FORECAST FOR DEKALB AND VICINITY, 7/24/08, 1 PM Today...slow increasing cloudiness, with mainly high clouds this afternoon. High of 83 degrees. South winds around 10 MPH. Tonight...becoming cloudy with a chance of a shower or thundershower after midnight. Warmer and muggy with a low of 64 degrees. Southeast winds around 5 MPH. Tomorrow...partly cloudy, warm and humid with a chance of an early morning and an afternoon shower or thunderstorm. High of 86 degrees. Southwest winds at 5 MPH. Extended outlook...Saturday through Wednesday... Saturday...variable cloudiness, warm and humid with scattered thunderstorms, mainly predawn. Low in the middle 60s. High in the middle 80s. Sunday...partly cloudy and less humid. Low around 60. High in the lower 80s. Monday...mostly sunny. Low in the lower 60s. High in the lower or middle 80s. Tuesday...partly cloudy. Low in the middle 60s. High in the middle or upper 80s. Wednesday...variable cloudiness with a chance of a thunderstorm. Low in the middle or upper 60s. High in the middle or upper 80s. **************************************************************************** CLIMATE DATA: Yesterday's high, 80 degrees; last night's low, 60 degrees. The average high/low temperature is 83/62. We have had no rain at the DeKalb campus over the last 24 hours ending at 7 AM this morning. Forecast was for 78/56; sunshine warmed us up a bit more than expected yesterday. We have had 5.25" of rain this month. On average, we should see 4.26" of liquid equivalent by July 31. We have had 24.94" of liquid equivalent so far this year. By July 31, our average annual liquid total should be 21.88". **************************************************************************** SEVERE/HAZARDOUS WEATHER OUTLOOK: There could be isolated storms Friday night that could produce gusty winds and a brief downpour. At this point, the severe threat is probably at or just under 5% for marginal severe wind gusts, so I will decline to mention any severe at this point. The severe activity, including heavy rainfall, should stay in Iowa and Missouri through western Illinois through tonight, and again on Friday (as well as up into Wisconsin). **************************************************************************** PRECIPITATION: Tonight into Friday night: .01"-.25", and 30% coverage, with isolated heavier amounts. **************************************************************************** FORECAST DISCUSSION: A "DeKalb doughnut" warning is in effect for this weekend as we're now seeing clear signs that the nasty activity to our southwest and approaching from the northwest will mostly go north and south of the I-88 corridor and much of north central and northeastern Illinois this weekend. That's not to say we won't get any rain or thunderstorms, but those that occur should be brief, with a very high probability of being below severe limits, and with scattered coverage at best. Although temperatures will be a bit uncomfortable, I see no heat waves coming...and with just two 90 degree days under our belt when 23 are expected by the end of September, that's saying something. On the surface map this morning...a low over central Nebraska had a warm front extending across southwest Missouri to southern Georgia. This system has produced extremely heavy rains and flash flooding over southern Iowa. reports from there include 6.5"-9" of rain across several counties; Mount Ayr reports 6.5" of rain, with an area northeast of Prescott, IA getting 7.5", and a nearby lake getting 9". That activity is now in northern Missouri, with flash flood warnings there as 3" to up to 8" of rain could fall in several counties before the afternoon is out. A low north of Buffalo, NY had a warm front eastward into central Maine, with a cold front extending south and just clearing the Atlantic seaboard to Charleston, SC to southern Georgia. Much of New England is under the gun for a squall line to hit later today. A low over central Manitoba had a cold front southwest to southern South Dakota. That front gets here tomorrow night, with a wind shift, a drop in humidity, and slightly cooler temperatures for a few days. In the Rockies, heat and humidity will bring scattered thunderstorms there. High pressure dominated the western U.S. with continued very warm to hot temperatures; the only exception is along the Pacific coast, where it will remain cool to comfortable. In the tropics...Tropical Storm Dolly is fading fast as it crosses over the Mexican border from southwest Texas, but not before producing 100 MPH wind gusts and damage across the southern part of the state. Otherwise, a large tropical wave in the eastern Atlantic is still under relatively cool water and shear, and is not expected to develop for another few days. For more information on Dolly and the tropics, please see http://www.nhc.noaa.gov . Our forecast problems...the system coming in late tonight through early Saturday, and then next week. Today...high clouds started moving in a bit earlier than expected, but this will have no significant bearing on our temperatures today. In fact, I actually bumped up our high two degrees based on the high we had last night, and the somewhat warmer low last night. Highs in the lower 80s should be common areawide, with a south winds already at 10 MPH. Tonight through Friday night...the warm front won't make it through here, which is really bad news for southeastern Iowa through west-central and southwest Illinois, which will not only get slammed today, but get whammied again tomorrow with more very heavy rainfall. But, this will help wring out a lot of the moisture before it gets here. As a result of that and relatively weak upper support in our area as the system goes through, along with poor timing of features...we should come through this with heavy rain to our south and west, and big storms in Wisconsin tomorrow before they fade away in the coolness of the overnight hours as they move in late Friday night. So, I will keep chances at either 30% to 40%, mainly for one wave just nicking us late tonight and early tomorrow, a chance for airmass thunderstorms tomorrow afternoon (30% at best), and then between midnight and say 8 AM Saturday as the cold front swings through. the humidity will be pretty high, with dewpoints well into the 60s. That means lows will warm to the middle and upper 60s, with highs in the middle and upper 80s on Friday. Saturday...the front goes through early, and the humidity slowly drops throughout the day as drier air comes in. Look for highs still making it into the middle and maybe upper 80s, as the cooler air will lag the front some. Next week...no significant changes to the forecast, although we might get clipped at some point with a thunderstorm as the warm and humid air moves back in Tuesday and Wednesday, before another cold front ends that. No hot weather is expected, just normal summer heat and humidity...and with highs in the 80s all week, that's tolerable by any stretch of the imagination. In conclusion, look for near to slightly below average temperatures and below average precipitation over the next 10 days. Overall a relatively quiet weather period...locally, anyway. We need it. ******************************************************************************* Gilbert Sebenste ******** (My opinions only!) ****** Staff Meteorologist, Northern Illinois University **** E-mail: sebenste@weather.admin.niu.edu *** web: http://weather.admin.niu.edu ** *******************************************************************************