Monday Afternoon Update.....Flash Flood Threat Increases Slightly

3:45pm Monday July 23, 2018 - Chief Meteorologist Chris White

Good afternoon. As everyone has probably seen a Flash Flood Watch has been hoisted across our entire coverage area. Overall though the forecast looks right on track and the highest precipitation chances are from now through 9pm, and chances are at 95%. After 9pm will follow guidance from NWS and most guidance in slowly winding down coverage, call it about 10% every hour past 9pm. By 2:00am coverage of showers and storms should drop below 50%. We will carry a 40% chance of rain through the early morning Tuesday before chances ramp back up Tuesday after sunrise. All of that being said there continues to be a little uncertainty as to if rainfall rates will surpass 2 inches per hour.  Precipitation rates have been lower than anticipated across SC which is where all of this moisture is moving from.  

 

Synopticlly (large scale) speaking the upper level level low continues to push south through Central Georgia, keeping our area in the Southeast flow. Unlike the May 31, 2018 Flash Flood event where significant flooding occurred, the flow off the Atlantic is not as moist. In fact the Southwest mountains of NC (that normally are the first to flood) are not included in the newly hoisted flash flood watch because most of this flow from Southeast to Northeast is being channeled up roughly the I-77 corridor. A stalled frontal boundary is draped roughly along a line from Athens GA to Columbia SC, Charlotte NC, up to Greensboro NC. A spoke of upper level energy is moving North  through the upper level flow and is positioned near Columbia SC. Moisture from Southeast flow is becoming very buoyant due to the lift created by that stalled front and spoke of energy. That is why there has been explosive shower and storm development across SC over the last hour and a half.  All of that moisture is due to move up into NC roughly from Concord West to Asheville. That’s the reason for the new Flash Flood Watch.  

It is also worth noting that some of the new high resolution model runs are developing another round of convection over SC and are now throwing it up into the area on up into the night. For now though none of the other model suites are indicating this. It’s something we will monitor and update accordingly as we go through the evening.

In our 8 County forecast area we are anticipating 1.5 to 4inches of rain through tonight. There could be locally higher amounts near the Eastern slopes and along Hwy 16 in our eastern counties. 

 

Satellite Upper and Lower Water Vapor Imagry and Radar 3:45pm

Weather Graphics Update from NOAA,  and Flash Flood Watch Counties

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9:00am Monday July 23, 2018 - Chief Meteorologist Chris White

 

Good Monday Morning. Let’s hope your week gets off to a great start. Weather wise mosty cloudy skies as of 9:00am. Temps in the upper 60’s and approaching 70°. Dewpoints are in the low 60’s now but those will creep up into the upper 60’s this afternoon and especially this evening. 

 

 

3 Day Severe Weather Outlook

9:15am Goes East Imagry: Red outlining the very broad upper low that stretches from The Great Lakes and down into Florida. “L” indicating the next spoke of energy that is moving North. Showers and storms are already developing in response to that and those are moving North toward our area. 

This morning there is some sun out there so that will aid the atmosphere to destabilize ahead from the aforementioned showers and storms mentioned above. While severe weather is not a big concern today, these storms could get strong and produce frequent lightning and torrential rainfall. Pea sized hail may be possible with the strongest storms this afternoon and evening. Highs today reach the up to around 80°.   Right now I believe our eastern counties will see more rain than our western counties today. This upper trough will continue to negatively tilt, pulling the band of moisture that is currently alon the Sandhills and cost to the West. Models in great agreement that the entire forecast area gets in on the rainfall this afternoon and evening. Showers and storms are moving North this morning but this afternoon will start to move from SSE to NNW. Additionally as the trough tilts negatively a narrow band of convection may form and train over the same areas over and over this evening. That raises the eyebrow a little bit for Alexander, Catawba, and Lincoln as we believe that line will stall somewhere along I-77. A small jog West is the difference between flooding rains and showers. We will monitor and keep you updated.

 

As shown above in the new SPC graphics above, thunder is in the forecast for the next three days.  At this time we are in a general thunderstorm risk which means widespread severe weather isn’t likely. I agree with the SPC and things look in good order there.   Tuesday winds will back and begin to change the flow. Southwest winds will keep things moist and unsettled even though the upper low begins to fall apart Tuesday Evening.  The same looks to happen everyday over the next 7, yeilding most areas to see a good 2-4 inch rainfall with locally higher amounts. More details later on.