Area Forecast Discussion
Issued by NWS North Platte, NE
Issued by NWS North Platte, NE
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524 FXUS63 KLBF 212311 AFDLBF Area Forecast Discussion National Weather Service North Platte NE 611 PM CDT Sat Sep 21 2024 .KEY MESSAGES... - Threat for precipitation Tonight into Sunday continues to shift south. - Potential for patchy frost Monday morning across portions of southwestern Nebraska and the Sandhills. - Dry conditions expected after Tuesday morning next week with above normal temps. && .SYNOPSIS... Issued at 316 PM CDT Sat Sep 21 2024 H5 analysis this morning had a fairly active pattern across the CONUS. Closed low pressure was located over western Arizona with a trough extending south into the Gulf of California. East of this feature, high pressure was anchored over south Texas. Further north, a trough of low pressure extended from east central Saskatchewan, south into North Dakota. One last feature of note was the persistent area of low pressure off of Cape Cod Massachusetts. A strong cold front blew through the forecast area earlier this morning. This has led to gusty northerly winds across western and north central Nebraska this afternoon. Northerly wind gusts as high as 40 MPH were reported at Imperial. Skies were mainly clear over north central Nebraska with partly to mostly cloudy skies central to southwestern Nebraska. Temperatures as of 2 PM CT ranged from 62 degrees at Gordon to 73 degrees at Imperial. && .SHORT TERM /THROUGH MONDAY/... Issued at 316 PM CDT Sat Sep 21 2024 The main forecast challenges continue to be precipitation chances tonight into Sunday morning, then the threat for frost Sunday night into Monday morning. For tonight, the upper level will emerge from the Four Corners into central Colorado by 12z Sunday. A broad shield of precipitation will develop from eastern Colorado into Kansas and far southern Nebraska. This precipitation will be most pronounced along and north of the surface cold front, which will reside along a line from the northern Texas Panhandle into SE Nebraska by 00z Sunday. Further north, the precipitation picture becomes more problematic. Already overnight, the latest NBM probabilities for >0.01 inches of precipitation have trended further south. Overnight, there is now less than a 50% probability of measurable pcpn, north of interstate 80. By the time you reach highway 92, that probability falls off to under 20 percent. The latest EC ensemble QPF probabilities for >0.01" are very similar to the NBM forecast having less than a 50 percent chance of measurable pcpn north of I-80 and less than 25 percent north of highway 92. This is also supported by the latest GFS and NAM12 isentropic fields at the 305thete level, which have the greatest lift generally along and south of highway 23 from Grant to Wellfleet. That being said, have lowered pops further in the central forecast area, and tightened up the northern gradient of pops. For example, across Lincoln county, we go from a 20 pop in the northern third of the county, to around 50 to 60 percent on the southern fringes of the county. As for QPF`s, they continue to trend downward with the latest deterministic solns (HRRR and 3KM NAM) which has roughly a quarter inch across the southern tier of counties, falling to near zero around I-80. Isentropic lift will exit the forecast area during the late morning/early afternoon hours Sunday, ending the precipitation threat over the southern quarter of the forecast area. Even with precipitation exiting the area midday, cloud cover will persist across the southern third of the forecast area, limiting highs. I did trend temps up slightly from the inherited forecast based on a more southerly track of precipitation and additional expected clearing across central portions of the forecast area. Highs Sunday will range from the upper 50s in the far south, to the upper 60s over northern Nebraska. Skies will begin to clear out Sunday evening. High pressure will build into southwestern Nebraska Sunday evening, transitioning into northwestern Kansas overnight. As for lows Sunday night, based on the shift in high pressure to the south, the coldest temps should be in the Platte River valley and portions of southwestern into central Nebraska. This is a shift from the previous forecast which favored the coldest temps in the western Sandhills. In these areas, light southerly winds will develop overnight on the northwestern periphery of the high. No surprise, low temps in the western Sandhills have trended slightly upward with the latest statistical guidance. Why is this important? Forecasted lows reach into the middle 30s Monday morning in the Platte River valley and portions of SW Nebraska. This may facilitate the first frost of the fall season. With better than a 50 percent probability of lows < 36F over portions of SW Nebraska and portions of the western Sandhills. Will be adding a mention of patchy frost to the grids. As for a frost headline product, will forgo this for now as forecast confidence in areas of frost coverage isn`t quite there yet. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Issued at 316 PM CDT Sat Sep 21 2024 A weak upper level disturbance will dive south from the Dakotas into Nebraska Monday night. This may lead to a small threat for precipitation in western portions of the forecast area. The inherited forecast as well as the new NBM does have some < 20% pops in the west and far southwest Monday night. This new NBM soln has trended farther southwest and lower with its new forecast. Looking at the latest probabilistic forecast from the ECMWF, wouldn`t be surprised if pops were eliminated from the forecast with the next NBM run. Beyond Monday night, a dry forecast is favored as a cutoff low develops over the southern plains and high pressure builds into the central and northern plains. Temperatures will trend back to near normal midweek with above normal temperatures expected thereafter. The latest NBM forecast has upper 70s to lower 80s for Wednesday through Saturday, which is on the order of 5 to 10 degrees above normal for this time of year. Lows will generally be in the upper 40s to lower 50s which is slightly above normal for this time of year. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 615 PM CDT Sat Sep 21 2024 VFR conditions are expected to prevail through tomorrow evening across western and north central Nebraska. An approaching system will lead to lowering CIGs for southwest Nebraska terminals, though look to remain well into VFR. Scattered precipitation is possible for terminals south of I-80, though this should remain light enough to keep visbys VFR as well. Gusty north winds subside just after sunset, and remain around 5 to 15kts from the north into tomorrow afternoon. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Buttler SHORT TERM...Buttler LONG TERM...Buttler AVIATION...Brown