textproduct: Wilmington

WHAT HAS CHANGED

Parts of the Wind Advisory have been upgraded to a High Wind Warning, mainly near/west of the I-71 and I-75 corridors. Additionally, the Wind Advisory was expanded to include the entire area to account for the potential for gusty winds late tonight with the cold front passage.

KEY MESSAGES

1) Windy and unseasonably warm conditions will continue ahead of an approaching cold front. Showers, with a chance of thunderstorms, can be expected tonight, potentially transitioning to a brief rain-snow mix in the early morning hours Monday.

2) Scattered snow showers are expected on Monday, potentially lingering into the evening. Although roads are expected to be mainly wet during the daytime, some isolated slick spots may develop after sunset with falling air and ground temperatures.

3) 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 today into early Monday morning. As this rapidly-amplifying midlevel trof translates E into the region, it will progressively become more negatively- tilted and develop into a closed midlevel low, indicative of a /very/ dynamic system, prompting the enhancement of LL and deep- layer wind fields beginning this morning and persisting into tonight. Intense mid/upper-level wind fields (H5 jet streak of ~125kts) will develop into the region tonight in response to the strengthening system, resulting in a strongly-forced band of precipitation along the leading edge of the sfc front where LL convergence will be maximized.

The ILN FA is becoming firmly positioned in the burgeoning warm sector, with deep/diurnally-driven mixing developing, leading to southerly wind gusts of 45-50kts, with the rain/storms/better moisture still well to the W. The best overlap of deep afternoon mixing and the stronger part of the LLJ (H8 ~60kts and H9 ~45kts) is evolving in parts of EC IN and WC OH, as well as areas near/west of I-71. 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 very strong LLJ is allowing for sporadic gust potential near/in excess of 50kts for these areas through early evening. This gustiness will drop off very briefly toward/beyond sunset with the decrease in mixing, but should pick up again around midnight as the strongest LLJ noses into the region just ahead of the approaching front and shower/storm activity. Given the latest guidance, the Wind Advisory was also expanded to include the entire ILN FA, due to expectations for 40+kt wind potential with the FROPA.

The evolution of tonight's system is coming into better focus, with quite a few solutions still showing a narrowing axis of instby with eastward extent into late tonight/very early Monday morning, particularly E of I-75. This being said, despite a nearly parallel LL bulk shear vector to the front itself, there remains the potential that, strictly due to the extreme convergence along the front within the strongly-forced and intensely-sheared environment, that severe (>50kts) winds will still make their way to the sfc in sporadic fashion as the convergent line moves W to E quickly through the ILN FA between about 03z-08z. A band of SHRA, with ISO potential for embedded TS, will provide small (~1-2 hour) windows for any one location to receive gusts near/greater than 50kts. But the coverage/expanse of this severe wind potential still remains in question due to a somewhat unfavorable BL thermodynamic setup, particularly for the ern half of the ILN FA.

Current guidance continues to suggest that the 0-3km instby may be pinched 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 advect in just ahead of the narrow squall line, there would end up being some more widespread severe potential locally, with damaging winds being the primary threat. This will coincide with a H9 LLJ of about 50-55kts and a H8 LLJ of about 70kts surging in coincident with the narrow convective line. If more a more widespread severe wind event is to unfold, it would be favored near/W of I-75, with even less potential for SB instby to develop further east of this area. Still yet, confidence in this occurring is still quite low, especially with the prospect of mixing out some of the BL moisture during the daytime today well ahead of the better forcing/dynamics. The time/spatial window for sufficient moisture/BL thermodynamics (and severe wind threat) is quite small for any one location, but potentially quite concerning. This will certainly need to be watched considering the magnitude/depth of the very strong wind fields that will be in play. Regardless, past 08z, the severe threat should be over for the entire ILN FA.

On the backside of the system, cold air will surge into the local area, with a ~30 degree drop in less than 6 hours expected for most spots. This quick arrival of colder air may even lead to a mix of rain/snow or a brief period of snow on the backside of the band of showers during the predawn hours. This could lead to isolated light accumulations on grassy/elevated surfaces, but roads will remain wet due to antecedent warm ground temps. 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. The strongest gusts near 40kts should be confined to areas near/N of I-70.

KEY MESSAGE 2)

Coinciding with the breezy conditions through the day Monday will be the potential for some SHSN as sufficient moisture/lift persists within the deepening/lowering DGZ through the daytime Monday. This will occur as an incredibly deep/potent PV anomaly digs into the region, providing plenty of forcing (and even some instby) for some SHSN activity through the daytime Monday. Some snow squalls will be possible, but thankfully ground temperatures and the relatively-high March sun angle should limit accumulation potential (and impacts) through the daytime, even as air temps slowly dip below freezing by late afternoon (ground/road temps will lag by at least several hours).

Of concern, however, is the potential that SHSN activity lingers past sunset. This loss of solar insolation amid air temps falling into the 20s, may create isolated slick spots/snow accumulation on untreated surfaces. It seems likely that at least ISO activity will persist past sunset given the maintenance of sufficient lift amidst a saturated DGZ , meaning that wet roads may turn somewhat slick in an isolated capacity coincident with the steadiest SHSN activity. Although overall accumulations will remain minor, the prospect of SHSN with subfreezing air and ground temps will be watched closely for impacts to roads.

KEY MESSAGE 3)

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.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

VFR conditions will persist through 06z, with the main item of interest through early evening being the S winds of 20-25kts, with gusts of 40-45kts. The wind will briefly taper off around 00z for a few hours before increasing once again out of the SSE around 03z-04z. SSE winds of 20-30kts, with gusts of 40-45kts are expected once again immediately ahead of a quickly-moving front and line of SHRA with ISO embedded TS. This squall line will approach KCVG/KLUK by 05z, KDAY/KILN by 06z, and KCMH/KLCK by 07z, with SHRA persisting for about 2-hours in any one location. Abrupt/significant changes in wind speed/direction are likely with the passage of the squall line.

Drier conditions will briefly return area-wide between about 08z-12z before scattered SHSN pivot into the region during the daytime Monday. This SHSN activity may result in brief MVFR/IFR VSBYs, but spotty coverage and uncertainty regarding timing/location precluded inclusion in the TAFs at this time.

The other item of concern after 00z is going to be S LLWS on the order of 50-55kts, which will end with the FROPA by 08z area-wide.

VFR CIGs will transition to MVFR with the arrival of the squall line, persisting following the FROPA through the remainder of the period area-wide. Brief MVFR/IFR VSBY is expected with the thin squall line. MVFR CIGs should still linger into Monday night. WSW winds of 20-25kts, with gusts around 35kts, are expected Monday mid morning through the afternoon, especially for nrn sites of KDAY/KILN/KCMH/KLCK.

OUTLOOK...MVFR CIGs are possible into early Tuesday. Some light snow, with MVFR CIGs/VSBY, is possible early Wednesday.

ILN WATCHES/WARNINGS/ADVISORIES

OH...High Wind Warning until 8 AM EDT Monday for OHZ026-034-035-042>045- 051>054-060>063-070>072-077-078. Wind Advisory until 8 AM EDT Monday for OHZ046-055-056-064-065-079- 080. Wind Advisory from midnight tonight to 8 AM EDT Monday for OHZ073- 074-081-082-088. KY...High Wind Warning until 8 AM EDT Monday for KYZ089>096. Wind Advisory until 8 AM EDT Monday for KYZ097>099. Wind Advisory from midnight tonight to 8 AM EDT Monday for KYZ100. IN...High Wind Warning until 8 AM EDT Monday for INZ050-058-059-066- 073>075-080.