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Severe POSS SEVERE WX CENTRAL ALABAMA 06/20/2019

PEA_RIDGE

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NWS BMX LATEST AFD

THURSDAY.

A CONSISTENT SYNOPTIC SIGNAL HAS EXISTED THE PAST FEW DAYS WITH
REGARDS TO AN AMPLIFYING SHORTWAVE MOVING ACROSS THE GREAT PLAINS
SOUTHEASTWARD INTO THE MID-MISSISSIPPI RIVER VALLEY OVERNIGHT
WEDNESDAY. POSITIONING OF FAVORABLE MID-LEVEL FLOW AROUND THE BASE
OF THE TROUGH SUGGESTS 40-50 KTS OF WESTERLY WINDS AT 500 MB
ACROSS OUR AREA ON THURSDAY AS MID-LEVEL LAPSE RATES STEEPEN
(~6.5-7.5 C/KM) FROM THE SOUTHERN PLAINS. WITH PRE-EXISTING LOW-
LEVEL MOISTURE IN PLACE, AFTERNOON HEATING IS EXPECTED TO
DESTABILIZE THE TROPOSPHERE SUCH THAT 2,500-3,500 J/KG SBCAPE IS

POSSIBLE WITH ~40 KTS EFFECTIVE BULK SHEAR. SEVERE WEATHER IS
POSSIBLE AS A RESULT OF THESE SHEAR/INSTABILITY VALUES, AS WELL AS
HEIGHT FALLS & COOLING TEMPERATURES ALOFT ASSOCIATED WITH THE
SHORTWAVE TROUGH.

FORECAST HODOGRAPHS SUGGEST QUASI-UNIDIRECTIONAL FLOW WITH MEAN
WINDS OUT OF THE WEST, WITH STORM MOTIONS SOUTH OF EAST. ENOUGH
INGESTION OF STORM-RELATIVE HELICITY IN THE 0-3 KM LAYER SUGGESTS
DISCRETE UPDRAFTS CAPABLE OF DEVELOPING MESOCYCLONES, ESPECIALLY

IF SURFACE WIND VECTORS CAN BACK MORE SOUTHWESTERLY. THIS FACTOR,
AS WELL AS 500 MB TEMPERATURES APPROACHING -10 C, SUGGESTS SEVERE
HAIL WOULD BE A THREAT AS WELL AS DAMAGING WIND GUSTS. FORECAST
UNCERTAINTY OF ANTECEDENT CONVECTIVE EVOLUTION AND POSITIONING OF
MESOSCALE FEATURES (SUCH AS SURFACE BOUNDARIES) LIMITS ANY
PREDICTABILITY FOR SPECIFIC AREAS UNDER GREATER PROBABILITY FOR
SEVERE WEATHER. (FOR EXAMPLE, AN UNCONTAMINATED ATMOSPHERE WILL
HAVE BETTER CHANCES OF SEVERE WEATHER COVERAGE THAT AFTERNOON
VERSUS ONGOING CONVECTION DURING THE MORNING LIMITING AVAILABLE
INSTABILITY OVER PARTICULAR AREAS.) THUS, FOR NOW, A MENTION OF
SEVERE WEATHER WILL BE ADDED TO THE HWO WITH LARGE HAIL AND
DAMAGING WINDS THE PRIMARY THREATS ACROSS ALL OF CENTRAL ALABAMA
UNTIL FURTHER FORECAST REFINEMENTS ARE MADE. AT THIS TIME, A
TORNADO THREAT CANNOT BE RULED OUT AS THERE ARE VARYING SCENARIOS
FOR HOW THIS SYSTEM WILL EVOLVE
 
Definitely some EML advection, sounding supports very large hail as well, also got a sickle shaped hodo, and solid critical angle right here, sounding is very similar to soundings ahead of that Dallas MCS that knocked a crane down days ago, damaging winds, embedded large hail and some tornadoes would be possible with this sounding, good thing atm this looks more linear although wind profiles aren’t far from supporting supercells out ahead but there is a Capping inversion
F082A572-C21D-4BE2-9121-91461D46B3D6.png
 

Mesoscale Discussion 1149
NWS Storm Prediction Center Norman OK
0958 PM CDT Wed Jun 19 2019

Areas affected...central and northern MS...parts of western
TN...northwest and north-central AL

Concerning...Severe potential...Severe Thunderstorm Watch likely

Valid 200258Z - 200400Z

Probability of Watch Issuance...95 percent

SUMMARY...A bow echo over southeastern AR is rapidly moving east at
55kt and will exit severe thunderstorm watch 405 around 11pm CDT. A
new severe thunderstorm watch will be needed for MS, parts of
western TN, and into northwest and north-central portions of AL.

DISCUSSION...Radar mosaic shows a bow echo over southeastern AR and
a cluster of severe thunderstorms over central AR. The central AR
cluster yielded gusts of 58kt at KLRF and 56kt at KLIT in the Little
Rock metro. Strong west-southwesterly flow increasing with height
will favor storm organization when combined with a moist boundary
layer (surface dewpoints in the lower 70s) and moderate buoyancy.
Expecting a continued risk for severe gusts (60-75kt) with the bow
echo and severe gusts potentially affecting the greater Memphis area
around 1am CDT. The highest potential and greatest concentration of
severe gusts will likely focus with the mature bow echo as it
rapidly moves into north-central MS during the late evening/early
overnight period.

..Smith/Edwards.. 06/20/2019

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...OHX...BMX...HUN...MEG...JAN...

LAT...LON 33219035 35419050 35458801 34798678 33938656 32978695
32658776 32669061 33219035
 
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