Area Forecast Discussion
Issued by NWS Northern Indiana

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000 FXUS63 KIWX 231017 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 617 AM EDT Fri Apr 23 2021 .SYNOPSIS... Issued at 400 AM EDT Fri Apr 23 2021 High clouds will overspread the area this morning, but some sun is expected this afternoon before clouds increase again late this afternoon into tonight in advance of the next system to bring rain to the area. The greatest chances of rain will be late tonight and especially on Saturday. Conditions will dry out for Saturday night into the early parts of next week. A warming trend will be in store by Monday, with high temperatures by Tuesday back around the 80 degree mark. && .SHORT TERM...(Today through Saturday) Issued at 400 AM EDT Fri Apr 23 2021 Temperatures early this morning range from the lower 40s across southwest Lower Michigan/northwest Indiana to the mid/upper 30s across the southeast where weaker gradient has allowed for better radiational cooling. Frost advisory headlines will continue as is early this morning. Otherwise this morning, an area of showers continues to progress eastward across eastern Missouri where modest low level jet and strong low level theta-e gradient have been favorable. Without much in the way of strong mid/upper level support, feel that near term consensus guidance in diminishing this rain eastward across the lower Ohio Valley this morning is reasonable. For local area, just expecting an increase in high clouds this morning. These clouds should tend to thin this afternoon as an upper level wave dampens across the western Great Lakes early this afternoon with just some very subtle upper level height rises. Lingering subsidence inversion is high based, and should see some good mixing today up to around 825 mb. This would support previously forecasted high temperatures around 60 for most locations. Could have some slightly warmer temperatures, particularly across the east where renewed increase in high clouds late this afternoon will likely be more delayed until this evening. The biggest challenge for the near term will be timing the onset of better rain shower chances. 00Z RAOB from ILX/DVN last evening indicating some respectable dry low/mid level air to overcome with 700 mb dew point depressions on the order of 40 deg C. Dampened upper ridging will be in place across the region this afternoon with a gradual increase of advective forcing from the central Plains to the Mid MS Valley into early this evening. A more pronounced upper level wave will shift east out of the northern Rockies this afternoon while broader northern stream upper troughing works across the northern Plains. With disjointed nature of upper pattern and initially very dry low/mid level air in place, bulk of deterministic and ensemble guidance is trending to a slower onset of precip chances this evening. Did slow PoPs slightly from previous forecast, but this trend may need to be continued today in later forecast amendments. Lowest confidence in terms of precip onset timing is across southeast half of the forecast area as some indications that interactions of northern stream trough could set up initial preference to higher rain chances late tonight into early Saturday across northwest portions of the forecast area where low level convergence may be a bit more pronounced. Still expecting rain shower chances to eventually increase across the east and southeast on Saturday as the northern Rockies trough allows mid level deformation axis to shift across NE Indiana/NW Ohio. Still believe 0.25 to 0.50 inches of storm total rainfall is a good starting point with expected lowest amounts across the far southeast where forcing mechanisms will be slightly more progressive in nature on Saturday. Clouds/precip should limit high temperatures on Saturday to the mid/upper 50s. && .LONG TERM...(Saturday Night through Thursday) Issued at 400 AM EDT Fri Apr 23 2021 Colder air moves back into the area Saturday night behind the Saturday system. Temperatures dropping back into the 30s reintroduces frost/freeze potential questions. At this time, expecting low levels to remains mixed well enough through the night to prevent significant issues with lows expected in the mid-upper 30s. Mid and upper level height rises follow for Saturday night/Sunday with stronger return advective forcing likely to remain back to the west across the northern Plains to the western Great Lakes. Cannot completely discount very light precip on Sunday across the far northwest as this mid level moisture advection occurs, but will keep Sunday dry as dry low levels will likely be too much to overcome. Warm/moist advection ramps up more aggressively Sunday night into Monday as large scale flow amplification develops in response to digging southwest CONUS upper trough. Confidence remains high in transition to more active weather in this amplifying pattern with good deal of downstream baroclinicity midweek. The details in evolution of the primary upper trough regarding depth and timing remain of quite low confidence and split eastern Pacific flow leads to some downstream phasing uncertainty heading into the Wed- Thu period. Overall trend in medium range deterministic/ensemble means the past few cycles appears to be toward slower evolution which could keep an active period of precip chances into Thursday. Have maintained likely PoPs on Wednesday, but will have to monitor trends regarding strength of downstream upper ridging that could slow these higher PoPs. Confidence remains high in much above normal temperatures for Tuesday and Wednesday with Tuesday featuring best chance at some lower 80s high temperatures. Did also maintain iso thunder mention for Wed-Thu with lingering uncertainty on best chances given the lower confidence in timing large scale features. && .AVIATION...(For the 12Z TAFS through 12Z Saturday Morning) Issued at 611 AM EDT Fri Apr 23 2021 High pressure will allow VFR conditions to persist into this evening. High clouds are currently moving in ahead of a sprawling area of low pressure. Ceilings won`t start to come down until after 00Z, but should stay VFR through 06Z. After that, conditions will deteriorate rapidly at SBN with rain moving in, and IFR ceilings will be possible by Saturday morning. Not confident that rain will move into FWA before end of the TAF period due to presence of a dry slot with prolonged ridging in that area, so only went down to MVFR ceilings. Southwest winds will increase during the day today, and could gust around 20 kts. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...Frost Advisory until 9 AM EDT this morning for INZ005>009- 016>018-024>027-032>034. MI...Frost Advisory until 9 AM EDT this morning for MIZ079>081. OH...Frost Advisory until 9 AM EDT this morning for OHZ001-002-004- 005-015-016-024-025. LM...NONE. && $$ SYNOPSIS...Marsili SHORT TERM...Marsili LONG TERM...Marsili AVIATION...Cobb Visit us at Follow us on Facebook...Twitter...and YouTube at: is the U.S. government's official web portal to all federal, state and local government web resources and services.