Written by Sig Silber

HEADLINES (Updated 6:24 pm EDT) –

– Elevated to critical fire weather conditions across a broad portion of the western U.S. and Plains

– A strong cold front is set to dispense much below normal temperatures across much of the central U.S

– Heavy showers and storms possible in the Plains and Mississippi Valley today, then across the eastern U.S. during the first half of the week

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 – 351 PM EDT Sun Sep 27 2020

Valid 00Z Mon Sep 28 2020 – 00Z Wed Sep 30 2020

…Elevated to critical fire weather conditions across a broad portion of the western U.S. and Plains.…

…A strong cold front is set to dispense much below normal temperatures across much of the central U.S…

…Heavy showers and storms possible in the Plains and Mississippi Valley today, then across the eastern U.S. during the first half of the week…

Fire weather remains a concern across portions of the western U.S., with Red Flag Warnings in effect across a large portion of California, as well as parts of Oregon, Utah, Colorado and New Mexico. High pressure building across the western U.S. is expected to support offshore winds, promoting critical fire weather conditions across much of Northern California, as well as the coastal ranges in Southern California. Fire weather conditions are expected to remain a concern for these areas in California through Monday.

In addition to sharply cooler temperatures, gusty winds behind a strong cold front sweeping through the Plains has prompted wind advisories for Sunday evening into the overnight across a large portion of the Plains. Dry and windy conditions continuing into Monday are expected to elevate fire weather concerns along the High Plains, especially from eastern Wyoming to the Texas Panhandle.

Showers and thunderstorms are expected to continue developing along and behind the front as it drops from the central Plains and mid Mississippi valley into the southern Plains and lower Mississippi valley this evening. Some of these storms may become strong to severe, with the potential for large hail, especially across portions of eastern Oklahoma and western Arkansas later today. Showers and storms are expected to advance east with the cold front, extending from the Great Lakes to the central Gulf Coast on Monday, before reaching the eastern U.S. on Tuesday. The front is forecast to slow as it moves into the eastern U.S. on Tuesday, which along with increasing moisture ahead of it, will raise the threat for heavy rainfall accumulations spreading north from the Southeast into the Mid-Atlantic by late Tuesday.

Prior to the front’s arrival, above-normal temperatures will continue through Monday from the upper Ohio valley and northern Mid-Atlantic, while persisting through Tuesday across the Northeast. Following a day of well-above normal temperatures, Monday is forecast to be sharply cooler across the southern Plains and Rockies. At to below-normal temperatures are forecast across most of the Plains and Midwest on Monday, before shifting farther east through the Ohio and Tennessee valleys, and central Gulf Coast states on Tuesday.

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 Great Lakes, the Northeast, the Mid-Atlantic, the Appalachians, and the Southeast, Tue-Wed, Sep 29-Sep 30.

– Flooding occurring or imminent across portions of the Southeast.

– Much above normal temperatures across portions of California, the Great Basin, and the Pacific Northwest, Mon-Fri, Sep 28-Oct 2.

– Much below normal temperatures across portions of the Central/Northern Plains, the Middle/Upper Mississippi Valley, and the Great Lakes, Thu-Fri, Oct 1-Oct 2.

– Heavy precipitation across portions of mainland Alaska, Tue-Fri, Sep 29-Oct 2.

– Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Mon-Fri, Sep 28-Oct 2.

– High winds across portions of mainland Alaska, Tue-Wed, Sep 29-Sep 30.

Detailed Summary:

During the medium range period (Monday, Sep 28 – Friday, Oct 2), a deep upper-level trough will be slow-moving across the central to eastern U.S., while upper-level ridging builds across the West. This upper-level pattern should lead to warmer than average temperatures across the West. Records for warm lows and highs are possible particularly across California and southern Oregon, with temperatures 5 to 15 degrees above normal. The Desert Southwest could see highs above 100 degrees, but only a few degrees above average for this time of year. Warmth spreads into the Pacific Northwest and Great Basin, but highs in the 70s and 80s are not considered hazardous.

On the other hand, cooler than normal temperatures are forecast for the central U.S. underneath the trough and behind a couple of cold fronts. These cooler temperatures will spread from the Rockies and Plains on Monday toward the Mississippi/Tennessee/Ohio Valleys by Tuesday and Wednesday, and eventually knock down above normal temperatures in the East as the week progresses. An area of Much Below Normal Temperatures was delineated on the Hazards graphic across portions of the Northern/Central Plains to Upper Midwest, where morning low temperatures could get into the 30s and cause the first frost or freeze of the season by Thursday/Friday. This seemed to be the most hazardous aspect of these temperatures more reminiscent of mid- or late fall.

A leading cold front moving across the East is expected to provide a focus for potentially heavy rainfall. Model guidance is not too agreeable yet as to where the heaviest rainfall will occur and the exact timing, as it depends on the frontal position, which in turn depends on the axis and orientation of the upper-level trough. But the potential is there for heavy rainfall stretching across much of the Eastern Seaboard. The highest threat seems to be on Tuesday and Wednesday, though some rain is possible Monday in the Southeast and lingering Thursday in the Northeast. Generally dry weather is forecast across the West underneath the ridge, and additional fire weather concerns may develop there.

Over Alaska, heavy precipitation is forecast in the south-central part of the state as potent surface lows move across the Gulf of Alaska. While the entire Gulf Coast may not see heavy precipitation constantly through the period, multiple rounds of precipitation are possible there next week. Along with the precipitation, high winds are a threat over portions of Kodiak Island and the Kenai Peninsula in the vicinity of Cook Inlet, currently expected late Tuesday into early Wednesday but dependent on the timing and track of the first surface low. The Bristol Bay region may also see some gusty winds with that system.

(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.

We also include drought information in this section.

New Seasonal Outlook Issued September 17, 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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