Joe’s Weather Blog: Late Week Storms

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Good afternoon…St Joseph this morning dropped to 37° for a record low temperatures (previous was 39°). That should do it for record lows for quite some time as the cooler air is moving away today (notice the SE winds increasing) and the warmer air starts to move in overnight tonight (stronger south winds).

Forecast:

Tonight: Fair skies with a small chance (20%) of some scattered showers of t-storms moving through after 3AM or so. Winds increasing from the south at 15-25 MPH keeping temperatures in the middle 50s for lows.

Tomorrow: Slim chance of lingering showers in the region through 9AM or so (20%) then clearing, windy and warmer with highs near 80°. South winds of 20-30 MPH with gusts to 40 MPH possible with enough sunshine stirring the air.

Monday Night: Fair and warm with south winds of 15-25 MPH. Lows in the middle 60s.

Discussion:

3rd record low in a row this morning in St Joseph, MO…pretty impressive for this time of the year (actually any time of the year really). For KC the low bottomed out at 43° (record is 39°). There may have been some patchy frost north and northeast of the KC area.

Take a look at the 850 mb map from this mornings upper air balloon reports and notice that the cool air, denoted by the bluish colors is still hanging on through parts of the Plains states…the next couple of maps are from Unisys.

 

The contours above are the temperatures in Celsius…now take a look at the forecasted temperatures at that level (about 5000′) up or so for tomorrow evening…(note…if you read this blog on Monday these maps will be for Tuesday morning)

 

The bluish colors are long gone and strong SW winds aloft are transporting warm to hot air into and through the Plains states…now lets jump to later Tuesday night…(and Wednesday morning, if you read this Monday morning)

 

So the chilly air of the past week is moving away. It’s been a cool week as the departures from average show for the Midwest/corn belt region.

So now we get to warm up this week…and as the warmth comes back so will at least some moisture…not only on the surface but also aloft. The next map shows the PW or precipitable water which helps us get an idea on the amount of moisture through the atmosphere. This map if valid for Wednesday evening…note the location of the stationary front…and also the way it coincides with the above average amount of moisture in the atmosphere…click on the graphics to make the images larger and more readable.

nam_pwat_mslp_east_29 sfc

So we have the moisture…we have a stationary front in the area…we have the heat (80s for highs Wednesday)…so we should have a ton of storms and heavy rainfall right? Well hold on for a second…let’s see whether or not the air at 10,000 feet or so is cool or “warm”. are we capped or not capped?. Check out this NEXLAB image for the 700 mb level for the same time later Wednesday.

 

We’re around a +10°C+ temperature which indicates that we’re probably pretty capped. It’s not that strong of a cap though considering the various features in the area and the forecasted instability is rather strong/high…so IF the cap can break we may have strong storms somewhere in the region Wednesday evening/night.

By Thursday the cap should be considerably weaker and then virtually non-existent into the beginning of the weekend. So IF we can keep that front around the region and we can get warm enough in the day…we should see repeated bouts of convection in the region. With that potential comes the potential of locally heavy rainfall. Promises…promises but it’s a set-up for over 3″ of rain in parts of the region but it’s impossible to forecast exactly where.

What can happen in these scenarios is that the repeated bursts of convection then move the stationary front and allow it to waffle around helping to refocus the convection in other places the next day. Also various outflows from the storms will help reignite additional bouts of storms and where those set up is impossible to forecast till radar shows the outflows. All I can say is with 1) the stationary front in the area and 2) the higher than average amounts of moisture in the atmosphere through the beginning of the holiday weekend and also 3) potentially very light winds aloft allowing the storms to pour down in localized areas…that the set up is there for heavy localized rainfall and even flash flooding. Will it be everywhere…no but some of our counties will be vulnerable if the set-up plays out.

The GFS does show some decent rain out there with this..but I’m surprised it’s not showing more considering the GFS loves to over-forecast rainfall and especially convective rainfall.

gfs_tprecip_mc_57

It’s forecasting 1/2″-1″ or so along the I-70 corridor through Sunday morning…which is nice but not the greatest in this scenario.

One possible issue that we could have, despite the great set-up of the 3 features I mentioned a while ago…is that there is no decent wave moving into the area to help to really trigger storm formation…in other words all the features are there but there is no big catalyst to focus and fire off a larger scale eruption of storms in the region.

Finally the other feature that we’ll be watching, believe it or not for the next 10-12 days is this upper level storm that is int he PAC NW right now. This is amazing to me because it’s going to be such a long-term discussion point.

 

You can see it there spinning around…it’s going to drop into the SW part of the country over the next few days and then spin around down there (giving parts of the south Plains some significant rainfall into W TX!) …track it via the GFS forecast…this goes for the next 8 days…and it’s still spinning around at the end of the 8th day!

 

Why does it take so long to move through the Plains…because it’s cut-off from the main jetstream across the N US and Canada. There is nothing to move it along. so the pattern gets all blocked up which means repeated rains for some…and for others not so much.

Have a great rest of the weekend and I’ll get another blog update done by 10AM or so Monday morning.

Joe

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