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Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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522 FXUS63 KIND 050528 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 128 AM EDT Fri Jul 5 2024 .KEY MESSAGES... - Drier overnight tonight with patchy fog - Rain and storms arrive near sunrise with scattered showers and storms through late afternoon - Dry conditions, less humid this weekend...Monday-Thursday expected to exhibit seasonable warmth/humidity with a few rain opportunities && .FORECAST UPDATE... After the abundance of clouds throughout much of the day...the widespread rain and storms earlier followed by the scattered showers this evening...skies have cleared out nicely just in time for evening outdoor activities. 0130Z temperatures ranged from the upper 60s to mid 70s with a humid airmass remaining. Much of the night will be dry as weak ridging aloft follows the convection from earlier this evening. With winds likely going near calm late tonight and shallow moisture in the near surface layer... expect patchy fog formation overnight with the potential for lower stratus to expand into the region from the east as well prior to daybreak. Uncertainty remains with respect to the ongoing convection from southwest Missouri back into Oklahoma. The convection will expand northeast into the lower Ohio Valley towards daybreak in a weakened state but as to how expansive it is for the forecast area is uncertain. Do not anticipate a repeat of this morning with the widespread rain and storms but there will be at least some convection moving into the Wabash Valley around sunrise or shortly after. Lows tonight will largely be in the upper 60s and lower 70s. Zone and grid updates out. && .SHORT TERM (This evening through Friday)... Issued at 300 PM EDT Thu Jul 4 2024 Latest satellite and radar imagery show convection associated with this morning`s complex of showers and storms pushing off to the east with widespread cloud cover in its wake. Weak low pressure noted on surface observations continues to push eastward into Central Illinois and will work its way into North Central Indiana by this evening. Surface to 850mb thermal gradient exists just south of this low from around Kansas City through Southern Ohio acting as a quasi- warm frontal feature. However the low level environment on either side of the front is very warm and moist. ACARS soundings from IND and STL indicate stability along and north of this boundary with a developing "warm nose" around 850mb, keeping the lowest 1 km agl stable with a marginally unstable and drier environment above it. This warm nose will likely inhibit substantial convective development across Central and Northern Indiana over the next few hours. Thicker cloud cover along and north of the I-70 corridor may also further enhance the S-N thermal gradient across the area through the evening hours. Satellite imagery clearly indicates stability for the northern half of Indiana with a healthy cu field developing in Southern Illinois and Indiana as the environment destabilizes. KSDF ACARS soundings paints a very different picture of the environment along and south of the aforementioned boundary with little indication of an inversion and steep low level lapse rates with CAPE approaching 2500-3000 j/kg. This strong thermal and instability gradient across South Central and Southern Indiana may be the area to watch for convective development going into the evening hours. Southeast flow at the surface with westerly flow aloft, 40-60 kt bulk shear, 30-50kt 0-3km shear, and 100-200 m2/a2 effective helicity may be sufficient for organized convection to develop this evening with damaging winds, isolated tornadoes, and flash flooding as main threats. Confidence is low as guidance typically does not handle situations well that highly depend on micro to mesoscale features. Best threat for these storms looks to be along and south of the I-70 corridor; however if areas further north can destabilize over the next few hours, cannot rule out a stronger storm there as well. Central and North Central Indiana will likely remain on the stable side of the boundary, with isolated, non- severe convection possible, but not likely through this evening. Tonight... After dusk, any remaining isolated showers and thunderstorm across Central Indiana should begin to wain as the atmosphere further stabilizes. This should keep conditions fairly dry through the early overnight hours. Guidance does show additional convection developing along the boundary south of the region; however most of that precipitation will likely also remain along and south of the Ohio River. Central Indiana remains in a weird location, north of the main boundary, but ahead of an approaching low and secondary front to the north and west. Lower confidence exists in the northward extent of convection by the early morning hours tomorrow. Lately guidance has been way overdoing overnight convection and brining it in too fast. So will go with consistency and keep the overnight hours drier. Although with such a saturated airmass and a low level inversion keeping moisture trapped at the surface, would not be surprised to see patch fog again tonight and towards sunrise tomorrow. Added patchy fog across the whole region to account for this chance with the Wabash Valley and lower lying areas and valleys having the best chance for fog development. .Tomorrow... There could be some showers and maybe a thunderstorm ahead of the approaching low and associated "cold" front tomorrow morning. HREF members and RAP guidance shows isolated showers and storms at best during the mid to late morning hours with more widespread convection developing east of the region later in the day. Expect a drying trend through the afternoon hours across Central Indiana with peaks of sun likely and temperatures rising into the low to mid 80s. && .LONG TERM (Friday night through Thursday)... Issued at 300 PM EDT Thu Jul 4 2024 Friday Night through Sunday... Broad yet weak surface high pressure will cross from the central Plains to the Mid-Atlantic this weekend ahead of a slowly- approaching, pronounced mid-level long wave trough over much of the central CONUS. Dry conditions will therefore return to central Indiana as precipitable water values aloft drop by almost two-thirds below today`s near-record levels. West-northwesterly light to moderate breezes Saturday will bring the coolest day of the next week, when widespread upper 70s are expected north of the I-74 corridor, perhaps at the cost of some lingering morning cloudiness. Low to mid-60s minimums will be the rule for both Friday and Saturday nights amid noticeably lower dewpoints. Expect more typical July conditions for Sunday as modest southerly flow returns mid- to upper 80s and seasonably moderate humidity. Monday through Thursday... The next work week should return a touch more warmth and humidity to continue the overall seasonable conditions from Sunday. The central US upper trough will continue to approach during the early week while weakening and probably focusing more of a weak SW flow into Indiana. THis combination of WAA ahead of lower heights should make for a very warm day Monday ahead of milder readings through the mid- week. Probably a few to at times scattered showers around the realm during Monday-Tuesday while the trough is approaching, especially Tuesday if a southern vort could phase into the trough axis while crossing the Midwest. Rainfall amounts would likely be lighter and not contribute to further drought improvement for most locations, but isolated t-storms/downpours would be possible. A trend to mainly dry conditions for the Wednesday-Thursday timeframe assuming the trough pulls across the Midwest on schedule, with isolated afternoon showers possible. Since Indianapolis` last 90F+ on June 22, IND has only reported one day above 87F (88F, July 3)...and the highest temp currently forecasted for the next 7 days is 88F on Monday, 7/8. && .AVIATION (06Z TAF Issuance)... Issued at 127 AM EDT Fri Jul 5 2024 Impacts: - Mainly VFR conditions this TAF period. - Brief MVFR possible 11Z-16Z with possible showers and very isolated storms. Discussion: Mostly clear skies, light winds and dew point depressions less than 2F have lead to MVFR to IFR fog development. This will persist through the early morning hours. A thunderstorm complex over SE MO is expected to push northeast into the Ohio Valley. It is expected to diminish somewhat upon approach, however the HRRR does continue to suggest this decaying system to pass across southern parts of central Indiana, possibly impacting the TAF sites. However, confidence remains too low at this time for a specific prevailing mention. Have used VCSH for the moment. After this morning round of possible showers passes, forecast soundings show a dry column with afternoon CU development as convective temperatures are reached. A mid level inversion will prevent deep convective growth. This should mainly be VFR CIGS. High pressure over the plains states will build across Indiana tonight and VFR conditions will continue under mostly clear skies and light winds. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Ryan SHORT TERM...CM LONG TERM...AGM AVIATION...Puma