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Potentially active week ahead for the Midwest
Looking like a busy week ahead. Both the NAM and GFS models are indicating a potentially active period of thunderstorms (some severe) across Missouri, Illinois, Iowa and surrounding regions from now through the Friday/Saturday timeframe. Setting the stage for this week is deep, abundant low-level moisture and warmth, with dewpoints in the high 60s/lower 70s. Upper flow has been slowly increasing as an upper low in the deep south moves northward, but a better shot of mid and upper support will arrive sometime mid-week with a subtle (but strengthening with time) shortwave trough moving across the Midwest. On the days that this feature approaches and passes (currently it looks like from Tuesday-Thursday), severe storms, and possibly a few tornadoes, are possible.
From today (Sunday) and Monday, weak upper support from the low to the south as well as an approaching cold front should provide for scattered non-severe storms both days. On Tuesday, models show westerly midlevel flow increasing to 30-35 knots over northern Missouri and Iowa, with a strong low-level jet at 850mb arcing in at 30-35 knots from the southwest. At the surface, winds should be southerly, providing decent turning in at least the low to mid levels. CAPE (istability) maxes out at 3000 j/kg in western Missouri. In addition to a developing warm front, boundaries from previous days' convection should be in place to provide storms with opportunities to interact and deviate from the mean flow. All this means that Tuesday has some potential to be a moderate severe weather event, with high winds and large hail possible across the lower Midwest. Tornadoes can't be ruled out with any isolated storm that can find a boundary to track along. Tuesday night could feature an all-night thunderstorm complex moving eastward through Missouri and Illinois, great for nighttime lightning photography.
Wednesday and Thursday may see more rounds of severe storms from the upper system and surface boundaries, with everything pushing to the east on Friday. However, strong northwest flow develops on the backside of the trough on Friday-Sunday, with cooling midlevel temps and lingering surface moisture providing more opportunities for local storms through the weekend.
Tuesday looks like a solid Midwest storm observation day, along north of I-70 in Missouri if the models are correct. Central Plains dryline setups will exist with this system, far to the west closer to surface lows in the Kansas and Nebraska areas, giving storm observers on vacation something good to go after. For me however, the proximity of observing potential here close to home will likely preclude any trip to the Plains.
In layman's terms, lots of local observing ahead around St. Louis and surrounding areas/states this week! As always, stay tuned to the Facebook/Twitter feeds for the most current updates. I'll try to update the blog with photos and video whenever I get the opportunities.