Area Forecast Discussion
Issued by NWS North Platte, NE
Issued by NWS North Platte, NE
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388 FXUS63 KLBF 102332 AFDLBF Area Forecast Discussion National Weather Service North Platte NE 632 PM CDT Mon Jun 10 2024 .KEY MESSAGES... - Strong to severe thunderstorms are again possible Monday afternoon and evening, mainly for areas west of Highway 83, with large hail and damaging winds the main concerns. - Temperatures will climb towards the middle of the week with forecast highs in the middle to upper 90s for much of southwest Nebraska, increasing heat concerns. - Temperatures cool towards late week into the weekend with continued rain and thunderstorm chances, peaking Friday afternoon and evening. && .SHORT TERM /THROUGH TONIGHT/... Issued at 258 PM CDT Mon Jun 10 2024 Conditions have remained dry during the day today as the area remains under the influence of high pressure which sits just east of the local area. As this feature continues to shift into the Mississippi Valley, southerly flow will increase across the High Plains. At the same time, a more pronounced shortwave tracking just north of the Canadian border will bring modest height falls into the area as a surface cool front trails the main low and approaches from the northwest. Ahead of this feature, dew points have climbed into the mid to upper 50s. Steep mid-level lapse rates continue to overspread the area, promoting moderate to strong instability denoted by MLCAPE values in the 1500-2500 j/kg range. Shear is adequate with h5 flow immediately behind the front of 30 to 40 knots Combined with low-level southerly to southeasterly flow and 0-6km BWD values range from 25 to 35 knots in closer proximity to greatest low-level forcing along the boundary. Thunderstorms are already ongoing across the far western Nebraska Panhandle and will gradually shift east this afternoon and evening into the local area. Storms initially will favor discrete modes capable of large hail and damaging wind gusts but as they congeal with eastward progression, expecting the threat to largely transition to damaging winds. PoPs ramp up markedly after 21z (4pm CDT) and peak around the 6-11pm CDT window with values as high as 80%, or Definite categorical, across the Sandhills. A heavy lean on HRRR/HREF/NAM Nest guidance was used to come up with the timing and progression of these. Given fairly appreciable PWATs, can`t rule out some locally heavy rainfall. Latest QPF values generally range from 0.25" to 0.75" with locally higher amounts possible. This, in general, matches latest HREF output though HREF ensemble max values suggest values as high as 1- 2". Believe quick progression, rapid decrease in intensity, and topography of Sandhills should preclude any Flooding concerns with this activity. Regarding this rapid decrease in intensity...storms will continue to track east into central Nebraska but are largely expected to outrun the greatest instability. Latest SPC Mesoanalysis guidance shows a rapid decrease from west to east with most locations along and east of Highway 83 showing less than 500 j/kg of MUCAPE. This should hasten the weakening after 10pm CDT tonight with no severe weather anticipated thereafter though lingering rain and general thunderstorms should persist through the overnight before exiting to the east prior to dawn Tuesday. Lows tonight should fall into the low 50s west to near 60 degF east. && .LONG TERM /TUESDAY THROUGH MONDAY/... Issued at 258 PM CDT Mon Jun 10 2024 Tuesday...modest high pressure will shuffle through the area which will help promote dry conditions. Winds will be light and variable through the day, becoming more southerly by late afternoon. Temperatures at h85 will actually increase from Monday to Tuesday and with deeper mixing expected, forecast highs will add 2 to 5 degF for all locations from Monday`s values. Forecast highs will settle in the 80s for all and even some upper 80s for far southwest and north central Nebraska. Quasi-zonal flow will settle in behind departing trough with the main h5 ridge beginning to shift east out of the Great Basin. Subsidence aloft and increasing mid-level temperatures should squash any precipitation chances for the day and evening even with a surface boundary stalled in the area. This focus should remain south though of the area. Wednesday...the hottest day of the week and focus of increasing concern for heat issues. Low amplitude ridging continues to drift east across the US/Mexico border with ridge axis focusing across the Central Rockies for Wednesday and the High Plains by late Thursday. The associated thermal ridge will gradually spread west out of the Great Basin with h85 temperatures climbing above the 90th percentile by Wednesday morning and peaking around the 99th percentile by early Thursday. A northern stream trough rounding the top of the mid-level high pressure will propel a surface trough into the area. Ahead of this, increasing southerly will propel a warm front north into east central South Dakota. Broad WAA in the open warm sector will promote rapid moistening in the low-levels. As daytime temperatures rise, convective temperatures look to be breached by late afternoon which would open the door for rain and thunderstorm development. What is more lacking in the immediate area is a focus. The lack of any appreciable surface convergence due to veered low-level winds or forcing aloft casts considerable doubt on seeing the development of any convection. Similarly minded, the NBM shows near negligible probabilities for precipitation with only 20-30% chances of seeing measurable rain for the day across far north central Nebraska. The latest SPC Day 3 Outlook covers much of the area east of Highway 83 in a Marginal Risk (level 1 of 5) with a Slight Risk (level 2 of 5) just encroaching in far eastern Boyd County. Believe a gradual downtrend in Risk Categories is warranted should the going forecast persist over the next day or two. The notable southwesterly flow should support fairly deep mixing as forecast soundings show potential for boundary layer depths to top 2-3km. This supports the hot temperatures in the latest forecast with mid to upper 90s prevalent for all areas with the exception of the western Sandhills. Fortunately, the core of greatest surface moisture remains east of the area, thus heat index values appear likely to fall short of advisory criteria (100 degF). Even so, WBGT values will climb into the Elevated to Moderate criteria with the latest Heat Risk guidance reaching levels 2 and 3. This suggests concern for folks with outdoor plans. The expected temperatures under mostly sunny skies will be hazardous to folks if adequate precaution is not taken. Thursday...similar to Wednesday, another hot day is likely for mainly southwest Nebraska. Weak low pressure will drift through the area in the early morning hours. This will promote increasing northerly flow immediately following this feature which will drive a cool front south into far southwest Nebraska up through northeast Nebraska. With the thermal ridge still in place, modest mixing is all that`s needed to tap in the anomalous temperatures off the surface. In the post frontal air mass, cold air advection will settle in but the overlap of strongest winds on the forward edge of CAA and the 28+ degC h85 temperatures will be the area to expect heat concerns yet again. This favors far southwest Nebraska, mainly south of Highway 23, where afternoon highs will again climb into the middle 90s. Heat concerns continue with heat index values climbing into the upper 90s, Wet Bulb Globe Temp values reaching the Elevated to Moderate levels, and Heat Risk values of 2. Though not as severe as Wednesday, caution is again advised for folks spending time outdoors. Further north across the area, CAA will abate the heat with many locations returning back to the 80s. Late afternoon and evening thunderstorm chances will return in close proximity to the surface boundary expected to settle south of the immediate area. Ensemble guidance remains fairly pessimistic with output showing low probabilities but various deterministic solutions showing increased potential. Will maintain the inherited Chance PoPs (< 30%) for now. Friday and Saturday...the next notable chance for rain and thunderstorms will arrive later in the day Friday. Ridge breakdown will occur late in the day as a stronger shortwave tracks out of the central Rockies. NBM PoPs paint a steady increase through the day, peaking in the evening in the Likely (55-65%) category. A closer look shows PoPs favoring the late afternoon through the early morning hours Saturday based on 50th Percentile output and various deterministic solutions. QPF amounts appear to be notable, with both the EPS and GEFS solutions showing 50-70% probabilities of seeing > 0.10" and 20-40% probabilities of seeing > 0.50". The threat for severe will need to be monitored but the overall pattern setup suggests at least an isolated threat with a narrow plume of moderate instability and h5 flow approaching 30 to 40 knots. Highs on Friday will reach the low to mid 80s, increasing to the mid to upper 80s for Saturday. Sunday and beyond...continued modest southwesterly flow will promote fairly active weather continuing in the extended period. Variations in precise evolution of the extended period casts some doubt, but the overall pattern will favor warm temperatures and recurring chances for precipitation. A strong northern stream system will track east out of the Pacific Northwest, dragging a cool front south into the area sometime early next week. The latest Climate Prediction Center Outlook favors continued above normal temperatures likely due to southeastern ridging. At the same time, the latest 6- 10 Day outlook shows above normal precipitation favored as well which supports the daily low-end PoPs for Days 6 and 7. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 632 PM CDT Mon Jun 10 2024 VFR conditions are expected to prevail across western and north central Nebraska through tomorrow evening. The primary aviation concern will be the line of showers and thunderstorms currently across the Panhandle that will move east this evening. The main concern is strong, gusty, and erratic winds around the thunderstorms. Storms may also bring some temporary MVFR conditions, which are covered by the TEMPO groups at both terminals. After the storms pass, winds are expected to be light and variable with skies clearing out. && .CLIMATE... Issued at 258 PM CDT Mon Jun 10 2024 Record Highs for LBF CWA Climate Sites: Wed 06/12 Thu 06/13 Fri 06/14 North Platte 102 (1952) 108 (2022) 101 (1952) Valentine 104 (1952) 103 (1956) 105 (1979) Broken Bow 101 (1952) 103 (2022) 101 (1952) Imperial 104 (1952) 106 (2022) 108 (2006) At this time, no records are projected to be broken. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...NMJ LONG TERM...NMJ AVIATION...Richie CLIMATE...NMJ