Area Forecast Discussion
Issued by NWS Hastings, NE
Issued by NWS Hastings, NE
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762 FXUS63 KGID 172131 AFDGID Area Forecast Discussion National Weather Service Hastings NE 431 PM CDT Tue Sep 17 2024 .KEY MESSAGES... - Chances for showers/storms spread across the entire forecast area tonight (60-70 percent). Potential for some strong to marginally severe storms remains in place late this evening into the early overnight hours...mainly for areas along/west of Highway 183. Wind gusts near 60 MPH would be the main threat. - After a dry Thursday, precipitation chance ramp back up for Friday on through early next week. At this time, the best overall chances look to be Friday night through Sunday night, with area-wide 50-60 percent chances at various points thorugh this period. Potential is there for a decent chunk of the area to pick up at least one inch of rain...however there are still several days to see how models trend and iron out the details. - High temperatures in the 80s remain through Friday, with a downward trend following. The overall-coolest day is currently Sunday, as the main upper low passes through...with 60s-70s for Saturday, Monday, and Tuesday. && .DISCUSSION... Issued at 425 PM CDT Tue Sep 17 2024 Currently through tonight... Fairly uniform conditions remain in place across the forecast area this afternoon, with gusty southerly winds and mostly clear skies. Looking aloft, upper air and satellite data show southwesterly flow in place across the region, driven primarily by a low pressure system working its way east near the UT/ID border. At the surface, the pressure gradient across the area has tightened as low pressure deepens along the central High Plains...with south-southeasterly winds gusting anywhere from 25-35 MPH (the higher gusts have been across the western half of the forecast area). No big surprises as far as temperatures go, with mid-afternoon readings for most spots in the mid-upper 80s. The rest of this afternoon, focus will be off to our west across the High Plains, where thunderstorms are expected to expand in coverage as energy from that upper level low swings northeast. Models showing that low continuing on a northeastward track through tonight...ending up around the MT/WY/ND/SD border area by sunrise Wednesday. Models have been pretty consistent showing a fairly solid line of storms moving into western NE/KS later this afternoon/evening, with the big question being how well do things hold together as it approaches our forecast area. Our forecast here remains dry through at least the early evening hours, did slow down the onset of preciptiation chances for our area a few hours from the previous forecast...with hi-res models having been pretty consistent showing it being closer to 03-04Z before activity moves into our western edge. The better parameters for strong/severe storms... instability, deeper layer shear, and aid via daytime heating... remain mainly focused to our west, but can`t totally rule out some of those storms moving to western areas being a problem. SPC Day 1 outlook keeps the Marginal Risk area over areas along/west of Highway 183...the main concern being with straight-line winds. The further east things push, models show that line potentially not being as solid, but kept preciptiation chances pretty high area-wide in that 06-12Z time frame (60-70 percent)...the overall threat for severe weather is expected to wane. Precipitation chances diminish from west to east as we get closer to 12Z, western areas may be totally dry by that time. Wednesday and Thursday... Can`t rule out some lingering activity across eastern portions of the forecast area to start the day on Wednesday...but coverage should diminish with time. Have chances (anywhere from 20-40 percent) lingering through the first half the day for areas along/east of Highway 281...but confidence in the exact timing of precip ending is not high. In the upper levels, we continue to sit under southwesterly flow...the main low driving activity through tonight doesn`t look to make a lot of progress during the day on Wednesday, with models showing it only to have made it into the northern MT/ND border area by early evening. Thinking there will be at least a brief lull in activity...with the potential for at least isolated- scattered thunderstorms developing mid-late afternoon. Some uncertainty remains with exact location of sfc/lower-level boundaries that this activity would be focused on...models show a surface dry line pushing east across the area during the day, but there could also be a boundary left from tonight`s activity/outflow meandering around. Overall upper level lift is on the weaker side, with the main low being well north of the area...looking to help keep things more scattered in nature. At this point, the better chances for these storms looks to be across eastern portions of the forecast area...along/east of HWY 281/into north central KS...but a few models show some isolated activity a touch further west than that is not out of the question. Models showing the potential for MLCAPE values near/exceeding 1500 j/kg across portions of the area...with deeper layer shear generally around 30 kts. Potential for some of this activity to be strong-severe remains, and central/eastern portions of the forecast area are included in the SPC Day 2 Marginal Risk area. Because activity is not expected to be widespread, precip chances remain in the 20-30 percent range. Otherwise, generally partly cloudy skies are expected, with afternoon highs forecast to again reach into the mid-upper 80s. Models are in pretty good agreement keeping the best chances in the 00-06Z time frame, and current forecast has the rest of the overnight hours dry. That dry forecast remains in place as we get into Thursday and Thursday night...with models showing the area set up under upper level shortwave ridging, between one low continuing its northeastward trek into central Canada and another digging into central/southern CA. Forecast calls for mostly sunny skies through the day, with mainly northwesterly winds on the lighter side, around 10-15 MPH...and another day with highs in the mid-upper 80s for most locations. Friday on into early next week... For the latter half of this forecast period, primary focus is on that upper level low over the western CONUS and the more widespread precipitation chances it is currently expected to bring. Looking at late Thursday night into the day on Friday, models are in generally good agreement in the big picture...showing the upper low shifting through southern CA toward the NV/AZ border area. Over the past few days, overall the forecast has trended drier due to the lack of better upper level lift being outside of the area...but do continue to have some small chances (20-30 percent) in the forecast...but if models continue on that trend, could see those chances lowered. Friday night, lift is increasing across the area, and could see a lead shortwave disturbance ejected out ahead of the main upper low (which moves into the Four Corners region). Precipitation chances increase into the 50-60 percent range area- wide late Friday night into Saturday. Plenty of uncertainties remain in this portion of the forecast...with one being how the rest of Saturday evolves. At this point, preciptiation chances are broad in nature through the day and remain elevated (40-60 percent)...but there will be a period in there where the area could be between bouts of better lift, sitting behind the shortwave disturbance driving the increasing chances Friday night continue to move east...and ahead of the arrival of the main upper low itself. Models show the upper low sliding through the Central Plains Saturday night into Sunday...with some differences whether there is any weakening as it does so (which could taper back how much accumulation there is). With it still several days away yet, hard to argue with the broad nature of chances from the NBM...it will be interesting to see how models trend in the coming days. By the time the end of the weekend arrives...there is the potential for a widespread appreciable rain across the area...latest EPS and GFS ensemble runs show 50-70 percent probabilities of an inch or more of rain over a decent-sized chunk of our south central NE counties, though vary on where it`s centered. Not totally out of the question given the convective nature potential that there could be spots with a couple of inches of rain...will just have to see how things trend. Have some low chances (20-30 percent) of precipitation continuing on into the Monday-Tuesday time frame...but confidence in those chances that far out are really low at this point. As far as temperatures go...currently have highs on Friday again in the 80s, as the area sits out well ahead of the main system and best preciptiation chances, with the rest of the period cooling off. Have mainly mid-upper 70s for Saturday, with the overall coolest day currently on Sunday, as that is the day expected to have the main upper low passing through. Monday and Tuesday currently sit in the mid 60s to mid 70s. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1237 PM CDT Tue Sep 17 2024 For KGRI/KEAR Airports: For the rest of this afternoon, expecting little in the way of cloud cover, and continued gusty southerly winds. Gusts around 30-35 MPH are not out of the question this afternoon. Winds diminish a touch this evening, but remain gusty out of the SSE. Main concern turns to mid-later evening into the overnight hours, as a line of showers/storms passes from west to east across the forecast area. At this time, the timing for the best chances at the terminal areas is roughly in the 06-10Z time frame...will be able to better refine that as activity develops out west and moves east early this evening. Kept a VCSH mention going through the early morning hours...confidence in just how much activity lingers is not high at this point...with the rest of this period expected to be dry. Kept this period VFR, but if sub-VFR conditions were to develop, it`d likely be in that time frame when precipitation is moving through/just after...confidence not high to drop it below VFR at this point. Gusty southerly winds look to redevelop mid-late morning tomorrow. && .GID WATCHES/WARNINGS/ADVISORIES... NE...None. KS...None. && $$ DISCUSSION...ADP AVIATION...ADP