As usual, twitter is on fire with extreme snow totals for Indiana. Do not trust these:
On the other hand, you can most certainly trust the National Weather Service's Twitter feed which has this:
As you can see, there is a disagreement here. The National Weather Service has the far northwestern part of Indiana highlighted for the best chances of impact.
If you are interested in the nitty-gritty details from the National Weather Service, you can read them here:
Area Forecast Discussion National Weather Service Indianapolis IN 218 PM EST Fri Jan 20 2023 .Short Term...(This evening through Saturday) Issued at 217 PM EST Fri Jan 20 2023 - Mostly Cloudy and Cold Tonight - Partly cloudy Saturday Morning, increasing clouds during the afternoon Surface analysis early this afternoon shows deep low pressure exiting out to the Atlantic east of New England. An associated trough axis extended west across Lake Ontario to southern WI. Broad, cold but poorly organized high pressure found across the Great Plains. The result of these two systems was continued cyclonic flow across Indiana and the Ohio Valley. GOES16 showed extensive lower level clouds in place across Central Indiana, the Ohio Valley and points upstream within the flow. Radar shows a few areas of flurries pushing across Central Indiana within the cyclonic northwest flow. A moderate pressure gradient was noted across the area within this broad cyclonic flow resulting in some gusty winds. Tonight... Weak ridging aloft is suggested to build across Indiana and the Great Lakes late tonight before becoming a bit more predominant on Saturday. Subsidence is noted within the mid and upper levels as the ridge builds across the area tonight, as drying is seen within the forecast soundings and time heights but a different story resides within the lower levels. The ongoing cyclonic lower level flow is expected to become more just northwesterly as the deep surface low continues to depart east. However, ridging within the lower levels fails to arrive until after 12Z Saturday. Given the extensive cloud cover as seen on GOES16, we are not confident for much clearing. Time heights keep saturation within the lower levels overnight while forecast soundings try to dry the lower levels out overnight. Thus given the abundance of clouds and the lack of strong clearing signal, we will keep skies mostly cloudy tonight. Given the expected cloud cover, will trend lows to low to middle 20s. Saturday... The models on Saturday show ridging building aloft over Indiana before exiting to the eastern Great Lakes by late afternoon. Meanwhile a broad trough over the plains is expected to begin to approach Central Indiana by late in the afternoon. Meanwhile at the surface, high pressure is expected to be moving through the Ohio Valley. Forecast soundings show a dry column across the area for the day. Thus some morning clouds could be lingering from the overnight period, but as heating and mixing resumes through the morning, we should see some clearing. High clouds will then be expected to return late in the afternoon as the previously mentioned approaching trough should begin to advance toward Indiana. Isentropic surfaces show best lift arriving late in the day over Illinois, but some of the cloud cover should begin to advance as the day progresses. Thus increasing cloud cover as the afternoon progresses. Any precipitation will hold off until the Saturday night period as that is when better forcing will arrive and time will once again be needed to saturate the dry column. Given the warm air advection ongoing and some sunshine expected highs near 40 will be reasonable. && .Long Term...(Saturday night through Friday) Issued at 217 PM EST Fri Jan 20 2023 Long Term *Light Snow Accumulations Late Saturday Night/Early Sunday *Potential Impactful Winter System Mid-Week Next Week Saturday Night and Sunday. An active weather pattern will be in place for much of the long term period with two major weather systems impacting central Indiana. The first system will arrive Saturday night into Sunday as a broad and gradually deepening trough exits the Four Corners region and pushes into the Central Plains. Gulf moisture will only penetrate as far as Tennessee which will limit the available moisture across central Indiana. There looks to be 2 areas of heavier snow accumulation with the main area of surface convergence in the southeast and a secondary area associated with the more robust cold air to the northwest. Where those two line up remains uncertain so will keep the snow accumulations fairly broad brushed at 0.5" to 1.0" with the thought that there will likely be an axis of 2-3 inches somewhere across Indiana. Monday and Tuesday. There may be a few residual snow showers Monday if the system ends up being slower, but think that most of Monday and Tuesday will be dry with a gradually warming trend as surface flow returns to the south. Wednesday Through Friday. The second and more impactful system of the week then looks to arrive Wednesday into Thursday as a rapidly deepening upper level trough and associated surface low pushes into the Southern Plains and tracks to the northeast. Model ensembles generally have a solid handle on the track with the operational GFS on the northern edge of the ensemble mean. There are likely to be some sections of the forecast area that see mostly rain and some that are mostly snow, but where that sets up remains very uncertain. One thing to note with these systems is that a typical pattern for these negatively tilted systems is for the surface low to follow the track of the 500mb low more closely when deepening. This more closely matches the current GFS run while the Euro has it further southeast which is more typical if deepening is not occurring. With all that in mind, an impactful winter system looks likely across portions of the upper Wabash Valley with the main uncertainty being the rain/snow line and how intense the snow bands will set up northwest of the surface low. The system has very strong dynamics and abundant moisture to allow for significant snow amounts, but there are a couple of factors that will limit snow accumulations. The first will be the warm air on Tuesday and Wednesday which will warm the ground and help melt the initial snow. Warm air aloft will also keep the snow out of the dendritic growth zone and push snow ratios closer to 8:1. All this gets factored in well by the model guidance which is showing an axis of 6-10 inches of snow accumulations, but a snow depth of only 3-5 inches. Will have to continue to monitor the model trends, but lean more towards the lower amounts for now, especially with the uncertainty as to P-type. The primary impacts look to be during the daytime hours Wednesday, but confidence in timing is still somewhat low. The typical post frontal flurries/light snow may then continue Thursday into Friday. && .Aviation...(18Z TAF Issuance) Issued at 126 PM EST Fri Jan 20 2023 Impacts: * MVFR Cigs expected today and early this evening. Discussion: GOES16 shows extensive cloudiness across the forecast area with widespread MVFR Cigs. broad cyclonic flow is expected to remain across the area today. Tonight the cyclonic flow appears to weaken, however there is a lack of a strong anti-cyclonic signal or clearing ridge axis. Thus confidence is low for clearing of cloud cover. Forecast soundings and time heights show a saturated area within the lower levels through much of the forecast period. Thus will keep MVFR Cigs this afternoon and evening and return to low VFR Cigs tonight as the cyclonic flow weakens while lower level moisture remains.
No comments:
Post a Comment