City #2: Billings, MT (KBIL)

We are done forecasting for Pensacola and now must divert our attention roughly 2,000 miles northwest to Billings, MT. Has anyone ever been to Yellowstone? If so- I'm jealous. We will be forecasting for this city from October 8-18. Forecasts are still due by 00 UTC or 8 PM local time. We are forecasting for the 24-h period 06-06 UTC which is 12 AM - 12 AM local time (MDT) for those looking at the Billings NWS WFO page.

Alright, time to stalk the airport and surrounding area. The airport and city lies in the Yellowstone Valley at an elevation of roughly 1000 m AMSL. Surrounding the city are clusters of 100-500 m high hills with the closest being to the north and southeast.



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So we have some terrain slight that may influence our forecasts. Mental note made.

Now just to get an idea of what to expect, time to look at some monthly climate data. Remember, this is just to get a crude idea about what is the average daily temperature range but there are always exceptions.

Month     Daily Max     Daily Min
Sep             73.1                  47.5
Oct             59.4                  37.1 

Now to move onto what's going on weather-wise.

Large-scale Pattern:

A look at forecast 500-hPa heights according to the GFS shows a persistent  trough over the region. Looking at some model output for other mass fields shows that weak surface fronts (cold fronts) may provide forcing for ascent in the near-term for some rain showers and even snow showers. Pay attention to the wind direction as the northerlies may usher in cold, Canadian air.

What to watch out for (IMO):

• Shortwaves traveling along the mean trough that can provide forcing for precipitation.
• Weak fronts if the models pick up on them which would impact temperatures.
• Wind direction should be very important given the topography, mainly westerly or zonal winds should result in warmer, drier conditions.
  

 Tips/Comments for Forecasting in General:

• Check out the current weather first via satellite, radar, surface observations, METAR, etc. You have to understand the present before you can look to the future.
• Get a feel for general pattern from NAM, GFS, etc. (available from here and here, for example). Identify the general pattern of low and high surface pressure systems and their progression, temperature advection at 850 mb, moisture at 700 mb, vorticity at 500 mb and the general jet structure at 300 mb. Make sure you are focusing your attention on Billings.
• Look at forecast model soundings for the period for KBIL.
• Compare your idea for values with MOS (model output statistics).  Keep in mind these are instantaneous output values and you can always have values above/below that between output times. 
• Read the Billings, MT WFO forecast discussion for KBIL.

Tips/Comments for Forecasting for High/Low temperature (Fahrenheit):

• Recall such basics as nighttime radiative cooling and daytime solar radiative heating, both of which are affected by cloud cover. 
• Frontal passages can affect your temperature forecast. Pay attention to the forecast timing of such frontal passages.
• With KBIL, terrain may be an issue. If the winds are downslope or likely westerly and northerwesterly given the location of the airport, then there may be some subsidence warming. Recall that as air falls adiabatically, it warms.

Tips/Comments for Forecasting Wind Speed (knots):

• NWS outputs wind speed in mph so if you are comparing your forecast value to theirs keep that in mind. Otherwise the models output wind speed (WSP) in knots.
• Look through METAR or surface obs for wind direction and temperature changes or try to spot it on the Billings, MT radar.

Tips/Comments for Forecasting Precipitation (inches):

• Snow?! Looks like it at KBIL! We forecast for the liquid equivalent of precipitation, or exactly what the models output in inches. So if there is a forecast for 6 inches of snow, do not put "6.00" or you will be filled with regret and sadness.
• Take a look at some higher-resolution models (e.g. WRF)
• What does the HPC show?
• Take a look at some ensemble data (e.g. SREF)
• Most products you will be looking at will output the QPF in inches already so no conversion is necessary.

What if I'm afraid I'll miss a forecast?

•  When making a forecast for the first day only, always select the "Guidance" option for the "Optional Forecast for Future Days" days just in case you forget.
• It is advisable that you enter your forecast for the next couple of days when you enter your Day 1 forecast. They are not counted towards any score and it is just a good way to possibly save your score if you happen to forget to forecast the next day. However, you realistically likely only have enough time to forecast for the first 24-hour period so I always just select "Guidance" anyway.

If you have any questions, comments please feel free to comment on this post! Best of luck with forecasting for Billings! Go SBU!!!