Written by Sig Silber

HEADLINES (Updated 5:03 pm and 9:12 pm EDT) –

– Sally to bring hurricane force winds and life-threatening flash flooding and storm surge to parts of the central Gulf Coast

– Improving fire weather conditions expected across the West, with some much needed rainfall moving in by late Thursday

– Surge of below normal temperatures will begin to march south and eastward from the Northern Plains to the Upper Midwest and Great Lakes on Wednesday and Thursday

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.

Directory

CONUS Focal Points

Short Range Focal Points

Short Range Forecast Discussion NWS Weather Prediction Center College Park MD – 340 PM EDT Tue Sep 15 2020

Valid 00Z Wed Sep 16 2020 – 00Z Fri Sep 18 2020

…Sally to bring hurricane force winds and life-threatening flash flooding and storm surge to parts of the central Gulf Coast…

…Improving fire weather conditions expected across the West, with some much needed rainfall moving in by late Thursday…

…Surge of below normal temperatures will begin to march south and eastward from the Northern Plains to the Upper Midwest and Great Lakes on Wednesday and Thursday…

The latest forecast for Hurricane Sally from the National Hurricane Center brings Sally inland by early Wednesday morning. Hurricane force winds, life-threatening storm surge, very heavy rainfall, and a threat for tornadoes will continue through Wednesday for portions of the Central Gulf Coast region. Sally is a slow moving storm so very heavy rainfall will likely bring a high risk for life-threatening and historic flash flooding. As Sally makes her way slowly inland, significant flash and urban flooding, as well as minor to moderate river flooding, are likely to spread northward into Alabama, northern Georgia, and the western Carolinas. The latest forecast storm total rainfall from Sally calls for 10 to 20+ inches of rain from far southeastern Mississippi to the western Florida Panhandle, with 4 to 8 inches (and locally higher amounts) farther inland along the track through the Southeast U.S.. Please refer to the latest advisory from the NHC for additional and updated information regarding Sally.

Out West, dense smoke advisories and air quality alerts remain in place across much of the Northwest U.S. and parts of Central California. Compared to recent days, fire weather conditions should continue to improve across the Western U.S. ahead of a frontal boundary. By Thursday evening, some much anticipated rainfall is expected to move into parts of the Pacific Northwest.

Above average temperatures will continue into Wednesday from the Western U.S. into the Central Plains and Midwest to the Northeast. A cold front dropping into the Northern Tier will bring a surge of colder temperatures spreading from the Northern Plains into the Upper Midwest/Great Lakes Wednesday into Thursday. Daytime highs could be 10 to 15 degrees below normal for some locations within this airmass. Elsewhere, the East Coast should remain comfortable and near normal the next few days, with below normal temperatures also expected within areas impacted by Hurricane Sally.

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 and the Mid-Atlantic, Fri, Sep 18.

– Flooding possible across portions of the Southeast, the Lower Mississippi Valley, and the Tennessee Valley.

– Flooding likely across portions of the Southeast and the Lower Mississippi Valley.

– Much above normal temperatures across portions of the Central Great Basin, the Central/Northern Rockies, and the Central/Northern Plains, Fri, Sep 18.

– Much above normal temperatures across portions of the Central Rockies and the Central/Northern Plains, Fri-Sat, Sep 18-Sep 19.

– Much below normal temperatures across portions of the Great Lakes, the Mid-Atlantic, the Northeast, the Central Appalachians, and the Ohio Valley, Sat-Mon, Sep 19-Sep 21.

– Much below normal temperatures across portions of the Great Lakes, Fri-Sat, Sep 18-Sep 19.

– Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Fri, Sep 18.

– Heavy precipitation across portions of mainland Alaska and the Aleutians, Mon-Tue, Sep 21-Sep 22.

– Heavy rain across portions of the Alaska Panhandle, Sun, Sep 20 and Tue, Sep 22.

– High winds across portions of mainland Alaska, Mon-Tue, Sep 21-Sep 22.

Detailed Summary:

The medium range period (Friday, Sep 18 – Tuesday, Sep 22) will first feature the remnants of Hurricane Sally moving through the Southeast before combining with a cold front off the U.S. East Coast likely by Saturday morning. While there remains some uncertainty with the speed at which Sally moves eastward, it appears that Friday could still see some heavy rain onshore over portions of the Carolinas/southern Mid-Atlantic. Tropical moisture overrunning the aforementioned front could spread lighter rain farther north across the Eastern Seaboard, with Cape Cod, Martha’s Vineyard, and Nantucket having the best chance of rain with their eastern geographical position.

Another area to watch for potentially heavy rain is the western/central Gulf Coast. A tropical area of low pressure is expected to meander in the Bay of Campeche/western Gulf of Mexico over the next several days causing heavy rain over water. At this time, it remains questionable if much of this rainfall will make its way onto the Texas and Louisiana coastlines, so no heavy rain hazard area was drawn there for now.

The upper-level flow in the medium range is forecast to start out fairly amplified, with a trough in the Great Lakes to Northeast. This upper trough and a cool Canadian surface high pressure system will cause fall-like below normal temperatures across those areas, shifting eastward through early next week. This could lead to the first frost or freeze in some areas of the Great Lakes region and interior Northeast. Below normal temperatures are forecast all the way south to the Southeast. Farther west, an upper-level ridge of high pressure is expected over the Four Corners to Northern Rockies Friday, with its axis shifting to the Plains over the weekend as an upper-level low pushes eastward across the Northwest. Above normal temperatures are forecast under the ridging before a cooldown with the upper low, which could also cause modest rainfall, particularly over the Northern Rockies. Meanwhile, fire danger is a possibility south of the jet stream over the Great Basin.

Alaska can expect a busy period weather-wise. A first round of low pressure systems traversing the area is expected late this week, which could cause locally heavy precipitation along the Gulf of Alaska coast (with potential for snow at higher elevations) on Friday after a windy and rainy/snowy Thursday in the south-central part of the state (now in the short range period). Some possibly heavy rainfall could occur over much of the Panhandle on Sunday as subtropical moisture is pulled into the frontal system. Then, another large surface low pressure system is forecast to move southeast from the Bering Sea across the Aleutians around Monday into the Gulf of Alaska Tuesday. Gusty winds are possible over the Aleutians, but high winds may pose a greater threat across south-central Alaska, though it will depend on the exact low track. Another threat with this system will be a round of heavy precipitation from the eastern Aleutians into the Alaska Peninsula toward the Kenai Peninsula for Monday/Tuesday, along with heavy rain potential once again for the Panhandle by Tuesday.

(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

New Feature – Ski Reports. (We may be a tad premature but not by much). It is difficult to find reports that auto-update on-screen (and they are very long) but these links will get you to them – If you have additional suggestions make them in the comments section after every GEI Article and we may add those links. We will try to not have too much overlap as that can add to the confusion.

We will update the above map weekly but more frequent updates can be obtained here.

Snow Forecasts.

Day 1

Day 2

Additional snow information can be found here and here.

During the summer we might add some drought information in this section.

New Seasonal Outlook Issued August 20, 2020

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Tropical Events

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 and when available add other related maps.

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

Atlantic and Gulf of Mexico

And the Eastern 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

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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