THE “ATMOSPHERIC RIVER” LOOKS TO CONTINUE WELL INTO NEXT WEEK

The atmospheric river will carry a surge of low pressure into northern California Friday, followed Saturday by a stronger, more widespread surge across most of California that will bring heavy precipitation, including heavy mountain snow. Another low-pressure impulse is expected to bring additional rounds of rain/heavy snow Sunday into Monday. Strong winds along with heavy snow will make travel almost impossible above 5,000 feet in the mountains, and with saturated conditions already in place, state-wide flooding impacts will also continue into next week.


After another potential low pressure hits next Wednesday, there are some indications of a break in the action there the back half of next week.


SATURDAY SET-UP

Upper-level 20,000-ft wind flow pattern and low-level/ surface temp distribution

  • SW #1 (short wave trough#1) moving east into the western Atlantic Ocean – northerly winds on the back side of the trough pull cool air all the way south into Florida
  • SW #2 Riding atmospheric river over eastern Pacific Ocean, pounding California with another wave of heavy rains, snow/strong winds — this short wave will continue east over the Rockies Sunday and trigger low pressure out of the plains producing rain here Monday
  • SW#3 will ride the atmospheric river SE, hitting California with another round of rain/snow/winds Monday
  • Chicago: Cool air shifts east and Chicago settles into into transitional air with temps in the 40s Sunday and 50s/rain Monday

DAYS ARE GETTING LONGER IN CHICAGO, BUT IT’S HARD TO TELL WITH SO MANY CLOUDY DAYS

December was a cloudy month with 17 completely sunless days and January is continuing the mostly cloudy trend with 7 of the first 13 days recording zero sunshine and overall receiving only 20% of possible sunshine (normal is 40% of possible for our two cloudiest months December and January). This has made it harder to notice, but the days are getting longer.


Since the first of the month, days have lengthened by 15 minutes—from 9 hours and 12 minutes to 9 hours and 27 minutes (currently about 1.5 minutes each day) By the end of January our period of daylight will be 10 hours, increasing at a faster rate of 2 minutes and 15 seconds/day.


SUNDAY

Strengthening southerly winds/milder air returns to Chicago

  • Low-level jet stream — SSW winds 25 to 40 mph
  • Warm/mild air pushes north into the Plains; Chicago rests on the eastern edge of the mild air/strong winds

NEXT WEATHER SYSTEM ARRIVES MONDAY, MARTIN LUTHER KING DAY, BRINGING NEXT CHANCE OF RAIN

Rainfall totals through Tuesday, January 17th

0.25 to 0.50″ likely across the Chicago area


FULL DAY TEMPERATURE DEPARTURES FROM NORMAL

Following brief cool-down, temperatures to surge well above normal later this weekend into early next week


CHICAGO’S PRECIPITATION

Next round of wet weather arrives by Monday with periods of rain/perhaps a rumble or two of thunder possible


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