Update on Heavy Rain Potential This Week...

...Overview...
Periods of rain and isolated thunderstorms will increase across the area again at times from Monday afternoon or evening through late Wednesday evening. Locally heavy downpours of rain are possible at times with some of this activity in at least some parts of the area, which could lead to mostly minor flooding of low lying and poor drainage areas such as low water crossings at times in at least some parts of the local area.


...Forecast Rainfall Amounts...
Average total rainfall is expected to range from near 1 inch in extreme Northern parts of the area (northern Williamson County) to around 3 inches in Southern parts of the area (southern Hays County).  

Locally higher amounts possible in some spots (especially in Southern parts of the metro area). Present indications suggest the rainfall is likely to be most widespread and possibly heavy at times locally from near dawn Wednesday through about Sunset on Wednesday. This will potentially include both the morning and afternoon rush transportation periods based on present indications.

Please note that present indications suggest that even heavier rain will occur on a more widespread basis not far to the South of the local area on Tuesday and Wednesday, generally toward I-10 and South from there, including the San Antonio metro area.


...Potential Flooding Risks...
Due to saturated ground conditions and continued moderate to high river and stream levels across the region, conditions will need to be monitored closely for potential flooding at times, especially on Wednesday. 

If flooding were to occur locally, it would most likely consist of periods of high water in the typical low lying and flood prone areas such as low water crossings and similar areas, and again, this would most likely be a concern on Wednesday per present indications.

As noted in the section above, present indications suggest that even heavier rain will occur on a more widespread basis not far to the South of the local area on Tuesday and Wednesday, generally toward I-10 and South from there, including the San Antonio metro area. An even higher risk of flooding is likely in this region during the period.


...A Note on the Uncertainties with this Forecast...
Please note, there is a higher than normal spread among computer forecast models regarding the most likely rainfall scenario for the local area in this situation. This is likely due to the complex nature of the situation, with a weather disturbance moving in from the West and moisture from two tropical systems in the Pacific possibly being pulled Northeast into the local area from Tuesday into Wednesday. 

There is no question that rainfall will occur area-wide especially on Tuesday and Wednesday ("high" confidence) but due to the above mentioned uncertainties and complexity of the situation, the confidence on the forecast rainfall amounts is only "moderate" at this time. If any changes were to be made, it would most likely be to raise rainfall forecast amounts for a good portion of the local area, not lower them, for the Tuesday-Wednesday period. This should become more clear during the day on Monday.

We will continue monitoring the situation and issue updates as conditions warrant.