Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 311739
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
139 PM EDT THU JUL 31 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 329 AM EDT THU JUL 31 2014

A SLOW WARM TREND WILL CONTINUE RIGHT INTO THE WEEKEND ACROSS THE
AREA WITH A SLIGHT INCREASE IN HUMIDITY LEVELS. LOW RAIN CHANCES
WILL PERSIST INTO THE WEEKEND AS WEAK WAVES OF LOW PRESSURE WILL
AFFECT THE AREA. MOST AREAS WILL NOT SEE MUCH RAIN WITH
SHOWERS/STORMS EXPECTED TO BE RATHER ISOLATED TO SCATTERED. THE BEST
CHANCES WILL BE FURTHER INLAND AWAY FROM LAKE MICHIGAN DURING THE
AFTERNOON AND EARLY EVENING HOURS.

&&

.UPDATE...
ISSUED AT 1035 AM EDT THU JUL 31 2014
LOWERED PRECIPITATION CHANCES AND REMOVED THUNDER FROM AFTERNOON
FORECAST. DRY MID LEVELS AND LOW LEVEL WESTERLY FLOW WILL PROVIDE
DRY WEATHER AND MAINLY CLEAR SKIES THIS AFTERNOON WEST OF U.S.
ROUTE 127... MODEST SHALLOW CAPE OF LESS THAN 500 J/KG MAY RESULT
IN SOME WIDELY SCATTERED SHOWERS EAST OF U.S. 127.

STILL THINKING FRI WILL BE A MORE ACTIVE DAY WITH AMPLIFICATION OF UPPER
TROF PROVIDING STEEPER LAPSE RATES WITH AFTERNOON CAPE VALUES AROUND
1500 J/KG. LAKE BREEZE FRONT WILL BE LIKELY FOCUS FOR STORMS. A
FEW LOCALIZED STRONG STORMS ARE LIKELY WITH HAIL/MICROBURST
POTENTIAL. MAIN CONVECTIVE MODE WILL BE SHORT-LIVED MULTICELL
CLUSTERS AS DEEP LAYER SHEAR WILL BE LESS THAN 20 KTS.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 329 AM EDT THU JUL 31 2014

THE MAIN FOCUS OF THE FCST CONTINUES TO BE CONVECTIVE TRENDS THROUGH
THE PERIOD...AND DETERMINING IF THERE IS A SEVERE WX THREAT OR NOT.

CONDITIONS FOR TODAY DO NOT SUPPORT A SIGNIFICANT CONCENTRATION OF
STORMS OR A SEVERE WX THREAT. WE HAVE ONE OF THE MAIN LOBES OF THE
LONG WAVE TROUGH THAT IS IN THE PROCESS OF EXITING THE AREA TO THE
EAST THIS MORNING. A SHOWER IS POSSIBLE UP NORTH THIS MORNING BEFORE
IT EXITS...BUT NOTHING OF SIGNIFICANCE. COOL AIR ALOFT REMAINS OVER
THE AREA. WITH TEMPS INLAND INCHING UP TO 80 OR SO AND DEW POINTS IN
THE MID 50S...A FEW SHOWERS/STORMS WILL DEVELOP THIS AFTERNOON AND
LAST INTO EARLY THIS EVENING. AN INVERSION RESULTING FROM THE
SUBSIDENCE IN THE WAKE OF THE LOBE MAY KEEP THINGS LIMITED UNTIL
LATER AFTERNOON WHEN A SHORT WAVE APPROACHES. THAT SAID...CAPE IS
VERY THIN...WINDS IN THE MID LEVELS ARE LIGHT SO WE EXPECT SOME
SMALL HAIL AND SOME SUB-SEVERE WIND GUSTS AT WORST TODAY.

THE THREAT FOR PCPN WILL REMAIN OVER THE AREA THROUGH THE DAY ON
SAT. SHORT WAVE ENERGY COMING INTO NORTH DAKOTA THIS MORNING WILL
CARVE OUT ANOTHER TROUGH OVER THE REGION BY FRI. THIS TROUGH
OVERHEAD AND WHAT LOOKS LIKE AN ELEVATED MIXED LAYER OF INSTABILITY
MOVES OVERHEAD TONIGHT. THERE IS NO MAJOR FEATURE COMING IN...BUT
ANY MESOSCALE FOCUS COULD POP A SHOWER/STORM OVERNIGHT TONIGHT.

PROBABLY THE BEST CHC OF PCPN IN THE PERIOD AND THE POTENTIALLY
STRONGEST STORMS OF THE SHORT TERM WILL COME ON FRI. THE NEW TROUGH
WILL MOVE OVERHEAD...COOLING THE MID LEVELS DOWN A BIT. AT THE SAME
TIME TEMPS WILL INCH INTO THE LOWER 80S AND DEW POINTS WILL INCREASE
TO ALMOST 60. THESE CONDITIONS WILL PRODUCE CAPES OVER 1000 J/KG
WITH A GOOD CHUNK OF THAT CAPE IN THE -10 TO -30C LAYER. THIS WOULD
SUPPORT SOME BIGGER HAIL.

THE CHC OF RAIN WILL PERSIST INTO FRI NIGHT AND SAT...BUT THE CHC
WILL DIMINISH SLIGHTLY. THE TROUGH OVER THE AREA ON FRI WILL SLOWLY
SHIFT EAST BY SAT AFTERNOON. SOME RIDGING BUILDS AND AND TEMPS ALOFT
WARM A LITTLE. THIS WILL LIMIT THE INSTABILITY SOME...AND RESULT IN
A LOWER SEVERE THREAT FOR SAT AFTER A SLIGHT CHC OF A POP UP SHOWER
OR STORM FRI NIGHT WITH THE TROUGH STILL OVERHEAD AT THAT TIME..

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 329 AM EDT THU JUL 31 2014

UPPER TROUGH IS FINALLY LIFTING OUT OF THE AREA TO THE EAST AND
NORTHEAST AT THE BEGINNING OF THE LONG TERM PERIOD (SATURDAY NIGHT).
FOR THE REMAINDER OF THE LONG TERM PERIOD UPPER RIDGING NUDGES
TOWARD THE GREAT LAKES FROM THE PLAINS STATES WITH A GENERAL
WEST-NORTHWEST FLOW IN PLACE. THIS WILL MEAN AN END TO THE DIURNAL
TYPE SHOWERS AND STORMS THAT WE HAVE BEEN EXPERIENCING AND A
TRANSITION INTO A MORE PROGRESSIVE PATTERN.

FEATURES TO KEY ON WILL BE A FRONTAL BOUNDARY THAT SAGS SOUTH INTO
THE AREA ON MONDAY...WHICH LINGERS ACROSS THE AREA INTO TUESDAY.
HAVE SIDED WITH THE SLOWER EVOLUTION WITH THIS FRONT VIA THE ECMWF.
BOTH THE GFS AND ECMWF THEN DEVELOP A SURFACE LOW ON THE FRONT AND
BRING THIS THROUGH THE REGION MID WEEK. THE ECMWF IS QUICKER WITH
THE LOW INTO THE AREA WHICH SEEMS PLAUSIBLE GIVEN THE MORE
PROGRESSIVE FLOW THAT WILL BE IN PLACE.

BOTTOM LINE IN TERMS OF SENSIBLE WEATHER...DRY SATURDAY NIGHT AND
SUNDAY AS SURFACE HIGH PRESSURE DRIFTS THROUGH THE AREA. CHANCES FOR
SHOWERS AND STORMS EACH FORECAST PERIOD SUNDAY NIGHT THROUGH
WEDNESDAY AS THE FRONT PIVOTS INTO THE AREA AND THEN
STALLS...FOLLOWED BY A LOW MOVING FROM WEST TO EAST ALONG THE
BOUNDARY. BEST CHANCES FOR PRECIPITATION WILL LIKELY BE MID NEXT
WEEK AS THE LOW MOVES THROUGH.

TEMPERATURES WILL BE NEAR NORMALS FOR THIS TIME OF YEAR THROUGH THE
PERIOD.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 137 PM EDT THU JUL 31 2014

VFR WX EXPECTED THIS AFTERNOON. ERN TAF SITES WILL SEE MORE CLOUD
COVERAGE THIS AFTERNOON. A SHOWER OR BRIEF TSRA IS ALSO POSSIBLE
AND COVERED WITH A VCSH. FOG MAY BE AN ISSUE AT KMKG FRIDAY
MORNING DUE TO PROXIMITY NEAR THE LAKE WHERE COLDER LAKE TEMPS
WILL CAUSE SFC TEMPS AT KMKG TO COME CLOSER TO DEWPOINT.

&&

.MARINE...
ISSUED AT 1035 AM EDT THU JUL 31 2014
FOG ADVISORY WILL EXPIRE AT 11 AM THIS MORNING...MOST WEBCAMS NOW
INDICATING VISIBILITIES ARE AT OR ABOVE 1 MILE IN RELATIVELY
SHALLOW FOG. BELIEVE IMPROVEMENT WILL CONTINUE AS LAKE BREEZE
STREGTHENS THIS AFTERNOON. MAY NEED TO ISSUE NEW ADVISORY FOR
LATER TONIGHT AS COLD NEAR COASTAL WATERS BELOW 50F CONTINUE TO
INTERACT WITH THE SEASONABLY MOIST AIRMASS WITH DEWPOINTS NEAR
60F.


&&

.HYDROLOGY...
ISSUED AT 300 PM EDT WED JUL 30 2014

NO MAJOR HYDROLOGY ISSUES EXPECTED. THE PRECIPITATION IS FORECASTED
TO BE SCATTERED.  AS A RESULT NOT MUCH BASIN AVERAGE RAINFALL
PREDICTED. WILL NEED TO MONITOR THE POSSIBLE WAVE FOR THU NIGHT
INTO FRI. TRENDS COULD SUPPORT A STEADIER RAIN EVENT.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...DENSE FOG ADVISORY UNTIL 9 PM EDT THIS EVENING FOR LMZ846>848.

&&

$$

UPDATE...COBB
SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...DUKE
AVIATION...93
HYDROLOGY...MJS
MARINE...COBB






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