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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.


Wednesday, February 15, 2023

SPC Feb 15, 2023 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1147 PM CST Tue Feb 14 2023 Valid 151200Z - 161200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY AND WESTERN TENNESSEE VALLEY... ...SUMMARY... Widely scattered severe thunderstorms are possible over parts of Texas and Oklahoma beginning late in the day and into the evening on Wednesday. A severe threat will also develop overnight over the lower Mississippi Valley/Mid-South region, with a tornado risk. ...Eastern OK/North-Central TX to the Mid-South... Late-evening satellite imagery depicts a well-defined upper low digging southeast into northern AZ. This feature is forecast to shift into the southern Rockies by mid day as a 110kt 500mb jet translates across the desert southwest toward the southern High Plains. With time this feature will advance into eastern KS allowing the trough to become more positive tilted as it moves into the central Plains. This evolution will maintain broad southwesterly flow across lower latitudes, including the Mid-South region. Of particular concern will be the development of a pronounced LLJ across the lower MS/TN Valley, especially during the latter half of the period when a marked increase is expected (in excess of 60kt). More appreciable mid-level height falls will remain north of the higher-buoyancy air mass, thus low-level warm advection will likely prove instrumental in the majority of supercell development through the period. At 05z, a narrow band of strongly-forced convection is observed along the front over AZ. Otherwise, most of the southern states are convective free with strong capping. Low-level trajectories favor Gulf air mass advancing inland across the lower MS Valley, and mid 60s surface dew points are well established at this time over much of the upper TX Coast and LA. Latest guidance suggests this air mass will easily advance north into AR/western TN Valley later today; however, convective development will likely remain suppressed until the latter half of the period when the LLJ intensifies in response to the approaching short wave. Upstream, strong boundary-layer heating across the southern High Plains will result in very steep surface-3km lapse rates from the southern TX Panhandle into western OK/northwest TX. It appears this steep lapse rate plume will overspread the northwestern portions of return moisture across south-central OK/north-central TX, just ahead of the front/dry line. As temperatures warm into the lower 70s capping should weaken and scattered convection is expected to develop. Forecast soundings favor supercell development and this activity should spread east during the evening hours with an attendant threat for all hazards. Downstream, LLJ will increase across LA into western TN from late afternoon into the evening. Steep mid-level lapse rates will overspread this region as 3km capping gradually weakens. As the cap weakens, isolated discrete supercells are expected to evolve within a moistening, warm advection regime. ESRH values in excess of 300 m2/s2, along with steep lapse rates, and modest instability favor severe supercells capable of producing tornadoes, possibly strong. A corridor of supercells may ultimately evolve along an axis from southeast AR into western TN, during the latter half of the period, as the cold front will not advance east of the MS River prior to sunrise. Warm advection should be the primary forcing mechanism for this activity, thus episodic bouts of severe are possible. ..Darrow/Thornton.. 02/15/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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