000
FXUS63 KGRR 171603
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1203 PM EDT MON JUN 17 2013

LATEST UPDATE...
UPDATE

.SYNOPSIS...
ISSUED AT 335 AM EDT MON JUN 17 2013

A FRONTAL SYSTEM WILL GRADUALLY DROP SOUTH THROUGH THE AREA DURING
THE DAY TODAY AND INTO THE EVENING HOURS. WAVES MOVING ALONG THE
FRONT WILL PRODUCE SCATTERED SHOWERS AND STORMS THROUGH THIS
EVENING. A FEW OF THESE STORMS COULD BECOME STRONG AT TIMES.

THE FRONT IS EXPECTED TO CLEAR THE AREA BY DAYBREAK TUESDAY. COOLER
AND DRIER AIR WILL FILTER IN ACROSS THE AREA. HIGH PRESSURE IS THEN
EXPECTED TO CONTROL THE WEATHER THROUGH MOST OF THE REST OF THE WORK
WEEK. IT IS POSSIBLE A MORE WET AND ACTIVE PATTERN COULD BE SETTING
UP FOR NEXT WEEKEND.

&&

.UPDATE...
ISSUED AT 1202 PM EDT MON JUN 17 2013

STILL EXPECTING SCATTERED CONVECTION THROUGH THE AFTERNOON AND
INTO THE EVENING HOURS. THE MAIN TIME FRAME WOULD BE FROM 300PM TO
1000PM BASED ON HI-RES MODEL SIMULATED REFLECTIVITY. SCATTERED
STORMS ARE ALREADY MOVING INTO THE NORTHERN CWA UP TOWARDS MASON
COUNTY. THERE HAS BEEN SOME LIGHTNING NOTED IN IT. A WEAK COLD
FRONT STRETCHES ACROSS OUR NORTHERN CWA. IT IS A BIT ILL
DEFINED...BUT MOST LIKELY STRETCHES FROM NEAR PENTWATER TO MOUNT
PLEASANT. DEW POINTS SOUTH OF THE FRONT REMAIN IN THE 60S.

FEEL CONVECTION WILL INCREASE A BIT IN COVERAGE THIS AFTERNOON AND
POTENTIALLY EVOLVE TOWARDS MARGINALLY SEVERE LEVELS IN THE LATE
AFTERNOON AND EARLY EVENING. LOW LEVEL MOISTURE IS THE QUESTION
MARK...BUT WITH DEW POINTS NOT MIXING OUT YET AND STILL IN THE 60S
IN THE SOUTH ISOLATED CONVECTION HAS THE POTENTIAL TO BECOME
MARGINALLY SEVERE. IF DEW POINTS REMAIN AROUND 60F OR THE LOW
60S...CAPE VALUES WILL PUSH TO NEAR 2000 J/KG WITH LI/S AROUND
-7C. SO PLENTY ENOUGH INSTABILITY FOR STRONG CONVECTION.

DYNAMICS ARE ALSO IN PLAY HERE WITH A SHORTWAVE DRIFTING EAST-
SOUTHEAST FROM WISCONSIN. A 50+ KNOT MID LEVEL JET IS ALSO IN
PLACE. GIVEN THE STRONGER WINDS IN THE MID LEVELS AND THE
POTENTIAL FOR SOME DRY AIR BELOW CLOUD BASE...DAMAGING WINDS
SHOULD BE THE MAIN THREAT WITH ANY STORMS THAT BECOME STRONG. HAIL
WOULD BE A THREAT AS WELL...BUT SECONDARY. THE RIGHT ENTRANCE
REGION OF A 250MB JET STREAK ALSO DRIFTS BY TOWARD 00Z WHICH MAY
PROVIDE AN UPTICK IN COVERAGE AND INTENSITY.

WILL BE MONITORING STORMS THROUGH THE AFTERNOON FOR CORES ALOFT
THAT COULD PRODUCE SEVERE HAIL/WIND AT THE SURFACE.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 335 AM EDT MON JUN 17 2013

THE MAIN AND REALLY ONLY FOCUS OF THE SHORT TERM PORTION OF THE FCST
IS THE POTENTIAL OF CONVECTION AND THE STRENGTH OF ANY CONVECTION
FROM THIS MORNING THROUGH TONIGHT. THE GENERAL FLAVOR OF THE FCST
REMAINS SIMILAR...WITH JUST A LITTLE LESS EMPHASIS ON THE LAKE
INFLUENCE ON CONVECTIVE POTENTIAL.

SCATTERED SHOWER AND ISOLATED STORM ACTIVITY CONTINUES TO BE ONGOING
EARLY THIS MORNING ACROSS NRN LOWER AND NRN WISCONSIN. THIS PCPN
CONTINUES TO BE DRIVEN BY WEAK/SMALL SHORT WAVES THAT CAN BE SEEN
RIDING
ALONG THE UPPER JET WHICH STRETCHES FROM SE ALBERTA ALL THE WAY
THROUGH THE NERN STATES. THE PCPN HAS SIMMERED DOWN A BIT SINCE
SUNSET WITH THE LOSS OF THE DIURNAL HEATING. IT HAS NOT DISAPPEARED
HOWEVER. THE MORE STABILIZING INFLUENCES OF THE LAKES HAVE NOT HAS
MUCH OF AN IMPACT ON THE PCPN.

THE FCST IS A BIT UNCERTAIN AS TO EXACT PLACEMENT AND TIMING OF PCPN
WAVES. THE SYNOPTIC MODELS CONTINUE TO EMPHASIZE AND FOCUS PCPN
POTENTIAL ON THE WRN UPWIND SIDE OF THE GREAT LAKES. THE MESOSCALE
MODELS SEEM TO BE HANDLING THE PCPN BATCHES A BIT BETTER AS THEY ARE
MAINTAINING THEM OVER THE LAKE AND AFFECTING ALL AREAS MORE
EQUALLY...MUCH CLOSER TO REALITY.

WE CONTINUE TO TREND OF THE FCST IN SHIFTING THE BEST PCPN CHCS
SOUTH FROM THIS MORNING THROUGH THIS EVENING. THIS SHOULD OCCUR AS
THE MAIN SHORT WAVE DIVING SE FROM SE ALBERTA WILL SHIFT THE UPPER
JET AND SHORT WAVE AXIS DOWN SOUTH THROUGH THE PERIOD.

IN BETWEEN THE SHOWERS...WE SHOULD SEE SUNNY PERIODS WHICH WILL HELP
TO DESTABILIZE THE ATMOSPHERE A BIT MORE. SFC BASED LI/S ARE FCST TO
DROP DOWN AT LEAST TO -5 OR -6 WITH THE BEST INSTABILITY AWAY FROM
THE LAKE. THIS WILL BRING THE BEST CHC OF STORMS TO THE ERN AREA.
HIGHS WILL BE IN THE UPPER 70S TO LOWER 80S WITH DEW POINTS WELL
INTO THE 50S TO AROUND 60. THE DECENT MID LEVEL WINDS WILL ALLOW FOR
SOME GOOD DEEP LAYER SHEAR VALUES IN THE 40S. SOME LARGE HAIL IS
POSSIBLE WITH DECENT CAPES IN THE -10 TO -30C LAYER. DAMAGING WINDS
WOULD BE MORE LIKELY DUE TO THE UNIDIRECTIONAL WIND PROFILE
EXPECTED. SOME RESIDUAL PCPN WILL LAST INTO THIS EVENING BEFORE THE
SFC FRONT IS ABLE TO SHIFT SOUTH OF THE AREA AND WE LOSE MORE
DIURNAL HEATING.

THE REMAINDER OF THE FCST FROM LATE TONIGHT THROUGH WED SHOULD BE
FAIRLY QUIET. WILL WILL REMAIN DOWNSTREAM OF THE LONG WAVE UPPER
RIDGE ACROSS THE PLAINS STATES. A COUPLE OF SHORT WAVES WILL TRY TO
DROP DOWN...BUT A DRY ERLY COMPONENT TO THE LOW LEVEL WIND WILL
LIMIT PCPN POTENTIAL OVER THE AREA. H850 TEMPS OF AROUND 9 TO 11C
WILL SUPPORT HIGHS IN THE 70S TUE AND WED.

.LONG TERM...(WEDNESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 335 AM EDT MON JUN 17 2013

AFTER A LONG STRETCH OF QUIET/DRY WEATHER THIS UPCOMING WEEK WITH A
SFC HIGH REMAINING IN CONTROL... THINGS MAY TURN ACTIVE NEXT
WEEKEND.

MEDIUM RANGE GUIDANCE INDICATES A WARM/MOIST/UNSTABLE AIR MASS
PUSHING INTO THE GREAT LAKES REGION FROM THE SOUTHWEST ON
SATURDAY... FEATURING H8 TEMPS AROUND 20C AND SFC DEW POINTS AROUND
70F. MEANWHILE SEVERAL SHORTWAVE IMPULSES WILL BE EJECTING NORTHEAST
OUT OF A TROUGH OVER THE WRN U.S. TOWARD MINNESOTA NEXT WEEKEND.

THESE SHORTWAVES ARE EXPECTED TO LEAD TO MCS DEVELOPMENT OVER NRN MN
AND WI WHICH SHOULD THEN TRACK SEWD ACROSS THE GREAT LAKES REGION
AROUND THE OUTER EDGE OF A STRONG 592 UPPER LEVEL HIGH CENTERED OVER
MISSOURI. PROGGED ORIENTATION OF 850-300 MB THICKNESSES WOULD EVEN
IMPLY SOUTHWARD PROPAGATING MCS/S FOR SATURDAY AND SATURDAY NIGHT
OVER THE UPPER MIDWEST/GRTLKS REGION.

ONE BIG QUESTION FOR NEXT WEEKEND WILL BE WHERE THE SFC BOUNDARY
ENDS UP BECOMING ORIENTED. INITIALLY IT APPEARS THE WARM FRONT WILL
BE WELL NORTH OF US ON SATURDAY... BUT MCS ACTIVITY SATURDAY NIGHT
COULD FORCE THAT BOUNDARY SOUTH TO BE EITHER ON TOP OF US OR EVEN
SOUTH OF US FOR SUNDAY. EITHER WAY... ADDITIONAL SHOWERS AND TSTMS
WILL BE POSSIBLE... BUT TEMPERATURES COULD BE HELD DOWN ON SUNDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 754 AM EDT MON JUN 17 2013

VFR CONDITIONS WILL PREVAIL TODAY WITH CLOUD BASES MOSTLY AT OR
ABOVE 8000 FT. THE MAIN CONCERN FOR THE AVIATION COMMUNITY IS THE
POTENTIAL OF ISOLATED TSTMS WITH BRIEFLY STRONG WIND GUSTS LATER
THIS AFTERNOON AND THIS EVENING.

BELIEVE THE MAIN TSTM THREAT IS GOING TO HOLD OFF UNTIL AFTER 21Z
BUT COVERAGE OF STORMS WILL BE ONLY WIDELY SCATTERED. THE PROBLEM
IS THAT A FEW OF THE STORMS BETWEEN 21Z-03Z COULD BE STRONG
ENOUGH TO PRODUCE WIND GUSTS OVER 40 KTS AND PERHAPS HAIL UP TO
ONE INCH IN DIAMETER. THE PROBABILITY OF A TERMINAL BEING IMPACTED
IS QUITE LOW... HOWEVER THE THREAT DOES EXIST.

THE PASSAGE OF THE SFC COLD FRONT AFTER 03Z FROM NORTH TO SOUTH
WILL SHIFT THE WINDS FROM WESTERLY TO NORTHERLY AND MAY RESULT IN
A 6 HOUR PERIOD OF MVFR CIGS RIGHT BEHIND THE FRONT. THE TSTM
THREAT IS EXPECTED TO END WITH THE PASSAGE OF THE FRONT... HOWEVER
THE FRONT MAY NOT CLEAR THE I-94 CORRIDOR REGION UNTIL AFTER 06Z.


&&

.MARINE...
ISSUED AT 335 AM EDT MON JUN 17 2013

WE CONTINUE TO EXPECT THAT WINDS AND WAVES WILL BE UP A LITTLE
THROUGH TONIGHT. EVEN WITH WINDS AND WAVES UP A LITTLE...WE EXPECT
NO HEADLINES WILL BE NEEDED FOR THE TIME BEING. WINDS WILL BE
HIGHEST UP NORTH WERE SOME 15 TO 20 KNOT WINDS WILL BE MORE LIKELY.
WINDS WILL GRADUALLY SWITCH TO NRLY TONIGHT AND EVEN NE BY TUE.


&&

.HYDROLOGY...
ISSUED AT 335 AM EDT MON JUN 17 2013

WE DO NOT EXPECT ANY SIGNIFICANT OR WIDESPREAD HYDROLOGY ISSUES
THROUGH THIS WEEK. SHOWERS AND STORMS LOOK TO BE RATHER SCATTERED
THROUGH THIS EVENING. THE TRUE DEEP MOISTURE IS LOCKED UP WELL SOUTH
OF THE STATE. LOCALLY HEAVY DOWNPOURS WILL BE POSSIBLE...BUT THEY
WILL NOT BE THE TROPICAL LIKE DOWNPOURS. AREA RIVERS AND STREAMS ARE
RUNNING HIGH...BUT CURRENT FCST WITH SAT NIGHT/S RAIN AND THE FCST
TODAY KEEP MOST RIVERS BELOW BANKFULL STAGE.

WE ARE MONITORING THE POSSIBILITY OF A MORE WET AND ACTIVE PATTERN
AT LEAST NEXT WEEKEND. WE COULD BE LOOKING AT A STALLED OUT FRONTAL
BOUNDARY WITH MCS ACTIVITY RIDING ALONG IT AND BEING FED BY A VERY
WARM AND HUMID AIR MASS JUST SOUTH OF IT. PLENTY OF TIME TO MONITOR
THIS.

&&

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

$$

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