POTENT WEATHER DAY EXPECTED.
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SEVERE STORMS LIKELY FRIDAY AFTERNOON.
As many of you are aware, Friday has the potential to be a potent severe weather day across the region. There are still a few details unresolved as of early Friday but the parameters are there for all modes of severe, including a strong tornado or two. SPC continues to highlight the area in a moderate risk assessment (4 out of a possible 5).
Here's a graphic showing most of my area within the moderate risk outlook.
A broad area of severe weather is expected Friday from the upper Midwest into the lower MS Valley. Strong, potentially long-track tornadoes, large hail, and numerous damaging gusts are all possible.
SPC shows a 15% hatched zone encompassing my entire area. That indicates there is a 15% chance or greater probability of an EF2-EF5 tornado occurring within 25 miles of a point.
It currently appears that much of my area has a high chance of going under a tornado watch at some point Friday afternoon. This has the potential to be a dangerous day and I would urge everyone to be weather savvy and aware. If a tornado watch (or warning) is issued for your specific area have a plan to stay safe, especially with storms traveling at speeds in excess of 50 mph.
Additionally, this is one of those situations where I do not want any mixed signals regarding the severe potential. The forecasters at the NWS in the Quad Cities have a good discussion in place regarding the severe set-up so I will defer to them for the meteorological details laid out below.
The severe weather day that we have been messaging arrives. Bottom line up front: Confidence continues to increase on severe weather mid-afternoon through the evening on Friday. General timing will be between 2-8pm, with storms moving into our west around 2pm. Currently, the SPC has essentially highlighted our whole area with a Moderate Risk (level 4/5) for Severe Weather, which indicates numerous strong to severe storms are expected. Along with the risk of severe winds, we can expect strong winds through the day as well, as strong gradient winds develop and mixing may also translate strong winds aloft to the surface. Potent wave is currently ejecting off of the central Rockies, which is generating a strong surface low, which continues to deepen, that is set to track through the Midwest. Guidance is starting to hone in on a track of the system, which would take the surface low from west-central IA and track it through northeast IA. With that, a strong warm front traversed through the area Thursday, leaving our area in the warm sector of the approaching storm and our eyes are on the cold front and possible occlusion that works its way into the area. Overnight and into Friday morning, we will be dealing with warm advection-induced convection. Some of these storms may be strong, with a low chance to see some severe storms, mainly focusing on hail. Frequent lightning can also be expected from these storms. As this clears out tomorrow morning, we will warm up quite a bit, with temperatures forecast to increase into the upper 60s to mid 70s, especially in our south. Some guidance hints at near 80 degrees in our south! So, well above normal temperatures are forecast ahead of the cold front. Also, collocated with the warm temperatures, impressive warm advection will also pull in anomalous moisture. Thus, dewpoints are currently forecast to be within the mid 50s to low 60s. While the triple point will be the area to focus on, especially for tornado potential, we must also look in the warm sector, especially along/ahead of the cold front. Initially, we may see some more discrete convection form, but given strong forcing and shear parallel to the boundary, we are expecting upscale growth. Although, latest guidance is indicating more of a disconnected line of supercells, also supported by model soundings. Damaging winds and tornadoes will be the main threat, with areas of large hail as well. The SPC has our area hatched on all hazards, indicating that we can see significant winds/hail, along with strong tornadoes. This is a very dynamic system with above normal temperatures and moisture, which will help increase instability quite a bit tomorrow. Guidance has been hinting at CAPE values ranging between 1500-2500 J/kg, which is a bit higher than previous forecast packages, hence the increasing potential for some significant severe. Wind shear is also concerning, ranging between 40-60 KTs in the deep layer, with LLVL shear ranging between 25-40 KTs. This shear in the low levels is very concerning. Just looking at these parameters and features in place, this paints a picture for a pretty strong event. With a dive into the shear profile, hodographs also indicate effective SRH values ranging between 200-300+. Thus, when putting everything together, this is why we are expecting a line of supercell thunderstorms favoring all hazards. Strong winds above the surface will favor damaging winds, as thunderstorm downdrafts that tap into the LLJ will help to translate these winds to the surface. While we can still see some changes in the forecast, it has been rather consistent through the last week with confidence increasing daily. Thus, have plans established in the case of severe weather, especially because tornadoes that develop along the line of convection may develop rapidly and hold the potential to be strong. So, in light of Severe Weather Awareness Week, please have your Weather Radio READY, just in case we see severe weather! Strong to damaging winds will also be a big threat with these storms, so secure objects and furniture outside. THE NWS QUAD CITIES...
THE LION ROARS
The cold front responsible for the storms is going to streak east at speeds up to 50 mph meaning storms won't be in one spot long and the severe weather threat is over in all areas by sunset Friday, even earlier west of the Mississippi. The next phase of the storm is strong northerly winds, sharply colder temperatures, and snow showers later Friday night and early Saturday as the March lion goes out roaring. The EURO shows a dusting of snow as far south as Dubuque. The upper Midwest gets pounded again with more than a foot of snow in parts of Minnesota and Wisconsin.
Here's the surface depiction of the backlash snow showers late Friday night being driven by NW winds gusting to 40 mph. Ugh.
Wind chills Saturday morning are in the teens NW to the mid 20s elsewhere.
After highs in the 60s to near 70 Friday, Saturday will remain in the mid to upper 30s north to mid 40s far south. That's a good 20-30 degrees cooler than 24 hours earlier.
As poor as the weekend starts, it ends on a high note with readings soaring back into the range of 60-65 Sunday. That introduces us to our next significant storm next week which could bring the the threat of more thunderstorms (possibly strong) and heavy rain. Here's the EURO surface depiction for next Tuesday. Another intense spring storm with a 977mb pressure center.
Lots of details to work out but most of us should get into the warm sector and that could very well mean the warmest day of the year for my southern counties next Tuesday. The EURO depicts highs that look like this.
It's another wet storm for the upper Midwest with the EURO suggesting these rain totals Monday-Tuesday night.
Much of Minnesota gets hit with another big snow.
Total precipitation the next 6 days is heavy over the upper Midwest.
Significant snow cover remains in northern Minnesota and adjoining Wisconsin with current moisture content of 2-6 inches. Throw in another 2-3 inches as the EURO shows and potential for major flooding on the Mississippi could become reality. The threat is already considered high without this additional rain and snow. If a quick thaw comes accompanied by more rain the ingredients are there for a big one on the big muddy.
That's all for now. I do plan on chasing locally Friday and will of course get some pictures on if I run into something sinister. More on the severe weather set-up around mid-day. Roll weather...TS