Originally published at: With multiple days of heavy rainfall possible, we are initiating a Stage 2 flood alert through the weekend – Space City Weather
In brief: In today’s post we’re are initiating a Stage 2 flood alert through Memorial Day Weekend due to the potential for periods of heavy rainfall that will accumulate in creeks and bayous over time. Please remain weather aware for the next week.
Overall pattern
With the complete breakdown of high pressure, plenty of moisture in the atmosphere, and an upper air pattern that will eject a series of disturbances into Texas from the southwest, the next seven days (at least) should feature periods of moderate to heavy rainfall. During this time accumulations of 4 to 8 inches of rainfall are possible, with higher amounts likely in some areas. As rainfall totals stack up over time they may bring some rivers, creeks, bayous, and other waterways to flood stage. For this reason we are putting a Stage 2 flood alert into effect through next Monday. This means that while most of our roads should be fine most of the time, there will be the potential for flash flooding, and you should remain weather aware.
You have questions, we don’t have answers
Let’s start with this fact: The large mass of showers moving into southwest Houston this morning was not well predicted. This underscores the reality that timing these atmospheric disturbances (which produce the lift and other conditions needed for rainfall) more than 24 hours out will be difficult. I know there are a lot of graduations later this week, and weekend, in addition to graduation parties. It is that time of year. Unfortunately there is no way I can sit here on Tuesday morning and tell you whether it will, for sure, rain on Friday evening, Saturday afternoon, or whenever.
All we can really say is that there is a good likelihood of rainfall, some of which may be heavy. Some of these showers may come in the form of thunderstorms, but the overall threat for severe weather beyond rainfall is not particularly high. It also will not rain all day and night, certainly, but the potential for showers during the daytime, through Memorial Day, is pretty high, especially over the weekend.
There are some benefits to all of this. Although Harris County is now drought free, many areas near Houston remain in a moderate to severe drought. Additionally, you may have heard about the water crisis in Corpus Christi. This will not end the problems there, but the potential for 3 to 6 inches of rainfall over the next week in the Coastal Bend area will provide some help with at least short-term water issues. And finally, instead of high temperatures around 90 degrees, we are going to be in the low- to mid-80s for the rest of the week.
Tuesday
Well, if you read yesterday’s forecast post, you may recall that I thought most of the daytime on Tuesday would be rain-free. Surprise! The arrival of a round of showers from the southwest this morning means that we could see intermittent showers through about noon. I think the stronger storms associated with this system will mostly remain off the coast, but we can’t rule out some moderate or heavy rainfall in the Houston region this morning. After this we probably will see some partly sunny skies this afternoon that will allow high temperatures to push into the mid- or possibly upper-80s. It will be plenty humid.
Then, beginning this evening, a weak front will approach and should move into the area from the north. I am not totally confident in how this system will progress, but we can probably expect a line of storms to develop north of Houston around sunset (i.e. in the vicinity of Conroe), and then propagate south into Houston this evening before reaching the coast around midnight, give or take. I suspect these storms will weaken as the move into the city, you should nonetheless be prepared for the possibility of thunderstorms this evening, and into early Wednesday across the region.
Wednesday
This will be a partly to mostly cloudy day, with highs probably in the mid-80s. Rain chances during the daytime hours will likely depend on how worked over the atmosphere is on Tuesday night (i.e. more widespread storms on Tuesday evening would probably lead to less coverage on Wednesday during the daytime, and a weaker line of storms on Tuesday would allow for more widespread showers and thunderstorms on Wednesday). Anyway, I’d peg rain chances in the vicinity of 50 percent. After today, rain chances will increase for the rest of the week.
Thursday, Friday, and Memorial Day Weekend
In general we expect these days to have mostly cloudy skies, highs in the lower 80s, and overnight lows in the mid-70s. That’s the easy part. In terms of rainfall, each day will have rain chances in the vicinity of 70 to 90 percent, with slightly lower chances during the overnight hours. It would be a fool’s errand to try and predict precisely when it will rain, or when the heaviest rainfall will occur. Just know that the pattern will be broadly supportive of rainfall, and that as amounts accumulate we may well see street flooding and flash flooding (rapidly rising waters). Generally mobility will probably be OK most of the time, but probably not all of the time for everywhere. We, at Space City Weather, will be with you the whole period. It’s not exactly the Memorial Day Weekend festivities we envisioned either, but here we are.
Next week
Rain chances will remain healthy next week, but probably take a step back to around 50 percent daily. Maybe. Honestly, it’s difficult to predict when this overly wet and cooler pattern will end with any confidence.
