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000
FXUS63 KGRR 131919
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
319 PM EDT MON MAY 13 2013

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

.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 INSTABILTY 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 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 106 PM EDT MON MAY 13 2013

VFR CONDITIONS ARE EXPECTED TO CONTINUE OVER THE NEXT 24 HOURS.
THERE WILL BE A WARM FRONT THAT WILL MOVE INTO THE REGION LATE
TONIGHT. THE FRONT WILL BRING CEILINGS OF 5-7K FT ALONG WITH A
FEW RAIN SHOWERS. THESE SHOWERS ARE EXPECTED TO REMAIN LIGHT...
WITH NO RESTRICTION TO VSBYS. THE SHOWERS ARE EXPECTED TO MOVE OUT
OF THE REGION TOWARD MID DAY TUE.

WESTERLY WINDS THIS AFTERNOON WILL BE A BIT BRISK...IN THE 10 TO
15 KNOT RANGE. THESE WILL DIMINISH BY SUNSET. A BRISK SOUTHERLY
WIND IS EXPECTED TO DEVELOP EARLY TUE MORNING...AGAIN MAINLY 10 TO
15 KNOTS.


&&

.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 AIRMASS 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...JK
FIRE WEATHER...MJS
HYDROLOGY...MJS
MARINE...MJS