Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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594 FXUS63 KLMK 280518 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 118 AM EDT Tue May 28 2024 .KEY MESSAGES... * Dry weather and below normal temperatures expected for most of the upcoming week. * Rain chances return for the weekend; severe weather is not expected at this time. && .UPDATE... Issued at 946 PM EDT Mon May 27 2024 Had a few scattered showers pop up this evening across south-central KY. These have moved on off to the southeast and out of the CWA. IN their wake, skies were clear to partly cloudy across the region with temps in the mid-upper 60s in most spots, though a few places were still in the lower 70s. Quiet weather is expected overnight. Probably will see some shallow fog across southern KY, if any dense fog forms, it would be in the lower river valleys. Overnight lows in the upper 50s look on target. && .SHORT TERM /THROUGH WEDNESDAY/... Issued at 315 PM EDT Mon May 27 2024 Synopsis...Stagnant upper-level trough over Great Lakes will keep the Ohio Valley under broad cyclonic flow with several shortwave energy pieces and mid-level wind speed maxima tracking north of the Ohio River. At the surface, slow-moving cold front will continue sagging southward tonight as high pressure ridge filters in from the west. Rest of Today...Surface observations and visible satellite imagery locate the frontal boundary crossing the Ohio River early this afternoon. A wind shift and dropping dewpoints is readily noted in the postfrontal airmass with highs forecast to stay around 80 degrees in the modified warm sector and slightly lower north of the boundary. In addition, the earlier stratus layer has evolved into a cumulus deck and although convective temperatures have been met in most cases and there is available instability along and ahead of the front amid steepening low-level lapse rates, the lack of sufficient mesoscale forcing, dry air aloft, and a capping inversion will discourage any chances of precipitation this afternoon. Otherwise, gusty winds will continue at least until sunset. Tonight...Winds will subside after sunset as nighttime stability decreases mixing in the BL. Decreasing dewpoints and lighter winds will allow morning lows to be around seasonal spring values. Also, the combination of light winds and recent rainfall could end up favoring shallow fog across south-central KY later tonight which could get more dense along the river valleys and other protected areas. There is low to medium confidence in fog based on pattern and HREF visibility output. Last but not least, upstream convection over the MO and IL this afternoon will weaken as it moves towards western Kentucky. Some models show isolated showers moving into the area overnight, but chances are too low to include it in the forecast at this moment. Tomorrow...Quiet conditions will continue tomorrow as mid-level air remains fairly dry and subsidence aloft maintains an inversion in place. Winds will remain somewhat gusty from midmorning until sunset once again with an average west to northwest direction. All HREF members show afternoon convection over central Indiana as another mid-level shortwave impulse moves over the region, but coverage further south is uncertain at the moment and given other elements favoring a dry forecast, decided to leave PoPs out. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Issued at 315 PM EDT Mon May 27 2024 Large-scale upper level troughing will continue across the eastern half of North America for much of the mid-week period, with smaller- scale shortwave disturbances swinging along its southern periphery. One of these shortwave disturbances is expected to move across the Midwest and upper portions of the Ohio Valley late Tuesday night into Wednesday, providing support for mid-level ascent via differential CVA. With model soundings showing reasonable amounts of moisture in the 925-700 mb layer Wednesday, would expect there to be an increase in diurnal cu, with a slight chance for a rain shower or low-topped thunderstorm across portions of the KY Bluegrass Wednesday afternoon. Otherwise, much of the period Tuesday night through the end of the week will be quiet across central Kentucky and southern Indiana, with below normal temperatures expected. A reinforcing shot of cool and dry air will move into the region Thursday into Friday behind Wednesday`s shortwave disturbance as high pressure centered over lower MI will promote low-level NE flow across the Ohio and TN valleys. There is relatively high forecast confidence in dry weather during this period, with EPS Ensemble mean PW values being below the 1st percentile for this time of year. Additionally, the ECMWF MinT EFI is around -0.7 for Friday morning, indicating medium-high confidence in anomalously cool low temperatures. The current forecast calls for lows in the upper 40s and low 50s Friday morning, but would not be surprised if some of our river valley locations fall into the low-to-mid 40s. Daytime highs for the second half of the week are generally expected in the mid-to-upper 70s. This coming weekend, another upper trough will push into the north central CONUS, with some of the associated energy diverting southward into a low-amplitude wave that will move across the Mississippi Valley on Saturday. As this wave moves into the Ohio Valley, resultant low-level southerly flow and moisture return will overspread the region next Saturday, leading to a return of daily chances for showers and thunderstorms. With mid- and upper-level flow expected to be weak, shear should be negligible, curtailing any severe potential. CSU ML probabilities and CIPS severe analogs reflects this, keeping any severe probabilities west of the Mississippi Valley. && .AVIATION /06Z TAFS THROUGH 12Z WEDNESDAY/... Issued at 117 AM EDT Tue May 28 2024 VFR conditions expected for most sites through the TAF period. Some patchy, shallow fog may develop in the more fog-prone locations near dawn but should be short lived. Winds will pick up this afternoon as the boundary layer mixes out and gusts could exceed 20kts at times. Winds will subside this evening near sunset. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ UPDATE...MJ SHORT TERM...ALL LONG TERM...CSG AVIATION...DM