textproduct: Wilmington

WHAT HAS CHANGED

A Wind Advisory has been issued for the Tri-State through eastern Indiana and western and central Ohio for the potential for gusty winds Sunday and Sunday night.

KEY MESSAGES

1) Breezy and warmer conditions will develop on Sunday ahead of an approaching cold front. Showers and a chance of thunderstorms can be expected late Sunday night with a few strong to severe storms possible. Windy conditions are expected at times during this stretch.

2) A much colder airmass will settle into the area for Monday and Tuesday, with lows in the teens likely Monday night.

DISCUSSION

KEY MESSAGE 1) A rapidly deepening/digging midlevel trof will pivot from the central plains into the mid MS Rvr and OH Vlys late Sunday into early Monday morning. As this rapidly-deepening midlevel trof translates E into the region, it will progressively become more negatively-tilted and develop into a closed midlevel low, suggesting the evolution of a /very/ dynamic system, prompting the enhancement of LL and deep-layer wind fields Sunday into Sunday night across the local area. Intense mid/upper-level wind fields (H5 jet streak of ~125kts) will develop into the region Sunday night in response to the strengthening system.

During the daytime Sunday, the ILN FA becomes firmly positioned in the burgeoning warm sector, with deep/diurnally-driven mixing expected to lead to the potential of gusts in excess of 40kts Sunday afternoon, with the rain/storms/better moisture still well to the W. The best overlap of deep mixing and the stronger part of the LLJ (H8 ~60kts and H9 ~40kts) will likely evolve in parts of EC IN and WC OH, as well as areas near/west of I-71/I-75 into far northern KY. Although WAA patterns typically don/t result in the same gustiness that a CAA regime or tight pressure rise/fall couplet, deep enough mixing with the potent LLJ should allow for gusts near/in excess of 40kts for these areas during the afternoon into early evening. There is a signal for gusts around 45kts to briefly evolve from EC IN through WC OH during the heart of the afternoon where the stronger LLJ will be located during peak diurnal heating/mixing. This mixing/gustiness will drop off very briefly toward/beyond sunset with the decrease in mixing, but should pick up again around midnight as the strongest/most expansive LLJ noses into the region just ahead of the approaching front and shower/storm activity. There is a concerning signal for a brief 1-2 hour period of high-level advisory wind gusts immediately ahead of the front, particularly near/W of I-71. As such, a Wind Advisory has been issued for the N/NW/W 2/3 of the ILN FA to account for the gustiness from Sunday afternoon through the entirety of Sunday night.

Even 36 hours out, there is still quite a bit of uncertainty regarding maintenance of a narrowing axis of instby with eastward extent into late Sunday night/very early Monday morning. Certainly there is the potential that a thin corridor of SB-instby may develop into the local area past midnight as the forcing/lift increases rather dramatically/abruptly. A band of showers, with isolated potential for embedded thunder, will quickly advance to the E into/through the local area between about 03z-08z Monday, with a small window for potential severe activity if the SB-instby is able to nose far enough E into the local area due to robust sfc moisture advection. Current guidance suggests that the instby may be pinched off just to the W of the local area as BL/sfc moisture pool remains a bit more meager locally compared to upstream across IL/IN/MO/wrn KY. If, and it is a big if, sfc dewpoints in the mid/upper 50s are able to advect in just ahead of the narrow squall line as the strong front approaches around/after midnight Sunday, there would end up being some severe potential locally, with damaging winds being the primary threat. This will coincide with a H9 LLJ of about 50kts and a H8 LLJ of about 70kts surging in coincident with the narrow convective line, so any degree of momentum transfer would be cause for concern. If this occurs, it would be favored near/west of I-75, with even less potential for SB instby to develop further E of this area. But these details are still not yet in focus at this juncture, especially with the prospect of mixing out some of the BL moisture during the daytime Sunday well ahead of the better forcing/dynamics. The time/spatial window for sufficient/supportive moisture/BL thermodynamics (and severe threat) is relatively small, but potentially quite concerning if realized. This will certainly need to be watched considering the magnitude/depth of the very strong wind fields that will be in play. While damaging winds will be the primary threat, line-embedded tornadoes cannot be ruled out given the robust LL and deep-layer speed and directional shear and elongated/curved hodographs.

On the backside of the system, cold air will surge into the local area, potentially even leading to a mix of rain/snow or a brief period of snow on the backside of the band of showers during the predawn hours Monday. This could lead to light accumulations on grassy/elevated surfaces. Moreover, there is additional support for synoptically-driven gusts near/in excess of 35kts during the daytime Monday as LL lapse rates steepen and colder air aloft filters into the OH Vly. Coinciding with these windy conditions will be the potential for some SHSN as some moisture/lift may persist within the deepening/lowering DGZ into the daytime Monday. This will occur as an incredibly deep/potent PV anomaly digs into the region, providing plenty of forcing to maintain some SHSN activity into Monday afternoon. Whether this SHSN activity remains more ISO or ends up being more widespread in nature, a rapid drop (potentially 30 degrees in just 6 hours) is expected near/just prior to daybreak Monday, leaving anomalously cold air in its wake for Monday and Tuesday.

KEY MESSAGE 2) Strong CAA will likely result in a non-diurnal temp trace Monday, with slowly falling temperatures during the daytime, even after the rapid drop expected with the FROPA during the predawn hours. This CAA will persist into Monday night and early Tuesday morning, allowing for temps to dip into the teens area-wide by daybreak Tuesday. Highs on Tuesday may only reach into the upper 20s and lower 30s Tuesday before again dipping into the upper teens again Tuesday night into Wednesday morning. With the recent warm stretch, this magnitude and persistence of late-season cold may be problematic for sensitive vegetation, some of which may be in the early stages of blooming. Wednesday should reach into the mid 40s, but again this is the tail end of the forecast and the most likely to be adjusted as time moves forward.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

VFR conditions will prevail through the TAF period with mainly just some mid and high level clouds at times. Some VFR Cu is possible after 15z Sunday.

A strengthening SSW LLJ on the order of 45kts overnight will lead to some LLWS late tonight into Sunday morning. By 15z, deepening LL mixing and steepening LL lapse rates will allow for diurnally-driven momentum transfer to commence, resulting in an increase in wind speeds/gusts toward 18z and beyond. Southerly winds of 20-25kts, with gusts around 40-45kts, are likely toward/beyond the end of the TAF period into Sunday night.

OUTLOOK...Wind gusts at or above 35 knots likely during the daytime Monday. MVFR CIGs and VSBYs are likely late Sunday night into Monday morning with MVFR CIGs possibly lingering into Monday afternoon.

ILN WATCHES/WARNINGS/ADVISORIES

OH...Wind Advisory from 11 AM Sunday to 8 AM EDT Monday for OHZ026-034- 035-042>046-051>056-060>065-070>072-077>080. KY...Wind Advisory from 11 AM Sunday to 8 AM EDT Monday for KYZ089>099. IN...Wind Advisory from 11 AM Sunday to 8 AM EDT Monday for INZ050-058- 059-066-073>075-080.