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000
FXUS63 KGRR 171524
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1124 AM EDT FRI MAY 17 2013

LATEST UPDATE...
UPDATE/MARINE

.SYNOPSIS...
ISSUED AT 334 AM EDT FRI MAY 17 2013

MORE CLOUDS WILL MOVE INTO THE AREA TODAY AS A SYSTEM TO OUR WEST
TRIES TO MOVE IN. DRY LOW LEVELS WILL KEEP RAIN CHANCES NEAR ZERO
FOR THE AREA. SOME LOW CHANCES OF RAIN WILL BE POSSIBLE TONIGHT AND
EARLY SATURDAY AS A FRONTAL SYSTEM MOVES BY JUST NORTHWEST OF THE
AREA. CONDITIONS SHOULD CLEAR OUT A BIT FOR LATER SATURDAY AND
SUNDAY WITH WARM TEMPERATURES EXPECTED. BETTER CHANCES FOR RAINFALL
WILL COME TOWARD MONDAY AND LINGER THROUGH WEDNESDAY NEXT WEEK.

&&

.UPDATE...
ISSUED AT 1121 AM EDT FRI MAY 17 2013

PRECIPITATION MOVING OFF THE WI SHORELINE HAS BEEN SLOW TO
DIMINISH. GFS 06Z RUN SEEMED TO HAVE A BETTER HANDLE ON THE
PRECIPITATION THAN THE NEW NAM. HRRR 12Z RUN AND OLD GFS PAINT
PRECIPITATION ACROSS MUCH OF NRN ZONES...NORTH OF MKG TO GRR WITH
PRECIPITAITON THIS AFTERNOON. WILL BUMP UP POPS AND LOWER
TEMPERATURES FOR THIS REGION.

UPDATE ISSUED AT 949 AM EDT FRI MAY 17 2013

ADDED A FEW RAIN SHOWERS TO THE FORECAST FOR LUDINGTON TO NEAR
CADILLAC. RADAR TRENDS SHOW INCREASING RETURNS AND THE OBSERVATION
OUT OF CADILLAC INDICATED THAT THE PRECIPITATION WAS REACHING THE
GROUND. AM MONITORING THE WEAKENING THUNDERSTORMS OVER IN ERN
WISCONSIN. MAY NEED TO ADD SOME PRECIPITATION TO THE MUSKEGON
FORECAST AS WELL IF THEY DO NOT WEAKEN QUICKLY ENOUGH. I DID
ADJUST TEMPERATURES DOWNWARD SLIGHTLY FOR NORTHERN ZONES DUE TO
THE CLOUDS AND PRECIPITATION.

&&

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 334 AM EDT FRI MAY 17 2013

THE MAIN CHALLENGE IN THE SHORT TERM IS DETERMINING PCPN CHCS
THROUGH THE PERIOD. MOST OF THE PERIOD THROUGH THE WEEKEND LOOKS
DRY...HOWEVER THERE ARE A COUPLE OF PERIODS WHERE RAIN POTENTIAL HAS
TO BE ADDRESSED.

WE EXPECT THAT THE AREA WILL STAY DRY DURING THE DAY TODAY. HIGH
CLOUDS STREAMING IN FROM THE WEST ARE SHROUDING THE AREA PRETTY WELL
THIS MORNING. SOME MID CLOUD COVER IS SHOWING UP OVER WEST CENTRAL
AREAS OF THE CWFA. THERE IS SOME MOISTURE TRANSPORT/THETA E
ADVECTION TAKING PLACE IN THE MID LEVELS. THE BEST PUSH OF EACH IS
OCCURRING FURTHER WEST IN WI. IN ADDITION...THE EASTERLY FLOW IS
CONTINUING TO FEED DRIER AIR IN ACROSS THE AREA. THESE FACTORS
SHOULD KEEP THE ENTIRE AREA DRY TODAY. TEMPS WILL LIKELY BE A COUPLE
OF DEGREES COOLER TODAY WITH LESS SOLAR INSOLATION.

THE FIRST CHC OF RAIN THAT COULD OCCUR WOULD BE DURING THE PERIOD
FROM TONIGHT INTO SAT MORNING ACROSS THE N/NW COUNTIES. WE HAVE
ADDED A SLIGHT CHC OF SHOWERS TO THE N/NW COUNTIES. THE BEST MID
LEVEL THETA E ADVECTION/MOISTURE TRANSPORT CONTINUES TO BE W/NW OF
THE AREA. THERE ARE SOME SOLUTIONS SHOWING THERE COULD BE JUST
ENOUGH FORCING AND DEEP ENOUGH MOISTURE TO GENERATE ENOUGH PCPN TO
REACH THE GROUND THROUGH THE DRIER LOWER LEVELS.

BY SAT AFTERNOON...WE SEE SUFFICIENT DIGGING OF THE WRN TROUGH AND
RESULTANT BUILDING OF THE UPPER RIDGE OVER THE AREA TO PUSH THE
CLOUDS AND PCPN WELL NORTH OF THE CWFA. MORE SUNSHINE COMPARED TO
THIS AFTERNOON WILL HELP TO WORK ON THE WARMING H850 TEMPS TO AROUND
12-13C AND SUPPORT HIGHS AROUND 80. THE LOW LEVEL FLOW WILL BE
VEERING A BIT TO THE S/SE AS THE HUDSON BAY RIDGE SHIFTS EAST. THIS
WILL HELP TO START ADVECTING SOMEWHAT HIGHER DEW POINTS INTO THE
AREA. FCST SOUNDINGS SHOW THAT THE LOW LEVELS WILL STILL BE JUST A
LITTLE TOO DRY YET TO ALLOW FOR ANY POP UP DIURNAL CONVECTION ALONG
ANY BOUNDARIES.

WE WILL SEE MORE SUNSHINE ON SUN WITH TEMPS INCREASING A CATEGORY AS
TEMPS ALOFT UNDER THE RIDGE INCREASE A COUPLE OF DEGREES C. SUN
MIGHT SEE A SLIGHTLY BETTER CHC FOR A POP UP SHOWER DURING THE
AFTERNOON HOURS AS BETTER LOW LEVEL MOISTURE DOES ADVECT IN. FCST
SOUNDINGS INDICATE THAT THE MID AND UPPER LEVELS MAY BE JUST A TAD
TOO WARM YET WITH THE UPPER RIDGE OVERHEAD TO ALLOW SHOWERS TO FORM.
THE CHC IS NOT ZERO...HOWEVER IT LOOKS JUST A LITTLE TOO LOW AT THIS
TIME TO JUSTIFY ADDING IN THE CHC.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 334 AM EDT FRI MAY 17 2013

LONG TERM PATTERN BEGINS WITH THE UPPER RIDGE OVERHEAD AND AN UPPER
LOW ACROSS THE NORTHERN PLAINS. THE RIDGE GRADUALLY SHIFTS SOUTH AND
EAST ALLOWING THE GREAT LAKES TO BECOME MORE UNDER THE INFLUENCE OF
THE UPPER LOW NEXT WEEK. THE UPPER LOW FILLS WITH TIME AND BECOMES
ABSORBED INTO A EASTERN CANADIAN UPPER TROUGH. BOTH THE GFS AND
ECMWF PAINT THIS SCENARIO.

AT THE SURFACE LOW PRESSURE WILL GRADUALLY MOVE INTO THE GREAT LAKES
STATES FROM THE WEST INTO MID WEEK. ISOLATED SHOWERS AND STORMS
APPEAR POSSIBLE SUNDAY NIGHT...WITH CHANCES RAMPING UP TO LIKELY
FROM TUESDAY INTO WEDNESDAY AS THE LOW AND A SURFACE WARM FRONT WILL
BE IN THE AREA. THE THUNDER THREAT DIMINISHES INTO WEDNESDAY NIGHT
AND THURSDAY AND HAVE SHOWERS ONLY IN THE FORECAST DURING THESE
PERIODS.

THE LONG TERM PERIOD LOOKS TO BE WET OVERALL...WITH RAINFALL IN
EXCESS OF AN INCH POSSIBLE AS THE UPPER LOW SLOWLY MOVES THROUGH THE
REGION. TEMPERATURES WILL START OUT WARM IN SOUTHERLY
FLOW...TRENDING BACK TOWARD NORMAL INTO MID WEEK.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 749 AM EDT FRI MAY 17 2013

VFR CONDITIONS ARE EXPECTED THE NEXT 24 HOURS...AS MID AND HIGH
CLOUDS DOMINATE THE DAYTIME HOURS. BASES SHOULD BE AT OR ABOVE
9000FT. CEILINGS MAY LOWER SOME TONIGHT...BUT 5000-6000FT BASES WILL
KEEP CONDITIONS AT VFR. WINDS WILL BE STEADY FROM THE EAST AT 8-12
KNOTS TODAY AND TONIGHT.


&&

.MARINE...
ISSUED AT 1121 AM EDT FRI MAY 17 2013

EXPANDED THE MENTION OF RAIN IN THE FORECAST FOR NORTHERN MARINE
ZONES.

&&

.FIRE WEATHER...
ISSUED AT 334 AM EDT FRI MAY 17 2013

CONDITIONS LOOK TO BE A SLIGHT BIT BETTER THAN THU WITH REGARD TO
FIRE DANGER...ALTHOUGH THE FIRE DANGER WILL REMAIN ELEVATED. MORE
CLOUD COVER WILL LIMIT THE AMOUNT OF HEATING AND THE MIXING DOWN OF
DRIER AIR. CONDITIONS WILL ONCE AGAIN APPROACH RED FLAG CRITERIA...
HOWEVER WE EXPECT RH/S TO REMAIN JUST SHY OF THE RED FLAG
CRITERIA....WINDS TO REMAIN JUST UNDER CRITERIA WITH A FEW GUSTS TO
NEAR CRITERIA...AND TEMPS RIGHT AROUND THE THRESHOLD OF 75 DEGREES.
WE WILL NEED TO MONITOR THE SITUATION THIS AFTERNOON.

DEW POINTS SHOULD COME UP SOME OVER THE WEEKEND AS THE FLOW BECOMES
A LITTLE MORE SOUTHERLY AND MOISTURE WILL ADVECT INTO THE AREA. THIS
SHOULD KEEP RED FLAG CRITERIA FROM BEING REACHED.

&&

.HYDROLOGY...
ISSUED AT 334 AM EDT FRI MAY 17 2013

WE WILL NOT SEE ANY HYDROLOGY ISSUES THROUGH THE WEEKEND WITH LIKELY
NO RAIN AT ALL. THE CHANCES OF ANY HYDROLOGY ISSUES MON-WED NEXT
WEEK WITH RAINFALL WITH THE SYSTEM DO NOT LOOK THAT GREAT EITHER.
THE SURFACE OF THE SOIL AROUND THE AREA HAS DRIED CONSIDERABLY...AND
RIVER/STREAM LEVELS HAVE RETURNED TO NEAR AVERAGE FLOWS. THE MODELS
ARE SHOWING RAINFALL AMOUNTS OF OVER AN INCH POSSIBLE FROM MON-WED.
THIS SHOULD NOT ALL COME AT ONCE...AND THE GROUND SHOULD SOAK IT UP
PRETTY WELL. RIVER LEVELS WILL COME UP...HOWEVER WE DO NOT EXPECT
ANY NOTABLE ISSUES AT THIS TIME.

&&

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

$$

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