Flying Weather: CWSU Salt Lake City Volume 3 Issue 2 Aviation Weather Safety in the Intermountain West December 2019 Wintertime in the West: What Pilots Should Know! By: Rick Dittmann, Meteorologist-in-Charge, NWS CWSU Salt Lake City During the cool season in the western United State, the jet stream migrates farther south. This storm track is responsible for bringing much more active weather to the region. These storms bring increased risks for icing, turbulence, lower visibility and runway snow and ice, among other hazards. As opposed to the summer months when brief showers and thunderstorms can lower visibility and ceilings for hours, these larger storms systems can last for days. General aviation pilots are at risk from these large storms, and should be thoroughly briefed about impending weather changes before flying. A myriad of resources exist in addition to the standard flight service weather briefings. Social media has greatly expanded the weather data availability for everyone. National Weather Service Fore- cast Offices are all present on social media with Twitter and Facebook accounts in addition to their web page presence. The Aviation Weather Center (AWC) in Kansas, City, Missouri, also maintains a web page and social media presence as do most Center Weather Service Units (CWSUs). As an example, here is an explanation of upslope and downslope conditions and the hazards they bring I saw the @NWSPocatello office tweet out. Pilots who follow these accounts can receive detailed and cur- rent weather information before and even during flight. Main- taining a weather informed awareness can keep you one step ahead of winter’s challenges. What’s Inside? NWS Great Falls Assists with Airfield Winter Weather Planning Correlation of Snowfall to Airport Operations NWS Boise Hosts Boise Airport Operations Crew at Me- dia Workshop Winds, Atmospheric Rivers, and the Sierra—Using En- hanced DSS Wording for Extreme Aviation Events 1 NWS Great Falls Assists with Airfield Winter Weather Planning By: Jane Fogleman, Meteorologist, NWS Great Falls On October 3rd, 2019, The National Weather Service (NWS) Great Falls Weather Forecast Office (WFO) sent two team members to the Helena Regional Airport (KHLN) Annual Snow Plan Meeting. KHLN is a public air- port located two miles northeast of Helena, the capital of Montana. It has four operational runways, three of these runways are asphalt and one runway is turf. This airfield is surrounded by the Little Belt Mountains to the northeast, the Crazy Mountains to the southeast, the Continental Divide south through west, and the Lewis Range to the northwest. Within a 2.5 km radius of the airfield, elevations change from the lowest point at 3800 feet to the local heights of the South Hills at 5400 feet. The airport, itself, is located at 3875 feet. Ser- vicing Alaska Airlines, Allegiant Air, American Airlines, Delta, and United Express, Helena Regional remains one of the busiest airfields in the state. The majority of the flights serviced by KHLN are general aviation flights, with the second most serviced aircraft being military flights. Helena Regional Airport has the distinc- tion of being the only airport in the state that can land Very Large Air Tankers (VLAT). This is very important during fire weather season and operations. With the unique and complex surrounding topography, weather forecasting for this airfield can indeed be a challenge. As part of an effort to ensure that Team WFO Great Falls is meeting the needs of our Aviation Part- ners, Warning Coordination Meteorologist (WCM), Megan Syner, along with Aviation Program Leader and Meteorologist, Jane Fogleman, attended the Helena Regional Airport Snow Plan Meeting. Helena Regional Airport Authority Airport Director, Jeff Wadekamper, lead and facilitated the discussion. Among the numer- ous topics discussed were The NWS Automated Surface Observing Systems (ASOS) new model for KHLN, as well as the concerns of airfield management in reference to runway surface deicing efforts. This meeting pro- vided an opportunity to give and receive feedback, and to remain current on the needs of the KHLN airfield mission. The communication shared during this meeting enables the trusted relationship building in this im- portant partnership, as we work together to maintain a high level of safety “...for the protection of life and property…” Helena Regional Airport, Helena, MT 2 Intermountain West Aviation Weather Safety (IWAWS) Workshop 2020 By: Sarah Rogowski, Meteorologist, NWS CWSU Salt Lake City Aviation weather and safety have significant impacts on both commercial and general aviation operations. The Intermountain West has unique and challenging aviation weather threats throughout the year. To pro- vide enhanced communication and collaboration of these forecast challenges, the third Intermountain West Aviation Weather Safety Workshop is being proposed. In addition to increased information sharing amongst partners/forecasters, this workshop provides an invaluable outlet to improve communication with a variety of users. This communication can be used to deepen customer/user relationships as a means to expand the Weather Ready Nation program. IWAWS 2020 will be hosted in Reno, NV at the Desert Research Institute on Friday, May 29 and Saturday, May 30. Friday will focus on NWS Operations and Meteorology and Saturday will focus on General Aviation and Winter Weather Impacts. The morning presentations on Saturday will include WINGS credit for attend- ing pilots. Pilots and Meteorologists are welcome BOTH days of the conference. IWAWS 2020 is free of charge!! There will be a call for abstracts in January for those that want to present an oral presentation or a poster. Monitor weather.gov/zlc for more information as it becomes available, including conference registration and the agenda. Photo courtesy of Dawn Johnson, WFO Reno & IWAWS Team Member 3 Correlation of Snowfall to Airport Operations By: Michael Matthews, Meteorologist, CWSU Washington (ZDC) Winter weather, specifically snow, is one of nature’s great equalizers, get enough of it and it can bring any community to a grinding halt. From Boston to Detroit and Denver to Salt Lake, no city is immune. At our na- tion’s busiest airports, the impact from snow events is even greater. However, with that said not all airports react equally. For example, as you might expect ATL (Atlanta) is impacted by a 2 inch snowfall event far more than Minneapolis. But what about Minneapolis vs Detroit, Salt Lake vs Denver, or the nation’s largest market New York City (EWR, JFK & LGA). To answer those questions you need to dig a little deeper, and that is what this study and tool is about. At its core it is a very simple study, merely a correlation between how much snow was measured at an air- port in a day and how many operations (departures + arrivals) occurred. The real work came in selecting the right events for each airport so that snow could best be isolated as the determining factor for the reduction in operations. For example, if a significant amount of ice or freezing rain was observed, those events were thrown out. Ice and freezing rain have a significant impact on any airport almost regardless of how much falls. If most of the snow was observed at non-peak operational hours, those events were thrown out. The same goes for events on holidays, since operations are already low. More work was also done to find the nor- mal operations for each airport. Average operations can change from year to year, season to season, and even more so by day of the week. 4 Correlation of Snowfall to Airport Operations (cont.) By: Michael Matthews, Meteorologist, CWSU Washington (ZDC) Each of the graphs and tables take into account every snow event 1” or greater (for some 2” or greater) from the 2006- 07 to 2017-18 winter season that satisfy our criteria. For the graphs, the points represent these events. The curved line is the best-fit curve, which shows a best guess for how an airport might be impacted by a given snow amount. For the individual airport plots the red and green curves are more or less confidence intervals. The further the red/green line is from the best-fit black curve, the more variability that airport has in operations given a snow amount. As you can see each airport is a little different and can vary greatly in the number of operations. One example of this can be seen by looking at 8 inch snowfall events at JFK. Over the time frame five times around 8 inches accumulated at JFK, however percent normal opera- tions vary from as high as around 70% to as low as around 15%. This variability can be from a number of reasons, some of which can have nothing to do with weather. For that reason this isn’t a singular tool to forecast how an airport will react to a forecasted snow event, but rather one of the tools in the box to give a better idea of how an airport has done in the past to better prepare for future events. In fact this tool has been presented to FAA Command Center and aviation partners in hopes that it can help next day planners. Airlines on one hand do not want to cancel flights a day in advance; however, planners need an idea of how many operations an airport may get given a forecast event. This tool helps to bridge that gap. The tool itself is a collaboration between a National Weather Service Meteorologist at the Washington ARTCC Center Weather Service Unit (Michael Mathews) and a Meteorologist at Southwest Airlines (David Dillahunt). The tool is also valuable in comparing airports and seeing how one does compared to another. The group plots are the best for comparing airports close by. Moreover, in the first graph shown above, of the major airports out west that get snow, SLC does the best with any snow amount.