mb temps roughly from 16C east to 19C west. GFS soundings advertise fairly deep mixing to 7-8 kft under sunny skies and a west wind. This deep mixing will likely drop dew points into the mid 50s east to lower 50s over the interior west. The NAM soundings depict a different story maintaining dewpoints around 60F through the day with afternoon MLCAPE values of 500-1000 j/kg. Even with the NAM`s typical moisture biased solution, it would be difficult to initiate convection on Monday given that there still would be some CIN and quite a bit of mid-level dry air to overcome. Will likely side with the drier GFS solution and lowering of dew points in the afternoon with the deep mixing through the dry air mass. Max temps will be well into the upper 80s across much of the area, possibly topping out at 90F over a few interior locations. Min RHs could dip near 30 pct interior west and central but with fairly light winds not expecting any fire weather concerns. Smoke likely lingering from Canadian wildfires could cause some minor obscuration of sky cover and maybe some haze across the area. By Monday evening, a strong cold front will be approaching from the north. Forcing with the front will likely kick off scattered showers Monday evening in the west which would spread into eastern counties after midnight. The NAM, Canadian and ECMWF would indicate enough destabilization (MUCAPEs up to 1000 j/kg) for thunder as well, but that would hinge on how effectively moisture can be advected in ahead of the front. Given that Monday afternoon likely will result in lowering of dewpoints ahead of the front, the probability of thunderstorms may be more questionable. Will maintain only slight chc pops for thunder Monday night per NBM grids. Tuesday, behind the front, cloud cover may be slow to clear in the morning. This along with a steady north wind and 850 mb temps dropping to around 10-12 C should hold temps down in the mid to upper 60s north to lower to mid 70s for south and east for highs. Mixing behind the front should at least temporarily scour out smoke from Canadian wildfires. Wednesday should see may temps rebounding into the mid 70s to lower 80s, as onshore northerly flow subsides and weak WAA ensues from the west. The Wed temp fcst may be further complicated by cloud cover as a few of models hint at a weak nw flow shortwave moving across the area late in the day which could increase cloud cover and maybe bring a chance of showers/t-storms into the area. The consensus of operational models and ensembles indicate the next chance of rain is somewhere around Wednesday night or Thursday when a more prominent NW flow shortwave and associated frontal boundary drop southeastward across the Upper Great Lakes. Similar to Monday night, there could be a thunderstorm chance with this wave, but again moisture return ahead of the wave looks questionable. Model agreement and resolution of nw flow shortwaves is poor beyond Thursday of next week, but this will be something to watch with future model runs, as experience tells us nw flow shortwaves can sometimes bring unexpected rounds of convection given adequate moisture in place. With no change to the upper-level pattern in sight, expect mostly above-normal temps to continue for late next week into the weekend. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 738 PM EDT SAT JUL 17 2021 Smoke taking over Upper Michigan today has obscured the skies, but up until just before this TAF issuance, hadn`t had much of an impact on surface visbys. If it weren`t for the smoke, conditions would be SKC/VFR. It is questionable whether or not the surface obscurations (currently still VFR though, just on the cusp of MVFR) will continue overnight since an inversion is anticipated to setup, but with smoke already mixing down, it is possible that some of it ends up getting trapped. If that`s the scenario that ends up playing out, then anticipate the 6SM (or lower) to persist at the terminals into tomorrow. Will be monitoring trends over the next few hours to determine if the current 03z end time for smoke mention will be reasonable. Otherwise, light and variable to calm winds will prevail at all three terminals through the TAF period. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 228 PM EDT SAT JUL 17 2021 Surface high persisting over the Upper Great Lakes will keep winds light through the weekend. A cold front is expected to drop south over Lake Superior Monday night. Southwest winds will increase to near 20kts ahead of the front over the west half, particularly in between the Keweenaw and Isle Royale. Following the frontal passage, winds are expected to become north to northeasterly at 20 to 25 kts through Tuesday morning. Another high is expected to build into the region and send winds back down to 15 kts or less through the end of next week. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JP LONG TERM...Voss AVIATION...lg MARINE...JP
Area Forecast Discussion
National Weather Service Norman OK
235 PM CDT Sat Jul 17 2021 ...New SHORT TERM, LONG TERM... .UPDATE... Issued at 101 PM CDT Sat Jul 17 2021 Update to increase PoPs further south. Deep, moist convection will continue to develop along and outflow boundary and ahead of a remnant MCV moving out of the TX panhandle thru this afternoon. Although deep layer shear is lacking a bit, moderate instability and high low level theta-e will likely contribute to a few robust updrafts developing within clusters into at least the early evening hours. In fact, one supercell is currently located near Okeene. The main threat will be damaging wind gusts along this boundary into the evening, perhaps nearing portions of the OKC metro, where DCAPE ridge will reside from there SE along the I-44 corridor. High rainfall rates will also accompany the storms so localized flash flooding appears a bit more likely now. All grids have been sent. && .SHORT TERM... (This evening through Sunday) Issued at 224 PM CDT Sat Jul 17 2021 Scattered thunderstorms will continue through the afternoon and evening across the region. It appears that the overall intensity should diminish after sunset, as storms lose their ground connection (become elevated). Elevated storms are expected to continue overnight, and into Sunday morning, when a similar scenario to today`s should redevelop. Storms may be marginally severe again, or at least threaten to be severe, particularly across the northern half of Oklahoma. Temperatures will be highly dependent on precipitation this afternoon and early evening. HRRR values, with some slight southward geographic alterations, seemed to be the best bet for the rest of today. CmS && .LONG TERM... (Sunday night through next Friday) Issued at 224 PM CDT Sat Jul 17 2021 The Sunday night/Monday/Monday night shortwave trough appears to be on schedule, still. It will bring more organization to the otherwise near-random pattern of convection as it passes north- to-south across the region. In its wake, a somewhat cooler and drier airmass is expected to cover Oklahoma, and to a lesser extent, north Texas for a few days. As the week progresses, a large ridge across the western part of the country will expand into the Plains. The position of the ridge will keep Oklahoma/north Texas in generally north to northeast flow (aloft...mainly southerly at the surface) for several days. During this time, temperatures will begin to creep back up, and rain chances will dwindle to near zero...unless one or more of the small upper-level disturbances randomly forecast by the medium range models actually comes to fruition. CmS && .AVIATION... (18Z TAFS) Issued at 101 PM CDT Sat Jul 17 2021 Thunderstorms will continue to develop from near SWO to north of CSM over the next few hours and move SE later today. Very heavy rainfall will accompany them so expect visbys to easily drop to 3SM and may need to amend for lower. It`s unclear how long this activity will last thru tonight so possible adjustments/inclusions of TS to SPS and LAW could be needed. && .UPPER AIR... Issued at 101 PM CDT Sat Jul 17 2021 An Upper Air flight is not planned for today. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 73 92 70 86 / 40 40 50 60 Hobart OK 72 94 71 89 / 40 20 40 50 Wichita Falls TX 75 95 74 91 / 20 20 20 50 Gage OK 70 94 68 89 / 40 30 50 40 Ponca City OK 70 87 69 84 / 30 30 60 60 Durant OK 75 94 73 90 / 20 30 30 60 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && $$ SHORT TERM...23 LONG TERM....23 AVIATION...03
Area Forecast Discussion...
National Weather Service Portland OR
311 PM PDT Sat Jul 17 2021 .SYNOPSIS...Upper level high pressure over the Intermountain West and upper low pressure over the northeast Pacific will result in near to slightly above average temperatures and dry weather for much of the next week. && .SHORT TERM...This evening through Tuesday...Recent 6.19 micron (high level) water vapor imagery continues to show an upper level trough across the eastern Gulf of Alaska near the central BC coast. Short-range models agree that this feature will remain quasi- stationary throughout the short-term. The GFS and ECMWF suggest our 500mb heights will increase somewhat (by around 3-7 decameters) between now and tomorrow night, before they begin to decrease again from the west-northwest as a small amount of energy associated with the trough moves into the area Monday night/Tuesday. From a practical standpoint, this implies our observable weather will remain quiet through the short-term, with the warmest temperatures expected tomorrow and Monday before a slightly cooler Tuesday. Both Sunday and Monday, afternoon temperatures will likely peak in the low 80s to around 90 across the Willamette Valley and in the 60s along the coast where onshore flow will ensure a continuous supply of marine-chilled air. 7.34 micron (low level) water vapor imagery shows a dry slot induced by subsidence behind a decaying front moving northeast across the Pacific a few hundred km off of the OR and CA coasts. As we would expect based on the movement of this region of drier air, the NAM, RAP, and UW-WRF agree that relative humidity will stay significantly lower across our area tonight compared with last night. In addition to weak subsidence acting to suppress the depth of the marine layer, the Spokane to North Bend gradient is forecast to be a tiny bit weaker tonight by both the GFS and NAM, which have it peaking at around 8mb (it reached 9.4mb last night). Moreover, forecast soundings from the GFS, NAM, and RAP agree that the marine layer - nearly 2km last night at Astoria, where 0.03" of drizzle was observed - will only reach around 1,000ft in depth tonight. All of this is to say that we are not expecting drizzle tonight, or tomorrow night for that matter. For Monday night/Tuesday morning, Bufkit soundings suggest the marine layer will deepen to nearly 1km (around 3,281 feet), so drizzle might be possible along the north OR/south WA coasts again then, but it`s a bit far out in time to add a mention. According to HREF guidance, tonight and tomorrow night are likely to remain mostly cloudless in the Willamette Valley, so we are expected to cool off a bit more overnight to get relief from the warmer daytime temperatures expected. -Bumgardner .LONG TERM...Tuesday night through Saturday...As has been the case all week, WPC`s cluster analysis (which shows 4 reasonably possible solutions composed by an algorithm which groups individual ensemble members from the ECMWF, CMC, and GFS by similarity) indicates excellent agreement in the overall synoptic-scale pattern at the beginning of the period: The quasistationary 500hPa (upper level) low still spinning along the central BC coast, and a strong ridge favoring tranquil weather to our east over the northern Plains. Thereafter, the pattern gradually becomes increasingly indeterminate, with one cluster favoring a westward building trend in the behavior of the ridge to result in rising heights across our area, two other clusters depicting a continuation of troughing for the PacNW, and another suggesting zonal flow. In all cluster scenarios, the deviation from average 500mb heights is expected to be between -30 and +90 meters (not a huge range), which suggests temperatures are likely to remain near to slightly above normal. In terms of weather, the main difference between one solution and another is the strength of nocturnal marine surges resulting from different possible flow patterns. This will indirectly impact temperatures as well, with marine stratus both reducing nocturnal cooling and delaying the onset of solar heating (so depending on the timing of its arrival and dissipation, temperatures are a tricky thing to forecast this far out). The NBM suggests high temperatures will likely dip a bit to near normal Tuesday through Thursday before rising to above average again on Friday. By Friday, the bounds of the wiskers (i.e., the 10th and 90th percentiles) given by the NBM`s 1D viewer temperature forecast at PDX (relatively representative of the Willamette Valley) are 80-91 and at Astoria (relatively representative of at least the north Oregon/south Washington coasts) are 66-71. This far out, we have left deterministic NBM`s forecast untouched, but, as is always the case in the extended timerange, there is considerable uncertainty. -Bumgardner && .AVIATION...Dry and stable westerly flow aloft will maintain VFR with mostly clear skies. Onshore flow will continue, but not as strong as past few days. With that, will see areas of MVFR to IFR stratus reform along the coast later tonight, mainly to north of Newport. Farther inland, would expect skies to remain clear, though may have patchy MVFR stratus from late tonight into early to mid Sunday morning along the lower Columbia River as far south as Portland, as well as in the Cowlitz Valley. For detailed regional Pac NW aviation weather information, go online to: KPDX AND APPROACHES...No adverse weather impacts expected, as high pressure maintain clear skies today and tonight. While not likely, still have minor potential for patchy MVFR stratus in/around ops area, mainly over Clark County to east Portland metro. If happens, would be between 12Z and 16Z Sunday. && .MARINE...Benign weather pattern over the waters continues, with high pres well offshore and thermal trough over far Oregon coast into nw Calif. This will maintain northerly winds on the coastal waters, with 10 to 15 kt for most areas, with gusts up to 20 kt south of Cascade Head in the afternoons/evenings. Seas will hove at 3 to 5 ft range. A weak front will push across region later next week, but not much change in winds, as speeds stay at 10 to 15 kt. && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && Interact with us via social media:
Area Forecast Discussion
National Weather Service Springfield MO
650 PM CDT Sat Jul 17 2021 ...00z Aviation Update... .SHORT TERM...(This evening through Sunday) Issued at 209 PM CDT Sat Jul 17 2021 Scattered showers and thunderstorms have developed this afternoon across the area, especially the southwest half of the area. This was in response to increased low level moisture and lift associated with an incoming shortwave across northeast Kansas. A surface front was located from Kansas City, to Lake of the Ozarks, to Farmington. This front also had some isolated showers and storms along it. PW values were likely in the 1.5-1.75in range, with MU capes of 2000-3000 j/kg. Wind shear was very weak, with 850-300mb mean wind of 5-10kts out of the west, therefore storms were drifting slowly east. Lightning and brief heavy rainfall are the main threats this afternoon. With clouds around, highs in the middle 80s are likely. Going into this evening and tonight, somewhat complicated forecast with the incoming shortwave and several boundaries around. Latest high res guidance has gone back and forth on the potential for heavier pockets of showers and storms this evening and overnight. Thinking that two main areas are possible, one area being across se Kansas and far southwest Missouri, closer to the incoming shortwave and higher moisture axis. The other area may be closer to the front that is just north of Springfield. Given the high moisture content and slow storm motions, localized flooding will be possible with some small pockets of 2-3 inches showing up in 12z HREF and latest HRRR guidance. Confidence is just too low to highlight an area for a Flood Watch tonight, however will continue to monitor trends. Some areas may not see any rainfall. Winds turn more northeasterly on Sunday as the front looks to move through most of the area. Should be some isolated to scattered storms develop by afternoon across southern Missouri, generally along and south of Interstate 44. Highs will be similar to today, in the lower to middle 80s. .LONG TERM...(Sunday Night through Saturday) Issued at 258 PM CDT Sat Jul 17 2021 A shortwave trough will continue rounding the eastern periphery of an upper-level ridge, centered across the Intermountain West, during the evening Sunday. Combined with the slowly advancing front, at least isolated PoP chances will remain for southern MO until the front clears Sunday night. Dry weather can be expected once frontal passage occurs. Surface high pressure will keep most of the area dry Monday. An outside chance of a scattered shower or storm exists across the southern CWA as cold temperatures aloft, associated with a weak upper-level disturbance, may yield sufficient instability for isolated convection. Dry weather is anticipated both Tuesday and Wednesday as the region will continue to be dominated by surface high pressure. High temperatures both days are expected to be in the mid-80s, slightly below normal for this time of year. Long-range guidance indicates that the western CONUS ridge may begin to deamplify some towards late next week into next weekend. If this occurs, the region may enter a more classic "northwest flow" regime on the eastern periphery of the ridge. The potential would exist for some increase in convective activity with any subtle shortwave embedded in the flow. Specifics remain highly uncertain and thus will only include low PoPs for Thursday- Saturday for now. Otherwise, temperatures will be seasonable in the upper-80s to low-90s. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 636 PM CDT Sat Jul 17 2021 Scattered showers and thunderstorms will continue through the evening across southern Missouri, most likely affecting KSGF and KBBG through 03z. Expect brief periods of MVFR to perhaps IFR conditions if heavier storms impact the terminal. Otherwise, lowered (MVFR) ceilings are forecast to develop at all terminals toward 08-10z Sunday and persist into the late morning. Areas of patchy fog may also develop, though overall confidence in such an outcome remains low at this time. Scattered showers and perhaps a thunderstorm are possible beginning in the early afternoon Sunday, which may again briefly reduce flight categories at all terminals. && .SGF WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && $$ SHORT TERM...Burchfield LONG TERM...Ungar AVIATION...Ungar
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
454 PM MDT Sat Jul 17 2021 .DISCUSSION...(This Evening Through Saturday) Issued at 1241 PM MDT Sat Jul 17 2021 The latest water vapor satellite and associated RAP 500-mb analysis showed an upper high over NM with anticyclonic flow extending northward across the CWA. Very weak and subtle short-wave troughs were embedded in the flow across the Rockies, but Q-vectors and negative CVA indicated weak subsidence for the CWA. The latest MLCAPE was 250-1250 J/kg from west to east across the CWA, but MLCIN also was -100 to -250 J/kg for much of the CWA. Given the minimal upper forcing and capping, expect thunderstorm coverage/development to be hindered this afternoon/evening. CAMs have agreement on weak storms firing over the BLKHLS by 21z, with additional storms near a psuedo dryline/surface trough over northeastern WY after 21z -- eventually moving over southwestern SD. This is supported by a very subtle short-wave trough moving through central WY ATTM. The 0-6km bulk shear will be favorable for a few supercells given modest midlevel northwest flow atop low-level southeast flow, with southerly RM motions and east-northeasterly LM motions. A low-level jet of 25-30kt and the weak upper wave may help sustain storms over southwestern SD into mid-evening. CAMs also suggest a few storms over northwestern SD late this afternoon and especially into the evening, but confidence in this is somewhat lower. The overall upper pattern will not change appreciably for the upcoming 5-7 days as high pressure remains over the central/southern Rockies and anticyclonic flow mostly dominates over our CWA. Decent l apse rates and MLCAPE still will be present on Sunday, but again with very weak forcing (likely subsidence) and notable capping. However, will add small chances for storms over the BLKHLS where heating and upslope flow may favor some convective development, and also will keep PoPs for south-central SD where richer moisture, higher MLCAPE, and weak surface convergence may favor a few storms. Midlevel lapse rates decrease for Monday and Tuesday with minimal chances for storms, except for possibly northeastern WY on Tuesday where lapse rates are steeper and PWAT values reach 150-200 percent of average. Tracking upper waves beyond 1-2 days will be difficult in this weak flow pattern, but cannot rule out storms completely, especially toward the end of next week when the ridge may break down a little. Otherwise, the low-level thermal ridge will remain mostly just to the west of the CWA, and considerable smoky haze at times will persist. Thus, although temperatures will be above-average, it may be difficult to reach the 100s. Finally, although RHs will be low at times, winds will be light overall, and the intersection of low RH and high winds greater than 25 mph appears unlikely at this time. && .AVIATION...(For the 00Z TAFS Through 00Z Sunday Evening) Issued At 452 PM MDT Sat Jul 17 2021 Scattered TSRA over the Black Hills will shift into southwest SD early this evening then dissipate. Areas may experience localized MVFR conditions in storms as well as potential for strong erratic winds and hail. Outside of any thunderstorms, VFR conditions are expected through the period. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ DISCUSSION...Bunkers AVIATION...Johnson