Good morning! Looks like Mother Nature felt sorry for a lot of people and decided to give you a taste of winter! Congratulations! Granted, it wouldn't be the same for everyone, but it's a start in the right direction and just goes to show you that it ain't over 'till it's over.
The Winter Storm Watch has been changed to a Winter Weather Advisory. Keith Spellman, the meteorologist in charge at the Atlanta NWS office explained why they decided to go with an Advisory...
"Tell-tale sign is the near 0 dew points across North GA as late as Tuesday evening. From past experience, dew points near 0 within 18-24 hours of precip is a good indicator of wintry precip since wet bulbing will significantly contribute to layer cooling."
Looking at the GFS, it appears that the precip begins in the northwest corner of the state and starts falling in below freezing temperatures. See image #1. 925 and 850 mb (~2500 and ~5000 feet, images 2 and 3) aren't particularly cold, but low dew points are very low (image 4) at the onset.
This looks like a freezing rain event as much as anything. Where the dew points are the lowest, I see more snow.
More to come on this as I go over the other models, the Euro is very similar.
.SHORT TERM /TODAY THROUGH WEDNESDAY/...
...CHALLENGING SHORT TERM FORECAST WITH FIRST BIG CHANCE AT WINTRY
SHORT TERM PERIOD BEGINS WITH FRIGID TEMPERATURES THIS
MORNING... COMBINING WITH WINDS...TO PRODUCE EXTREMELY COLD WIND
CHILLS ACROSS THE NORTHEAST GEORGIA MOUNTAINS. HIGHLIGHTED COUNTIES
FOR THE WIND CHILL ADVISORY /WHERE APPARENT TEMPERATURES ARE 5
DEGREES OR LESS/ STILL LOOK APPROPRIATE... AND HAVE MADE NO CHANGES
TO THE PRODUCT. THE ADVISORY IS IN EFFECT UNTIL 10 AM. IT WILL NOT
BE TOO MUCH WARMER OUTSIDE OF THE ADVISORY AREA...WHERE TEMPERATURES
WILL STILL FEEL LIKE THEY ARE IN THE SINGLE DIGITS TO LOW TEENS.
SURFACE HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE SOUTHEAST
TODAY AS THE RIDGE AXIS MOVE EASTWARD... KEEPING THE DRY AND CHILLY
AIR MASS OVER THE STATE /SEE FIRE WEATHER SECTION BELOW/. A MODEST
SHORTWAVE APPROACHES THE STATE TONIGHT AND INTO WEDNESDAY
MORNING... DAMPENING SOMEWHAT. AS THE COLUMN SATURATES...EXPECT
THERMODYNAMIC COOLING TO KEEP TEMPERATURES LOW. AS PRECIPITATION
BEGINS ACROSS THE AREA... EXPECT INITIAL LIGHT SNOW/SLEET WEDNESDAY
MORNING TO TRANSITION TO FREEZING RAIN /WPC PRECIP PROBS FOR
FREEZING RAIN ARE IMPRESSIVE/. NORTH GEORGIA COUNTIES WILL CONTINUE
TO SEE A RAIN/SNOW PTYPE THROUGH THE DAY...WITH THE REMAINDER OF THE
AREA TRANSITIONING TO ALL RAIN BY THE AFTERNOON. COLD ANTECEDENT
CONDITIONS WILL PRIME THE AREA TO SEE EARLY IMPACTS...AND HAVE GONE
AHEAD AND UPGRADED THE WINTER STORM WATCH AREA AND EXPANDED
IT...ISSUING A WINTER WEATHER ADVISORY FOR 09Z WEDNESDAY TO 06Z
THURSDAY. SNOW/ICE ACCUMULATIONS HAVE NOT CHANGED SIGNIFICANTLY FROM
THE EVENING FORECAST PACKAGE...AND STILL EXPECTING UP TO 2 INCHES OF
SNOW/SLEET IN THE FAR NORTHERN COUNTIES...AND A QUARTER TO HALF AN
INCH IN PORTIONS OF THE NORTHERN ATLANTA SUBURBS.
THERE STILL REMAINS SEVERAL KEY QUESTIONS AND UNCERTAINTIES WITH THE
FORECAST. MODELS TEND TO BE TOO QUICK TO MODIFY THE
ENVIRONMENT...WARMING TEMPERATURES FASTER THAN REALITY. AS A
RESULT...THE TIMING OF THE TRANSITION TO ALL RAIN MAY BE A LITTLE
FAST. HAVE TRIED TO ACCOMMODATE THIS TREND IN THE FORECAST. ANOTHER
BIG QUESTION IS THE SOUTHERN EXTENT OF THE WINTRY PRECIP. WOULD NOT
BE SURPRISED TO SEE SOME NON-ACCUMULATING WINTRY PRECIP AS FAR SOUTH
STAY ALERT TO THE CHANGING FORECAST...AS IT IS SURE TO EVOLVE AS
THIS EVENT APPROACHES.