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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.


Tuesday, August 8, 2023

SPC Aug 8, 2023 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook Day 1 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 1249 AM CDT Tue Aug 08 2023 Valid 081200Z - 091200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS CENTRAL HIGH PLAINS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS CENTRAL PLAINS AND ACROSS THE SOUTHEAST... CORRECTED FOR ERRONEOUS THUNDER LINE DIRECTION ...SUMMARY... Scattered severe thunderstorms are possible across portions of the central High Plains this afternoon into tonight. Large to very large hail, along with a risk for a tornado and widely scattered severe gusts, will be the potential hazards. Scattered severe thunderstorms are also expected through the day across portions of the Southeast. ...Synopsis... An unseasonably strong upper wave is noted in overnight water-vapor imagery lifting to the northeast across the New England region. In its wake, a broad northwesterly flow regime is in place from the Pacific Northwest to the southeastern states. Several disturbances are embedded within this mean flow regime from the High Plains into the northern Great Basin. These disturbances are expected to propagate to the southeast over the next 24 hours, and will be the impetus for severe weather potential for the High Plains and Southeast. ...Central Plains/High Plains... The upper wave over the northern Great Basin is forecast to move into the central Rockies by 00-06 UTC this evening. As this occurs, modest lee troughing will support southeasterly return flow, which should allow for air mass recovery in the wake of early morning convection. The combination of southeasterly low-level flow under 40-50 knot zonal flow aloft will yield nearly-straight hodographs featuring strong deep-layer shear (on the order of 50 knots). This zonal flow will foster eastward advection of steep 700-500 mb lapse rates sampled upstream by 00 UTC soundings, which when combined with low-level moistening, will result in MLCAPE values near 2500-3000 J/kg by late afternoon. Initially discrete cells are expected to develop within the upslope flow regime across northeast CO to southeast WY and the NE Panhandle. Given the aforementioned thermodynamic/kinematic environment, splitting supercells appear likely. These will pose a threat for very large hail (2+ inches in diameter) and a tornado or two, as cells migrate into improving low-level moisture across northwest KS. Consolidating outflow from storm interactions should foster gradual upscale growth by late evening. Lift associated with the ejection of the upper wave and a strengthening low-level jet will aid in MCS organization overnight across KS with an attendant severe wind risk. ...Southeast... A convectively reinforced MCV is forecast to emanate from the southern Plains into the lower MS River Valley and Southeast today. One or more thunderstorm clusters associated with this feature will likely be elevated at the start of the forecast period, posing a severe hail risk across AR/northern LA. The convective threat will transition to a damaging wind threat by late morning and early afternoon across central MS/southern AL, where temperatures are forecast to reach the low to mid 90s along and south of a residual outflow boundary/cold front. Enhanced mid-level flow associated with the MCV should provide adequate deep-layer shear for organized convection. While a few semi-discrete cells are possible, one or more organized clusters/lines appear probable as the system moves into southern GA/north FL by late afternoon/early evening. ...New England... A secondary surface low associated with the northeastern upper wave is expected to meander northeast through the New England region during peak daytime heating. Warming surface temperatures should be adequate to support surface-based convection, and effective SRH on the order of 100 m2/s2 in the vicinity of the low may allow for a few transient mesocyclones with an attendant tornado threat. However, this potential will be conditional on sufficient low-level heating, which is uncertain given lingering precipitation and cloud cover. ..Moore/Jewell.. 08/08/2023 Read more CHECK UPDATE ZOOM GRAPHIC
SUNRISE AND SUNSET TIMES IN UTC (if you're not logged in to Google)
CHICAGO UTC-6 during CST (Central Standard Time, e.g., winter)
CHICAGO UTC-5 during CDT (Daylight Savings Time, e.g., summer)