Michael's Weather Blog: Arctic Parade

FORECAST DISCUSSION:

After hitting a high of 71ºF this afternoon at Camp Mabry it is time to brace yourselves for some BIG changes. A strong Arctic Cold Front will plunge through south central Texas late tonight into early Wednesday morning. Strong north winds will move in behind the front and allow cold, Arctic air to settle into the region. Highs on Wednesday will struggle to climb into the mid 40s under a mostly sunny sky. The brunt of the cold air moves in late Wednesday into Thursday morning when all of south central Texas will fall into the 20s! Don’t be surprised to see some upper 10s across the Hill Country. Remember the 4 P’s: Plants, pipes, people and pets. A reinforcing Arctic front moves through central Texas early Friday morning keeping highs in the 30s for Friday and Saturday [more info. below]

Strong Arctic High Pressure Cell [a.k.a. SIBERIAN HIGH] will take over a good chunk of the central and Eastern U.S. over the coming days. An Arctic High is simply an incredibly cold and strong built up mass of Arctic Air. This Arctic High will ensure a long stretch of well below normal temperatures not only us here in Texas, but for the majority of the lower 48 east of the Rocky Mountains:

Notice on the map below how tight the black lines [isobars=lines of equal pressure] are on the outer periphery of the center of the high pressure cell which is forecast by the GFS Model to be over the South Dakota and Nebraska Border noon Wednesday. The closer the black lines are to each other, the windier it is! So, just by looking at this map get ready for a WINDY Wednesday!

Just for fun, the image below is an archived image of the same type of map you are looking at above from the December 1989 Historic Arctic Outbreak that brought us a low of 4ºF here in Austin just before Christmas of 1989, it sure is interesting to see just how similar those maps look! I'm not saying we are going to see single digits here in Austin, however, it is incredible to think just how strong this Arctic High moving in over the coming days is going to be: If you are interested in reading up on the December 1989 Arctic Outbreak click HERE.

This chart is a look at official high and low temperatures recorded in Austin during that Arctic Outbreak: Dec. 21st through Dec. 24th 1989

Information from Left to Right:

Date-High-Low-Average Temperature-Departure from normal

Wednesday Night/Thursday Morning Forecast Lows (NAM 4km Model):

As an upper level disturbance approaches from the west Friday and passes over the area on Saturday there is the chance for light rain to develop across the area. Given the cold temperatures in place, freezing rain/drizzle and sleet [ice pellets] are not out of the question for the area late Friday into Saturday. There is still a fair amount of uncertainty with this forecast, however, it is beginning to look like travel may become impacted late Friday into Saturday for areas along and west of I-35. Temperature forecasts will need to be monitored carefully. If the air turns out to be colder than models are currently suggesting, freezing rain may become an issue for all of south central Texas. Please monitor the weather carefully over the coming days and heed all watches/warnings/advisories issued by the National Weather Service.

Day by Day Forecast:

***High and Low temperatures below represent Austin Metro Area***

Tonight: Mostly clear and cool; north winds pickup overnight as Arctic Front moves through; we will wake up to temperatures as cold as the lower 30s across the northwestern Hill Country to as “warm” as the lower 40s across the remainder of the area.

LO: 39ºF

Wednesday: Mainly sunny, WINDY, and MUCH COLDER with highs in the 40s; North winds sustained 15-25 mph with gusts as high as 35-40 mph possible at times. Latest models show us spending a majority of the afternoon in the upper 30s and lower 40s quickly dropping into the 30s area wide by sunset.

HI: 45ºF (Lower 40s north, upper 40s south)

Wednesday Night: Area wide HARD FREEZE with lows in the 20s area wide; upper teens possible across the Hill Country.

LO: 23-25ºF

Thursday: FRIGID START in the 20s (wind chills in the 10s) will give way to a partly sunny & COLD afternoon with highs in the upper 30s and lower 40s across the region

HI: 40ºF [if clouds are heavier we may not make 40ºF]

Thursday Night: Increasing clouds & COLD with lows dipping into the upper 20s and lower 30s area wide; Austin and points south and east may stay just above freezing

LO: 33ºF

Friday: Cloudy & COLD as another reinforcing Arctic front moves in with a 30% chance for afternoon light rain showers; temperatures likely to stay in the mid to upper 30s all day

HI: 39ºF

Friday Night: 50% chance of wintry mix (freezing rain & sleet [ice pellets] possible especially for areas along and west of the I-35 corridor) Temperatures expected to be at/below freezing along and west of I-35 with temperatures possibly remaining 1-2ºF above freezing for areas south and east of Austin

LO: 30º (colder west in the upper 20s)

Saturday: 50% chance of AM freezing rain/sleet mix along and west of I-35; cold rain for southern and eastern areas; otherwise, cloudy and cold with highs in the 30s

HI: 35ºF

GFS Model 18Z Run:

This high resolution model has been persistently showing a rather large area of freezing rain mixed with sleet [ice pellets] over south central Texas beginning late Friday into early Saturday and clearing out by late Saturday afternoon/early evening (PINK ON MAP REPRESENTS THE FORECASTED WINTRY PRECIP & GREEN REPRESENTS A COLD RAIN)