723 FXUS63 KIND 290300 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 959 PM EST Sat Nov 28 2020 .UPDATE... The Near Term and AVIATION Sections have been updated below. && .SYNOPSIS... Issued at 232 PM EST Sat Nov 28 2020 High pressure will hold across the area through Sunday. A low pressure system is expected to affect the area from Sunday night into early next week. High pressure will return for the middle to later parts of next week. && .NEAR TERM /Rest of Tonight and Sunday/... Issued at 959 PM EST Sat Nov 28 2020 Clear skies are in place across central Indiana at 930 pm. Temperatures are in the mid to upper 30s with light southwesterly winds and dew points in the middle to upper 20s. Surface high pressure centered east of the area continues to block northward advancement of clouds and this will continue through most of the overnight. Could see an increase in clouds in the southwest by the morning sent in this direction by a system currently strengthening over western TX/OK. No appreciable changes in the forecast. Previous discussion follows... Model data suggest a gradually weakening surface ridge will hold across the local area through Sunday, as an amplifying northern stream trough digs into the northern Midwest by Sunday evening. A decent amount of lift may be generated across the area during the day Sunday, ahead of the approaching trough. However, models suggest condensation pressure deficits within the precipitation bearing layer will remain insufficient for precipitation through the day Sunday. As a result, only expecting a gradual increase in mid and high level cloud, starting by the pre dawn hours of tonight and continuing through Sunday. Low level thicknesses suggest the GFS MOS temperature guidance for tonight and Sunday look reasonable for the most part, so only minor adjustments planned. && .SHORT TERM /Sunday Night through Tuesday/... Issued at 232 PM EST Sat Nov 28 2020 Model data suggest the amplifying northern stream trough will evolve into a deep upper low over the area by Monday night, with this low drifting slowly east by Tuesday. In addition, a southern stream system will get absorbed by the developing upper low. Models suggest this southern stream system will shear out across the Ohio Valley Sunday night and Monday. It appears the deeper moisture will get tied up with the southern stream system, and get shunted off to the southeast of the local area. However, sustained lift associated with the developing upper low, will result in a gradual saturation of the air mass from the top down by the early morning hours of Monday. Will bring in PoPs starting Sunday night, and continue them into Monday night. Will start to taper off the PoPs from west to east later Monday night into Tuesday, as the upper low drifts off to the east. The highest PoPs appear to be from late Sunday night into Monday night, coinciding with the development and passage of the upper low. Thicknesses should be low enough under the developing upper low for most of precipitation to fall in the form of snow, except for the beginning of the event where thicknesses may still be high enough for the precipitation to start as rain. Most of the area has potential for light accumulations by Tuesday. Potential exists for somewhat higher amounts over the far east zones, where models suggest the western fringes of a deformation zone may intrude into the those areas for a time Monday afternoon and night. Progged low level thicknesses generally support the GFS MOS temperature guidance during the short term. Any adjustments should be minor. && .LONG TERM /Tuesday Night through Saturday/... Issued at 156 PM EST Sat Nov 28 2020 ECMWF shows high pressure building across the Ohio Valley on Tuesday night through Thursday in the wake of the departing low pressure system. Dry air and subsidence appear to be in place across Indiana on Tuesday through Thursday as ridging passed from the southeast. On Thursday through Saturday...the ECMWF continues with a highly amplified...wavy pattern aloft as another area of low pressure dives south to the southern plains before turning northeast for the Ohio Valley on Friday and Saturday. This will bring more chances for precipitation to Central Indiana late this week. At this time enough cold air appears in place that some of the precip type could be snow...although significant accumulations are not expected. Temps will be at or near normals. && .AVIATION /Discussion for 290300z TAF issuance/... Issued at 959 PM EST Sat Nov 28 2020 Updated current conditions only. Previous discussion follows... IMPACTS: -VFR thru the period. -Light (0 to 5 kt) southwesterly winds thru the night. DISCUSSION: Quiet weather is expected for the next 24 hours, with clear skies tonight and light southwesterly winds and high pressure sliding off to the east. CONFIDENCE: -High confidence in VFR through 0z Monday. -High confidence in light to calm winds overnight. OUTLOOK: A strengthening low pressure system will bring lowering ceilings, gusty northwesterly winds, and rain and snow to the TAF sites starting late Sunday night. && .IND WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...JAS NEAR TERM...JAS/CP SHORT TERM...JAS LONG TERM....Puma AVIATION...CP