I see whats happening... The first main storm exits towards Great Lakes/Canada tomorrow and another piece of energy dives down (wasn't shown last week).
That energy carrying moisture coming after the polar air plunged south. So that's why we're getting snow dropping south as well. See the 540 thickness!?? Even 534! This is impressive to see on the map beginning of September!
From
Rapid City.
NATIONAL WEATHER SERVICE RAPID CITY SD
316 AM MDT TUE SEP 9 2014
.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT
ISSUED AT 248 AM MDT TUE SEP 9 2014
WATER VAPOR SHOWS DEEP TROF BUILDING INTO THE WRN CONUS WITH UPPER
RIDGE OVER THE CNTRL PLAINS. AT THE SFC...BACKDOOR CDFNT WORKING
SWD THROUGH WRN SD...WITH EVEN COLDER AIR SURGING SWD INTO CNTRL
MT.
TODAY...COLDER AIR WILL CONTINUE TO WORK SWD THROUGH THE CWFA.
TEMPS IN THE NRN HALF OF THE CWFA WILL LIKELY SLOWLY FALL THROUGH
THE DAY GIVEN STRENGTH OF COLD ADVECTION AND WDSPRD LOW STRATUS
BUILDING SWD OUT OF MT/ND.
WEDNESDAY NIGHT...
THERMAL PROFILES
SHOW SNOW LEVELS POTENTIALLY LOWERING ONTO THE PLAINS FROM NERN WY
INTO NWRN SD...WITH SOME ACCUMULATIONS POSSIBLE AT HIGHER
ELEVATIONS OF THE BLKHLS.
.LONG TERM...THURSDAY THROUGH MONDAY
A STRONG UPPER LEVEL TROF WILL CONTINUE TO MOVE
SOUTHEAST THROUGH THE NORTHERN PLAINS ON THURSDAY...BRINGING RAIN
AND HIGHER ELEVATION SNOW TO MOST OF THE REGION. SNOWFALL WILL
MOSTLY BE CONFINED TO NORTHEAST WY...THE BLACK HILLS...AND FAR
NORTHWEST SD...WHERE AT LEAST A LIGHT ACCUMULATION IS
LIKELY...ESPECIALLY IN THE MORNING. SEVERAL INCHES OF ACCUMULATION
IS POSSIBLE OVER THE HIGHER ELEVATIONS OF THE BLACK HILLS. THE
CUTOFF OF RAIN VS SNOW WILL BE CLOSE IN THE RAPID CITY AREA THURSDAY
MORNING. WILL GO WITH A POSSIBLE MIX HERE DURING THE MORNING HOURS.
PRECIPITATION WILL MOVE OUT OF THE AREA FROM NORTHWEST TO SOUTHEAST
THURSDAY NIGHT AS THE TROF MOVES QUICKLY EAST.
TEMPERATURES WILL
DROP TO NEAR OR BELOW FREEZING LATER THURSDAY NIGHT/EARLY FRIDAY
ACROSS MUCH OF NORTHEAST WY AND WESTERN SD...COLDEST WHERE SKIES
CLEAR OUT. A HARD/KILLING FREEZE IS POSSIBLE ACROSS NORTHERN AND
WESTERN PORTIONS OF THE CWA.