Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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424 FXUS63 KIWX 190753 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 353 AM EDT Thu Sep 19 2024 .KEY MESSAGES... - Remaining unseasonably warm (upper-80s) through at least Saturday. - Much needed rain enters the forecast as early as Friday for some (20-30% chance). - Not as warm next week with highs in the mid-70s. && .DISCUSSION... Issued at 343 AM EDT Thu Sep 19 2024 The primary forecast challenge is anticipating when the first raindrops will actually fall as this stagnant weather pattern comes to an end in the coming days. But first, dry once again today with any fog mixing out as the morning progresses. Fog is once again aided by a marine layer pushing in from Lake Erie. High cirrus this morning has had little impact on fog thus far, as fog continues to spread west through northwest Ohio. High pressure will remain in place over the eastern Great Lakes while a cold front, currently over central Nebraska, approaches the Mississippi River through the day. High resolution guidance is raising some concern for isolated severe storms Friday afternoon, which is somewhat curious but also within the realm of possibility. The parent low occludes over the Canadian Prairie which results in sheared-out forcing aloft locally by Friday. Moisture return is weak and generally shallow on Friday due to a strong ridge over Mexico extending through Oklahoma, along with high pressure to our east steering Atlantic moisture south of the Ohio River valley. Despite this, dew points in the low-60s are noted early this morning over far western Iowa and are forecast to advect east to our area by Friday. Forecast soundings otherwise depict adequate but not- uniform moisture through the column. No wonder, then, that box and whisker plots depict paltry rain amounts (if any) in Michiana Friday afternoon. With these miss-matched ingredients, I am skeptical of the high resolution guidance which might be over- convecting (perhaps due to erroneously high dew points impacting CAPE). Even with a modest adjustments to dew points closer to 60, low- level lapse rates would be adequate (7c/km) as would shear (30 knots). This is overall something to keep an eye on and I`ve increased POPs toward 30% as a result. Remaining warm both Friday and Saturday as 500-mb heights remain elevated along with continued balmy 850-mb temperatures. This ridge breaks down and our persistent eastern Great Lakes high gets kicked east as a trough over the Four Corners and trough over Manitoba buckles the jet stream. The result is some much needed rain in the Sunday through Tuesday time frame. Beyond this, scissors were deployed for POPs Wednesday and Thursday behind a departing low. Tried for a dry forecast Thursday, but some guidance and neighbors preferred the slight chance showers (15% chance). && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 1148 PM EDT Wed Sep 18 2024 The set up tonight is similar to last night with the potential for dense fog formation late tonight as lower 60 dew points were over northeast Indiana with slightly higher moisture amounts upstream in the synoptic east flow from the Atlantic with some enhancement (extra moisture) from Lake Erie. The hourly HRRR lagged some with the fog development last night, but appears to be on track in at least the right area with rapid dense fog development over northwest Ohio spreading into northeast Indiana including the FWA terminal. The 24 hour temp/dew pt changes showed the FWA spread 5 degrees smaller this past hour then last night at this time. Also, dense fog had already formed in the marine moisture rich air at the Toledo Suburban Airport (KDUH). Updated the FWA TAF with categorical dense fog before daybreak. The fog will mix out mid to late morning rendering light east winds.. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...None. && $$ DISCUSSION...Brown AVIATION...Skipper