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
431 FXUS63 KOAX 282312 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 612 PM CDT Fri Jun 28 2024 .KEY MESSAGES... - Moderate flooding is ongoing or expected to begin along the Missouri River the next day or two. It`s forecast to last into next week for Omaha and points south. - A few severe storms are possible this afternoon and evening with the potential for large hail, damaging winds, localized flash flooding, and perhaps a tornado or two. - Quiet and cooler for the weekend, with highs in the mid 70s to lower 80s. Then warming back up and becoming more active for the holiday week. && .DISCUSSION... Issued at 255 PM CDT Fri Jun 28 2024 The current scenario at 3 PM Friday has a persistent area of light rain showers, with elevated parcel inflow regions, extending from Monona county back to Gage county. There have been a few lightning strikes within this activity, but for the most part they have been few and far between. However, the southern tip of this area has shown recent signs of deeper convective updrafts, and is likely beginning to interact with near surface parcels. Mixed layer inhibition has decreased to less than 25 J/kg while an axis of MLCAPE greater than 2000 J/kg has developed amidst surface temperatures near 90 and dewpoints in the middle to upper 70s in far southeast NE and southwest IA. Effective shear is also in the 30-40 kt range in this area. All of this suggests a window for strong to severe convective development over the next 2-3 hours, seemingly focused south of a line from Nebraska City to Red Oak, and points east. If storms are able to surface base and organize, would anticipate a period of large hail production as well as generally isolated wind damage potential correlated with any stronger downbursts. While there is a pre-frontal wind shift across the region, the true cold front at 3 PM was analyzed near a line from near Onawa back toward Fremont, and then down to around Seward, and is making some southerly progress. With the light and/or westerly flow in advance of the front, and northerly flow that isn`t particularly strong behind the front, the boundary layer convergence is present but not especially strong. This is reflected in the shallow cumulus field in this area. But, as we progress into the evening, some cool advection aloft and weak height falls moving into the region may be sufficient to help initiate new convection near the front in combination with the weak boundary layer convergence. Inhibition is expected to become weak or non-existing while CAPE will likely still be in the 1500-2500 J/kg range and effective shear will be sufficient for storm organization. Thus, we will need to continue monitoring the front, especially in the 5-8 PM time frame for new development as it could become severe with similar hail/wind hazards to any afternoon activity. There is a non-zero tornado potential, but it does look to be a very small potential, and mainly tied to any intense updrafts that can develop near the front and stretch existing vertical vorticity. After the front and any associate storms push east, there is a likelihood for a few storms to be moving east across central NE. However, these storms will be entering an increasingly hostile environment with eastward extent, and expect them to likely dissipate before reaching the local forecast area. Saturday and Sunday will be quite nice. There are a couple shots at a light shower Saturday morning and mid day, but more likely that we`ll see some cloud cover and virga rather than measurable rainfall. Still something to keep in mind. High temperatures both days will be in the 70s to lower 80s...with Sunday morning lows probably dropping into the 50s. Sunday night into Monday morning features a return of rain chances and warm humid conditions as a new storm system enters the Plains and brings a warm front back north. Sunday night looks more rainy than stormy, probably seeing a widespread 0.25 to 1.00. There may be some potential for a bit more locally, but not a major heavy rain threat at this time. As we go into Monday, it appears somewhat likely that severe storm parameters will again align with substantial CAPE and favorable hodographs for supercells. There are many details to work out regarding this period, but early indications are that all severe weather hazards will be possible Monday afternoon and evening. This is further amplified by the amount of atmospheric moisture returning to the region on Monday night. Moisture convergence on the LLJ appears favorable to produce some heavy rain, perhaps 2-3+ inches in some locations. A similar severe and heavy rain setup could develop on Tuesday, but will depend on the details of system timing from late Monday. The unsettled weather pattern probably continues through the end of the week, but looks like it may settle down into more of a dominant ridge pattern as we get into next weekend. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 611 PM CDT Fri Jun 28 2024 VFR conditions through the period with northerly winds less than 12 knots for the first half of the TAF, but increasing to 15-25 knots for the second half of the forecast. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Barjenbruch AVIATION...DeWald