textproduct: Wilmington

WHAT HAS CHANGED

High Wind Warning issued for late tonight through the day on Friday for areas near and north of I-70. Wind Advisory remains in place for the rest of the local area on Friday.

KEY MESSAGES

1) Windy conditions will develop late tonight and continue through the day on Friday. The highest gusts will occur mid morning through mid afternoon, especially near/north of I-70, where gusts around 60 mph will be possible.

2) Breezy and warmer conditions will develop on Sunday ahead of an approaching cold front. Showers and a chance of thunderstorms can be expected Sunday night, potentially transitioning to a rain-snow mix in the early morning hours on Monday, with some snow showers lingering into Monday afternoon. 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) Windy conditions will develop late tonight and continue through the day on Friday. The highest gusts will occur mid morning through mid afternoon, especially near/north of I-70, where gusts around 60 mph will be possible.

A compact/deep low pressure system will translate to the SE from the Upper Midwest to the Great Lakes region late tonight through the day Friday. Latest guidance suggests a sub-990 mb sfc low migrating north of the OH Vly Friday morning into early afternoon, with a H9 LLJ on the order of ~50kts, with H8 LLJ on the order of ~60kts, translating E through the region between 12z-18z. An initial narrow wing of light RA/SN encountering an antecedent dry airmass may enhance early downward momentum transfer due to evaporational cooling for a brief period area-wide between about 11z-14z, especially as the core of the strongest LLJ translates through the ILN FA during this time. Thereafter, enhanced diurnally-driven mixing (along with steepening LL lapse rates owing to subtle CAA aloft) should develop by/past mid-morning, even with uncertainties regarding depth of mixing. Although the strongest LLJ will pull E of the local area past 18z, steep LL lapse rates should still support relatively good mixing through the afternoon. Confidence is increasing in a period of very strong winds, particularly from WC through central OH as well as EC IN, mid-morning through mid afternoon, with momentum transfer supporting the potential (~50%) for sporadic gusts of around 60 MPH in these areas. This, combined with recent saturated soils, will likely cause scattered tree and powerline damage in these locations.

With sufficient ensemble support and forecast sounding momentum transfer suggesting potential for 50+kt gusts from WC through central OH and parts of EC IN for at least several hours (especially 12z-18z), a High Wind Warning has been issued. There is a bit lower confidence further to the S across parts of the Tri-State into N/NE KY regarding the potential (and more specifically the longevity/persistence) for 50+kt gusts, so a high-end Wind Advisory has been maintained in these areas for now. If data trends toward stronger gust potential in these areas, an upgrade to a High Wind Warning may be considered.

Gusts will taper off toward sunset and beyond with the combined loss of diurnal mixing, continued decrease in the LLJ, and the relaxation of the sfc pressure gradient.

KEY MESSAGE 2) Breezy and warmer conditions will develop on Sunday ahead of an approaching cold front. Showers and a chance of thunderstorms can be expected Sunday night, potentially transitioning to a rain- snow mix in the early morning hours on Monday, with some snow showers lingering into Monday afternoon. A much colder airmass will settle into the area for Monday and Tuesday, with lows in the teens likely Monday night.

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 as a closed midlevel low develops, 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.

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 35kts Sunday afternoon, with the rain/storms/better moisture still well to the W. This mixing/gustiness will drop off temporarily toward/beyond sunset with the decrease in mixing, but should pick up again after midnight as the strongest LLJ noses into the region ahead of the advancing cold front.

At this time, 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 narrow 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 potential for embedded thunder, will quickly advance to the E into/through the local area between about 06z-12z Monday, with a small window for potential severe activity if the SB-instby is able to nose far enough E into the local area during the middle of the night. Current guidance suggests that the instby may pinch off just to the W of the local area as BL/sfc moisture 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 be maintained as the strong front approaches after midnight Sunday, there could end up being some brief severe potential locally. But those details are far from certain 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.

On the backside of the system, cold air will rush into the local area by daybreak Monday following the FROPA, with 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 SCT 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. Regardless of whether this SHSN activity remains more ISO or ends up being more widespread in nature, a rapid drop (potentially >30 degrees in ~6 hours) is expected near/just prior to daybreak Monday, leaving anomalously cold air in its wake for Monday and Tuesday. Lows on Monday night into Tuesday morning will likely dip into the teens area-wide, presenting a concern for sensitive vegetation which may be in the early stages of growing/blooming.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

Aside from a FEW VFR Cu this afternoon, mainly clear skies are expected through early evening before trending to SKC around sunset. Mid clouds will overspread from the W toward 06z and beyond, with 10-12kft CIGs expected by 09z.

The primary item of interest for the TAF period is going to be the gusty winds expected, particularly between 12z-22z on Friday. SW winds on the order of 20-30kts, with gusts between 45-50kts, can be expected, especially for nrn sites of KDAY/KCMH/KLCK. The strongest gusts are generally expected between about 14z-20z before slowly decreasing to 15-20kts by sunset. Of additional concern is going to be the SW LLWS on the order of 50-55kts between about 10z-13z area- wide.

Although some brief RA/SN cannot be completely ruled out between 10z-13z, kept the fcst dry for now given low probability of this reaching the ground. The best chance for a brief RA/SN mix is going to evolve from near KDAY to KCMH/KLCK during this time period. Otherwise, VFR conditions prevail with FEW VFR Cu by Friday afternoon.

OUTLOOK... MVFR to IFR conditions will be possible Sunday night and Monday, along with gusty winds in excess of 35 knots.

ILN WATCHES/WARNINGS/ADVISORIES

OH...High Wind Warning from 5 AM to 8 PM EDT Friday for OHZ026-034-035- 042>046-051>056-060>062. Wind Advisory from 7 AM to 8 PM EDT Friday for OHZ063>065-070>074- 077>082-088. KY...Wind Advisory from 7 AM to 8 PM EDT Friday for KYZ089>100. IN...High Wind Warning from 5 AM to 8 PM EDT Friday for INZ050-058-059. Wind Advisory from 7 AM to 8 PM EDT Friday for INZ066-073>075-080.