FXUS63 KGRR 242104
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
400 PM EST THU DEC 24 2009
LATEST UPDATE...ALL EXCEPT AVIATION...
.SYNOPSIS...(400 PM EST THU DEC 24 2009)
A STRENGTHENING AREA OF LOW PRESSURE WILL LIFT NORTH TONIGHT FROM
ARKANSAS THROUGH MISSOURI. LOWER MICHIGAN WILL BE ON THE EASTERN
FRINGES OF THE SYSTEM...WHICH IS THE WARM SIDE. WINTER STORM
WARNINGS COVER MUCH OF THE PLAINS ON THE WESTERN...COLDER SIDE OF
THE SYSTEM. COLD AIR NEAR GROUND LEVEL WILL COMBINE WITH A SURGE OF
WARM AIR ALOFT TO CREATE CONDITIONS CONDUCIVE FOR A MIXTURE OF
PRECIPITATION INTO CHRISTMAS MORNING. FREEZING RAIN AND FREEZING
DRIZZLE WILL BE THE DOMINANT PRECIPITATION MODE. A WINTER WEATHER
ADVISORY FOR SLEET AND FREEZING RAIN IS IN EFFECT FOR ALL OF
SOUTHWEST LOWER MICHIGAN THROUGH CHRISTMAS DAY. THE MIXTURE OF
PRECIPITATION WILL TRY TO CHANGE OVER TO ALL RAIN ON CHRISTMAS DAY
BEFORE TRANSITIONING BACK TO SNOW FRIDAY NIGHT. COLDER AIR FILTERS
INTO THE AREA FOR THE REMAINDER OF THE WEEKEND AND EARLY NEXT WEEK
WITH SOME LIGHT ACCUMULATIONS OF SNOW POSSIBLE DURING THAT TIME.
&&
.SHORT TERM...(400 PM EST THU DEC 24 2009)
(TONIGHT THROUGH FRIDAY NIGHT)
PULLED THE START TIME OF THE WINTER WEATHER ADVISORY FOR SLEET AND
FREEZING RAIN BACK TO 300 PM GIVEN THE ONGOING LIGHT MIXTURE OF
PRECIPITATION. ALL PRECIPITATION TYPES HAVE BEEN REPORTED...FROM
SLEET...FREEZING RAIN AND SNOW. DOMINANT PRECIPITATION MODE WILL BE
FREEZING RAIN THROUGH THE NIGHT THOUGH.
A LULL IN THE PRECIPITATION MAY OCCUR AFTER DARK...WHICH WILL LIKELY
LEAD TO FREEZING DRIZZLE. AIR TEMPS ARE NEAR FREEZING...SO ROAD
EFFORTS WITH SALT WILL BE EFFECTIVE. MAIN CONCERN WILL BE THE SIDE
ROADS...PARKING LOTS AND SIDEWALKS THAT MAY NOT BE TREATED.
FEELING IS THAT WE ARE LOOKING FOR A COUPLE BURSTS OF PRECIPITATION.
FIRST IS THE ONE MOVING THROUGH SOUTHWEST LOWER MICHIGAN IN A ZONE
OF WARM AIR ADVECTION...SEEN ON THE 290K ISENTROPIC SURFACE. THIS
PRECIPITATION MAY LIFT NORTH OF THE AREA THIS EVENING LEAVING
SOMEWHAT OF A LULL THROUGH THE OVERNIGHT WITH PERIODS OF LIGHT
FREEZING RAIN AND DRIZZLE OCCURRING IN ITS WAKE.
MAIN BATCH OF PRECIPITATION ASSOCIATED WITH THE OCCLUDED FRONT WILL
SPREAD IN LATE TONIGHT AND CHRISTMAS MORNING. TEMPERATURES WILL
STILL BE FLIRTING WITH FREEZING WHICH MAKES THE RAIN/FREEZING RAIN
CALL A HARD ONE. WARM AIR ADVECTION BURST ALOFT IS SIGNIFICANT
THOUGH...SO SEE THE PRECIPITATION TRYING TO GO OVER TO ALL RAIN ON
CHRISTMAS. CONCERN ARE THE SNOW AND ICE PACKED SIDE ROADS THOUGH. AS
RAIN FALLS ONTO THESE COLDER SURFACE REFREEZING MAY STILL TAKE PLACE.
MAIN BAND OF PRECIPITATION WILL BE LIFTING NORTH OF THE AREA AS WE
HEAD INTO FRIDAY NIGHT. NOT EXPECTING SIGNIFICANT PRECIPITATION
FRIDAY NIGHT AS THE RAIN TRANSITIONS BACK TO SNOW. TRAVEL INTO
SATURDAY MORNING COULD BE HAMPERED A BIT BY TEMPS FALLING BACK BELOW
FREEZING. MOST ROADS WILL BE WET FRIDAY EVENING...BUT WITH TEMPS
FALLING INTO THE 20S ICY CONDITIONS WILL LIKELY REDEVELOP INTO
SATURDAY MORNING.
&&
.LONG TERM...(400 PM EST THU DEC 24 2009)
(SATURDAY THROUGH THURSDAY)
THE OCCLUDED LOW PRESSURE SYSTEM WILL BRING SOME LIGHT SNOW THIS
WEEKEND. HOWEVER WE ARE NOT EXPECTING LAKE EFFECT SNOW SATURDAY OR
SATURDAY NIGHT SINCE LOW LEVEL WIND FIELDS WILL BE SOUTH
SOUTHEASTERLY.
OUR BETTER CHC FOR LIGHT SNOW SHOULD HOLD OFF UNTIL SUNDAY WHEN
WINDS WILL FINALLY VEER TO THE WEST TO NORTHWEST. WILL MAINTAIN HIGH
CHC POPS SUNDAY FOR MOST OF OUR CWFA AND LIKELY POPS FOR AREAS WEST
OF US-131. SNOW WILL LINGER SUNDAY NIGHT AND MONDAY BEFORE DRY WX
RETURNS TUESDAY AND WEDNESDAY AS ANTICYCLONIC FLOW BUILDS IN.
$$
.AVIATION...(245 PM EST THU DEC 24 2009)
VERY COMPLEX FCST THE NEXT 24 HRS DUE TO A LIGHT WINTRY MIX OF PCPN.
VFR TO MVFR CONDITIONS ARE ANTICIPATED THIS AFTERNOON. RGNL RADAR
TRENDS INDICATE THAT THE INITIAL BATCH OF PCPN IS MOVING NORTH OF
OUR TAF SITES. HOWEVER ANOTHER BATCH IS MOVING NORTH FROM NORTHERN
INDIANA AND WILL IMPACT ALL OUR TAF SITES LATE THIS AFTERNOON INTO
THE EVENING.
EASTERLY WINDS OF 15 TO 25 KTS WILL CONTINUE THIS AFTERNOON AND
INCREASE TO 20 TO 30 KTS OVERNIGHT THROUGH 18Z FRIDAY.
LIGHT FREEZING RAIN AND SLEET COULD REDEVELOP DURING THE EARLY
MORNING HOURS FRIDAY AND GRADUALLY TRANSITION OVER TO PLAIN RAIN
SHOWERS FROM SOUTH TO NORTH EARLY TO MID FRIDAY MORNING. HOWEVER IT
IS NOTED THAT OVERALL SHORT RANGE COMPUTER MODEL GUIDANCE TRENDS
SUGGEST THAT DRY CONDITIONS SHOULD PREVAIL MOST OF THE NIGHT. THIS
IS CORROBORATED WITH RGNL RADAR TRENDS AND SFC OBS THAT SHOW
PREDOMINANTLY DRY CONDITIONS ACROSS CENTRAL AND SOUTHERN INDIANA.
LIGHT RAIN SHOWERS AND SPRINKLES ARE ANTICIPATED FROM MID MORNING
FRIDAY THROUGH EARLY FRIDAY AFTERNOON WITH CONDITIONS IN THE IFR TO
LIFR FLIGHT CATEGORY.
&&
.MARINE...(400 PM EST THU DEC 24 2009)
CONTINUED THE GALE WARNING WHICH IS IN EFFECT THROUGH CHRISTMAS DAY.
GALE CONDITIONS SHOULD DEVELOP IN THE NEARSHORE WATERS OVERNIGHT.
PERIOD OF HIGHEST WINDS SHOULD BE FROM ABOUT MIDNIGHT THROUGH MIDDAY
ON CHRISTMAS. GIVEN THE OFFSHORE FLOW...HIGHEST WAVES WILL BE AT THE
5 MILE MARK. WINDS SHOULD FALL BELOW GALE LEVELS CHRISTMAS AFTERNOON.
&&
.HYDROLOGY...(400 PM EST THU DEC 24 2009)
NOT EXPECTING ENOUGH IN THE WAY OF PRECIPITATION TO CAUSE MAJOR
CONCERNS. AREA RIVERS ARE AT NORMAL LEVELS PER THE USGS SITE SO QPF
ON THE ORDER OF A HALF INCH THROUGH TOMORROW EVENING SHOULD EASILY
BE ABSORBED. WITH TEMPERATURES AROUND FREEZING THE NEXT 24
HOURS...NOT EXPECTING ANY ICE JAM ISSUES AND HAVE HEARD NOTHING ON
THAT FRONT YET THIS SEASON. RAINFALL ON CHRISTMAS MORNING/DAY COULD
LEAD TO SOME LOCAL PONDING OF WATER IN AREAS THAT HAVE SNOW OR ICE
CLOGGED STORM DRAINS.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY THIS AFTERNOON THROUGH CHRISTMAS DAY
FOR THE ENTIRE CWA.
LM...GALE WARNING THROUGH FRIDAY AFTERNOON FOR THE ENTIRE NEAR SHORE.
&&
$$
SYNOPSIS: DUKE
SHORT TERM: DUKE
LONG TERM: LAURENS
AVIATION: LAURENS
MARINE: DUKE
HYDROLOGY: DUKE
