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000
FXUS63 KGRR 140425
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1225 AM EDT TUE MAY 14 2013

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 214 PM EDT MON MAY 13 2013

HIGH PRESSURE CENTERED OVER LOWER MICHIGAN WILL PUSH EAST OF THE
STATE TONIGHT. A SOUTHWEST FLOW OF WARMER AIR WILL DEVELOP AND
PERSIST ACROSS THE REGION INTO WEDNESDAY. THE WEATHER COULD BE
UNSETTLED UNTIL A COLD FRONT SWINGS THROUGH EARLY WEDNESDAY. A
WEAK AREA OF HIGH PRESSURE BUILDS IN FOR THURSDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 214 PM EDT MON MAY 13 2013

THE MAIN CHALLENGE IN THE SHORT TERM DEALS WITH THE POTENTIAL FOR
SHOWERS TONIGHT INTO WEDNESDAY.

THE PERIOD LOOKS MAINLY DRY...HOWEVER SEVERAL ROUNDS OF SHOWERS
ARE POSSIBLE. THE FIRST ARRIVES AFTER MIDNIGHT TONIGHT. THIS IS
WHEN A MID LEVEL WAVE AND ASSOCIATED WARM AIR ADVECTION MOVES IN.
MOISTURE IS LIMITED...ESPECIALLY BELOW 700 MB. HOWEVER THERE IS
WEAKNESS IN THE STABILITY AND BETTER RH ABOVE 700 MB. THIS AREA OF
SHOWERS WILL LIKELY MOVE EAST SOUTHEAST OUT OF WI.

A SECOND ROUND OF SHOWERS AND EVEN A FEW THUNDERSTORMS WILL BE
POSSIBLE TUESDAY NIGHT INTO EARLY WED. A STRONGER LOW LEVEL JET
MOVES IN AND BETTER INSTABILITY WILL EXIST. WHILE LOW LEVEL
PARCELS WILL BE VERY UNSTABLE...THEY WILL BE CAPPED. LESS OF A CAP
EXISTS FOR LIFTED PARCELS ABOVE 700 MB...AND THERE IS THIN CAPE
THROUGH THE -20 DEG C LEVEL. SO THUNDER IS LIKELY WITH ANY AREA OF
PRECIPITATION. THE THOUGHT IS THAT WHEN THE LOW LEVEL MOVES IN
MAINLY AFTER MIDNIGHT...THE ELEVATED CONVECTION SHOULD ACCOMPANY
THIS FEATURE. THE GFS IS HOLDING BACK SOME INSTABILITY FOR WED
AM...SO I WILL KEEP A LOW POP GOING THEN. OTHERWISE...HIGHEST POPS
WILL BE FOR TUE NIGHT.

GUSTY WINDS LIKELY FOR WED AS DRYING MOVES IN FROM THE WEST. I DID
LOWER TEMPERATURES SLIGHTLY CLOSER TO THE LAKESHORE DUE TO THE
ONSHORE FLOW.

.LONG TERM...(THURSDAY THROUGH MONDAY)
ISSUED AT 214 PM EDT MON MAY 13 2013

THE END OF THE WORK WEEK WILL BE DOMINATED BY HIGH PRESSURE.  EXPECT
MAINLY DRY CONDITIONS THURSDAY AND FRIDAY.  THIS SHOULD BE A DRY AIR
MASS WITH LARGE DIURNAL TEMP SWINGS.  THEREFORE INCREASED MAX TEMP
FOR THU...BUT LOWERED THE MIN FOR THU NIGHT.

THE REST OF THE EXTENDED PERIOD...FROM FRIDAY NIGHT THROUGH MONDAY
LOOKS UNSETTLED.  AN UPPER RIDGE OVER THE EASTERN U.S WILL GRADUALLY
WEAKEN.  DEPENDING ON HOW QUICKLY THIS OCCURS WILL DICTATE WHEN
PCPN CHCS ARRIVE...SOMETIME BETWEEN FRI NIGHT AND SATURDAY NIGHT.
AS THE RIDGE WEAKENS A LONG WAVE TROUGH OVER THE WESTERN U.S.
SLOWLY ADVANCES EAST.  AHEAD OF THIS WAVE GULF MOISTURE WILL FLOW
FREELY TOWARD THE GREAT LAKES.  A WARM FRONT SHOULD ALSO BE IN THE
VICINITY HELPING CREATE SHOWERS AND STORMS.  THIS PATTERN HOLDS INTO
MONDAY.  AS A GENERAL RULE...WE SHOULD SEE AN INCREASE IN THE PCPN
COVERAGE THROUGH THE WEEKEND AND INTO MONDAY AS THE UPPER TROUGH
GETS CLOSER AND THE GULF MOISTURE DEEPENS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1225 AM EDT TUE MAY 14 2013

VFR CONDITIONS WILL PREVAIL OVERNIGHT AND TUESDAY. CONFIDENCE
LEVEL IS HIGH. CIGS WILL BE MOSTLY AOA 8K FEET OVERNIGHT AND MOST
OF THE SCATTERED SHOWERS WILL NOT EVEN REACH THE GROUND. IF THEY
DO REACH THE GROUND THEY SHOULD HAVE LITTLE OR NO IMPACT ON VSBYS.
LIGHT SFC WINDS TONIGHT WILL BECOME SOUTHERLY AT 10 TO 20 KNOTS ON
TUESDAY. A FEW TSTMS COULD DEVELOP AROUND MKG AND GRR TOWARD 06Z
WEDNESDAY BUT CONFIDENCE IS CURRENTLY LOW.

&&

.MARINE...
ISSUED AT 214 PM EDT MON MAY 13 2013

WAVES OF 3 TO 4 FEET WILL DEVELOP CLOSER TO LITTLE AND BIG SABLE
POINTS TONIGHT AS THE SOUTHERLY FLOW STRENGTHEN. COULD TURN INTO A
SMALL CRAFT ADVISORY EVENT. WINDS AND WAVES WILL DIMINISH SOMEWHAT
TUESDAY AS PRESSURE GRADIENT WEAKENS.


&&

.FIRE WEATHER...
ISSUED AT 214 PM EDT MON MAY 13 2013

WILL NEED TO MONITOR WEDNESDAY FOR POSSIBLE ELEVATED FIRE DANGER
RISK. DRYING WARM AIR MASS AND GUSTY WIND ARE THE MAIN CONCERNS.

&&

.HYDROLOGY...
ISSUED AT 214 PM EDT MON MAY 13 2013

LIMITED RAINFALL THROUGH THURSDAY WILL RESULT IN WATER LEVELS
REMAINING STEADY OR SLOWLY FALLING.

&&

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

$$

SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...JK
AVIATION...MEADE
FIRE WEATHER...MJS
HYDROLOGY...MJS
MARINE...MJS