Scientific Forecaster Discussion

000 fxus63 kiwx 231055 afdiwx Area forecast discussion National Weather Service northern Indiana 655 am EDT Tue Apr 23 2019 Synopsis... issued at 356 am EDT Tue Apr 23 2019 A cold front tracking across the region this morning may produce an isolated shower this morning, but otherwise dry conditions are expected today. Northwest winds gusting to 15 to 25 mph behind the front will bring cooler air to the region and slowly falling or steady temperatures this afternoon in the 50s and 60s. A ridge of high pressure will settle across the area tonight with dry weather into Wednesday. Additional light rain chances arrive for Wednesday night and Thursday. && Short term...(today and tonight) issued at 356 am EDT Tue Apr 23 2019 Lingering isolated showers/storm early this morning will give way to dry weather this afternoon into the first part of Wednesday. Band of prefrontal showers gradually filled in overnight coincident with 500-1000 j/kg MUCAPE axis. This elevated instability was driven by narrow low level moisture axis and plume of steep mid level lapse rates. These ingredients have shifted into central Ohio as of 08z. Upper trough axis and associated cold front will be tracking across the area this morning, with additional isolated showers possible through mid to late morning. By late morning/early afternoon, mid/upper level forcing becomes less impressive as primary upper vort Max approaches the eastern Great Lakes, with just weak trailing sheared vorticity maximum across the Ohio Valley. The more diurnally favored timing of the cold front should favor afternoon shower/storm development well south/southeast of the local area. Temperature trends tricky for today with period of falling temps across northwest half of the area this morning, likely followed by near steady trend this afternoon due to competing effects of diurnal tendencies and cold advection. Stratocu should also rapidly fill in this morning in Post-frontal environment. Skies should begin to clear from north to south this afternoon as much drier low level air advects southward. By this evening, surface boundary is expected to be stalled from southeast Missouri to eastern Kentucky while weak 1018 mb anticyclone builds across the southern Great Lakes. Dry air mass, diminishing winds, and low level thermal troughing settling across the region may allow for some patchy frost formation for early Wednesday morning across northern portions of the area. && Long term...(wednesday through monday) issued at 356 am EDT Tue Apr 23 2019 A rather complicated upper level flow pattern will characterize the mid week period. Mid/upper level deformation axis will prevent next sheared vorticity Max emanating from southwest Continental U.S. Cut off negative height anomaly to make only modest northward progress late Wednesday into Thursday. Some elevated moisture return with this feature should increase light rain shower chances for areas south of Route 30 Wednesday night into Thursday. Confidence is on the low side with northward extent of these chances, as low level dry layer may be difficult to overcome given overall weak nature of this forcing. By late Thursday, next northern stream wave will rapidly push across the southern Great Lakes but deeper moisture will likely be tied well to the south across the lower Ohio Valley. Reinforcing cold air advection behind the northern stream wave for Thursday should result in below normal temps for end of work week, with additional northern stream disturbances keeping warmer low level profiles suppressed to the south. Periodic isentropic/moisture advective forcing with this active northern stream will keep periodic chances of rain in the forecast for much of the Saturday through Monday period. Later forecasts will need to further refine temporal detail with these chances as predictability in timing these progressive northern stream waves difficult at this forecast distance. && Aviation...(for the 12z tafs through 12z Wednesday morning) issued at 649 am EDT Tue Apr 23 2019 A strong cold front was just northwest of sbn with a good wind signature/fine line on the radar data. IFR clouds will move southeast behind the front and are expected to spread across northern Indiana. Have updated the tafs for the timing of these lower clouds. Went with IFR at sbn given lower IFR clouds just upstream. These clouds will persist through a good part of the day, but should lift by this evening as high pressure builds into the region. && Iwx watches/warnings/advisories... in...none. Michigan...none. Ohio...none. Lm...Small Craft Advisory until 5 PM EDT this afternoon for lmz043. Small Craft Advisory until 11 am EDT this morning for lmz046. && $$ Synopsis...marsili short term...marsili long term...marsili aviation...skipper Visit US at www.Weather.Gov/iwx

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