Updated 845am CDT Wednesday / 30 October 2013
…. A Strong Upper Air Storm System / Cold Front to Move Overhead ….
…. A Round of Rain Showers and Thunderstorms as System Passes ….
…. Flash Flood Watch Valid 7pm Tonight to 12 Noon Thursday ….
…. Clearing…. Less Humid and Cooler Friday into the Weekend ….
On this Wednesday morning…. a surface high pressure area is over the southeastern USA with a cold front extending westward from the Ohio Valley into Kansas southward into Oklahoma and then northwestward into Colorado around a developing surface low pressure area. From that low, a cold front extends south southwestward into New Mexico and northern Mexico. As a result of this surface weather pattern, surface winds are south southeasterly across our area.
In the upper levels of the atmosphere… a eastward moving strong upper level low pressure area is over Wyoming southwestward into Utah. As a result, the upper level winds over south central Texas and the Austin metro area about 18,000 feet above the ground are southwesterly at 35 to 45 mph.
With the upper level low to our northwest moves eastward by today into tonight, the inflow of moisture from the south and southeast is continuing as atmospheric instability and lift increasing. We’ve already seen rain shower and thunderstorm coverage increase and that will continue especially later today into tonight and Thursday. Some periods of heavier rain are possible.. especially tonight into Thursday.. as the upper air system, moves by to our distant north. Current NWS guidance suggests than upwards of 1 to 3 inches of rain could fall over our area between now and midday tomorrow.. isolated heavier totals are certainly possible. We could see some periods of localized flooding later today through tonight and early tomorrow across our area. A flash flood watch has been issued by the NWS/Austin-San Antonio for all of the local area effective at 7pm tonight through 12 noon tomorrow.
As the upper system passes, an associated cold front will be allowed to drop through the area by late tomorrow afternoon into tomorrow night with high pressure.. cooler and drier air.. and clearing skies taking hold late week through the weekend.
By early next week, with low level moisture returning and another cold front approaching from the west, I’ll increase cloud cover with a chance of rain returning as well.
Regarding my forecast, my local forecast confidence: High forecast confidence through tomorrow afternoon (exact timing of rain chances and possibility of flooding being the confidence reducing factors) then very high confidence for Thursday night and Friday through the weekend. Confidence falls back to moderate for Monday into Tuesday with probability and timing of rainfall being the confidence “reducers”.
Have a good Wednesday…
Meteorologist Troy Kimmel