...Expected Local Impacts by Category...
Transportation: Widespread
Power: Scattered
Tree Damage: Isolated
Impact categories and definitions:
Isolated: less than 25 percent of the category may be impacted
Scattered: 25-40 percent of the category may be impacted
Regional: 40-60 percent of the category may be impacted
Widespread: greater than 60 percent of the category may be impacted
...Overview and Timing...
We continue to forecast that significant impacts from a combination of ice, sleet and/or snow are likely across the entire area on Tuesday. This will not be the "typical" event for the local area for two reasons: (1). The precipitation will occur over a broad time period throughout the day on Tuesday, rather than just a brief period early in the morning and (2). Accumulation amounts, particularly of sleet and/or snow, are likely to be higher than we normally see with local winter weather events.
Periods of light rain will mix with and then change to a mixture of sleet, freezing rain and possibly light snow by around 4-5am on Tuesday morning. Northern parts of the area will see the change first, followed by Southern areas last. Please note that it may take 1-2 hours for ice accumulation to begin after the wintry precipitation has begun, and elevated roadways are likely to see accumulation begin first. Present indications suggest that the wintry mix will then increase into the morning hours.
Temperatures are expected to fall to around freezing by around 4am on Tuesday, and continue to slowly fall into the remainder of the daytime hours. After about 10am, readings will mainly be in the middle to upper 20s throughout the remainder of the day. As temperatures continue to fall during the morning hours, the mixed precipitation that is expected from 4 or 5am through about 10am will change mostly to sleet and/or light snow during the mid to late morning hours and continue into the afternoon hours.
...Ice Accumulation Forecast...
Ice accumulation of up to 0.1 inch is expected with this event, most of which will likely occur from around 5-6am through about 10am. If more sleet begins to mix in with the precipitation toward mid-morning, then this amount could be lower in some parts of the area. On the other hand, if less sleet mixes in by mid-morning, then the ice amounts could be slightly higher in some parts of the area.
Ice accumulation of up to 0.1 inch would mainly form a light glaze on exposed surfaces, especially metallic surfaces, colder elevated surfaces such as bridges, overpasses, etc., (especially if they are untreated), and roadways that are lesser traveled and/or untreated. Tree limbs and exposed power lines may also start to see a light glaze-over especially if the near 0.1 inch ice amounts are realized.
...Sleet and/or Snow Accumulation Forecast...
A combined sleet/snow accumulation of up to 1.0 inch is expected with this event. This would most likely occur from around or shortly after 10am through about 4-5pm on Tuesday, with decreasing amounts into the late afternoon and early evening hours. If the glaze ice accumulation occurs as expected (see above), the sleet and/or snow would be able to accumulate on most any exposed surface that has a glaze of ice, including many roadways, and especially those that are untreated.
...Transportation Impacts - Widespread...
Transportation impacts are likely to reach "widespread" status across the local area with this event. Impacts will begin on Tuesday morning and increase throughout the day. Elevated surfaces such as bridges and overpasses would likely be impacted first, followed by the lesser traveled/untreated surface roadways and then other roadways depending upon the extent of the heavier precipitation, amount of traffic on the roads, and the type of treatment the roads are receiving (if any). Please also note that although accumulating winter precipitation will end by late on Tuesday afternoon, temperatures will remain well below freezing into Tuesday night and much of Wednesday. Unless direct treatment of the roadways is applied, many of them (particularly those less traveled) will remain icy well after the precipitation has ended.
...Power Impacts - Scattered...
Power impacts are expected to reach "scattered" status across the local area with this event. Areas with exposed power lines would be most vulnerable, and especially if any concentrated spots of even slightly more than 0.1 inch ice accumulation are observed in those areas. North winds will gust 25-35 mph throughout much of the day on Tuesday, and this could aggravate the condition at times in at least parts of the area, especially where the higher end of the ice accumulation occurs and where there is more open exposure to a Northerly wind.
...Impacts on Trees - Isolated...
Impacts on trees are expected to reach "isolated' status across the local area with this event. Ice glazing of up to 0.1 inch does not typically cause significant issues with downing of tree limbs, so this would primarily be of concern in any areas that may receive slightly more than 0.1 inch of glaze, and on any trees that were in poor condition to begin with. North winds will gust 25-35 mph throughout much of the day on Tuesday, and this could aggravate the condition at times in at least parts of the area, especially where the higher end of the ice accumulation occurs and where there is more open exposure to a Northerly wind.
...What are the Main Areas of Uncertainty?...
With most winter weather events across the local area, the usual area of uncertainty is whether or not temperatures will reach freezing, allowing the precipitation to turn into ice, sleet or snow. We will not have this issue in this case, as temperatures will definitely reach freezing, and fall a considerable degree below freezing as well on Tuesday morning. The main question in this case then becomes the precipitation type. If temperatures get colder faster than expected, we'd have more sleet and/or snow and less ice glazing. Neither scenario is a "good" one, with possibly the only exception being we would potentially see less impact from scattered power outages if we have less ice and more sleet/snow. In either case, transportation impacts will be high, so there seems little reason to split hairs on precipitation type at this time. The only other variable with some amount of uncertainty in this case has to do with the timing of the ending of the precipitation. In general, the precipitation will likely decrease in coverage and/or intensity during the afternoon hours. Whether or not this decrease is gradual or abrupt, it would be during the afternoon hours, not the morning hours. Therefore, we won't be dealing with the usual situation of an "early morning only" type event like we typically see in our area.
...Other Impacts...
Please note that in addition to hazardous conditions that are expected as a result of wintry precipitation, cold temperatures and bitter cold Wind Chills will also create additional hazards throughout this period and extending into Wednesday as well as portions of Thursday.
We will continue monitoring the situation and issue updates as conditions warrant.
Transportation: Widespread
Power: Scattered
Tree Damage: Isolated
Impact categories and definitions:
Isolated: less than 25 percent of the category may be impacted
Scattered: 25-40 percent of the category may be impacted
Regional: 40-60 percent of the category may be impacted
Widespread: greater than 60 percent of the category may be impacted
...Overview and Timing...
We continue to forecast that significant impacts from a combination of ice, sleet and/or snow are likely across the entire area on Tuesday. This will not be the "typical" event for the local area for two reasons: (1). The precipitation will occur over a broad time period throughout the day on Tuesday, rather than just a brief period early in the morning and (2). Accumulation amounts, particularly of sleet and/or snow, are likely to be higher than we normally see with local winter weather events.
Periods of light rain will mix with and then change to a mixture of sleet, freezing rain and possibly light snow by around 4-5am on Tuesday morning. Northern parts of the area will see the change first, followed by Southern areas last. Please note that it may take 1-2 hours for ice accumulation to begin after the wintry precipitation has begun, and elevated roadways are likely to see accumulation begin first. Present indications suggest that the wintry mix will then increase into the morning hours.
Temperatures are expected to fall to around freezing by around 4am on Tuesday, and continue to slowly fall into the remainder of the daytime hours. After about 10am, readings will mainly be in the middle to upper 20s throughout the remainder of the day. As temperatures continue to fall during the morning hours, the mixed precipitation that is expected from 4 or 5am through about 10am will change mostly to sleet and/or light snow during the mid to late morning hours and continue into the afternoon hours.
...Ice Accumulation Forecast...
Ice accumulation of up to 0.1 inch is expected with this event, most of which will likely occur from around 5-6am through about 10am. If more sleet begins to mix in with the precipitation toward mid-morning, then this amount could be lower in some parts of the area. On the other hand, if less sleet mixes in by mid-morning, then the ice amounts could be slightly higher in some parts of the area.
Ice accumulation of up to 0.1 inch would mainly form a light glaze on exposed surfaces, especially metallic surfaces, colder elevated surfaces such as bridges, overpasses, etc., (especially if they are untreated), and roadways that are lesser traveled and/or untreated. Tree limbs and exposed power lines may also start to see a light glaze-over especially if the near 0.1 inch ice amounts are realized.
...Sleet and/or Snow Accumulation Forecast...
A combined sleet/snow accumulation of up to 1.0 inch is expected with this event. This would most likely occur from around or shortly after 10am through about 4-5pm on Tuesday, with decreasing amounts into the late afternoon and early evening hours. If the glaze ice accumulation occurs as expected (see above), the sleet and/or snow would be able to accumulate on most any exposed surface that has a glaze of ice, including many roadways, and especially those that are untreated.
...Transportation Impacts - Widespread...
Transportation impacts are likely to reach "widespread" status across the local area with this event. Impacts will begin on Tuesday morning and increase throughout the day. Elevated surfaces such as bridges and overpasses would likely be impacted first, followed by the lesser traveled/untreated surface roadways and then other roadways depending upon the extent of the heavier precipitation, amount of traffic on the roads, and the type of treatment the roads are receiving (if any). Please also note that although accumulating winter precipitation will end by late on Tuesday afternoon, temperatures will remain well below freezing into Tuesday night and much of Wednesday. Unless direct treatment of the roadways is applied, many of them (particularly those less traveled) will remain icy well after the precipitation has ended.
...Power Impacts - Scattered...
Power impacts are expected to reach "scattered" status across the local area with this event. Areas with exposed power lines would be most vulnerable, and especially if any concentrated spots of even slightly more than 0.1 inch ice accumulation are observed in those areas. North winds will gust 25-35 mph throughout much of the day on Tuesday, and this could aggravate the condition at times in at least parts of the area, especially where the higher end of the ice accumulation occurs and where there is more open exposure to a Northerly wind.
...Impacts on Trees - Isolated...
Impacts on trees are expected to reach "isolated' status across the local area with this event. Ice glazing of up to 0.1 inch does not typically cause significant issues with downing of tree limbs, so this would primarily be of concern in any areas that may receive slightly more than 0.1 inch of glaze, and on any trees that were in poor condition to begin with. North winds will gust 25-35 mph throughout much of the day on Tuesday, and this could aggravate the condition at times in at least parts of the area, especially where the higher end of the ice accumulation occurs and where there is more open exposure to a Northerly wind.
...What are the Main Areas of Uncertainty?...
With most winter weather events across the local area, the usual area of uncertainty is whether or not temperatures will reach freezing, allowing the precipitation to turn into ice, sleet or snow. We will not have this issue in this case, as temperatures will definitely reach freezing, and fall a considerable degree below freezing as well on Tuesday morning. The main question in this case then becomes the precipitation type. If temperatures get colder faster than expected, we'd have more sleet and/or snow and less ice glazing. Neither scenario is a "good" one, with possibly the only exception being we would potentially see less impact from scattered power outages if we have less ice and more sleet/snow. In either case, transportation impacts will be high, so there seems little reason to split hairs on precipitation type at this time. The only other variable with some amount of uncertainty in this case has to do with the timing of the ending of the precipitation. In general, the precipitation will likely decrease in coverage and/or intensity during the afternoon hours. Whether or not this decrease is gradual or abrupt, it would be during the afternoon hours, not the morning hours. Therefore, we won't be dealing with the usual situation of an "early morning only" type event like we typically see in our area.
...Other Impacts...
Please note that in addition to hazardous conditions that are expected as a result of wintry precipitation, cold temperatures and bitter cold Wind Chills will also create additional hazards throughout this period and extending into Wednesday as well as portions of Thursday.
We will continue monitoring the situation and issue updates as conditions warrant.
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