180 FXUS63 KIND 011437 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 937 AM EST Mon Feb 1 2021 .UPDATE... The AVIATION Section has been updated below. && .SYNOPSIS... Issued at 224 AM EST Mon Feb 1 2021 Light snow showers will linger through today on the back side of this weekend's low pressure system. They will become more confined to the eastern portions of the forecast area by this afternoon though as high pressure strengthens to the west. This broad ridge of high pressure will then dominate the pattern through mid-week, resulting in dry but cold weather. After that, the pattern will become more active as a couple of systems bring chances for wintry precipitation to the region in the extended period. Further out, models continue to trend toward cold Arctic air next weekend, possibly the coldest of the season. && .NEAR TERM /Today/... Issued at 224 AM EST Mon Feb 1 2021 Current surface analysis indicates an area of low pressure centered over the Ohio Valley with another area of low pressure tracking up the East Coast. Meanwhile, GOES16 WV shows a large plume of moisture wrapping around these disturbances and extending back into central Indiana, which correlates well with the light snow reports in the latest obs across central Indiana. Time cross sections show a saturated air column through Mon 18Z, but at that point, there is a drastic drop in moisture with dry air overtaking the mid and upper levels. This is portrayed well in model trends as strong subsidence overtakes the region as high pressure strengths further over the Rockies. So, will lean toward a dry forecast over the western two-thirds of central Indiana by this afternoon with any lingering snow showers confined to the eastern counties during the evening hours. In addition, a tightening pressure gradient will keep winds breezy out of the north today with sustained speeds in the 10 to 15 mph range with gusts up to 25 mph. Daytime highs will top off below normal in the northerly flow with readings in the upper 20s (NE) to mid 30s (SW). && .SHORT TERM /Tonight through Wednesday Night/... Issued at 224 AM EST Mon Feb 1 2021 Strong subsidence throughout the short term period will keep conditions dry as a broad area of high pressure overtakes the central U.S. The ridge axis is progged to be over the Plains by tonight, shifting eastward throughout the short term period and eventually reaching the Great Lakes Region on Wednesday night. The strong northerly winds will persist into tonight with gusts up to 25 mph, but the gradient will begin to relax a bit by Tuesday. The northerly flow will help keep temperatures below normal though for most of the period with lows dipping into the teens and 20s tonight and Tuesday night, and daytime highs only topping off in the upper 20s to mid 30s on Tuesday. However, as the surface flow becomes southerly on Wednesday, a brief warming trend will commence. Daytime highs on Wednesday will top off in the low to upper 30s with slightly warmer temperatures in the low to upper 20s on Wednesday night. && .LONG TERM /Thursday through Monday/... Issued at 258 AM EST Mon Feb 1 2021 The long term will focus on two features, helping produce precipitation on Thursday and then sub-seasonal temperatures next weekend. A low pressure system will begin to develop in the lee of the Rockies Wednesday, moving eastward along a neutrally oriented upper level trough. Primary cyclogenesis will be within the left exit region of a 400-300mb upper level jet. The lack of significant advections and dynamic alignment should keep this system rather mundane. However, an influx of moisture out ahead of the trough will help invigorate precipitation development slightly, with overall QPF totals expected between 0.25"-0.5" over central Indiana. P-type should mostly be rain as central Indiana is located within the warm sector, although some mixed precipitation during onset is possible. Further into the period a majority of ensemble members are in decent agreement, especially for 150+ hours out, indicating strongly below seasonal temperatures next weekend. A positively tilted mid to upper level trough will reinforce the the southward progression of an arctic airmass into the eastern half of the CONUS. This is supported by a strongly negative AO depicting weak inertial stability of the polar jet. Given this combination of factors, confidence in a cold snap during days 6 through 7 is trending upwards. Current ensemble means are showing 1000-500mb thickness values below 4900 indicative of an extremely cold air mass. Although, exact temperature values are hard to predict and will vary as models ingest observations in the coming days. Overnight lows on Saturday night are expected to be in the single digits, but below zero values are not out of the realm of possibilities. && .AVIATION /Discussion for 011500Z TAF Update/... Issued at 937 AM EST Mon Feb 1 2021 Few breaks in the low deck have develop over the central part of the area and will drift across KBMG and KIND over the next few hours. Expect the MVFR ceilings though to fill back in and hold the rest of the day. 12Z discussion follows. IMPACTS: MVFR ceilings over southern TAF sites throughout the day and into tonight. Brief VFR at KLAF this morning, quickly deteriorating to MVFR by late morning. Scattered snow flurries through mid-afternoon. Gusts up to 25 knots throughout today. Improving conditions late tonight. DISCUSSION: Upper level low pressure will move off to the east throughout today. With it, BKN to OVC cloud cover is likely with ceilings between 1200 and 1800 feet. Scattered snow flurries are likely through 21Z. Visibilities could lower slightly within heavier flurries given gusty winds. Winds will remain strong throughout the day even past dusk; sustained around 12-15 knots with gusts upwards of 25 knots. After 06Z winds should start to die down. Clouds will begin to scatter later tonight as high pressure builds in. && .IND WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS...TDUD NEAR TERM...TDUD SHORT TERM...TDUD LONG TERM....Updike AVIATION...Updike/Ryan