Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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222 FXUS63 KIND 020907 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 507 AM EDT Tue Jul 2 2024 .KEY MESSAGES... - Warmer today - Thunderstorm chances Wednesday through Friday - A few severe storms with damaging wind possible Wednesday - Cooler and drier this coming weekend && .SHORT TERM (Today and tonight)... Issued at 228 AM EDT Tue Jul 2 2024 We will be on the windward side of prograding and gradually dampening mid-upper ridge today. This is often the warm side as lower tropospheric warm plume advects in from the southwest. There is some spread in model guidance for temperatures this afternoon which appears to be related to mixing characteristics and interaction of the surface-based mixed layer with the warm plume aloft. A non-GFS blend weighted toward ECMWF and MOS camps are warmer and seem more realistic in this environment. This will place the entire area in the mid to upper 80s. It also appears the warm plume will be quite dry, and capable of dew points on the lower end of the model spectrum. This is a typical bias in these situations of shallow moisture return and mixing into a pronounced warm/dry layer. Although fuels are green and insufficient wind thresholds indicate fire spread isn`t a concern, we did make this adjustment to more accurately convey afternoon humidity within our standard fire weather products. Lower tropospheric moisture advection will increase considerably tonight as lower latitude reservoir of moisture reaches Indiana coincident with subsiding mixing. Within a fairly stout warm advection regime, blended model guidance shouldn`t need much adjustment. The only potential caveat would be a slightly steeper drop immediately after peak mixing as a dry environment has stronger radiative cooling. But, this would level off quickly as low-level warm/moist advection regime strengthens overnight. Modeled IVT shows richer moisture through a deep layer relegated to a fairly narrow warm conveyer belt near and ahead of the cold front. It appears most mid-upper cloudiness will hold northwest of our area until tonight, and frontal convective band may approach in the pre- dawn hours. Substantial weakening and remnant light precipitation with extensive midlevel clouds is the most likely outcome for central Indiana very late Tuesday night. && .LONG TERM (Wednesday through Monday)... Issued at 228 AM EDT Tue Jul 2 2024 On Wednesday, the trough/ridge pattern should support a slow-moving weakly baroclinic cold front positioned over central Indiana. Anomalous rich moisture through a deep layer coupled with surface heating should result in moderate instability. Westerly wind aloft is modest but should result in 20-30-knots supporting organized multicell clusters. This is a good setup for sporadic wind damage potential with the most intense convective cells. The limiting factors for a more organized and/or greater magnitude severe episode will be (1) absence of dry midlevel layer somewhat limiting intense cold pool formation, and (2) marginal deep layer shear. Nevertheless, one or more bowing segments with swaths of wind damage could still form. The threat appears greatest across roughly the southern half of Indiana given modeled frontal timing relative to diurnal destabilization. There is some uncertainty on Thursday (July 4th) with regards to convective coverage and timing. There has been a subtle trend toward weaker low-latitude mean ridging (to our south) and a more amplified upstream trough (to our northwest). Thus, midlevel heights are lower across Indiana compared to previous model cycles. The diminishing warm conveyor belt and deep subtropical moisture plume will probably be to our south, and our air mass may be overturned from the previous day`s convection. It appears that replenishment of moisture and noteworthy destabilization may not occur until later in the day when modest low level jet expands across Indiana. This would potentially result in some warm advection-driven convection later in the evening and overnight. Also, there is some signal for an upstream synoptically-driven convective complex. Mid-upper flow is quite weak to sustain this into Indiana late Thursday night or early Friday, however. Rather, there may be a tendency for this to upshear propagate into the mid-Mississippi Valley. Later in the day on Friday, timing of frontal forcing with diurnal destabilization may result in the best convective coverage south and east of our area. The post-frontal air mass next weekend should be cooler and less humid, albeit not as pleasant as this last cool/dry air mass that`s currently departing. Modest moistening and destabilization early next week preceding the next shortwave trough will result in increased rain chances. Timing and intensity remain uncertain given increasing ensemble spread by this time. && .AVIATION (12Z TAF Issuance)... Issued at 507 AM EDT Tue Jul 2 2024 Impacts: -None Discussion: VFR conditions will continue. Some high cirrus clouds may be observed, especially toward the end of the TAF period. A shift in MSLP pattern will result in winds veering slightly during the early morning, as mixing commences. Easterly or east-southeasterly winds will become more southeasterly. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...BRB LONG TERM...BRB AVIATION...BRB