Written by Sig Silber
HEADLINES (Updated 5:15 PM EDT) –
– Slight Risk of excessive rainfall over parts of the Mid-Atlantic, Tennessee/Lower Mississippi Valleys, and Upper Midwest through Saturday morning
– Slight Risk of severe thunderstorms over parts of the Northern/Central Plains and the Upper/Middle Mississippi Valley through Saturday morning
– Tropical Storm Henri is forecast to become a hurricane and move toward Southern New England with a Moderate Risk of excessive rainfall starting as early as Saturday night
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.
Readers can scan through this article or jump to where they want to go via the links to the right. To get back to the Directory, hit the back arrow at the top of the URL bar on your screen. But in many cases, one of my Editors has graciously inserted a Return to Directory link to click so that is even easier. This is so high tech that I hardly believe it. |
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CONUS Focal Points
Short Range Focal Points
Short Range Forecast Discussion NWS Weather Prediction Center College Park MD
436 PM EDT Fri Aug 20 2021
Valid 00Z Sat Aug 21 2021 – 00Z Mon Aug 23 2021
…There is a Slight Risk of excessive rainfall over parts of the Mid-Atlantic, Tennessee/Lower Mississippi Valleys, and Upper Midwest through Saturday morning…
…There is a Slight Risk of severe thunderstorms over parts of the Northern/Central Plains and the Upper/Middle Mississippi Valley through Saturday morning…
…Tropical Storm Henri is forecast to become a hurricane and move toward Southern New England with a Moderate Risk of excessive rainfall starting as early as Saturday night…
Tropical Storm Henri is forecast to become a hurricane on Saturday morning as the storm heads northeastward towards Southern New England; forecast to make landfall on Sunday. Overnight Saturday, Henri starts producing rain over Southern New England, and the rain will become heavier as the storm moves onshore. Therefore, the WPC has issued a Moderate Risk of excessive rainfall with rain. The associated heavy rain will create numerous areas of flash flooding. Furthermore, many streams may flood, potentially affecting larger rivers through Sunday into Monday morning.
Elsewhere, a front extending from Upper Midwest to the Southern High Plains and Southern Rockies will move eastward to the Lower Great Lakes to the Middle Mississippi Valley by Sunday evening. Moisture streaming northward from the Western Gulf Coast will aid in producing showers and thunderstorms along and ahead of the boundary through Saturday night. The showers and thunderstorms will produce heavy rain over parts of the Upper Midwest through Saturday morning. Therefore, the WPC has issued a Slight Risk of excessive rainfall with these thunderstorms.
The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, and small streams the most vulnerable through Saturday morning. Additionally, the SPC has issued a Slight Risk of severe thunderstorms over the Northern/Central Plains and the Upper/Middle Mississippi Valley through Saturday morning. The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a few tornadoes. The severe thunderstorm and the excessive rainfall threat diminish on Saturday.
Meanwhile, tropical moisture, an old boundary, and upper-level energy will aid in producing showers and thunderstorms over the Tennessee/Lower Mississippi Valleys through Sunday morning. The showers and thunderstorms will produce heavy rain over the area. Therefore, the WPC has issued a Slight Risk of excessive rainfall with these thunderstorms. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, and small streams the most vulnerable through Saturday morning. The excessive rainfall threat will continue over the region on Saturday into Sunday morning.
Furthermore, tropical moisture and a weak upper-level low over the Mid-Atlantic will produce showers and thunderstorms through Sunday morning. The showers and thunderstorms will produce heavy rain over parts of the Mid-Atlantic through Saturday morning. Therefore, the WPC has issued a Slight Risk of excessive rainfall with these thunderstorms. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, and small streams the most vulnerable through Saturday morning. The excessive rainfall threat decreases slightly on Saturday into Sunday.
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
The below does not update and is a still rather than the 40-hour animation of the recent past. But if you click on it you will get the upadated animattion. If it does not upload completely you need to hit the refresh button.
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Day 3 – 7 Hazards
Valid Monday August 23 2021 – Friday August 27 2021
Hazards:
– Heavy rain across portions of the Great Lakes, the Upper Mississippi Valley, and the Northern Plains, Tue, Aug 24.
– Heavy rain across portions of the Great Lakes and the Upper Mississippi Valley, Fri, Aug 27.
– Heavy rain across portions of the Mid-Atlantic and the Northeast, Mon, Aug 23.
– Flooding occurring or imminent across portions of the Southeast, the Great Lakes, the Mid-Atlantic, the Northeast, and the Southern Appalachians.
– Excessive heat across portions of the Lower Mississippi Valley, the Tennessee Valley, the Middle Mississippi Valley, the Southeast, the Southern Plains, and the Ohio Valley, Mon-Tue, Aug 23-Aug 24.
– Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Tue-Wed, Aug 24-Aug 25.
– Heavy rain across portions of mainland Alaska, Mon, Aug 23.
– High significant wave heights for coastal portions of mainland Alaska, Thu, Aug 26.
Detailed Summary:
The synoptic scale pattern over the Lower 48 during the medium range period (Mon, Aug 23 – Fri, Aug 27) can be summarized by a building areas of ridging aloft over the southern U.S. while a steady stream of Pacific disturbances track from the Northwest to the Upper Midwest. The weather system in the spotlight at the very start of the period is Henri, which is forecast to be somewhere over New England or even as far west as upstate New York. Precipitable water levels ~2-2.5 STDs above normal and ongoing southerly flow that could become oriented in a favorable upsloping manner would help to generate excessive rainfall rates in higher elevations. Much of these areas have also received heavy rainfall from remnants of Fred where overly saturated antecedent soil conditions are present.
Given the latest forecast shows a slowing forward motion and pivot in Henri’s track, flash flooding and areal flooding will likely remain a serious problem for portions of New England on Monday. River and stream flooding in wake of Henri may linger into the middle of the week. Coastal impacts should start to wain by Monday morning as the storm quickly weakens over land and the pressure gradient relaxes Sunday night, but some lingering coastal flooding may persist into early Monday so long as brisk onshore flow is present.
Across the remainder of the CONUS, hazards include an Excessive Heat area in the South-Central U.S. where heat indices are forecast to soar as high as 110-115 degrees. On the northern periphery of the expansive southern U.S. upper ridge, the pattern could behave in a “ring of fire” type manner as the aforementioned disturbances track just north of the Midwest. Areas of thunderstorms, some of which could be severe, have the potential to produce heavy rainfall rates and lead to flash flooding concerns. The area most at risk is the Upper Mississippi Valley where they reside closest a series of frontal systems passing through the region. The days that currently feature the most risk for heavy rainfall are Tuesday (8/24) and Friday (8/27). There could be other portions of the Northern Plains and Midwest that see rounds of showers and storms at differing times throughout the week.
The Gulf of Alaska coast is expected to deal with a deluge of Pacific moisture brought upon by a robust upper level trough tapping into rich subtropical moisture. An occluded low pressure system will introduce a steady barrage of precipitation out ahead it the first half of the week. Combined with persistent upslope flow along the higher elevations, copious amounts of rainfall are anticipated along the higher elevations of the Gulf Coast. Some of the highest elevations could even witness some measurable snowfall. Even parts of central Alaska could see scattered showers and thunderstorms as upper level troughing lingers over the state, but rainfall amounts are forecast to remain below threshold. Lastly, a qu ck moving wave of low pressure could generate high waves and swells along the northwest coast on Thursday. A significant waves area has been introduced and could be expanded or re-positioned should the wave height forecast change on Monday.
(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 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
For those interested in more detail, there are additional weather maps and information in the MORE WEATHER Addendum. The link to the Addendum is here. |
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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
Current watches, warnings, and advisories issued by the agencies of the National Weather Service. Hazards should show up in the various maps but the below links will take you to all outstanding watches and warnings in each category which may include some categories not covered in the various maps or difficult to find. So if there is a category of interest, click on the appropriate link below. |
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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 | |
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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 |