Area of surface high pressure that brought us the chilly temps over the weekend behind Saturday morning's windy cold front is now pushing east of the area. Now that we are on the backside (or western side) of this area of high pressure, the clockwise flow around it has allowed light southeasterly winds to return to south central Texas. Over the next couple of days, a trough, or dip in the jet stream aloft over the western United States will help surface pressures to drop across the plains east of the Rocky Mountains. Falling surface pressures to our north will help to increase the southerly flow across Texas. The deepening upper level trough to our west will pull the subtropical jet stream (southwesterly winds aloft) over Texas by the middle to end of the week. This southwesterly wind flow aloft will help to pump in Pacific moisture into the mid and upper levels of our atmosphere. At the same time, upper disturbances, or ripples in the wind flow aloft will help to kickoff on and off showers across the area (beginning as early as Wednesday). Latest forecast model guidance shows a tropical system forming in the eastern Pacific by the middle of the week. The southwesterly wind flow will help to pull some of the moisture from this tropical system over Mexico and into the southern plains. With two sources of moisture in play, heavy rainfall and minor stream and creek flooding may be possible Friday into Saturday.
Forecast 500mb Analysis Thanksgiving Evening (simple map, right?)...big upper level low over Nevada and California (blue shaded area)...reds over western Canada indicating high pressure, that will help to push the cold Canadian Air south into Texas on Friday...the upper level low will send moisture on top of that cold air to produce rain for us!
Quick Weather Points
>>>We officially received our first freeze of the season in Austin this morning. Camp Mabry bottomed out at 32°F this morning. That freeze comes a week ahead of schedule.
>>>The airport set two brand new record lows this weekend; 31°F Sunday morning (previous record: 32°F set back in 2005 & 1964) and 27°F this morning (previous record: 28°F set back in 1975)
>>>The average high and low for this time of year in Austin is 69°F and 48°F...as you can see, we were running well below average this weekend
>>>As of 2 p.m. C.S.T. temperatures are running in the lower to middle 60s across the area under mostly sunny skies...high clouds will be increasing from the west later this afternoon/evening and especially overnight and into the day tomorrow.
>>>With increasing moisture expected across the state of Texas at both the low, mid, and high levels of the atmosphere, we can look for cloudy, balmy, and warm days ahead with highs rebounding into the 70s and lows rebounding significantly into the 60s. What a world of difference a change in wind direction makes this time of year.
>>>No more freezes expected through the end of the week; it will turn colder this weekend, but I think we will stay ABOVE freezing
Thanksgiving Day Forecast:
Cloudy, mild, and muggy with highs in the middle to upper 70s, we will start the day in the mid to upper 60s. There is a 40-50% chance of on and off showers during the day and evening...the heaviest precipitation and possible storms should manage to stay north and west of the area...that changes though late Thursday evening into Friday (see below).
Forecast Highs across the U.S. Thanksgiving Day
Black Friday Cold Front/Rain Chances
As it looks right now, the bulk of the rainfall with this next system looks to come late Thanksgiving into Sunday. A strong surface cold front will be moving across the state of Texas on Friday. This front will have some very chilly air behind it, setting up a large contrast in temperatures across the state. I'm thinking a 20-40 degree difference in temperatures on either side of the front.
>>>Gusty north winds will move in behind the front. Temperatures will drop from the 60s and 70s ahead of the front into the 40s and 50s in a short amount of time.
>>>The GFS Forecast Model is indicating that once the cold front passes through the area, it will stall, or really slow down just to our south and east and may in fact end up stalling near the Texas Coast. That would mean a 20-30 degree temperature difference between Austin and Houston on Saturday. We will have to wait and see what future model output shows.
GFS Surface Temperature Forecast (noon Friday)
There will be a 40-60 degree temperature difference across the state! You don't have to be a meteorologist to find the front on this map!
Potential Cold Heavy Rainfall Setup:
>>>As the front pushes into the area during the day on Friday, numerous to widespread showers and even some heavier downpours with embedded thunderstorms are likely to develop and persist through the day on Saturday as warm, moist Gulf air is forced to overrun, or move up and over the cold Canadian air at the surface. Combine that overrunning Gulf air with Pacific moisture streaming into the state and heavy rainfall may become an issue across south central Texas. As of right now, forecast models are showing the really heavy rains staying north and east of our area, but that could change.
>>>Temperatures on Saturday likely to stay in the 40s all day with rain falling.
How much rain are we talking?
Latest forecast model guidance indicating a widespread 1-3 inches of rain possible across the area between now and Sunday evening...some locations may receive more than that (especially north and east of the area, as it looks right now where upwards of 3-5 inches of rain may fall)...there is still plenty of time to watch forecast rainfall accumulation
Wintry Precipitation?
>>>In my last blog I mentioned a threat for wintry precipitation across the area this coming weekend. Based on the latest forecast model guidance, freezing temperatures should stay well north of south central Texas...it looks like the majority of the wintry precipitation will fall in the Texas Panhandle. Portions of the Panhandle could get a very heavy snowfall by the weekend...check out the forecast accumulated snowfall map (this is just a forecast).
***Please know and understand that this is just a forecast...specifics may change over the coming days...remember to heed all watches/warnings/advisories issued by the National Weather Service***
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