Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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333 FXUS63 KIWX 162345 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 745 PM EDT Thu May 16 2024 .KEY MESSAGES... - Scattered showers and storms with local downpours this afternoon into Saturday. - Very warm Sunday into Tuesday with highs in the low to mid 80s. - Strong storms possible Tuesday. && .UPDATE... Issued at 744 PM EDT Thu May 16 2024 An area of mainly light showers continues, with a few of the showers managing to tap the limited instability, but poorly sheared environment long enough to intensify with pockets of locally heavy rain and in a few instances 30 to 35 mph gusts. Loss of heating should allow for a slow reduction in coverage. Small area of showers in east central IL will work ENE and may impact far S/SE areas in a few hours. CAMs still try to expand coverage with this area and increasing LLJ of 30 kts later tonight. Have toned down pops in the SE overnight to no more than likely. If these can come together the weak flow and abundant moisture could lead to some areas of heavier rainfall and ponding. && .DISCUSSION... Issued at 257 PM EDT Thu May 16 2024 An area of surface convergence was setting off showers and sub- severe thunderstorms in Missouri this morning. That area of surface convergence located behind a warm front today sets the stage for a resurgence of moisture and, therefore, showers and thunderstorms later this afternoon into tonight. As the parent low pressure system moves northeast into southern Canada, a cold front slowly approaches the area around midday Friday and pushes through during the afternoon. This likely takes Lake MI-adjacent counties out of any pop-shower or storm that forms during the afternoon with the 500 to 1500 J/kg of MUCAPE at their disposal. These storms will be lacking in the shear department and that limits their severity, but locally heavy down pours will be possible. This is most likely true tonight as a moist environment with 60F surface dew points, 850 mb dew points approaching 10C, and 1.3 in PWATs in addition to weak winds, favorable MBE vectors, and hints at available large scale ascent. By Saturday, the better moisture has shifted south and east some so that the area conducive to pop showers and thunderstorms will likely be lesser during the afternoon, but not zero. Storms will, once again, have 500 to 1500 J/kg of MUCAPE to work with, but shear will, once again, be negligible limiting the severity of these storms. DCAPE does appear to approach 900 J/kg so perhaps a microburst could occur in addition to locally heavy rain. Surface high pressure and mid level ridging overhead work in tandem to keep Sunday dry. It`ll be a nice day with highs securely in the 80s. With forcing still off to our northwest, daytime Monday also looks dry, but with a few more clouds around. Highs will also be securely in the 80s. From Monday night through Wednesday morning, an active period with some extent of forcing nearby is in store. An upper low over southwest Canada will serve as the main channel through which areas of vorticity will be flung towards the area. The first such one scrapes our northwest Monday night and there will likely be thunderstorms with this, but shear appears limited also limiting severe weather potential. Another shortwave appears to encroach on our western areas Tuesday morning before a cold front approaches the area Tuesday evening and night. This begs the question how much instability and shear will be present during this time debris clouds around and the timing of the front may limit instability as well. One positive for storms may be that mid level lapse rates around or potentially surpassing 7 C/km could be around for storms to tap into. These are generally favorable for severe hail. However, with the rain chances around during this time, it`ll be interesting to see how those lapse rates maintain themselves or mix out before they make it here. Flooding could be a problem with the continued rain chances, especially in urban areas, which are normally more flood prone. Finally, the arrival of these pieces still has time to change between now and then so it`s certainly not yet set in stone. Tuesday`s active weather has been slowing down some in recent model runs so while I have some confidence in Thursday being dry, I have less confidence in keeping Wednesday dry, especially the morning. Have lowered NBM PoPs Wed PM, but only to low chance at this juncture. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 744 PM EDT Thu May 16 2024 Area of showers and isolated storms has shifted east of KSBN with a period of partial clearing coming for at least a few hours before stratus begins to develop and settle in with MVFR cigs overnight into the first part of Friday. Light rain/rain showers will persist at KFWA for a few hours with the initial area weakening. A small area of showers/storms extended from KDNV to south of KCMI, moving ENE over the next several hours. Models try to expand this area somewhat, possibly clipping the airport later this evening, but think bulk of this will remain to the S and E. Have left a unrestricted shower mention in the next several hours. Cigs should also begin to lower overnight, although maybe not quite as low as KSBN since the site will be well east of the weak sfc trough edging eastward. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...None. && $$ UPDATE...Fisher DISCUSSION...Roller AVIATION...Fisher