MOS Forecast Extends Now To 3 Days

Back in December we announced a new forecast tool in ForeFlight Mobile called Model Output Statistics or MOS. A TAF-like forecast, MOS provides site-specific weather guidance to pilots for hundreds of airports where a TAF is not provided by the National Weather Service (NWS). We’re happy to say that we’ve taken MOS even further.

Now Even More MOS

Not only have we added over three hundred additional MOS airports to ForeFlight Mobile, but we’ve extended the MOS guidance from 24 hours to 3 days. That’s right, in ForeFlight Mobile 2,032 stations throughout the U.S. and its territories now have a TAF-like MOS forecast with site-specific weather guidance out to 3 days in the future. Pilots can now get a forecast of wind direction and wind speed, ceiling height, ground visibility and precipitation similar to what you might see in a TAF, now extended to 84 hours for over 2,000 airports. This means that even when the TAF stops at 24 or 30 hours, MOS continues to provide site-specific weather guidance beyond the forecast timeframe of over 700 NWS TAFs.

Finding MOS in ForeFlight

The MOS forecast option is available to all subscribers with ForeFlight Mobile 6.6 and to find it in the app, simply select an airport or station from the Maps view. In the pop-over window, tap the Forecast tab at the bottom. Then press the MOS button to reveal this forecast product and scroll through the MOS forecast over the next three days.

Access the MOS forecast in the Maps view by tapping on an airport.

Access the MOS forecast in the Maps view by tapping on an airport.

Flight Rules Thrown Out of the ForeFlight Mobile App

No, we didn’t convince the FAA to change the regulations; however, in ForeFlight Mobile we’ve stopped using the term Flight Rules when referring to weather conditions for an airport. Flight Rules has now been replaced with a more appropriate term, namely, Flight Category which appears as a selection below TFRs. Same useful information, just under a new name.

Flight Category selected in the Map overlay selector

Flight Category overlay is shown selected in the Maps view menu.

Flight rules refers to the regulatory requirements defined in 14 CFR Part 91, Subpart B. These include Visual Flight Rules (VFR), Instrument Flight Rules (IFR) and Special VFR. Although derived from Flight Rules, Flight Category describes the observed or forecast weather conditions at the airport based on the combination of prevailing ground visibility and ceiling. Using a color-coded marker, flight categories include VFR, Marginal VFR (MVFR), IFR and Low IFR (LIFR) as shown below. Although not implemented in ForeFlight, the National Weather Service (NWS) uses a fifth category to represent Very Low IFR (VLIFR) conditions which includes a ceiling less than 200 feet and/or visibility less than 1/2 statute miles.

Flight Category legend.

Flight Category legend used in ForeFlight Mobile.

In the app, you can also display the ceiling and visibility markers separately on the ForeFlight Map. Similar color coding of these markers will occur based on the criteria shown above. For example, ceilings markers are being displayed on the Map below. Notice for Topeka, Kansas,  a marker labeled “26” representing a MVFR ceiling of 2,600 feet so the marker is shown in blue. It is critical to understand that this does not imply that the Flight Category for the airport is MVFR since this marker does not also factor in the reported visibility.

Ceiling marker view.

Ceiling markers do not factor in the reported visibility relative to Flight Category color coding.

In this case, tapping the marker for Topeka as shown below indicates that the surface visibility is reported at 1 statute mile representing an IFR Flight Category. Hence the coded observation is colored red accordingly.  Similarly, when displaying the visibility markers on the Map, the color shown does not also factor in the reported ceiling.

Weather station details in the Maps view.

Tap on the marker to reveal the Flight Category, indicated by the highlighted observation text, when using the Ceiling and Visibility overlays.

Lastly, ceiling markers are unique in that a marker will only be displayed when the observation is reporting a broken, overcast or indefinite ceiling. In other words, if the sky is clear or there are just scattered or few clouds in the report, a marker will not be displayed on the Map.

While the departure from Flight Rules seems pretty subtle, using Flight Category in the ForeFlight Mobile app now matches FAA documentation and other official weather guidance provided by the NWS.

Automated Reports of Blowing Snow in a Blizzard

In a bona fide blizzard you would certainly expect to see a fair amount of blowing snow, right? Well, take a look at the conditions for these three airports at the height of the nor’easter that recently pummeled the Northeast with a record snowfall.

KEWB 270539Z AUTO 03030G46KT 1/4SM R05/1600V2200FT +SN FZFG SQ VV004 
     M02/M02 A2958 RMK AO2 PK WND 03046/0538 P0000 T10171022

KTAN 270552Z AUTO 01018G32KT 1/4SM +SN FZFG VV003 M02/M03 A2962 
     RMK AO2 PK WND 04040/0536 SLP031 

KFMH 270535Z AUTO 03032G52KT 1/4SM SN OVC002 M01/M02 A2955 
     RMK A02

In the belly of this storm, these airports observed strong, gusty winds, moderate to heavy snow and even a squall, but no hint of blowing snow (coded as BLSN) in any of these automated reports. This seems rather odd, but an Automated Surface Observing System (ASOS) is not designed to report blowing snow in the middle of a blizzard. You read that right; it’s designed to report blowing snow only after the winter storm has departed as seen here for the observation at Worcester, Massachusetts the following morning.

KORH 280947Z AUTO 31020G26KT 2 1/2SM BLSN CLR M14/M18 A2972 
     RMK AO2 PK WND 29028/0913 VIS 3/4V5 T11391178

Before an ASOS can report blowing snow (even when blowing snow conditions are detected by the precipitation sensors), all of the following conditions must also be met –

  1. Visibility must be less than 7 statute miles
  2. Ambient temperature must be less than or equal to 14 degrees Fahrenheit
  3. Sky cover must be less than overcast or the ceiling height must be greater than 10,000 feet
  4. Wind speed must be greater than 22 knots.

From the surface observations during the recent blizzard, only two of the four conditions were met, namely, wind speed and visibility. As a result, BLSN wasn’t reported in the automated observation. Keep in mind, at airports or stations with a human observer, the observation may be augmented to include BLSN like it was here for Providence, Rhode Island during the storm.

KPVD 270551Z 01025G34KT 1/2SM R05/3000VP6000FT SN BLSN FZFG VV012 
     M07/M09 A2965 RMK AO2 PK WND 01038/0538 SLP039

Automatically Pack Weather and NOTAMs in ForeFlight Mobile version 6.6.1

ForeFlight Mobile’s Pack feature simplifies your pre-flight preparation and enhances your safety by ensuring that you have all of the current charts, data, NOTAMS, fuel prices, and the latest pre-departure weather information stored on your device for inflight access. ForeFlight Mobile 6.6.1 introduces a refinement to Pack which automatically keeps the most current weather, TFRs, fuel prices, and NOTAMs refreshed and downloaded onto your device during your preparation for flight.

After planning your route, tap the Pack suitcase to ensure you’ve downloaded all the data you will need for the trip:

Tap the Pack suitcase and download the data to initiate the auto-packing feature.

Tap the Pack suitcase and download the data to initiate the auto-packing feature.

After the initial ‘Pack’ is completed, then Pack will continue to refresh every 30 minutes with the latest METARs, TAFs, AIR/SIGMETs, TFRs, fuel prices, and NOTAMs (based on each of these you have selected to Pack). The automatic refresh only runs while you are connected to the Internet and the app is open, not running in the background. If you leave the app and come back, the weather, TFRs, fuel prices, and NOTAMs will update automatically, without the need to manually tap the Pack suitcase again. This ‘auto-pack’ feature will continue to run for 24 hours or until you change the route. The red badge alert for Pack will then only show if you make significant changes to your route.

There are no settings required to make this work and Pack is available to both Basic and Pro subscribers. We recommend that you tap the Pack suitcase one final time before leaving your Internet connection prior to flight. When you see the All Packed! message, you’re ready to fly:

A final check on Pack: All Packed! means you are ready to fly.

A final check on Pack: All Packed! means you are ready to fly.

ForeFlight Mobile Version 6.6.1 Is Available On The App Store

ForeFlight Mobile version 6.6.1 is a free download for subscribers via the the App Store. For additional information, be sure to review our Pilot’s Guide. You can also download the Pilot’s Guide onto your device using the built-in catalog in the Documents view.

We’ve refined the Internet radar color bar

Of all of the weather layers available on the ForeFlight Maps view, the radar mosaic is likely the most frequently viewed. With such a high glance value, even the most inexperienced pilot can quickly identify where the significant adverse weather is located and plot to avoid it. This is because radar reflectivity (or the amount of energy returned to the radar) is strongly correlated to the size and concentration of the hydrometeors (rain drops, snow flakes, hailstones, etc.) present in the radar’s view. Large raindrops or hailstones are indicative of intense updrafts and a high probability of severe or extreme convective turbulence. So it’s important that the radar mosaic be depicted in a balanced way that engenders caution without over-warning the pilot when the weather is benign. To that end, we’ve made a subtle change to the Internet radar color map as shown below.


Comparison of new and old Internet radar colors.

The primary goal was to modify the mid-range reflectivity (dBZ) values. This provides better awareness during the early stages of convective growth that were previously being shown as a dark green. Consequently, we shifted yellow and orange by 5 dBZ. For instance, yellow used to begin at 40 dBZ, but now it begins at 35 dBZ with orange beginning at 40 dBZ. We kept red at 50 dBZ and added a darker shade of orange to fill the void. This subtle modification won’t significantly change the look and feel of active thunderstorm regions, but will help highlight an area of developing convective weather much sooner.

For example, take a look below at this thin line of precipitation just east of Beaumont, Texas. There is a distinct “weak” region in this line just southeast of Beaumont. This part of the line is characterized by mostly green contours with just a hint of yellow. At a quick glance, it may be very tempting for a pilot to flight plan through this thin convective line at this weak region. Take notice of the storm track that has also been depicted within this part of the line. Storm tracks shown by the straight lines denote distinct cells that have been identified by the NEXRAD software algorithm. In this case, this part of the line was beginning to strengthen and was rapidly becoming a significant threat to aviation.


As a comparison, below is the same line with the new color map applied. Notice the area looks much more pronounced given the warmer colors of yellow and slight hint of orange now being displayed. While there are still a few “soft” spots along this line, the newest depiction represents the threat more accurately. Notice, however, the more intense cells along the northern and southern extent of this line don’t change appearance significantly preserving the original ForeFlight characteristics.


Synthetic Vision and Forecast Weather Guidance with MOS in ForeFlight Mobile 6.6

ForeFlight Mobile 6.6 is now available for download on the app store.

Synthetic Vision Advances ForeFlight Mobile’s Hazard Awareness Platform

We are thrilled to announce that Synthetic Vision plans are available on the iPad with ForeFlight Mobile version 6.6 or later and are available for United States and Canada coverages. ForeFlight Mobile Basic + Synthetic Vision is $99.99/year, ForeFlight Mobile Pro USA + Synthetic Vision is $174.99/year, and ForeFlight Mobile Pro Canada + Synthetic Vision is $174.99/year.

Synthetic Vision takes our hazard awareness platform to the next level with a three dimensional representation of terrain and obstacle hazards, airport markers, runways, and water features. Check out our highlight video narrated by mapping team member and lead developer for Synthetic Vision, Malcolm Toon, and also visit our web page to learn more about Synthetic Vision.

How To Buy Synthetic Vision

For existing customers: As an existing customer, upgrading to a Synthetic Vision plan requires that you renew your existing subscription. When you renew/upgrade on our website, you’ll receive a credit for the unused time on your existing subscription plan which then applies to the combined renewal/upgrade purchase price.

To change plans, login at or go to and use the email address associated with your account. iTunes credit or gift cards may not be used towards Synthetic Vision upgrades for existing accounts.

For new customers: As a new customer, you can purchase a ForeFlight Mobile + Synthetic Vision plan via the App Store or via our website at iTunes credits and gift cards may be used towards the purchase via the App Store.

ForeFlight Mobile Expands Forecast Weather Guidance with MOS

ForeFlight Mobile 6.6 also delivers a new forecast weather product called MOS for better preflight weather briefings. MOS enables local weather forecasters to create TAF-like forecasts for airports not served by official National Weather Service TAFs. MOS is great for aviation use because it updates hourly and can be highly tailored for local weather effects. Our Weather Scientist, Scott Dennstaedt, wrote this article to explain more about MOS. The MOS feature is available to Basic and Pro subscribers.

Access the MOS forecast in the Maps view by tapping on an airport.

Access the MOS forecast in the Maps view by tapping on an airport.

Additional updates

ForeFlight Mobile Standard is now ForeFlight Mobile Basic. Same great features and price, just a different name.

ForeFlight Mobile Version 6.6 Is Available On The App Store

ForeFlight Mobile version 6.6 is a free download for subscribers via the Apple Store. For additional information, be sure to review our Pilot’s Guide. You can also download the Pilot’s Guide onto your device using the built-in catalog in the Documents view.

ForeFlight Synthetic Vision is Coming

Luminous terrain

We are excited to unveil our visually stunning, high performance synthetic vision platform for ForeFlight Mobile. With features like luminous terrain, night sky, FAA styled runway numbers, and a brilliant obstacle awareness system, we believe you will find flying with ForeFlight Synthetic Vision a joy. Synthetic Vision plans will be available on the iPad with ForeFlight Mobile version 6.6 or later and are available for United States and Canada coverages. ForeFlight Mobile Basic + Synthetic Vision will be $99.99/year, ForeFlight Mobile Pro USA + Synthetic Vision will be $174.99/year, and ForeFlight Mobile Pro Canada + Synthetic Vision will be $174.99/year. Synthetic Vision plans will be available soon after the Christmas holiday. Start the New Year with a significant upgrade to your flight bag! Until then, enjoy the ForeFlight Synthetic Vision highlights shown below or on our Synthetic Vision web page:

Synthetic Vision Comes Alive with Stratus

The Stratus 2* has a built-in AHRS that drives real time pitch and roll indications on the attitude indicator within the SSV-iPad-with-Stratusynthetic Vision view. The award-winning Stratus also delivers subscription-free weather, ADS-B traffic, and GPS position and attitude information—all from a wireless receiver that fits in your pocket. Because Stratus is made for ForeFlight, it delivers seamless app integration and simply works the right way.

It’s Not Too Late! Give yourself a last minute gift and be ready for Synthetic Vision. Order Stratus 2 by 5pm Central Time on December 23 for delivery on Christmas Eve. Order by Friday, December 19 to avoid expedited shipping costs.




Stratus is Made in the USA.

*Stratus is not required to run Synthetic Vision.

ForeFlight Mobile Expands Forecast Weather Guidance with MOS

What is MOS?  No, it’s not that green stuff that may grow in your garden. But you will find MOS in the latest release of ForeFlight Mobile. MOS stands for Model Output Statistics. As the name suggests, MOS is derived from the output of weather prediction models developed and run by research meteorologists at NOAA. The use of MOS has actually been around for decades, but has only recently been introduced for aviation use.

MOS Makes Model Forecasts Better

MOS in the Maps viewWeather prediction models provide forecasters with long and short term guidance in the form of various meteorologically significant variables like pressure, humidity, temperature, and wind. Meteorologists compile this information and other derived data and display it on standard charts and diagrams to make a forecast.

These models are certainly useful, however they do not automatically produce a point forecast for a specific town or airport as pilots would expect to see for preflight planning. Enter MOS! The job of MOS is to take the “raw” model forecast and attempt to improve upon it using a statistical method to produce an objective and more useful site-specific forecast that also attempts to quantify uncertainty.

To make the original model forecast better, MOS takes into account an historical record of observations at forecast points (such as airports), removes any known systematic model biases, and quantifies any uncertainty (like precipitation or thunderstorm chances) into probabilistic forecasts.

MOS Makes Model Forecasts Useful for Aviation

MOS transforms the model data into weather elements that the model does not directly forecast. This includes sensible weather elements basic to aviation such as sky cover, ceiling height, visibility, wind speed and direction, the probability of precipitation, and the precipitation type.

MOS is such a great tool that it’s used by local NWS forecasters all over the US to create more accurate local forecasts for specific towns or cities. These forecasters also rely on MOS as one form of guidance to construct and amend a TAF. While TAFs provide the official forecast for 635 airports throughout the US and its territories, MOS provides weather guidance for over 1800 airports including some military air bases.

MOS is especially accurate in the first 6 hours and, since it is location specific, will usually provide you with more detailed guidance than using the area forecast (FA) alone. One thing to note, however, is that MOS should never be used for legal requirements such as determining an alternate on an IFR flight plan (more on that below).

Another distinct benefit to pilots is that MOS is updated hourly. You’ll get a refreshed forecast at an airport that will tend to track better with the actual weather than with the area forecast. Moreover, MOS is highly tailored for each airport. So if the airport is in a valley or near an ocean or next to a river, MOS is aware of the nearby terrain features and local effects of the weather for that airport.

Mind the Limitations

MOS is a great tool for better understanding the local weather picture during your flight planning, but there are some important limitations you should be aware of when it comes to MOS producing a TAF-like forecast. MOS cannot forecast multiple cloud layers as you see in a TAF. Except for when the forecast is shown as clear, a single fixed cloud layer is the best MOS can do. It cannot directly forecast showers in the vicinity (VCSH), thunderstorms in the vicinity (VCTS) or fog in the vicinity (VCFG), nor can it forecast precipitation intensity. Additionally, MOS cannot forecast non-convective LLWS and no significant weather (NSW), both of which can appear in a TAF. MOS is also unable to predict a variable wind and can’t tell the difference between rain and drizzle or mixed precipitation including freezing rain and ice pellets. Currently, MOS only provides domestic forecasts -so you won’t see MOS forecasts for airports outside of the US.

Finding MOS in ForeFlight

The MOS forecast option is available to all subscribers with ForeFlight Mobile 6.6 and to find it in the app, simply select an airport or weather station from the Maps view. In the pop-over window, tap the Forecast tab at the bottom. Then press the MOS button to reveal this new forecast product.

Access the MOS forecast in the Maps view by tapping on an airport.

Access the MOS forecast in the Maps view by tapping on an airport.

Similar to the way Terminal Area Forecasts (TAFs) are translated, you will see one or more sections that represent an aviation forecast for that airport over the next 24 hours. You can also view MOS forecasts in the Airports view. Tap on the Weather tab, then MOS:

You can also view the MOS forecast in the Airports view by tapping on the Weather tab.

You can also view the MOS forecast in the Airports view by tapping on the Weather tab.

Next time you plan a flight, take MOS for a test drive!

ForeFlight Mobile’s Helper Messages Make Filing Easier

ForeFlight Mobile has two kinds of helper messages to assist with the flight plan filing process. These messages ensure that you file with accuracy and avoid potential issues with ATC down the line.

The first type of helper message is a warning. Warnings are new in ForeFlight Mobile version 6.5 and appear when something doesn’t look quite right in the Route or Altitude fields.

In the route field, the main thing ForeFlight will be looking for is an invalid or mistyped fix. The warning gives you an opportunity to double-check that you have entered the route as intended before you file. There may be route codes or other route elements that the app is not familiar with and so you can still file your flight plan when this warning is triggered.

An example of a route element warning.

An example of a route element warning.

A warning will also be triggered if you select an altitude that does not agree with your direction or type of flight:

An example of an altitude warning where an altitude of 12,000 was chosen for an eastbound IFR flight.

An example of an altitude warning where an altitude of 12,000 was chosen for an eastbound IFR flight.

Similar to the route field warning, the altitude warning gives you a chance to ensure you have entered the proper altitude before you file.

The second type of helper message is an error. Errors are more restrictive in that they prevent you from filing a flight plan until they are corrected. Errors include things like: not enough fuel to meet required reserves, incomplete ICAO profile elements, and invalid departure times.

Not enough fuel error

An example flight plan error indicating not enough fuel to meet required reserves.

ForeFlight Mobile Receives Operational Suitability Approval on iPad and iPhone

We are pleased to announce that the FAA’s Aircraft Evaluation Group completed an evaluation of ForeFlight Mobile as an Electronic Flight Bag (EFB) solution and found the app to be operationally suitable as a “complete flight deck solution for continuous accessibility for the pilot.”

The approval letter goes on to say: “[The] ForeFlight Mobile application includes airport flight directory information and instrument departure and arrival procedures and charts for all of the US and Canadian IFR National Airspace System. The mobile application was evaluated and found to be operationally suitable.”

The Operational Suitability evaluation was completed on an iPad 2, however the approval covers the iPad 2 or newer, iPad Mini, and iPhone 3GS or newer hardware. In related efforts, the co-developed Stratus 2 ADS-B receiver with Appareo Systems has received approval for use in Part 121 aircraft operations. The Stratus platform enables the display of ADS-B weather on iPad and iPhone running the ForeFlight Mobile app, as well as WAAS-grade GPS positioning for ownship display. Professional operators with access to inflight weather routinely report saving thousands of pounds of gas by being able to see ahead and work with flight operations on inflight re-routes.

In the United States, operators falling under FAR Part 91K, 121, 125, and 135 are required to have formal FAA authorization to use EFB solutions inflight. This letter makes it even easier for operators to obtain approval for use of ForeFlight Mobile on iOS devices. ForeFlight will share copies of the letter to interested customers seeking this approval.

For more information about obtaining ForeFlight Mobile and Stratus approvals, contact ForeFlight at