908 FXUS63 KLMK 282328 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 728 PM EDT Thu Mar 28 2019 ...Updated Aviation Discussion... .Short Term...(This evening through Friday) Issued at 300 PM EDT Thu Mar 28 2019 Southern Indiana and central Kentucky are south of the jet stream which is near the Canadian border. Over the Ohio Valley, mid-level flow is weak and un-amplified. At the surface, high pressure sits over the southeastern United States, and a low pressure center sits over the panhandle of Oklahoma. A cold front extended from this low to the northeast. Ahead of the cold front, moist flow from the Gulf of Mexico flows north. Surface convergence will cause rain showers that will advance into southern Indiana tonight after midnight. With dewpoints in the 30s a lot of dry air is in place that any rain showers will have to over come. With so much dry air in place, rainfall totals of a 0.1" and less are expected. Low temperatures should be mild tonight staying in the mid 50s with a southern wind and cloud cover. Tomorrow, the same conditions continue as the cold front inches closer from the west. Rain chances in the afternoon will decrease in south central Kentucky. Highs will make it into the 60s with the warmer of those temperatures to the south. .Long Term...(Friday night through Thursday) Issued at 300 PM EDT Thu Mar 28 2019 Friday Night - Saturday Night... A surface low moving out of the eastern Plains is expected to ride along an initially stalled frontal boundary just to the north of the CWA Friday night. This feature is expected to move to the eastern Great Lakes by midday Saturday, which will lift the initial stalled frontal boundary north as a warm front early in the day then drag a secondary and strong cold front through the area later Saturday ahead of a strong shortwave trough axis. The aforementioned synoptic setup will lead to light showers associated with isentropic lift mainly across our northern CWA along the stalled frontal boundary. Expect a mild overnight given decent southerly flow, and cloud cover. Most lows will only drop to the mid 50s. The warm sector becomes better established on Saturday over the area, with gusty SW winds and temps warming just above normal into the 60s in the warm sector. Widespread rain and embedded thunderstorms are then possible through Saturday ahead of the cold front and sharpening shortwave trough axis where most amounts will total in the 0.5"-1" range across the region. Can't rule out a narrow axis of weak surface based instability on Saturday, however severe potential looks low as the best chances would be south and west of the CWA. Will keep an eye on instability trends and the chance for a stronger storm or two on Saturday. Otherwise, the main threats will be brief heavy rainfall, a few cloud to ground lightning strikes, and perhaps some gusty winds. The cold front passes through later Saturday afternoon and evening, with precipitation ending from W to E as this occurs. Temperatures will fall off pretty dramatically behind the cold front, and should be in the 30s by dawn on Sunday. At this point, it looks close with regard to cold air catching up to the back side of any lingering precipitation chances, but will lean things being dry by the time cold air arrives to support anything other than rain. Sunday - Thursday... ...Freeze Potential Sunday Night/Growing Season Has Progressed In Areas of Kentucky... Strong Canadian surface high pressure and dry NW flow aloft will dominate the Sunday and early week time frame, bringing dry and cooler (below normal temps) conditions to the region. In fact, there is concern for a fairly hard freeze Sunday night/Monday morning as temps drop into the upper 20s. Will likely be starting up frost/freeze wording as UK Ag informed us that the growing season has progressed in southern KY. Future headlines may be needed for Sunday night. The upper pattern will transition to a zonal and then deeper SW flow pattern by mid to late week, resulting in a steady warm up through that time. There is some signal of a weak system passing to our south on Tuesday, however not too confident in this feature given model variability. Highs are expected to be above normal in the 60s and 70s by Wednesday and Thursday. && .Aviation...(00Z TAF Issuance) Updated at 728 PM EDT Thu Mar 28 2019 A quasi-stationary front reaching from the St Lawrence Valley to the southern Plains will be a focal point for showers during this TAF period. HNB and SDF will stand the best chances of rain and MVFR vis/cig, especially as a small wave moves overhead late tonight and another approaches Friday afternoon. Low level winds will increase off the surface tonight ahead of the boundary, coming in from the SSW around 30-35kt at 2k' producing borderline LLWS. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Short Term...KDW Long Term...BJS Aviation...13