WEEKEND WEATHER FORECAST – EARLY EDITION

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Weekend Weather Update
Saturday will be sunny and chilly. (Cancel the windy conditions.) High temperatures 42-43.

Sunday now looks to have some cloudiness in the morning, then sunny until later in the afternoon, when clouds move in. High 40. Rain, possibly starting with a few flakes of snow, in the evening/night (GFS).

There are differences between the NAM and GFS regarding QPF, but when it rains, nobody really cares if we get 0.10inches of rain or 0.30 inches.

Details from earlier today…

Let me preface this by noting that today was supposed to be cloudy. The models didn’t do too well yesterday.  Let’s see how they do for the weekend.

A frontal system will move through early evening tonight. Only some cloudiness and a low chance of a sprinkle will accompany the front.

Colder air moves in for Saturday. It will be mostly sunny and windy. High 41.

On Sunday, a weak and poorly organized low pressure system moves in later in the day. Sunday starts with some sun, but expect clouds to move in during the late morning.    There are some timing differences with the models with the NAM having some light precip in the afternoon, while the GFS is later, into the evening.

Both the GFS and NAM are similar with QPF values of about 0.12 inches water.   The precipitation will likely fall as rain or possibly rain mixed with snow, as high temperatures are expected to be about 39 and critical temperatures in the upper atmosphere are borderline too warm for snow.

There are enough model differences with this system, that I expect the forecast to change.  Stay tuned.

ABOUT THOSE MULTIPLE STORMS…

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For snow lovers, it looks like there’s disappointment in the forecast. Those several disturbances mentioned to move along the flat jet stream are still coming through, but not with much if any snow.  Here’s the latest–

The Saturday disturbance still looks like it will miss us to our south.

The Sunday evening disturbance looks to be less organized with a mix of rain and maybe some wintery mix.

The Wednesday disturbance currently appears to move slightly to our north, giving us mostly rain.

  • 200 mb flow
    Previous prediction of 200 mb winds

The flat jet usually doesn’t allow much if any development and shape of the jet is now anticyclonic vs cyclonic. Furthermore, it moved from a position to our south (cold for us) to a more northern position which allows warmer air to move in.

 

WEATHER OUTLOOK

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Wednesday Update
Just a quick note that the first of the impulses expected to move along the fast jet stream track will approach on Saturday. It appears that this most likely misses us to our south, according to the ECMWF.

This afternoon’s GFS gives us a light 1 inch accumulation on Saturday, as does the Canadian CMC.

Another impulse moves by Sunday afternoon. The GFS is more aggressive with this second system and gives us a QPF of about 0.30 inches water. The forecast for these systems is low confidence at this time.

from Tuesday..

We’re almost done with the current storm. The “cold air damming” proved to be more persistent than any of the models had forecast; the cold low level temperatures and the mixed precip remained somewhat longer than expected.

We’re continuing in an active weather pattern. The high level wind flow will act as a fast highway for moisture and disturbances to transit across the country–

200 mb flow
200 mb wind flow for the weekend

We’ll be seeing a chance for precipitation almost every 36-48 hours! Note that the track is just to our south.  There are several more chances for snow and mixed precipitation over the next week.   Details are uncertain, but I’m keeping an eye on it.   Stay tuned.

STORM UPDATE

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A quick review.  This has been an interesting storm.  As far as QPF predictions went, the NAM was superior to the GFS,  both with the previous snowfall Sunday night and with last night’s light accumulation.   We didn’t get the 0.35 inches of water forecast by the GFS last night.

Another bias this storm seemed to confirm:  the “off-hour” runs of the GFS and the NAM, (the model runs done at 1AM and 1PM eastern time),  should really be ignored.  They often complicate rather than clarify the forecast.    Some of the back and forth with the forecast could have been avoided by ignoring the off hour models.

The new National Blend of Models  (NBM) also did well, especially with forecasting precipitation type- snow vs sleet vs rain.  (PTYPE).

In my neck of the woods, we had less than 1 inch of mixed precipitation accumulate.  There’s a mix of light snow, rain and a bit of ice pellets right now and that should transition to sleet and rain by about noon.    Temperatures remain near 30 and below just outside of the city and should rise above 32 mid day.

The latest NBM shows a transition to all rain about noon to 1 PM here. (gridpoint- Blue Bell).  Later transition will occur further north and west.

Rain, heavy at times,  continues until after midnight tonight.

Storm Forecasts & Other Things "up in the air".