FXUS63 KGRR 260450
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1155 PM EST WED NOV 25 2009
LATEST UPDATE...AVIATION...
.SYNOPSIS...(405 PM EST WED NOV 25 2009)
LOW PRESSURE WILL LINGER ACROSS THE NORTHERN GREAT LAKES REGION INTO
THANKSGIVING BRINGING THE CHANCES FOR BOTH RAIN AND SNOW. OCCASIONAL
RAIN SHOWERS WILL CONTINUE TONIGHT LASTING INTO THE DAY ON
THANKSGIVING. COLDER AIR WILL GRADUALLY FILTER INTO THE STATE
ALLOWING FOR THE POSSIBILITY OF SNOW MIXING IN AT TIMES THANKSGIVING
EVENING AND NIGHT. SOME LIGHT ACCUMULATIONS OF SNOW ARE NOT OUT OF
THE REALM OF POSSIBILITIES ESPECIALLY ALONG AND WEST OF HIGHWAY 131
ON THANKSGIVING EVENING. TRAVEL PROBLEMS ARE NOT EXPECTED THROUGH
THE HOLIDAY WEEKEND AS ANY SNOW THAT OCCURS THURSDAY NIGHT SHOULD BE
LIGHT AND ROADS SHOULD BE WET. FOR THE REMAINDER OF THE WEEKEND...
DRY CONDITIONS ARE EXPECTED FOR MOST OF FRIDAY AND SATURDAY. THERE
IS A CHANCE OF LIGHT RAIN SUNDAY AS A LOW PRESSURE SYSTEM MOVES
THROUGH THE GREAT LAKES.
&&
.SHORT TERM...(405 PM EST WED NOV 25 2009)
(TONIGHT THROUGH FRIDAY NIGHT)
MAIN SHORT TERM ISSUES PERTAIN TO THE LOW PRESSURE SYSTEM TRAVERSING
THE GREAT LAKES AT THIS TIME. PRECIPITATION TYPE/CHANCES ARE THE
MAIN POINTS OF CONTENTION.
TONIGHT...THE PRECIPITATION SHOULD BE ALL RAIN. THE RAIN IS QUITE
SCATTERED AT THIS POINT...BUT IT SHOULD RAMP UP IN COVERAGE AS THE
UPPER LOW OFF TO THE WEST PUSHES IN. DELTA T/S WILL ALSO SLOWLY
CLIMB ALLOWING FOR SOME LAKE ENHANCEMENT. BY MORNING...THE NAM IS
PRODUCING DELTA T/S AROUND 13 DEGREES C.
SURFACE TROUGH SWINGS THROUGH ON THANKSGIVING WHICH WILL CONTINUE
THE RAIN SHOWERS OVER MUCH OF THE AREA. THE FAR SOUTHEAST WILL SEE
THE LOWEST CHANCES FOR PRECIPITATION IN THE MORNING...BUT IT SHOULD
RAMP UP IN THE AFTERNOON AS THE TROUGH PRESSES EAST. AIR MAY BE JUST
COLD ENOUGH IN THE AFTERNOON AND EARLY EVENING TO ALLOW SOME SNOW TO
MIX IN.
THE BEST CHANCE FOR SNOW WILL COME THURSDAY NIGHT AS THE CORE OF THE
COLD AIR ALOFT MOVES THROUGH. DELTA T/S WILL BE IN THE MIDDLE TEENS C
AT LEAST. IT APPEARS NORTHWEST FLOW LAKE EFFECT BANDS WILL GET GOING
DURING THE EVENING. THERE MAY EVEN BE A DOMINANT BAND THAT PUSHES
INTO PORTIONS OF ALLEGAN AND VAN BUREN COUNTIES. GIVEN THE WARM
LAKE...RAIN CAN BE EXPECTED NEAR THE COAST. AWAY FROM THE LAKE
THOUGH SOME LIGHT ACCUMS ARE NOT OUT OF THE QUESTION. AROUND AN INCH
OR SO POSSIBLE ON GRASSY AREAS AFTER DARK.
&&
.LONG TERM...(405 PM EST WED NOV 25 2009)
(SATURDAY THROUGH WEDNESDAY)
BIGGEST CHALLENGE IN THE LONG TERM WILL BE DETERMINING THE CHC OF
PCPN FOR THE FIRST HALF OF THE WEEK AS A COMPLEX PATTERN SETS UP
DURING THIS PERIOD.
SATURDAY CONTINUES TO LOOK LIKE A DECENT NOVEMBER DAY AS A HEALTHY
RIDGE MOVES IN BEHIND THE DEPARTING THANKSGIVING SYSTEM. H850 TEMPS
OF 4 TO 6C COULD PROVIDE TEMPS WELL INTO THE 40S IF WE CAN CLEAR OUT
THE LOW CLOUDS.
THE BREAK IN THE WEATHER WILL BE SHORT-LIVED HOWEVER AS A NRN STREAM
TROUGH WILL PUSH A COLD FRONT INTO THE AREA DURING THE DAY ON SUN.
THIS FRONT HAS BEEN ADVERTISED THE PAST FEW DAYS TO HAVE LIMITED
MOISTURE ASSOCIATED WITH IT RESULTING IN A LOW PCPN EVENT. MODELS
HAVE BEEN TRENDING TOWARD A BIT MORE PHASING WITH A LEAD SHORT WAVE
EJECTING FROM THE DIGGING SW TROUGH...AND TAPPING SOME GULF OF
MEXICO MOISTURE.
A THREAT OF PCPN STILL EXISTS ON MON. THE NRN TROUGH WILL BE IN THE
PROCESS OF CROSSING THE STATE. LATEST MODELS HAVE BEEN BRINGING
ANOTHER SRN STREAM WAVE TO THE NE AHEAD OF THE NRN TROUGH. THE
DETAIL IN QUESTION HERE WOULD BE HOW MUCH PCPN...DEPENDING ON THE
DEGREE OF PHASING THAT OCCURS.
CONFIDENCE IS INCREASING THAT TUE AND WED NEXT WEEK WILL BE DRY. THE
BIG TROUGH DIGGING THIS WEEKEND OVER THE SW CORNER OF THE U.S. LOOKS
LIKE IT WILL NOT QUITE CLOSE OFF AS QUICKLY. SOME OF THE ENERGY WILL
EJECT EARLY IN THE WEEK...AND LEAVE THE REST OF IT TO ROLL ACROSS
THE SRN PORTION OF THE COUNTRY. WE LOOK TO BE LEFT IN BETWEEN THE
TWO STREAMS...AND UNDER MORE INFLUENCE FROM THE NRN STREAM RIDGE.
THE ENSEMBLES HAVE BEEN POINTING AT THIS...AND THE OPERATIONAL
MODELS ARE NOW FOLLOWING.
&&
.AVIATION...(1155 PM EST WED NOV 25 2009)
THE MAIN CONCERN DEALS WITH THE TIMING OF THE IFR CONDITIONS THROUGH
THURSDAY AND SOME ICING TONIGHT.
A MIXTURE OF IFR AND MVFR CONDITIONS COVER THE TAF SITES IN
SOUTHWEST LOWER MI AT THIS TIME. CURRENTLY A WARM FRONT HAS LIFTED
NORTH TO AROUND KGRR AS A WAVE OF LOW PRESSURE IS DEVELOPING NEAR
KLDM. LOOKS LIKE OBSERVATIONAL TRENDS AND MODEL DATA SUGGEST MVFR
WITH PERHAPS VFR WEATHER SOUTHEAST OF A LINE FROM KLAN TO KBTL FOR
MUCH OF THE NIGHT INTO THURSDAY. HOWEVER AS THE LOW SLOWLY TRACKS
EAST NORTHEAST...KMKG AND KGRR TO KAZO WILL DROP DOWN TO IFR...AND
PERHAPS LOWER. NOT CONFIDENT ENOUGH TO ADD LIFR AT THIS TIME...BUT
KMKG APPEARS TO BE MOST PRONE FOR THESE LOW CONDITIONS ESPECIALLY
THURSDAY.
CURRENTLY IT LOOKS TOO WARM FOR SNOW...BUT SOME DRYING ABOVE 10000
FEET BETWEEN 06Z AND 14Z COULD CREATE AN ENVIRONMENT FOR
A LAYER OF ICING BETWEEN 2000 FT TO 8000 FT.
NORTHWESTERLY WINDS WILL DEVELOP THURSDAY AFTERNOON. THUS GRADUAL
IMPROVEMENT IN CEILINGS FROM NORTHWEST TO SOUTHEAST IS EXPECTED
DURING THE LATE AFTERNOON THROUGH THE EVENING HOURS.
&&
.MARINE...(405 PM EST WED NOV 25 2009)
EXPANDED THE SMALL CRAFT ADVISORY BOTH IN AREA AND TIME. EXTENDED
THE ADVISORY NORTH TO INCLUDE THE PENTWATER TO MANISTEE ZONE AND
PUSHED IT OUT THROUGH THANKSGIVING NIGHT NOW (VALID THROUGH 12Z FRI).
COMPLEX SITUATION WITH CORE OF MAIN WINDS TODAY/THIS EVENING IN THE
SOUTH. WINDS THEN PICK UP OUT OF THE NORTH ON THURSDAY BUILDING
WAVES IN ALL THE MARINE ZONES. WAVES WILL BE UP AT LEAST THROUGH
THURSDAY NIGHT. THE SMALL CRAFT ADVISORY MAY NEED TO BE EXTENDED
INTO FRIDAY.
&&
.HYDROLOGY...(405 PM EST WED NOV 25 2009)
MOST RAINFALL REPORTS SO FAR SEEM TO BE UNDER A HALF INCH. THIS
SHOULD HAVE LITTLE AFFECT ON AREA RIVERS. ADDITIONAL PRECIPITATION
TOTALS WILL LIKELY BE UNDER A QUARTER OF AN INCH IN MOST PLACE THE
NEXT 24 TO 36 HOURS...SO HYDRO ISSUES ARE NOT ANTICIPATED.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY ST. JOSEPH MANISTEE THROUGH THURSDAY NIGHT.
&&
$$
SYNOPSIS: DUKE
SHORT TERM: DUKE
LONG TERM: NJJ
AVIATION: MJS
MARINE: DUKE
HYDROLOGY: DUKE
