Sunrise 6:40 AM   Sunset 8:44 PM Moonrise 4:13 AM   Moonset 5:06 PM

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FXUS63 KIND 051629 AFDIND

Area Forecast Discussion National Weather Service Indianapolis IN 1229 PM EDT Sun May 5 2024

KEY MESSAGES

- Confidence continues to increase for severe weather potential both Tuesday and Wednesday. All hazards are possible, with damaging wind and large hail as the primary threat.

- Heavy rain threat Monday through Wednesday. Flooding possible due to multiple rounds of convection.

FORECAST UPDATE
Issued at 925 AM EDT Sun May 5 2024

Lower stratus has expanded across much of the forecast area this morning with broad cyclonic flow in place behind the front that passed through overnight. 13Z temperatures ranged from the upper 50s to the mid 60s with a steady N/NW wind.

The forecast is in very good shape for the rest of the day with the primary focus for the update on the clouds and how quickly they mix out. The current ACARS sounding for KIND shows moisture trapped beneath an inversion between 900 and 850mb. As progressively drier aloft associated with high pressure expands east into the region over the next few hours...this will likely strengthen the inversion for a short period of time before boundary layer mixing can overcome it. Expect the lower stratus to linger in abundance as a result for the next few hours with a trend towards increasing sunshine as the clouds mix out into a cu field this afternoon.

Remain confident in a dry forecast for the entire area through late day as the subsidence associated with the high pressure ridge should aid in the deeper moisture remaining closer to the Ohio River and points south. Northerly winds near 10mph are expected throughout the day. Low level thermals support highs mainly in the low to mid 70s for much of the forecast area .

Zone and grid updates out.

.SHORT TERM (Today and tonight)...
Issued at 258 AM EDT Sun May 5 2024

Low cloud cover has begun to spread across central Indiana early this morning mainly associated the remnants of a decaying MCS. Within these low clouds, isolated weak showers are possible, but most areas are expected to remain dry.

Behind this MCS, a NW shift in winds and modest AVA upstream of a low level trough will be enough for low level height rises across the region. This should eventually create enough subsidence and mixing to erode the low level cloud cover. By the late morning, pockets of sunshine are expected, slowly becoming partly cloudy by the afternoon. The overall airmass is drier and cooler for Sunday, leading to a slight dip in temperatures; back into the mid to upper 70s for highs.

During the day on Sunday, another shortwave is expected to develop over the mid-Mississippi Valley, centered within the diffluent region of the subtropical jet. This should push E/N into the Ohio Valley late today. Confidence is increasing the the aforementioned low level high will enough to suppress wave progression enough for central Indiana to remain dry through the daytime hours and through dusk. The greater source of lift within the wave looks tonight, with showers quickly developing over KY/IN border around midnight. Dry surface air will initially curtail precipitation onset, but continued lift and saturation should be enough for scattered showers prior to sunrise on Monday.

.LONG TERM (Monday through Saturday)...
Issued at 258 AM EDT Sun May 5 2024

The main forecast concern in the extended is the potential for severe weather Tuesday and Wednesday. However, rain chances persist through most of the period due to the broad troughing aloft over the eastern CONUS. Anomalous moisture combined with the potential for multiple rounds of convection could also lead to heavy rainfall.

Monday through Wednesday night...

Showers and some thunderstorms will likely be ongoing at the beginning of the period as a shortwave trough moves through the region. Limited instability and deep-layer shear should inhibit any severe weather potential for Monday. Multiple embedded shortwaves within broad upper troughing are then expected to traverse the region Tuesday/Wednesday. Models still show some discrepancies regarding timing or location of any developing surface lows, but generally have become better aligned.

The first potential round of severe weather looks to arrive sometime Tuesday afternoon into the evening as a surface wave approaches.
Expect showers and storms to be ongoing early in the day within a warm air advection regime. Cannot rule out severe potential in the morning though the greatest threat should be later in the day as increasing low-level theta-e advection leads to stronger destabilization. In addition, guidance shows a mid-upper level jet moving in during the latter half of the day. Moderate to strong instability combined with increasing deep-layer shear supports the potential for organized convection. All hazards could be on the table for Tuesday though damaging winds and large hail appear to be the greatest threat at this time.

Another round of severe weather is possible on Wednesday as a second surface low moves towards the region. CSU machine learning and CIPS analogs are more bullish with this setup, but uncertainties remain in the forecast. An important factor to the severe weather threat on Wednesday will depend on where the warm front associated with the surface low sets up. Generally models show the frontal boundary set up near central Indiana allowing for a moderate-strong unstable airmass to develop late in the day for at least portions of the area.

Subtle ridging may limit convective potential through portions of the day, but increasing coverage of storms is expected late in the day as large scale ascent and warm moist advection increases.
Strong deep-layer shear combined with the favorable unstable airmass will likely support organized convection posing a threat for all hazards. If the warm front sets up further south then the attendant severe threat would shift further south due to less destabilization so trends in the location of the low will have to be monitored closely in the coming days. Prior day convection also limits confidence some as this could impact the favorable parameter space.
Heavy rainfall is a concern both Tuesday and Wednesday given the potential for multiple rounds of convection. Wednesday may have the greatest threat though with the aforementioned warm front potentially setting up west to east over central Indiana. This could lead to training convection.

Thursday onward...

Rain chances persist through the long term period as broad troughing remains aloft and broad cyclonic flow on the backside of the departing low. Cold air advection within northwest flow will lead to a cooler pattern heading into late week. By this point, it appears the severe threat should shift out of the region.

.AVIATION (18Z TAF Issuance)...
Issued at 1229 PM EDT Sun May 5 2024

Impacts:

- VFR conditions developing this afternoon through much of tonight

- Restrictions developing near daybreak Monday with scattered showers

Discussion:

Lower stratus has been steadily mixing out over the last hour or two as drier air and subsidence work down into the boundary layer. This trend will continue with a VFR cu field for the rest of the afternoon along with expanding high clouds from the southwest in advance of low pressure set to track into Arkansas this evening.
Clouds will thicken and lower tonight and early Monday as the low lifts into the lower Ohio Valley. Light rain showers will increase in coverage near or just after daybreak Monday...with MVFR ceilings developing. Brief periods of IFR ceilings will be possible late morning Monday into the afternoon.

Light N/NW winds are expected into the evening...veering to E/NE by daybreak then E/SE on Monday.

IND WATCHES/WARNINGS/ADVISORIES
None.

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