FXUS63 KGRR 101724
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1215 PM EST THU DEC 10 2009
LATEST UPDATE...SHORT TERM MARINE AND HYDROLOGY...
.SYNOPSIS...(409 AM EST THU DEC 10 2009)
LAKE EFFECT SNOW SHOWERS WILL CONTINUE THIS AFTERNOON ALONG WITH
STRONG WEST WINDS. THE SNOW WILL BE HEAVIEST AND MOST PERSISTENT
OVER THE SOUTHWEST PORTION OF THE STATE...GENERALLY ALONG AND SOUTH
OF INTERSTATE 96 AND WEST OF ROUTE 66. THE COMBINATION OF THE
SNOW...WIND AND BLOWING SNOW WILL FREQUENTLY PRODUCE BLIZZARD
CONDITIONS WITH VISIBILITIES FALLING TO NEAR ZERO. TRAVEL IN THIS
AREA WILL BE SEVERELY IMPACTED INTO TONIGHT.
ELSEWHERE OVER SOUTHWEST LOWER MICHIGAN...THE SNOW SHOWERS WILL BE
LESS INTENSE AND LESS FREQUENT. HOWEVER...THE BRISK WINDS WILL
CAUSE BLOWING AND DRIFTING SNOW. THEREFORE...A WINTER WEATHER
ADVISORY IS IN EFFECT THROUGH TONIGHT.
CONDITIONS ARE EXPECTED TO IMPROVE FRIDAY AS THE SNOW AND WIND
DIMINISH.
&&
.SHORT TERM...(1215 PM EST THU DEC 10 2009)
(THIS AFTERNOON THROUGH SATURDAY)
HAVE EXTENDED THE CURRENT HEADLINES THROUGH TONIGHT.
MOISTURE REMAINS RELATIVELY DEEP THROUGH THE NIGHT...UP TO AROUND
-25 DEG C ACROSS THE WARNING AREA. PERSISTENT SURFACE CONVERGENCE
IS SHOWN IN A BAND BETWEEN GRR AND AZO. SEVERAL MODELS SHOW THIS
SCENARIO. ANOTHER SHORTWAVE UP OVER NORTH DAKOTA MOVES IN THIS
EVENING...AND WILL LIKELY ENHANCE THE SNOWFALL. OVERVIEWS FROM
BUFKIT ESPECIALLY AROUND LWA SHOW STRONGER LIFT WITHIN THE DGZ FROM
00Z TO 06Z. THIS SUPPORTS HEAVY SNOW. THE -10 DEG C IS FAIRLY
CLOSE TO THE GROUND CURRENTLY...SNOW ACCUMULATION RATES MAY DROP OFF
FOR A FEW HOURS...HOWEVER IT RISES OVERNIGHT...WITH THE SHORTWAVE
MOVING IN. WE TAP INTO THE 30 TO 40 KNOT WINDS THROUGH THE
NIGHT...THUS WILL MAINTAIN THE BLIZZARD WARNING.
FURTHER EAST FOR THE ADVISORY AREA...SURFACE CONVERGENCE EXTENDS TO
AT LEAST LAN THROUGH THE NIGHT. THIS SUPPORTS LAKE EFFECT SNOW
BANDS EXTENDING WELL INLAND. WHILE THE BANDS WILL LIFT NORTH OF JXN
FOR A WHILE...WIND CHILL VALUES WILL REMAIN CLOSE TO ADVISORY
LEVELS. THUS WILL INCORPORATE THIS INTO THE WINTER WEATHER ADVISORY.
THE SNOW SHOULD END BY LATE FRIDAY NIGHT AS ANTICYCLONIC FLOW
DEVELOPS. SATURDAY LOOKS DRY AND WARMER AS RETURN FLOW DEVELOPS ON
THE BACKSIDE OF HIGH PRESSURE.
&&
.LONG TERM...(409 AM EST THU DEC 10 2009)
(SATURDAY NIGHT THROUGH WEDNESDAY)
WHILE THE OVERALL COLD PATTERN SEEMS LIKELY TO PREVAIL (RELATED TO
MJO CONVECTION BEING EAST OF INDONESIA)... IT SEEMS TO ME WE COULD
WELL SEE A TWO DAY WARM UP EARLY NEXT WEEK. WE CAN THANK THAT STRONG
PACIFIC SHORTWAVE THAT IS FORECAST TO UNDERCUT THE LARGE UPPER LEVEL
RIDGE OFF THE WEST COAST FOR THIS WARM UP. AS THE SHORTWAVE COMES
INTO THE SOUTHERN PLAINS...IT MAY WELL BUCKLE THE UPPER LEVEL
PATTERN ENOUGH TO CAUSE A BRIEF WARM UP EARLY NEXT WEEK. THERE IS
POTENTIAL FOR PHASING OF THE NORTHERN AND SOUTHERN STREAM IN THE
MON/TUE TIME FRAME AS THAT SOUTHERN STREAM WAVE MOVES OUT INTO THE
SOUTHERN PLAINS. IF THAT HAPPENED WE WOULD SEE AN EVEN STRONGER WARM
UP... AND AN MUCH STRONGER COOL DOWN BEHIND THE COLD FRONT. THE
ISSUE HERE IS A CONFIDENCE THING. THE SHORTWAVE HAS NOT COME ON
SHORE YET AND THE MODELS NOTORIOUSLY DO NOT DO WELL WITH THOSE TYPES
OF SOUTHERN STREAM SHORTWAVES.
EVEN SO... THE WARM ADVECTION LIFT PART OF THE EVENT SEEMS LIKELY TO
CAUSE SNOW SUNDAY. BY MONDAY THERE SHOULD BE ENOUGH WARMING TO
CHANGE THE SNOW TO RAIN. I DID NOT WARM THE GRID TEMPS AS MUCH AS I
THROUGH WOULD REALLY HAPPEN ON SUN...MON AND TUE TO GIVE US ROOM FOR
MODEL FOR FLEXIBILITY IN LATER FORECAST. RAIN WOULD GO BACK TO SNOW
MONDAY NIGHT AS THE COLD AIR COMES BACK IN.
THE COLD AIR WOULD RETURN WITH LAKE EFFECT SNOW SHOWERS IN THE
TUESDAY NIGHT / WEDNESDAY TIME FRAME. IF PHASING OCCURS THAT AIR
WOULD BE COLDER THAN WHAT WE WILL SEE TODAY (THURSDAY).
WE MUST NOT FORGET ABOUT THE LARGE RETROGRADING CLOSED UPPER HIGH
FROM GREENLAND. THAT SHOULD BY ITSELF BE REASON ENOUGH TO KEEP LOWER
MICHIGAN BELOW NORMAL IN TEMPERATURES OVERALL FOR NEXT WEEK.
&&
.AVIATION...(715 AM EST THU DEC 10 2009)
THERE AREA TWO SIGNIFICANT SHORTWAVES THAT WILL CROSS LAKE MICHIGAN
INTO LOWER MICHIGAN WITHIN THE NEXT 12 HOURS. EACH OF THESE
SHORTWAVES WILL ENHANCE THE SNOW SHOWER ACTIVITY FOR ABOUT 2 HOURS
PRIOR TO PASSAGE THEN DIMINISH THE SNOW SHOWERS FOR ABOUT 2 HOURS
BEHIND THEM. THIS FIRST ONE WILL CROSS INTO SOUTHWEST MICHIGAN
AROUND 15Z THEN THE NEXT ONE WILL BE CLOSER TO 00Z.
FREQUENT IFR/LIFR CONDITIONS DUE TO SNOW SHOWERS AND BLOWING SNOW
WILL CONTINUE THROUGH FRIDAY EVENING AS COLD AIR AND STRONG WINDS
POUR IN BEHIND THE DEPARTING LOW PRESSURE CENTER. THE HEAVIEST SNOW
BANDS TODAY WILL BE FOCUSED ON KGRR AND KMKG WITH KAZO AND KBTL
HAVING SIMILAR CONDITIONS BUT A LITTLE LESS SO.
&&
.MARINE...(1215 PM EST THU DEC 10 2009)
THE GALE WARNING WILL BE EXTENDED INTO TONIGHT. THEREAFTER IT
APPEARS WINDS WILL GRADUALLY DIMINISH INTO FRIDAY AND FRIDAY NIGHT
AS A RIDGE OF HIGH PRESSURE BUILDS TO OUR SOUTH.
&&
.HYDROLOGY...(1215 PM EST THU DEC 10 2009)
NO HYDRO ISSUES EXPECTED AS COLD AIR HAS FROZEN ANY STANDING WATER.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...BLIZZARD WARNING MUSKEGON...KENT...OTTAWA...ALLEGAN...BARRY...
VAN BUREN AND KALAMAZOO COUNTIES THROUGH TONIGHT.
WINTER WEATHER ADVISORY FOR THE REST OF THE CWA THROUGH TONIGHT.
LM...GALE WARNING ST. JOSEPH TO MANISTEE THROUGH TONIGHT.
&&
$$
SYNOPSIS: MJS
SHORT TERM: MJS
LONG TERM: WDM
AVIATION: WDM
MARINE: MJS
HYDROLOGY: MJS
