FXUS63 KGRR 080319
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1019 PM EST MON DEC 7 2009
LATEST UPDATE...SHORT TERM...
.SYNOPSIS...(405 PM EST MON DEC 7 2009)
A POWERFUL WINTER STORM WILL MOVE INTO LOWER MICHIGAN TUESDAY NIGHT
AND WEDNESDAY. SNOW WILL BREAK OUT TUESDAY AFTERNOON AND BECOME
HEAVY TUESDAY NIGHT NORTH OF INTERSTATE 96. MIXED PRECIPITATION CAN
BE EXPECTED NEAR AND SOUTH OF INTERSTATE 96 RESULTING IN SOME ICING
AND HAZARDOUS TRAVEL CONDITIONS.
MIXED RAIN... FREEZING RAIN AND SNOW WEDNESDAY MORNING WILL CHANGE
TO LAKE EFFECT SNOW SHOWERS WEDNESDAY AFTERNOON AS THE WINDS CRANK
UP WITH GUSTS TO 50 MPH AND WHITEOUT CONDITIONS ACROSS WESTERN LOWER
MICHIGAN. LAKE EFFECT SNOW WILL CONTINUE THURSDAY NIGHT AND FRIDAY.
&&
.SHORT TERM...(1019 PM EST MON DEC 7 2009)
(TONIGHT THROUGH WEDNESDAY)
WILL ADD AREAS OF FOG TO THE OVERNIGHT FORECAST. POCKETS OF FOG ARE
MOVING IN AND OUT AS PARTIAL CLEARING OCCURS. AS WINDS INCREASE AND
THE HIGH CLOUDS MOVE IN TOWARD MORNING THE FOG SHOULD TEND TO BECOME
PATCHY.
AS FOR THE PENDING STORM...WILL CONTINUE WITH THE CURRENT HEADLINES.
AS OF 03Z THE LOW CONTINUES TO DEEPEN OVER THE NEVADA/ARIZONA BORDER
WITH SNOW BREAKING OUT AS FAR EAST AS NORTHERN MISSOURI.
PREVIOUS DISCUSSION FROM 405 PM...
HAVE ISSUED A WINTER STORM WARNING FOR NORTHERN TWO ROWS OF COUNTIES
PLUS MUSKEGON COUNTY...WHICH REPLACES THE WATCH. THIS IS BASED ON
HIGH CONFIDENCE OF HEAVY SNOW THERE. WILL LET THE REST OF THE WATCH
RIDE. THE 12Z EURO AND GFS SHOW REMARKABLE RUN TO RUN CONSISTENCY
ONCE AGAIN AND THE ONLY NOTICEABLE TREND IS FOR A SLIGHTLY FASTER
ARRIVAL OF THE WAA SNOW...SO POPS AND QPF WERE TWEAKED UP FOR
TUESDAY AFTERNOON. STRONG AREA OF WAA/ISENTROPIC ASCENT SHOULD LEAD
TO A QUICK BURST OF SNOW EVEN ACROSS THE FAR SOUTHERN FORECAST AREA
BEFORE WARMING EVENTUALLY LEADS TO CHANGEOVER BY LATE IN THE EVENING
ALONG THE I-94 CORRIDOR.
ONE BIG ISSUE TO BE DETERMINED IS THE EXTENT OF FREEZING RAIN/ICING
ACROSS THE CENTRAL AND SOUTHERN FORECAST AREA. SYNOPTIC SET UP WITH
SFC HIGH SITTING OVER NORTHERN NEW ENGLAND WOULD BE FAVORABLE FOR A
PERIOD OF EASTERLY WINDS FEEDING COLD AIR IN NEAR THE SURFACE. THIS
PERSISTS THROUGH ABOUT 12Z WEDNESDAY MORNING...SO WILL HAVE TO WATCH
ICING POTENTIAL CAREFULLY LATE TUESDAY NIGHT AND WEDNESDAY
MORNING.
OTHER CONCERN IS FOR HOW MUCH OF A DRY SLOT GETS INTO THE FORECAST
AREA BY WEDNESDAY MORNING. WITH THE SFC LOW PROGGED TO MOVE ACROSS
THE SOUTHERN OR CENTRAL CWA...IT APPEARS THE HEAVY PRECIP WILL BE
DISPLACED TO THE NORTH OF THE TRACK OF THE SFC LOW. THIS COMBINED
WITH THE EFFECT OF MIXED PRECIP WORKING INTO THE CENTRAL CWA WILL
PUT A SHARP GRADIENT IN THE SYNOPTIC SNOWFALL RIGHT THROUGH THE
MIDDLE OF THE FORECAST AREA.
LAKE EFFECT SNOW BEGINS WEDNESDAY AFTERNOON AS THE SFC LOW PULLS
AWAY TO THE NORTHEAST AND COLDER AIR SURGES IN. WINDS WILL ALSO BE
PICKING UP BUT THE WORST OF THE LAKE EFFECT/HIGH WINDS WILL OCCUR
AFTER 00Z THURSDAY AS THE COLD AIR ADVECTION INTENSIFIES.
&&
.LONG TERM...(405 PM EST MON DEC 7 2009)
(WEDNESDAY NIGHT THROUGH MONDAY)
BIGGEST CONCERNS IN THE LONG TERM ARE THE LAKE EFFECT SNOW SHOWERS
AND WINDS/BLOWING SNOW ISSUES FOR THE WED NIGHT AND THU TIME FRAME.
LAKE EFFECT POTENTIAL WILL HAVE TO BE ADDRESSED FOR THE REMAINDER OF
THE PERIOD.
PCPN FROM THE SYNOPTIC PORTION OF THE BIG STORM IS EXPECTED TO HAVE
EXITED THE CWFA BY THE BEGINNING OF THE LONG TERM WED NIGHT. STRONG
GRADIENT ON THE BACKSIDE OF THE SYSTEM WILL USHER IN MUCH COLDER AIR
ON W/NW FLOW. H850 TEMPS ARE EXPECTED TO DROP AT LEAST INTO THE
NEGATIVE UPPER TEENS AND AROUND -20C BY THU MORNING. THIS WILL
PRODUCE NUMEROUS TO WIDESPREAD LAKE EFFECT SNOW SHOWERS. WINDS
GUSTING UP TO AROUND 40 MPH OR SO ON WED NIGHT AND THU ARE STILL
EXPECTED TO PRODUCE BLOWING AND DRIFTING SNOW WHICH WILL REDUCE
VISIBILITIES QUITE A BIT.
LAKE EFFECT SNOW SHOWERS WILL BE NUMEROUS TO WIDESPREAD...HOWEVER
ACCUMULATIONS WILL BE LIMITED SOMEWHAT BY A COUPLE OF FACTORS. CLOUD
MICROPHYSICS WILL LIMIT ACCUMULATION POTENTIAL SOME AS DGZ WILL BE
QUITE LOW NEAR THE GROUND...PROVIDING SMALLER SNOWFLAKES. STRONGER
WINDS WILL ALSO LIMIT THE ACCUMS SOME AS SNOW BLOWS INLAND A BIT.
WIND CHILLS WILL BE FAIRLY LOW WITH TEMPS IN THE TEENS TO LOWER 20S
AND THE STRONG WINDS. EITHER WAY...WED NIGHT AND THU LOOK FAIRLY
WINTRY.
THE ENTIRE SYSTEM WILL LIFT NE OUT OF THE REGION BY THE DAY ON FRI.
DEEP COLD AIR WILL LIFT OUT BY THE DAY ON FRI...LEAVING A MORE
SHALLOW...YET COLD LOW LEVEL AIR MASS. THIS COMBINED WITH A WRLY
COMPONENT TO THE WIND WILL MAINTAIN SNOW SHOWERS...ESPECIALLY FOR
WRN AREAS. POTENTIAL FOR SIGNIFICANT ACCUMS WILL GO DOWN WITH A
LIMITED DEPTH OF MOISTURE.
A NRN STREAM SHORT WAVE LOOKS TO MOVE THROUGH THE AREA LATE SAT AND
INTO EARLY SUN. FRONT ITSELF DOES NOT HAVE A LOT OF MOISTURE WITH
IT...BUT LAKE ENHANCEMENT COULD HELP IT OUT A BIT. THIS FRONT WILL
REINFORCE THE COLD TEMPS A BIT. LAKE EFFECT FOR SUN AND MON IS A BIT
UNCERTAIN DEPENDING ON THE WAY THE HIGH BUILDS IN. THE FLOW COULD
END UP BECOMING OFFSHORE WHICH WOULD SHUT THE LAKE EFFECT OFF. FOR
NOW WE HAVE ASSUMED A ONSHORE FLOW WILL CONTINUE WITH A CHC OF SOME
LAKE EFFECT.
&&
.AVIATION...(850 PM EST MON DEC 7 2009)
WEAK FRONTAL BOUNDARY HAS SAGGED INTO SOUTHWEST LOWER MICHIGAN THIS
EVENING...STRETCHING FROM NEAR SOUTH HAVEN TO SAGINAW BAY.
CONDITIONS ARE QUITE VARIED ACROSS THE AREA WITH SOME AREAS
CLEAR...OTHERS CARRYING MVFR CEILINGS AND FINALLY SOME SPOTS LIKE
BIG RAPIDS DOWN IN A QUARTER MILE AND FOG.
THE FOG HAS FORMED IN AREAS THAT CLEARED OUT WITH COLD AIR SETTLING
IN BEHIND THE FRONT INTERACTING WITH A MOIST LOW LEVEL AIRMASS. MID
AND HIGH CLOUDS ARE ALREADY STREAMING TOWARD THE AREA ACROSS
ILLINOIS. IN GENERAL...EXPECTING THE VARIED CONDITIONS TO CONTINUE
THIS EVENING...TRENDING MORE TOWARD MVFR TOWARD MORNING. CONDITIONS
BEGIN TO SLIDE DOWNHILL MONDAY AFTERNOON IN ADVANCE OF THE SYSTEM
SWEEPING OUT OF THE PLAINS WITH CONDITIONS DROPPING INTO THE IFR
CATEGORY.
&&
.MARINE...(405 PM EST MON DEC 7 2009)
A GALE WATCH REMAINS IN EFFECT FROM WEDNESDAY AFTERNOON THROUGH
THURSDAY EVENING. HIGH END GALES ARE EXPECTED WITH POTENTIAL FOR
STORM FORCE WINDS.
&&
.HYDROLOGY...(405 PM EST MON DEC 7 2009)
NO HYDRO ISSUES EXPECTED ALTHOUGH SOME RISES ARE POSSIBLE IN
KALAMAZOO RIVER BASIN DEPENDING ON HOW MUCH QPF FALLS IN THE FORM OF
RAIN EARLY WEDNESDAY MORNING.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...WINTER STORM WARNING FOR MUSKEGON COUNTY AND THE NORTHERN TWO
ROWS OF COUNTIES FOR TUESDAY EVENING THROUGH WEDNESDAY NIGHT.
WINTER STORM WATCH FOR THE REST OF THE CWFA WITH THE EXCEPTION OF
CALHOUN AND JACKSON COUNTIES FROM TUESDAY EVENING THROUGH WEDNESDAY
NIGHT.
LM...GALE WATCH ST. JOSEPH TO MANISTEE FROM WEDNESDAY AFTERNOON
THROUGH THURSDAY EVENING.
&&
$$
SYNOPSIS: OSTUNO
SHORT TERM: OSTUNO JK
LONG TERM: NJJ
AVIATION: DUKE
MARINE: OSTUNO
HYDROLOGY: OSTUNO
