Lake-effect snow is produced during cooler atmospheric conditions when a cold air mass moves across long expanses of warmer lake water, warming the lower layer of air which picks up water vapor from the ...
The NWS Wind Chill Temperature (WCT) index uses advances in science, technology, and computer modeling to provide an accurate, understandable, and useful formula for calculating the dangers from winter ...
WRN – Winter Weather Warnings, Watches and Advisories
Winter Weather Warnings, Watches and Advisories
Winter weather related Warnings, Watches and Advisories are issued by your local National Weather Service office. Each office knows the local area and will ...
SPC AC 221712 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1112 AM CST Wed Nov 22 2017 Valid 231200Z - 241200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... A few thunderstorms are expected across the Florida Peninsula on Thursday. ...DISCUSSION... An upper-level trough will move eastward across the eastern U.S. on Thursday as an upper-level ridge remains over the southwestern and central states. At the surface, a low will move across the far northeastern Gulf of Mexico. A moist airmass will be in place across the Florida Peninsula where a few thunderstorms will be possible Thursday afternoon. However, no severe threat is expected with this activity. ..Broyles.. 11/22/2017 CLICK TO GET WUUS02 PTSDY2 PRODUCT NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0700Z
SPC AC 221607 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1007 AM CST Wed Nov 22 2017 Valid 221630Z - 231200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... No severe thunderstorms are forecast over the US today. ...Florida... A well-defined upper trough is moving across the western Gulf of Mexico today. This feature will produce scattered showers and thunderstorms over the eastern Gulf and the central/southern FL peninsula today and tonight. The more robust convection will stay west of FL through this forecast period, before moving inland on Thursday. No organized severe storms are forecast today or tonight. ..Hart/Bunting.. 11/22/2017 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z
…SMALL CRAFT ADVISORY REMAINS IN EFFECT UNTIL 3 PM EST THIS AFTERNOON… * WINDS…NORTHWEST 15 TO 25 KNOTS DIMINISHING TO TO 10 TO 20 KNOTS. * WAVES… WAVES 4 TO 6 FEET SUBSIDING TO 1 TO 3 FEET.
Vermilion to Avon Point OH (LEZ145)
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
Day 4-8 Severe Weather Outlook Issued on Nov 22, 2017
Updated: Wed Nov 22 07:13:02 UTC 2017
Sat, Nov 25, 2017 – Sun, Nov 26, 2017
Tue, Nov 28, 2017 – Wed, Nov 29, 2017
Sun, Nov 26, 2017 – Mon, Nov 27, 2017
Wed, Nov 29, 2017 – Thu, Nov 30, 2017
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.
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 AC 220551 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 1151 PM CST Tue Nov 21 2017 Valid 241200Z - 251200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are possible over the Florida Peninsula early in the day on Friday. Severe thunderstorms are not forecast. ...Synopsis... A potent shortwave trough will quickly move east across the Midwest/Great Lakes while a mid-level ridge amplifies over the western states ahead of an east Pacific mid-level trough. Thunderstorm activity will be associated with a weakening mid- to upper-level trough moving across FL and into the western Atlantic. Early day shower and thunderstorm activity is possible across the FL Peninsula as weak large-scale ascent overspreads the region. Weak instability will likely preclude intense thunderstorm development. Elsewhere, tranquil conditions are forecast for a large part of the CONUS. ..Smith.. 11/22/2017 CLICK TO GET WUUS03 PTSDY3 PRODUCT NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0830Z
SPC AC 220444 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1044 PM CST Tue Nov 21 2017 Valid 231200Z - 241200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... A few general thunderstorms are expected across the Florida Peninsula on Thursday. ...FL Peninsula... The main impetus and focus for thunderstorm development Thursday and Thursday night will be a slow-moving upper-level trough over the Gulf of Mexico. A weak area of low pressure will gradually develop from the central into the eastern Gulf with moist low-level trajectories emanating from the northwest Caribbean into the FL Peninsula vicinity. Buoyancy is forecast to lessen with northward extent away from the Gulf Stream/FL Straits. The latest NAM (22/00Z) showed a slightly stronger PV anomaly encroaching on the FL Gulf Coast during the overnight hours. Concurrent with this feature, stronger low-level mass response was depicted. However, time-lagged versions of the GFS, ECMWF, CMC, and UKMET all show a weaker low-level response. It seems plausible based on the NAM and a few convection-allowing models with NAM input that some risk for a strong thunderstorm or two would be possible over the Keys, Everglades, and perhaps along the immediate Gulf Coast south of Tampa Bay. Yet, this scenario seems unlikely given the model variability/consensus. For these reasons, will maintain a less than 5-percent severe risk for this outlook update. ..Smith.. 11/22/2017 CLICK TO GET WUUS02 PTSDY2 PRODUCT NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z