000
FXUS63 KGRR 151150
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
750 AM EDT SAT JUN 15 2013

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 328 AM EDT SAT JUN 15 2013

AN AREA OF LOW PRESSURE SOUTH AND WEST OF THE AREA WILL GRADUALLY
APPROACH THE AREA THROUGH TONIGHT. THIS WILL GRADUALLY INCREASE THE
CHANCES FOR RAIN THROUGH THIS EVENING. OVERNIGHT TONIGHT WE EXPECT
THAT MOST LOCATIONS WILL SEE SHOWERS AND A FEW STORMS MOVE THROUGH.
SEVERE WEATHER IS NOT EXPECTED AT THIS TIME.

ANY RESIDUAL SHOWERS EARLY SUNDAY MORNING WILL MOVE OUT BY SUNDAY
AFTERNOON AND CLEARING WILL TAKE PLACE. MILD TEMPERATURES WILL
CONTINUE TO BE FOUND ACROSS THE AREA. ANOTHER FRONTAL SYSTEM WILL
DROP SOUTH THROUGH THE AREA ON MONDAY. THIS WILL PRODUCE ANOTHER
CHANCE OF SHOWERS AND A FEW STORMS.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 328 AM EDT SAT JUN 15 2013

MAIN FCST ISSUE IN THE SHORT TERM PORTION OF THIS FCST PACKAGE IS
THE RAIN CHCS TODAY THROUGH EARLY SUN. LATEST MODEL TRENDS INDICATE
THAT THE CHC OF RAIN IS A LITTLE BETTER TODAY THAN WHAT WAS
PREVIOUSLY EXPECTED. OTHERWISE THE FCST GENERALLY REMAINS SIMILAR.

WE HAVE INCREASED THE CHC OF RAIN A BIT FOR THE DAY TODAY...ALTHOUGH
A BIT OF UNCERTAINTY REMAINS SURROUNDING THE EVOLUTION OF THE RAIN.
PLENTY OF SHOWERS AND STORMS ARE CURRENTLY OCCURRING ACROSS
WISCONSIN AND IOWA AS OF 07Z. ALL OF THIS PCPN IS OCCURRING AT THE
NOSE OF THE LLJ AND AT THE LEADING EDGE OF THE BETTER MOISTURE
TRANSPORT. WITH THE UPPER RIDGE AXIS STILL WEST OF OUR AREA...THE
GENERAL MOVEMENT OF THE CONVECTION IS NW TO SE. THE GENERAL
EXPECTATION WITH ALL OF THE CONVECTION TO OUR WEST IS THAT IT SHOULD
LIKELY STAY WEST OF THE CWFA AND SHOW A DIMINISHING TREND AS THE LLJ
WILL UNDERGO ITS TYPICAL WEAKENING AS WE APPROACH DAYBREAK.

THERE ARE A FEW SPRINKLES FALLING OUT OF A MID DECK MOVING IN FROM
NRN LAKE MICHIGAN...AND WE HAVE ACCOUNTED FOR THESE IN THE FCST
FIRST THING THIS MORNING. WE EXPECT A LULL IN THE ACTIVITY FROM
AROUND DAYBREAK THROUGH MOST OF THE MORNING.

THE UNCERTAINTY SHOWS UP FOR THE AFTERNOON HOURS. THE LOWER
RESOLUTION MODELS INDICATE WE SHOULD NOT SEE MUCH PCPN THROUGH THE
AFTERNOON HOURS AS THEY ALL WAIT FOR THE LLJ TO RAMP BACK UP TONIGHT
AND BRING OUR SOAKING RAIN AT THAT TIME. THE HIGHER RESOLUTION
MESOSCALE MODELS ARE INDICATING A VORT COMING OUT OF IOWA AND
REIGNITING SOME SHOWERS ACROSS THE SRN THIRD OF THE CWFA TOWARD AND
AFTER 18Z THIS AFTERNOON. WE ARE NOT CONFIDENT ON THIS FEATURE
REIGNITING WIDESPREAD SHOWERS. HOWEVER WE HAVE TRENDED THE CHCS UP A
BIT TO TAKE IT INTO ACCOUNT. IF THESE SHOWERS DO COME TO
FRUITION...TEMPS WILL OBVIOUSLY BE HELD DOWN. ELSEWHERE...A FEW
SPOTTY SHOWERS/ISOLATED STORMS COULD DEVELOP AS SOME RESIDUAL
MOISTURE TRANSPORT MAKES ITS WAY INTO THE CWFA TODAY.

MODELS ARE IN PRETTY GOOD AGREEMENT CONCERNING A FAIRLY WIDESPREAD
RAINFALL FOR TONIGHT ACROSS MOST OF THE AREA. THIS WILL OCCUR AS JET
ENERGY/A SHORT WAVE ACROSS WY THIS MORNING WILL APPROACH THE AREA
AFTER 00Z TONIGHT. THIS TAKES PLACE AS THE UPPER RIDGE TO OUR WEST
GETS FLATTENED BY UPPER ENERGY ACROSS CANADA AND THEN DIRECTS THE WY
SHORT WAVE TOWARD THE HEART OF THE CWFA. WE WILL SEE THE LLJ RAMP UP
AND HELP TO DEVELOP SHOWERS AND A FEW EMBEDDED STORMS AND MOVE THEM
ACROSS THE CWFA.

FCST SOUNDINGS CONTINUE TO INDICATE THAT INSTABILITY WILL BE RATHER
WEAK IN NATURE. THIN CAPE PROFILES WILL LIMIT THE UPDRAFT STRENGTH
AND THEREFORE LIMIT THE SEVERE WX POTENTIAL FOR THE CWFA. DEEP LAYER
SHEAR VALUES OF 30-40 KNOTS ARE DECENT...BUT AGAIN INSTABILITY
SHOULD BE A BIG LIMITING FACTOR.

THE LLJ AND SHORT WAVE WILL BE EXITING THE CWFA AROUND 12Z SUN.
THERE WILL BE A RESIDUAL CHC OF A FEW SHOWERS EARLY SUN MORNING. THE
SFC FRONT WILL CLEAR THE AREA BY AFTERNOON AND WE SHOULD SEE
CLEARING SKIES AND DRY CONDITIONS. SOME DIURNAL INSTABILITY IS
PRESENT ON SUN...HOWEVER WE SHOULD BE UNDER THE INFLUENCE OF SHORT
WAVE RIDGING IN THE WAKE OF THE DEPARTING SHORT WAVE TROUGH...AND
WELL AHEAD OF THE NEXT WAVE EXPECTED TO MOVE IN ON MON.

A SECONDARY FRONT WILL PUSH THROUGH THE AREA ON MON AS A SHORT WAVE
DIVES SE OUT OF SOUTH CENTRAL CANADA. THE MODELS ARE ALL INDICATING
THAT THE LOCATIONS WEST OF EACH OF THE GREAT LAKES WILL SEE THE BEST
CHC OF RAIN ON MON. THIS IS THE CASE AS A WEAK PRESSURE GRADIENT
WILL ALLOW FOR MAXIMIZED LAKE BREEZE CONVERGENCE TO OCCUR AT THOSE
LOCATIONS. ALSO...STABILIZING EFFECTS FROM THE COOLER LAKE MICHIGAN
WATERS WITH A WRLY FLOW WILL LIMIT THE CONVECTION POTENTIAL OVER THE
WRN PORTION OF THE CWFA.

.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 328 AM EDT SAT JUN 15 2013

COOL AND DRY SURFACE HIGH PRESSURE WILL BUILD INTO THE GREAT LAKES
REGION TUESDAY BEHIND THE COLD FRONT WHICH PASSES THROUGH ON MONDAY
EVENING. THE SURFACE HIGH STICKS AROUND MOST OF NEXT WEEK PROVIDING
DRY AND PLEASANT WEATHER... THEN SLIPS AWAY TOWARD THE END OF THE
WEEK.

RETURNING WARM ADVECTION ON FRIDAY COULD LEAD TO A FEW SHOWERS AND
TSTMS... BUT CONFIDENCE IS LOW REGARDING THE TIMING AND STRENGTH OF
THE INCOMING WARM FRONT THAT FAR OUT.

BELOW NORMAL BUT COMFORTABLE TEMPERATURES ARE EXPECTED TUESDAY AND
WEDNESDAY WITH READINGS MODERATING TO NEAR OR SLIGHTLY ABOVE NORMAL
ON THURSDAY AND FRIDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 750 AM EDT SAT JUN 15 2013

CONFIDENCE IS HIGH THAT VFR CONDITIONS WILL CONTINUE THROUGH AT
LEAST 18Z AS THE INCOMING CLOUD DECK HAS BASES ABOVE 8000 FT AND
IS ONLY PRODUCING LIGHT SHOWERS/SPRINKLES. EVENTUALLY MVFR
CONDITIONS ARRIVE TOWARD 00Z AS SHOWERS BEGIN TO INCREASE IN
COVERAGE/INTENSITY AND THE CIGS LOWER.

WHILE A FEW TSTMS CANNOT BE RULED OUT THIS AFTERNOON... HAVE
OPTED TO HIGHLIGHT THE 00Z-06Z TIME FRAME AS THE OPTIMAL TIME FOR
TSTMS ACROSS SRN LWR MI. THAT IS BASED ON THE EXTRAPOLATION OF THE
TSTM COMPLEX CURRENTLY OVER NEBRASKA THIS MORNING.

EVEN AFTER TSTMS EXIT THE REGION LATE TONIGHT AROUND 09Z...
SHOWERS AND MVFR CONDITIONS WILL LINGER.

&&

.MARINE...
ISSUED AT 328 AM EDT SAT JUN 15 2013

WE WILL SEE AN INCREASE IN WIND LATER TODAY AND TONIGHT AHEAD OF THE
INCOMING SYSTEM. THERE IS SOME DECENT WIND ALOFT /20-25 KNOTS/ WITH
THE WIND CORE AT 2-4K FEET. INDICATIONS ARE THAT WE WILL NOT MIX
THIS DOWN OVER THE MORE STABLE LAKE AND CONDITIONS WILL STAY BELOW
ADVISORY. WE WILL GO WITH THIS IDEA FOR NOW...BUT CONTINUE TO
MONITOR FOR HIGHER POSSIBLE WINDS/WAVES.


&&

.HYDROLOGY...
ISSUED AT 328 AM EDT SAT JUN 15 2013

CONDITIONS ARE STABILIZING ON THE AREA RIVERS AND STREAMS AFTER A
FEW DAYS SINCE THE HEAVY RAINFALL ON WED NIGHT. THE CREST IS MAKING
ITS WAY DOWN THE GRAND. THE CONCERN NOW IS ADDING A BIT OF RAIN
EXPECTED ACROSS THE AREA FOR TONIGHT.

MODELS CONTINUE TO INDICATE THAT BASIN AVERAGES SHOULD END UP WITH
HALF AN INCH TO MAYBE AN INCH OF RAINFALL TONIGHT WITH THE WAVE OF
LOW PRESSURE. PWATS ARE EXPECTED TO INCREASE TO AROUND 1.75 INCHES
OR SO BY TONIGHT...WHICH WOULD SUPPORT SOME LOCALLY HEAVY DOWNPOURS
AND LOCALLY HIGHER AMOUNTS. THIS WILL ONLY INCREASE THE FLOWS/LEVELS
ON THE RIVERS. WE COULD SEE A COUPLE OF LOCATIONS APPROACH FLOOD
LEVELS...HOWEVER IT SEEMS MORE LIKELY THAT WE WILL EVENTUALLY NEED
ADDITIONAL ADVISORIES IN ADDITION TO THE FIVE ALREADY IN EFFECT.

&&

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

$$

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