Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 211859
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
300 PM EDT MON APR 21 2014

.UPDATE...
LONG TERM SECTION HAS BEEN UPDATED BELOW.

&&

.SYNOPSIS...
ISSUED AT 304 AM EDT MON APR 21 2014

SHOWERS WITH EMBEDDED THUNDERSTORMS WILL DEVELOP LATER TODAY AND
CONTINUE TONIGHT AS A COLD FRONT MOVES THROUGH THE OHIO VALLEY.
COOLER DRIER WEATHER RETURNS FOR TUESDAY AND WEDNESDAY AS HIGH
PRESSURE MOVES THROUGH THE REGION. WARMER AND MORE UNSETTLED WEATHER
RETURNS FOR LATE WEEK WITH THE PASSAGE OF ANOTHER COLD FRONT. BEHIND
THE FRONT...COOLER WEATHER WILL RETURN FOR THE WEEKEND.

&&

.NEAR TERM /TODAY/...
ISSUED AT 945 AM EDT MON APR 21 2014

RADAR MOSAIC SHOWS SOME ECHOES OF 20-30 DBZ MOVING INTO KNOX COUNTY
AT 930 AM AND VISIBLE SATELLITE SHOWS A CONVECTIVE NATURE TO THE
CLOUDS ASSOCIATED WITH THESE ECHOES. THUS FAR NO PRECIPITATION HAS
BEEN REPORTED AT THE GROUND UNDER THESE CLOUDS AND WITH DEW POINTS
IN THE MID 40S TO LOW 50S AND A FAIRLY DRY COLUMN THINK CONTINUING
WITH NO MEASURABLE PRECIP TIL AFTER 19Z IS A GOOD IDEA. HOWEVER
CAN/T RULE OUT A FEW SPRINKLES DEVELOPING IN THE SOUTHWEST...SO WILL
GO AHEAD AND ADD A CHANCE FOR SPRINKLES THERE FOR THE NEXT FEW
HOURS. REST OF THE FORECAST IS IN GOOD SHAPE WITH HIGHS IN THE MID
TO UPPER 70S STILL ON TRACK AND HI RES MODELS SHOWING SIMILAR TIMING
TO MEASURABLE PRECIP AS THE GOING FORECAST...AFTER 19Z WITH BEST
CHANCES NOT ARRIVING UNTIL SOMETIME AFTER 0Z.

PREVIOUS DISCUSSION FOLLOWS...

MAIN FOCUS FOR TODAY IS THE APPROACH OF THE UPPER WAVE AND COLD
FRONT TO THE WEST AS LOW PRESSURE OFF THE NORTH CAROLINA COAST
FINALLY SHIFTS FURTHER EAST INTO THE ATLANTIC OCEAN. THIS WILL
ENABLE THE RIDGE AXIS TO LIKEWISE SHIFT EAST TO THE U S EAST COAST
BY LATE DAY. CLOUD COVERAGE WILL INCREASE THROUGHOUT THE DAY AS
MOISTURE ADVECTS INTO THE REGION FROM THE SOUTHWEST. WEAK LIFT AND
FORCING WILL MOVE INTO THE OHIO VALLEY DURING THE COURSE OF THE
AFTERNOON WITH SCATTERED SHOWERS AND PERHAPS A THUNDERSTORM
SPREADING EAST INTO THE FORECAST AREA BY LATE AFTERNOON. MORE
EXPANSIVE COVERAGE TO RAINFALL WILL LIKELY HOLD OFF UNTIL THIS
EVENING AS MODEL SOUNDINGS INDICATING IT WILL TAKE MUCH OF THE DAY
TO MOISTEN THE BOUNDARY LAYER. WILL CARRY MAINLY LOW CHANCE POPS FOR
MID/LATE AFTERNOON.

TEMPS...FILTERED SUN THROUGH THE MORNING AND WARM ADVECTION AHEAD OF
THE FRONT WILL ENABLE ANOTHER WARM DAY PEAKING IN THE 70S. LOW LEVEL
THERMALS SUPPORTED MAX TEMPS AT OR JUST ABOVE MAVMOS IN THE
MID/UPPER 70S.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
ISSUED AT 304 AM EDT MON APR 21 2014

FORECAST CHALLENGES FOCUS ON PRECIP CHANCES TONIGHT AS THE FRONT
SWINGS THROUGH THE REGION...AND POTENTIAL FOR FROSTY TEMPS WEDNESDAY
MORNING.

WEAKENING UPPER WAVE WILL TRACK THROUGH THE OHIO VALLEY WITH THE
COLD FRONT TONIGHT WITH RAIN SHOWERS AND EMBEDDED THUNDERSTORMS.
MOST WIDESPREAD COVERAGE EXPECTED DURING THE EVENING AND EARLY
OVERNIGHT...WITH PRECIP GRADUALLY SHIFTING INTO THE SOUTHERN/EASTERN
PORTIONS OF THE FORECAST AREA AFTER 06Z TUESDAY. BRIEF PERIOD OF
ISENTROPIC LIFT AND SUBTLE LOW LEVEL CONVERGENCE WITHIN A NARROW
RIBBON OF DEEPER MOISTURE WILL BE THE MAIN RAINFALL CATALYSTS
TONIGHT AND WILL MAINTAIN LIKELY POPS. RAINFALL AMOUNTS WILL BE
GENERALLY LIGHT AT A QUARTER INCH OR LESS.

COLD FRONT WILL BE EAST OF THE FORECAST AREA BY DAYBREAK TUESDAY
WITH THE DEEPER MOISTURE DEPARTING ALONG WITH IT. EXPECT SKIES TO
CLEAR QUICKLY TUESDAY MORNING AS MODEL SOUNDINGS AND RH PROGS
INDICATING A RAPIDLY DRYING COLUMN. DESPITE STRONG COLD ADVECTION
AND A  SHARP WAVE ALOFT PASSING THROUGH THE LOWER GREAT LAKES DURING
THE COURSE OF THE DAY...EXPECT ANY CU FORMATION TO BE SIGNIFICANTLY
LIMITED BY THE INCREASING SUBSIDENCE AND DRY AIR ADVECTING INTO THE
REGION. EFFICIENT LOW LEVEL MIXING WILL BRING STRONGER WINDS TO THE
SURFACE TUESDAY AFTERNOON WITH MAX GUSTS UP TO 25 MPH.

HIGH PRESSURE RIDGE CENTERS ACROSS THE REGION TUESDAY NIGHT WITH
NORTHERLY WINDS BECOMING LIGHT AFTER MIDNIGHT. WITH CLEAR
SKIES...GOOD RADIATIONAL COOLING SETUP FOR THE REGION WITH POTENTIAL
FOR FROST ACCRUAL OVER MUCH OF THE FORECAST AREA AS TEMPS FALL INTO
THE 30S. WITH THE GROWING SEASON HAVING ADVANCED ENOUGH ACROSS THE
SOUTHERN HALF OF THE FORECAST AREA...POTENTIAL FOR FROST HEADLINES
EARLY WEDNESDAY. WILL CONTINUE TO HIGHLIGHT IN THE HWO AT THIS TIME.
REMAINDER OF THE SHORT TERM WILL BE DRY WITH WARM ADVECTION
COMMENCING BY LATE WEDNESDAY AS RIDGING ALOFT EXPANDS EAST INTO THE
OHIO VALLEY. A WARM FRONT WILL LIFT ACROSS THE FORECAST AREA
WEDNESDAY NIGHT AND MAY BRING A BRIEF INCREASE IN CLOUDS. ANY PRECIP
ASSOCIATED WITH THE WARM FRONT HOWEVER SHOULD REMAIN TO THE
NORTHWEST OF THE REGION.

TEMPS...MAVMOS GUIDANCE SUPPORTED LOW LEVEL THERMALS FOR HIGHS BOTH
TUESDAY AND WEDNESDAY...WITH TEMPS SLIPPING BACK INTO THE 60S BOTH
DAYS OVER MUCH OF THE FORECAST AREA. AS MENTIONED ABOVE...TUESDAY
NIGHT LOOKING FROSTY AS TEMPS EXPECTED TO FALL INTO THE 30S. WENT
NEAR MOS GUIDANCE FOR LOWS ALL THREE NIGHTS.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
ISSUED AT 300 PM EDT MON APR 21 2014

THE LONG TERM PERIOD WILL START OUT WET AND END WET. HOWEVER THERE
ARE A LOT OF DIFFERENCES BETWEEN MODELS ON HOW QUICKLY THE RAIN
RETURNS LATE IN THE LONG TERM.

A COLD FRONT WILL MOVE RAPIDLY EAST ACROSS OUR REGION THURSDAY NIGHT
PRODUCING NUMEROUS SHOWERS AND A FEW THUNDERSTORMS THURSDAY
EVENING.  THESE WILL GRADUALLY END OVER NIGHT AS THE COLD FRONT
MOVES RAPIDLY EAST.

FRIDAY THROUGH SATURDAY WILL BE MOSTLY DRY.  WILL MENTION A SLIGHT
CHANCE OF SHOWERS IN OUR FAR NORTH SATURDAY AS SEVERAL MODELS
INDICATE NEAR TRACE QPF AMOUNTS THERE AND IT IS ALSO CLOSER TO THE
SURFACE LOW OVER THE GREAT LAKES.

MODELS MOVE STRONG HIGH PRESSURE INTO SOUTHERN CANADA NORTH OF THE
GREAT LAKES.  THEY ALSO DEVELOP A WARM FRONT OVER THE LOWER
MISSISSIPPI VALLEY AS LOW PRESSURE MOVES INTO THE CENTRAL PLAINS
SUNDAY.  THE EURO IS AGGRESSIVE IN SPREADING RAIN INTO OUR REGION AS
EARLY AS SATURDAY NIGHT...WHILE THE GFS ALL BUT FAR SOUTHWEST
SECTIONS DRY THROUGH THE PERIOD.  THE GEMNH MODEL IS NOT AS SLOW AS
THE GFS...BUT SOMEWHAT IN BETWEEN MODELS.  WILL LEAN IN THAT
DIRECTION AS THIS SEEMS A GOOD COMPROMISE.

MADE A FEW TWEAKS IN TEMPERATURES...BUT OVERALL ALL BLEND
TEMPERATURES SEEEM OK MOST PERIODS.

&&

.AVIATION /DISCUSSION FOR THE 21/18Z TAF ISSUANCE/...
ISSUED AT 100 PM EDT MON APR 21 2014

MOSTLY VFR. HOWEVER A PERIOD OF MVFR CEILINGS POSSIBLE AFTER
MIDNIGHT TONIGHT TO NEAR SUNRISE TUESDAY. MODERATE TO BRISK WINDS
WILL OCCUR TUESDAY.

LOW PRESSURE OVER NORTHERN LAKE MICHIGAN AND A TRAILING COLD FRONT
ACROSS EASTERN IOWA WILL MOVE SOUTHEAST ACROSS OUR REGION DURING THE
MIDDLE AND LATER PARTS OF TONIGHT.  VFR CONDITIONS WILL CONTINUE
THIS AFTERNOON. HOWEVER SCATTERED SHOWERS AND AN ISOLATED
THUNDERSHOWER WILL INCREASE ACROSS OUR REGION LATE THIS AFTERNOON
AND EARLY TONIGHT. WILL GO WITH PREVAILING SHOWERS AND VCTS
BEGINNING AT MOST SITES AROUND 00Z-02Z TIME PERIOD. MODELS INDICATE
MVFR CEILINGS MAY OCCUR ALONG AND JUST BEHIND FRONT AS SHOWERS
INCREASE ALONG THE COLD FRONT OVERNIGHT.

FOLLOWING THE COLD FRONT MUCH DRIER AIR SPREAD IN FROM THE NORTHWEST
CAUSING RAPID CLEARING BY MID OR LATE MORNING. WINDS THIS AFTERNOON
WILL BE SOUTHWEST 10 TO 12 KNOTS DECREASING A LITTLE THIS EVENING
AND THEN BECOMING NORTHWEST AND INCREASING UP TO 15 KNOTS AND GUSTS
TO 25 KNOTS TUESDAY MORNING.

&&

.IND WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SYNOPSIS...RYAN
NEAR TERM...RYAN/CP
SHORT TERM...RYAN
LONG TERM...JH
AVIATION...JH

VISIT US AT HTTP://WWW.WEATHER.GOV/IND

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WWW.TWITTER.COM/NWSINDIANAPOLIS
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