11PM Day 1 Convective Outlook for Monday, January 5. NO SEVERE THUNDERSTORM AREAS FORECAST
SUMMARY
The risk for thunderstorms will remain minimal across the U.S. today through tonight.
Discussion
Models indicate that mid-level flow is trending more zonal across the northern mid-latitudes, from the Pacific to the Atlantic. Across the southern mid- into subtropical latitudes, it appears likely to remain more amplified through this period, with one notable short wave trough forecast to continue digging across the eastern Pacific. Downstream, a lower amplitude short wave trough emerging from the Intermountain West may contribute to further suppression of mid-level ridging as far south as the central Great Plains into middle Mississippi Valley later today through tonight. However, mid-level ridging is likely to be maintained across much of the Gulf Basin and adjacent Gulf Coast, to the north of an increasingly prominent mid-level high forming near the Yucatan Peninsula. Farther east, broad mid-level troughing is forecast to shift a bit further offshore of the south Atlantic Seaboard.
Beneath this regime, modest surface cyclogenesis may commence across the central Great Plains into Midwest. This may be accompanied by some low-level moistening off a Gulf boundary layer only slowly modifying in the wake of recent cooling and/or drying. However, forecast soundings indicate that this moisture return will be capped by pronounced warm and dry layers in the lower through mid-troposphere.
California
Stronger mid-level cooling and forcing for ascent downstream of the digging offshore short wave, which could potentially become supportive of thermodynamic profiles conducive to thunderstorms, may approach the central California coast this morning before slowly shifting southward near, but mostly offshore of coastal areas through the remainder of the period.
Great Basin into Rockies
Guidance continues to suggest that mid-level cooling and forcing for ascent (associated with a short wave perturbation now progressing northeast and east of the southern Sierra Nevada) could contribute to the evolution of thermodynamic profiles at least marginally conducive to convection capable of producing lightning, across the mountains of north central/northeastern Utah this morning into northwestern Colorado/adjacent southern Wyoming later today.
Upper Midwest
Downstream of the short wave emerging from the Great Basin, forecast soundings indicate that steepening lapse rates associated with mid-level cooling and forcing for ascent, coupled with mid-level moisture return, may support a corridor of destabilization rooted generally around the 700 mb layer. It might not be entirely out of the question that this could support weak convection capable of producing lightning across the southern Minnesota through southern Wisconsin vicinity (and adjacent portions of northern Illinois/Iowa) tonight. However, probabilities for this still appear below the minimum 10 percent threshold for a categorical thunder area.