DuPage Area Forecast
Prepared by NEXLAB, the College of DuPage Meteorology Department
------>LAST UPDATED 10/24/2008
Date: Oct 24, 2008 Time: 1:00pm
Short term and critical weather discussion:
Area of concern for this period will be any redevelopment of showers associated with cut off low currently spinning over central IA. Once this low moves off to our East very cold air mass will take over the Great lakes region for the next couple of days as we really start to feel the first blast of real winter air this season thus far.
GOES Satellite shows big low still cut off from main flow spinning over IA. Dry air is now becoming entrained and is drying out mid levels...resulting in decay of shower activity. However cloud cover will not let up and shower active is forecasted to redevelop later this afternoon into this evening. Vis shows huge swath of mid levels clouds over most of the Mid West and Northern Great Plains. The rain our FA received this morning was result of sfc boundary that made its way through the region. Showers will stay in the vicinity of the boundary and will not redevelop untill later on this afternoon. Behind the boundary winds remain out of the south but any isentropic forcing is forecasted to be limited. Both NAM and GFS are forecasting rather sloped theta surfaces but if the dry intrusion pushes its way further north then the amount of substance will be underforecasted by both models. GFS is doing bad job handling precip and will lean more towards the NAM solution for any precip in forecast. STL is currently reporting light showers...as the afternoon moves on this area of rain will rotate around the low and move North into our area.
As for tonight Models forecast big vort lobe to rotate around the base of the cut off low. NAM and GFS have strong UVV out ahead of this vort max. The problem with model guidance will be the mid level moisture. The dry intrusion now is making its way further north then forcasted by both models and might limit the amount of lift and the amount of moisture. Models are forecasting high rain fall totals. The amount of moisture might be over forecasted...The region will still receive rain tonight but models might be over forecasting the amount. Limited lift and moisture will be the reasons for undercutting models totals. Cloud cover will not break up at all tonight into the morning as this system continues to remain separated from the main flow and move slowly off the the NE. With the progression of the the low winds will shift from the South to the West.
Saturday morning our cut off low is forecasted to open back up and rejoin the main flow. The main jet will push this disturbance out of the area Saturday. Cloud cover will remain for most of the day Saturday but will be breaking up through out the afternoon into the evening. Another area of lift is forecasted to makes its way out ahead of the next wave out of Canada. This could keep skies cloudier then forecasted but will not put any chance of precip in forecast. Environment will just be to dry the main challenge with Saturdays forecast will be the amount of cloud cover. If models are right about the weak area of lift the skies could be mostly cloudy...But models have been having trouble forecasting the cut off low so will keep skies partly cloudy in the afternoon into the evening on Saturday. Dryer air will makes its way in behind the low and will clear out skies for Saturday night.
NORTHEAST ILLINOIS FORECAST:
Friday NIGHT: Cloudy and rainy. Lows in the mid 40s winds out of the south around 5mph
Saturday: Cloudy then turning Partly cloudy towards evening. highs in the mid 50s wind 10 to 15 mph out of the West
Saturday night: Partly Cloudy and lows in the mid 40s winds 10 to 15mph
Sunday : Partly Cloudy and windy high in the upper 40s winds 15 to 25mph
Extended Forecast Discussion:
Extend forecast...The before mentioned cut off low will make its way out of the Mid West Saturday night. Setting the stage for a very windy event on Sunday. The next wave will come crashing into the Mid West bringing with it very cold temps. As if the freezing temps werent enough winds will pick up and making for a windy day Sunday. Pressure Gradient tightens up with the passing of the trough axis. Out ahead of the cold front look for a few more clouds to develop but no major ceilings...air mass will be very dry. Behind the cold front temps will drop very cold. This should be the first major frost of the fall for most of the area. Lows on Sunday will drop to the lower 30s behind the front. The main pattern stays very amplified. Once this upper level trough makes it way off to the East long range models develop a big ridge in the West and move it East. This will warm us back up to the upper 50s by the end of the next week. The over all synoptic scale flow then turns rather zonal but still many days out.
- WOJ
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