Joe’s Weather Blog: More Needed Rain
Talked to a farmer yesterday who conveyed that now that a lot of his soil is saturated, everything else will run into the retaining ponds on his large property…he said this was a VERY good thing. He’ll be happy with this mornings rain moving through.
A complete discussion coming during the afternoon.
Forecast: (Updated @ 2PM)
This afternoon: Sunny skies through mid-late afternoon in the wake of the MCS that rumbled through the region. That has stabilized things for the time being. I’m going to watch areas in N KS for the potential of additional storms that could migrate our way before 9PM tonight. Highs warming into the 80s with the sunshine.
Tonight: Some scattered activity is possible this evening & somewhat muggy. Lows in the 60s.
Friday: Partly sunny and warmer with highs in the 80s.
Discussion: (Updated at 2PM)
This morning something rather unusual happened that created “unusual” weather in the region.
During the morning a MCS (Mesoscale convective system) moved through the area. That is not unusual during the late spring and summer months. As a matter of fact they’re typically welcome additions because we can get some much needed rainfall from them.
Sometimes these systems can pack some pretty strong winds with the actual thunderstorms. That too is not unusual and you can get severe weather from them.
On rare occasions though the systems can generate strong winds on the backside of the storms, behind the circulation that you can see spinning away on local or regional radar views and that’s what happened this morning.
This system developed late last night across western KS and while the brunt of the severe storms moved to the SW/S of the KC region the winds that were created by some unusual conditions moved eastwards on the backside.
Take a look at this monster that developed last night. I didn’t happen to notice the cloud tops on this thing, but per twitter some of the tops were close to -90°C or as cold as -130°F! The images below are courtesy @cimms_satellite
So this thing marched eastwards and southeastwards. On rare occasions, and typically the winds have to form before you know they’ll actually happen a “wake low” can develop. This occurs because of an interaction between rapidly falling surface pressures and rapidly rising pressures. I’ll let wikipedia take it from there
“A wake low, or wake depression, is a mesoscale low-pressure area which trails the mesoscale high following a squall line. Due to the subsiding warm air associated with the systems formation, clearing skies are associated with the wake low. Once difficult to detect in surface weather observations due to their broad spacing, the formation of mesoscale weather station networks, or mesonets, has increased their detection. Severe weather, in the form of high winds, can be generated by the wake low when the pressure difference between the mesohigh preceding it and the wake low is intense enough. When the squall line is in the process of decay, heat bursts can be generated near the wake low. Once new thunderstorm activity along the squall line ends, the wake low associated with it weakens in tandem.”
Take a look at this map showing the 2 hour surface pressure rises (red) and falls (blue). Notice that there is a very small 1005 mb surface low near St Joe at 11AM this morning…about the time the strong winds were coming in. Fascinating stuff.
Remember all wind is is that process of air flowing from areas of higher pressure (red lines above) to areas of lower pressure (blue lines above). Where the pressures go up and down the fastest is where the wind can be generated and blow harder.
Interestingly IF this would’ve happened at night there may have been a “heat burst” like what happened in Salina/Hill City on Tuesday night (95-100° temperatures at around 12AM or so)
OK another weather 101 lesson is over with.
Here is a look at radar…
Also take a look at the doppler indicated rainfall totals…through 1:15 PM
So where are we going from here for the rest of the afternoon. The sinking air behind this wave has allowed clouds to clear out.
Notice however the area of cloudiness across N KS and S NE. There is a front (wind shift) up there and it might be able to generate at least some convection later this afternoon. Should that happen there would be the potential of some of it to make it into the region sometime this evening. We’ll watch that area carefully for the rest of the afternoon. Whatever forms out there should move SEwards…so that’s why that area needs to be watched. One issue will be if the potential storms would be able to hold together IF they run into sinking air behind the MCS that is in place on top of the region now…there is a window there between 6-9PM or so for some additional storms to move through.
Then we’ll try and sneak in dry days on Friday and Sunday with rainy/stormy days on Saturday and Monday. Saturday , in particular is not looking good with high chances of storms/rain through the 1st part of the day at least as another complex develops in the western Plains and moves towards us. There is again potential for locally heavy rainfall on Saturday.
Longer term we should get hotter and rather steamy later next week. A LOT of moisture is going to be in the ground after Monday…and that will turn into steam heat next week.