Forecast Discussion 12:49:08.4401

…Updated Aviation Discussion…

.Short Term…(This afternoon through Tuesday)
Issued at 240 AM EST Mon Nov 14 2022

Stratus deck continues to hold over our southeast IN and north central KY counties this hour, with notable gaps working on clearing it out from the east. Areas that have cleared out the longest have dropped into the 20’s, whereas other points are in the 30’s.

Aside from some invading high clouds, the lower clouds should continue breaking up through the day. The added sunshine will mean high temperatures today rising much warmer than Sunday’s, likely at least 10 degrees warmer areawide. These readings still will be ~10 degrees below normal for this time of year.

Early morning water vapor loop reveals at least 5 shortwaves west of the MS River in the CONUS. Main global models have these features initialized fairly well. Three of the waves are part of a larger gyre centered over the central US/Canadian border. The one over the Four Corners region will merge in with the flow around this gyre and accelerate quickly towards our region later tonight. As it
approaches, a surface reflection will develop over the northwest Gulf of Mexico, with an inverted trough extending northward to the Lower Ohio Valley. Aloft, a jet streak moving across the Red River Valley will place our area in the left exit region, enhancing lift over that inverted trough. In addition, ahead of the shortwave, we’ll see a 25-30 kt low-level jet focus rain chances over southern KY. Thus expecting likely pops (60-80%), mainly south of I-64 by Tuesday daybreak.

The northern edge of these higher rain chances will have the best chance to stay in the cold long enough for wintry mix chances early Tuesday morning, especially at onset of precipitation. Given the expected short duration, have mostly rain for accumulations. Cannot rule out some small ice and/or snow accums, but not enough for concern at this point.

.Long Term…(Tuesday night through Sunday)
Issued at 335 AM EST Mon Nov 14 2022


Synopsis…Amplified and stagnant pattern will prevail during most of the long term period. CONUS mid-level flow will be characterized by longwave trough and transient shortwave energy reinforcing below- normal upper heights and inducing frontogenesis. Although model uncertainty increases towards the weekend, a more progressive pattern might allow ridging and weak WAA over the Ohio Valley next week.

Model Evaluation/Confidence…Overall, above-average model consensus exist on the synoptic features at play this week; however, details on the mesoscale and higher resolution elements are still pending better agreement. For example, temperature evolution on Tuesday will determine precipitation type. In this case, decide to push highs on Tuesday a few degrees up and towards the NBM 50th percentile which moved the rain/snow line a few degrees northward. On the other hand, went more aggressive with the precipitation chances during the Wednesday-Thursday time frame give the number of ECMWF and GFS ensemble members with measurable snow.

Tuesday…First and strongest shortwave trough will move from the Southern Plains Monday night into Tuesday. While the main surface low pressure will be tracking over the Gulf States, a secondary and weaker low pressure center will transition through the lower Ohio Valley by Tuesday midmorning with very limited WAA, but enough to allow a precipitation transition from an earlier wintry mix to an all-rain event by noon. Given the shallow depth of the saturated layer along with the cold vertical profile, expect cold and small rain droplets throughout the day with overall light QPF.

Wednesday-Thursday…Second shortwave trough passes by and taps into a generally below-freezing, low-level moist layer. As previously stated, ensemble members are actually more adamant with snow QPF during this period. As a consequence, raised and expanded duration of precipitation chances which ultimately translated to higher snow chances and areas with flurries (the latter mainly south of I-64). As for the QPF amount, grids have light QPF but would monitor trends as CAM guidance window starts to cover this period.

Friday-Next Week… Below-average temperatures and dry weather is expected with a warming trend by the end of the weekend amid decreasing model confidence.


.Aviation…(18Z TAF Issuance)
Issued at 1245 PM EST Mon Nov 14 2022

-Chance for precip and MVFR/IFR CIGs around daybreak Tuesday.


Expect VFR conditions to prevail through today and into the first part of tonight, with mid- and high-clouds gradually increasing this evening. As we move into the pre-dawn hours (15/10Z-12Z), ceilings will begin to lower from west to east into MVFR range as precip overspreads the area, with the potential for IFR CIGs by mid-late morning at all TAF sites. While precip looks to fall as mostly rain, certainly cannot rule out a wintry mix early Tuesday morning at KHNB/KSDF/KLEX as surface temperatures hover around the freezing mark. Confidence was too low to include mention of any -SN or freezing precip though. Precip will then push out of the area by early afternoon.




Short Term…RJS
Long Term…ALL