Area Forecast Discussion
Issued by NWS Omaha/Valley, NE
Issued by NWS Omaha/Valley, NE
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147 FXUS63 KOAX 251719 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1219 PM CDT Tue Jun 25 2024 .KEY MESSAGES... - Flooding is expected to continue along the Missouri River this week. See the Hydrology section for more details. - Hot temperatures are expected to continue tomorrow, with a heat advisory in effect for heat indices as high as 106 degrees. - Scattered strong to severe thunderstorms will be possible (40-60 percent chance) this afternoon and evening with primary threats being large hail and damaging winds. A low tornado threat exists as well. - Scattered thunderstorms will return to the region Thursday night into Friday. Some locations may see up to an inch of additional rain heading into next weekend. A few storms may be strong to severe. && .DISCUSSION... Issued at 356 AM CDT Tue Jun 25 2024 Isolated to widely scattered storms surround our area but we`ve remained dry so far this morning. We could see the showers in north- central Nebraska spread eastward this morning leading to isolated storm chances in northeast Nebraska through 7 AM. More than likely, though, nothing will develop enough for accumulating rainfall to reach the ground. Temperatures stay very warm this morning, in the low-to-mid 80s as of 2:30 AM. Humidity is helping to keep temperatures up, which may keep morning lows up in the mid 70s across most of our area. Today will be another hot one, but a weak, stalled cold front across the northern half of our area will help keep temperatures and humidity lower across northeast Nebraska, while southeast Nebraska and southwest Iowa see heat indices get back up to 100 to 106 this afternoon. This boundary will act as a focus as a shortwave moving across the boundary will trigger storm development late this afternoon/early this evening. There is quite a bit of uncertainty in where this weak boundary will be by this evening, with some CAMs lifting it north focusing storm development along the Nebraska/South Dakota border, while others drop the boundary south to the Kansas border by 00Z, which would focus storm potential across southeast Nebraska and southwest Iowa. Half the CAMs keep storms east of our area completely. The National Blend of Models keeps storm chances down around 30 to 40 percent this afternoon, likely due to this spread in the models. In any case, instability across the region will be plenty sufficient with SBCAPE values around 3500-5000 J/kg. Shear will be maximized along this boundary which will likely see isolated supercells develop along it initially. Lack of any cap will likely lead to the development of convective clusters fairly quickly off of outflow boundaries from the initial storms. Primary threats with these initial storms will be damaging winds, large hail up to baseball-size, as well as a low tornado threat. As the convective clusters get established, expect a cold-pool to develop transitioning these storms into more linear clusters with bowing segments with more of a damaging wind threat. The bigger MCS does look like it should come together east of our area, impacting more of central Iowa down into northeast Missouri and western Illinois. We are mainly concerned with the potential across our area which covers the early stages of this system`s development. Any storms that do develop across our area should move off to the south or east by midnight tonight, and our severe threat will be over. Wednesday - Friday: Wednesday will be milder and very pleasant with dry, northerly flow across our area. Highs will only be in the mid 80s with humidity dropping to around 40 percent during the afternoon. We`ll see the return of the low-level jet Wednesday night shifting flow back to southerly out ahead of our next shortwave which will likely bring more numerous showers and storms to our area during the day on Thursday into Thursday night. Colorado State Machine Learning Algorithm highlights potential for severe weather Thursday evening - night across our area, so this is definitely a period to watch. A moderately strong cold front and strong low-level jet ahead of it definitely looks like the potential is there. Low shower and storm chances linger into Friday, though right now models show the better axis of moisture dropping south of our area with the cold front late Thursday/early Friday. Temperatures on Friday will depend on timing of the frontal boundary and if it drops completely south of our area, but right now we see temperatures get back up into the 90s across southeast Nebraska and southwest Iowa and stay down in the mid 80s to the north. Saturday - Monday: Confidence in forecast details drops off over the weekend, though the general pattern shows a dampening of the upper-level ridge as a broad surface high drops south out of Canada down into the Northern Plains. This appears likely to bring temperatures down, with ensembles putting the forecast highs in the upper 70s to low 80s Saturday and Sunday. Depending on how far south this surface high gets, we could stay mostly dry over the weekend, but we keep low precip chances as some models do show the potential for an overnight MCS Saturday night with showers lingering into Sunday. While we remain cooler, the upper-level ridge builds back up to our west over the weekend and will bring back hotter weather and storm chances going into early next week. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1156 AM CDT Tue Jun 25 2024 A weak surface front is draped across east-central Nebraska into southern Iowa. Areas north of this front (KOFK, KOMA) will see winds prevailing out of the east-southeast. Areas south (KLNK) will see wind prevailing out of the south/southwest. This boundary should remain relatively stationary until thunderstorms develop along it later this evening. After 21Z, scattered strong to severe thunderstorms are expected to develop in northeast Nebraska and move east-southeast across the region. Most likely timing for thunderstorms at KOFK and KOMA have been included in a TEMPO group, with the lower probability but still possible time frame for convection in a -SHRA FM group. There is still substantial uncertainty as to how far south convection will move, so have left precip out of KLNK TAFs for now. Wind gusts up to 60 knots and hail up to the size of baseballs will be possible in the strongest storms (most likely northeast Nebraska into southwest Iowa, KOFK and KOMA). Thunderstorms should move south and east of the forecast area by 06Z. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...Heat Advisory until 7 PM CDT this evening for NEZ045-051>053- 066>068-088>093. IA...Heat Advisory until 7 PM CDT this evening for IAZ055-069-079- 080-090-091. && $$ DISCUSSION...McCoy AVIATION...Darrah