Area Forecast Discussion
Issued by NWS Omaha/Valley, NE
Issued by NWS Omaha/Valley, NE
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
871 FXUS63 KOAX 230506 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1206 AM CDT Sun Jun 23 2024 .KEY MESSAGES... - Flooding of the Missouri River tributaries in southeast South Dakota and northwest Iowa will lead to increased water flow into the Missouri River downstream of Sioux City. Flood warnings are in effect along the Missouri from Decatur to Rulo beginning early next week. - There is less than a 5% chance of severe thunderstorm development in southeast Nebraska through early evening, with damaging winds the primary hazards. - The hottest temperatures so far this year are expected Monday and possibly Tuesday, with heat index readings of 100 to 110. - There will be additional storm chances next week, with occasional severe weather and heavy rainfall possible, particularly on Tuesday and Friday. && .DISCUSSION... Issued at 358 PM CDT Sat Jun 22 2024 Quasi-zonal flow prevails across the northern plains this afternoon, with a short wave feature moving eastward into the Great Lakes region. An attendant frontal boundary is slowing moving through the forecast area, so far only marked by a wind shift and slightly cooler temperatures. Diabatic heating will allow SB/MUCAPE to increase into the 1500-2500 J/kg range by late afternoon with bulk shear 30-35kt. Diabatic forcing combined with weak large scale forcing and low level convergence may be sufficient to develop isolated thunderstorms late this afternoon, generally south and east of Harlan IA to Omaha- Council Bluffs to Pawnee City line. Given bulk shear values on the low side, it may be difficult to storms to sustain updrafts, thus any storm that reaches severe limits may collapse producing isolated damaging wind gusts. The front is expected to move south of the forecast area early this evening, effectively ending the severe weather threat. The rest of the evening will be characterized by clearing skies and light northwest winds, with temperatures falling into the 60s. Sunday through Tuesday: Upper level riding amplifies as aforementioned short wave feature carves a long wave trough across the eastern U.S. bisecting southern tier H5 dome. The sensible weather effect across the forecast area is a dramatic increase in temperatures, especially Monday. Temperatures on Sunday will be about 5 degrees above normal, with upper 80s and lower 90s expected, and heat indicies in the mid 90s. Monday will be the sizzler of the week, with high temperatures in the upper 90s to lower 100s and heat indicies 100 to 110. There still is some spread in the forecast guidance, with half the at least one of the ensemble clusters indicating less ridging. 75+% confidence in heat headlines being issued in the next 24 hours. Tuesday, the signal is a little mixed. A vortex moving across the central Canadian provinces has a slight reflection in the form of a diffuse upper level disturbance that moves across the central plains Monday night into Tuesday, dragging another weak cold front across the region. Synoptic models and medium range ensemble clusters indicate the development of a MCS that will move across the area, mainly affecting northeast Nebraska and western Iowa. Convective cloud debris and cooling from the passage of the front may impact the level of warming, except for southeast Nebraska and southwest Iowa. Still, NBM 25-75% temperatures near or above 90 in most locations. Redevelopment of storms along the front later in the afternoon appears possible, which could further limit temperatures. Rainfall amounts do not appear excessive at this time, with model QPF a quarter inch or less, thus would not expect flooding situation to be exacerbated. However, precipitable water values will be in the 75% of climatology, thus isolated heavy rainfall may be possible. Wednesday Through Saturday: A relatively quiet weather day on Wednesday, with slightly above average temperatures and no precipitation expected. A large scale trough develops across the western U.S. coast Thursday, with medium range deterministic and ensembles ejecting systems quickly eastward Friday and Saturday across the northern U.S. and southern central Canada. One or more convective complexes will affect the area, with the possibility of severe weather and heavy rainfall, with the grand ensemble indicating a 20 to 40% probability of sufficient CAPE and shear for severe weather on Friday. Temperatures will trend slightly above average Wednesday through Friday, with more seasonable temperatures on Saturday. Similarly the probability of 1 inch or greater rainfall occurring somewhere across the region is 30 to 50%. The additional rainfall could delay the recession of the Missouri river if realized. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1203 AM CDT Sun Jun 23 2024 Latest runs of the short-term models suggest that fog chances are decreasing at KOMA, but have elected to keep them in with the expected slight winds, and potential for it to still by patchy. Aside from the fog chances, winds have slackened and will become calm to somewhat variable in not from the northwest, and will return southwesterly tomorrow morning and turn southeasterly while staying light. && .HYDROLOGY... Issued at 358 PM CDT Sat Jun 22 2024 Flood warnings have been posted along the Missouri River downstream from Sioux City to Rulo. The successive river forecasts during the past 24-36 hours have lagged the onset of flooding and crests, forecasts are tracking with observations more closely. This will be the first time since 2020 that the Missouri has been in flood along its entire reach in the HSA. Additionally flooding is occurring along Ponca Creak from its headwaters to Verdel, with some indications that the river could re-crest again based on the National Water Model. River levels also are above action stage along the Platte between Schuyler and North Bend, Loup upstream of Columbus and Clear Creek. Fortunately there will be no precipitation in the short-term to affect rivers in the next 24-48 hours, but precipitation Tuesday and onward could impact the recession of the Missouri, and cause other area rivers to rise from Wednesday onward. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Fortin AVIATION...Petersen HYDROLOGY...Fortin