Written by Sig Silber

HEADLINES (Update 5:00 PM EDT) –

– HIGH Risk of flash flooding in place today/tonight as Fred moves northward and spreads very heavy rainfall and potential for landslides to the Southern Appalachians

– Heavy rainfall and scattered flash floods are also possible across much of the eastern U.S.

– Cooler and wetter conditions are likely for the Northwest behind a potent cold front, with warm temperatures and Elevated to Critical fire weather conditions ahead of it

– Monsoonal moisture will cause additional showers and thunderstorms as well as the threat of flash flooding for the Southwest into Utah through midweek

This article provides continuous updates for a variety of Weather and Weather-Related Threats as well as a general weather forecast. These are “Live” maps that continually update. Please pay attention to the Mesoscale Events maps — Mesoscale Events are potentially life-threatening situations.

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For those interested in longer-term forecasts, we just published the new NOAA Seasonal Outlook and it can be accessed here.

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CONUS Focal Points

Short Range Focal Points

Short Range Forecast Discussion NWS Weather Prediction Center College Park MD

425 PM EDT Tue Aug 17 2021

Valid 00Z Wed Aug 18 2021 – 00Z Fri Aug 20 2021

…HIGH Risk of flash flooding in place today/tonight as Fred moves northward and spreads very heavy rainfall and potential for landslides to the Southern Appalachians…

…Heavy rainfall and scattered flash floods are also possible across much of the eastern U.S. as tropical moisture streams north…

…Cooler and wetter conditions are likely for the Northwest behind a potent cold front, with warm temperatures and Elevated to Critical fire weather conditions ahead of it…

…Monsoonal moisture will cause additional showers and thunderstorms as well as the threat of flash flooding for the Southwest into Utah through midweek…

This afternoon, Tropical Depression Fred continues a north-northeastward track through the Southeast, and is approaching the spine of the Appalachian Mountains close to the Georgia-North/South Carolina border. A slew of hazardous weather accompanies Fred, including extremely heavy rainfall and severe weather. A High Risk of excessive rainfall remains in effect over western North Carolina since the initial issuance this morning, as widespread rain accumulations of 4 to 8 inches (with isolated storm totals of 10 inches) are expected over the Southern Appalachians through today. This area is particularly sensitive to heavy rainfall due to the varying terrain and inundated ground from recent heavy rains in the region. Severe, widespread flash flooding is anticipated, and numerous Flash Flood Warnings cover the region as bands of training thunderstorms overtake the area.

In addition to flash floods, the heavy rain will bring an increased risk of landslides in the mountains of North Carolina and the Blue Ridge Escarpment. Severe weather also remains a distinct possibility over parts of Georgia, the western Carolinas, and southwestern Virginia where an Enhanced Risk of severe weather is highlighted by SPC, primarily for the threat of several tornadoes. Trailing bands of rain with Fred could also occur over northern Florida and into South Carolina today.

Meanwhile, tropical moisture streaming northward across much of the East feeding into a weak frontal system ahead of a weak upper-trough will lead to widespread rain and thunderstorms across the Central/Northern Appalachians and parts of the Mid-Atlantic into New York over the next couple of days. Through Friday, 2 to 4 inches of rain with isolated totals of 6 inches are expected over the Central Appalachians/Mid-Atlantic as remnants of Fred move north-northeast. Ahead of the anticipated scattered flash floods later this week, Flash Flood Watches are already in effect over the aforementioned areas in the Appalachians, Mid-Atlantic, and Northeast.

In the West, a potent cold front pushed by an upper-level low will move through the Intermountain West over the next couple of days, significantly cooling temperatures there. High temperatures are forecast to drop to 20 to 30 degrees below normal in the Northern Rockies by Wednesday, with highs in the 50s.

However, temperatures should remain hot ahead of the front, with a couple more days of 100+ temperatures expected for the Northern Plains. Areas such as the Central Great Basin should see warmer than normal temperatures today followed by below normal highs by Wednesday as the cold front approaches.

Ahead of the front, Elevated to Critical fire weather conditions are a threat again today, along with the potential for additional fire ignitions from dry thunderstorms. Red Flag Warnings are in place from portions of California through the Central Great Basin into the Northern High Plains as dry and windy conditions align with the movement of the strong front. Related to the fire activity, poor air quality continues over the northern Great Basin, Rockies, and Central California, where Air Quality Alerts cover the region.

Rain showers are also likely with this system in the West along and behind the cold front, while monsoonal moisture pools ahead of the boundary in the Southwest around Utah. The approaching front will interact with the monsoonal moisture to support a severe weather threat over Central Utah, where SPC has highlighted a Slight Risk for isolated severe wind gusts. Moreover, rainfall totals over an inch with locally higher rainfall amounts may produce isolated instances flash flooding across portions of the Four Corners states northward into the Northern Rockies, and eastward to Texas over the next couple of days. Embedded Slight Risks of excessive rainfall are highlighted over portions of Utah, southern Arizona, and Central Texas through Wednesday where the flash flood threat is more focused.

We try to keep this up to date but if is not you can find the updated version here.

When you click on this image it takes you to the SPC Fire Warning Page and you get a set of maps for Days 1, 2, 3 – 8, etc. You can then click on those for more detailed information. The map is a bit blurry as I tried to make it a bit larger than the map provided by NOAA but should be able to see where the current wildfire risks are. But if you click on this map, you will get to see three maps that show the risk for different time periods.

Thunderstorm Risk

This should play out something like shown in this 60 Hour Forecast Animation

Here is a national animation of weather fronts and precipitation forecasts with four 6-hour projections of the conditions that will apply covering the next 24 hours and a second day of two 12-hour projections the second of which is the forecast for 48 hours out and to the extent it applies for 12 hours, this animation is intended to provide coverage out to 60 hours. Beyond 60 hours, additional maps are available at links provided below. The explanation for the coding used in these maps, i.e. the full legend, can be found here although it includes some symbols that are no longer shown in the graphic because they are implemented by color-coding.

The two maps below break it down by day and may be easier to read.

Now, the Day One and Two CONUS Forecasts: These Maps Update Daily.

Day One CONUS Forecast	Day Two CONUS Forecast
These graphics update and can be clicked on to enlarge. You can see where the weather will be

During the winter much of our weather originates in the Pacific. That is why we pay attention to the near-term history of storms arriving.

Temperature

A version that shows a 40 hour animation and some other views can be found here

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Day 3 – 7 Hazards

Valid Friday August 20 2021 – Tuesday August 24 2021

Hazards:

– Heavy rain across portions of the Northern/Central Plains, the Tennessee Valley, the Middle/Upper Mississippi Valley, and the Ohio Valley, Fri, Aug 20.

– Severe weather across portions of the Northern/Central Plains and the Upper/Middle Mississippi Valley, Fri, Aug 20.

– Flooding possible across portions of the Southeast and the Southern Appalachians.

– Flooding occurring or imminent across portions of the Southeast.

– Excessive heat across portions of the Southeast, the Middle/Lower Mississippi Valley, the Southern Plains, and the Tennessee Valley, Sun-Tue, Aug 22-Aug 24.

Detailed Summary:

On Friday, a front across the Northern/Central Plains will focus showers and thunderstorms over the area as moisture streams into the region with a deep upper-level trough and energy move across the area. As a result, an area of heavy rain is depicted on the Hazards Chart on Friday that will overlap an area of potentially severe thunderstorms that will also be over the Upper Midwest on Friday.

The front moves slowly eastward to the Great Lakes by Sunday as the moisture supply ends while the trailing part of the boundary will extend across the Upper Midwest. Rain will continue along and near the boundary but will have lower precipitation amounts. Furthermore, tropical moisture will be over parts of the Tennessee and Southern Ohio Valleys on Friday. The moisture will aid in producing showers and thunderstorms over the region. Therefore, an area of heavy rain is depicted on the Hazards Chart over parts of Tennessee Valley and parts of the Southern Ohio Valley on Friday.

The previously mentioned upper-level trough will aid in producing below-average temperatures over the Northern High Plains and Northern Rockies through Tuesday. However, an upper-level high will develop over parts of the Lower Mississippi/Tennessee Valleys and parts of the Central Gulf Coast starting on Sunday through Tuesday. The temperatures will be slightly above average, yet the dew point temperatures will be in the low to mid-70s. The temperatures and dew point will combine to make the heat index around 110 to 115. Therefore, as a result, an area of Excessive Heat is depicted over parts of the Lower Mississippi/Tennessee Valleys and parts of the Central Gulf Coast starting on Sunday going through Tuesday.

For Alaska, the upper-level pattern will be dominated by troughing, which will be conducive to wet weather. At the surface, low pressure and a front will be across the Interior of Alaska on Friday and then move into Canada by Saturday, trailing the front across the Gulf Coast on Saturday. On Saturday, another area of low pressure and a front move across the Aleutians and move into the Interior and Gulf Coast by Tuesday. In the meantime, another front will move across the Far North on Sunday and move into Canada on Monday while draping across the Interior into Tuesday. The systems will produce rain over parts of the state through Tuesday. Yet, the precipitation totals will not reach the criteria for a hazard for this time of year. There is some uncertainty for heavy rain along the Gulf Coast, with the ECMWF being the most robust with the precipitation totals.

Click here for the latest complete Day 3 -7 Hazards forecast which updates only on weekdays. It includes the full discussion which I do not update in this article but only present the highlights.

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Ski Snow Reports

We will resume snow coverage in the Fall

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Drought Coverage

We include drought information in this section.

More information can be found here.

August Drought Outlook.

Seasonal Outlook Issued July 15, 2021

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Tropical Events

Atlantic and Gulf of Mexico

The Eastern Pacific

The Central Pacific

Updates on individual named storms can be obtained here.

And the Western Pacific

Weekly Tropical Forecast

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Intermediate-Term Weather Forecast

And shifting to the Alaska and CONUS Intermediate-Term Weather Forecast showing from left to right, Days 1- 5, 6 – 10, 8 – 14 and Weeks 3 – 4 You can click on these maps to have them enlarge, there are larger versions in the Addendum (More Weather the link is shown at the end of this section, and there are larger versions of these maps in the Addendum. Also, the discussions that go with these forecast maps can be found here (first two weeks) and here (Weeks 3 and 4).

First Temperature

And then Precipitation

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Mesoscale Events

The following map shows where mesoscale events are occurring or forecast. If you do not see any areas highlight on this map than there are no mesoscale events taking place or forecast. A mesoscale event is a very serious situation for a very small area and detailed information is provided for these events when they occur or are forecast. If a mesoscale event is shown, click on the map and more detail on the event will be shown.

Two different parts of the NWS issue this map and they are not always in agreement although they are pretty close. They (Norman Oklahoma and College Park Maryland) issue the alerts when they realize the need, so it is best to look on both maps and click one or both if you see areas highlighted.

This next map showing where “Headlines” have been issued for convection (and an animation of the recent movement of storms) should update and you should be able to click on to get additional details but if it does not update when you click on it, click here.

There is a slight difference between convection and thunderstorms. The below map shows where “Headlines” have been issued for Thunderstorms. You should be able to click on the map to get additional details but if it does not update, you can click here.

The map below shows the current wildfire risk which becomes more significant as we move into Summer. When you click on this image it takes you to the SPC Fire Warning Page and you get a set of maps for Days 1, 2, 3 – 8, etc. You can then click on those for more detailed information. The map is a bit blurry as I tried to make it a bit larger than the map provided by NOAA but should be able to see where the current wildfire risks are. But if you click on this map, you will get to see three maps that show the risk for different time periods.

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Now the Day 3 – 7 Hazards Outlook Maps

The orange and red outlined areas are what is most concerning of the forecasted Day 3 – 7 Hazards. This graphic does not update during the weekend. There is a discussion that goes with this graphic and you can access that discussion here.

The following is provided to help the reader relate the maps to how NWS will describe an area of the U.S.

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Now to our More Detailed Weather Report

This graphic is about Atmospheric Rivers i.e. thick concentrated movements of water moisture. More explanation on Atmospheric Rivers can be found by clicking here or if you want more theoretical information by clicking here. The idea is that we have now concluded that moisture often moves via narrow but deep channels in the atmosphere (especially when the source of the moisture is over water) rather than being very spread out. This raises the potential for extreme precipitation events.

500 MB Mid-Atmosphere View

The map below is the mid-atmosphere 3-Day chart rather than the surface highs and lows and weather features. In some cases, it provides a clearer less confusing picture as it shows only the major pressure gradients. This graphic auto-updates so when you look at it you will see NOAA’s latest thinking. The speed at which these troughs and ridges travel across the nation will determine the timing of weather impacts. This graphic auto-updates I think every six hours and it changes a lot. Thinking about clockwise movements around High-Pressure Systems and counterclockwise movements around Low-Pressure Systems provides a lot of information.

Day 3 Above, 6 Below	Day 4 Above,7 Below	Day 5 Above.

Here are the precipitation forecasts. First the cumulative for Days 1 – 3

Then cumulative for Days 1 – 5

Then cumulative for Days 1 – 7

Looking ahead to next week.

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Additional Tools to Obtain Watches and Warnings

Below you will see a number of different maps that are updated in real-time, making this a “live” report. If a part of one or more of the maps shows an area that is highlighted, you can click on it and get the full current report. By having the reader click on these active situations rather than having GEI do so, you will not miss any events in which you might have an interest and which we had not noticed and the page will not get cluttered with warnings, etc that have since expired.

Our focus here is events that are likely to last in the range of six hours but there can be longer or shorter events that are addressed by the Storm Prediction Center which is the main source of the information in this article. Long-term major events like a Hurricane are more likely to be in a separate article. But that may not always be the case. Since in general, all the links on this page transfer you into the NOAA system, in order to get back into this article you need to either close the tab to which you were transferred or click back on the tab that has this article.

Live Warning Maps which If Severe Weather is Shown can be Clicked on to get more detail about these events. If there is a current warning shown on the map, click on the map for additional information related to the event.	These maps are updated as risks are identified.
This is the current graphic showing any mesoscale discussions (MD’s) which are in effect over the contiguous United States. Please read the description of the purpose of our MD’s for further information. Details on all valid MD’s may be found on our Current Mesoscale Discussions page.
Convective Outlooks
This is today’s forecast for organized severe thunderstorms over the contiguous United States. Please read the description of the risk categories for further information. You may find the latest Day 1 Outlook available as well as all Outlooks issued today online.	Today’s Outlook
This is tomorrow’s forecast for organized severe thunderstorms over the contiguous United States. Please read the description of the risk categories for further information. The latest Day 2 Outlook is available as well as all Outlooks that have been issued today.	Tomorrow’s Outlook
This is the day after tomorrow’s (day 3) forecast for organized severe thunderstorms over the contiguous United States. Please read the description of the risk categories for further information. The latest Day 3 Outlook is available as well as all Outlooks that have been issued today.	Day 3 Outlook
This is the day 4-8 forecast for organized severe thunderstorms over the contiguous United States. The latest Day 4-8 Outlook is available as well as all Outlooks that have been issued today. Note: A severe weather area depicted in the Day 4-8 period indicates a 30% or higher probability for severe thunderstorms (e.g. a 30% chance that a severe thunderstorm will occur within 25 miles of any point).	Day 4-8 Outlook
The Thunderstorm Outlooks depict the probability of thunderstorms across the contiguous United States in 4 or 8 hour time periods. The probabilistic forecast directly expresses the best estimate of a thunderstorm occurring within 12 miles of a point. The three probabilistic forecast thresholds are 10, 40, and 70 percent.	Thunderstorm Outlook
Fire Weather Outlooks
This is today’s forecast for organized wildfires over the contiguous United States. Please read the description of the risk categories for further information about this product.	Today’s Outlook
This is tomorrow’s forecast for organized wildfires over the contiguous United States. Please read the description of the risk categories for further information about this product.	Tomorrow’s Outlook
This is day 3-8 forecast for organized wildfires over the contiguous United States. Please read the description of the risk categories for further information about this product.	Day 3-8 Outlook

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