Area Forecast Discussion
Issued by NWS Hastings, NE
Issued by NWS Hastings, NE
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062 FXUS63 KGID 301227 AFDGID Area Forecast Discussion National Weather Service Hastings NE 727 AM CDT Thu May 30 2024 ...Aviation Update... .KEY MESSAGES... - More active pattern expected for the rest of the week and through early next week, though official forecast likely sounds worse/wetter than what reality will be for most. - Some of the thunderstorms may be strong to severe, at times, but there currently aren`t any strong indications for organized and/or widespread severe weather. - Rainfall amounts will be HIGHLY variable across the region, as is typical for the warm season. Reasonable high end amounts over the next 5 days (ensemble 90-95th percentile) are 3-5", which could lead to isolated hydro concerns if that pans out. - Temperatures will remain remarkably steady in the 70s-80s (highs) and 50s-60s (lows) for most of the next 7-10 days, though areas SW of the Tri-Cities may make a run into the low 90s at times Sun-Tue. && .DISCUSSION... Issued at 450 AM CDT Thu May 30 2024 Much more "messy", almost summer-like, upper pattern is forecast to settle in for the next several days with shower and thunderstorm chances for at least portions of the forecast area essentially a daily/nightly occurrence. The pattern won`t come with the summer-like heat, however. Today - Tonight: Convection has largely played out as expected over the past 9-12 hours and is indeed scattered and fairly weak currently. Several MCVs are evident in regional mosaic radar loops, and to some extent surface observations, which will "muddy the waters" for forecasting convective trends today. The most obvious MCV locally is currently just NW of Kearney, but additional MCVs are also noted in northern Neb. and central Kan. These will slowly shift E throughout the morning and continue to provide weak ascent for iso-scat new development within a generally uncapped, weak elevate CAPE environment. Shear is also weak through at least midday, so really not much of a severe risk this morning. Assuming some subsidence behind departing MCVs allows for at least a few hrs of mixed sunshine, should be able to develop some moderate instability (1000-1500 J/kg MLCAPE) immediately along and just ahead of the front by late aftn/early eve as low levels gradually moisten on continued Srly flow. SREF deep layer bulk shear increases to ~30kt this eve, but appears the strongest mid-level flow will remain well post-frontal. Nonetheless, this CAPE/shear parameter space will probably be adequate for marginally severe hail and wind. Capping is weak thanks to H7 temps of 8C or less, so would expect relatively early development along the sfc convergence zone from near Ord to Lexington around 20Z. Activity should move E and SE through the evening, probably still on a scattered basis through 03Z. Some uptick in coverage will be possible thereafter, either from MCVs moving off the high plains, or from increasing low level jet. This could keep the marginal severe threat going well into the overnight. PWATs are forecast to pool around 1.5" along the frontal zone this eve/overnight, so with complex storm mergers and/or slow effective forward motions, could have some locally heavy rainfall. General consensus of model data suggests areas along and S of the state line would be most at risk for isolated 2-4" of rain in short amount of time. Rainfall amounts, however, will be HIGHLY variable across the region with many areas staying mostly dry. This looks to be general idea each of the next several days - some see isolated heavy rain, many others miss out completely. Friday-Friday Night: Lingering showers and thunderstorms in the morning should gradually end/shift S-SE with the composite front/outflow through the daytime hours as upper support becomes increasingly meager. Can`t rule out an iso pop-up storm anytime in the aftn or eve thanks to uncapped moist BL, as evident by light and spurious QPF in various model output. Also, EC has been insistent that an MCS could clip areas SW of the Tri-Cities Fri night, though confidence on this is low given weak 850mb flow. Weekend: Rain chances continue through the entire weekend, but definitely don`t want to give the impression that either day is a washout. In fact, think most will stay dry through late aftn Sat as the main risk locally should come from scattered storms that develop in central Nebraska then move SE during the evening - perhaps in the form of one or two MCSs. Belt of stronger deep layer shear remains just off to the N, so think severe threat should be fairly similar to today and mostly of the marginal variety. Overnight convection should have more LLJ to work with. Kind of a wash, rinse, repeat for Sunday in terms of expecting timing and location of initial development. This round of activity could have more organization/intensity with it, though, given higher values of both instability and shear, as well as more coherent shortwave trough and possibly a front. Confidence in the higher CAPE/shear overlap occurring this far S is too low for a formal outlook from the SPC, but something to monitor for potential impacts to Sunday evening outdoor activities. Next week: Forecast confidence continues on the low side early week, at least in terms of shower/thunderstorm details on Monday, thanks to weak zonal flow and potential for one or more boundaries to linger in the region from previous rounds of convection. Ensembles have started to come into better agreement regarding a stronger shortwave trough moving through the central/northern Plains in the Tuesday-ish time frame - which would likely send at least a moderately strong cold front through the region and possibly bring an end to the frequent rain chances for a few days. Ahead of this front, some areas could make a run at the low 90s Sun-Tue, but otherwise much of the next 7-10 days look to be mainly mid 70s to 80s for high temperatures. Fairly seasonable for late May - early June. && .AVIATION /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 727 AM CDT Thu May 30 2024 - General overview for KGRI/KEAR: Although the majority of the period will likely feature VFR ceiling/visibility and rain/thunderstorm-free conditions, particularly the 23-06Z time frame (this evening) could feature at least brief (but perhaps strong to severe) thunderstorm potential, and particularly the 06-12Z time frame (early Fri AM) could bring sub-VFR ceiling and visibility in low clouds/light fog. Aside from any potential short-term gustiness/erratic direction shifts associated with thunderstorm activity, winds will not be a major issue, with even gusts topping out mainly no more than 15-20KT. - Ceiling/visibility/precipitation/thunderstorm details: Right out of the gate this morning, KGRI will have about another hour of passing rain shower potential, but for the most part, latest higher-res models are more suggestive that these first 10-12 hours will prevail dry/storm-free with any possible ceiling no lower than low-end VFR. The main time frame for possible, isolated to scattered thunderstorm activity appears to focus 23-06Z. Given inherent uncertainty in any finer details, have simply kept with generic "vicinity thunderstorm" (VCTS) for now, and defer any more refined TEMPO/prevailing groups to later issuances. There is an outside chance that KGRI/KEAR could see a severe storm during this time, with the main hazards being gusts to around 50KT and/or hail to around quarter size. Once convective potential largely ends by around 06Z, there are increasing chances for sub-VFR ceiling/visibility late in the period. Although it is possible that visibility could be as poor as IFR and ceiling as low as IFR/LIFR, opted to not go quite this pessimistic quite yet, and thus went with MVFR ceiling/visibility for now. - Wind details: Aside from any enhanced gustiness/erratic directional changes from thunderstorm activity (which would be most favored between 23-06Z), winds through the first half of the period today will mainly be 10-15KT/gusts 15-20KT out of the south-southeast. Then overnight into early Fri AM, directional will shift more northeasterly at speeds under 10KT. && .GID WATCHES/WARNINGS/ADVISORIES... NE...None. KS...None. && $$ DISCUSSION...Thies AVIATION...Pfannkuch