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Area Forecast Discussion
Issued by NWS North Platte, NE
Issued by NWS North Platte, NE
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666 FXUS63 KLBF 132035 AFDLBF Area Forecast Discussion National Weather Service North Platte NE 335 PM CDT Tue Aug 13 2024 .KEY MESSAGES... - A Slight Risk (Level 2 of 5) for severe weather across southwestern Nebraska this evening and tonight. Tonight`s primary severe threat will be severe wind gusts and locally heavy rainfall. Storms this evening will have the capability of bringing over 1 inch of rain under the heavier downpours. - A Marginal Risk (Level 1 of 5) for all of western and north central Nebraska tomorrow afternoon for wind and hail. - The week continues on with near seasonal temperatures and near daily rain chances through the end of the week. && .SYNOPSIS... Issued at 331 PM CDT Tue Aug 13 2024 Upper level analysis and water vapor satellite imagery reveal a low amplitude ridge over western Nebraska, with an upper level disturbance in the flow. At the surface, a stationary front is observed along the Nebraska-Wyoming border. A few showers and thunderstorms are noted on satellite and radar across the western Nebraska Panhandle and northeastern Colorado. && .SHORT TERM /THROUGH WEDNESDAY NIGHT/... Issued at 331 PM CDT Tue Aug 13 2024 As storms develop this afternoon along the front, they will continue to trek to the east, eventually reaching western Nebraska. Better instability exists over northeast Colorado, where CAPE values this afternoon hover around 1000-1500 J/kg, expected to increase around 1500-2000 J/kg late this afternoon into the evening. The upper level flow remains relatively slow, with only around 25 kts at 500 mb. With the more marginal shear, a more multi-cellular mode is expected for convection this evening, with the greatest severe potential being damaging wind gusts, though some large hail cannot be ruled out. With the increasing confidence in more organized convection this evening, the Storm Prediction Center upgraded the Marginal Risk for today into a Slight Risk across portions of southwest Nebraska, generally along and south of Interstate 80. Interestingly, PWAT values across western Nebraska are around 1.5 inches, which puts it around our 50th to 75th percentile compared to climatology. However, the PWAT values have been increasing the past 24 hours, thanks to southeast flow pumping more moisture into the region. Latest model guidance has been picking up on the efficient rain processes, and multiple models have painted a stripe of higher QPF values across southwest Nebraska, with some solutions further north into the Sandhills. Although wind is the primary severe weather concern with storms this evening and overnight, will need to keep a close eye on the potential training nature of storms this evening. With the amount of available moisture, storms this evening could be quite efficient rain producers, with widespread precipitation coverage across southwest Nebraska ranging from .5 inches to 1 inch. However, if the storms train, would not be surprised to see locally higher amounts in excess of 2 inches. On the topic of moisture, after rain and storms clear out of the area early Wednesday morning, there is yet again a chance of patchy fog through the morning hours. With the recent rainfall, humidity values will be near 100 percent, with calm winds to boot. Currently unsure on how dense the fog may get, but will need to keep a close eye on visibilities overnight to see whether any fog headlines are required in the morning. As for Wednesday, a break in the cloud cover is expected late Wednesday morning, which will help with daytime heating. With all the recent moisture, and another shortwave in the upper level flow, another round of severe weather may be on deck. Guidance suggests the possibility of CAPE in excess of 2000 J/kg across central Nebraska, however, there is question on how far west this will extend. Again, upper level flow is not overly robust, with 500 mb winds around 30 kts. Forecast soundings appear supportive of large hail in stronger cells, and cannot rule out potential for severe wind gusts. As of now, the ingredients for more organized severe weather appear to be lining up over eastern Nebraska. However, as storms initiate over central and north central Nebraska, there may be a window for potentially severe thunderstorms tomorrow afternoon and evening. For now, the Storm Prediction Center has placed a Marginal Risk for severe weather across all of western and north central Nebraska for Wednesday. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Issued at 331 PM CDT Tue Aug 13 2024 An upper level low will attempt to flatten the low amplitude ridge over western Nebraska Wednesday afternoon, bringing more zonal flow on Wednesday night and Thursday, before another ridge is expected on Friday. A few shortwaves are expected to track through the upper level flow, and with those shortwaves, at least slight chances of showers and thunderstorms through the end of the week. At this time, the severe potential of any thunderstorms remains uncertain. By the weekend, precipitation chances are expected to drop below 20 percent, but will need to see how guidance handles the upper level flow. There were already deviations setting up in spaghetti plots by the weekend, so will need to keep an eye on model trends to see how these deviations resolve. Also of note, will be the return to seasonal temperatures, generally highs in the 80s, starting as early as Wednesday. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1227 PM CDT Tue Aug 13 2024 Areas of MVFR/IFR/local LIFR in low or very low ceilings across wrn Nebraska will gradually improve to MVFR by around 21z this afternoon. A return to IFR/LIFR in low/very low ceilings and vsbys is expected to commence around 03z this evening and last until 15z or later Wednesday morning. It`s worth noting an eastward moving cold front Wednesday morning will improve flight conditions from west to east. Aviators will also have to negotiate scattered to numerous thunderstorms from 01z this evening through 12z Wednesday morning, generally affecting areas along and south of highway 2. This flight concern is associated with a UA disturbance moving east northeast out of Colorado this afternoon. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Richie SHORT TERM...Richie LONG TERM...Richie AVIATION...CDC