SPC Nov 22, 2017 1730 UTC Day 2 Convective Outlook


SPC Nov 22, 2017 1630 UTC Day 1 Convective Outlook


SPC Nov 22, 2017 1300 UTC Day 1 Convective Outlook

 SPC AC 221237 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0637 AM CST Wed Nov 22 2017 Valid 221300Z - 231200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Inland thunderstorm chances through tomorrow morning appear confined to parts of Florida. ...Synopsis... In the mean, the upper-air pattern will maintain a western ridge and eastern trough through the period. This will keep substantial low-level moisture and instability shunted out of the great majority of the U.S. mainland, except for portions of Florida. A basal shortwave trough -- evident in moisture-channel imagery over parts of the northwestern Gulf and the lower Rio Grande Valley of TX -- is forecast to dig southeastward across the western/central Gulf through the period and become less positively tilted. As this occurs, associated thunder risks over the Gulf should retreat farther away from the lower TX coast. By 12Z, the perturbation should align closely with the southern part of larger-scale trough position, from near the Mississippi River mouth across the eastern Bay of Campeche. Slightly confluent southwest flow aloft will result across FL, while a surface frontal-wave cyclone moves from the south-central to east-central Gulf along a residual baroclinic zone. Meanwhile, a strong northern-stream shortwave trough -- now located from southern ON across WV -- is expected to pivot east- northeastward to western New England and Long Island by 00Z, then well east of Maine by 12Z. Large-scale ascent preceding this feature will support a favorable environment for thunder well offshore from Delmarva and Long Island, where heat fluxes from ocean to boundary layer contribute the most low-level instability. ...FL... Isolated to widely scattered thunderstorms may develop during the most strongly heated diurnal cycle across parts of the southern peninsula, where boundary-layer theta-e will remain relatively maximized. Forecast soundings suggest peak MLCAPE 500-1000 J/kg but amidst low-level weaknesses of both low-level flow and shear. Given that factor and lack of more robust buoyancy, organized severe is not anticipated. Another round of thunderstorms may affect northwestern FL and adjacent waters late in the overnight period -- largely after about 09Z. This should occur as large-scale ascent and frontogenetic forcing ahead of the shortwave trough cross over suitably high-theta-e low-level air, near and just north of the surface front. ..Edwards.. 11/22/2017 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z

SPC Nov 22, 2017 Day 4-8 Severe Weather Outlook

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Day 4-8 Severe Weather Outlook Issued on Nov 22, 2017
Updated: Wed Nov 22 07:13:02 UTC 2017
D4 Sat, Nov 25, 2017 – Sun, Nov 26, 2017 D7 Tue, Nov 28, 2017 – Wed, Nov 29, 2017
D5 Sun, Nov 26, 2017 – Mon, Nov 27, 2017 D8 Wed, Nov 29, 2017 – Thu, Nov 30, 2017
D6 Mon, Nov 27, 2017 – Tue, Nov 28, 2017 (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 220711 SPC AC 220711 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0111 AM CST Wed Nov 22 2017 Valid 251200Z - 301200Z ...DISCUSSION... The mid-upper-level flow will continue to be dominated by a west-to-east, ridge-trough pattern across the United States. The continued northwest flow across the eastern United States will maintain/reinforce the already dry airmass. By late weekend the mid-level pattern should break down with the arrival of a more substantial trough moving across the country. As this trough moves into the Plains during the Day 6-8 time frame, surface cyclogenesis in the central Plains will allow low-level moisture to be drawn northward ahead of a surface cold front. Despite the likely presence of strong tropospheric shear associated with this trough, concerns abound regarding the depth and quality of moisture return. This leads to considerable uncertainties regarding thunderstorm initiation, timing, duration, and even location. Thus predictability of any severe potential remains too low. ..Marsh/Smith.. 11/22/2017 CLICK TO GET WUUS48 PTSD48 PRODUCT 


SPC Nov 22, 2017 0830 UTC Day 3 Severe Thunderstorm Outlook


SPC Nov 22, 2017 0700 UTC Day 2 Convective Outlook

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