Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 171924
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
324 PM EDT WED SEP 17 2014

LATEST UPDATE...
SYNOPSIS/SHORT TERM/LONG TERM/HYDRO/MARINE

.SYNOPSIS...
ISSUED AT 324 PM EDT WED SEP 17 2014

A COLD FRONT WILL MOVE SOUTH FROM CANADA TONIGHT. WE/LL SEE THE
CLOUDS INCREASE AS THE FRONT APPROACHES AND THERE COULD ALSO BE A
BRIEF PERIOD OF DRIZZLE TOWARD MORNING. SKIES WILL BECOME MOSTLY
SUNNY THURSDAY AS HIGH PRESSURE BUILDS OVER LOWER MICHIGAN. CLEAR
SKIES AND LIGHT WINDS WILL RESULT IN CHILLY TEMPERATURES THURSDAY
NIGHT AND FROST MAY BE POSSIBLE NORTHEAST OF GRAND RAPIDS.

RAIN IS EXPECTED FRIDAY NIGHT AND EARLY SATURDAY BUT TEMPERATURES
WILL WARM INTO THE MID TO PERHAPS UPPER 70S SATURDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY NIGHT)
ISSUED AT 324 PM EDT WED SEP 17 2014

FORECAST CONCERNS DEAL WITH FROST POTENTIAL THURSDAY NIGHT AND RAIN
CHANCES FRIDAY NIGHT.

A COLD FRONT MOVING SOUTH FROM CANADA TONIGHT WILL SET THE STAGE FOR
A CHILLY THURSDAY NIGHT. HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THE FRONT AND CLEAR OUT THE CLOUDS. LIGHT WINDS WILL ALLOW TEMPS TO
FALL THURSDAY NIGHT INTO THE MID 30S NORTHEAST OF GRAND RAPIDS.
ADDED SOME FROST TO THE GRIDS AND WENT A DEGREE OR TWO BELOW
GUIDANCE. THERE IS SOME CONCERN THAT THE HIGH WILL MOVE EAST QUICK
ENOUGH TO ALLOW LIGHT SOUTH WINDS TO DEVELOP BEFORE SUNRISE FRIDAY
MORNING...SO WE HELD OFF ON A FROST ADVISORY AT THIS POINT.

LOW PRESSURE MOVING EAST FROM THE PLAINS LATE FRIDAY WILL PUSH A
WARM FRONT NORTH THROUGH THE CWA. MOISTURE TRANSPORT VECTORS
LENGTHEN QUITE A BIT FRIDAY NIGHT...ESPECIALLY AFTER 06Z WHEN PWATS
CLIMB TO AROUND 1.7 INCHES OVER THE NW CWA. LOCALLY HEAVY RAINFALL
SEEMS POSSIBLE AFTER MIDNIGHT FRIDAY NIGHT NW OF A GRAND HAVEN TO
CLARE LINE. TSRA CHANCES ARE HIGHER AFTER MIDNIGHT THAN BEFORE DUE
TO GROWING ELEVATED INSTABILITY. INCREASED POPS TO LIKELY DURING
THIS TIMEFRAME.

IN THE MEANTIME...THE FRONT THAT MOVES SOUTH TONIGHT WILL BRING SOME
CLOUDS WITH IT. BUFKIT DATA SHOWED SOME LIFT IN THE CLOUD LAYER FOR
A SHORT TIME FROM AROUND 09-13Z...SO SOME -DZ MAY BE POSSIBLE.

.LONG TERM...(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 324 PM EDT WED SEP 17 2014

SOMEWHAT TRICKY HIGH TEMPERATURE FCST ON SATURDAY DUE TO LOW
CONFIDENCE IN EXTENT OF CLOUDS AND CONVECTION. BEHAVIOR OF THE LOW
LEVEL JET IS STILL UNCLEAR. THE HIGHEST POTENTIAL FOR SHOWERS/TSTMS
WOULD APPEAR TO BE NORTH AND WEST OF GRR CLOSER TO THE APPROACHING
SFC COLD FRONT. WILL HAVE HIGHS IN THE LOW TO MID 70S ACROSS THIS
AREA WHICH IS ALSO WHERE THE STRONG LOW LEVEL SOUTHWEST FLOW OFF
LAKE MICHIGAN WILL BE OCCURRING. SOUTH AND EAST OF GRR HOWEVER HIGHS
MAY REACH 80 ON SATURDAY AWAY FROM THE LAKE INFLUENCE IF CLOUDS AND
CONVECTION ARE NOT PARTICULARLY WIDESPREAD.

THE COLD FRONTAL PASSAGE IS STILL ON TRACK FOR SATURDAY NIGHT WITH
GRADUAL COLD ADVECTION FOLLOWING IN ITS WAKE SUNDAY AND MONDAY. THE
COLD ADVECTION BEHIND THE FRONT MAY SUPPORT SOME SCATTERED RAIN
SHOWERS ALTHOUGH SFC RIDGING/ANTICYCLONIC FLOW IS RATHER QUICK TO
BUILD INTO THE REGION ON MONDAY. THIS IS A LIMITING FACTOR FOR LAKE
EFFECT/ENHANCED RAIN SHOWERS IN THE COLDER AIR.

FAIRLY HIGH CONFIDENCE IN DRY WEATHER WITH MODERATING TEMPS TUESDAY
AND WEDNESDAY AS LARGE/SLOW MOVING SFC HIGH IMPACTS THE REGION.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 143 PM EDT WED SEP 17 2014

VFR CONDITIONS ARE EXPECTED TO CONTINUE THIS AFTERNOON INTO
TONIGHT. HOWEVER THE PASSAGE OF A SFC COLD FRONT FROM NORTH TO
SOUTH VERY LATE TONIGHT AND EARLY THURSDAY MORNING WILL BRING A
FEW HOURS OF MVFR AND POSSIBLY IFR CIGS FROM ROUGHLY 10Z TO 16Z
THURSDAY.

THE HIGHEST CONFIDENCE FOR LOWER IFR/MVFR CIGS EXISTS AT LAN AND
JXN... WITH LESSER POTENTIAL/CONFIDENCE FARTHER WEST AND SOUTH AT
THE GRR/MKG/AZO/BTL TERMINALS. CIGS SHOULD IMPROVE AGAIN TO VFR BY
18Z THURSDAY AS THE BAND OF STRATUS BEHIND THE COLD FRONT LIFTS
AND BEGINS TO SCATTER OUT.

WEST SFC WINDS OF 10 KTS OR LESS WILL BECOME NORTHEASTERLY BEHIND
THE SFC COLD FRONT AFTER 09Z THURSDAY AND REMAIN 10KTS OR LESS.


&&

.MARINE...
ISSUED AT 324 PM EDT WED SEP 17 2014

A COLD FRONT WILL DROP SOUTH FROM CANADA TONIGHT. WINDS WILL SHIFT
TO THE NORTHEAST AFTER MIDNIGHT AND INCREASE TO 10 TO 20 KNOTS.
GIVEN THE NORTHEAST FLOW BEHIND THE FRONT...HIGHEST WAVES SHOULD
REMAIN OVER THE OPEN WATER. HOWEVER...IF WINDS ARE A BIT MORE
NORTHERLY...WAVES MAY APPROACH SCA CRITERIA NEAR THE POINTS NORTH OF
WHITEHALL. OPTED TO NOT GO WITH A SCA AT THIS TIME AS WE EXPECT 2 TO
4 FOOTERS TO DEVELOP LATE TONIGHT. WAVES WILL BE ON THE DECREASE BY
MID MORNING THURSDAY.

WAVES WILL INCREASE AGAIN LATE FRIDAY AS SOUTH FLOW DEVELOPS AHEAD
OF THE APPROACHING LOW. A SCA MAY BE NEEDED FRIDAY NIGHT/SATURDAY.

&&

.HYDROLOGY...
ISSUED AT 324 PM EDT WED SEP 17 2014

THE NEXT CHANCE OF RAIN WILL COME FRIDAY NIGHT AND EARLY SATURDAY AS
LOW PRESSURE MOVES EAST FROM THE NORTHERN PLAINS TOWARD THE GREAT
LAKES. MOISTURE TRANSPORT VECTORS INCREASE QUITE A BIT FRIDAY NIGHT
AS INSTABILITY ALSO RISES AFTER MIDNIGHT. WE COULD SEE SOME LOCALLY
HEAVY RAINFALL WITH SHOWERS AND THUNDERSTORMS...ESPECIALLY AFTER
MIDNIGHT.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
&&

$$

SYNOPSIS...93
SHORT TERM...93
LONG TERM...MEADE
AVIATION...MEADE
HYDROLOGY...93
MARINE...93









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