Monthly Archives: February 2019

Winter Storm Outlook

WINTER WEATHER UPDATE -TUESDAY

[su_box title=”Winter Weather Update: Tuesday 8 PM” box_color=”#defcdc” title_color=”#000000″]A quick review of the today’s models. We’re back to 4-5 inches of snow, changing to sleet about 5 pm. Tonight’s NAM data starts becoming available after 9 pm and I’ll update sometime after 9:40. [/su_box]

[su_box title=”Winter Weather Update: Tues 9:30 AM” box_color=”#defcdc” title_color=”#000000″]A change in the forecast, based on the latest NAM. Precipitation starts about 10 AM, earlier to the west and southwest. Snow until about 4-5 PM, then a changeover to sleet and then some freezing rain.

The revision in the forecast- most of the QPF will be arriving after the changeover to sleet.. about 3 inches of snow expected, more north and especially west, before a changeover to an extended period of heavy sleet and sleet mixed with rain, then rain.

I’ll be updating this evening. Likely update time is around 9:30 PM.[/su_box]

I’m waiting for the latest NAM data.  Last night’s NAM and GFS moved the precipitation start time later to 10-11 AM (with the exception of the FV3-GFS which still maintains an earlier start.)

NAM QPF values for the morning and afternoon increased to 0.80 inches water, but some of that will be falling as sleet.   The NAM maintains freezing temperatures into the evening.  At the current time, I’m still with 4-6 inches, leaning towards the higher amount, before a changeover to an extended period of sleet.   Snowfall will be heavy in the early afternoon.

I’ll  be updating with the NAM data this morning, before 10 AM.

A very busy schedule at work today, so I probably won’t get a chance to further update until this evening.  (It will be this evening’s data that will be most important.)

Winter Weather

WINTER WEATHER UPDATE -MON 6 PM

[su_box title=”Winter Weather Update: Monday Evening ” box_color=”#defcdc” title_color=”#000000″]Tonight’s NAM has become available. The NAM has snow starting about 9-10 AM Wednesday and continues as snow until 4-6 pm, when it starts mixing and changing to all sleet by 7pm. Temperatures remain at or below freezing until early evening.

Based on QPF, 4-6 inches of snow may accumulate before the changeover. A further changeover to rain will occur later in the evening. Heavier rain about midnight.

This is a preliminary forecast. Expect changes with future model runs.  [/su_box]

From earlier..

Here’s the latest on the snow that’s expected for Wednesday.  As usual, there’s a fair amount of model disagreement.

This morning’s GFS had the snow starting as late as noon, however this morning’s run of the new FV3-GFS had the snow starting about 8 AM.   This afternoon’s high resolution NAM NEST has the snow starting about 10 AM.

This will be a storm where the total QPF will be divided into snow, sleet and rain components.  Most of the models are in general agreement that there will be about 3-6 inches of snow, with a lean towards the lower end, before a changeover to sleet and then eventually to rain.  BTW, the European (ECMWF) has 4-6 inches for our area.

Models have the changeover from snow to sleet anytime from 3PM to 7 PM.   Sleet will likely fall for several hours as it mixes with rain. The heaviest precip will occur as rain towards midnight and after.

As discussed earlier, this will be another “warm air aloft over-runnng cold air at the surface” type system, actually a warm frontal-type system.

The forecast accuracy for this type of system has little to do with the “track of the storm” as they say on TV, but rather with the three dimensional thermal profile of the atmosphere and the eventual placement of the moisture plumes and dynamics.   There’s no storm center “to track” here; it’s more subtle than that.

Getting the forecast even close to correct probably won’t be possible until Tuesday night’s model runs.