Marine Weather and Tide Forecast for La Porte, IN

DISCUSSION
Issued at 241 PM EDT Sat Apr 19 2025

A sprauling trough across the western US becomes cutoff across the southwestern US as the northern stream continues eastward. This allows a baroclinic zone to set up from TX to arcing towards the Lower Great Lakes region. What's left of that energy in the southwestern US moves up towards the Lower Great Lakes Sunday evening. So, as the cold front that caused this morning showers and storms slowly shifts southeastward, rain shuts off for all areas by after midnight tonight. This brief reprieve in the rain is caused by surface high pressure nudging into the area. It attempts to shut rain off as mid 30s to mid 40s dew point air nudges in from the north. Better moisture exists south of US-30, so am not as sold on rain as far north as the GFS and ECMWF have. FWIW, the NAM doesn't have rain in the area at all Sunday. This thinking would keep the forecast in line with the previous shift of having mostly slight chance PoPs and a pocket of chance PoPs west of IN-15 at times and other times south of US-30. A warm front attempts to lift northward Sunday evening and may provide a time period with some thunderstorms as the NAM indicates some variation of 250 to 1250 J/kg of CAPE coupled with 30 to 40 kts of effective shear may be around. All of that appears marginally severe, though. The timeframe with the best moisture appears to be late Sunday night into early Monday morning as an occluded front swings west to east through the area, but dry air is quick to fill back in in the mid levels shutting off heavier rain to either drizzle or off altogether. Rain should be done Monday afternoon as sfc high pressure noses in from the south and heights become looser across the area. Expect gusty winds (25 to 35 mph)
Monday afternoon as a cold front pushes through and CAA takes over.

The aforementioned sfc high pressure area is west of the area later day Tuesday and this allows WAA to take over Tuesday night into Wednesday morning. Warmer high temps with 70 degree highs may be more prevalent Wednesday through the end of the week as a result.
One dampener on that warm of high temps would be that there's some model consensus around bringing some convection eastward through Lower MI on a stationary front similar to an MCS type evolution on the eastern edge of LLJ. Although the resultant location (and if it even happens) could change in the days to come.

Medium range guidance diverges Wednesday night through the end of the work week as the GFS is already bringing in the next trough and allowing for rain Wednesday night with some thunder possible. The ECMWF does have some connection to the Gulf during this time and it would only require some forcing to get showers and maybe some storms started. With the northern stream jet north of the area and the subtropical jet weakening, more defined areas of forcing will be harder for models to find and track between Thursday and Friday allowing quite a bit more uncertainty. Will keep slight to chance PoPs during the end of next week to indicate the possibility of rain and thunder, but nailing down a day and time comes with uncertainty at this time.

Look for drying some time next weekend as high pressure comes in and cooler/drier air arrives from the north.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
Issued at 1218 PM EDT Sat Apr 19 2025

Current MVFR conditions within cool, moist post frontal airmass will improve to VFR this evening as flow veers erly and subsident drying takes place.

IWX WATCHES/WARNINGS/ADVISORIES
IN...None.
OH...None.
MI...None.
MARINE...None.