Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 182230
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
630 PM EDT MON AUG 18 2014

.UPDATE...
THE AVIATION SECTION HAS BEEN UPDATED BELOW.

&&

.SYNOPSIS...
ISSUED AT 217 PM EDT MON AUG 18 2014

A FRONTAL SYSTEM IS EXPECTED TO MOVE INTO THE AREA TUESDAY NIGHT
AND EVENTUALLY STALL OUT LATER THIS WEEK. THIS WILL SERVE TO KEEP
THE WEATHER UNSETTLED OVERALL THROUGH MOST OF THE UPCOMING WEEK.

&&

.NEAR TERM /REST OF THIS AFTERNOON AND TONIGHT/...
ISSUED AT 217 PM EDT MON AUG 18 2014

A FEW SMALL SHOWERS ARE BEGINNING TO DEVELOP NEAR THE SOUTHEAST
PARTS OF THE FORECAST AREA. THREAT FOR ISOLATED TO WIDELY SCATTERED
CONVECTION SHOULD CONTINUE THROUGH SUNSET DUE TO AN UNSTABLE AIR
MASS AND LITTLE CAP.

OTHERWISE...CONVECTION EXPECTED TO DEVELOP OFF TO THE NORTHWEST
LATER THIS AFTERNOON AND TONIGHT IN WARM ADVECTION ZONE AHEAD OF
NEXT UPPER TROUGH DROPPING INTO THE NORTHERN MIDWEST. ORIENTATION OF
LOW LEVEL JET TONIGHT SUGGESTS MOST OF THIS ACTIVITY WILL STAY OFF
TO THE NORTHWEST...HOWEVER CAN/T RULE OUT SOMETHING SNEAKING
INTO THE NORTHWEST ZONES DURING THE PRE DAWN HOURS TUESDAY. WILL GO
WITH SOME SMALL POPS LATE TONIGHT IN THOSE AREAS...AND DRY ELSEWHERE.

A LIGHT GRADIENT AND HUMID AIR MASS SUGGESTS AREAS OF FOG WILL FORM
AGAIN LATE TONIGHT.

LOW LEVEL THICKNESSES SUGGEST THE GFS MOS LOWS TONIGHT LOOK
REASONABLE.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
ISSUED AT 217 PM EDT MON AUG 18 2014

NORTHWEST UPPER FLOW EXPECTED ACROSS THE AREA DURING THIS
PERIOD...AS AN UPPER TROUGH MOVES THROUGH THE GREAT LAKES TUESDAY
AND WEDNESDAY AND A HEAT RIDGE BUILDS INTO THE LOWER MISSISSIPPI
VALLEY AND GULF COAST STATES.

MODEL DATA SUGGEST UPPER TROUGH AND ASSOCIATED FRONTAL SYSTEM WILL
MOVE INTO THE AREA TUESDAY NIGHT. APPEARS THE BEST LIFT/HIGHEST
PRECIPITATION THREAT WILL BE MOVING THROUGH FROM THE MID AFTERNOON
HOURS UNTIL ABOUT MIDNIGHT TUESDAY NIGHT...ALTHOUGH SOME OF THE
ENSEMBLE MEMBERS BRING IN THE THREAT QUICKER. SYSTEM LOOKS STRONG
ENOUGH THAT MOST PLACES WILL SEE PRECIPITATION EITHER DURING THE DAY
TUESDAY OR TUESDAY NIGHT. QUESTIONS REVOLVING AROUND TIMING WILL
PRECLUDE LIKELY POPS. STEEPENING LAPSE RATES AND INCREASING DEEP
LAYER SHEAR SUGGEST POTENTIAL STORM ORGANIZATION.

FRONTAL ZONE LOOKS TO LINGER OVER THE AREA THROUGH THE REST OF THE
PERIOD. WARM ADVECTION BEGINS WEDNESDAY AFTERNOON AND CONTINUES
THROUGH THURSDAY...SO ADDITIONAL CHANCES FOR CONVECTION WILL BE
PRESENT AS EARLY AS WEDNESDAY AFTERNOON...BUT MORE LIKELY WEDNESDAY
NIGHT INTO THURSDAY WHEN WARM ADVECTION WILL BE STRONGER. WILL
CONTINUE WITH CHANCE POPS FOR WEDNESDAY AND THURSDAY TO COVER THIS
POTENTIAL. LAPSE RATES/DEEP LAYER SHEAR CONTINUE TO SUGGEST
ORGANIZED CONVECTION POSSIBLE WEDNESDAY AND THURSDAY WITH HEAVY
RAINFALL ALSO A THREAT WITH PRECIPITABLE WATERS APPROACHING 2 INCHES
BY THURSDAY.

PROGGED LOW LEVEL THICKNESSES SUGGEST THE GFS MOS TEMPERATURE
GUIDANCE THROUGH THURSDAY LOOKS OK FOR THE MOST PART.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...

ISSUED AT 155 PM EDT MON AUG 18 2014

ECMWF AND GFS DEPICT A WARM WEEKEND IN PLACE DURING THE PERIOD.
MODELS AGREE THAT A STRONG UPPER RIDGE WILL BE BUILDING ACROSS THE
MISSISSIPPI RIVER VALLEY AND OHIO VALLEY DURING THIS TIME
PERIOD...ALLOWING HEAT AND HUMIDITY TO BUILD FROM THE SOUTHWEST.
THIS SHOULD RESULT IN SOME OF THE WARMEST AIR OF THE SUMMER ACROSS
CENTRAL INDIANA. THROUGH SUNDAY THE BLOCKING RIDGE CONTINUES TO
PUSH APPROACHING SHORT WAVES FROM THE WEST WELL NORTH OF INDIANA.
MEANWHILE MODELS DO CONTINUE TO DEPICT VERY HIGH DEW POINTS IN THE
LOWER 70S. ECMWF ALSO SHOWS 700MB TEMPS THROUGH THE THE PERIOD AT
OR BELOW 10C...WHICH LEADS TO A QUESTIONABLE CAPPING SITUATION.
THUS WILL NEED TO INCLUDE CHANCES SEVERAL DAYS DURING THIS PERIOD
AS DIURNAL THUNDERSTORMS STILL APPEAR POSSIBLE.

HEAT LOOKS TO LESSEN ON MONDAY AS THE UPPER RIDGE ACROSS THE AREA
BEGINS TO FLATTEN. GFS AND ECMWF SHOW THE WARM ARE THEN BEING
PUSHED FARTHER SOUTH.

&&

.AVIATION /DISCUSSION FOR THE 190000Z TAF ISSUANCE/...

ISSUED AT 630 PM EDT MON AUG 18 2014

CONDITIONS WILL DETERIORATE TO IFR OR WORSE AT MOST SITES TONIGHT
BEFORE RETURNING TO VFR BY TUESDAY AFTERNOON.

A MOIST AIRMASS COMBINED WITH LIGHT WINDS AND CLEAR TO PARTLY CLOUDY
SKIES SHOULD SET THE STAGE FOR FOG AND STRATUS ONCE AGAIN TONIGHT.
CONTINUED WITH IFR OR WORSE FORECAST DEVELOPING MAINLY AFTER 06Z.
KEPT KIND AT MVFR DUE TO URBAN HEAT ISLAND EFFECTS.

FOG AND STRATUS WILL BURN OFF BY 15Z OR SO TUESDAY. THUNDERSTORMS
ARE POSSIBLE TUESDAY AFTERNOON...BUT CONFIDENCE IS LOW ENOUGH IN
TIMING AND COVERAGE TO LEAVE MENTION OF THEM OUT OF THE TAFS THAT
FAR OUT.

&&

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

$$

SYNOPSIS...JAS
NEAR TERM...JAS
SHORT TERM...JAS
LONG TERM....PUMA
AVIATION...50

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