Mar 28, 2017 2000 UTC Day 1 Convective Outlook
Updated: Tue Mar 28 20:07:57 UTC 2017 (20170328 2000Z Day 1 shapefile | 20170328 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170328 2000 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MODERATE 20,139 417,407 Wichita Falls, TX...Lawton, OK...Altus, OK...Burkburnett, TX...Vernon, TX...
ENHANCED 63,292 2,356,487 Oklahoma City, OK...Abilene, TX...Norman, OK...San Angelo, TX...Edmond, OK...
SLIGHT 84,795 11,815,226 Dallas, TX...Austin, TX...Fort Worth, TX...Tulsa, OK...Arlington, TX...
MARGINAL 169,587 16,756,363 San Antonio, TX...Charlotte, NC...Virginia Beach, VA...Raleigh, NC...Norfolk, VA...
Probabilistic Tornado Graphic
20170328 2000 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
10 % 28,141 693,701 Abilene, TX...Wichita Falls, TX...Lawton, OK...Duncan, OK...Altus, OK...
5 % 82,013 11,053,164 Dallas, TX...Austin, TX...Fort Worth, TX...Oklahoma City, OK...Arlington, TX...
2 % 48,192 3,093,535 San Antonio, TX...Lubbock, TX...San Marcos, TX...New Braunfels, TX...Muskogee, OK...
Probabilistic Damaging Wind Graphic
20170328 2000 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
30 % 60,379 2,635,297 Oklahoma City, OK...Abilene, TX...Norman, OK...Wichita Falls, TX...Lawton, OK...
15 % 83,735 11,416,898 Dallas, TX...Austin, TX...Fort Worth, TX...Tulsa, OK...Arlington, TX...
5 % 166,778 16,060,008 San Antonio, TX...Charlotte, NC...Virginia Beach, VA...Raleigh, NC...Norfolk, VA...
Probabilistic Large Hail Graphic
20170328 2000 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SIG SEVERE 61,765 992,757 Abilene, TX...Wichita Falls, TX...Lawton, OK...San Angelo, TX...Duncan, OK...
45 % 20,139 417,407 Wichita Falls, TX...Lawton, OK...Altus, OK...Burkburnett, TX...Vernon, TX...
30 % 42,549 710,354 Abilene, TX...San Angelo, TX...Duncan, OK...Brownwood, TX...Mineral Wells, TX...
15 % 77,047 9,151,620 Dallas, TX...Fort Worth, TX...Oklahoma City, OK...Arlington, TX...Plano, TX...
5 % 167,020 17,429,962 San Antonio, TX...Austin, TX...Virginia Beach, VA...Tulsa, OK...Raleigh, NC...
   SPC AC 282007

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0307 PM CDT Tue Mar 28 2017

   Valid 282000Z - 291200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS WESTERN
   NORTH TX AND SOUTHWEST OK...

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM CENTRAL OK
   TO THE EDWARDS PLATEAU OF SOUTHWEST TX...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
   SOUTHERN PLAINS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
   SOUTHERN PLAINS INTO PARTS OF EAST AND NORTHEAST NM...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS VA AND
   NC...

   ...SUMMARY...
   Numerous severe storms are expected across the southern Great Plains
   including parts of Texas and Oklahoma, especially late this
   afternoon and evening. Very large hail, damaging winds, and
   tornadoes are likely.

   ...Southern Plains...
   Previous forecast remains valid as initial severe storms have
   developed earlier this afternoon at the triple point in west-central
   TX near LBB and southward along the dryline.  Given trends/evolution
   of these storms and placement of the dryline per mesoscale analysis
   extending southwest into Pecos to Brewster counties, the Marginal
   and Slight risk areas and the general thunderstorm line have been
   shifted west.  The rest of the southern extent of the severe
   probabilities and overall severe-weather threat remains valid for
   this forecast period.

   Meanwhile, ongoing storm interactions of discrete supercells
   extending from the TX counties of Floyd to western Kent to Howard
   per radar imagery would suggest some diminishing trend in the threat
   for a greater coverage of hail.  However, ongoing poleward
   destabilization (moderate instability into northwest TX) combined
   with strong effective bulk shear suggests the moderate risk for hail
   (some very large) remains valid at this time.  The enhanced tornado
   risk persists across northwest TX into southwest OK.  

   Farther north, the Enhanced risk and significant hail threat have
   been trimmed some across parts of the southeast and south extension
   of the TX Panhandle, based  on trends in radar imagery.

   ...East-central and northeast NM...
   The marginal severe risk area has been expanded some across
   east-central and northeast NM as a midlevel impulse moves north
   across eastern NM this afternoon into the early evening.  Cooling
   500-mb temperatures/steepening midlevel lapse rates with this
   impulse and height falls ahead of the approaching synoptic trough
   will support additional thunderstorm development into the early
   evening.  Marginal instability should limit the overall coverage of
   severe storms, with isolated hail and/or locally strong wind gusts
   the primary threats.  Reference Mesoscale Discussion 354 for
   additional short-term details.

   ...VA/NC...
   The forecast remains valid for a marginal severe-weather threat this
   afternoon with overall risk diminishing by early evening.  No
   changes needed across this region in the convective outlook. 
   Reference Mesoscale Discussion 352 for additional short-term
   details.

   ..Peters.. 03/28/2017

   .PREV DISCUSSION... /ISSUED 1130 AM CDT Tue Mar 28 2017/

   ...Southern Plains...
   A combination of 12Z upper-air analysis and water vapor satellite
   imagery features an east/southeastward-digging shortwave trough over
   southeast AZ/southwest NM at late morning, with a preceding belt of
   40-50 kt mid-level southwesterly winds overspreading eastern NM and
   west TX. These south-southwesterly mid-level winds will continue to
   advect a stout elevated mixed layer east-northeastward today atop an
   increasingly moist sector ahead of a dryline and upstream Pacific
   front. Regional 12Z soundings and upper-air analysis featured 7.7+
   C/km 700-500mb lapse rates across all of west TX, while around 14
   g/kg mean mixing ratios were noted at Del Rio and Corpus Christi TX,
   with 850 mb dewpoints of 12C+ as far north as Midland/Dallas-Fort
   Worth.

   Initially, increasing elevated storms may pose a severe hail risk
   early this afternoon across the TX panhandle/northwest TX. Reference
   Mesoscale Discussion 350 for additional short-term details.

   To the east of the dryline, low clouds remain prevalent at late
   morning, although a relatively narrow upper dry slot continues to
   steady approach west Texas and low clouds are steadily eroding
   across the Permian Basin vicinity. As additional moistening/heating
   occurs, moderate to strong destabilization with minimal inhibition
   is expected particularly near the surface low/warm
   front/dryline-related triple point across the TX south Plains/low
   rolling plains, southward to near/east of the dryline as it extends
   into the Permian Basin vicinity. Here, aforementioned moisture/lapse
   rates should yield MLCAPE in excess of 2500 J/kg. 

   Current thinking is that at least isolated surface-based severe
   storms will develop near the triple point vicinity by around
   mid/late afternoon, with additional development possible near the
   dry line. Although current (late morning) cloud cover casts some
   uncertainty, a somewhat displaced corridor of warm-conveyor-related
   storms are expected by late afternoon/early evening farther east
   across additional parts of western north TX into southwest OK.
   Initially discrete supercell mode should favor large hail and
   localized severe wind gusts. Although the upper flow pattern will
   become increasingly meridional with time (with general tendency of
   backing mid-level winds), and a more linear/mixed mode should evolve
   during the evening, enlarged low-level hodographs will support the
   potential for tornadoes through at least early/mid-evening. Linear
   bands should accelerate northeast into southern/central Oklahoma
   during the evening, with attendant risks for damaging winds, hail,
   and a couple tornadoes.

   Farther south across west-central/southwest TX including the Edwards
   Plateau, initially isolated late afternoon/early evening storms near
   the dryline should become widespread in coverage during mid/late
   evening as the Pacific front merges and overtakes the dryline. This
   should result in a predominant risk to large hail transitioning
   quickly to strong to severe wind gusts. An extensive squall line
   will likely evolve east overnight with at least an isolated severe
   risk spreading eastward into central TX including the Hill
   Country/Interstate 35 corridor late tonight.

   ...VA/NC...
   A dampening shortwave impulse over WV will shift off the VA/NC coast
   by mid-evening. Ongoing showers and isolated storms will subdue
   destabilization early in the diurnal heating cycle. However, by late
   afternoon, widely scattered storms should develop ahead of the
   impulse. Increased veering of the wind profile with height should
   foster mainly discrete cells, some of which should weakly rotate.
   Isolated severe hail and damaging winds will be possible.

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