WORT 89.9FM Madison
Forecast For Monday, 9 - 23 - 24
If you've got a computer or a phone handy, it might pull up a graphic to look at as you listen to the forecast at W-O-R-T-F-M dot O-R-G forward slash weather. I'll be talking about the water vapor satellite view of the contiguous US that's up in the featured graphics. There in a moment, you may also want to reference a wider water vapor view. There's a couple of them there that they include the whole continent. Welcome to the first full day of autumn though. First of all, the sun crossed the equator southbound yesterday at 7.44 a.m., headed for Capricorn at the solstice. That was around the time we were finishing up our great inundation, at least here in the city. So the end of summer was very, very wet. The preceding three days had already produced better than an inch of rain, and the final 13 hours of summer then gave us 3.6 additional inches between what came down Saturday evening. And then the pre-dawn hours of yesterday. So between Wednesday and Sunday, September went from having 1% of its normal rainfall to 200% twice its normal rainfall as of yesterday. Yesterday's final precipitation tally of 3.97 inches ended up being not only the record for the 22nd of September, as you might imagine. It was also the single-day greatest rainfall in the month of September at Madison. That's going back to 1869. And I believe I'm right in saying, if I've done my data collection correctly, that it was the fifth, heaviest single-day rainfall event ever in Madison. So a little wonder then that we ended up with some flooded farm fields and intersections and probably some basements, various places in the city. A slow-moving cold frontal boundary was the primary cause of our repeated rounds of thunderstorms. It was laid out pretty much along the lower Wisconsin waterway as we got on towards dawn yesterday, and pretty much came to a standstill there as a wave of low pressure passed along it, and just to our south over Illinois. So we had a prolonged period in there of convergence and upward motion before, finally, northerly winds pushed in with some drier air and subsidence and turned off that precipitation process along about 9 or 10 in the morning. That low pressure circulation is now well east of us, currently bringing precipitation to northern and western New York, but the frontal boundary along which it is situated is still strung out nearby to our southeast, running southwest westward from New York down through southern Illinois and into Arkansas and Texas. A second area of leftward spin will develop along it later today associated with a speed maximum that's currently over central Texas, and that feature is going to ride up into east central Illinois or so by this evening, potentially throwing us some showers either late tonight or into tomorrow morning. Have a look at the water vapor image of the contiguous US that I was mentioning on the station's weather page, you'll be able to see that nascent system down over east Texas as well as the wider layout of the winds in the upper troposphere. Over the course of the three days of the image sequence there, you can see the rightward turning upper ridge, which kept us warm, well as I mentioned for 10 days all the way up through Saturday, and which at the beginning of the sequence there stretches from southern California up through Wyoming and south Dakota over into the central Great Lakes. So quite large, you can see that slowly working eastward driven in part by an upper trough that's making its way in parallel across Canada to the north, spinning the opposite direction, of course, leftward and impinging on the ridge along the Canadian border region in the northern tier of US states, almost like a couple of gears spinning together there. So by the end of the sequence, then we have the upper trough with its cooler air dominating areas basically to the northwest of that Texas to New England cold front that I was mentioning with upper ridging then over the eastern and southeastern parts of the US. And if you look on the white, actually on the wider water vapor view of the continent, you'll note that to the west over the Pacific Ocean, there is yet another upper ridge breaking forward over British Columbia. So behind our intrusion of cool layer currently, we've definitely got another warm up ahead as we get out toward the end part of this week. How exactly that's going to unfold is still a little bit unclear since we're going to be seeing a quite interesting interaction of three different weather systems across the east central US over these coming several days. All the components of that interaction are visible on the wider water vapor view. The first is the system that's currently down over east Texas and its part is fairly straightforward. As I mentioned, it will ripple northeastward up towards the central Great Lakes the next day or so along that stalled funnel boundary between the trough and the ridge. The only unclear part of that is just how far northwestward moisture is going to get rotated around that circulation as it passes to our southeast here early tomorrow. The far east and southeast parts of the listening area I think may get in on some passing showers, but I think areas towards Madison and northwest from there will see enough dry air in the column above to upstanch those showers before they reach ground level. Component number two is a little hard to see on the water vapor, but it's a southward push of cooler air down across Alberta and Saskatchewan. Out ahead of that upper ridge over the Pacific Northwest, that cooler air is going to kind of cut off into a week up or low somewhere probably over about Iowa or Missouri by later tomorrow or Wednesday, perhaps down into southern Illinois. That'll be once that first low to our southeast exits into Quebec and allows that second low to drop into place behind it. And that second low would then generally follow that first one northeastward where it's not for the third system, which you can barely see at this point on the wider water vapor view. It's coming on screen down at the bottom there over the western Caribbean between the Yucatan Peninsula and Jamaica. That's a nascent tropical system, which is depicted on all of the global forecast models to deepen prodigiously as it lifts north and northeastward over the Gulf of Mexico and slams into the Gulf Coast probably eastward of, say, southern Mississippi or Mobile, Alabama somewhere in there. Perhaps as a major hurricane away at the moment, what's of interest to us though up here is what happens thereafter. The post-tropical low is forecast to interact with the second low to its west. It'll probably be, as I mentioned over the lower Mississippi Valley region and probably cycling those two counterclockwise around a common center somewhere over the mid-south. That interaction plays out quite differently between the various forecast models at this point. So far, the Canadian is the only model that brings precipitation as far north as Wisconsin over this coming weekend, but the swirling interaction between giers like this is a complex one. So it's a bit of a gamble to say with any certainty whether this weekend is going to be dry, but I think it has pretty good odds at this point. Though once the evening news forecast should be an interesting one in any case, so you might tune into the details at that time. Otherwise though, the forecast looks like this going forward. Today, generally, clear skies should see some increase in passing high clouds as we get into the afternoon hours. Perhaps joined by some cumulus from a little bit of moisture that would be drawn inland off of Lake Michigan on our northeastern winds, which will come up to five to ten miles per hour. It's unclear how much of that lower cloud development we might see. Temperatures will reach the mid-upper sixties, depending a little bit on afternoon cloud trends. High and mid-level clouds will continue to pass through the overnight hours, holding temperatures to around 50 on the northeast and northeastern winds. The southeastern parts of the listening area will see those clouds sticking up a little more generally speaking, and tomorrow the passing cloud cover will be thickest to the east and southeast of Madison, perhaps with some intermittent showers working into those areas as well. Otherwise, skies that will generally be higher and more broken as far as cloud cover goes, the further northwest you go from Madison, so temperatures may reach the upper sixties or perhaps even 70 in spots that have more sun to the west and north. Otherwise, though, just probably in the mid-sixties with more cloud cover and/or showers passing, winds will be north-northesially tomorrow, five to ten miles per hour, backing more northerly and then north-westerly and coming down overnight to three to five miles per hour. Low temperatures will reach 50 or so as the skies continue to break in the overnight hours, and clearing skies as we go into Wednesday should allow temperatures that day to reach the low seventies on light north-westerly winds. Temperatures will again drop towards 50 in that overnight, and Thursday and Friday generally look clear with a ridge of surface high pressure sitting across the Great Lakes area with upper ridging building over us as well from the north and west. We may see some passing higher middle-level clouds, especially as we get later in that period and whatever activity to our south starts to encroach from the south. Temperatures look to be in the, I would say, the upper seventies both days with again relatively clear skies and those upper seventies may continue into the weekend also. Again, that will depend on how much tropical moisture comes up with whatever system evolves down there to our south. Anyway, tune into the "1, 8 in news" forecast to get all the final details on that.
Forecast For Monday, 9 - 23 - 24 by WORT 89.9FM Madison