#22 Postby PurdueWx80 » Tue Nov 30, 2004 4:50 pm
GRR contemplates a warning from Holland to Grand Rapids, but stays with an advisory for now -
THE GFS HAS FINALLY COME MORE IN LINE WITH THE FARTHER NORTH AND
WEST TRACK OF THE ETA. THUS CONFIDENCE HAS INCREASED THAT A BAND OF
ACCUMULATING WET SNOW IS GOING TO DEVELOP THIS EVENING ACROSS PARTS
OF CENTRAL AND SOUTHERN LOWER MICHIGAN. THE BIG COMPLICATING FACTOR
WITH THIS SYSTEM IS THAT IT IS LIFTING NORTH FROM THE GULF AND
CURRENTLY HAS PRIMARILY RAIN WITH IT. SURFACE TEMPS ARE CURRENTLY IN
THE UPPER 30S...SO THIS EVENT WILL START OUT AS PRIMARILY RAIN
BEFORE CHANGING OVER LATER THIS EVENING.
JUST WHEN THAT CHANGEOVER OCCURS WILL BE VERY CRITICAL FOR HOW MUCH
SNOW ACCUMULATION WE END UP WITH. AM VERY CONCERNED THAT THE AREA
FROM HOLLAND TO GRAND RAPIDS TO ALMA WILL APPROACH OR SLIGHTLY
EXCEED WARNING CRITERIA SNOWFALL. THE LAPS SOUNDINGS NEAR GRR SHOW
THE MELTING LAYER IS AT ABOUT 2500 FEET AND ENTIRELY ABOVE FREEZING
ABOVE THAT. THE WET BULB ZERO IS QUITE LOW AT ONLY 1500 FT. FEEL
THAT ONCE HEAVIER PCPN DEVELOPS... IT WON'T TAKE VERY LONG FOR THE
PCPN TO GO TO PRIMARILY ALL SNOW. THE RUC FCST SOUNDINGS SUPPORT
GOOD DENDRITIC GROWTH UP HIGH AND GOOD AGGREGATION DOWN LOW... WITH
THE STRONGEST OMEGA COINCIDENT WITH THE MAX SNOW GROWTH REGION UP
HIGH. WOULD EXPECT 6 HOURS OF FAIRLY HEAVY SNOW FROM 03Z TO 09Z IN
THE HOLLAND AND GRAND RAPIDS AREAS. WILL KEEP THE ADVISORY FOR
NOW... BUT AM VERY MUCH ON THE FENCE FOR A WARNING IN THIS AREA.
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