####018010524#### FXUS63 KIND 231243 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 843 AM EDT Tue Apr 23 2024 .KEY MESSAGES... - Afternoon/evening rain expected. Total QPF under a half inch. - Cooler mid-week, with some frost possible Wednesday night for North Central Indiana - Active pattern returns Friday into next week with above normal temperatures and numerous storm chances && .FORECAST UPDATE... Issued at 841 AM EDT Tue Apr 23 2024 - Increasing Clouds with afternoon Rain Surface analysis late this morning shows low pressure over Lake Superior and a second area of low pressure was in place over SW OK. A cold front across WI, IA and NE KS connected these two lows. Broad and elongated high pressure was found across the east coast. This was resulting in southerly flow across Central Indiana, however the high pressure system was effectively blocking moist gulf flow from reaching the Ohio Valley. Aloft, a moderate short wave was found over MN and SW Ontario, with a trough axis extending SW across SD. This was resulting in moderate westerly flow aloft across Indiana. This short wave was being influence by the broader cyclonic flow across northeast North America as a deep upper low was anchored near Hudson Bay. GOES16 shows abundant cloud cover ahead of the frontal boundary, pushing toward Central Indiana. An area of rain was found over NE MO and western IL, pushing east. Dew points across central Indiana remained quite dry, in the middle 30s, resulting in current dew point depressions of 15-20F. The upper short wave over the northern plains is expected to pivot a trough axis southeast across Central Indiana this afternoon before exiting this evening. The associated cold front is expected to slowly advance southeast and elongate somewhat this afternoon. HRRR suggests advection of the clouds and precipitation to west to reach much of Central Indiana through the afternoon hours. Forecast soundings also show a brief period of column saturation late in the afternoon. This seems reasonable considering the dry lower levels and large dew point depressions. Thus will try and focus highest pops during the mid to late afternoon hours, when this best moisture is suggested to arrive. Given the expected increasing cloud cover and rain arrival, highs around 60 will be expected, with low to mid 60s south. && .SHORT TERM (Today and tonight)... Issued at 301 AM EDT Tue Apr 23 2024 Latest surface analysis shows a surface low located over Northern Lake Superior with a front extending southwest toward another surface wave across the Front Range in Colorado. Energy from that wave rides along the front as it slowly pushes southeastward through Indiana this afternoon and evening increasing rainfall coverage and intensity. Latest hi-res guidance continues to slow down the front and arrival of rain across the region, so have continued the trend in the forecast. Latest satelitte and radar imagery show scattered areas of clouds and showers along the front associated with an upper level wave along the Kansas/Nebraska Border. Expect this activity to continue its eastward progression through the day, expanding in coverage along the front. Although latest sounding and ACARs data from around the Midwest shows a very dry profile in the lowest 5 km of the atmosphere. In fact, latest observations still show dew point depressions of 20-25 degrees across Indiana and points west. With such a dry low and mid level profile, it is going to take a while for the column to saturate and for precip to reach the ground. This adds to the confidence in a later start time for rainfall across Indiana. QPF values are likely a bit overdone as well as guidance is likely not handling the very dry antecedent conditions very well. While rainfall amounts were already forecasted to be under a half inch, it is likely that most areas will see around a third of an inch or less. With all that said, best forcing for ascent and saturation through the column arrives during the 19-22z timeframe this afternoon with the arrival of the mid level energy riding along the front. This can easily be seen in 850mb maps as the low level jet ramps up to 30-40 kts. Forecast soundings by 18Z show good saturation in the mid and upper levels across the area with pwats around 1 inch. Recent guidance does keep the boundary layer fairly dry as low level moisture advection will likely be lagging as much of the deep Gulf moisture is blocked from pushing north due to a strong area of high pressure and associated subsidence across the Gulf Coast. While forcing seems quite favorable for precip, moisture is somewhat limited. Thus a light rain is expected. So we are looking at high confidence, low amount type rain event. Furthermore, forecast soundings fail to show much instability, so any thunder will be minimal to none. With a drier atmosphere and later arrival of rainfall, bumped highs up across the region several degrees into the mid to upper 60s for South Central Indiana and lower 60s for North Central Indiana. Despite increasing clouds, greater boundary layer heating today will allow for greater mixing to occur resulting in winds in the low level jet and drier air being brought down to the surface. Winds may gust upwards of 20-30 kts at times this afternoon ahead of the approaching front. This may promote even drier air also mixing down to the surface ahead of the rainfall, further working to keep rainfall amounts fairly light. && .LONG TERM (Wednesday through Monday)... Issued at 301 AM EDT Tue Apr 23 2024 On Wednesday, cold advection in the wake of departing shortwave trough will overspread the central part of the state. This will moderate readily given the degree of diabatic surface heating this time of year. However, a subsequent minor shortwave perturbation looks to be enough to cause lingering stratus across roughly the northeastern half of the state. This could result in a 10-12 degree temperature gradient across central Indiana. Temperature forecast uncertainty is above average. By Thursday pronounced ridging will be building into the Mississippi Valley with a shortwave trough emerging onto the Plains. Temperatures moderate some but the warm front and associated warm advection-driven precipitation hold west until Friday. Temperatures should be warmer Friday with pronounced warm advection in response to aforementioned Plains mid-latitude system, although this may be offset some by clouds and precipitation. It appears as of now, precipitation would be most likely the latter half of the day, though this timing may need to be adjusted. Precipitation should mostly be from a northwest to southeast oriented warm frontal rain band with some embedded convection/thunder given the presence of weak instability. Models show a weakening of this shortwave trough and a track holding stronger height falls/forcing to our northwest. Nevertheless, its warm conveyor belt and associated broad/strong IVs signal will be positioned over Indiana late Friday into early Saturday and support precipitation during that time. The track and life stage of the cyclone by then will mean steeper midlevel lapse rates will be displaced from the warm conveyor belt and so this should limit intense convection and severe potential. Also, this pattern will support cold advection holding to the northwest without a push into Indiana, so temperatures will remain warm through the weekend and into early next week. A more classic frontal band scenario with greater instability looks to arrive late Sunday or Monday with the next shortwave trough. This looks to take a similar path as the previous, but is broader/stronger with greater forcing and steeper midlevel lapse rates. Thus, a more robust QPF signal and a better chance of severe storms. This is supported by a broad relatively low probability CSU machine learning signal. For the Day 8-14 period, early indications are for ridging and anomalous warmth over the east and positive precipitation anomalies staying to our west. There is too much chaos in the ensembles to identify a specific impact, but given the overall synoptic pattern indicated some convective hazard risk may exist during this period. && .AVIATION (12Z TAF Issuance)... Issued at 631 AM EDT Tue Apr 23 2024 Impacts: - LLWS through around 18z - Rain moving in this afternoon and evening, periods of MVFR cigs and vis - SW to W winds increasing after sunrise to 12to 18 kts with gusts up to 30 kts Discussion: VFR conditions persist early this morning across all of Central Indiana. A front will slowly push southeast through the state later today bringing a period of rain with winds shifting from southerly to westerly into the evening. Latest guidance continues to push back the timing of the rainfall arrival, so have kept the TAFs more optimistic for much of the day. Expect conditions to begin deteriorating around late morning to early afternoon for KLAF, then after 20z for KHUF, KIND, and KBMG. MVFR cigs and cigs expected at times during the rain, however conditions should become VFR again during the 00-06z timeframe. Very slight chance of an isolated lightning strike along and south of I-70 later this evening, but confidence in that occurring is too low to mention it in the TAF. There will be a threat for LLWS through around 18z. Latest ACARS soundings does indicate a strengthening southwesterly low level jet overhead; however winds at the surface have not responded due to a low level inversion. Once mixing begins later this morning, stronger winds will mix down to the surface. Winds early this morning are from the SW near 7-10 kts. Sustained speeds will increase to near 15 kts after sunrise with gusts up to 30 kts possible through much of the day. Wind direction will become more westerly by the end of the TAF period. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Puma SHORT TERM...CM LONG TERM...BRB AVIATION...CM ####018006323#### FXUS64 KMRX 231243 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 843 AM EDT Tue Apr 23 2024 ...New UPDATE... .UPDATE... Issued at 828 AM EDT Tue Apr 23 2024 No significant changes were made to the forecast for today. Today will be dry, breezy and warmer. Southwesterly winds will gust up to 25 mph this afternoon in the Tennessee Valley. With a dry air mass in place and clear skies bringing good mixing conditions, relative humidity values may get into the 20 percent range this afternoon despite WAA. The good news is that fuel moisture levels are likely high enough to keep fire danger limited. && .SHORT TERM... (Today and tonight) Issued at 256 AM EDT Tue Apr 23 2024 Key Messages: 1. Frost Advisory remains in effect until 9AM ET. See product for additional details. 2. Dry and breezy this afternoon. 3. Increasing chances of rain overnight into the first half of Wednesday. Only light rain is expected before becoming mostly dry for Wednesday afternoon/evening. Discussion: A surface cold front has led to scattered radar returns across portions of the midwest and into the Great Lakes region. This has resulted in some minor high clouds advecting across the area. Additionally, most recent surface observations have a wide range of dewpoints from lower 40s to upper 20s, along with a few places holding onto a light(3-5kt) wind. A Frost Advisory remains in effect until 9AM EDT as patchy frost is possible, primarily in sheltered valleys where there is a lower likelihood of aforementioned light winds/clouds weakening favorable radiational cooling. Tuesday afternoon will be dry as high pressure remains in control ahead of the aforementioned approaching surface boundary. A tightening pressure gradient and favorable mixing will result in low relative humidities and breezy southwest winds throughout the afternoon hours. Have continued to headline this in the FWF. An upper level shortwave will drive the cold front into the region overnight Tuesday, with rather light precipitation of a tenth of an inch or less expected for most. Locally higher totals will be possible within the East Tennessee mountains where orographic lift helps squeeze out as much moisture as possible. The best chances for rain exist in the northern half of the area during this Tuesday night through early Wednesday timeframe. Rain chances gradually come to an end around mid-day Wednesday, as most places should remain dry for the afternoon and evening. && .LONG TERM... (Wednesday through Monday) Issued at 256 AM EDT Tue Apr 23 2024 Key Messages: 1. Overall, mostly dry extended forecast into the weekend. 2. A warm-up with temperatures becoming above normal with breezy conditions late week and into the weekend. 3. A chance of showers and thunderstorms return early next week. Discussion: Overall, the extended will be dominated by upper and surface ridging into the southern Appalachians and southeast United States. Ridging will block upper forcing well west and northwest of the area and limit deep moisture and instability return into the southern Appalachians. Best chance of showers and increased moisture/instability return early next week. For Wednesday night through Thursday night, building upper ridge and surface ridging across the southern Appalachians into southeast United States will produce dry and warm conditions. For Friday, an upper jet moves northeast across the mid-section of the nation strengthening the low-level jet over the western Ohio and Tennessee valleys. The deterministic models, especially the GFS, suggests an area of isentropic forced scattered showers will lift north over the area. However, the ensemble probabilities from the NBM depict meager chances (10 to 30 percent) at most. This seems reasonable given the continued surface ridging into the southeast/eastern Gulf coast states limited moisture return. For Saturday and Sunday, ridging surface and aloft builds into the southern Appalachians producing unseasonably warm and dry conditions. There may be a few showers develop across the higher elevations due to orographic lift but overall dry. Temperatures will be some 5 to 10 degrees above normal. For Monday, another jet moves from the mid-section of the nation into the Great Lakes/Ohio valley. In response, a frontal boundary moves into the Tennessee valley. NBM ensemble probabilities are more aggressive with chances of measurable rainfall as well as higher SBCAPE. Chance of showers and thunderstorms will return for early next week. && .AVIATION... (12Z TAFS) Issued at 658 AM EDT Tue Apr 23 2024 VFR conditions will persist, with some high clouds atop the region at times. Main aviation concern will be southwest winds becoming gusty this afternoon. Sustained winds are expected to be around 10-15kts with gusts between 20-25kts. Gusts should diminish by the evening/overnight hours. Rain chances will increase early Wednesday morning at TYS and TRI. Current indications are conditions will remain VFR at this time. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 75 54 76 50 / 0 10 10 0 Knoxville McGhee Tyson Airport, TN 72 55 72 47 / 0 30 30 0 Oak Ridge, TN 72 54 74 47 / 0 40 30 0 Tri Cities Airport, TN 69 50 68 42 / 0 40 40 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...Frost Advisory until 9 AM EDT this morning for Cherokee-Clay. TN...Frost Advisory until 9 AM EDT this morning for Blount Smoky Mountains-Campbell-Claiborne-Cocke Smoky Mountains-East Polk-Hancock-Hawkins-Johnson-Morgan-Northwest Carter- Northwest Cocke-Northwest Greene-Scott TN-Sevier Smoky Mountains-Southeast Carter-Southeast Greene-Southeast Monroe-Sullivan-Unicoi-Washington TN. VA...Frost Advisory until 9 AM EDT this morning for Lee-Russell-Scott VA-Washington VA-Wise. && $$ SHORT TERM...KRS LONG TERM....DH AVIATION...KRS