MESOSCALE DISCUSSION 0102
NWS STORM PREDICTION CENTER NORMAN OK
0720 PM CST TUE FEB 01 2022
AREAS AFFECTED...PARTS OF NORTH CENTRAL MISSOURI INTO WEST CENTRAL
ILLINOIS
CONCERNING...HEAVY SNOW
VALID 020120Z - 020515Z
SUMMARY...MODERATE TO HEAVY SNOW APPEARS LIKELY TO DEVELOP LATE THIS
EVENING. THIS MAY INCLUDE A DEVELOPING BAND WITH PEAK HOURLY RATES
ON THE ORDER OF 1-2 INCHES PER HOUR BETWEEN 9 PM AND MIDNIGHT.
DISCUSSION...AS THE CENTER OF A FAIRLY BROAD AND DEEP SURFACE
CYCLONE MIGRATES INTO AND ACROSS THE JAMES BAY VICINITY THIS
EVENING, COLD SURFACE RIDGING IS IN THE PROCESS OF NOSING SOUTHWARD
TO THE LEE OF THE ROCKIES, AND EASTWARD ACROSS THE UPPER INTO MIDDLE
MISSISSIPPI VALLEY. THE DEEPENING LEADING EDGE OF SUB-FREEZING
SURFACE-BASED AIR (INCLUDING THE SURFACE THROUGH AROUND 850 MB) IS
IN THE PROCESS OF ADVANCING SOUTHWARD INTO PORTIONS OF NORTH CENTRAL
MISSOURI AND WEST CENTRAL ILLINOIS, LIKELY INCLUDING THE
CARROLLTON/BRUNSWICK/MOBERLY MO AND QUINCY IL AREAS WITHIN THE NEXT
FEW HOURS.
LATEST RAPID REFRESH INDICATES THAT THIS WILL COINCIDE WITH
STRENGTHENING LOWER/MID TROPOSPHERIC FRONTOGENETIC FORCING,
INCLUDING THROUGH THE 700-500 MB LAYER, WHERE TEMPERATURES ARE
CONDUCIVE TO LARGE DENDRITIC ICE CRYSTAL GROWTH. AIDED BY FORCING
FOR ASCENT BENEATH AT LEAST BROADLY DIVERGENT UPPER FLOW, FORECAST
SOUNDINGS SUGGEST THAT LIFT MAY BECOME MAXIMIZED WITHIN THE
DENDRITIC GROWTH ACROSS NORTH CENTRAL MISSOURI BY 02-03Z, BEFORE
DEVELOPING NORTHEASTWARD TOWARD WEST CENTRAL ILLINOIS THROUGH
06-07Z.
IT APPEARS THAT THIS WILL BECOME FOCUSED ALONG THE GRADIENT OF A
PLUME OF MOISTURE EMANATING FROM THE GULF OF MEXICO, WHERE
PRECIPITABLE WATER VALUES RANGE FROM AROUND .5-.75 INCHES. AS THE
SURFACE-BASED SUB-FREEZING LAYER DEEPENS, A PERIOD OF SLEET MAY
PRECEDE THE PRECIPITATION TRANSITION TO SNOW, BUT FORECAST SOUNDINGS
FROM RECENT RUNS OF THE RAPID REFRESH, SUPPORTED BY OUTPUT FROM THE
21Z NCEP SREF, SUGGEST THAT AT LEAST A NARROW CORRIDOR WITH 1-2 INCH
PER HOUR SNOW RATES COULD DEVELOP THROUGH 03-06Z.