Oh No! It’s Happening Again

Over and over again the past 6 weeks we’ve seen models attempt to develop upper level ridging (even if only briefly) over the West Coast of North America, only to see subsequent model runs squash it down and bring new, cool, upper-level troughs closer to the coastline than originally anticipated.  It’s as if long range models keep attempting to revert to “normal” summertime conditions, but then “clue in” to the persistent cool West and hot mid-USA pattern that has not changed (significantly) since late last winter.

Well…it happened again the past 24 hours.  Yesterday we had a 7 day forecast that showed mainly clear skies and temps around 80 or so both days this weekend.  Now the ECMWF model is rushing an upper level trough right into the Pacific Northwest SATURDAY AFTERNOON!  That would mean clouds and showers late Saturday and into Sunday.  A 2nd wet weekend in the middle of July.  We get 2 runs of that model every day (a new one every 12 hours).  Now the GFS model comes in every 6 hours and has gradually moved towards the ECMWF the past day or so.  It has showers coming in Sunday evening or night with yucky/showery weather Monday.   Here at FOX12 we haven’t gone “whole hog ECMWF”, but the threat is there:

We could see showers as soon as Saturday evening, definitely by Monday, so likely only 1-2 days of noticeably warmer and drier weather at the end of the week (Friday and Saturday).  We may have to move the showers into Sunday as well; that 7 Day may yet go downhill further.

Believe me, I’m just as annoyed by the changing forecast as everyone else.  Many people make plans (months ahead of time) for the almost guaranteed dry weekends in later July and August.  At least we’re catching it 5-6 days ahead of time, much better than a Thursday or Friday change to a weekend forecast.

Chief Meteorologist Mark Nelsen

112 Responses to Oh No! It’s Happening Again

  1. hemp says:

    ..Snow Hope Index.Ok I promised a new blog so here it is. I thought about waiting for the morning models to come in but I didnt want to wait that long. Theres my latest snow hope index. Its at a 7. Odds are that this will go down tomorrow and then back up on Friday but well see. Heres the latest thinking about this system .The Basic An area of low pressure will move up from the Deep South Friday into Saturday. It will butt-up against some very cold air coming out of Canada on Friday. Snow showers in Central Virginia are a good bet. There is a chance for accumulating snow in the metro hence the snow hope but there is also a possible rain snow mix in the forecast for a period. Scattered snow showers are expected late Friday night while the whole atmosphere moistens up from top to bottom. Then the mix would come in to some part of the viewing area early Saturday. As the low moves offshore Saturday the cold air will push back south and snow showers will take over. Then the upper level low comes into play and can make for some light snow showers Saturay afternoon evening. Heres the latest forecast that I put together regarding the low pressure area at the surface .Weekend Weather.This forecast track can easily change. Ill discuss some of the computer model trends below. Warningit will be detailed. I will mention some cities in here but they are more for cutoff points rather than specific forecasts. I can do more city by city when we get closer to the event. .The models detailed I first looked at the Canadian model. It has some light snow arriving late Friday night through a good portion of the area. Very light stuff though. Then Saturday morning it shows heavy snow near the Virginia North Carolina Border. It looks like a mix from Virginia Beach Southward. Saturday afternoon evening the low moves offshore and we get some moderate snow inland with a possible rain snow mix in the metro. Rain sleet for the Outer Banks at that time. We dry out later that night. .The overnight run of the GFS model has some rain sleet snow in North Carolina Friday night with virga over Virginia. It has the light snow coming in overnight with a rain snow mix over northeast North Carolina. Light snow in the metro and heavy snow in Central Virginia. At that time the low is over South Alabama and stretches over to South Carolina. By Saturday morning it looks like a mix in the metro southward with heavy snow from about Suffolk northward. It would probably be the heavy wet variety but thats a guess. By the afternoon the GFS has some moderate to heavy snow in the metro and north and west of here. The low then stretches from Florida up to just offshore of the Outer Banks. The upper level low then takes the baton and produces some light snow Saturday afternoon evening as the surface low moves away. Here s the place that I go to look at the GFS and NAM models. Its . .To me the European model looks further south and is more upper level dependent. It looks like less snow from the most recent model run but maybe Im not looking at a good source. Heres the link that I use .. update I just checked the morning run of the Navy model. It is the driest of the models with most of the mixed precip across North Carolina. It is not very impressive but it still advertises some light snow overall..The morning run of the NAM is coming in now. Whoa! It shows dry conditions Friday night and overnight but then it gets interesting. Saturday morning it has heavy snow over North Carolina with light snow in the metro. The surface low over South Georgia at that time. By Saturday afternoon we could see a rain snow mix in the metro and in northeast North Carolina. But it suggests heavy snow from the metro northward and in central Virginia. The low stretching from Georgia to the southern Outer Banks at that time. By the evening everybody would see moderate to heavy snow showers as the low moves offshore. This looks a little supicious though as most of the moisture would come on the backside of the low at that point. Its not out of the question but it does look overdone. The upper level low would be coming into play at that time. Wed get the 500mb PVA upper level spin coming into play then too. If this model verifies then we will be in trouble as well have to measure the snow with a yard stick. .My 2 cents So heres my latest thinking based off of what Ive seen so far. Well probably start off with some light snow showers very late Friday early Saturday. This will turn into a mix in part of the metro Saturday morning as the low gets closer. Then as the low moves away the winds go more northeast and the cold air pushes down. Then we have a chance for snow showers even in the metro. The upper level low may produce a few light snow showers Saturday afternoon evening but it will be on the light side. This is also when snow may push as far south as the Albemarle. Some things that could impede snow in the area If the low strengthens before it moves offshore then it could throw some more warm air up this way. That could push the rain snow line a little further north. Its also possible that the low could move further south and then offshore. That could reduce the snow amounts significantly as most of the moisture would be further south. But it would also mean that the cold air is in place and then anything that fell would be snow. Things are getting interesting but I am not going to get too excited yet.

  2. I don’t mind cool but sun is important since I have a garden and fruits and vegetables need sun to grow.

  3. pappoose in scappoose says:

    A shift in the weather?

    National Weather Service Portland or
    903 PM PDT Thursday Jul 21 2011

    Recent model runs are beginning to lean toward a slightly more zonal flow over the Pacific northwest toward the end of next week versus the continual trough that has plagued the area so far this Summer. It offers some hope that there may be a shift in the weather – though at this early stage in the forecast it is unwise to put much stock in the change…but one can be hopeful. Kelson

  4. An evil day. A high of 66.6. 8th day with a high below 70.

    The NW wind is blowing decently this evening, and I have a feeling it may drop into the 40s tonight.

  5. Gresham Rocks says:

    Hope that 7 day forecast is not true, you winter really came early!!!!!

    • Gresham Rocks says:

      Oops misspelled a word “OR” winter really came early

    • snodaze says:

      But if you were looking at a calendar, had it opened to November and were shaking your finger at it while saying what you said. It wouldn’t really be misspelled.

      “you winter really came early, you”!!! 🙂

  6. Joshua in Lake Oswego says:

    Historic summer cold snap coming up for the next week!!!


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