039 FXUS63 KIND 021656 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 1256 PM EDT Fri Apr 2 2021 ...Updated Aviation Discussion... .Forecast Update... Issued at 1010 AM EDT Fri Apr 2 2021 Going forecast is in good shape as high pressure dominates the area today, with light winds, clear skies, and low humidity. Did lower afternoon dewpoints a bit as latest HRRR runs have us mixing out to the upper single digits to mid teens on dewpoints, with forecast soundings depicting a relatively deep mixed layer even with the fairly tame low level flow. Thankfully, while afternoon minimum RH values will be quite low, fuel moisture and 20 foot winds will not meet criteria for critical fire conditions. Still, will update morning fire products and recent spot forecast request along with grids and zones. Will expire freeze warning on schedule at 11 AM as remaining sites at or below freezing will have come up by then. && .Short Term...(Today through Saturday) Issued at 326 AM EDT Fri Apr 2 2021 Upper ridging paired with surface high pressure will dominate the short term period with strong subsidence. Model soundings show a deep layer of dry air persisting into the weekend which will lead to sunny conditions for the next couple of days. Surface observations early this morning indicate that the center of the high is currently making its way through Indiana as winds have become light and variable across the area. These light winds will continue into tonight while the high slowly tracks eastward. Models then show a surface low forming over the Dakotas tonight that will push towards the Great Lakes. This will create tight pressure gradients and flow at the lower levels which will pick winds up through the day Saturday. Expect sustained winds of 10 to 20 kts with gusts up to around 25 kts. Temperatures will continue to be on the colder side into tonight due to northwesterly flow aloft on the back side of an upper trough. Cold air advection will weaken through the period as the trough continues eastward, towards the Atlantic, which will allow for a warming trend into Saturday. This morning still has a threat of record low temperatures but it will warm to near 50 later today. Near to below freezing temperatures are in the forecast again tonight but Saturday will warm even more into the lower 60s ushering Spring back in. && .Long Term...(Saturday night through Thursday) Issued at 326 AM EDT Fri Apr 2 2021 Saturday Night through Sunday Night... ECMWF shows large and strong surface high pressure in place from Saturday night through Sunday Night...stretching from the Great Lakes to the deep south. This is response to a large...broad ridge that will be expected to be in place across the northern plains and Great Lakes...allowing Pacific air to flow into the Ohio Valley. Thus dry weather will be expected along with mild temperatures. On Monday through Wednesday Night... The ECMWF and GFS agree with the upper pattern early next work week. Both show the broad ridge over the plains translating eastward across the Ohio valley. However the GFS takes a slightly different approach...ejecting some upper forcing dynamics across the Ohio Valley within the flow aloft. Meanwhile the ECMWF keeps the flow aloft relatively clean. Both models suggest a weak warm frontal boundary in place near northern Indiana. Thus a small Pop for this feature appears reasonable on Tuesday into Wednesday. Thursday... Confidence for rain chances appears higher on Thursday as the GFS and ECMWF shows a negatively tilted upper trough in place over the plains...pushing east toward Indiana. A surface low also appears present...riding the previously mentioned frontal Boundary across Central Indiana. Thus at this time chances for rain look best on Thursday. && .Aviation...(18Z TAF Issuance) Issued at 1256 PM EDT Fri Apr 2 2021 IMPACTS: * Only significant operational impact will be gusty winds very late in the period (approx 21015G24KT after 15Z Saturday) DISCUSSION: * Surface high pressure will drift southeast across the area to the Appalachians during the TAF period. As a result, VFR conditions with clear skies and light winds are expected throughout much of the period. Winds will be variable during the afternoon, becoming southerly (190 @ 3-6KT) this evening and overnight. Late in the period, after about 15Z Saturday, a strengthening pressure gradient and diurnal mixing will result in gusty winds out of the southwest at all sites, approximately 21015G24KT. && .IND WATCHES/WARNINGS/ADVISORIES... Freeze Watch from late tonight through Saturday morning for INZ067>072. && $$ Update...Nield Short Term...KH Long Term...Puma Aviation...Nield