What an unusual weekend for the middle of August. Beginning last Thursday, we've had the following high temperatures:
High: 73.3ºF - Avg for the day: 68.2ºF - Thursday
High: 66.1ºF - Avg for the day: 63.2ºF - Friday
High: 64.6ºF - Avg for the day: 62.2ºF - Saturday
Keep in mind that our average daytime highs right now are right at 88ºF, so as you can see, we've been running more than 20 degrees below normal for the last several days thanks to an extremely strong wedge of cool air pushing down the east side of the Appalachian Mountains. I've requested from the NWS, the records that were set for the coolest Max high temperatures this week and will hopefully have those tomorrow. We almost never see CAD events this strong during the summer, so it's been a very unusual event for us. The wedge will slowly begin breaking down later today into Monday, but the rain will stay with us through the end of the work week.
Today
I believe that today may bring more rain than we've seen here in the last several days. A surface low near the Gulf coast may begin to lift toward the NNE as the day progresses, and with it will come the rain. We've had light rain/moderate drizzle for the last few days due to the overrunning of warm moist air over the cool surface temps. Situations like what we're currently experiencing tend to stabilize the atmosphere, so you don't see the heavy rain and thunderstorms develop like we saw several weeks ago, instead we get the drizzle/light rain. Had this been winter, I have no doubt that we would be buried under ice right now. CAD events, especially as strong as this one, would be disastrous in the winter time, so we should be happy it happened in August instead of 5 months from now.
As the stalled front drifts back to the north toward our area, it will provide the focus for the rain to return to the metro area. There is currently a Flood Watch issued for parts of north Georgia (although Gwinnett, Forsyth, and Walton were left out) for the potential for minor flooding today. (See map above)
Monday - Thursday
Here's the extended discussion from the NWS:
ISSUED AT 445 AM EDT SUN AUG 18 2013
THE WET PATTERN CONTINUES INTO THE EXTENDED. THE STATIONARY FRONT OVER SOUTH GA TODAY WILL MOVE SLOWLY NORTHWARD THROUGH MONDAY AND SHOULD BE SOME WHERE BETWEEN ATL AND MCN BY TUE MORNING. THIS FRONT WILL WEAKEN SOME BUT IT WILL STILL ACT AS A GUIDE FOR GULF MOISTURE TO MOVE NORTHWARD ACROSS THE REGION THROUGH THE MIDDLE OF THE WEEK. THE WEDGE LOOKS TO FINALLY BREAK DOWN SOMETIME MONDAY WHICH WILL ALSO ALLOW FOR A MORE DIURNALLY DRIVEN PRECIP PATTERN THROUGH DAY 7. BEST TIMING FOR THE HEAVIEST RAIN WILL BE IN THE SHORT TERM BUT DEEP TROPICAL MOISTURE REMAINS OVER THE REGION THROUGH WED/THU WITH PRECIPITABLE WATERS IN THE 1.5 TO 2.0 INCH RANGE THROUGH THU. THE DEEPER MOISTURE MOVES NORTH AND EAST OF THE STATE BY THU NIGHT BUT THE DIURNAL CONVECTIVE TREND WILL CONTINUE INTO NEXT WEEKEND. TEMPS WILL BEGIN TO REBOUND BY TUE AND BE BACK TO NEAR SEASONAL NORMS BY THU/FRI.
Hydrology
ISSUED AT 445 AM EDT SUN AUG 18 2013
AN UPPER LOW PRESSURE SYSTEM TO THE NORTHWEST WILL INTERACT WITH A A WARM FRONT DRIFTING NORTH TODAY TO PRODUCE A CHANCE OF HEAVY RAIN ACROSS MAINLY NORTHWEST AND WEST CENTRAL GA TODAY. MODEL AND HPC QPF NUMBERS SUGGEST ANYWHERE FROM 1 TO 2 INCHES WITH ISOLATED HIGHER AMOUNTS IS POSSIBLE THROUGH THE AFTERNOON AND EVENING HOURS TODAY. THEREFORE... HAVE POSTED A FLASH FLOOD WATCH THROUGH 8 PM THIS EVENING FOR AREAS ALONG AND WEST OF A BLUE RIDGE TO ATLANTA TO MACON LINE WHERE THE GREATEST RAINFALL AMOUNTS ARE EXPECTED. HOWEVER... STILL MUCH UNCERTAINTY ON LOCATION...INTENSITY AND DURATION OF CONVECTION THROUGH THE AFTERNOON AND EVENING HOURS... SO SOME AREAS EAST OF THE WATCH COULD STILL SEE PERIODS OF BRIEF HEAVY RAIN.
The long term models seem to think the trough that has been stuck over the eastern part of the US, will not be going anywhere any time soon. Better than normal chances for rain will be in the cards through August. (see maps above)
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