000
FXUS63 KGRR 141140
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
740 AM EDT TUE MAY 14 2013

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 346 AM EDT TUE MAY 14 2013

A WARM FRONTAL SYSTEM WILL APPROACH THE AREA DURING THE DAY TODAY. A
WAVE OF LOW PRESSURE MOVING THROUGH THIS MORNING WILL BRING A CHANCE
OF SOME LIGHT SHOWERS. AFTER A MAINLY DRY PERIOD THIS AFTERNOON AND
EARLY EVENING...ANOTHER WAVE WILL MOVE THROUGH AND INCREASE THE
CHANCE OF SHOWERS AND STORMS TONIGHT. AREAS NORTH OF I-96 WILL SEE
THE BEST CHANCES OF RAIN. THE CHANCE OF STORMS WILL GRADUALLY END
FROM NORTHWEST TO SOUTHEAST ON WEDNESDAY MORNING AS A COLD FRONT
SINKS SOUTH THROUGH THE AREA. MILD AND DRY AIR IS EXPECTED THEN FOR
THURSDAY AND FRIDAY.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 346 AM EDT TUE MAY 14 2013

THE MAIN FOCUS OF THE SHORT TERM PORTION OF THE FCST IS PCPN/THUNDER
CHANCES THROUGH WED.

THERE ARE A COUPLE OF CHANCES OF SHOWERS RIGHT OFF THE BAT HERE
EARLY THIS MORNING. THE FIRST CHANCE IS THE BAND OF SPRINKLES/VIRGA
THAT IS CURRENTLY MOVING THROUGH THE CWFA. THIS IS ASSOCIATED WITH A
PUSH OF THETA E IN THE MID LEVELS OF THE ATMOSPHERE AROUND 700 MB OR
SO. THE VERY DRY AIR BELOW THIS IS ONLY ALLOWING SOME SPRINKLES/
SPOTTY LIGHT SHOWERS TO OCCUR. THIS WILL BE MOVING OUT IN THE NEXT
COUPLE OF HOURS.

THE NEXT CHC OF PCPN WILL COME AROUND 12Z OR SO. THIS IS WHEN WE
WILL SEE THE BEST MOISTURE TRANSPORT AROUND 925-850 MB NOSE INTO THE
AREA VIA A 30-35 KNOT LLJ. WE WILL SEE DEW POINTS OF AROUND 10C
GRADUALLY WORK INTO THE AREA. MODELS ARE NOT REALLY INDICATING A
WHOLE LOT OF INSTABILITY THIS MORNING WITH ELEVATED LI/S STAYING
POSITIVE. THE LLJ WILL BEGIN TO WEAKEN A BIT AS EXPECTED AS WE PASS
THE PEAK TIME OF THE LLJ...AND THE BEST INFLUX OF MOISTURE WILL
SHIFT EAST OF THE CWFA BY 18Z THIS AFTERNOON.

WE SHOULD SEE A LULL THEN IN THE PCPN THIS AFTERNOON AND EARLY THIS
EVENING. WE WILL HAVE THE WARM FRONT JUST SOUTH/SOUTHWEST OF THE
AREA THROUGH THE AFTERNOON. THE ISSUE THOUGH IS THAT THERE IS VERY
LITTLE PUSH OF THE FRONT IN THE VICINITY OF THE AREA WITH ONE LLJ
HEADING EAST...AND THEN WE WILL BE WAITING FOR THE NEXT LLJ TO
APPROACH LATER TONIGHT.

THE 40-45 KNOT LLJ IS EXPECTED TO CRANK UP BY 00Z ACROSS WRN WI BY
00Z TONIGHT...AND THEN MIGRATE OVER THE STATE AROUND OR JUST AFTER
06Z. THERE IS A DECENT AMOUNT OF MOISTURE TRANSPORT GOING
ON...HOWEVER THE MODELS ARE SHOWING LIMITED PCPN. THIS IS LIKELY DUE
TO LIMITED RICH MOISTURE COMING IN DUE TO A LACK OF A DIRECT FEED
FROM THE GULF. THE BEST CHC OF SHOWERS AND STORMS WILL BE NORTH OF
I-96 TONIGHT WHERE THE NOSE OF THE LLJ WILL BE AIMED. THE ENTIRE
AREA WILL SEE A THREAT FROM WAA SCATTERED CONVECTION.

ANY CONVECTION THAT DOES GET GOING TONIGHT WILL HAVE THE POTENTIAL
TO GENERATE SOME DECENT HAIL. FCST SOUNDINGS INDICATE SOME DECENT
CAPE ABOVE THE -20C ISOTHERM. THE ELEVATED NATURE OF THE INSTABILITY
SHOULD LIMIT WIND POTENTIAL.

A CHANCE OF STORMS WILL REMAIN POSSIBLE DURING THE MORNING HOURS ON
WED. THIS CHC WILL DIMINISH PRETTY QUICKLY AS THE COLD FRONT SLIPS
SOUTH OF THE AREA WED AFTERNOON. WE WILL SEE DEW POINTS DROPPING
SOME EVEN WITH TEMPS REMAINING IN THE 70S FOR MOST LOCATIONS. WED
NIGHT AND THU SHOULD SEE DRY CONDITIONS AS DRIER AIR FILTERS IN. THE
FRONT WILL LOCK UP ANY MOISTURE SOUTH OF THE AREA. THE AIR BEHIND
THE FRONT WILL NOT BE MUCH COLDER.

.LONG TERM...(THURSDAY NIGHT THROUGH MONDAY)
ISSUED AT 346 AM EDT TUE MAY 14 2013

FRONTAL SYSTEM IN THE SHORT TERM WILL SINK SOUTH OF THE AREA AND BE
LOCATED ACROSS PORTIONS OF ILLINOIS...INDIANA AND OHIO AT THE START
OF THE LONG TERM. QUIET WEATHER IS EXPECTED THURSDAY NIGHT AND
FRIDAY WITH THE BOUNDARY LOCATED TO OUR SOUTH. FRIDAY NIGHT THE
FRONT BEGINS TO LIFT NORTH AS A WARM FRONT AND HAVE CHANCE POPS IN
THE FORECAST AS GOOD WARM AIR ADVECTION...ESPECIALLY ALOFT...IS
FORECAST.

SATURDAY THROUGH MONDAY LOOKS LIKE IT MAY BE AN ACTIVE PERIOD AS THE
FRONT LIFTS NORTH AND WARM...MOIST AIR SHOULD SPREAD INTO THE GREAT
LAKES. UPPER TROUGHING IN THE WEST WILL SHIFT EAST THROUGH THE
NORTHERN PLAINS THROUGH THE COURSE OF THE WEEKEND. THE TROUGH TRIES
TO PUSH INTO THE GREAT LAKES EARLY NEXT WEEK. SO...WHILE POPS ARE IN
THE FORECAST SAT-MON...FEEL THE BEST CHANCES WILL COME LATE IN THE
WEEKEND INTO EARLY NEXT WEEK AS THE UPPER TROUGH SLOWLY NUDGES IN.
UPPER RIDGING IS ACTUALLY FORECAST MOST OF THE WEEKEND...SO NOT
EXPECTING A WASH OUT. THE GFS LOOKS AS THOUGH IT MAY HAVE SOME
CONVECTIVE FEEDBACK SAT AFTERNOON INTO SUNDAY MORNING ACROSS THE
SOUTH. HAVE SIDED MORE WITH THE ECMWF AS THAT AMOUNT OF PRECIP
DOESN/T MAKE A WHOLE LOT OF SENSE RIGHT UNDER THE UPPER RIDGE.

OVERALL...THE EXTENDED PERIOD WILL FEATURE WARMER THAN NORMAL
TEMPERATURES AND GRADUALLY INCREASING CHANCES FOR PRECIPITATION FROM
THE WEEKEND INTO EARLY NEXT WEEK.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 739 AM EDT TUE MAY 14 2013

MID DECK OF CLOUDS OVER THE AREA THIS MORNING WILL SHIFT EAST BY
MIDDAY. VFR CONDITIONS ARE EXPECTED THROUGH THE THE DAY. WINDS
WILL BE THE MAIN STORY...ESPECIALLY THIS MORNING INTO THE EARLY
AFTERNOON. GUSTY SOUTH WINDS WILL DEVELOP IN THE NEXT FEW
HOURS...BEFORE SUBSIDING A BIT IN THE MID TO LATE AFTERNOON. GUSTS
OF 20-30 KNOTS WILL BE POSSIBLE.

TONIGHT...A BAND OF SHOWERS AND STORMS MAY MOVE THROUGH THE TAF
SITES...WITH THE I-96 TAF SITES STANDING THE BEST CHANCE.
CONFIDENCE IS NOT HIGH AT THIS POINT...SO RAN WITH VCTS IN THE
TAFS. 03Z-12Z IS THE MAIN TIME FRAME FOR STORMS IN THE AREA. CLOUD
BASES SHOULD BE VFR...WITH SOME BRIEF MVFR VSBYS AS THE STORMS
MOVE THROUGH.

&&

.MARINE...
ISSUED AT 346 AM EDT TUE MAY 14 2013

WE WILL NOT BE ISSUING A SMALL CRAFT ADVISORY WITH THE FCST PACKAGE.
WE HOWEVER WILL BE WATCHING THE POTENTIAL THROUGH THE MORNING FOR AN
ADVISORY. WE WILL SEE A STRONG PUSH OF VERY WARM AIR A COUPLE OF
THOUSAND FEET ABOVE THE SURFACE THROUGH THIS MORNING. THIS WARM AIR
OVER THE COOL WATERS OF LAKE MICHIGAN WILL GREATLY LIMIT THE DEGREE
OF WINDS AND THE WAVES. IT IS STILL POSSIBLE WE COULD SEE SOME OF
THE WIND MAKE IT TO THE SURFACE.

WE WILL SEE ANOTHER BREEZY PERIOD POSSIBLE ON WED ALONG AND BEHIND
THE COLD FRONT PUSHING THROUGH.


&&

.FIRE WEATHER...
ISSUED AT 346 AM EDT TUE MAY 14 2013

WE WILL SEE SOME ELEVATED FIRE DANGER THIS WEEK. TEMPS INTO THE 70S
FOR TODAY AND TOMORROW WILL COMBINE WITH SOME BRISK WINDS TO PRODUCE
THE ELEVATED NATURE OF THE FIRE DANGER. DEW POINTS SHOULD COME UP
SOME INTO THE 50S...SO THIS SHOULD KEEP THE POTENTIAL OF SPREADING
WILDFIRES SOMEWHAT LIMITED. WE ARE STILL IN THE PRE-GREEN UP STAGES
OF THE CONIFEROUS TREES UP NORTH SO THE DANGER WILL REMAIN. WED WILL
BE SIMILAR...ALTHOUGH DEW POINTS WILL BE DROPPING SOME IN THE
AFTERNOON DUE TO THE COLD FRONTAL PASSAGE SO THAT COULD EXACERBATE
CONDITIONS SOME.

&&

.HYDROLOGY...
ISSUED AT 346 AM EDT TUE MAY 14 2013

WE ARE NOT EXPECTING HYDROLOGY ISSUES THROUGH THE END OF THIS WEEK.
RAINFALL THROUGH WED AFTERNOON WHEN THE FRONT WILL END THE PCPN CHCS
SHOULD GENERALLY REMAIN BELOW HALF AN INCH. THE HIGHEST AMOUNTS OF
RAIN WILL OCCUR UP NORTH. MOST AREAS WILL ONLY SEE AMOUNTS UNDER A
COUPLE OF TENTHS OF AN INCH THROUGH WED MORNING.

&&

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

$$

SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...DUKE
AVIATION...DUKE
FIRE WEATHER...NJJ
HYDROLOGY...NJJ
MARINE...NJJ