Sunrise 6:20 AM   Sunset 9:17 PM Moonrise 2:49 AM   Moonset 6:43 PM

  Print   HELP   Reset   Save   Recall  News

FXUS63 KIND 030616 AFDIND

Area Forecast Discussion National Weather Service Indianapolis IN 216 AM EDT Wed Jul 3 2024

KEY MESSAGES

- Hot and humid Today; Highs near 90 with dew points in the low 70s

- Rain and thunderstorm chances Wednesday through Friday, A few strong to severe storms are possible on Wednesday and Thursday.

- Uncertainty increases for timing of thunderstorms on Thursday and Friday

.SHORT TERM (Today and tonight)...
Issued at 216 AM EDT Wed Jul 3 2024

Tuesday Night into Wednesday Morning...

Radar and satillite imagery showcase a healthy MCS currently over Missouri, that should progress into western IL over the next few hours. As this MCS moves eastward it will encounter abnormally dry airmass, seen through KIND ACARS soundings with 10-15 degree dewpoint depressions through the entire 0-10km column. This dry layer will errode some as the MCS pushes eastward, but all that should be left as this system reaches central Indiana is a broken to overcast 3-6km cloud deck. For now isolated shower chances have been kept over far NW and W central Indiana, given some uncertaity on the swiftness of MCS decay. Outside of this area, temperatures should remain fairly mild as the PBL struggles to decouple completely underneath increasing upper level clouds and a steady W/SW low level flow. Current low temperature forecast is between the upper 60s and low 70s across central Indiana.

Wednesday and Wednesday Night...

The 0-3km layer should quickly moisten post dawn as the high breaks down beneath upper level diffluence, resulting in an increase of S/SW winds. By 14Z, most areas south of I-70 should have dew points arleady in the upper 60s to low 70s. The remants of the previous mentioned MCS is expected to leave a weak stationary boundary over central Indiana, of which will be the primary focus for convective intiation in the afternoon.

Temperature wise, central Indiana will be split in two, with areas north of I-70 likely remaining in the mid to upper 80s benath steady cloud cover and weaker surface flow. Futher to the south, sun light should trickly in by mid to late morning, aiding in temperature gains. Most areas south of I-70 should reach or exceed 90, with some locations approaching 92/93 in far southern Indiana. A few CAMs have a well mixed boundary layer this afternoon, but given consistant flow through the lower 1km, this solution looks unlikely. The current expectation is for a closer to climatelogical moisture to temperature vertical distribution, with dew points remaining in the low 70s this afternoon over southern Indiana. The combination of temperautres in the low 90s and dew points in the low 70s will push heat index values near to just above 100. An SPS has been issued to highlight the heat risk for this afternoon.

As mentioned, the stationary boundary will be the focus for convective development later this afternoon over central Indiana.
Current HRRR members are varied on where this boundary will be positioned, but given the pattern and consistent surface flow, the current forecast leans towards further north solutions, keeping the I-70 corridor in >40 PoPs this afternoon. Eventually, the CAPE gradient will push south, increasing convective coverage this evening over southern Indiana.

In regards to thunderstorm severity, bulk sheer values are generally not very supportive of sustained, and organized updrafts, but the thermodynamic profile does hint at an increased damaging wind threat this afternoon and evening; 00Z HRRR suite shows a broad area of 50- 100 J/kg 0-3km CAPE and DCAPE values 1000-1200 J/kg. Small hail cannot be ruled out, but a large hail threat looks highly limited given elevated freezing levels and modest updraft strength. This overall threat will be for all areas south of the aforemtioned boundary, but far southern central Indiana has the greatest risk given higher thunderstorm coverage expected this evening.

Around dusk, evapoative cooling and a lack of consistent moisture return. should rapidly increases local surface based CIN and limit convective development. A few isolated thunderstorms can not be ruled out for tonight, but most areas should remain dry. A secondary low from the SW will begin to develop late Wednesday into Wednesday night, helping re-establish a moist warm sector over southern portions of the region. This should not lead to any rainfall pre- dawn, but dew points and temperauters should remain elevated. Expect overnight lows to range from the mid 70s over far SW central Indiana (Knox Cty), to upper 60s over NW central Indiana (Tippecanoe Cty).

.LONG TERM (Thursday through Tuesday)...
Issued at 216 AM EDT Wed Jul 3 2024

The forecast for Thursday (July 4th) and Friday continues to be complicated with below average confidence. Mesoscale details are unclear due to convection in a weakly forced unstable regime. How the convection evolves tomorrow evening will have some implications on potential Thursday, and likewise the potential for Friday will be dependent on convection Thursday. We'll explain these details and list some possible scenarios in the analysis below. Bottom line, we will continue to encourage lightning safety messaging, as well as the dangers of thunderstorm-driven wind gusts, as these will both be the primary hazards through Friday. We encourage our media partners and emergency managers to do the same, given the juxtaposition of numerous outdoor events with these potential thunderstorm hazards.

On the synoptic scale, mid-upper level ridging will continue to weaken as one shortwave trough departs. This will result in falling midlevel heights over our region and a southward shift of a weakly baroclinic front. Some models are more nondescript with the MSLP pattern than others, and show the front will be masked by residual convective cold pools. It appears as though convection may continue into Thursday morning mainly to our south along the northern periphery of a modest low level jet and associated weak low-level moisture advection. There may be a tendency for convective elements to propagate upshear and thus move further south. How much this convection augments mesoscale features is unclear at this time. It does not appear there will be a noticeable push of continental air into our area, so even north of the front once diurnal heating commences isolated to scattered convection may reform anywhere across central Indiana, since this pattern doesn't support meaningful capping.

One caveat to the above is the potential for a MCS or remnant MCS that may initiate from where the warm advection signal is strongest, over Missouri. This could be fostered by increasing large-scale ascent from approaching deepening shortwave trough over the northern Plains. Rich moisture and at least modest instability will support convective regeneration, and although the lower tropospheric flow is quite weak, westerlies aloft are strong enough to contribute to 30- 40-knots of effective shear. In this scenario, a fairly slow-moving weakly organized MCS or cluster of convection may enter western- central Indiana during the morning or midday (uncertain timing), resulting in more widespread rain coverage. A tendency for at least some element of upshear propagation given the modeled kinematic fields may favor stronger convective elements to our south and perhaps some limit on how far north central Indiana will be impacted. With the most intense convective cells, damaging wind gusts is the primary threat, given the moisture distribution, instability, and shear values expected.

The best chance of a dry period Thursday would be post-MCS (if one moves through), where overturning and mesoscale subsidence temporarily limits convective development. As closed midlevel low approaches late Thursday evening and night, lower tropospheric flow should strengthen and replenish moisture perhaps driving either (1)
some warm advection convection, or (2) maintaining another upstream MCS. It appears by midday or afternoon Friday, the cold front will be east and diurnal convection that develops along it would be mostly in Ohio, but perhaps in our far east.

Obviously with all the caveats of convective timing, the temperature forecast has a fairly high degree of uncertainty Thursday and into Friday. Post-frontal air mass will be cooler and drier this weekend, but probably not to the magnitude seen with the most recent continental air mass. Nevertheless, this should lead to a dry period with the next opportunity for rain being Monday and Tuesday.
Probabilities during this period are low/mid-range and spread across a broad period for now, due to increasing ensemble spread and uncertainties about how this front will/won't potentially interact with deeper subtropical moisture surge.

.AVIATION (06Z TAF Issuance)...
Issued at 1242 AM EDT Wed Jul 3 2024

Impacts:

-Potential for MVFR to IFR vsbys/cigs due to TS at IND and BMG mid to late afternoon.
-Southwesterly wind gusts to 22kts 15Z to 01Z.

Discussion:

VFR conditions expected through much of the TAF period outside of a low potential for MVFR vsbys at LAF and HUF towards daybreak and a period mid to late afternoon as thunderstorms move through.
Confidence is higher in the second round of convection with IND and BMG likely to see MVFR to briefly IFR vsbys during convection. Winds will gradually become more southwesterly towards the morning hours with gusts to 22kts from 15Z to 01Z before becoming near calm during the overnight.



IND WATCHES/WARNINGS/ADVISORIES
None.

Full Color Weather Map

Link to Loop


Other links: GEOS-West     Contential US     Full GOES-East

Indianapolis, IN,