Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 251537
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1137 AM EDT SAT JUL 25 2015

LATEST UPDATE...
HYDRO

.SYNOPSIS...
ISSUED AT 330 AM EDT SAT JUL 25 2015

IT WILL FEEL LIKE THE DOG DAYS OF SUMMER AS WE HEAD THROUGH THE REST
OF THE WEEKEND AND INTO THE MIDDLE PART OF THE WORK WEEK. HIGHS WILL
LIKELY TOP OUT IN THE MIDDLE 80S TODAY WITH UPPER 80S IN MANY AREAS
FOR SUNDAY AND MONDAY. TUESDAY LOOKS TO BE THE WARMEST DAY OF THE
NEXT WEEK AS WE WILL LIKELY PUSH TO OR EXCEED 90 DEGREES. A
WEAKENING COLD FRONT IS EXPECTED TO SLIDE THROUGH SOUTHWEST LOWER
MICHIGAN TODAY AND BRING WITH IT SCATTERED SHOWER AND THUNDERSTORM
DEVELOPMENT. WIDESPREAD PRECIPITATION IS NOT EXPECTED...IN FACT MANY
AREAS WILL REMAIN DRY. FAIR AND DRY WEATHER IS ON TAP FOR SUNDAY
INTO EARLY NEXT WEEK AS HIGH PRESSURE WILL BE SITUATED OVER THE
AREA.

&&

.UPDATE...
ISSUED AT 1101 AM EDT SAT JUL 25 2015

TRIMMED POPS CONSIDERABLY THIS AFTERNOON FOR THE WESTERN TWO
THIRDS OF THE FORECAST AREA. THIS IS BASED LARGELY ON THE LAST
SEVERAL RUNS OF THE HRRR. SURFACE OBSERVATIONS SHOW A CONSIDERABLE
SHIFT TO WESTERLY FLOW AT THE LAKESHORE...HERALDING THE APPROACH
OF THE STABLE MARINE LAYER OFF LAKE MICHIGAN. THIS AND
CONSIDERABLE CLOUDINESS OVER LOWER MICHIGAN SHOULD LIMIT
DESTABILIZATION OVER MOST OF SOUTHWEST LOWER MICHIGAN. CLOUDINESS
SHOULD GRADUALLY ERODE FROM WEST TO EAST. COLD FRONT CURRENTLY
EXTENDING FROM FAR NORTHERN LAKE MICHIGAN THROUGH MADISON
WISCONSIN WILL PROVIDE A FOCUS FOR DEEPER CONVECTION...MAINLY OVER
SOUTH-CENTRAL AND SOUTHEAST LOWER MICHIGAN. THE OVERALL SEVERE
THREAT REMAINS LIMITED. PLEASE SEE THE SPC DAY1 OUTLOOK FOR
FURTHER DETAILS.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 330 AM EDT SAT JUL 25 2015

CONCERNS IN THE SHORT TERM ARE RELATED TO SHOWER AND STORM CHANCES
TODAY AND THEN TWEAKING HIGH TEMPERATURES THE NEXT COUPLE DAYS AS WE
WILL BE QUITE WARM.

AS FOR CONVECTION TODAY...IT LOOKS LESS AND LESS IMPRESSIVE WITH
EACH MODEL RUN. THE HRRR GUIDANCE IS ONLY SHOWING SCATTERED STORMS
AT BEST. THE LATEST RAP GUIDANCE IS INDICATING MOST UNSTABLE CAPE
VALUES OF 1000-2000 J/KG WHICH IS MORE THAN ENOUGH...BUT OTHER
FACTORS LIMIT THE THREAT. THEY ARE NAMELY...THE MAIN SHORTWAVE IS
WELL NORTH OF THE AREA AND A WIND OFF THE LAKE WILL LIKELY TEMPER
INSTABILITY DURING THE AFTERNOON. MID LEVEL LAPSE RATES ARE NOT
STEEP EITHER...ON THE ORDER OF 5.5 C/KM. THE LLJ AND 850MB MOISTURE
TRANSPORT HAVE TRENDED DOWN AS WELL. BOTTOM LINE...LOOKING FOR
SCATTERED STORMS TO DEVELOP MIDDAY AND WORK SOUTH/EAST OUT OF THE
AREA DURING THE AFTERNOON HOURS. ANY CHANCE OF A STRONG STORM WOULD
BE DURING THE AFTERNOON TOWARDS LAN/BTL/JXN.

OTHERWISE FAIR WEATHER IS EXPECTED WITH HIGH PRESSURE BUILDING IN
BEHIND THE WEAKENING COLD FRONT. AFTER TODAY WITH CLOUDS ASSOCIATED
WITH THE FRONT...SKIES SHOULD BE MAINLY CLEAR. THINKING WE WILL PUSH
INTO THE MID 80S TODAY...CLOUD COVER IS A BIT OF A CONCERN WHICH
COULD TREND THINGS EITHER SIDE OF THOSE NUMBERS. UPPER 80S LOOK
PRETTY SOLID FOR SUNDAY AND MONDAY GIVEN 850MB TEMPS IN THE 17-19C
RANGE.

.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 330 AM EDT SAT JUL 25 2015

OUR MAIN FOCUS OF THE LONG TERM IS THE FRONTAL PASSAGE THAT IS
EXPECTED DURING THE MID-WEEK TIME FRAME...AND THE CHCS OF CONVECTION
THAT WILL ACCOMPANY THE FRONT.

THE BEGINNING OF THE PERIOD IS EXPECTED TO BE HOT AND HUMID WITH
LITTLE CHCS OF RAIN INITIALLY. WE WILL HAVE A FAIRLY DECENT UPPER
RIDGE IN PLACE. THIS UPPER RIDGE WITH HIGH HEIGHTS WILL SUPPORT THE
HOT WEATHER AND WILL CAP THE ATMOSPHERE OFF FROM ANY PCPN FROM
OCCURRING. WE ARE LOOKING AT A GOOD CHANCE OF LOWER 90S ON TUE WITH
H850 TEMPS APPROACHING 20C.

THERE IS A LITTLE UNCERTAINTY WITH THE SPECIFIC TIMING OF THE
SHOWERS/STORMS WITH THE FRONT MID-WEEK. THE CONSENSUS OF THE CHC OF
SHOWERS/STORMS LOOKS TO OCCUR TUE NIGHT INTO WED. SOME MODELS ARE A
LITTLE EARLIER...AND SOME ARE A LITTLE LATER. IT DOES NOT LOOK LIKE
A STRONG FEED OF GULF MOISTURE WILL BE PRESENT. ENOUGH SHOULD BE
AROUND WITH THE STRENGTH OF THE FRONT TO BRING A DECENT CHC OF RAIN.

SEVERE CHCS ARE NOT LOOKING REAL STRONG AT THIS POINT. THERE DOES
LOOK TO BE A GOOD DEAL OF INSTABILITY PRESENT...ESPECIALLY DURING
PEAK HEATING ON WED. DEEP LAYER SHEAR IS LACKING A BIT WITH THE
BETTER WIND FIELDS LAGGING THE FRONT/STORMS A BIT. WE WILL CONTINUE
TO MONITOR THIS POTENTIAL AND THE TRENDS OVER THE NEXT FEW DAYS.

WE WILL SEE A COOL DOWN ALONG WITH DRIER CONDITIONS FOR THE THU AND
FRI TIME FRAME. WE WILL SEE A TROUGH OVER THE AREA EVENTUALLY GIVING
WAY TO A SFC RIDGE. NW FLOW ALOFT AND IN THE LOWER LEVELS WILL COOL
US OFF A BIT. IT DOES NOT LOOK TOO COLD AT THIS TIME WITH H850 TEMPS
DROPPING INTO THE LOWER TEENS C.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 753 AM EDT SAT JUL 25 2015

CUMULUS CLOUDS ARE EXPECTED TO FILL IN THIS MORNING...TAKING
CONDITIONS BROKEN AT ALL TAF SITES. CEILINGS FOR THE MOST PART
WILL BE IN THE 3500-5000FT RANGE...BUT FOR A TIME FROM
15Z-18Z...KMKG AND KGRR WILL LIKELY GO MVFR WITH CEILINGS JUST
BELOW OR NEAR 3000FT.

A WEAK COLD FRONT WILL BE SLIDING SOUTH THROUGH THE AREA TODAY AND
SCATTERED SHOWER AND THUNDERSTORM DEVELOPMENT CAN BE EXPECTED. AT
THIS POINT COVERAGE LOOKS TO BE SOMEWHAT SPARSE AND THEREFORE ONLY
HAVE VCSH WORDING IN THE TAFS.

SKIES WILL CLEAR OUT THIS EVENING AND REMAIN THAT WAY OVERNIGHT.
THERE MAY BE SOME LIGHT FOG LATE TONIGHT...BUT DECIDED TO HOLD OFF
ADDING ANOTHER FORECAST GROUP INTO THE 12Z TAFS.


&&

.MARINE...
ISSUED AT 330 AM EDT SAT JUL 25 2015

WAVES OF 1 TO 3 FEET ARE EXPECTED THIS MORNING FROM GRAND HAVEN
NORTHWARD IN A ZONE WHERE SOUTHWEST WINDS OF 10 TO 20 KNOTS WILL
BUILD WAVE HEIGHTS. WINDS LOOK A BIT DOWN FROM WHAT WE WERE SEEING
IN THE MODELS THE LAST COUPLE NIGHTS...SO THE MORE WIDESPREAD 2 TO 4
FOOT WAVES LOOK LESS LIKELY.

AFTER THIS MORNING...QUIET WEATHER OUT ON THE BIG LAKE THE REST OF
THE WEEKEND WITH HIGH PRESSURE IN PLACE. WAVES OF 2 FEET OR LESS AND
WINDS LESS THAN 15 KNOTS SHOULD BE COMMON PLACE.


&&

.HYDROLOGY...
ISSUED AT 1137 AM EDT SAT JUL 25 2015

NO FLOODING CONCERNS EXIST THROUGH THE NEXT SEVERAL DAYS.

RECENT DRY CONDTIONS AND LITTLE EXPECTED RAINFALL HAS RESULTED IN
FALLING RIVER LEVELS. A FEW SCATTERED STORMS ARE EXPECTED TODAY
WITH VERY LOCALIZED HEAVY RAINFALL POSSIBLE. HOWEVER...THIS MAY BE
BRIEF WITH THE LACK OF ANY WIDESPREAD MOISTURE.

ALL RIVERS ARE WELL WITHIN BANKS AND THE STEADY OR FALLING TREND
WILL LIKELY CONTINUE THROUGH THE NEXT FEW DAYS. WARM AND HUMID
CONDITIONS WILL LACK MUCH IN THE WAY OF RAINFALL. A MID WEEK COLD
FRONT WILL HELP TO INCREASE RAIN CHANCES...BUT EVEN THESE TOTALS
SHOULD WILL BE RELATIVELY LIGHT IN REGARDS TO ANY HIGHLIGHTING AND
HYDRO ISSUES.

&&

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

$$

UPDATE...TJT
SYNOPSIS...DUKE
SHORT TERM...DUKE
LONG TERM...NJJ
AVIATION...DUKE
HYDROLOGY...JAM
MARINE...DUKE



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