The M-4 Forecasts

When will the low pressure area depart? If it leaves too late, we'll have strong north winds and the chance of rain Marathon morning. If it leaves too early, we could see warmer temperatures and more humidity and possibly strong Gulf winds. Despite this uncertainty, the forecasts have been surprisingly consistent (and consistently favorable). Today's NWS discussion:

YESTERDAY CONDITIONS WARMED UP NICELY WITH MAX TEMPS IN THE LOW 60S FOR MOST AREAS ACROSS SE TX. IT IS POSSIBLE TO HAVE TEMPS IN THE LOW 60S ONCE MORE BUT THIS WILL LARGELY HINGE ON THE AMOUNT OF CLOUD COVER DURING THE DAY. THE 00Z 500MB ANALYSIS SHOWS A BROAD UPPER LEVEL LOW OVER OLD MEXICO AND IS PUSHING INTO THE RIO GRANDE VALLEY AND S TX THIS MORNING. THE MAIN IMPACTS FROM THIS LOW FOR SE TX WILL BE INCREASED LOW/MID CLOUD COVER BUT THERE MAY BE ENOUGH BREAKS IN THE CLOUDS FOR DECENT HEATING. WINDS WILL ALSO TURN TO THE SE WHICH WILL AID HEATING. THIS UPPER LOW SHOULD WEAKEN AS IT SWINGS OFF TO THE NE OVER TX AS THE NEXT DEVELOPING TROUGH DIGS OVER THE DESERT SW AND NW MEXICO. THIS NEXT TROUGH WILL BE THE MAIN WEATHER MAKER FOR THE END OF THE WEEK.
WATER VAPOR IMAGERY AND 500MB ANALYSIS SHOW THIS NEXT TROUGH BEGINNING TO TAKE SHAPE OFF THE COAST OF CALIFORNIA. A STRONG JET STREAK SHOULD PUNCH INTO THE BACK OF THE TROUGH WHICH WILL CAUSE IT TO DROP SOUTHWARD. THE TROUGH AND UPPER LOW SHOULD TAKE SHAPE THU NIGHT AND THEN BEGIN TO SHIFT EAST OUT OF C MEXICO INTO S TX. THU AND THU NIGHT SHOULD SEE THE BEGINNING OF STRONG WARM ADVECTION AND ISENTROPIC LIFT. THERE MAY BE SOME ISO THUNDERSTORMS BUT SUSPECT MOST OF THE ACTIVITY WILL BE MODERATE RAINFALL FROM SHOWERS. ONCE AGAIN THE 00Z ECMWF SEEMS TO BE THE MORE CONSISTENT OF THE MODELS WITH ITS EVOLUTION OF THE COASTAL LOW THAT DEVELOPS FRI MORNING. THE DETAILS OF HOW THIS COASTAL LOW EVOLVES ARE STILL HARD TO PIN DOWN BUT SUSPECT THAT THERE MAY IN FACT BE MULTIPLE SFC LOWS DEPENDING ON WHERE ORGANIZED CONVECTION DEVELOPS IN THE GULF. REGARDLESS...THERE SHOULD BE QUITE STRONG EASTERLY FLOW OVER THE COASTAL WATERS OF THE UPPER TX COAST WHICH PERSIST FOR A GOOD 12 TO 24 HRS. ELEVATED TIDES WILL BE POSSIBLE SO COASTAL FLOOD STATEMENTS MAY BE NEEDED FOR FRIDAY. THE COASTAL LOW SHOULD TRACK EAST ACROSS THE N GULF INTO THE MISS RIVER DELTA LATE SATURDAY. THIS MEANS THAT THE BULK OF THE PRECIP...GENERALLY STILL 1 TO 3 INCHES... WILL FALL ON FRI FOR SE TX. THE HIGHER RAINFALL AMOUNTS WILL LIKELY BE CONFINED TO THE SOUTHERN HALF OF THE FORECAST AREA. POPS WERE TRIMMED DOWN SOME FOR SOME OF THE NORTHERN AREAS OF SE TX BUT STILL KEPT 80 POPS FOR WHERE HEAVY RAINFALL IS EXPECTED FOR THE SOUTHERN 2/3`S OF SE TX. AT THIS TIME IT STILL LOOKS LIKE MUCH OF THE AREA CAN HANDLE 1 TO 3 INCHES OF RAINFALL WITH OUT ANY FLOODING PROBLEMS. THE UPPER LOW WILL TRACK EAST A LITTLE BE BEHIND THE SFC LOW BUT SHOULD CLEAR THE REGION SAT NIGHT. THIS SHOULD BRING AN END TO ANY PRECIP CHANCES AS THERE MAY BE SOME WRAP AROUND RAIN DURING THE DAY SATURDAY. POPS WERE TRIMMED TO FINE TUNE THE TIMING OF WHEN PRECIP WILL COME TO AN END ACROSS THE AREA SATURDAY.

SUN AND MON NEXT WEEK LOOK TO BE DRY AND COULD BE A TAD WARMER THAN PREVIOUSLY THOUGHT. THE GFS HAS TRENDED WARMER SO THE FORECAST HAS BEEN ADJUSTED TO ACCOUNT FOR SLIGHTLY WARMER TEMPS. THE ECMWF SEEMS TO AGREE WITH THIS MAINLY DUE TO LOW LEVEL FLOW INCREASING FROM THE SW ESPECIALLY AT 850MB. LOOKS LIKE MOISTURE WILL BE ON THE RETURN MON/TUE NEXT WEEK WITH SLIGHT RAIN CHANCES WITH WARM ADVECTION. SE TX MAY HAVE 3 DAYS IN A ROW OF ABOVE NORMAL TEMPERATURES FOR MON/TUE/WED.

Here's the NWS hourly projection for Marathon Sunday. The NWS projects 41°F at the start and 50°F at 10AM, with the dewpoint in the 30s. That's warmer, but still very nice for running. They have a WNW wind at 6 mph to a W wind at 7 mph and partly cloudy with sky cover at 20%.


The 7.5-day model includes marathon morning. This model follows right along with the NWS hourly projection [the graph is in UTC, six hours ahead of Houston]. The text version of the MRF model. shows a low of 41°F and winds at 14mph in the morning.




The Weather Channel tends to weight their long term predictions with seasonal averages. For Saturday night they show:
Overnight Low 41°F
Precip 50%
Wind: NW 6 mph
Max. Humidity: 87%
Showers


For Sunday they show:
High 62°F
Precip 0%
Wind: WSW 3 mph
Max. Humidity: 74%
UV Index: 4 Moderate
Sunrise: 7:17 AM CT
Sunny


AccuWeather has Saturday night and Sunday their detailed forecasts. They predict:

Saturday Night, Jan 16
Low: 41 °F RealFeel®: 37 °F
Winds W at 9 mph with gusts to 16 mph
Mainly clear

Sunday, Jan 17
High: 60°F RealFeel®: 61°F
Winds SSW at 8 mph with gusts to 16 mph
Partly sunny