Jan 21, 2017 0100 UTC Day 1 Convective Outlook
Updated: Sat Jan 21 00:58:40 UTC 2017 (20170121 0100Z Day 1 shapefile | 20170121 0100Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Public Severe Weather Outlook

The SPC is forecasting ...Severe thunderstorms expected over parts of the overnight....   Please read the latest public statement about this event.  View What is a Watch? clip.

Categorical Graphic
20170121 0100 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 62,319 5,630,198 New Orleans, LA...Baton Rouge, LA...Mobile, AL...Jackson, MS...Metairie, LA...
SLIGHT 44,279 5,792,582 Houston, TX...Pasadena, TX...Beaumont, TX...Lake Charles, LA...Baytown, TX...
MARGINAL 39,969 5,157,177 Birmingham, AL...Montgomery, AL...Tuscaloosa, AL...Sugar Land, TX...The Woodlands, TX...
Probabilistic Tornado Graphic
20170121 0100 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
SIG SEVERE 34,129 4,093,832 New Orleans, LA...Baton Rouge, LA...Mobile, AL...Metairie, LA...Lafayette, LA...
10 % 34,040 4,090,664 New Orleans, LA...Baton Rouge, LA...Mobile, AL...Metairie, LA...Lafayette, LA...
5 % 46,383 2,890,981 Jackson, MS...Beaumont, TX...Lake Charles, LA...Port Arthur, TX...Pensacola, FL...
2 % 31,035 6,714,634 Houston, TX...Montgomery, AL...Pasadena, TX...Sugar Land, TX...The Woodlands, TX...
Probabilistic Damaging Wind Graphic
20170121 0100 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 % 53,740 5,463,205 New Orleans, LA...Baton Rouge, LA...Mobile, AL...Jackson, MS...Metairie, LA...
15 % 52,545 5,951,270 Houston, TX...Pasadena, TX...Beaumont, TX...Lake Charles, LA...Baytown, TX...
5 % 18,386 3,195,099 Montgomery, AL...Tuscaloosa, AL...Sugar Land, TX...The Woodlands, TX...Missouri City, TX...
Probabilistic Large Hail Graphic
20170121 0100 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 40,023 6,510,411 Houston, TX...Baton Rouge, LA...Pasadena, TX...Lafayette, LA...Beaumont, TX...
15 % 106,539 11,420,365 Houston, TX...New Orleans, LA...Baton Rouge, LA...Mobile, AL...Jackson, MS...
5 % 40,011 5,159,468 Birmingham, AL...Montgomery, AL...Tuscaloosa, AL...Sugar Land, TX...The Woodlands, TX...
   SPC AC 210058

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0658 PM CST Fri Jan 20 2017

   Valid 210100Z - 211200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   SOUTHERN AND CENTRAL LA/MS...AND SOUTHWEST AL...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS EXTENDING FROM
   SOUTHEAST TX ACROSS THE LOWER MS VALLEY INTO AL AND THE FL
   PANHANDLE...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   SLIGHT RISK...

   ...SUMMARY...
   Scattered severe storms are expected to continue developing this
   evening across southeast Texas, and spread across the lower
   Mississippi Valley and into Alabama and the Florida Panhandle
   tonight through Saturday morning. A few tornadoes, some of which
   could be strong, large hail, and damaging winds will all be
   possible.

   Reminder: This Day 1 Convective Outlook will be valid THROUGH 12Z
   Saturday (7 AM EST/6 AM CST). An upcoming Day 1 Convective Outlook
   will be issued around 06Z (1 AM EST/Midnight CST), which will be
   valid BEGINNING at 12Z Saturday, and continuing through 12Z Sunday.

   ...Southeast TX into the Lower MS Valley and Adjacent Gulf Coast
   States...
   A cluster of thunderstorms has developed across the Houston metro
   area over the past several hours along a sea breeze as large-scale
   ascent associated with an upstream shortwave trough overspreads this
   region. This activity is expected to continue northeastward/eastward
   across the lower Sabine River valley through the evening. Better
   low-level moisture characterized by mid 60s to lower 70s dewpoints
   currently resides near/along coastal LA/MS/AL and the western FL
   Panhandle. This moisture will likely move northward into central
   LA/MS/AL as an effective warm front through 12Z Saturday as a 40-50
   kt low-level jet strengthens across this region.

   Overall thinking regarding convective evolution through this
   evening/overnight and into early Saturday morning remains generally
   unchanged from the prior outlook. Upscale growth of initial
   cluster/discrete development in southeast TX/southwest LA appears
   probable given the strength of the low-level jet and large-scale
   ascent associated with a 120+ kt upper jet moving over the lower MS
   Valley. While large hail may be an initial threat given steep
   mid-level lapse rates, damaging winds would appear to be the greater
   concern with time as this line of thunderstorms moves eastward
   across southern/central LA/MS and into southwest AL overnight. Some
   adjustments have been made to the 30% wind probabilities and
   corresponding Enhanced Risk area to account for a slightly faster
   eastward progression of this line per most recent convection-
   allowing model guidance.

   In addition, a 10% tornado probability area has been included for
   parts of southern LA/MS and far southwest AL, including the Mobile
   metro area. There will be a greater potential for discrete supercell
   development with southward extent ahead of the previously mentioned
   line of thunderstorms. Forecast soundings across this region suggest
   that any tornadoes that do form in this environment could be strong
   with southwesterly winds around 850 mb strengthening to around 50 kt
   overnight, and corresponding effective SRH in excess of 300 m2/s2.

   For additional information on the near-term severe threat (through
   about 0230Z) across southeast TX through southwest LA, see recently
   issued Mesoscale Discussion 80.

   ..Gleason.. 01/21/2017

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z