

Day 4-8 Severe Weather Outlook Issued on Jan 6, 2020 Updated: Mon Jan 6 14:14:02 UTC 2020 Day 4 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area No Risk Areas Forecast Day 5 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area 30 % 61,408 3,558,423 Shreveport, LA...Little Rock, AR...Tyler, TX...College Station, TX...Longview, TX... 15 % 97,929 17,223,980 Houston, TX...Dallas, TX...Austin, TX...Fort Worth, TX...Arlington, TX... Day 6 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area 15 % 185,044 21,640,891 Nashville, TN...New Orleans, LA...Atlanta, GA...Birmingham, AL...Baton Rouge, LA... Day 7 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area No Risk Areas Forecast Day 8 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area No Risk Areas Forecast D4 Thu, Jan 09, 2020 - Fri, Jan 10, 2020 D7 Sun, Jan 12, 2020 - Mon, Jan 13, 2020 D5 Fri, Jan 10, 2020 - Sat, Jan 11, 2020 D8 Mon, Jan 13, 2020 - Tue, Jan 14, 2020 D6 Sat, Jan 11, 2020 - Sun, Jan 12, 2020 (All days are valid from 12 UTC - 12 UTC the following day) Note: A severe weather area depicted in the Day 4-8 period indicates 15%, 30% or higher probability for severe thunderstorms within 25 miles of any point. PREDICTABILITY TOO LOW is used to indicate severe storms may be possible based on some model scenarios. However, the location or occurrence of severe storms are in doubt due to: 1) large differences in the deterministic model solutions, 2) large spread in the ensemble guidance, and/or 3) minimal run-to-run continuity. POTENTIAL TOO LOW means the threat for a regional area of organized severe storms appears unlikely (i.e., less than 15%) for the forecast day. Forecast Discussion ZCZC SPCSWOD48 ALL ACUS48 KWNS 061411 SPC AC 061411 Day 4-8 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 0811 AM CST Mon Jan 06 2020 Valid 091200Z - 141200Z CORRECTED TO ADD LABEL TO DAY 8 GRAPHIC ...DISCUSSION... A multi-day severe weather episode is expected across portions of the Arklatex into the Deep South vicinity on D5/Fri and D6/Sat. The ingredients for severe thunderstorms will begin to fall into place Day 4/Thu as an upper ridge spreads eastward across the eastern U.S. and a large-scale trough intensifies across the western states. At the surface, a strong surface pressure gradient will develop from the Midwest to the western Gulf Coast, allowing rich Gulf moisture to begin streaming northward across east TX and the lower MS Valley vicinity on Thursday. The warm sector will expand through the day on Friday from eastern OK/TX eastward across much of the TN Valley and Gulf Coast states. Surface dewpoints are expected to be impressive for this time of year, climbing into the mid 60s to low 70s as a deepening surface low shifts eastward across OK/TX on Friday. This will occur as the western trough ejects eastward into the southern Plains and an intense southerly low level jet overspreads the region. Forecast guidance also shows a weak EML emanating from the Mexican Plateau spreading over parts of the region, providing a weak cap that should limit warm sector convection initially. Confidence has increased that a strong vertical shear parameter-space will overlay a high-quality warm sector ahead of the ejecting trough and a southeastward-advancing cold front Friday afternoon through Friday night. As such, a 30% severe delineation has been included for parts of the Arklatex within the broader 15% severe probability area. On Day 6/Sat, severe thunderstorm potential is expected to continue into portions of the TN Valley and the northern Gulf Coast vicinity. Similar to Friday, intense shear parameters and adequate instability will exist across the region as the upper trough becomes more compact and lifts northeast across the mid/lower MS Valley to the OH Valley. 15% severe probabilities will be maintained at this time as questions remain with respect to how pristine the warm sector will remain over MS/AL and vicinity, as well as timing/location of key surface features. That being said, the overall pattern will support severe thunderstorms into Saturday evening across much of the Deep South vicinity. Confidence in severe potential beyond Day 6/Sat is low, though guidance suggests stormy conditions could return to parts of the Southeast on Monday/Monday night. ..Leitman.. 01/06/2020 CLICK TO GET WUUS48 PTSD48 PRODUCT Weather Topics:

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