Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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253 FXUS63 KIND 210144 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 944 PM EDT Sat Jul 20 2024 .KEY MESSAGES... - Dry through the day on Sunday - Chances for rain/t-storms and increasing clouds next week will likely help keep temperatures slightly below to near normal && .FORECAST UPDATE... Issued at 944 PM EDT Sat Jul 20 2024 Forecast is in excellent shape this evening. Made very minor adjustments in some variables based on latest hourly guidance trends, but this in no way changes the gist of the forecast - surface high pressure keeping a seasonably mild and dry airmass in place at the surface, coupled with an increase in mid and high cloud ahead of an upper level trough currently centered over Iowa, which should prevent any significant fog in what would otherwise be a decent radiational cooling/radiation fog setup. Cannot rule out patchy fog near daybreak in the typical low lying, rural, and valley areas, but this will be of little consequence. && .SHORT TERM (This evening through Sunday)... Issued at 237 PM EDT Sat Jul 20 2024 Rest of This Afternoon... Scattered to broken coverage of cumulus will continue along with some high clouds, resulting in partly cloudy skies for much of the area. Temperatures will peak in the 80s. Tonight... A weak upper wave will drift toward the area, but at the surface, lingering high pressure will remain in control. Mid level moisture will increase with southerly flow there. The resulting mid level cloud deck will result in mostly cloudy skies. Some weak isentropic lift may sneak into the far southern forecast area late tonight, and this may result in a sprinkle given the dry low levels. Not confident enough though to introduce any sprinkles at this time. Clouds will help keep temperatures a little warmer than previous nights. Lows will be in the 60s. Sunday... The mid and high clouds will stick around well into Sunday, and some cumulus may pop up. Skies will overall be partly to mostly cloudy. Some weak lift will continue south of the forecast area. With the lift staying south of the area, will go with a dry forecast. However, if the lift were to get a little farther north, a light shower or sprinkle would be possible in the far southern forecast area. High temperatures will be in the 80s. && .LONG TERM (Sunday night through Saturday)... Issued at 237 PM EDT Sat Jul 20 2024 Upper Levels: Ensemble guidance continues to show a tight height spread in regards to the stagnation of a deep upper level ridge over the western CONUS this weekend through most of next week. This will further reinforce general troughing over the Mississippi and Ohio Vallies, with some amplified troughing possible as the quasi-stationary Bermuda high builds westward towards the end of the extended forecast period. There has been a trend towards a weak wave passing through the Ohio Valley late Tuesday into Wednesday Low Levels and Surface: Currently, surface ridging remains over the Great Lakes region, thanks to efficient CAA earlier this week. This high pressure will slowly erode, with troughing aloft. Upper level diffluence will prevail early next week, with most of the Ohio Valley out of the influence of low level high pressure by late Monday. Greater southerly flow ahead of a surface wave next weekend could allow for a warmer airmass shift towards the end of the long term. Temperatures: Upper level troughing above strong low level high pressure will help continue the sub-seasonal temperatures for portions of this weekend, but temperatures will approach seasonal by tomorrow as deep PBLs will aid in mixing and greater surface warming. Monday onward, surface high pressure will become weaker, but increased cloud cover and moisture will inhibit diurnal temperature gains, with highs remaining in the mid 80s. Greater southerly flow next weekend should give a subtle boost to temperatures, but uncertainty still remain on the more mesoscale related influence. Still, the overall pattern next weekend supports highs likely reaching the upper 80s. As mentioned, surface moisture will increase rapidly late Sunday through Tuesday as the surface ridge breaks down, and a weak mid to upper wave develops over the Ohio Valley. Current expectations are for surface dew points to push into the 70s once again by mid week, returning the summer-time feel to the air. Surface winds will remain very light through the extended period due to the lack of any significant low level disturbance. Precipitation: Upper level diffluence within a destabilizing atmosphere beginning on Monday will lead to an increases in diurnal thunderstorm chances throughout next week. Lapse rates are consistently greater than 6 C/km throughout he troposphere next week, further aiding in deep convective instability. The combination of deep instability and deep moisture will allow for very efficient rainfall rates within any thunderstorms. With storm motion expected to be very slow (Weak steering flow), pockets of 1-2" over short periods are possible. Outside of this, the flooding threat looks low outside of a low potential for mesoscale boundaries to help organize initiation. Without much shear, thunderstorms will have a difficult time organizing next week, limiting the overall severe threat. Still, given 3-4k CAPE and a high EL, updraft may be rather strong even in these brief windows of growth. This could lead to isolated hail and wind threats next week. There is some uncertainty on the amount of available mid level shear Late Tuesday and Wednesday, of which could increase the severe threat slightly during this 36 hour stretch. && .AVIATION (00Z TAF Issuance)... Issued at 700 PM EDT Sat Jul 20 2024 Impacts - No impacts expected Discussion: VFR through the period. Mainly mid and high cloud associated with an upper level trough are expected throughout the period as a dry low level airmass associated with surface high pressure remains in place across the area. Winds will generally be northerly through northeasterly below 10KT, occasionally light and variable to calm overnight. No significant obstructions to visibility are expected. && .IND WATCHES/WARNINGS/ADVISORIES...None. && $$ UPDATE...Nield SHORT TERM...50 LONG TERM...Updike AVIATION...Nield