Area Forecast Discussion
Issued by NWS Louisville, KY

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000 FXUS63 KLMK 050304 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 1004 PM EST Thu Mar 4 2021 .Forecast Update... Issued at 1004 PM EST Thu Mar 4 2021 Surface high pressure nosing in from the north and a dry atmosphere will provide us with light winds and clear skies overnight. It will be chilly with the mercury falling into the middle and upper 20s in most places, about 5 to 10 degrees colder than normal. No changes to the forecast needed. && .Short Term...(This evening through Friday) Issued at 225 PM EST Thu Mar 4 2021 Current satellite shows clear skies across the region as regional observations show temperatures in the low 50s across southern Indiana and into the low 60s across southern KY. Surface analysis shows a weak cold front stretched W-E across central KY with a 1033mb high pressure centered over Ontario and another 1022mb center over ArkLaTx. Ridging aloft will begin to weaken a bit as an upper low moves from the Four Corners eastward toward the Lower MS Valley, filling as it goes and eventually becoming enveloped within the upper flow. As a result, southern KY will see increased mid and high cloud cover Friday afternoon through evening. Otherwise, expect slightly cooler temperatures Friday with morning mins in the mid 20s across the Bluegrass and in the low 30s across southern KY. Highs Friday will reach into the upper 40s to low 50s. .Long Term...(Friday night through Thursday) Issued at 250 PM EST Thu Mar 4 2021 ...COOLER WEATHER THIS WEEKEND WITH A WARM UP NEXT WEEK... ...HEAVY RAINFALL THREAT DEVELOPING BY LATE NEXT WEEK... ======================================== Synoptic Overview ======================================== Amplified upper level pattern is expected at the beginning of the forecast period (Friday night) with a broad/deep trough axis over the eastern third of the US with ridging over the Rockies. The eastern US trough axis will slowly move off to the east by early next week. The upper level pattern will undergo significant changes next by early-mid next week as a large and powerful trough pushes into the western US. As this occurs, downstream ridging will build over the central and eastern US which will allow temperatures to moderate and become quite mild across the central and eastern US. As the western US trough heads eastward into the Plains, a large synoptic scale cyclone is expected to develop with widespread showers and storms expected across the Plains. The shower and thunderstorm activity will then shift into the Ohio and Tennessee Valleys toward in the later half of the week and linger into next weekend. The set up may bring a renewed threat of heavy rainfall to the Ohio Valley late next week. ======================================== Model Discussion and Sensible Weather ======================================== Overall, the global models are in decent agreement throughout the upcoming long term period. Model continuity has been fairly good and the ensembles are generally good agreement. There is some spread in the Wed/Thu time frame, but nothing out of the ordinary when talking about spread in the day 6/7 forecast period. The guidance suggests a rather cool weekend across the area with lows Friday night in the mid-upper 20s with highs on Saturday remaining in the lower 40s across the Bluegrass with 45-50 across the I-65 corridor and points west. Temperatures look to moderate slightly on Sunday with highs in the upper 40s in the Bluegrass with lower 50s elsewhere. Southerly flow should start to kick in on Monday with highs warming into the lower 60s along and west of I-65 with mainly mid-upper 50s out in the I-75 corridor. Overnight lows still look to average out in the upper 20s to the lower 30s. As heights build aloft on Tuesday/Wednesday we should start to see much milder weather develop Highs look to hit the 60-65 degree mark by Tuesday and may get into the 65-70 range by Wednesday. The guidance through this period is probably too cool as the global models always under estimate high temperatures under deep southwesterly flow. So I suspect that if the current forecast pattern holds, then highs will likely trend warmer in subsequent forecasts. By mid-week a large Plains cyclone should develop and shift into the Great Lakes. The trailing cold front will likely spark a corridor of strong to possibly severe storms over the central Plains. This activity will spread eastward into the Ohio Valley by late Wednesday and into the day on Thursday. Temperatures will probably remain pretty mild here with highs in the 60s. Looking past Thursday we have some concerns about how the pattern may evolve by late week. There are signals within the data that a new upper trough axis may move into the western US resulting in the upper level flow remaining more west-southwesterly across the OH/TN Valleys by late week. Should this scenario unfold, the late week cold front may stall out across the Ohio Valley and serve as focus for renewed convective development as additional waves translate eastward within the flow regime aloft. This could result in another period of excessive rainfall and possible flooding and river flooding by late next weekend and into week two. ======================================== Societal Impacts ======================================== No real societal impacts are expected this weekend and into next week. However, ongoing flooding along the Kentucky, Ohio, and portions of the Green River will continue into next week. Warmer temperatures will be noted during the mid-week time frame. Record high temperatures do not look to be hit during this period. However, there is a risk that we could tie or break some overnight warm minimum temperatures by mid-late week in our southern forecast area. Moderate to heavy rainfall may lead to hydrologic issues by late week and into the weekend if significant rainfall develops. Given wet antecedent soil conditions, runoff could be rather quick with possible quick rises on area creeks and streams. Residents in low- lying and flood prone areas should keep an eye on forecasts next week and be prepared for another round of flooding as early as next weekend. ======================================== Forecast Confidence ======================================== Weekend Temperatures : Moderate-High Expected Warmup Next Week : Moderate Possibility of late hydro issues: Low-Moderate && .Aviation...(00Z TAF Issuance) Issued at 540 PM EST Thu Mar 4 2021 Surface high pressure spilling southward from the Canadian Archipelago to the Ohio Valley will keep our weather quiet during this TAF period with light NW-NE breezes. A weakening 5H low traveling from DEN to LIT will bring high clouds to the region on Friday. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...13 Short Term...CG Long Term...MJ Aviation...13

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