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FXUS63 KLBF 242345 AFDLBF

Area Forecast Discussion National Weather Service North Platte NE 645 PM CDT Wed Apr 24 2024

KEY MESSAGES

- Isolated to scattered thunderstorms for the panhandle and southwest Nebraska tonight into early tomorrow with a low severe threat

- Greater severe threat with storms beginning tomorrow afternoon and evening, continuing into the nighttime. Hail will be the main concern, although strong winds and a brief tornado are also possible.

- Widespread rain showers Friday through Sunday with potential for significant moisture totals of 1-2"

- Warmer and drier for first half of next week

SHORT TERM /THROUGH THURSDAY NIGHT/
Issued at 418 PM CDT Wed Apr 24 2024

This evening and tonight... Two areas will be the focus for thunderstorm potential. The first concerns ongoing convection along the Laramie Range which may survive its journey through the Nebraska panhandle this evening. Most short term high-res solutions suggest this activity to dwindle as it approaches the Hwy 61 corridor, but kept chc PoP. Severe threat appears limited as dew points hold near 40F and overall instability is weak. The second area will be toward the southern reaches of the CWA as a warm front develops in Kansas and a modest (~35kt) low level jet noses into the Sandhills. For this setup, the most likely timeframe will be after 09z. Instability appears to actually increase overnight as low level moisture advection increases, but shear backs off compared to earlier in the night despite the low level jet. With this activity likely being elevated in nature, hail will be the main concern. Parameters suggest it remaining sub-severe, however. Dry conditions and a steady southerly breeze will be the most probable scenario for a good chunk of the Sandhills or north central Nebraska. Used a general blend for the min temp forecast and bumped up a degree or two toward the upper end of the NBM envelope. Thinking the combination of increasing cloud cover, likely in the form of a stratus shield, and modest warm air advection will keep temps fairly mild. Guidance suggests 24 hr temp changes at H5 ending at 12z of 3- 4C across the CWA Forecast ranges from mid 40s panhandle to near 50F central.

Tomorrow into tomorrow night... Warm air advection slows, but moisture advection keeps up throughout the day, partly shown by surface dew points rising into the lower 50s. The main surface low deepens across eastern Colorado and the attendant warm front gradually lifts north across Kansas. Its northward progress will play a huge role in severe potential for our forecast area. At this time, guidance suggests it will bisect the GLD CWA by 00z, keeping Nebraska in the cool sector. In fact, the NBM envelope falls almost entirely in the 60s for highs for most of southwest into central Nebraska. A bit more sunshine in the northern panhandle may push locations toward 70F. The overrunning moisture and deep isentropic upglide should maintain the stratus deck during the day, which will hamper the best instability. While the greater low level forcing lies south of the area, mid-level lapse rates may be very steep over the Sandhills with some solutions showing 8-8.5 C/km. The strongest deep layer (as well as low level) shear also stay south of I-80. The vicinity of the surface low and front result in large helicity values along the NE/KS line, and with modest moisture profile and lower LCL's, agree with heightened tornado potential. If the front ends up drifting 50 miles farther north, think the tornado threat increases quite a bit for our CWA With the current info though, hedging toward an isolated or scattered storm threat for southwestern zones during daylight hours on the edge of the greater severe potential. Toward dark, the redevelopment of the low level jet and arrival of the upper low will greatly increase overall forcing. While surface features may still be concentrated to the south, abundant moisture and elevated features should fire off a number of storms in the Sandhills. Modest MUCAPE values around 1000 j/kg and continued steep mid level lapse rates, along with bulk shear up to 40 kts, will support some severe storms farther north.
Hail will be the main concern, although a few wind gusts may approach severe limits. The PoP forecast reflects the conditional storms in the south to begin the event and greater coverage and confidence overnight in the north.

LONG TERM /FRIDAY THROUGH WEDNESDAY/
Issued at 418 PM CDT Wed Apr 24 2024

Friday through Sunday... The upper low hangs right on top of the forecast area Friday, which will keep the rain potential going. Cool and moist northwest low level flow will lessen the severe threat, but a brief hail/wind concern exists for far north central Neb where southerly H85 flow still exists at 21z. A second upper low is quick on its heels, rounding the Four Corners on Saturday and reaching the Sandhills early Sunday. The second system appears to have a classic deformation band setup across the forecast area and be a winter storm should this occur a month earlier. Thermal profiles suggest rain, and moisture totals could be fairly impressive. When all is said and done, widespread 1" amounts appear likely and some spots could top 2" depending where the heavier storms roll through.
Temperature-wise, a steep gradient may set up across the area due to the rain core and the transitioning low level flow. Highs will range from 50s northwest to near 70F far southwest on Fri and Sat, then 40s and 60s for Sun.

Monday and beyond... Upper flow switches to quasi-zonal to start the week as the low kicks out of the Plains. Surface high pressure also gives way to a warm front pushing north through the Missouri Valley.
Additional precip chances appear limited, but temperatures moderate quite a bit with highs in the 70s likely. The warmer end of the NBM suggests 80s across the south toward midweek.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/
Issued at 642 PM CDT Wed Apr 24 2024

As humidity increases from the south, ceilings will lower late tonight and continue into Thursday. Expecting IFR conditions across much of the Sandhills southward through southwest and central Nebraska. MVFR expected across northern Nebraska. Winds will be gusty from the south-southeast, especially early this evening, then again during the day Thursday.

LBF WATCHES/WARNINGS/ADVISORIES
None.

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