Area Forecast Discussion
Issued by NWS North Platte, NE
Issued by NWS North Platte, NE
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473 FXUS63 KLBF 202019 AFDLBF Area Forecast Discussion National Weather Service North Platte NE 319 PM CDT Fri Sep 20 2024 .KEY MESSAGES... - Cold front will bring cooler temps to the area beginning Saturday. - Decent threat for precipitation across southern portions of the forecast area Saturday afternoon into Saturday night. - Cooler temps will persist into next week with possible frost potential Monday morning in the western Sandhills. - Mainly dry conditions expected next week with near seasonal temps. && .SYNOPSIS... Issued at 319 PM CDT Fri Sep 20 2024 H5 analysis this morning had high pressure anchored over south central Texas. A ridge extended north into southern Nebraska. Further west, a closed low was located over Los Angeles while over New England, a second low was located off the coast of Maine. Further north, a broad trough of low pressure was noted over western Canada. Within this trough, a couple strong shortwave troughs were noted. The first over eastern British Columbia and a second over northeastern Manitoba. At the surface this afternoon...Low pressure was located over southeastern Saskatchewan. A surface trough extended to the south of this feature into far western North Dakota. A second surface trough was present over northwestern Nebraska into northeastern Colorado. Along and west of this surface trough, winds were from the west and were on the order of 10 to 15 MPH. East of the trough, winds were southerly and southwesterly and were gusting up to 35 MPH at Valentine and 25 MPH at North Platte. Current RH over northwestern Nebraska was around 20 percent attm, however winds were fairly light at Gordon and Alliance. Further east at Valentine and Ainsworth, RH was in the 20 to 25 percent range as of 2 PM CT. Given the wind speeds in these areas, near critical fire weather conditions were present. If dew points in these areas hold in the lower 40s, and believe this will continue, we would have to see air temps in the mid to upper 90s for critical RH values. ATTM, believe strongly, the current temps will be the high for today in the before mentioned areas. Elsewhere, temps were generally in the middle to upper 80s under mostly clear skies. && .SHORT TERM /THROUGH SATURDAY NIGHT/... Issued at 319 PM CDT Fri Sep 20 2024 In the short term, precipitation chances Saturday night into Sunday morning is the main forecast challenge. The shortwave trough over eastern British Columbia, will migrate east into Saskatchewan tonight. This will force a cold front into northwestern Nebraska overnight-clearing the forecast area by mid morning Saturday. The inherited forecast had an abundance of precipitation chances beginning as early as Saturday morning, continuing into the afternoon hours on Saturday. This is not supported by the latest NBM ensemble QPF guidance which has a near zero probability of QPF>0.01" across the area through 7 PM CT Saturday evening. Further support for a dry forecast Saturday lies with the latest deterministic NAM12 and GFS solns which demonstrate, little to no isentropic lift at the 310K layer through 00z Sunday. Lift for precipitation initially lies along the frontal boundary, which by Saturday afternoon is off to the south and east of the area. That being said, with the exception of a small area of slight chance pops hugging the eastern fringes of the forecast area, most location will see dry conditions Saturday. It will be much cooler however as highs will range from the upper 60s in the northwest, to the lower 70s in the eastern forecast area. On Saturday night, the upper level low will migrate from the Four Corners into eastern Colorado. Isentropic lift will begin to increase, most notably over the southern third of the forecast area Saturday night or along and south of Interstate 80. The NBM probabilistic forecast has a 75% chance of 0.01" of QPF for North Platte Saturday night. This continues to trend downward from the previous forecasts. If you look at a tenth of an inch the probability drops off to around 60 percent. With this in mind and looking at the latest deterministic NAM12 and GFS solns, will confine likely pops to areas south of a line from Chappell to Broken Bow. For areas north of this line, pops were trended downward quickly with the northern tier of counties now being dry. This was based on the probabilistic forecast, a sharp cutoff in isentropic lift and much drier air pushing into northern Nebraska from South Dakota ie. dew points in the 30s. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Issued at 319 PM CDT Fri Sep 20 2024 Weak isentropic lift will persist, roughly along a line from Ogallala to O`Neill during the day on Sunday, shifting into northeastern portions of the forecast area early evening. Low precipitation chances will persist on Sunday roughly along and south of this line. In addition, cloud cover combined with northeasterly winds, will make for a raw cool day across the area. Highs will struggle to get out of the middle 50s in the south with some lower 60s possible in the northern forecast area. Skies will begin to clear off Sunday night with drier air pushing into the forecast area from the north. this will lead to lows in the middle to upper 30s in the west, to lower 40s in the east. The latest probabilistic NBM forecast indicates a 30 percent chance of temps below 36F Monday morning across the western Sandhills. ATTM, would like to see a better than 50 percent chance before inserting a mention of frost in the forecast. FWIW, if we are forecasting areas of frost for Monday morning in subsequent forecasts and fore confidence increases, would probably issue frost headlines, given this would be ahead of the climatological normal. We have also seen unseasonably warm temps across the area over the past couple of weeks so sensitive vegetation remains susceptible to frost. A second shortwave and northern stream trough of low pressure will impact the area Monday night into Tuesday morning. This will bring an increased threat for showers to the west. Beyond Tuesday conditions will be dry with temperatures gradually warming back into the upper 70s to lower 80s by the end of next week. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1249 PM CDT Fri Sep 20 2024 VFR conditions will prevail across western and north central Nebraska through tonight. A cold front will cross the area late tonight and winds will switch to the north. Very gusty north to northeast winds are expected Saturday, with gusts exceeding 35 kts at times. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Buttler SHORT TERM...Buttler LONG TERM...Buttler AVIATION...Taylor