Area Forecast Discussion
Issued by NWS North Platte, NE
Issued by NWS North Platte, NE
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172 FXUS63 KLBF 162031 AFDLBF Area Forecast Discussion National Weather Service North Platte NE 331 PM CDT Sun Jun 16 2024 .KEY MESSAGES... - Isolated to scattered severe thunderstorms possible across much of western and north central Nebraska this evening and tonight. Primary hazards include damaging wind, large hail, and perhaps an isolated tornado(es). - Another round of severe weather will be possible late Monday with the potential for damaging winds and large hail. - Near daily shower and thunderstorm chances continue across the area each day through the rest of the week into the weekend. The severe threat remains uncertain at this time. && .SYNOPSIS... Issued at 330 PM CDT Sun Jun 16 2024 Recent GOES-16 WV and RAP 500-mb analysis showed a ridge of high pressure situated across the southeast US, extending northward into the Great Lakes region. Multiple upper-level shortwave troughs were traversing along the upstreams of the ridge across the southern Plains into the western Great Lakes. Just to the west-southwest of this feature, a positively-tilted upper level trough was centered over the Washington/Oregon border. An upper-level trough of low pressure was swinging northeastward across Manitoba. Surface low pressure associated with this system is gradually shifting eastward into northern Manitoba, while an attendant cold front extends southwest across the Upper Midwest, stalling across southwest Nebraska. A dry line extends southward from a surface low located to the lee of the Rockies across eastern Colorado. These boundaries will have to be monitored very closely as we head into the evening as they will provide a focus for potential storm initiation this evening and tonight. In fact, recent satellite imagery is starting to show the first bubbling cumulus across northwest Colorado. As of 3 PM CT, temperatures ranged from 71 degrees at Ainsworth to 85 degrees at Imperial. && .SHORT TERM /THROUGH MONDAY NIGHT/... Issued at 330 PM CDT Sun Jun 16 2024 This evening and tonight...Although it has been a fairly quiet Father`s Day under mostly clear skies, attention turns to the potential for isolated to scattered severe thunderstorms for two portions of the forecast area... 1) areas along and south of I-80 High temperatures have begun to rise into the 80s along and south of the aforementioned front across southwest Nebraska. Combined with increasing dew points into the upper 60s, nearing the low 70s for some locations, ample instability (MLCAPE 2,000 to 3,000+ J/kg) has set up across this area. Pre-convective low to mid-level lapse rates have steepened across this area (7.5 to 8.5+ C/km) with strong 0-6km Bulk Shear (of 40 to 50 kts) creating a rather robust environment supporting a threat for large hail, damaging winds, and perhaps an isolated tornado(es). The biggest question that remains is, will convection be able to initiate along this boundary given the strength of the CAP? Our special 20Z UA launch shows a strong CAP in place here at LBF. However, a subtle shortwave looks to progress northeastward in the mean flow aloft, combined with increased surface convergence along the front, could be enough to get robust multicells and perhaps marginal supercells to develop across southwest Nebraska. This is a highly conditional and somewhat low confidence, but a potentially high impact scenario. Will be monitoring for storm initiation between 4 and 7 PM CT. 2) areas along and north of I-80 As we head into tonight, a low level jet (LLJ) will start to strengthen and nose into the region. Upper-level forcing will strengthen as well with increasing frontogenetical forcing and isentropic lift in an easterly upslope flow regime. There continues to be a strong signal for robust elevated convection to develop across portions of the Sandhills into northern Nebraska, north of the front. This activity will grow upscale as storms move east/northeastward through the overnight hours into South Dakota, exiting across the Nebraska/South Dakota border by 09Z. Forecast soundings exhibit elevated instability with substantial MUCAPE (2,000 to 3,000 J/km). Large hail will be the primary concern with the elevated convection, though isolated damaging wind gusts cannot be rules out. Monday and Monday Night... The aforementioned stalled cold front will slowly lift northward as a warm front through the day on Monday. Instability will increase yet again as the low- level wind field amplifies Monday afternoon with strong winds of 30 to 40 miles per hour across southwest into central and north central Nebraska. Ample instability (MLCAPE 3,500+ J/km) and continued impressive 0-6km Bulk Shear (of 40 to 50 kts) sets up across much of the area, especially for areas along and east of Highway 83. The dry line should aid in overcoming the CAP late in the day with the potential of thunderstorms developing across the southern Panhandle and southwest Nebraska. These storms may grow upscale as they move east/northeast into Monday evening. Primary concerns will be large hail and damaging wind gusts. However, an isolated tornado(es) threat exists for areas along and north of Highway 20. Outside of the convective threat, daytime highs will warm into the 80s across northwest Nebraska to upper 90s across southwest Nebraska, some locations may near the 100 degree mark. && .LONG TERM /TUESDAY THROUGH SATURDAY/... Issued at 330 PM CDT Sun Jun 16 2024 Tuesday and Wednesday... The flow aloft at the start of the long term period will be defined by a high amplitude ridge across the eastern US and a trough across the western US. A cold front will advance across the area through the day on Tuesday, stalling just to our east, eventually building back into the region through midweek. This front will continue to provide focus for thunderstorm development Tuesday night into Wednesday. At this time it appears the strongest forcing and corridor of greatest instability will reside to the east of the forecast area. Though the severe risk appears limited for our area, will need to monitor the potential for heavy rainfall for portions of southwest and north central Nebraska Tuesday night into Wednesday. Precipitable water values appear to meet or exceed the 90th percentile during this time as highlighted by both the NAEFS and ENS ensemble guidance. This is supported by WPC`s Day 3 Excessive Rainfall Outlook (ERO) outlooking the previously mentioned areas under a Marginal to Slight Risk for Excessive Rainfall. Persistent cloud cover and precipitation will lead to a nice cool down with Tuesday`s highs in the 70s and 80s to the 60s on Wednesday. Thursday and beyond... The midweek cool down will be short-lived as temperatures warm back into the 80s as the upper-level ridge retrogrades westward into the weekend. Continued southwesterly flow aloft with additional northern stream disturbances tracking across the area will keep the extended forecast in an active pattern. While day-to-day predictability is low and the severe risk remains uncertain, recurring afternoon and evening thunderstorm chances will exist each day for the latter end of the week into the weekend. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1233 PM CDT Sun Jun 16 2024 VFR conditions are expected to prevail through early this evening at the KLBF and KVTN terminals. Thunderstorms may develop south and east of the KLBF terminal by 23Z. Have included a PROB30 until 03Z. Overnight, increasing low stratus will lead to MVFR/IFR CIGs across northern Nebraska, along with increasing showers and thunderstorms. Timing and placement of thunderstorms still remains somewhat uncertain, though prevailing -TSRA included at KVTN from 06Z until 11Z. Winds remain from the north and northeast with gusts to 20KT, before shifting easterly into this evening, at around 10 to 20kts. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Viken SHORT TERM...Viken LONG TERM...Viken AVIATION...Roberg