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  Jared Smith 6:13 pm on February 28, 2012 Permalink
  Tags: lowcountry ( 2 ), overnight threat, severe weather   

  Wednesday’s overnight severe threat expected to remain north of the Lowcountry 

  

  SPC has an enormous slight risk area for tomorrow and tomorrow evening, parts of which include northern and central SC (including the northern tier of the Charleston Tri-County area) as a strong Great Lakes system and associated front push eastward (and weaken). WFO Charleston has not been sold on this scenario thus far due to the forecast weakening and unfavorable timing:

  STORM PREDICTION CENTER HAS BROUGHT THE NORTHERN THIRD OF THE
  FORECAST AREA INTO A DAY 2 SLIGHT RISK. THE FOCUS FOR CONCERN
  APPEARS TO BE WITH THE TAIL END OF A CONVECTIVE LINE WEDNESDAY
  EVENING AND OVERNIGHT…ENHANCED BY INCREASED FORCING FROM THE COLD
  FRONT AS WELL AS A 30 TO 40 KT LOW LEVEL JET DESCENDING INTO THE
  WESTERN AND NORTHERN ZONES. INSTABILITY WILL BE WEAK…ESPECIALLY
  CONSIDERING THE LESS FAVORABLE NOCTURNAL TIMING OF THIS THREAT.
  PREFER TO KEEP MENTION OF SEVERE WEATHER OUT OF THE HAZARDOUS
  WEATHER OUTLOOK AT THIS TIME DUE TO UNCERTAINTIES IN THE AVAILABLE
  INSTABILITY…COVERAGE OF SHOWERS AND THUNDERSTORMS…AND
  POTENTIAL WEAKENING OF THE SYSTEM UPON ITS APPROACH.

  I’ll keep an eye on this but it doesn’t appear it will be much to contend with tomorrow night. Rumbles of thunder aren’t out of the question overnight into Thursday.

  Saturday may be a more favorable severe weather day:

  IT SHOULD BE NOTED THAT LOW LEVEL WIND FIELDS AHEAD OF THE FRONT
  APPEAR VERY IMPRESSIVE. IF THE ATMOSPHERE CAN DESTABILIZE ENOUGH
  AHEAD OF THE FRONT…THEN THERE IS CERTAINLY A POTENTIAL FOR SEVERE
  WEATHER ACROSS THE AREA. IN ADDITION…BREEZY OR WINDY CONDITIONS
  ARE EXPECTED ON SATURDAY…EVEN OUTSIDE OF CONVECTION DUE TO THE
  STRONG LOW LEVEL WIND FIELDS…AND AGAIN ON SUNDAY WITH STRONG
  COLD AIR ADVECTION IN WAKE OF THE FRONT.

  There’s a lot of divergence in the model solutions still, especially with the upper-air setup. The GFS wants to do something similar to last Friday in which the area was in the right-rear entrance region of the jet, allowing for divergence aloft; the Euro is digging a deeper trough over Texas and is staying a bit more to the west. Will be a situation to watch as we get into meteorological spring starting Thursday.

   
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  Jared Smith 2:20 pm on February 24, 2012 Permalink
  Tags: sc lowcountry ( 19 ), severe weather   

  Still waiting on storm initiation in the Lowcountry. A special 18z upper-air sounding revealed a cap in place over the Charleston area still; however, with clearing allowing for rapid warming and the front approaching, this cap will erode and storms will initiate. Most severe weather so far in SC has occurred in association with the jet streak to the north in the Midlands, where a few tornado-warned storms have already moved through.

   
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  Jared Smith 12:05 pm on February 24, 2012 Permalink
  Tags: sc lowcountry ( 19 ), severe weather, tornado watch 37   

  Tornado Watch for the SC Lowcountry until 8PM 

  The Storm Prediction Center has issued another massive tornado watch, Tornado Watch 37, until 8PM. Of current concern are storms firing in the Florida panhandle and southern Georgia which will move northeast into an increasingly destabilizing environment with better upper air support.

  Keep a close eye on the weather throughout this afternoon. Looks like the best risk will coincide with the afternoon commute. I’ll monitor trends and update here and Twitter as needed.

   
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  Jared Smith 10:03 am on February 24, 2012 Permalink
  Tags: moderate risk, sc lowcountry ( 19 ), severe weather   

  Moderate risk day in SC 

  I’m monitoring the severe risk today; a moderate risk exists from about Summerville northeastward through Moncks Corner and into NE SC, eastern NC, and SE Virginia.

  A fairly widespread damaging wind event is being forecast by SPC, with an isolated tornado risk in the mix as well. Tornado watches are up just to the west, with a few tornadic storms recently detected in northeast GA.

  No watches are up for SC yet but it’s just a matter of time before we see one. This morning I’m keeping a close eye on temperatures and cloud cover. Right now there are broken clouds over most of the Lowcountry; models indicate they will stay this way for a few more hours. The NAM warms things into the 80s; the GFS is a bit more conservative. This is key for additional instability. The next few hours are critical for any severe threat in SC.

  Coastal areas are in a slight risk area for severe weather; forecasters are anticipating that the marine influence will take some of the punch out of these storms as they run for the coast, but damaging winds are still a definite possibility.

  Watch @chswx on Twitter as today unfolds. I’ll update here and Google+ periodically.

   
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  Jared Smith 8:14 am on February 23, 2012 Permalink
  Tags: lowcountry ( 2 ), record highs, severe weather   

  Record highs today, strong storms Friday 

  Very springlike day on tap for much of the East Coast (we’re going to benefit up here in Northern VA, too); looks like 80s aren’t out of the question in the Southeast. It will be a crazy nice day for this time of year, so enjoy it as best as you can.

  The Storm Prediction Center has held on to a slight risk (15% probability) of severe storms tomorrow for central and eastern SC (including the coast) (click to enlarge):

  

  Here is the relevant bit from NWS Charleston’s 7am forecast discussion:

  THE BIGGEST ISSUE FOR FRIDAY IS THE POTENTIAL FOR SEVERE WEATHER.
  THE MOST CONCERNING FACTOR IS THE STRONG LOW LEVEL JET THAT WILL BE
  IN PLACE AHEAD OF THE COLD FRONT…WITH 850MB WINDS POSSIBLY AS
  STRONG AS 50-55 KT OVER PARTS OF THE AREA ACCORDING TO SOME OF THE
  LATEST GUIDANCE. IN ADDITION…STRONG MOISTURE ADVECTION WITH A DEEP
  SOUTHWEST FLOW IN PLACE WILL ALLOW DEWPOINT VALUES TO RISE INTO THE
  LOWER TO MID 60S ACROSS THE AREA. A FRONTAL PASSAGE LATER IN THE DAY
  WILL ALSO ALLOW GREATER DESTABILIZATION TO OCCUR. DESPITE THESE
  FAVORABLE CONDITIONS…THIS IS BY NO MEANS A LIKELY SEVERE WEATHER
  EVENT. PERHAPS THE GREATEST LIMITING FACTOR CONTINUES TO BE THE
  POTENTIAL FOR EXTENSIVE CLOUD COVER OVER THE AREA AHEAD OF THE COLD
  FRONT WHICH COULD LIMIT THE AVAILABLE INSTABILITY. ALSO…MID LEVEL
  LAPSE RATES REMAIN RATHER POOR. HAVING SAID ALL OF THIS…AT THE
  VERY LEAST ISOLATED SEVERE THUNDERSTORMS CANNOT BE RULED OUT…WITH
  DAMAGING WIND GUSTS THE PRIMARY THREAT. WILL THEREFORE KEEP MENTION
  IN THE HAZARDOUS WEATHER OUTLOOK. EVEN IF SEVERE WEATHER DOES NOT
  OCCUR…DEEP MIXING WILL RESULT IN STRONG WIND GUSTS UPWARDS OF
  30-35 MPH AT TIMES DURING THE DAY.

  Cloud cover and the resultant lack of instability has done in many severe threats in the Southeast so far this winter. The NAM and GFS, thanks to timing differences, have different opinions on available instability. The 12z NAM (coming in as I write this) is really enthusiastic about instability, with max CAPE of 1200+ J/kg over the Midlands at 1PM tomorrow. I’m going to consider the NAM an outlier for now; let’s see what the 12z run of the global models say about this first. They are much more conservative on instability (but also much slower). I agree with NWS Charleston that this won’t be a widespread severe event, but there’s still time for things to change. Good to continue to stay vigilant on this front.

  Regardless of instability, it does look like quite a rainmaker — we need all we can get given drought conditions across SC. Here’s the five-day QPF chart as of this morning — it does look like the heaviest rain will remain well inland but we won’t be shut out completely:

  

  More later today or tomorrow depending on how busy things get here.

   
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  Jared Smith 8:08 am on February 22, 2012 Permalink
  Tags: charleston ( 3 ), sc lowcountry ( 19 ), severe weather   

  Severe risk on Friday for Lowcountry struggling to come into focus 

  

  I’m watching this severe weather risk for Friday closely as a cold front is expected to push through the area in the Friday/Saturday timeframe, bringing some more needed rain but also possibly bringing a damaging wind threat. SPC was pretty gangbusters about it yesterday, coming in with a 30% risk; they’ve since dialed this back to about 15% given significant timing differences in the models (about 8-12 hours, which is the difference between a frontal passage during peak heating and overnight). Available instability is certainly the question, which has been a recurring theme for all of this winter’s severe weather threats so far.

  From NWS Charleston’s forecast discussion this morning:

  DEEP MOISTURE AND FORCING FROM THE RIGHT REAR QUADRANT OF A 125+ KT
  UPPER LEVEL JET WILL SUPPORT SCATTERED TO NUMEROUS SHOWERS ACROSS
  THE AREA BY FRIDAY AFTERNOON ALONG WITH ISOLATED THUNDERSTORMS. WEAK
  LAPSE RATES AND LIMITED INSTABILITY ARE BOTH NEGATING FACTORS FOR
  ANY SEVERE THUNDERSTORMS…BUT GIVEN WHAT COULD BE IMPRESSIVE LOW
  LEVEL WIND FIELDS IN ADVANCE OF THE FRONT…THERE CERTAINLY IS A
  MARGINAL DAMAGING WIND THREAT AND SPC HAS THE ENTIRE FORECAST AREA
  IN A SLIGHT RISK. IF THE FRONT COMES THROUGH DURING THE DAY THAT IS
  CERTAINLY MORE FAVORABLE TIMING FOR SEVERE WEATHER…BUT IT SEEMS AS
  IF THE ECMWF IS THE MOST ROBUST BUT ITS FRONTAL TIMING IS AT NIGHT.
  WHILE NOT TOTALLY CONVINCED THAT A SEVERE WEATHER EVENT IS GOING TO
  BE A BIG CONCERN ON FRIDAY…WILL ADD MENTION TO THE HAZARDOUS
  WEATHER OUTLOOK GIVEN THE NON-ZERO POTENTIAL.

  Will continue to monitor trends as needed as this situation is still very fluid. Going to try to get an update out later today with the 12z global model runs.

   
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  Jared Smith 11:56 am on August 21, 2011 Permalink
  Tags: dc, northern va, severe thunderstorm watch 794, severe weather   

  Severe Thunderstorm Watch 794 is now up until 9PM for DC and the suburbs.

   
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  Jared Smith 11:01 am on August 21, 2011 Permalink
  Tags: northern va/dc ( 3 ), severe weather, weather watch   

  A convective watch is likely up in the Capital Region this afternoon: http://www.spc.noaa.gov/products/md/md2030.html

   
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  Jared Smith 5:12 pm on August 20, 2011 Permalink
  Tags: charleston ( 3 ), sc lowcountry ( 19 ), severe weather, summerville   

  

  Charleston radar at 6:09 PM.

  Afternoon thunderstorms becoming severe with a damaging wind threat this afternoon in the Charleston area. I’m updating @chswx with warnings and storm reports as they come across.