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FXUS63 KLMK 191855 AFDLMK

Area Forecast Discussion National Weather Service Louisville KY 255 PM EDT Sun May 19 2024

KEY MESSAGES

* Dry weather and above normal temperatures weather Monday and Tuesday.

* Unsettled weather late in the week, with highest confidence in showers and storms late Wednesday through Thursday.

* Severe storm potential remains uncertain, with somewhat higher confidence in the potential for localized flooding.

SHORT TERM /THROUGH MONDAY/
Issued at 255 PM EDT Sun May 19 2024

This afternoon, high pressure is located over the region, leading to light winds and mostly sunny skies. A diurnal cu field has developed atop a deep near-sfc boundary layer; these clouds will gradually dissipate this evening as we lose daytime heating. Temperatures have risen into the low-to-mid 80s at this hour, with another 1-2 degrees of warming expected before temperatures start to cool this evening.

Tonight, once afternoon cu dissipates, clear skies are expected through the overnight hours as high pressure remains in control. The combination of clear skies and light winds should promote efficient radiational cooling after sunset, with temperatures in rural areas and valleys dropping more quickly than in the urban heat islands.
Agree with the previous forecast thinking that any fog which develops Monday morning should be confined to river valleys and sources of greater sfc moisture, as low-level mixing this afternoon has helped to bring somewhat drier air down to the surface.
Temperatures Monday morning should be fairly similar to this morning, with lows ranging from the upper 50s in rural areas and river valleys to the low-to-mid 60s.

Tomorrow, the large-scale pattern across North America will feature digging upper level troughing along the west coast, SW flow across the central Plains and upper Midwest, with ridging extending SW to NE from the southern Plains across the Ohio Valley and into the northeastern US. While the center of sfc high pressure will be east of the Appalachians tomorrow, the pressure gradient will remain weak over the Ohio/TN valleys, with light S/SW winds setting up during the late morning and afternoon hours. Ridging and associated warm temperatures aloft should suppress convection tomorrow afternoon, although FEW-SCT diurnal cu would be expected to develop in the presence of marginal low-level moisture. The combination of slightly higher heights aloft and very weak warm advection should allow us to add 1-2 degrees over persistence, with highs expected to top out in the mid-to-upper 80s Monday afternoon.

LONG TERM /MONDAY NIGHT THROUGH SATURDAY/
Issued at 255 PM EDT Sun May 19 2024

Monday Night through Tuesday Night...

Upper ridging over the eastern CONUS will support very warm temps and suppress most if not all convection. Temp forecast is a bit tricky given that vegetation is quite green and soil moisture is plentiful. GFS output is showing its typical seasonal warm bias, but other guidance still supports highs in the mid/upper 80s, close to 10 degrees above normal.

Wednesday through Sunday...

Overall pattern turns unsettled for the latter half of the week as southeast CONUS ridging breaks down. POPs ramp up on Wednesday as a cold front moves into the Ohio Valley. Model soundings show modest instability developing Wednesday afternoon, so severe wx can't be ruled out completely. However, shear is weak as the stronger westerlies remain to our north. As such, expect SVR potential to be limited, but locally gusty winds and heavy rainfall are possible.

Additional waves of showers and storms are possible Thursday and Friday, but timing is tricky. More confident in Thursday as the front will be dropping slowly through Kentucky. Look for a break at some point as the front drops southward into the Tennessee Valley, but POPs increase again sometime Friday as the boundary waves back northward as a warm front. Shear remains weak, so our typical pulse threats of localized gusty winds and heavy rain will be the main hazards.

POPs remain in the chance range through the weekend as additional disturbances move through, but would not expect a washout by any means. Intervals of showers and storms, with substantial dry periods in between, will be the flavor of the weekend. Temps through the week will be near normal by day, just either side of 80, and solidly above climo at night given the humid and at times cloudy environment.

AVIATION /18Z TAFS THROUGH 00Z TUESDAY/
Issued at 127 PM EDT Sun May 19 2024

High pressure will move across the region today into tonight, with light winds and VFR conditions expected across all forecast sites.
Diurnal 5 kft cu field will gradually subside this evening, leaving mostly clear skies overnight. Light NE winds will calm after sunset, with winds remaining calm or very light until mid-morning Monday.

The only potential impact during the current forecast period would be potential re-emergence of fog before sunrise Monday. Would expect RGA to have the highest chance to see fog Monday morning since fog was observed there this morning; however, drying in the low-levels this afternoon will mean that temperatures will not fall nearly as far below crossover values tonight into Monday morning. Will leave fog mention out of the forecast for now due to low confidence.

LMK WATCHES/WARNINGS/ADVISORIES
KY...None.
IN...None.

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