AP-MI--GRR-MI W Cntrl Area Forecast Discussion, MI

000

FXUS63 KGRR 151131

AFDGRR

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE GRAND RAPIDS MI

731 AM EDT WED JUL 15 2015

LATEST UPDATE...

MARINE

.SYNOPSIS...

ISSUED AT 250 AM EDT WED JUL 15 2015

CANADIAN HIGH PRESSURE WILL TRACK SOUTHEASTWARD THROUGH THE GREAT

LAKES REGION TODAY THROUGH THURSDAY. THIS SYSTEM WILL ACT TO KEEP

TEMPERATURES COOLER THAN NORMAL AND THE WEATHER DRY. A WARM FRONT

WILL LIFT INTO THE AREA THURSDAY NIGHT AND REMAIN ACROSS THE

REGION INTO FRIDAY. AS A RESULT...SHOWERS AND THUNDERSTORMS COULD

RETURN.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)

ISSUED AT 250 AM EDT WED JUL 15 2015

THE MAIN CHALLENGE IN THE SHORT TERM DEALS WITH THE POTENTIAL FOR

RAIN THURSDAY NIGHT INTO FRIDAY AND WHETHER WE WILL SEE ANY SEVERE

THUNDERSTORMS.

DEEP LAYER SHEAR IS FORECASTED TO BE SUFFICIENT FOR ORGANIZED

CONVECTION. LOW LEVEL JET MOVES IN DRAWING THE WARM FRONT INTO THE

AREA. ALOFT DIFFLUENCE EXISTS. LOW LEVEL INSTABILITY PARAMETERS

SUGGEST THE CONVECTION WILL BE FAIRLY ELEVATED...ABOVE 850 MB

THROUGH MUCH OF THU NIGHT. GENERALLY THIS KEEPS THE RISK FOR

SEVERE WEATHER LOW. LATER AT NIGHT...AS STRONGER MOISTURE

ADVECTION CONTINUES...WE SEE MORE FAVORABLE INSTABILITY ARRIVING.

THUS IS APPEARS THAT THE MOST FAVORABLE PERIOD FOR ORGANIZED

CONVECTION WILL BE AFTER 06Z. WHILE MODEL QPF PARAMETERS SUGGEST

THE HEAVIEST RAIN WILL BE NORTH OF THE CWA...THIS SUMMER THE

PATTERN HAS BEEN FOR THE STORMS TO BE FURTHER SOUTH OF WHAT THE

MODELS HAVE GENERALLY SHOW.

I WILL KEEP THE POPS HIGH FOR THU NIGHT ESPECIALLY FOR NORTHWEST

PARTS OF THE CWA. I WILL MENTION ISOLATED SEVERE POSSIBLE IN THE

HAZARDOUS WEATHER OUTLOOK. THE LOW LEVEL JET IS SHOWN TO BE OFF TO

THE EAST FRIDAY SO THE RISK FOR STRONGER CONVECTION APPEARS LOW.

.LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY)

ISSUED AT 250 AM EDT WED JUL 15 2015

VERY WARM AND HUMID WX IS ANTICIPATED FRIDAY NIGHT THROUGH MONDAY

WITH MAX TEMPS DAILY GENERALLY IN THE 85 TO 90 DEGREE RANGE. A

CONSENSUS OF LATEST MEDIUM RANGE GUIDANCE ALSO CONTINUES TO SUGGEST

POTENTIAL FOR SEVERAL ROUNDS OF SHOWERS AND THUNDERSTORMS. A LOW

PRESSURE WAVE ALONG A QUASI STATIONARY BOUNDARY WILL BRING POTENTIAL

FOR SHOWERS AND STORMS INTO FRIDAY NIGHT.

A BOUNDARY IN THE AREA THIS WEEKEND WILL PROVIDE THE FOCUSING

MECHANISM FOR CONTINUED POTENTIAL FOR SEVERAL ROUNDS OF SHOWERS AND

THUNDERSTORMS WITH THE PATTERN FAVORING ONE OR SEVERAL MCS/S IN OUR

REGION. THERE IS POTENTIAL FOR MODERATE TO STRONG INSTABILITY TO

DEVELOP LATE FRIDAY RIGHT THROUGH THE WEEKEND.

A COLD FRONT WILL BRING POTENTIAL FOR MORE SHOWERS AND STORMS

MONDAY. A WX PATTERN CHANGE SHOULD THEN FINALLY OCCUR BEHIND THAT

FRONT FOR TUESDAY THROUGH THE MIDDLE OF NEXT WEEK AS A COOLER AND

DRIER AIRMASS MOVES IN.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)

ISSUED AT 549 AM EDT WED JUL 15 2015

WITH HIGH PRESSURE BUILDING INTO THE REGION...THIS WILL ACT TO

KEEP THE CLOUD COVER TO A MINIMUM. THE DRY AIRMASS MOVING IN WILL

SUPPORT VFR WEATHER. THE PRESSURE GRADIENT WEAKENS OVER TIME...SO

THE WIND WILL GENERALLY DECREASE FROM THIS MORNING INTO TONIGHT. A

GENERAL NORTHEAST FLOW IS FORECASTED. THERE IS A SMALL RISK FOR

COME DIURNAL CLOUDS TO DEVELOP SHORTLY AFTER SUNRISE...BUT THEY

SHOULD DISSIPATE BY 18Z.

&&

.MARINE...

ISSUED AT 729 AM EDT WED JUL 15 2015

EXTENDED THE MWW AND CFW FOR THE SOUTHERNMOST ZONE. WAVES SOUTH OF

SOUTH HAVEN STILL ABOVE 4 FEET SO HAZARDOUS CONDITIONS STILL

PERSIST. CONDITIONS WILL GRADUALLY IMPROVE THROUGH THE DAY AS THE

PRESSURE GRADIENT DECREASES.

&&

.HYDROLOGY...

ISSUED AT 250 AM EDT WED JUL 15 2015

HEAVY RAIN COULD MOVE IN FOR THU NIGHT AND FRIDAY. PWATS CLIMB TO

NEAR 2 INCHES AGAIN AND A LOW LEVEL JET ARRIVES THAT COULD HELP

FOCUS A ROUND OF STORMS WITH LOCALLY HEAVY RAIN. RECENT RAIN HAS

ALSO MOISTENED THE SOIL UP SO RUNOFF COULD BE EFFICIENT. WILL NEED

TO MONITOR TRENDS CLOSELY.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...

MI...BEACH HAZARDS STATEMENT UNTIL 10 AM EDT THIS MORNING FOR MIZ071.

LM...SMALL CRAFT ADVISORY UNTIL 10 AM EDT THIS MORNING FOR LMZ844.

&&

$$

SYNOPSIS...MJS

SHORT TERM...MJS

LONG TERM...LAURENS

AVIATION...MJS

HYDROLOGY...MJS

MARINE...MJS

Delivered by Weather Underground Inc. Wed Jul 15 2015 7:31AM EDT