METR 360                                                                                                                                                                                                                                            Lab 9

Lake Effect Snow Forecasting

Forecast models have become very accurate on the synoptic scale, although human forecasters can usually improve on their accuracy.  The more difficult 21st century weather forecast challenges occur with smaller, mesoscale forecasts, mainly due to problems with model resolution and assumptions.  Lake effect is a classic example of a local forecasting problem in which a synoptic situation can be well understood and forecast but the scale of the weather phenomena make individual location forecasts problematic.  In this lab, we will study three cold season examples and in each case, lake effect was a significant element.  After studying the synoptic maps, data, and numerical guidance, you will be asked to think about the lake effect component.  To see the maps, click on the links below.

 

Case 1: Classic set up over Lake Michigan 

 

In Fall 2013, the lake effect station chosen for WxChallenge was Grand Rapids, MI (KGRR).  Downwind from Lake Michigan, this city experienced light snow overnight and during the day on December 7.  Click here for the radar loop.  KGRR is east of the lake.  The 12Z surface map showed an Arctic High west of Michigan with a pressure gradient over the lake (click here for loop).  Other information and observations can be found on the 850 hPa map, 500 hPa vorticity map, and 250 hPa map, all from 12Z on December 7.  The Great Lakes water temperature map from Dec 5 is also available.

 

For this lab you must answer questions 1-7 in a text or Word file.  Start here:

 

1. Based on the observed and forecast conditions from the map links already given, write a discussion in the NWS format.  Your discussion must describe what’s happening in enough detail so that a professional meteorologist will understand both the general synoptic situation and the nuances that pertain to lake effect.

 

2. Based on the forecasts for 12Z December 7, both graphical (NAM 24 hour MSLP and the 24 hour surface prog) and digital for Grand Rapids in particular (NAM MOS and Grid Extracts), what is an appropriate and consistent forecast for Grand Rapids, MI from 00Z Dec 7 to 00Z Dec 8?  Include all the usual elements, i.e., temperature, precipitation type, precipitation amount, wind, and sky cover.

 

Case 2:  Buffalo lake effect “ Snow Blast”

 

On November 18, 2014, Buffalo experienced one of the most intense lake effect squalls in history.  Images of the wall of snow across Lake Erie are iconic on the Internet:

 

 

The radar loop for this case shows a very different reaction than you saw in the Grand Rapids case and the observations show a prolonged period of measureable snowfall.

 

As in the first case, you must become familiar with the surface map for 00Z Nov 18,  surface map loop,  850 hPa map, 500 hPa vorticity map, and 250 hPa map.  You also have, as before, the Great Lakes water temperatures from Nov 15. 

 

For this Buffalo case, the resulting lake effect squalls were very different in terms of intensity as well as structure.  Here are your questions:

 

3. How is the synoptic setup different from the Grand Rapids case?  Wherever possible, be quantitative.

 

4. How do these conditions work to create such a different lake effect event?

 

5. Was the forecast guidance (MOS in an Excel spreadsheet, and 24 hour surface prog) helpful in guiding you to the correct forecast?  Why or why not?

 

Case 3: Syracuse 2012

 

In the Fall of 2012, WxChallenge chose Syracuse, NY as their northeast station.  Late in the day on Nov 28, radar showed what appeared to be a long single lake effect band set up on the south shore of Lake Ontario.  Observations from 12Z Nov 28 to 12Z Nov 29 featured a number of hours with S- but little accumulation which may indicate that the long shoreline band was not as strong as it looked.

 

You again have a surface map loop for the same times as the observations and, for 00Z Nov 29, the U.S. surface analysis, 850 hPa map, 500 hPa vorticity map, and 250 hPa map.  The Great Lakes water temperatures were from Nov 29.  Your MOS digital forecast was from the NAM that was initialized at 00Z Nov 28, 2012 and the 24 hour surface prog was based on the same 00Z initialization.

 

Please answer the following:

 

6. Was this lake effect or not?  Justify your answer using the information given.  

   

7. The observations showed 0.00" measurable precipitation.  Considering the well-developed long band, how could there be 0 precipitation?

 

8. Assess the MOS guidance for this case, knowing what the observations were.  Would you have made an accurate forecast using this guidance?  Why or why not?

   

   

Send your text or Word file to Jerome.Blechman@oneonta.edu by Wednesday, Nov 8.