Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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526 FXUS63 KIND 181900 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 300 PM EDT Sat May 18 2024 .KEY MESSAGES... - Fog possible again tonight; locally dense - Isolated showers across northern Indiana Sunday afternoon - Unseasonably warm Sunday-Tuesday with highs in 80s...ahead of increasing strong t-storm threat late Tuesday and Wednesday && .SHORT TERM (This evening through Sunday)... Issued at 258 PM EDT Sat May 18 2024 Isolated convection is possible through early evening, but there are several limiting factors for more sustained/deeper convection. Coverage is likely to be ~5% or less. Limiting factors include subsident capping layer around 3-4-km, dry entrainment, weak winds resulting in vertical updrafts that are short-lived. Any brief convective showers that do form would be most likely north of a band of wake subsidence across roughly the northern third of Indiana, and would diminish shortly after sunset. Deeper mixing today will redistribute some dry air making low level moisture slightly less than the last two days. But, the air mass largely hasn`t changed otherwise with little/no horizontal advection. Still, with clear conditions and an MSLP pattern that will favor light/calm winds, fog is once again expected. Dense fog is possible. There may be a slight preference for denser fog in areas of east- central and southeast Indiana where mixing was delayed given the magnitude of this morning`s fog. Ridging will build Sunday bringing a warmer pattern (temperatures at or just above the warmest temperature so far this season; mid-80s for maximums area wide). A northern stream wave will nudge a weak front to near the northern portion of our area and convergence along it may result in isolated showers and thunderstorms Sunday afternoon/evening. Coverage should be limited. Weak flow under the ridge will support unorganized short-lived single cells. && .LONG TERM (Sunday night through Saturday)... Issued at 258 PM EDT Sat May 18 2024 Sunday night through Monday... Upper ridging and surface high pressure will provide quiet weather conditions early in the extended. Expect increasing heights aloft and S/SW low level flow to help warm temperatures well into the 80s Monday. Thankfully relative humidity will remain low with dewpoints generally in the low 60s so it won`t feel unbearable. Monday night onward... Guidance is in general agreement that the upper level pattern will switch to more full-latitude troughing across the western CONUS compared to split flow this past week. This should result in a more active pattern with multiple embedded shortwaves potentially tracking over the Midwest next week. Look for rain chances to begin increasing Monday evening and remaining elevated through the long term. The best chance for rain looks be late Tuesday through Wednesday when an upper trough moves through. Severe weather is possible late Tuesday into Tuesday night and again on Wednesday, but uncertainties remain in the forecast. Models have been consistent showing a deepening surface low moving towards northern portions of the Great Lakes late Tuesday. The current expectation is for an MCS to develop near Iowa/Missouri along an attendant cold front before propagating eastward. The environment should gradually become less favorable as the MCS moves out well ahead of the front which should lead to gradual weakening with time. If the complex of storms can survive, there would be the potential for mainly damaging wind gusts Tuesday night. Other convective hazards such as large hail or tornadoes cannot be completely ruled out. Another round of severe weather is possible Wednesday, but uncertainties remain for this forecast as well. Latest guidance shows variance in where exactly the aforementioned cold front will be located. This will be the main factor for severe weather potential as daytime heating/moisture advection ahead of the front combined with sufficient deep-layer shear should support the potential for organized convection. Most guidance shows at least portions of the area remaining ahead of the cold front during the day Wednesday which suggest there is at least low end potential for severe weather. Mostly quiet weather conditions should return late Wednesday into Thursday once the cold front moves out, but rain chances quickly return towards the end of the week as another system could move in. && .AVIATION (18Z TAF Issuance)... Issued at 139 PM EDT Sat May 18 2024 Impacts: - Fog once again tonight; lowest visibilities near/south of I-70 Discussion: Clear conditions, light winds, and residual low level moisture will result in areas of fog again tonight. Uncertainty on spatial coverage and magnitude of visibility reduction exists since mixing and redistribution of drier air aloft today may limit fog to a slight degree. Best chance of dense fog will be at KBMG but especially further east. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...BRB LONG TERM...Melo AVIATION...BRB