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Southern/Central Plains Obs and Short Term Discussions


OKpowdah

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Looks like a major, slow-moving MCS is on tap for tomorrow through Friday. Would be wonderful for this to verify for W OK.

 

post-972-0-89248800-1374725426_thumb.gif

 

My secondary hope is for us to get decent storms that don't hit between 4-8am, but I've just about already conceded that one.

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2034z (2:34 Mountain Time) 6 miles NE of Two Buttes, Colorado.  NUMEROUS REPORTS OF TORNADO NEAR PROWERS AND BACA COUNTY LINE NORTHEAST OF TWO BUTTES. TORNADO HAS BEEN ON GROUND FOR AT LEAST 20 MINUTES.

 

totally unrelated radar image:  Dodge City radar,  wide mesocyclone near Garden City KS.

 

post-1182-0-66196500-1374799039_thumb.pn

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Significant flash flooding this morning across OKC metro and Norman.

4" at the Mesonet in North Norman, CoCoRaHS reports over 5" in the southern half of the city. Police advising drivers to stay off roads if possible. In late July of all times.... odd.

66126_10151593474714200_1786787621_n.jpg

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Watch out, SE Kansas. The 4km NAM is showing huge amounts of precipitation. The regular NAM is showing about 1-1.5" in the next 24 hours. It's already raining heavily around Emporia and Kansas City.  Some of Kansas saw heavy rain amounts over the weekend too.

 

post-1182-0-98970800-1375124629_thumb.gi

 

post-1182-0-25460100-1375124629_thumb.pn

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Very beneficial rainfall occurred across much of the eastern half of KS yesterday with widespread 3-7 inch rainfall totals... Unfortunately this will lead to moderate to major flooding for those areas that saw the heaviest rainfall... Also, saw on the KTOP LSR that in Southern Lyon County somebody measured receiving 5 inches of rain in an hour and 15 minutes, I don't think ive ever seen rainfall rates that high ever.

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Interesting severe weather setup for the first day of august for central, and south-central Nebraska... NAM is forecasting 0-1KM EHI values of 1 to 3, and 0-3KM EHI values of 5 to 8... Most of these high'ish numbers would appear to be a result from the relatively modest 0-1KM (100-200 m2s2) and 0-3KM (300-600 m2s2) Helicity Values, along with sufficient instability AOA 2000 J/KG in the lowest 0-70hPa AGL and 50kts of Bulk Shear. Main concern would be capping with a very strong cap immediately east of the best conditions, and it doesn't appear that any storms will go over this area until after dark which could inhibit the tornado potential. 

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Interesting severe weather setup for the first day of august for central, and south-central Nebraska... NAM is forecasting 0-1KM EHI values of 1 to 3, and 0-3KM EHI values of 5 to 8... Most of these high'ish numbers would appear to be a result from the relatively modest 0-1KM (100-200 m2s2) and 0-3KM (300-600 m2s2) Helicity Values, along with sufficient instability AOA 2000 J/KG in the lowest 0-70hPa AGL and 50kts of Bulk Shear. Main concern would be capping with a very strong cap immediately east of the best conditions, and it doesn't appear that any storms will go over this area until after dark which could inhibit the tornado potential. 

Good discussion. I see the SPC has introduced a 30% risk area tomorrow, along with some hatching. The NAM predicts a 300mb wind speed of 50 knots over some of this area. That would indicate that some of the 0-6 km shear values (or effective shear) may be 45-50 knots, which is a definite signal for higher severe weather potential. (250mb is over 60 knots.)

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Interesting severe weather setup for the first day of august for central, and south-central Nebraska... NAM is forecasting 0-1KM EHI values of 1 to 3, and 0-3KM EHI values of 5 to 8... Most of these high'ish numbers would appear to be a result from the relatively modest 0-1KM (100-200 m2s2) and 0-3KM (300-600 m2s2) Helicity Values, along with sufficient instability AOA 2000 J/KG in the lowest 0-70hPa AGL and 50kts of Bulk Shear. Main concern would be capping with a very strong cap immediately east of the best conditions, and it doesn't appear that any storms will go over this area until after dark which could inhibit the tornado potential. 

 

Those helicity values are certainly not modest.

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Solid area of high (3000-4000+ J/kg) SBCAPE (MLCAPE is also 2500-3000+ J/kg) along the dryline off the 00z NAM (valid 21z) in Western/Central NE tomorrow.

2qe.gif
 

If cells can fire maybe around 18z and propagate eastward into the following highly sheared environment, could be quite the interesting day (given moderately strong/substantially veering flow with height).

uw1.gif
 

Strong sfc wind response via pressure falls associated with leeside cyclogenesis near and east of the dryline contributing to the above impressive 0-3 km SRH.

b3m.gif

 

The 4 km WRF-NMM does not have anything in this area tomorrow afternoon/evening, FWIW.

 

The NAM does appear to have some convective parameterization issues via an MCS that it has running from morning through early afternoon that shows up on the 500 mb vorticity fields. Like I said above though, if we can get a few supercells to fire off the dryline maybe somewhere near North Platte's longitude, it could be an interesting localized event.

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Tornado watch coming for SW SD and much of western/central NE.

 

MESOSCALE DISCUSSION 1581   NWS STORM PREDICTION CENTER NORMAN OK   1253 PM CDT THU AUG 01 2013   AREAS AFFECTED...NEB...SWRN SD   CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY    VALID 011753Z - 012000Z   PROBABILITY OF WATCH ISSUANCE...95 PERCENT   SUMMARY...ISOLATED TO SCATTERED SUPERCELLS WILL FORM BY   MID-AFTERNOON WITH INITIAL PRIMARY RISKS OF VERY LARGE HAIL AND A   FEW TORNADOES. A WW WILL BE ISSUED WITHIN THE HOUR...WITH MODERATE   UNCERTAINTY OVER THE SPATIAL EXTENT OF AN INITIAL WW.   DISCUSSION...17Z SURFACE ANALYSIS PLACED A 1012 MB CYCLONE NEAR   BFF...WITH A QUASI-STATIONARY FRONT EXTENDING NEWD AND THEN E ACROSS   SRN SD. SURFACE-BASED CB/S HAVE FORMED ALONG THIS FRONT IN   SHANNON/BENNETT COUNTIES SD. ADDITIONAL CU DEVELOPMENT HAS BEEN   NOTED ALONG RESIDUAL OUTFLOW IN CNTRL NEB /CENTERED OVER VALLEY   COUNTY/. ALTHOUGH LARGE-SCALE FOR ASCENT IS NEBULOUS...CONTINUED   SURFACE HEATING WILL YIELD INCREASING DESTABILIZATION AND MINIMAL   CAPPING WITH SUSTAINED SURFACE-BASED TSTMS EXPECTED DURING THE   AFTERNOON /SUPPORTED BY RECENT HRRR RUNS/. STRONG DEEP-LAYER SHEAR   AND STEEP MID-LEVEL LAPSE RATES WILL BE QUITE FAVORABLE FOR   SUPERCELLS PRODUCING LARGE HAIL /SOME SIGNIFICANT/. VEERING OF THE   LOW-LEVEL WIND PROFILE ALONG WITH THE PRESENCE OF THE BOUNDARIES   WILL SUPPORT A RISK FOR A COUPLE OF TORNADOES AS WELL.   ..GRAMS/MEAD.. 08/01/2013
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