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WDT HAZARDOUS WEATHER OUTLOOK 9/4/2017€¦ · Threat Legend Orange –Strong to Severe...

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Threat Legend Orange – Strong to Severe Thunderstorms Possible Red – Significant Severe Thunderstorm Threat Purple – Severe Weather Outbreak (Day 1 and 2 Only) Green – Excessive Rainfall Blue – Significant Snow/Ice Day 1 Threat Regions Map Day 2 Threat Regions Map WDT HAZARDOUS WEATHER OUTLOOK 9/4/2017 Days 1 – 2 (Short Term) Threat Summary DAY 1 MIDWEST/OHIO RIVER VALLEY: STRONG TO SEVERE THUNDERSTORMS POSSIBLE ALONG AND AHEAD OF A COLD FRONT SOUTH-CENTRAL ARIZONA: STRONG TO MARGINALLY SEVERE THUNDERSTORMS POSSIBLE FROM TROPICAL STORM LIDIA REMNANTS DAY 2 NORTHEAST: STRONG TO SEVERE THUNDERSTORMS POSSIBLE ALONG AND AHEAD OF A COLD FRONT
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Page 1: WDT HAZARDOUS WEATHER OUTLOOK 9/4/2017€¦ · Threat Legend Orange –Strong to Severe Thunderstorms Possible Red –Significant Severe Thunderstorm Threat Purple –Severe Weather

Threat LegendOrange – Strong to Severe Thunderstorms PossibleRed – Significant Severe Thunderstorm ThreatPurple – Severe Weather Outbreak (Day 1 and 2 Only)Green – Excessive Rainfall

Blue – Significant Snow/Ice

Day 1 Threat Regions Map Day 2 Threat Regions Map

WDT HAZARDOUS WEATHER OUTLOOK 9/4/2017

Days 1 – 2 (Short Term) Threat Summary

DAY 1MIDWEST/OHIO RIVER VALLEY: STRONG TO SEVERE THUNDERSTORMS POSSIBLE ALONG AND AHEAD OF A COLD FRONT

SOUTH-CENTRAL ARIZONA: STRONG TO MARGINALLY SEVERE THUNDERSTORMS POSSIBLE FROM TROPICAL STORM LIDIA REMNANTS

DAY 2 NORTHEAST: STRONG TO SEVERE THUNDERSTORMS POSSIBLE ALONG AND AHEAD OF A COLD FRONT

Page 2: WDT HAZARDOUS WEATHER OUTLOOK 9/4/2017€¦ · Threat Legend Orange –Strong to Severe Thunderstorms Possible Red –Significant Severe Thunderstorm Threat Purple –Severe Weather

Day 3

Day 6

WDT THREATS AT A GLANCE – Days 3 Through 7 9/4/2017

Day 4

Day 5

Threat LegendOrange – Strong to Severe Thunderstorms PossibleRed – Significant Severe Thunderstorm ThreatPurple – Severe Weather Outbreak (Day 1 and 2 Only)Green – Excessive Rainfall

Blue – Significant Snow/Ice

Day 7

Page 3: WDT HAZARDOUS WEATHER OUTLOOK 9/4/2017€¦ · Threat Legend Orange –Strong to Severe Thunderstorms Possible Red –Significant Severe Thunderstorm Threat Purple –Severe Weather

Threat LegendOrange – Strong to Severe Thunderstorms PossibleRed – Significant Severe Thunderstorm ThreatPurple – Severe Weather Outbreak (Day 1 and 2 Only)Green – Excessive Rainfall

Blue – Significant Snow/Ice

Day 1 – Monday Threat Assessments and Morning Frontal Analysis Threat Region Discussion:

Midwest/Ohio River Valley: By the late afternoon and into the evening hours of Monday, thunderstorm development is likely along and ahead of a southeastward moving cold front. High dewpoint values and strong daytime heating will act to provide a moist and very unstable environment across this region. These conditions will act to allow strong to severe thunderstorm development along and ahead of the cold front. Primary hazards will be strong to severe wind gusts, hail, frequent lightning, and moderate to heavy rainfall. In addition, the possibility for an isolated tornado or two cannot be ruled out.

South-Central Arizona: Remnants from Tropical Storm Lidia will leave behind a moist and favorable environment for showers and thunderstorms to develop within this region during the afternoon hours. Although severity is expected to remain marginal, the threat for strong to marginally severe wind gusts within any stronger storm that develops is possible.

Page 4: WDT HAZARDOUS WEATHER OUTLOOK 9/4/2017€¦ · Threat Legend Orange –Strong to Severe Thunderstorms Possible Red –Significant Severe Thunderstorm Threat Purple –Severe Weather

Threat LegendOrange – Strong to Severe Thunderstorms PossibleRed – Significant Severe Thunderstorm ThreatPurple – Severe Weather Outbreak (Day 1 and 2 Only)Green – Excessive Rainfall

Blue – Significant Snow/Ice

Day 2 – Tuesday Threat Assessments and Morning Frontal Analysis Threat Region Discussion:

Northeast: As the low-pressure system continues to move eastward, and the cold front moves further toward the east and southeast, showers and some strong to severethunderstorms will be likely along and ahead of the front. In the Northeast, where the potential for severe weather is likely, strong to severe wind gusts and hail are possible threats. In addition, frequent lightning and moderate to heavy rainfall will also be possible.

A stationary front will extend westward from the southern end of the cold front and bring the possibility for precipitation and general thunderstorms across the western Ohio River Valley and Southern Plains. Further west, an area of high pressure will continue to build and move southeastward.

Page 5: WDT HAZARDOUS WEATHER OUTLOOK 9/4/2017€¦ · Threat Legend Orange –Strong to Severe Thunderstorms Possible Red –Significant Severe Thunderstorm Threat Purple –Severe Weather

Threat LegendOrange – Strong to Severe Thunderstorms PossibleRed – Significant Severe Thunderstorm ThreatPurple – Severe Weather Outbreak (Day 1 and 2 Only)Green – Excessive Rainfall

Blue – Significant Snow/Ice

Day 3 – Wednesday Threat Assessments and Morning Frontal Analysis Threat Region Discussion:

Mid-Atlantic: The cold front is forecast to continue to move east-southeastward and will bring showers and general thunderstorms along the eastern CONUS. However, across the Mid-Atlantic region where high dewpoint values ahead of the front will lie may allow thedevelopment of strong to marginally severe thunderstorms on Wednesday. Primary hazards across this region appear to be strong to marginally severe wind gusts, frequent lightning, and heavy to excessive amounts of rainfall. Anywhere from 0.50 to 1.50 inches of rainfall islikely, with local amounts likely exceeding 1.50+ inches.

Further south, a stationary front will extend southwestward from the cold front and bring showers and general thunderstorms with moderate to heavy rainfall at times to locations within the vicinity. Further west, the area of high pressure will continue to build over the western and central United States as it progresses eastward behind the exiting low.

Page 6: WDT HAZARDOUS WEATHER OUTLOOK 9/4/2017€¦ · Threat Legend Orange –Strong to Severe Thunderstorms Possible Red –Significant Severe Thunderstorm Threat Purple –Severe Weather

Threat LegendOrange – Strong to Severe Thunderstorms PossibleRed – Significant Severe Thunderstorm ThreatPurple – Severe Weather Outbreak (Day 1 and 2 Only)Green – Excessive Rainfall

Blue – Significant Snow/Ice

Day 4 – Thursday Threat Assessments and Morning Frontal Analysis No significant threat regions:

The cold front will begin to move offshore, but will leave the chance of precipitation possible across the Northeast. A stationary front will extend southward along the EasternSeaboard and into the Gulf of Mexico. This will likely bring showers and generally weak thunderstorms to these regions on Thursday. The high over the central United States will continue to build and slowly move eastward behind the low.

Page 7: WDT HAZARDOUS WEATHER OUTLOOK 9/4/2017€¦ · Threat Legend Orange –Strong to Severe Thunderstorms Possible Red –Significant Severe Thunderstorm Threat Purple –Severe Weather

Threat LegendOrange – Strong to Severe Thunderstorms PossibleRed – Significant Severe Thunderstorm ThreatPurple – Severe Weather Outbreak (Day 1 and 2 Only)Green – Excessive Rainfall

Blue – Significant Snow/Ice

Day 5 – Friday Threat Assessments and Morning Frontal Analysis No significant threat regions:

Into Friday, high pressure is expected to dominate much of the United States weather pattern as the low and frontal boundaries move offshore. However, in the far Northeast United States, showers are possible along a trough axis. Showers and general thunderstorms will be possible across Florida along the stationary front still present over this region. Elsewhere, fair weather conditions will persist.

Page 8: WDT HAZARDOUS WEATHER OUTLOOK 9/4/2017€¦ · Threat Legend Orange –Strong to Severe Thunderstorms Possible Red –Significant Severe Thunderstorm Threat Purple –Severe Weather

Day 6 – Saturday Threat Assessments and Morning Frontal Analysis

Discussion: Into the weekend, high pressure will continue to encompass a majority of the United States. Lingering showers are possible on Saturday in the far Northeastern United States. A new low-pressure system may develop in the lee of the Rockies and bring a chance for showers and thunderstorms across the far Northern Plains on both Saturday and Sunday. Further south into the tropics, Hurricane Irma is forecast to continue to move generally to the west-northwest, closer to eastern Caribbean Islands and U.S. Territory. However, being 6 and 7 days out, a high degree of uncertainty still remains on the exact track of this storm. Model guidance shows a variety of different scenarios. Therefore, interests in the Southeast and along the East Coast should continue to monitor Irma and the possible forecast track scenarios. Please refer to the latest Active Storm Advisory for Irma for additional information. With that being said, the location of Irma on the two maps above is an approximation that could very well change as forecast confidence rises.

Day 7 – Sunday Threat Assessments and Morning Frontal Analysis


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