One Day "Heat Wave" Followed by a Week of Dry Weather

 If you have an umbrella, put it away...you won't need it for a while.

 Find your sunglasses...you will need them.  

A major mid-winter break from the rain and murk has now begun...and tomorrow, Tuesday, will be the warmest day of the period.   Some locations will even get to 60°F, but perhaps not where you would expect it.

Consider the forecast surface air temperature at 2 PM tomorrow over Washington--close to the time of warmest temperatures in winter (shown below).

Western Washington is warm, with some locations reaching the upper 50s...and some lucky folks into the lower 60s.

Since such warmth is so attractive this time of the year, here is a close-up map at the same time.  Head north and east of Seattle!

I know what you are wondering.  Can you trust this forecast?  

Good question...particularly after the disastrous forecasts of a big windstorm last week.  As I have discussed before, we need to consider the multiple predictions using ensemble systems, and the UW has one of the best.

Here is the prediction of the many forecasts of the UW system for Seattle.  Nearly all are on board for the warmth.   You can bank on this one-day wonder.

We will cool off after tomorrow, but persistent upper-level high pressure will move in, with at least a week of totally dry weather.  To show this, below is the ensemble of many forecasts of precipitation in Seattle from the NOAA/NWS GFS model.

Precipitation is flatlined at least through January 20.  Other forecast systems are doing the same thing.

Interestingly, long-term climatology shows that amid-month drying is not unusual.  To illustrate, here is the climatological probability of receiving at least 0.10 inches at SeaTac in a day.  You will see a drop in mid-January.

But don't worry, extended model forecasts show the precipitation coming back.   

And if I were irresponsible, I would show the forecast total snowfall by the end of the month.

A forecast that shows lots of snow over the western lowlands.  It would get lots of clicks and attention.   

This is the graphic I am not going to talk about, so please don't look at it and don't talk about it on social media. 😁

Super Ridge of High Pressure Will Bring Dry Conditions and Warmth

 Tired of the rain and cool temperatures?   A major change is about to occur:  the development of a "Super Ridge" of high pressure aloft over the northeastern Pacific.

This "Super Ridge" will bring a short period of spring-like warmth to some lucky folks in our region.

I am going to show you a series of forecast upper-level weather charts that describe the situation around 18,000 ft (heights of the 500 hPa pressure surface above sea level will be shown).   You can think of these figures as describing the pressure variation at 18,000 ft.  The colors indicate the difference from normal (red--above normal, blue--below normal).

Today, at  4 PM, the ridge of high pressure is found just inland from the West Coast, but with low pressure offshore.  Since sinking air and dry weather are found under and east of such high pressure aloft, we arestill  open to Pacific moisture that will push in later today and Thursday.

In fact, the latest weather radar image shows an approaching system lurking offshore.

But high pressure is not done with us!   By Tuesday at 4 PM, another high-pressure ridge builds over our region (see below).

This high pressure will be associated with warming air aloft and its surface reflection to the east will result in easterly flow over the Cascades, with downslope warming over the western slopes of the Cascades.  To show this, below is the predicted surface temperature map for 3 PM on Tuesday.  

Wow.  Temperatures will rise to around 60°F on the western slopes!

Even locations away from the slopes will be warmed...just not as much.  For example, the European Center model predicts a temperature of 59°F on Tuesday (see below).  That will feel very nice.

But this is only a taste of the upcoming Super Ridging.  By Friday morning, an absolutely extraordinary ridge/high-pressure area will form to our north (see below).  This pattern produces absolutely dry conditions over our region.

I have some confidence in this projection because all the major weather modeling systems are forecasting something like it.   

Want a sample?  

Here is the 72-hour total precipitation ending Sunday at 4 PM.  NO PRECIPITATION ANYWHERE.

I hope those pushing a drought narrative will wait before ringing the alarm bells.

Models forecast precipitation the following week, and the extended forecasts are for wetter than normal conditions over the next three months (see the European Center prediction below).

Even the Drought-loving U.S. Drought Monitor has backed off the drought alarms (see their latest graphic below), with drought gone over western Washington and "severe" drought only over the far southeastern side of the State.

Super Ridge