Joe’s Weather Blog: Round 1 mostly done…awaiting the bigger punch (SAT-8/5)
We had the appetizer and expected rain this morning…so far roughly 1/2-3/4″ on average in the area…there may be some additional showers (but not steady) this afternoon. Now we wait to see how things evolve tonight as strong winds above the surface start poking right towards KC…enhancing the “lift” in the atmosphere and creating more storms/rain with heavy rain potential. Where the storms form and where they track will determine whether you get 1″ of rain or another 3-4″ of rain. The main flooding threat remains overnight as I’ve mentioned for the last several days. A Flash Flood Watch remains in effect until tomorrow morning.
Forecast (as of 1PM):
Rest of today: Intermittent showers with some break in the clouds as well in some area. Cool for August…some 20° below average with highs 65-70° or so.
Tonight: The redevelopment period starts around 9PM or so…which is the typical time-frame we watch when the low level jet stream increases in strength. These are the storms that have the ability of producing flooding rains of 1-3″ rates per hour. Some areas may see in excess of 3″ more rain overnight. The exact location will be near where the storms form and potentially south of the storms formation because over time the storms should drop towards the south or southeast. Lows near 60°
Sunday: IF there is any shower activity leftover…it should fade by 10AM or so…skies will then try and thin out a bit. Cool temperatures remain however with highs in the 70s
Monday: Partly cloudy skies with highs well into the 70s
So far the forecast has worked out exactly as expected…that’s a good thing in my weather world. The rain came in when expected (after daybreak)…and now the bulk (but not entirety) of the rain has shifted away. There will continue to be lingering showers/storms in a somewhat more scattered and NOT as long lasting fashion this afternoon in the area. Take a look at the NWS radar from Pleasant Hill, MO (this will auto-update for you with the latest information).
There are many fascinating things about this weather regime we’re in right now. We went from perfection yesterday to another 1/2″+ of rain this morning. Last night when I looked at the balloon sounding that went up in Topeka to measure various atmospheric variables…I was struck by how DRY the atmosphere was. In the scheme of things it was no big deal for the year as a whole…BUT for the month of August it was VERY unusual in it’s dryness from the ground up through about 100,000 feet!
We’ve talked at times about a variable called Precipitable Water or PW. This is a measurement of the amount of water vapor (we convert it to inches) that is in the atmosphere ready to be tapped and turned into rain.
Yesterday at 7PM this variable was measured at .52″. It got me wondering…when was the last time we were soooo dry for the atmosphere as a whole in what is typically a “wetter” profile during the summer months. So I looked back and found only 1 other time for yesterday’s date/time that the atmosphere was so dry…or held so little moisture in it for August 4th at 7PM. This to me was a significant factoid to pass along. The phenomena also happened in Springfield, MO too. It was actually their driest. I know that’s real weather geek stuff right there…but it really is an amazing occurrence. The sounding records go back to about 1956…so we’re talking more than 60 balloon launches on 8/4 for the 7PM observation over these years. For perspective I’m expected the PW values tonight in the atmosphere above us to be over 2″ available…4 times the value of last night…and hence the reason why additional heavy rains are more of a concern for tonight in the region.
The 1PM surface map this afternoon shows our region squarely in a rain cooled air mass as I type this blog. Temperatures are in the low-mid 60s around the area…while farther off to the SW it’s getting hotter and hotter. South central KS is in the 90s as I type this…as a matter of fact the 1PM surface map shows the temperatures (in RED) and you can see the contrast strengthening between the rain cooled air and the searing summer heat.
This conflict in air masses will help to create a focal point for new storms to develop…and those storms could be potentially severe, but those storms will be well off towards the west and SW of the KC area this afternoon.. The Storm Predication Center is watching that area more intently for this risk. Hail/wind are the main concerns out there…and as I look at the surface winds…there may even be a weird spin-up towards central KS as well. This area is in a “slight” risk
Those storms that develop out in the Plains won’t really be a big factor for us locally…the storms that develop more or less on top of the region will be the bigger issue and that could happen around 8-10PM tonight.
There are tricks to all this though. For example the disturbance that was generated from all the rain overnight and this morning has moved towards SW MO this afternoon. Will that disturbance impact the atmosphere locally and mess things up at all? You can see it moving through SW MO by looking at the radar from down there…
Will the strengthening winds overnight above the surface impinge on the boundary more towards the south of KC? Right now it’s a lower end chance…I still think the I-70 corridor is the area to watch the most overnight for new storms and heavy rainfall potential. Our models are still VERY aggressive with total rainfall. Of note though some of these models, which were predicting over 6″ of rain locally…also said that we’d have over 2″ of rain by late this afternoon. That will not work out (from their previous forecasts).
I still think an additional 1-4″+ rain event is on tap for a good part of the area from KC southwards overnight. The Flash Flood Watch continues for the area and I feel this is appropriate given the guidance at hand. The counties under a WATCH are in the darker green below…the brighter green represents flood warnings that are in effect.
I want to show you one of our short term weather models…this product will be updated every few hours for you automatically…it’s called the HRRR model and while never perfect…it may give you an rough idea of what the “future” radar will look like as this event unfolds.
So far the forecast is working out perfectly…but I’m always leery of “spiking the football” prematurely in these situations. There are other variables that have to play out for us to get the regeneration of the heavy rain producing storms tonight…and it will bear constant monitoring on my part…especially after sunset.
Finally this morning…an amazing sunrise. There was rain falling west of KC at the time…it was moving eastwards but there were great rainbows and various other optical phenomena happening including an incredibly pink sky out there as well.
Look at this shot from Lynda Egner outside Lawrence, KS this morning.
There is a faint rainbow there and the sky is pink underneath the rainbow it appears. I’m guessing it was even more vivid in person!