About Forecasts

This page explains the features on the Hail Forecasts page.

Day One Hail Forecast

This map is generated by National Weather Service.  The map displayed at The Hail Reporter is always the very latest map from NWS.  Unlike the maps for days 2-8, the Day One map is a forecast for hail specifically, and does not include the likelihood of wind or tornado.  The Day One Hail map is the most accurate forecast map NWS produces for hail.  Where the likelihood of hail in the present day is greater than or equal to 5%, NWS represents the forecast area with a brown/gold outline.  A dark blue outline represents areas of 15% likelihood, and a red outline represents 30% likelihood.  On rare occasions, a 45% likelihood exists, and even rarer is the 60% likelihood.  The higher the likelihood that is forecast, the rarer it is to see the day come and go with no hail storms.

NWS has a category called "severe weather" (wind, tornado, thunderstorm, and hail) and another called "extreme severe weather".  Extreme severe weather includes F2 or greater tornadoes,  damaging winds with speeds greater than 65 knots, or large hail 2" or greater in diameter. If the forecaster believes that there is a 10% or greater chance that extreme severe weather will occur on Day One, the outline of the area in question will be filled with hatch marks.  Otherwise, no hatched area will appear on the map.

Previous Forecast (6 Hours Ago) & Previous Forecast (12 Hours Ago)

Because hail forecasting is not a perfect science, and because the forecasts often evolve throughout the day, it is useful at times to be able to compare the current forecast for Day One with previous versions of the Day One forecast.  For example, one might notice in the morning that there is a large area of 30% likelihood forecast, but in the early afternoon, the forecast has been revised to show only a 5% area where the 30% had previously existed.  With this Previous Forecast feature, one can see the progression of the Day One forecasts throughout the day so as to better understand how the weather is evolving in that day.  The Hail Reporter shows two such outdated views---one from 6 hours ago, and the other from 12 hours ago.

Day Two Probabilistic

National Weather Service's forecast maps for days 2-8 do not show the likelihood of hail specifically, but they do give an indication of severe weather, which can include tornado, thunderstorms, high winds, and hail.  The Day Two Probabilistic map can show probabilities of these values:  5%, 15%, 30%, 45%, 60%.  As a general rule, the higher the likelihood of severe weather, the higher the likelihood that hail will occur.  The Day Two forecast is not generally updated as often as the Day One Hail forecast, but it does sometimes evolve throughout the day.  Therefore, it is a good practice to check it two or three times a day if you want an updated idea of what may happen tomorrow.

Day Three Probabilistic

Like the Day Two Probabilistic map, the Day Three map does not specifically address the likelihood of hail, but of severe weather generally, which can include tornado, thunderstorms, high winds, and hail.  Unlike the Day One and Day Two maps, the Day Three map will never show a 60% likelihood as it is impossible to forecast such a likelihood so far in advance. (To see a 60% forecast even on Day One is very rare.)  If you're interested in the near future for severe weather, it's a good idea to keep an eye on the Day Three map as it can change.  For example, you may have looked yesterday at the Days 4-8 map and noticed that there was nothing forecast, but find this morning that the Day Three map (which was yesterday's Days 4-8 map) is now showing a high likelihood of severe weather.

Days 4-8 Probabilistic

Since the accuracy of forecasting severe weather so far in advance is quite problematic, days 4-8 are lumped together into one map by NWS.  This map is useful merely as an indicator of the current guess as to what will happen.  Predictions on this map turn out either accurate or inaccurate, as do all weather predictions.  One should note, however, that when a prediction is followed consistently for several days, with each day's map still reflecting the likelihood of severe weather, those predictions more often prove accurate than not.  Having said that, however, it's important to point out that in a period in which no severe weather has been forecast or observed for several weeks, a very high probability of severe weather can suddenly pop up with little warning, and in days closer to today than 4-8 days out.  For example, imagine that you haven't seen any indication of action on the forecast maps for several days, then you look again tomorrow and see that the Day Two map is showing a 45% likelihood of severe weather.  This is why it's helpful to have all the maps shown together in one place, as they are shown at The Hail Reporter (but not shown at the NWS website.)

Current National Radar Loop

This standard NWS map shows a loop of the last 4 hours of radar data.  It also includes "categorical" outlines, which are more general than the outlines used for the prediction of severe weather.  The map is presented for Hail Reporter subscribers so as to have a current idea of what is happening right now.  If, for example, large hail is likely for today, you can get an idea of whether the forecast areas have severe weather currently developing at this hour.

Current Satellite Infrared

This NWS map is helpful as a supplement to the Current National Radar Loop map (above)  in understanding the temperature differences along weather front lines.  As severe weather normally develops at the coming together of warm and cold air masses, this map is helpful in understanding whether such areas may exist at present.

Current Severe Weather Watches

This map displays active weather watches, including those for tornadoes and thunderstorms.  On a day when hail is forecast, it will quite often happen in areas currently under such watches.  If this map, therefore, is currently showing no watches, it's likely that today's hail (if any) will not occur at this time.  Keeping an eye on this map, therefore, can help you to know if today's forecast hail is likely to happen soon (if at all).

Hail Reports During the Last 3 Hours

This is NWS's standard map showing points where hail, wind, and tornado reports have originated over the last 3 hours.  The Hail Reporter's "Hail Reports" page shows a superior and interactive map of hail storm reports, but the NWS map is shown here as a quick reference for recent activity.  This is done for the convenience of the subscriber who is interested in watching the day's hail storms develop in real time. Seeing the hail that has developed in only the last three hours can sometimes be a good indication of what will happen next.  If, for example, hail has been forecast for both Mississippi and Alabama (states that neighbor each other, one on the West and the other on the East), and hail has already been occurring in Mississippi, it's very likely that the forecast Alabama hail will indeed occur as the day's weather continues to develop.   By viewing reports from the last 3 hours, one can also sometimes witness that the hail for the day is tapering off.

It is also useful that these maps show wind and tornado reports as hail fall and the likelihood of hail fall often accompanies the updrafts and downdrafts associated with severe thunderstorms and tornadoes.  This is not to suggest that where there is wind, there will be hail, but it is helpful to the amateur forecaster to be exposed to the overall weather patterns over time.

All Today's Hail Reports

Like the Last 3 Hours map (discussed above), it is helpful to view all the hail, wind, and tornado reports from the present day---especially to see whether all the areas for which hail was forecast have yet received hail.

Yesterday's Hail Reports

As hail outbreaks often span more than one day without consulting the clock or the calendar, there are times when following the latest hail means looking back to yesterday's reports.  (NWS considers that a new day begins at 6:00 a.m. Central Standard Time.  The Hail Reporter, in contrast, begins the new day at midnight, just as our calendars do.)