Snow begins by Sunday afternoon and peaks Sunday night, wrapping up Monday morning. For my listeners/viewers/followers in:
—Indianapolis: expect 5-10 inches…
—Hendricks County: 5-10 inches…
—Lafayette 2-5 inches…
—Muncie 3-6 inches…
—Lima Ohio 2-5 inches…
TODAY’S MAP
NATIONAL WEATHER SERVICE INDIANAPOLIS TECHNICAL DISCUSSION
797 .KEY MESSAGES... - Below normal temperatures expected for the foreseeable future. Bitterly cold conditions likely by mid week next week. - WINTER STORM WARNING in effect across much of central IN for a significant winter storm expected to impact the region Sunday - Monday. - WINTER WEATHER ADVISORY in effect for northern portions of central Indiana Sunday into Monday where uncertainty remains in snowfall totals and overall impacts. Today through Tonight... Mundane weather is expected through tonight with surface high pressure remaining dominant across the region. Large scale subsidence will provide mostly clear skies for much of today before clouds begin to increase again late ahead of an approaching winter storm. Dry subsidence induced air in the low levels should keep central Indiana dry. However, some guidance suggest there is a low chance for light snow across far southwestern just before daybreak Sunday due to moisture surging northward. Low end POPs will remain in the forecast for late tonight though much of the wintry precipitation should hold off until during the day Sunday. More details on this upcoming winter storm can be found in the long term forecast discussion below. The main concern for today and tonight will be cold temperatures. An anomalously cold airmass has settled into the region after a cold front moved through yesterday. Temperatures in the teens this morning combined with a slight NW breeze could lead to wind chills near or slightly below zero over north-central Indiana. Areas further south are still going to be cold with single digit wind chills possible. Given negligible thermal advection, temperatures remain below normal through tonight. Look for highs in the 20s this afternoon followed by lows in the teens to low 20s overnight. .LONG TERM (Sunday through Friday)... OVERVIEW - The primary concerns for the long term forecast are twofold. 1) WINTER STORM WARNING across much of central Indiana for a winter storm expected Sunday into Monday, with potential for significant to major impacts, in the form of heavy snow, sleet/ice accumulations, and gusty winds/blowing and drifting. A WINTER WEATHER ADVISORY is in effect for northern portions of central Indiana where uncertainty remains regarding overall impacts. 2) Bitterly cold conditions arriving in the wake of the winter storm, likely persisting well into the week 2 period before improvement. WINTER STORM SUNDAY INTO MONDAY - Overall, forecast thoughts for the winter storm moving in Sunday remain generally the same with impacts expected to last into the start of the work week. Models have continued to trend slightly south with the track of the low pressure system which continues to lower confidence in northern portions of central Indiana receiving significant snowfall. Guidance shows a deepening surface low interacting with an upper trough moving towards the Ohio Valley on Sunday. Anomalous moisture streaming northward within a strong LLJ and increasing dynamics will promote widespread wintry precipitation overspreading the area from SW to NE during the day Sunday. Precipitation is expected to begin across the southwest in the morning before spreading across all of central Indiana by mid-late afternoon. Look for precipitation to begin as all snow with increasing warm air advection within the WCB then leading to sleet or freezing rain mixing in over south-central Indiana late Sunday into Sunday night. Models have remained consistent on timing of the winter storm, but there are still discrepancies regarding the track and evolution of the system which leads to slight differences in how far north sleet or freezing rain mixes in. The slight southward shift suggest sleet may be the more dominant precipitation than freezing rain where a transition occurs. Forecast soundings generally support this showing the warm nose remaining only a degree or two above the 0C isotherm near south-central IN and a sufficient sub-freezing layer beneath the warm nose for sleet. However, some model soundings near far southern counties show the potential for the warm nose to be warmer than 3C. This would make it difficult for re-freezing to occur, likely supporting freezing rain. Thermal profiles further north closer to the I-70 corridor suggest precipitation type remains snow during the winter storm. The strongest large scale ascent and frontogenetical forcing is expected to move across the area late Sunday in tandem with the transition of wintry precipitation. Thus, the heaviest snowfall rates from the system are likely to occur in this period as well. It is worth noting heavy precipitation rates could help limit ice accretion. A transition back to all snow should occur late overnight once colder begins to filter in on the backside of the system. There are still a few models showing the potential for a TROWAL to develop and move through late Sunday night into Monday morning though it appears to weaken as the system progresses eastward. The winter storm will shift east on Monday allowing snow to taper off with drier air filtering in. Models differ on how quickly the system exits, but light accumulations are likely to continue through Monday with some impacts. ******************************************************************* Summary of Winter Storm: The concern for greatest impacts is near and south of the I-70 corridor where a Winter Storm Warning is in effect. Given the slight southward shift, there is still uncertainties in northern portions of central Indiana seeing greater than 4 inches of snow. A Winter Weather Advisory is in effect for these areas, but models could trend back north in the next 24 hours. Greatest snowfall amounts are likely to remain south of the I-70 corridor with widespread amounts around 5-8 inches and locally higher amounts up to 11 inches possible. While snowfall amounts may be lower where freezing rain/sleet mixes in, impacts could still be just as significant. Strong winds are also a concern with 30-35 mph gusts late Sunday into Monday likely resulting in blowing or drifting snow. Strong winds combined with heavy wet snow could lead to power outages. ******************************************************************** BITTER COLD - Guidance strongly suggests the arrival and fairly lengthy persistence of a potent Arctic airmass in the wake of the winter storm. Well below normal temperatures are expected from Tuesday - Wednesday and into the week 2 period, Depending on where the snowpack forms, there is strong potential for subzero low temperatures. Kept both highs and lows below guidance for the rest of the week, nudging temperatures toward the NBM10-25th percentile given the fact that there will be a healthy snowpack. MISCELLANEOUS - Toward the middle of next week and beyond, guidance not only strongly suggests the aforementioned persistence of a potent Arctic airmass, but also the passage of one or more upper level shortwave troughs within the much larger longwave trough/upper low over the eastern Canadian provinces and the northeastern CONUS. While moisture is very often difficult to come by for these waves, cyclonic flow in Arctic airmasses is notorious for producing persistent flurries or light snow showers, and depending upon the orientation of the flow, may allow somewhat more substantial lake enhanced activity to make it down into portions of central Indiana at times. While these more minor snows are far less predictable, particularly several days or more in advance, we are likely to see at least a few periods of light snow across some portions of central Indiana at times toward the end of the forecast period and beyond, despite the official forecast remaining dry for now.





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