095 FXUS63 KIND 260727 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 327 AM EDT Mon Apr 26 2021 .Short Term...(Today through Tuesday) Issued at 327 AM EDT Mon Apr 26 2021 Early this morning, some mid clouds were across the northern forecast area, with some cirrus approaching the remainder of the area from the west. Temperatures were in the upper 30s to upper 40s. Upper ridging will build across central Indiana during the day today. Strong warm advection through the low to mid atmosphere will continue through the day today. This will result in some passing mid and high clouds at times, but the overall day will be partly to mostly sunny. After a cool start, the warm advection and sunshine will boost temperatures into the 70s this afternoon. A low level jet will move in today, aiding in the warm advection. Mixing should be high enough to bring down gusts up to 35 mph. The low level jet will continue into this evening, but the boundary layer will decouple, keeping winds in check. With the upper ridge in place, expect dry conditions with some passing high clouds. Temperatures will be much warmer than recent nights, with lows in the 50s. The upper ridge will move a little farther east on Tuesday. Weak energy riding around the ridge will bring passing mid and high clouds. Warm advection will continue. With the warmer start and continued warm advection, highs will be in the 80s. Less than a week after setting a record low at Indianapolis, temperatures will be within a few degrees of the record high, 84 degrees (last reached in 1990). Tuesday will be breezy once again, with gusts around 35 mph possible. && .Long Term...(Tuesday night through Sunday) Issued at 327 AM EDT Mon Apr 26 2021 The long term period will begin as the overall amplified mid-level regime transitions from ridge to trough. Although there is moderate confidence that the stagnant progress of the trough's southern, cut-off energy along the US-Mexico border will also slow the eastward advance of the mid-latitude wave from the northern Plains to the Mid-West...promoting at least a 36-hour period of unsettled/rainy weather over Indiana in the early Wednesday-Thursday timeframe. The period will start amid near-record warmth courtesy the persistent southwesterly flow between the ridge over the the southeastern US and the approaching deep trough to our west. While not as warm as Tuesday, very mild, and even somewhat humid conditions, will persist through midweek as the system's elongated cold front should also be slow to reach/cross the CWA. The heaviest rainfall should be focused along this boundary, and perhaps enhanced by surface cyclogenesis. There is low confidence in appreciable instability Wednesday, between the nearly-moist adiabatic temperature profile and resultant considerable cloudiness limiting surface heating. However, the H850's southwesterly flow is still expected to be in the 20-40 kt range for most of this unsettled period, while coupled with a precipitable water maximum axis over the CWA of about 1.00-1.75" ...which are near-record values for late April. Therefore did not hesitate to have POPs peak 75-90% in the middle of this period. Have set QPF values across the CWA, through only Thursday, to a generous 1.00-1.50", although assume this is reasonable given the consistently anomalous P-Wat guidance. Greater chances for thunderstorms would generally be Wednesday-Wed Night with decent theta-E ahead of the slow front...although kept slight chances through end of day Thursday given low confidence on how fast the system will pass from west to east. Timing of frontal passage and strength of mid-level frontogenesis with any developing surface low, that would cross the region while sliding northeastward up the front, will be important variables to the timing/duration of periods of moderate-heavy rain. A strong upper ridge over the western US will build into southwest Canada by late week, which may also trigger some energy...from a northern stream trough over central Canada...to descend into the Mid-West system, which would help to prolong showers in the Thursday-Thursday night timeframe. The broad western upper ridge will then advance eastward into the central US during Friday-Sunday, which should push its corresponding surface high pressure into the Mid-West, making for a generally dry weekend. Cooler/less-humid air will build into the CWA from the northwest, although if any of the interior-Canada upper trough first plunges into the US...as the mid-week, mid-latitude trough finally departs...it would make for a chillier Friday-Saturday. The period will end with the upper ridge likely flattening as it reaches the region, favoring a return to slightly above normal readings. Some guidance members suggest a rather weak system crossing the southern Great Lakes around Sunday, but decided on no more than thunder-less slight chance POPs at this time as solid majority of ensemble members keep central Indiana dry. For the entire period, temperatures will be near normal Thursday-Saturday, and otherwise above normal. && .Aviation...(260600Z TAF Issuance) Issued at 1144 PM EDT Sun Apr 25 2021 IMPACTS: - Surface wind gusts 18-20 kts possible from 160-180 degrees towards midday Monday. DISCUSSION: High pressure moving east through the Great Lakes, coupled with a dry air mass in the lower levels, will result in no significant low cloud and unrestricted visibility at the terminals through the midday hours of Monday. Model data suggest 850mb winds will increase to 25-30 kts by midday Monday, as the pressure gradient tightens up between the retreating high pressure, and developing low pressure in the Plains. Increased low level mixing by midday Monday may result in some surface wind gusts of 18-20 kts. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ Short Term...50 Long Term...AM Aviation...JAS