Sunrise 6:27 AM   Sunset 8:30 PM Moonrise 3:08 AM   Moonset 2:21 PM

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FXUS61 KILN 030539 AFDILN

AREA FORECAST DISCUSSION National Weather Service Wilmington OH 139 AM EDT Fri May 3 2024

SYNOPSIS
The unseasonably warm pattern will persist across the region for the foreseeable future, with periodic episodes of rain and storms nearly every day through the end of next week. Although not all spots will receive rain each day, there likely will be at least a few showers or storms around fairly frequently, with the most unsettled stretch likely to evolve near the middle of next week.

NEAR TERM /UNTIL 6 AM THIS MORNING/
Showers in the northern ILN CWA have mostly dissipated this evening, though an isolated shower or two will remain possible for the next few hours. A greater chance for precipitation will begin to move into the area after 08Z, as 925mb-850mb theta-e advection continues, and a weak shortwave (more evident on models at 700mb than 500mb) moves into the area. Have slightly sped up the eastward progression of PoPs during the early morning hours, but otherwise the going forecast appears reasonable.

Previous discussion > Some diurnally-driven Cu have sprouted about the area, coincident with an axis of slightly better LL moisture availability (shown via sfc DPs in the upper 50s and lower 60s).
This axis of slightly higher LL moisture is advecting back to the N, with some mixing out of sfc DPs on the southern flank (near the OH Rvr) as we progress into late afternoon. By early this evening, the highest DPs (upper 50s) may be close to I-70 and near/W of I-75, suggesting a relatively small temporal and spatial window for a spotty SHRA or TSRA or two to develop in EC IN and WC OH this evening. Even with this being said, the overall potential for spotty activity is somewhat low, with the best coverage centered in the 22z-02z time frame near a corridor from Fayette/Union Cos IN to Shelby/Auglaize Cos OH. Gusty winds in a favorable DCAPE environment will be the primary threat with any stronger cores, but there are notable uncertainties regarding both the coverage and intensity of storms that develop (if any at all). Do think that the potential for gusty/damaging winds with storms is low enough to continue a null HWO for now.

The main item of interest for the remainder of the daytime will be the unseasonably warm temps in the mid to even upper 80s.
This, combined with sfc DPs ranging from the mid 50s to around 60 degrees will certainly lend itself to a "summerlike" feel about the area this afternoon/evening. Although these values are not "hot" by traditional summertime standards, the occurrence of these temps/humidity this early in the season is fairly anomalous for the area. For example, if the high at KCVG or KDAY reaches the fcst of 86F, it would be the first time reaching such a temp this early in the season (on/prior to May 2) at each respective site since 2012.

The diurnally-driven Cu should wane in coverage toward/beyond sunset, lingering the longest in WC OH where those spotty SHRA/TSRA (if there are any at all) could percolate a bit into the late evening hours. Lows tonight dip into the lower/mid 60s area-wide amidst calm/light winds and thickening mid/upper level cloud cover late in the night.

SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/
The short term period will be somewhat unsettled, although not particularly concerning from a hazardous-weather perspective. A midlevel S/W will eject NE through the TN/OH Vlys through the morning, with a very diffuse LL flow pattern in its wake stretching SW to NE squarely through the region. While there will be some very subtle LL convergence near the LL trof axis, a remnant weak low/MCV will likely provide a focus for the most persistent coverage/development of activity as we progress into the afternoon/evening. A few SHRA will move into the far wrn parts of the ILN FA shortly after daybreak before /slowly/ expanding E into the rest of the area through the course of the daytime. Recent guidance has trended slightly slower with the progression of this feature into the local area, so have adjusted PoPs accordingly.

By the afternoon into the evening, there should be an expansion in coverage of SHRA/TSRA activity locally, albeit in a very disorganized manner. SCT to numerous SHRA, with some ISO embedded TSRA, will be the primary item of interest mid afternoon through the evening hours along/immediately ahead of the weakly-convergent LL flow axis and MCV remnant, which should migrate into N KY by Friday evening. The weak convergence associated with these two separate, but related, features amidst an amply-saturated (high PWAT) environment will keep SHRA/iso TSRA activity going for a fairly extended stretch from late Friday morning through late Friday night. However, activity should decrease from W to E past midnight into Saturday morning, with at least a few SHRA likely still lingering in central OH to NE KY by daybreak Saturday.

The overall potential for TSRA vs. SHRA on Friday is fairly low considering the somewhat meager instby in the profile. In fact, the weak steering-layer flow likely points to brief heavy rain as being the only /low-end/ concern, and even this looks too negligible to even add to the HWO at this juncture.

Highs on Friday will be very-much convectively-modulated, with temps reaching into the lower 80s from NE KY through central OH before the better SHRA/iso TSRA activity moves in later in the day. Elsewhere, highs should top out in the mid 70s, although certainly temps may only top out around 70 in EC/SE IN where thicker cloud cover/more persistent pcpn coverage will evolve earlier in the day than will be the case for points further E.
Lows Friday night dip into lower 60s amidst extensive LL cloud cover (a soupy setup).

LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/
An unsettled
warm
somewhat humid...and potentially active period for early May is in the offing during this period. There may be hazards including severe storms and locally heavy rain/flooding given the large scale / synoptic setup at some point during the middle of next week, but timing/area is highly uncertain.

At 12Z Saturday, a closed mid/upper level low pressure over Hudson Bay will be meandering slowly east across southeast Canada through/atop ridging to its east into Sunday. Some weakness in the height field /weak 700mb trough/ across the Ohio Valley and embedded/strung out vorticity - almost somewhat removed from stronger flow to the north - will plod along slowly through the weekend and keep things unsettled Saturday, while a secondary weak wave ripples through the Great Lakes on Sunday maintaining some degree of rain chance. Rain chances Saturday should remain highest east of I-75 along a diffuse surface trough moving ever so slowly east underneath the strung out vorticity aloft and mid-level troughing
On Sunday
while the weak 700mb trough will have exited to the east, more energy moving through the Great Lakes and also through KY/TN Sunday night will maintain rain chances. Just an unsettled...non-washout-but-still-showery weekend with highs in the 70s.

On Monday...the residual impacts of the southern stream wave moving through KY/TN will likely foster diurnal shower/storms especially south, before that system pushes east as well.

A progressive...deep upper trough will be pushing steadily east across the western CONUS on Monday, forcing replacement height rises over the Ohio Valley in the wake of weekend unsettled weather. This system will slow and continue to deepen as it centers over the Dakotas by Tuesday, which places the Ohio Valley in broadly diffluent/southwesterly flow aloft with a wide open Gulf of Mexico- sourced low level jet transporting plenty of warmth/moisture for the middle of next week. While the magnitude of the negative height anomalies trends downward through the week, the trough axis remains intact and maintains a feed of moderate/fast southwesterly flow atop a southerly low level jet well into Thursday. As a result of all of this, ejecting waves out of the trough should focus/funnel through the Ohio Valley along an oscillating frontal boundary draped somewhere nearby. These waves are common in all deterministic/ensemble member runs, but with widely varying latitude and depth.

It is noted that CIPS analogs running on the mean GEFS pattern highlights a broad area of potentially daily severe convective threat from the central and lower Mississippi River Valley, into the Ohio Valley Tue-Thur that is mirrored by 02.00Z CSU MLP guidance.
GEFS/EPS instability matrices are strongly aligned in this time period offering moderate instability, and plenty of precip chances via waves moving through the area. 02.00Z EPS Ef/SOT graphics paint a corridor of anomalous CAPE/shear overlap for early May through the Ohio Valley, peaking on Wednesday, but timing should taken cautiously at this time range as daily threats will be modulated heavily by low amplitude shortwave tracks and convective overturning in previous days. The pattern - when taken cumulatively - suggest rainfall/flooding issues could be present either with individual MCS episodes, or from repeated rounds of convection as the ridge slowly flattens and low-mid level flow begins to align in a WSW orientation by the end of next week, when an effective frontal should begin to settle south of the area and we cool/dry out perhaps into next weekend.
But until then...Tues night-Thursday bears some potential for several rounds of organized storms, some of which could be strong to severe, with locally heavy rain/flooding.

AVIATION /06Z FRIDAY THROUGH TUESDAY/
Mid level energy will lift northeast across the region today into tonight. This will lead to periods of rain showers and perhaps a few embedded thunderstorms. While most of the day will not be a wash out, skittered showers will be possible at times through much of the TAF period. Will generally handle this with a VCSH. CAMs are suggesting the best chance for more widespread pcpn will be during the mid afternoon hours and will try to hit a period around that time with a prevailing -shra. Cigs will gradually trend downward today with some MVFR cigs possible this afternoon.

OUTLOOK...Thunderstorms possible at times Saturday through Tuesday. MVFR ceilings are likely Friday night into Saturday, with IFR ceilings and MVFR VSBYs possible Friday night into Saturday morning. MVFR conditions are possible again Sunday morning.

ILN WATCHES/WARNINGS/ADVISORIES
OH...None.
KY...None.
IN...None.

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