:: Just as Promised
I hate to gloat, but I am extremely proud of my 00Z analysis last night. WFO's and even the SPC had initially discounted the modeling of CAPEs and Li's...except when things started to really pop - right around 1400CDT *weird...thats what I said would happen*.
Ok, enough of that...MCS/line that did form along the shortwave/frontal boundary has pushed into WI now (2200CDT). Dissipation of the frontal boundary is prevalent as winds are calm behind the storms, and there has been no real appreciative temp or moisture change in the atmosphere. Dewpoints remain elevated...still at pre-convection values of mid-lower 60's. Looking at MADIS plot, definitive frontal boundary is showing in western MN, from BJI-AXN-MML. Temps are beginning to drop a bit, but telltale wind shift and dewpoint drops are indicated by the reports. NAM seems to have best handle on initialization, as well as placement of the frontal feature for the near-term forecast period. The model progs the front to begin some meager motion eastward overnight. LLJ still progged to have one last surge from the south in advance of the front, and I think timing looks good on that being the impetus for TSRA redevelopment sometime after 07Z...with initiation on the nose of the LLJ, in south-central MN. Expect another line of activity, more showery in nature, to fill in from MKT-STC-GPZ into the morning commute. Some more stalling will occur as the front tries to push further into WI, bringing into play the possibility of training along, and just behind, the boundary as the southerly flow continues to push along and over the front. NAM targets some precip bullseyes over the ern tier of MN counties pushing the 1.5" mark by 18Z. Sunrise will also aid slight elevated redev.
After 18Z, however, things will rapidly change. Expect cool inflow behind the CFP from the northwest...dynamically backfilling, as the pressure gradient will simply not be there to warrant anything over 10kts. So, some partial drying will happen late tomorrow and into the first part of Friday. Then the holiday weekend progs got a bit more interesting...12ZGFS run paints a low to slide down the Canadian and Montana front range tomorrow, over the Powder River basin Friday, and into the Sioux Empire by mid-Saturday. Upper level dynamics are of greater concern for the system...jet goes zonal after tomorrow, and upper low associated with this next wave is progged to become negatively tilted, and somewhat cut off by Saturday. Also, GFS paints a bit of divergence in the jet as the mid- and lower-level flows in advance of the system return to a south-southwesterly orientation. Future model runs will need to resolve the scenario better...right now it either looks to be a cold-pool rainmaker, or a developing severe weather threat, or possibly both depending where you are! Right now, however, I have confidence of a rain event late Saturday. Sunday and Memorial Day look to be tamer, drier, and comfortable.
Thursday...showers and thunderstorms likely before noon. High 66. Low 48. Southwest wind turning northwest 5-10 mph. Rain chance 60%.
Friday...Partly cloudy and comfortable. High 74. East wind 5 mph. Low 50.
Saturday...Mostly cloudy. Thunderstorms develop in the afternoon. High 72. Low 45.
Sunday...Mostly cloudy. High 72. Low 46.
Memorial Day...Sunny. High 74. Low 54.