16/12/2021
SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK1153 PM CST Wed Dec 15 2021Valid 161200Z - 171200Z...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OFTHE ARKLATEX INTO THE MID-MISSISSIPPI VALLEY......SUMMARY...A marginal risk for gusty winds and hail with a couple of strongerstorms may evolve Thursday from parts of northeastern Texas acrossthe Arklatex into parts of the Mid-Mississippi Valley....Synopsis...An upper-level trough and associated strong jet-streak will movethrough the Great Lakes into southeast Canada through the day today.Meanwhile, a second positively-tilted trough will cross the centralRockies which will keep a broad area of cyclonic flow across much ofthe central States. At the surface, an occluding, very strongcyclone will mover northeast into northern Ontario with a trailingcold front moving quickly eastward across the Great Lakes andNortheast and only slowly advancing southeastward across portions ofthe Mississippi Valley and into the Arklatex....Parts of Northeast Texas and southeast Oklahoma into theMid-Mississippi Valley...At the beginning of the period, showers and occasional thunderstormsare expected to be ongoing along and ahead of the surface front asit moves slowly southeastward. This front will slow its progressionthrough the day and eventually start to retreat northward during thelate evening and into the overnight hours. Some modest surfaceheating is possible ahead of the front with temperatures warminginto the low 70s. This may provide ample instability, when coupledwith veering and increasing flow with height, for a few strongerstorms. However, expect storm coverage and intensity to be low giventhe lack of larger scale forcing and neutral to slightly risingmid-level heights through the late afternoon/early evening. Overnight, the low-level jet is expected to strengthen as thewestern trough starts to move over the Plains. This will bringincreasing isentropic ascent and thunderstorm coverage acrosseastern Texas/Oklahoma and western Arkansas, especially after 06Z.Forecast soundings show ample elevated instability and shear for anoccasional stronger storm or two, but expect this activity to remainmostly sub-severe...Bentley.. 12/16/2021
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