Written by Sig Silber

HEADLINES (Updated 5:59 pm EDT) –

“…. A Slight to Moderate Risk of excessive rainfall exists in the Mid-Atlantic through Thursday; …. A Slight Risk of excessive rainfall and severe thunderstorms exists over the Northern Plains through Friday; …. Elevated fire weather conditions & Excessive Heat Warnings are in effect over portions of the Western U.S through Thursday; …. Record heat from the Southern Plains into the Southwest possible through Friday”

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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CONUS Focal Points

Short Range Focal Points

Short Range Forecast Discussion NWS Weather Prediction Center College Park MD – 312 PM EDT Wed Aug 12 2020

Valid 00Z Thu Aug 13 2020 – 00Z Sat Aug 15 2020

…A Slight to Moderate Risk of excessive rainfall exists in the Mid-Atlantic through Thursday…

…A Slight Risk of excessive rainfall and severe thunderstorms exists over the Northern Plains through Friday…

…Elevated fire weather conditions & Excessive Heat Warnings are in effect over portions of the Western U.S through Thursday...

…Record heat from the Southern Plains into the Southwest possible through Friday…

A front will become quasi-stationary over the Northeast/Mid-Atlantic into the Ohio Valley into Thursday, before sagging southward late Thursday into Friday as high pressure builds southward from eastern Canada. High moisture will pool along the front, which when lit by daytime heating sparks showers and thunderstorms near and south of the boundary with potentially heavy rainfall. A Moderate Risk of excessive rainfall exists over the Mid-Atlantic from Wednesday afternoon into Thursday morning due to recent and expected heavy rainfall, with a Slight Risk existing in and near Virginia Thursday and Thursday night.

A slowly moving cold front is expected to produce windy conditions, but little precipitation, which will factor into elevated to critical fire weather conditions Wednesday and Thursday across portions of the Northwest, Northern Rockies and Great Basin. Red Flag Warnings are in effect for many of these areas. Meanwhile, potentially record heat spreads westward from the Southern Plains through the Southwest into California. Excessive Heat Watches and Warnings have been posted for portions of California and the Southwest. High temperatures above 105 degrees should be commonplace, with Death Valley itself likely to reach the mid 120s; record highs are possible across these areas.

Moisture in advance of the slowly progressive Western front moving into the Northern Plains will aid in producing showers and thunderstorms with heavy rainfall across the Northern Plains and eventually the Upper Mississippi; a Slight Risk of excessive rainfall/flash flooding and severe thunderstorms exists through Friday.

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 20 hour animation and some other views can be found here OR SIMPLY CLICK ON THE IMAGE.

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Day 3 – 7 Hazards

Hazards:

– Heavy rain across portions of the Southeast, the Southern/Central Appalachians, and the Mid-Atlantic, Sat-Sun, Aug 15-Aug 16.

– Excessive heat across portions of the Central Great Basin, California, and the Southwest, Sat-Wed, Aug 15-Aug 19.

– Excessive heat across portions of the Lower Mississippi Valley and the Southern Plains, Sat-Sun, Aug 15-Aug 16.

– Much above normal temperatures across portions of California, the Pacific Northwest, the Central/Northern Great Basin, and the Northern Rockies, Sat-Mon, Aug 15-Aug 17.

– Heavy rain across portions of the Alaska Panhandle, Sat-Sun, Aug 15-Aug 16.

Detailed Summary:

The medium range period (Saturday, Aug. 15 to Wednesday, Aug. 19) will feature a front moving slowly southward across the eastern U.S., while another front located ahead of an upper-level trough should push through the Midwest, Great Lakes, Mississippi and Ohio Valleys, and Eastern Seaboard through the period. These fronts will provide focuses for rain and thunderstorms. Currently, it appears the best chance for widespread heavy rainfall will be across the Southern and Central Appalachians eastward into the Carolinas and Mid-Atlantic through the weekend. Farther north, rain and thunderstorms (which could be strong to severe) could spread from the Great Lakes region/Upper Ohio Valley Sunday to the Northeast Monday and Tuesday ahead of the front. However, the front is likely to be progressive enough that widespread heavy rainfall is not forecast, but locally heavy rain amounts are possible. The southeastern U.S. can also expect scattered rain and storms, potentially increasing in coverage by Tuesday and Wednesday of next week, and particularly during afternoon and evening hours as daytime heating increases the thunderstorm potential.

Meanwhile, an upper-level high is forecast to meander across the Southwest and build ridging across the West over the weekend into early next week. Excessive heat will be persistent in the Desert Southwest, as high temperatures continue to be 110-120 degrees, hotter than average for this time of year as monsoon season has usually taken hold by now. Very hot temperatures are expected to stretch into the lower elevations of California, including the valleys and even approaching the coast in some areas. Excessive Heat Watches are already in effect. While hot weather with temperatures nearing or exceeding 100 degrees are forecast all across the West under the ridge, highs are expected to be most anomalous starting in the Pacific Northwest on Saturday and spreading to the Northern Great Basin early next week. The Northwest should cool down closer to normal around midweek as upper-level troughing coming in presses the high southward. Additionally, heat and high dewpoints will combine to create high heat indices in portions of the Southern Plains to Lower Mississippi Valley this weekend. Record high temperatures are possible for the West to Southern
Plains. Meanwhile, temperatures look to be below average for the central U.S. next week.

In Alaska, a low pressure system is forecast to spin offshore of Panhandle this weekend. Moisture inflow with this cyclone could lead to heavy rain particularly in the southeastern part of the Panhandle. Another low pressure system is currently forecast to track through the Bering Sea early next week, while another front drops southward across the western part of the state. There is some potential for gusty wind and heavy rain with these features in southwestern Alaska, but currently the large variability in model guidance precludes drawing hazard areas there. Temperatures are expected to be warmer than average for the southwestern part of the state and interior Alaska through early next week, with highs in the 70s and even nearing 80 degrees.

(This is updated only during the week) Note the first list is weather highlights, this list is hazards. Not sure there is that much of a difference but they come from two different parts of NOAA. The Day 3 – 7 Hazards List does not update on weekends. But it is still useful as it remains valid for the period of time it covers. Of course, all forecasts are subject to change. Later we show a map of the hazards. Perhaps we should show them together.

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 more detailed coverage when the summer is over. During the summer we might add some drought information in this section.

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Tropical Events

This is now beyond the time of the year we pay special attention to Tropical Events other than the Western Pacific.

So I am replacing the large with three small maps but you can click on them to get larger versions. Even though they are small maps you should be able to tell if there is activity and If I see activity I will make the map where there is activity full size.

the Central Pacific.	the Eastern Pacific	the Atlantic and the Gulf of Mexico

Updates on individual named storms can be obtained here.

And the Western Pacific

Week 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

Now we look at the forecast for the Maximum Temperature three days out.

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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