Mesoscale Discussion 421

Issued

Apr 19, 2016, 8:45 PM CDT (01:45 UTC)

Expired

Apr 19, 2016, 11:15 PM CDT

In force

3 hr

Issued by

the Storm Prediction Center

Chance of a watch

20%

The San Angelo radar (KSJT), 66 km from the middle of the area, began a volume at 01:47 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

• Severe Thunderstorm Watch 98Apr 19, 10:00 PM CDT

126 
ACUS11 KWNS 200146
SWOMCD
SPC MCD 200145 
TXZ000-OKZ000-200415-

MESOSCALE DISCUSSION 0421
NWS STORM PREDICTION CENTER NORMAN OK
0845 PM CDT TUE APR 19 2016

AREAS AFFECTED...A LARGE PART OF TEXAS

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 200145Z - 200415Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...TSTM CLUSTERS EVOLVING ACROSS PORTIONS OF WRN/NRN TX AT
MID EVENING ARE FORECAST TO SPREAD ACROSS A LARGE PART OF TX THROUGH
THE LATE EVENING AND INTO THE EARLY OVERNIGHT. THIS ACTIVITY WILL
OFFER AN ISOLATED SVR WIND/HAIL RISK. WHILE CONVECTIVE TRENDS WILL
CONTINUE TO BE MONITORED...WW ISSUANCE IS PRESENTLY UNLIKELY.

DISCUSSION...MOISTURE-CHANNEL IMAGERY SUGGESTS THAT ANY SUBSTANTIVE
MID-LEVEL ASCENT IS ONLY GLANCING CONDITIONALLY UNSTABLE AIR SAMPLED
ACROSS PORTIONS OF CNTRL/WRN TX. SFC ANALYSIS AT 01Z PLACES A FRONT
ARCHING FROM NEAR WICHITA FALLS TO S OF LUBBOCK AND THEN INTO
E-CNTRL NM E OF CLOVIS. THAT PORTION OF THE BOUNDARY ACROSS WRN N TX
TO THE TX S PLAINS IS BEING ENHANCED BY ONGOING COLD-POOL
AMALGAMATION ASSOCIATED WITH A QUASI-LINEAR CONVECTIVE CLUSTER. A
DRYLINE INTERSECTS THE BOUNDARY AT A TRIPLE POINT ANALYZED SSW OF
LUBBOCK AND EXTENDS TO THE SWRN TX BIG BEND. THE DRYLINE IS
RETREATING WWD FOLLOWING INITIAL NOCTURNAL DECOUPLING OF THE
BOUNDARY LAYER. WHILE THE AFOREMENTIONED CONVECTIVE CLUSTER
CONTINUES BACKBUILDING TOWARD THE TRIPLE POINT...MORE ISOLATED
CONVECTION IS OCCURRING IN PROXIMITY TO THE DRYLINE SWD FROM THE
PERMIAN BASIN TO THE STOCKTON PLATEAU. MEANWHILE...A PERSISTENT
SUPERCELL CLUSTER IS NEARING THE RIO GRANDE RIVER. ALSO...FINAL
VISIBLE SATELLITE PICTURES OF THE DAY INDICATE MORE ISOLATED PATCHES
OF AGITATED CUMULUS WITHIN THE OPEN WARM/MOIST SECTOR...FROM WHICH
DEEPER CONVECTION HAS BLOSSOMED INVOF THE CONCHO VALLEY.

RECYCLED LOW-LEVEL MOISTURE REMAINS IN PLACE E OF THE DRYLINE AND
S/SE OF THE EFFECTIVE BOUNDARY...WITH 00Z RAOBS INDICATING
LOWEST-100-MB MEAN MIXING RATIOS AROUND 10-12 G/KG. MID-LEVEL LAPSE
RATES WILL BE SUFFICIENT TO MAINTAIN MUCAPE AROUND 500-1500 J/KG
INTO THE OVERNIGHT HOURS. THE DRT 00Z RAOB IS SAMPLING THE
BEST-DEFINED EML ACROSS THE AREA...SUPPORTING THE STRONGEST BUOYANCY
TOWARD THE RIO GRANDE RIVER. AFOREMENTIONED CONVECTION EVOLVING FROM
MULTIPLE FOCI WILL SPREAD EWD ACROSS THE FOREGOING AIR MASS THROUGH
THE LATE EVENING/EARLY OVERNIGHT HOURS. THIS ACTIVITY WILL
PRINCIPALLY BE SUSTAINED BY SUFFICIENTLY MOIST/UNSTABLE INFLOW
IMPINGING UPON LOCALLY UPSCALE-GROWING COLD POOLS AMID 30-45 KT OF
EFFECTIVE BULK SHEAR.

GIVEN THE AFOREMENTIONED BUOYANCY/SHEAR PARAMETER SPACE...ISOLATED
SVR HAIL ACCOMPANYING INCIPIENT CONVECTIVE STAGES AND MORE DISCRETE
CONVECTIVE MODES WILL BE POSSIBLE...AND A FEW SVR WIND GUSTS MAY
ALSO OCCUR WITH STRENGTHENING COLD POOLS. THIS WILL AFFECT A LARGE
PART OF CNTRL TX AND VICINITY. HOWEVER...GIVEN A TENDENCY FOR
NOCTURNAL COOLING TO SUPPORT GAINS IN BOUNDARY-LAYER STATIC
STABILITY AND MLCINH MAGNITUDE...ALONG WITH AN OVERALL DEARTH OF
DEEP/LARGE-SCALE ASCENT AND WEAK LOW-LEVEL FLOW SAMPLED BY AREA
VWPS...THE SVR-TSTM RISK SHOULD REMAIN ISOLATED. CONVECTIVE TRENDS
WILL CONTINUE TO BE MONITORED. IF A MORE WIDESPREAD SVR RISK WERE TO
EVOLVE WITH UPSCALE-GROWING CONVECTION...THEN WW-ISSUANCE
PROBABILITIES COULD INCREASE.

..COHEN/EDWARDS.. 04/20/2016

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...FWD...OUN...EWX...SJT...LUB...MAF...

LAT...LON   31160263 32890162 33839919 33929768 33369636 31599677
            30349790 29849972 29680134 29900249 31160263

Mesoscale Discussions in Texas, 2016Every mesoscale discussion in 2016

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.