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Archives for the SPC Convective Outlook are updated daily (approximately) with a live map at the beginning of each article. Follow the link at the end of the article to check for current updates on the NOAA/NWS Storm Prediction Center website. Also, see Archives for Chicago's hourly weather data on CARDINAL NEWS Magazine.


Sunday, June 13, 2021

SPC Jun 13, 2021 1630 UTC Day 1 Convective Outlook

SPC 1630Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1112 AM CDT Sun Jun 13 2021 Valid 131630Z - 141200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS CENTRAL APPALACHIANS...CENTRAL HIGH PLAINS...CENTRAL GULF COAST... ...SUMMARY... Scattered damaging winds are possible through about dusk across the central Appalachians and the Deep South to central Gulf Coast region. Scattered severe wind and hail are possible across the central High Plains, mainly this evening. ...Central Appalachians... Convection associated with a leading mid-level impulse is ongoing near the MD/WV/VA border region along the periphery of weak buoyancy. Additional scattered convection should develop in its wake shortly along a weak surface front from the lee of Lake Erie southwest to southern OH. Despite weak mid-level lapse rates, robust boundary-layer heating amid upper 60s to low 70s dew points will support moderate buoyancy with MLCAPE of 1500-2500 J/kg across the OH Valley. Within a belt of 25-35 kt mid-level northwesterlies, a few organized multicell clusters and low-end supercells will pose a primary threat of damaging wind, along with isolated marginally severe hail through about dusk. ...Central High Plains... Low-level moisture characterized by a plume of low 60s surface dew points is spreading north on the western periphery of a surface high. Intense boundary-layer heating beneath steep mid-level lapse rates will result in MLCAPE of 2000-3000 J/kg by late afternoon as thermodynamic profiles become deeply mixed. Thunderstorm initiation is most likely near the higher terrain in southeast WY and the NE Panhandle along a quasi-stationary front despite small mid-level height rises associated with the high centered over western NM. Storms will probably coalesce through outflow interactions, with the potential for a cluster to form and develop south-southeastward into the low-level inflow and moisture/buoyancy corridor through at least midnight. Vertical shear will be on the lower margins for supercells initially, with some potential for splitting cells producing large hail. Thereafter, severe winds will become the main threat given the expected cluster storm mode in an environment with strong downdraft potential. ...TN Valley to central Gulf Coast... 12Z area soundings sampled a plume of probable large MLCAPE in excess of 3000 J/kg should develop as further boundary-layer heating occurs amid very rich low-level moisture characterized by 70s dew points. Scattered thunderstorms are expected from the TN Valley south-southwest towards the central Gulf Coast. Within a belt of confluent 20-25 kt mid-level northerlies, multiple loosely-organized multicells clusters are expected with occasional wet microbursts producing scattered wind damage. See MCD 0943 for additional short-term forecast information. ...WI... A shortwave trough over northwest ON this morning will dig southeast and amplify through tonight across the Great Lakes, in response to upstream height rises over the northern High Plains. The trough will be accompanied by a strong northwesterly mid-level jet which will yield a highly elongated hodograph as 0-6 km bulk shear increases to 60-70 kt this evening. The primary concern is the lack of low-level moisture return after a prior frontal intrusion. With only meager buoyancy, an inverted-v thermodynamic profile should support a few high-based/lower-topped cells capable of isolated damaging winds and marginally severe hail from late afternoon through about dusk. ...Interior OR/WA... Embedded speed maxima will eject north-northeast over western OR/WA on the eastern periphery of a midlevel trough offshore. On the east edge of the more persistent rain/clouds along a baroclinic zone, meager buoyancy from parcels rooted near 700 mb is expected along and east of the crest of the Cascades amid modest mid-level lapse rates. Strong speed shear from the boundary-layer to mid-levels will support a few fast-moving cells with isolated severe gusts and small to marginally severe hail as the main hazards. ...Southwest OK and northwest TX... An MCV drifting across southwest OK may be the focus for intensifying thunderstorm development this afternoon. Guidance differs greatly with the degree of development, but the westward advection of rich boundary-layer moisture from the I-35 corridor should be adequate to overcome MLCIN by late afternoon. A couple of multicell clusters could develop into this evening with a risk for at least isolated severe wind and hail. ..Grams/Squitieri.. 06/13/2021 Read more LIVE:
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