Area Forecast Discussion
Issued by NWS Hastings, NE
Issued by NWS Hastings, NE
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321 FXUS63 KGID 141020 AFDGID Area Forecast Discussion National Weather Service Hastings NE 520 AM CDT Fri Jun 14 2024 .KEY MESSAGES... - While mainly spotty showers/sprinkles and probably a few probably non-severe storms will be possible during the day today, MUCH HIGHER chances for thunderstorms (some probably severe...especially west) will arrive later this evening- overnight in the form of a larger-scale complex. - Although of less certainty than tonight`s storm chances, most of our coverage area (CWA) is under a Marginal to Slight Risk (level 1-2 of 5) for severe storms again Saturday. This risk (IF it materializes) would appear to mainly favor our central/eastern counties and mainly 5 PM-Midnight (earlier than tonight`s round). - At least for now, we are calling for a brief break in rain chances centered on Sunday daytime, but thereafter, a parade of mostly-still-highly-uncertain, daily/nightly chances return to various parts of area, with the overall highest chances (PoPs) up to 50% currently focused Tues night- Wed. - Temperature-wise: confidence is high that especially today through Tuesday will feature above normal/average readings, with Sunday-Monday currently looking like the overall-hottest days with highs well into the 90s most areas and heat index readings near-to-slightly above 100 (but at least for now slightly short of our 105+ Advisory criteria). - Very warm LOW temps in the 70s most areas both Sun night and Mon night COULD at least approach record-warm values for June 17-18. - Temperature uncertainty really grows by Wed-Thurs, with our official forecast calling for a bit of a cool-down into the 70s-mid 80s, but some model data suggesting this is NOT a "sure thing" && .DISCUSSION... Issued at 519 AM CDT Fri Jun 14 2024 Quick "admin note" up front: It`s this forecaster`s first of several nights on, and from a "first impressions" perspective: 1) This is a "messy" upcoming weather pattern when it comes to the parade of rain/thunderstorm chances that currently litter every single day/night forecast period except Sunday daytime. More than usual, it is highly recommended to not try taking these chances/PoPs anything close to literally no more than 1-2 days in advance, especially as model 2) Although at least a slight cool-down is at least POSSIBLE by Wed-Thurs, at least slightly above normal heat will clearly be the other main story through the next several days...as we continue flipping the switch to "summer mode" after several weeks of overall-mild/temperature conditions that defined our spring/early summer season up until a few days ago. -- PRIMARY CHANGES TO THIS 7-DAY FORECAST PACKAGE VERSUS THE PREVIOUS ONE (issued Thurs afternoon): - Technically, the overall-biggest/most noticeable change was a low-confidence one, as high temps for Wednesday were brought down 5-8 degrees, now very tentatively aimed mid 70s-low 80s most places. -- 7-DAY FORECAST OVERVIEW/HIGHLIGHTS): - CURRENT/RECENT WEATHER SCENE AS OF 430 AM: Although it hasn`t quite arrived yet, an area of isolated to scattered rain showers and a few embedded thunderstorms look to be developing eastward into our far western zones over the next few hours, driven by subtle, somewhat "sneaky" mid level convergence likely rooted up in the 800-700 millibar layer. Out ahead of this incoming activity, skies have overall averaged mostly clear overnight most areas. In the big picture of the mid-upper levels, water vapor satellite imagery and short term model data confirm that our flow aloft is out of the west- northwest, as we reside north of an upper ridge axis centered over the Southern High Plains, and still well-downstream from a shortwave trough heading east across western AZ. At the surface, the cold front that tracked southward across our CWA yesterday and divided seasonably warm (north) from downright hot (south) has settled into southern KS. In the wake of this front, much drier air with dewpoints well down into the upper 40s-mid 50s range reside across our CWA, and low temps are on track to bottom out somewhere in the 60s most areas, but as cool as upper 50s far north, to as warm as around 70 far southeast. Early-AM breezes are generally 5-10 MPH out of the northeast. - TODAY-EARLY EVENING (through around sunset): While MOST areas will likely be dry MOST of the time, this is a a classic case where it is almost impossible to guarantee that is stays totally dry the entire time, as persistent mid-level theta-e advection will almost assuredly continue to spark generally northwest-southeast oriented bands or splotches of at least sprinkles/light showers, and probably a few embedded and largely weak thunderstorms (due to them being elevated above capped-off lower-level instability. As a result, have blanketed the entire CWA with at least a 20% shower/thunderstorm chance and/or sprinkle possibility through most of the day. High temps carry at least modest uncertainty, as at least a few degrees will depend on whether skies average more partly cloudy or perhaps trend more toward mostly cloudy with time. For now kept them similar to previous forecast with mid 80s most Neb zones, and upper 80s to around 90 more common near/south of the state line. Winds today will trend more southeasterly with time and become modestly-breezy...sustained 10-15+ MPH/gusts 15-25 MPH. - LATER THIS EVENING-OVERNIGHT: This has been long-advertised as one of our better rain chances in a while, and overall that still looks to be on track, but perhaps/probably at the expense of at least a limited severe storm threat. In short, upper forcing will be on the increase as the shortwave trough currently over AZ gradually ejects into the Central High Plains, while a southerly low level jet develops out ahead of it. The net result should be a fairly large-scale complex of storms (perhaps with a well-defined linear leading edge) that is expected to arrive in our western zones around 9-10 PM, reach central counties roughly Midnight, and then gradually vacate our eastern zones by roughly 4 AM. Severe- weather wise, this is not a "slam dunk" setup, as there is the potential that convection could "lose steam" as it tracks farther east into our area (for one thing deep layer shear is only modestly strong at 30-40KT). However, especially our western counties (where SPC has the Slight Risk focuses) could see a few-hours window of opportunity for 60-70 MPH wind gusts, with a lesser threat of hail probably only to around quarter size, and an even lesser threat (albeit non-zero) of a brief QLCS tornado if things come together just right. While localized higher/lower amounts are always probable with convection, official WPC QPF is calling for most of our CWA to pick up somewhere between 0.50-1.00", which is not expected to pose much of a flooding threat (beyond very short- term/localized) given that all of the sudden these last 6 days have suddenly been very dry (and hotter) across the vast majority of our CWA. Temp- wise, lows tonight aimed mid-upper 60s most areas. - SATURDAY-SAT NIGHT: Over the course of the daytime-evening hours, the larger scale upper trough will gradually track across the heart of the Central Plains. With this upper forcing in place, at least spotty showers/a few weak storms just cannot be ruled out through much of the day (although MOST places should be dry). The overall-biggest question mark and concern is: will at least a few strong to severe storms try flaring up mainly within our central/eastern zones at some point between 5 PM-Midnight? Higher-res models offer mixed messages on this, with the often- aggressive NAMNest more supportive of this possibility than the latest HRRR. At least from a conditional threat perspective though, cannot argue much with SPC assigning roughly the southeastern 2/3rds of our CWA a Slight Risk. In other departments Saturday, assuming that daytime convection is held to a relative minimum, it is expected to turn fairly breezy from the south (gusts at least 20-30 MPH), which would give temps a generally 2-5 degree boost over today, with highs aimed upper 80s-low 90s most Neb zones and low-mid 90s in KS. Once any possible storms vacate our eastern zones late Sat evening-overnight, it should be a dry early Sun AM with lows holding up mainly mid-upper 60s. - SUNDAY-SUN NIGHT: Officially, we have kept the daytime forecast block a dry one, which seems plausible given that warm mid level temps should "cap" us off pretty well, although the possible presence of a sharp, west-east surface front near our northern edges (up around Ord/Greeley) will bear watching. Otherwise, the main story will be another crank up in the heat, with another 3-5 degree boost in high temps with most areas well into the 90s (flirting with 100 especially KS). Heat index readings will be widespread upper 90s to as high as around 103 (especially in KS), but at least for now this would fall just short of Advisory criteria. Sunday evening-overnight, odds favor the majority of convection in our region remaining north of our CWA, but officially we have as high as 30-40% chances/PoPs returning to mainly our northern half. Overnight low temps are forecast to hold well up into the low-mid 70s most areas (placing possible June 17 records in jeopardy at Grand Island/Hastings). - MON-MON NIGHT: Under continued southwesterly flow aloft, odds strongly favor the vast majority of our CWA remaining dry under very warm mid- level temps. However, given strong heating and weak/subtle disturbances in the flow, at least spotty storms cannot be ruled out (especially in our north). However, barring a big change, this looks like a hot and fairly windy day (especially by June standards), with highs similar to Sunday (solidly 90s most areas), but with southerly gusts perhaps as high as 30-40 MPH as surface low pressure deepens to our west. At least spotty heat index of 100+ again possible, especially in KS. - TUES-THURS: Simply taking a brief overview of these last three days of our 7-day, the bottom line is that uncertainty starts growing (especially temperature-wise, and especially Wed-Thurs). If the latest ECMWF/GFS agree on anything, it`s that our next larger scale/synoptic cold front should sag southward into our region Tues night into Wednesday, promoting our next "best chance" rain/thunderstorm chances beyond the one tonight. Depending on frontal timing, Tuesday could be another rather hot day (currently depicted to be a few degrees cooler than Mon). Then, especially by early-summer standards, Wed and Thurs carry above- average temperature uncertainty, with some models/guidance as cool as 70s and others are warm as 90s. This will depend mainly on whether the front heads back north or stalls out over our area, and also to some degree how much convection/outflow is around. A whole lot yet to sort out in this time range. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 104 AM CDT Fri Jun 14 2024 For KGRI/KEAR Airports: - General overview: High confidence in VFR ceiling/visibility through the vast majority of the period, but with a good chance for a potentially large-scale (and possibly severe?) complex or line of thunderstorms arriving very late in the period Friday evening, things could trend sub-VFR very quickly. Speaking of rain/storms, there could be spotty/brief passing showers/weak thunderstorms perhaps as early as around 14Z, but these chances are far less of a "sure thing" than the aforementioned later ones. Aside from any gusty/erratic thunderstorm outflow, winds do not look to be a significant factor, with most of the period featuring an east-southeasterly direction, with especially afternoon gusts likely into the 20-25KT range. - Ceiling/visibility/rainfall/thunderstorm details: High confidence in VFR ceiling/visibility through the vast majority of the period, with any potential ceiling most likely at-or-above 8K ft. until late evening when a larger-scale line or complex of storms is expected to arrive from the west. Once this occurs, sub-VFR ceiling/visibility both could clearly come into play. As for shower/thunderstorm potential, honestly can only really "guarantee" dry weather these first 6-8 hours at most. As early as roughly 14Z, there are hints that at least spotty, high-based showers/weaker thunderstorms could develop overhead, and have hinted at this potential with a basic "vicinity shower" (VCSH) group 14-18Z. Between 18-03z, odds favor mainly dry conditions, but cannot rule out some continued spotty shower/weaker thunderstorm activity here and there. Finally, very late in the period (mainly after 03Z KEAR/04Z KGRI), latest higher-res models are increasingly-suggestive of a larger scale complex/line of storms arriving from the west. Given this activity is out toward the end of this TAF period, will only introduce a generic "vicinity thunderstorm" (VCTS) for now, but this activity could easily produce at least small hail, heavy rain and wind gusts into the 30-50KT range depending on how it evolves. - Winds: Aside from any possible much stronger/erratic direction winds caused by thunderstorms mainly late in the period, winds should not be a significant issue. The lightest winds of the period are right away early this morning (under 10KT out of the northeast), but a steadier east-southeast wind will pick up during the day, with especially this afternoon featuring sustained speeds around 15KT/gusts 20-25KT. && .GID WATCHES/WARNINGS/ADVISORIES... NE...None. KS...None. && $$ DISCUSSION...Pfannkuch AVIATION...Pfannkuch