FXUS63 KGRR 062056
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
356 PM EST SUN DEC 6 2009
LATEST UPDATE...SYNOPSIS/SHORT AND LONG TERM/MARINE/HYDRO...
.SYNOPSIS...(356 PM EST SUN DEC 6 2009)
LIGHT SNOW WILL BE ACROSS AREAS NORTH OF INTERSTATE 96 TONIGHT BUT
ONLY LIGHT ACCUMULATIONS OF AN INCH OR TWO AREA EXPECTED WITH
PERHAPS ANOTHER INCH ON MONDAY AS WEAK LOW PRESSURE MOVES ALONG A
STALLED FRONT. THEN ALL EYES TURN TO THE SOUTHWEST WHERE A WINTER
STORM WILL BE GATHERING BY TUESDAY. THIS STORM WILL BRING HIGH WINDS
AND HEAVY SNOW OR MIXED PRECIPITATION FOR THE WEDNESDAY MORNING
COMMUTE. THEN LAKE EFFECT SNOW COMBINED WITH 40 MPH WIND GUSTS COULD
IMPEDE TRAVEL WEDNESDAY NIGHT AND THURSDAY.
&&
.SHORT TERM...(356 PM EST SUN DEC 6 2009)
(TONIGHT THROUGH TUESDAY NIGHT)
FORECAST ISSUES IN THE NEAR TERM ARE FOR LIGHT SNOW TONIGHT AND
HEAVY SNOW POTENTIAL TUESDAY NIGHT. FOR TONIGHT...AREA OF LIGHT SNOW
WAY BACK ACROSS WESTERN IOWA ASSOCIATED F-GEN FORCING AND THIS WILL
TRANSLATE EAST ALONG AND NORTH OF THE PATH OF THE WEAK SFC LOW THAT
WILL BE MOVING ALONG THE STATIONARY FRONT NOW DRAPED OVER OUR
NORTHERN FORECAST AREA.
THIS FRONT IS ALSO PROVIDING SOME LOW LEVEL CONVERGENCE AND
ENHANCING THE FEW REMAINING LAKE EFFECT SNOW SHOWERS ACROSS THE
NORTHERN ZONES. DECIDED TO KEEP LOW CHANCE POPS UP NORTH FOR THIS
EVENING TO ACCOUNT FOR THIS. THE DEEPER MOISTURE AND BETTER LIFT
ARRIVES AFTER 06Z...AND WITH SOME LAKE ENHANCEMENT...SHOULD SEE
LIGHT ACCUMS ACROSS ROUGHLY THE NORTHERN HALF OF THE FORECAST AREA
BETWEEN 06Z AND 18Z MONDAY. MADE ONLY SLIGHT TWEAKS TO CURRENT SNOW
GRIDS FOR THIS PERIOD...WITH ABOUT 2 INCHES OF ACCUMS FROM NORTH OF
MKG TO RQB AND OVER TO MOP.
ONCE THIS WEAK SYSTEM MOVES EAST BY MONDAY NIGHT...THERE SHOULD BE A
LULL IN THE ACTION UNTIL TUESDAY NIGHT WHEN DEEP MOISTURE ARRIVES
AND ISENTROPIC ASCENT INCREASES ASSOCIATED WITH MAJOR SOUTHERN
PLAINS CYCLONE. TRACK OF THE LOW HAS BEEN PRETTY CONSISTENTLY
HANDLED BY THE GFS AND EXPECT HEAVY SNOW TO MOVE FROM SOUTHWEST TO
NORTHEAST ACROSS THE FORECAST AREA DURING THE EVENING. MIX TO SLEET
AND FREEZING RAIN POSSIBLE ACROSS THE SOUTH AFTER 06Z WEDNESDAY AS
SEEN IN GFS THERMAL PROFILES. DRY SLOT MAY ALSO BE AN ISSUE ACROSS
THE SOUTH...BUT PROBABLY NOT UNTIL BEYOND 12Z WEDNESDAY.
&&
.LONG TERM...(356 PM EST SUN DEC 6 2009)
(WEDNESDAY THROUGH SUNDAY)
THE MID RANGE MODELS CONTINUE TO TRACK A STRONG LOW PRESSURE SYSTEM
THROUGH THE GREAT LAKES REGION EARLY WEDNESDAY INTO WEDNESDAY NIGHT.
THE 12Z GFS HAS A LOW OF 984 MB DEEPENING TO 986 MB AS IT MOVES
FROM GARY INDIANA TO EASTERN LAKE HURON. THE 12Z ECMWF HAS THE LOW
DEEPENING FROM 980 MB TO 970 MB AS IT MOVES FROM SOUTH OF GARY
INDIANA TO CENTRAL LAKE HURON. PRECIPITATION MAY BE IN THE FORM OF
RAIN... ICE PELLETS OR SNOW ACROSS SOUTHERN LOWER MICHIGAN WEDNESDAY
MORNING AS A WARM WEDGE MOVES THROUGH. THIS WILL LIMIT THE SNOW
ACCUMULATIONS ACROSS THE SOUTH. A GOOD PRESSURE GRADIENT AND
CYCLONIC FLOW AS COLD AIR FLOWS IN BEHIND THE SYSTEM WILL KICK UP
LAKE EFFECT SNOWS BEHIND THIS SYSTEM OVERNIGHT WEDNESDAY THROUGH
THURSDAY.
THE MODELS THEN SHOW SPLIT FLOW AROUND AN AREA OF HIGH PRESSURE
THAT BUILDS INTO THE CENTER OF THE CONTINENT. LOW PRESSURE SYSTEMS
WILL MOVE BY TO THE NORTH AND SOUTH OF THE AREA LATE FRIDAY AND
SATURDAY. COLD AIR WILL CONTINUE TO FLOW ACROSS LAKE MICHIGAN AND
LIGHT LAKE EFFECT SNOW SHOWERS AND FLURRIES WILL CONTINUE TO BE
POSSIBLE.
TEMPERATURES IN THE LONG TERM WILL BE MOSTLY BELOW NORMAL FOR THIS
TIME OF THE YEAR WITH A FEW PERIODS NEAR NORMAL. NORMAL HIGHS ARE IN
THE MID 30S AND NORMAL LOWS ARE IN THE LOWER 20S.
&&
.AVIATION...(1231 PM EST SUN DEC 6 2009)
SOUTHWEST FLOW OFF OF LAKE MICHIGAN IS PRODUCING A FEW FLURRIES OR
LIGHT SNOW SHOWERS AND CEILINGS FROM 2500 TO 3500 FEET FROM THE MKG
TAF SITE AND TO THE NORTH. CEILINGS OF 6000 FEET STRETCH FROM SOUTH
HAVEN TO THE LAN TAF SITE AND NORTH. EXPECT THESE CONDITIONS TO
CONTINUE INTO THE NIGHT. A CHANCE OF ACCUMULATING SNOW RETURNS
OVERNIGHT... AS A LOW PRESSURE SYSTEM MOVES THROUGH THE REGION.
EXPECT THE HEAVIER SNOW NORTH OF A LINE FROM HOLLAND TO GRR TO MOUNT
PLEASANT. THIS SHOULD BRING IFR VISIBILITIES TO MKG AND GRR. THE
CEILINGS ACROSS THE TAF SITES WILL BE AT MVFR LEVELS THROUGH
TOMORROW WITH VISIBILITIES AWAY FROM THE HEAVIER SNOW ALSO AT MVFR
LEVELS. GUSTY WINDS WILL DIMINISH THIS EVENING AND NO STRONG WINDS
ARE ANTICIPATED TONIGHT OR TOMORROW.
&&
.MARINE...(356 PM EST SUN DEC 6 2009)
OFFSHORE FLOW AND DECREASING WAVES TONIGHT. BIG STORM FOR WEDNESDAY
AND THURSDAY WITH GALES LIKELY WEDNESDAY NIGHT...MAYBE STORM FORCE
WIND GUSTS.
&&
.HYDROLOGY...(356 PM EST SUN DEC 6 2009)
NO HYDRO ISSUES AT LEAST THROUGH TUESDAY. STILL LOOKS LIKE WEDNESDAY
STORM WILL BE MORE SNOW OR MIXED PRECIP THAN RAIN. STAY TUNED.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
&&
$$
SYNOPSIS: OSTUNO
SHORT TERM: OSTUNO
LONG TERM: IOD
AVIATION: IOD
MARINE: OSTUNO
HYDROLOGY: OSTUNO
