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The Dexes / Heavy Rain / 477593

Eventdex · Heavy Rain

ADAMS

477593 · 40.580, -98.510

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Event typeevent_typeHeavy Rain
NOAA NCEI event IDncei_event_id477,593
Episode IDepisode_id79,571
Begin UTCbegin_utc2013-10-03T02:00:00+00:00
End UTCend_utc2013-10-03T11:00:00+00:00
StatestateNEBRASKA
County/zone typecz_typeC
County/zone namecz_nameADAMS
Latitudelat40.580
Longitudelon-98.510
End latitudeend_lat40.580
End longitudeend_lon-98.510
Deaths directdeaths_direct0
Deaths indirectdeaths_indirect0
Injuries directinjuries_direct0
Injuries indirectinjuries_indirect0
Damage propertydamage_property400.00K
Damage cropsdamage_crops0.00K
Weather forecast office sourcewfo_sourceCoCoRaHS
Episode narrativeepisode_narrativeAlthough this Wednesday afternoon started out with a fairly low-key development of isolated strong to severe thunderstorms in northern portions of South Central Nebraska, this convective event ended up being one of the most significant heavy rain episodes of 2013 for much of the northeast two-thirds of the 24-county area, highlighted by a small zone of 8+ inch rainfall in southeastern Greeley County. In terms of actual severe weather, this event was small in scale, featuring only a handful of quarter to golf ball size hail reports in southern Greeley and northwestern Howard counties during the late afternoon and early evening, with the largest hail stones reported four miles south of Greeley at 535 pm CDT. However, as the large hail threat diminished by sunset, heavy rainfall took over as the main story for the next several hours lasting well into Thursday morning the 3rd, as the initially isolated development in northern counties morphed into a slow-moving, southward-drifting linear mesoscale convective system (MCS). By the time all convection finally exited South Central Nebraska shortly before sunrise on the 3rd, most places generally northeast of a line from Loup City-Gibbon-Blue Hill-Superior had received at least 2-3 of rain, but with a corridor of higher amounts generally 4-6 concentrated across much of Adams, northwestern Nuckolls and southwestern Clay counties. Within these counties, just a few of the highest reported rainfall totals included 6.35 a few miles south of Juniata and 4.75 a few miles south of Trumbull. At Hastings Municipal Airport, 3.49 of the storm total of 4.13 fell on the calendar day of Oct. 3rd, shattering the previous record for highest rainfall on any given day in October (2.95 on Oct. 16, 1968). Of even greater significance, however, was the incredible amount of rain that fell mainly between 4-9pm CDT within a small portion of southeastern Greeley County. Despite limited ground-truth from the epicenter of heavy rainfall in that area, an observer five miles northwest of Wolbach measured 8.46, and radar estimates suggested that even higher amounts might have fallen roughly 4-8 miles northeast of Wolbach. Although several counties in South Central Nebraska undoubtedly experienced short-term flooding issues from this event including lowland flooding and damage to rural roads, specific flooding reports were fairly limited. However, a few known reports included water running across several county roads in southeastern Greeley County, and also water up to the hood of a vehicle on Highway 92 east of Ashton near the Sherman-Howard County line. Fortunately, a stretch of predominantly dry weather during the preceding few weeks likely mitigated more significant flooding on larger creeks and rivers. As for thunderstorm winds during this event, there were no known-instances of severe-criteria gusts, although a RAWS sensor in western Clay County clocked a near-severe gust to 54 MPH. ||Taking a closer look at event timing, the initial development of localized strong to severe storms got underway within primarily Sherman, Howard, Valley and especially southern Greeley counties between 3-7 pm CDT. During these early stages, several very slow-moving to nearly stationary multicell storms dumped heavy rainfall and isolated large hail over many of the same areas. Then between 7-10 pm CDT, the initial storm clusters finally started sinking slowly southward toward the Interstate 80 corridor, while gradually expanding in coverage and elongating into a west-southwest to east-northeast linear system. From about 10 pm to 1 am CDT, the MCS propagated slowly southward across Interstate 80 and into counties along Highway 6 from near Holdrege to Geneva. During the pre-dawn hours of the 3rd, widespread convection continued drenching primarily those counties south of Interstate 80 and near/east of Highway 281, with backbuilding along the western edge of the complex resulting in the enhanced rainfall totals over Adams County and vicinity. Finally, between 6-7 am CDT, the back edge of weakening convection departed the eastern fringes of the local area, ending nearly 16 consecutive hours of thunderstorm activity within South Central Nebraska. On the synoptic scale aloft this was a fairly weakly-forced event, as South Central Nebraska resided under relatively weak west-southwest mid-upper level flow, downstream from a larger scale trough organizing over the Pacific Northwest and Northern Rockies. However, a low-level focus for convective development existed in the form of a southwest-northeast oriented cold front that roughly bisected Nebraska during the late afternoon and evening hours. The initial mid-late afternoon storms flared up near this frontal boundary, aided by forcing from a subtle shortwave trough passing through the area. During these early stages, mesoscale severe weather parameters within the local area featured fairly modest mixed-layer CAPE values of 1000-1500 J/kg and generally no more than 30 knots of 0-6 kilometer vertical wind shear. However, the combination of the weak shear environment featuring mid-upper level flow nearly parallel to the surface front, along with seasonably-high low level moisture reflected by surface dewpoints in the low-mid 60s F, fostered the slow storm movement and resultant heavy rainfall. As the night wore on, the southward expansion of the MCS was aided by the development of a south-southwesterly low level jet that ramped up to around 40 knots at 850 millibars, enhancing moisture transport into the area.
Event narrativeevent_narrativeA rainfall total of 6.35 inches occurred.
Yearyear2,013

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ADAMS — Heavy Rain — TerraPulse