Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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747 FXUS63 KIND 101629 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 1229 PM EDT Mon Jun 10 2024 .KEY MESSAGES... - Unseasonably cool Today. - Warming trend beginning Wednesday, highs near 90 possible by Thursday and Friday. - Low chance of showers/t-storms Thu Night-Friday. && .FORECAST UPDATE... Issued at 923 AM EDT Mon Jun 10 2024 Large area of stratocu continues its southward push in advance of an wave aloft pivoting through the back side of the broad upper trough. 13Z temperatures were in the upper 50s and lower 60s. The overall forecast remains on track for the rest of the day. The wave aloft will track across the region through early to mid afternoon with the stratocu remaining in abundance before drier air enables skies to clear during the second half of the afternoon. The presence of the cloud coverage in tandem with steady N/NW winds will bring a cool feel to the air for much of the day. Much of the region will remain in the 60s as long as the clouds linger with potential for a late surge into the lower 70s with increasing sun late... especially over the southwest half of the forecast area. Zone and grid updates out. && .SHORT TERM (Today and tonight)... Issued at 303 AM EDT Mon Jun 10 2024 Today... Surface obs are indicating a backdoor cold front is moving into far southern parts of central Indiana as seen in a shift from southwest to northeast winds. Meanwhile, GOES-16 IR satellite loop and surface obs are showing extensive MVFR/VFR stratocu deck over southern Wisconsin, northern Illinois and lower Michigan. The deck was dropping southeast along an ahead of an upper trough that was rotating southeast across the Great Lakes per H20 vapor imagery loop. This trough will move southeast of the Ohio River this afternoon and with broad surface high pressure building in from the west and a high sun angle, look for the deck to scatter out from west to east. Despite some afternoon sunshine, cold advection behind the cold front will translate to below normal temperatures and the coolest day of the foreseeable future. Temperatures may not even hit 70s degrees over northern and eastern locales, where strato . cu remains the longest. Normal highs for this time of year are in the 80s. Finally, Hi-Res soundings suggest mixing down of near 20 knot gusts this afternoon from around 850 millibars. Tonight... Winds will drop off quickly after dark as diurnal mixing ceases and high pressure continues to build in as the pressure gradient relaxes. In addition, upper ridging will close in from the upper Midwest. Drying column per soundings along with light to calm winds will provide efficient radiation cooling and allow for unseasonable chilly overnight temperatures in the 40s. && .LONG TERM (Tuesday through Sunday)... Issued at 303 AM EDT Mon Jun 10 2024 A pattern shift towards warmer temperatures is becoming increasingly likely this week. Northwesterly flow aloft currently prevails and has been dictating our weather. As such, we`ve seen rather cool conditions for this time of the year. That changes as ridge-building occurs to our west. Ensemble guidance is in decently good agreement showing the resulting ridge gradually translating eastward by the weekend. At the surface, high pressure shifts southeast of Indiana by late Tuesday or early Wednesday. This allows flow to gain a southerly component and thus beginning the expected warming trend. Modest warm air advection brings high temps into the mid 80s for most locations Wednesday afternoon. As the aforementioned ridge edges eastward, temperatures near 90 are possible Thursday afternoon. However, we are still likely to be on the eastern side of the ridge at this point. Flow aloft still retains a northwesterly component to some extent. Guidance is keen on bringing a system in from the northwest along with its associated cold front. We may see a shower or thunderstorm from this feature late Thursday or into Friday. By the weekend, ensemble guidance depicts the ridge axis shifting eastward and directly over Indiana. NAEFS/ECMWF ensemble situational awareness tables give an early look at the potential strength of the ridge. Both tend to show 250mb heights within the 95th to 99th percentile range. Such anomalous ridging would lead to very warm surface temperatures, assuming clouds/precipitation does not impede warming potential. Readings into the 90s are possible again this weekend and into next week. Additionally, surface dew points are likely to increase with sustained southerly surface flow. Heat and humidity may lead to high heat indices late this weekend and early next week, and will need to be monitored closely. Taking a look beyond the long range into the 8-14 day period, we see a signal for sustained ridging within ensemble guidance. Continued above-average warmth and humidity is the most likely outcome in such a scenario. Precipitation anomalies are a bit harder to discern, however. Guidance is showing a plume of tropical moisture developing over Gulf late this week, which may lift northward into the ridge. This may lead to "air mass" type thunderstorms or may interact with decaying frontal boundaries drifting southward. Deterministic models show the polar jet well to our north once the ridge develops, so large-scale organized forcing may be absent most of the time. Therefore, our rainfall may depend on these subtle interactions that are harder to pin point this far out. && .AVIATION (18Z TAF Issuance)... Issued at 1229 PM EDT Mon Jun 10 2024 Impacts: - MVFR ceilings possible at times through mid afternoon - Occasional gusts to around 20kts this afternoon Discussion: A wave aloft on the back side of the parent upper trough over the northeast U S was tracking through the region early this afternoon. A large area of stratocu with ceilings generally between 2500-3500ft was progressing S/SE in tandem with the wave aloft and will remain across the forecast area over the next few hours. Scattering of the deck has already expanded into far northern Indiana as of 16Z and will move across the terminals from north to south during the second half of the afternoon. May see gusts briefly jump up as sunshine and low level mixing increases later this afternoon. Skies become clear this evening as a broad high pressure ridge and deep subsidence overspreads central Indiana from the north. Winds will become light and variable with the ridge across the Ohio Valley through Tuesday. && .IND WATCHES/WARNINGS/ADVISORIES...None. && $$ UPDATE...Ryan SHORT TERM...MK LONG TERM...Eckhoff AVIATION...Ryan