Forecast Discussion 18:27:24.6574

…Updated Aviation Discussion…

.Short Term…(This evening through Wednesday)
Issued at 310 PM EST Tue Nov 15 2022

Dreary November weather across the area today as we remain socked in beneath low stratus. Main precip shield has pushed eastward out of the area, however a light mist/drizzle will continue on and off into tonight. Under the thick cloud cover, temperatures have struggled to warm much with most locations currently in the lower to mid 40s, only about 5-10 degrees warmer than this morning’s low temperatures.

As we move into tonight, model soundings indicate we will remain fairly saturated through at least 850 mb, with perhaps a thin layer of dry air attempting to move in at the surface around or after 16/00Z. There may be enough dry air to see some breaks in the drizzle, but confidence remains low as hi-res guidance is much less enthusiastic than the global models with the dry air. Will
continue to monitor potential for drizzle to continue overnight over the next few hours. Lows will generally be in the mid 30s with a few locations potentially falling into the lower 30s.

Low stratus expected to persist into the first part of Wednesday, with cloud bases gradually lifting into the afternoon. Model soundings indicate that we may begin to saturate into the DGZ as lapse rates steepen, and cannot rule out some brief periods of flurries during the morning and early afternoon hours, especially across southern IN into the Bluegrass Region. Similar to today, temps are expected to top out in the lower to mid 40s, well below climatological normals for this time of year.

.Long Term…(Wednesday night through Tuesday)
Issued at 245 PM EST Tue Nov 15 2022

Well below average temperatures and overall wintry conditions will continue into the long term period as an impressive large upper trough remains situated over the eastern two thirds of the CONUS. A shortwave pivoting around the upper low looks to swing through the region Wednesday night, offering additional support and a vort max within the broad scale ascent to possibly result in isolated to scattered very light precip with little to no accumulations. Model soundings suggest we’ll be lacking substantial moisture, with only a shallow layer barely getting into the DGZ to support higher precip chances. Should low level lapse rates become a bit steeper and we can tap into some deeper moisture, then better snow shower chances would be possible. However, that type of environment looks to remain just north of our forecast area for Wednesday night. Some ensemble guidance continues to indicate some very light accumulations mainly north of the I-64 corridor, with the cold-running Canadian and the GEFS both showing a fair amount of members with light snow QPF. NBM gives a 15-20% probability of >0.01″ of snow primarily north of I-64 and across southern IN for the Wednesday night wave, but again, the greater snow probs remain to our north. With all this in mind, will still draw in a silent 10% PoP mainly across southern IN for the Wednesday night period.

The upper flow flattens into a more zonal flow, though below normal temps will make it feel more like January with temps in the upper 30s and low 40s for Thursday. Re-enforcing cold shot comes Friday as sfc high pressure noses eastward into the region and the upper trough strengthens to 2-3 standard deviations below normal. Highs for Friday are a touch cooler, with southern IN counties struggling to make it above freezing, and south-central KY counties not expected to get out of the 30s. Expect to see Saturday morning lows in the teens, though it does not appear to be a record-breaking cold. Current low temp records for SDF, LEX, and FFT are all much lower than the current forecast, but BWG’s record of 17F (1951) could be in jeopardy.

Cold temps persist for Sunday as the upper trough remains overhead, with Sunday morning lows expected to also be in the teens across the region. Sfc high pressure will pass over the region Sunday night, and will bring warm return flow back to the area by Monday and Tuesday. Should see temps gradually rising back into the 40s for Monday and near 50 for Tuesday.


.Aviation…(00Z TAF Issuance)
Issued at 627 PM EST Tue Nov 15 2022

– Drizzle this evening and low clouds overnight


MVFR to IFR conditions are expected to prevail through much of the forecast period. Main band of rain has moved northeast of the region. However, band of drizzle and light rain has moved east of the I-65 corridor and will affect the KLEX terminal this evening. Once this drizzle moves out, cigs should rise into the MVFR range and remain there for the overnight period. Winds overnight will be out of the west at 5-10kts. Cigs look to rise more Wednesday morning with VFR conditions returning by mid-late morning. Winds may be gusty Wednesday afternoon with speeds of 10-15kt and gusts to 20-25kt.


Medium to high confidence on all elements.




Short Term…JML
Long Term….CJP