Area Forecast Discussion
Issued by NWS North Platte, NE
Issued by NWS North Platte, NE
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157 FXUS63 KLBF 182332 AFDLBF Area Forecast Discussion National Weather Service North Platte NE 632 PM CDT Sat May 18 2024 .KEY MESSAGES... - An active weather pattern brings a variety of impacts, including severe weather and heavy rainfall Sunday through Tuesday. - A limited threat for late season frost, but cannot rule out a localized threat following a cool down mid week. - The pattern remains active through the week, brining the potential for precipitation nearly every day. Confidence on daily precipitation chances remains relatively low, due to uncertainty in exactly how the upper level pattern evolves. && .SYNOPSIS... Issued at 235 PM CDT Sat May 18 2024 Upper air analysis and satellite imagery this morning reveal an upper level low over north central North Dakota, and a developing shortwave over western Washington. At the surface, a low pressure system is located over Winnipeg, Manitoba this morning, with a cold front extending south through north central Kansas. High pressure is observed over the Nebraska Panhandle. && .SHORT TERM /THROUGH SUNDAY NIGHT/... Issued at 235 PM CDT Sat May 18 2024 Tonight, the stage becomes set for several days of active weather. As surface high pressure ejects to the east, a weak surface boundary may be the focus for some showers and thunderstorms this evening through Sunday morning, particularly across southwest Nebraska. As the nocturnal low level jet settles in, a plume of warm, moist air advects into the region. While this is happening, a low pressure system over Wyoming is expected to form and mature, developing a warm front and cold front before it heads east. The main forecast challenge in the short term will be how long these showers and thunderstorms linger, which sets up two main scenarios for Sunday evening. If the storms exit the region more quickly, as seen in HRRR guidance, there is a greater period of daytime heating, and as such a greater severe weather threat Sunday afternoon and evening. These solutions are presenting decent surface based CAPE and generally initiate storms along a line through most of the region. On the other hand, there is some slower guidance such as the NAM Nest, which holds the cloud cover from showers and storms a bit longer, limiting the daytime heating. These slower solutions limit the surface based CAPE, keeping storms more elevated in nature, and in some cases wipes the thunderstorm threat out by tomorrow evening. What does remain consistent is the plume of moisture ahead of the approaching system. Additionally, forecast soundings all tend to show a potential severe weather environment tomorrow evening, with ample CAPE and shear profiles. If the daytime heating can erode the capping layer, and storms can tap into the surface based layer, the environment seems primed to produce large hail and damaging winds. If the cap remains in place, then convection likely remains elevated, still with large hail potential, but may end up being hindered unless it can tap into the surface moisture. && .LONG TERM /MONDAY THROUGH SATURDAY/... Issued at 235 PM CDT Sat May 18 2024 Showers and thunderstorms Sunday night begin to taper off after midnight, giving a brief dry period on Monday morning. By the afternoon, another batch of showers and thunderstorms develops to the west and begins to track across the forecast area. Overnight Monday into Tuesday continues to be highlighted as the peak intensity of this precipitation event. Current guidance suggests that forecast precipitable water values will exceed the climatological 90th percentile. To further back this, ensemble guidance is now highlighting portions of north central Nebraska and the Sandhills with a 60 percent chance of exceeding 1 inch of rain in 24 hours. As for expected amounts, followed with the Weather Prediction Center guidance which calls for storm total rainfall around 1 to 3 inches across the region from tonight through early Wednesday morning. Currently, the highest amounts are expected across the Sandhills, but with the convective nature of the rain, locally higher amounts are possible. The next concern comes with a mid week cool off Wednesday morning. The latest forecast sees temperatures trending up slightly, however some of the lower end guidance brings mid to lower 30s across southern portions of the Panhandle. Will continue to keep an eye on temperature trends over the next several days, as temperatures in the mid to lower 30s could cause some late season frost concerns across the southern Panhandle. At this time, the chances seem somewhat limited, but again, will be worth keeping a close eye on. Mid week through the end of the week, the upper level pattern remains fairly active. A series of shortwave and upper level lows persist across the Northern Plains, with variations in the placement of surface systems and associated rainfall. Precipitation chances remain through the end of the week, however, it is a bit difficult to nail down a precise timing right now. Certainly, the synoptic forcing will be there, so it will also be worth keeping an eye on how the upper level pattern evolves over the next several days to more precisely time precipitation chances through the week. For now, will continue to stick with general chances of showers and thunderstorms through the week, however, follow on forecasts may be able to refine the timing as models resolve the pattern later this week. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 625 PM CDT Sat May 18 2024 VFR conditions will continue through the overnight period, though clouds will begin to fill in and lower as rain showers develop Sunday morning. MVFR to locally IFR ceilings are likely for southern terminals after sunset, impacting KLBF. Winds will strengthen out of the south with gusts exceeding 25 knots. Clouds will begin to scatter out towards the end of the valid period. Confidence on timing and specific impacts from the rain showers is rather low at this time, thus future amendments and inclusions will be possible. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Richie SHORT TERM...Richie LONG TERM...Richie AVIATION...Viken