Forecast Update Sunday January 9 2011

Current Surface Map @ 15z

A high pressure system is currently centered over Kentucky and northern Tennessee right now with another high pressure system located over northern Minnesota.   These areas of high pressure are keeping Northern Illinois free from any precipitation but allowing for the cold air to take hold over the area.   There is a low pressure system along the Gulf Coast of Texas that is triggering some heavy rain and thunderstorms in southeast Texas.   This low will move to the east and cause wintry weather over the Southeast during the next 24 to 48 hours.   Another low pressure can be seen over the eastern rockies.   This system is providing large snow totals for much of Colorado, Montana, Wyoming, and the Plain states.

National Radar @ 11 am Sunday Morning

 The national radar picture shows the large area of precipitation being generated by the Low pressure system sitting over the Southeast coast of Texas right now.  Again this system is going to reek havoc over the Southeastern U.S. for the next 24-48 hours.   Providing snow and even freezing rain for much of the Southeast.   The current radar picture also shows the snow over Colorado into northern Kansas, northwest Missouri, Iowa, Nebraska, and into the Dakotas.  Fortunately for Northern Illinois we are dry and we have clear skies for today, but come Monday and Tuesday the system over the central plains will be pushing off to the ESE so we will see an increase in clouds and we will have a chance of snow showers to begin the week from this system.

Upper Level Winds @ 250 mb 12z Sunday Morning

The winds at 250 mb shows very strong winds over the Southeast.  These winds will carry the low pressure system at the surface over Texas to the east over the next 24-48 hours.  There is also a trough over the Pacific NW where there is another low pressure system at the surface providing some precipitation for the Pacific Northwest.  This trough will also provide needed energy for the low pressure system currently over the rockies that is providing snow for much of Colorado and the northern Plains.  

700mb Winds, Temperature (C), Humidity at 12 z Sunday Morning

Looking closer to the surface at 700 mb we can see the moisture over the Gulf Coast and in the Plains.   Right now over northern Illinois we are dry so skies will be clear today, however, the northwesterly flow will keep us very cold for today.

MODELS:   The NAM and GFS appear to differ not necessarily in the progression of the systems but the intensity of the precipitation.   I am going with the NAM for today.  

NAM Model run includes Sunday night thru Tuesday morning.

Again, high pressure will dominate our weather for today.  However, come Monday the high pressure system is going to move off to the east, northeast as the low pressure system over the rockies progresses to the east, southeast.   As this low pressure system moves off to the ESE  Northern Illinois will experience snow showers Monday night into Tuesday morning.  

NAM prediction for Tuesday night.

The snow will linger into the afternoon and evening of Tuesday as depicted by the NAM model run for Tuesday @ 0z.   The GFS is showing a small chance of some light snow/flurries for Wednesday at the low pressure system moves into the Northeast.


SHORT TERM FORECAST FOR DEKALB AND NORTHERN ILLINOIS:

Today (Sunday):  Clear Skies High: 26 Winds: WSW around 5 mph

Sunday Night:  Increasing clouds.  Low: 15  Winds: ENE 5-10 mph

Monday: Mostly Cloudy High: 28  Winds: ENE 5-10 mph

Monday Night:  Cloudy with a chance of snow showers.   Low:  20  Winds:  ENE 5-10 mph.

Tuesday:  Snow showers continue.  High:  30  Winds:  NW 5-15 mph.

Tuesday Night:  Snow showers begin to end otherwise cloudy skies.  Low: 21 Winds: NW 10-15 mph.

Wednesday: Mostly cloudy.  High: 22

Thursday:  Partly Cloudy.  High: 18  Low: 9