Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 182039
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
439 PM EDT SAT APR 18 2015

.SYNOPSIS...
ISSUED AT 435 PM EDT SAT APR 18 2015

ISOLATED SHOWERS AND THUNDERSTORMS ARE POSSIBLE THIS
AFTERNOON...MAINLY ALONG AND NORTH OF US-24. OTHERWISE...MORE STEADY
RAIN WILL MOVE IN LATE TONIGHT AND CONTINUE INTO SUNDAY. ISOLATED
THUNDERSTORMS ARE ALSO POSSIBLE SUNDAY. LOWS TONIGHT WILL RANGE FROM
44 TO 55. HIGHS SUNDAY WILL BE IN THE 60S.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 435 PM EDT SAT APR 18 2015

MOISTURE HAS POOLED ALONG THE SOUTHERN THIRD OF THE FORECAST AREA
AND SURFACE TROF / FRONTAL BOUNDARY HAS PUSHED OUT OF
MICHIGAN...EVIDENT ON RADAR. INSTABILITY AND CONVERGENCE ALONG AND
SOUTH OF THIS BOUNDARY HAS TRIGGERED ISOLATED THUNDERSTORMS SOUTH OF
US-30. EXPECT TO SEE ADDITIONAL DEVELOPMENT AS THE EASTERLY FLOW AND
CONVERGENCE INCREASE OVER THE NEXT FEW HOURS.

CONVECTION WILL END AS THE INSOLATION DECREASES AND SHOULD HAVE A
QUICK DECREASE IN COVERAGE.

HIGH PRESSURE GRADUALLY RETREATING THROUGH SUNDAY MORNING.
APPROACHING SYSTEM WITH ABUNDANT CIRRUS SHIELD WILL CONTINUE TO
OVERSPREAD THE REGION AND WITH DEEPENING EASTERLY FLOW...BOUNDARY
LAYER MOISTURE WILL BE SHIFTED SOUTH AND WEST OVERNIGHT...AND EXPECT
THIS TO BE SLOW TO RETURN TO THE NORTHERN TWO-THIRDS OF THE AREA
UNTIL SUNDAY MORNING.

MUCH COOLER DAY SUNDAY AS THE CLOUDS AND PRECIPITATION OVERSPREAD
THE REGION.

&&

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 435 PM EDT SAT APR 18 2015

A SECOND SYSTEM IMMEDIATELY FOLLOWING THE EJECTING SOUTHWESTERN
SHORTWAVE WILL MOVE ACROSS THE AREA EARLY MONDAY. FOLLOWED A GFS
SOLUTION WHICH HAS TRENDED THIS SYSTEM SLOWER. THIS TREND APPEARS
REASONABLE WITH A DEEP DIGGING UPPER TROF AND A 90 KNOT UPPER JET ON
THE BACK SIDE OF THIS SYSTEM. THEREFORE...HAVE ADJUSTED THE TIMING
OF RAIN CHANCES SUNDAY NIGHT AND MONDAY. ISENTROPIC 300K SURFACE
SUPPORTS THE BEST RAIN CHANCES MONDAY MORNING. A LITTLE BREAK IN THE
SHOWERS IS POSSIBLE AFTER MIDNIGHT SUNDAY NIGHT.

AFTER THIS SYSTEM...MUCH COOLER AIR WILL MOVE INTO THE AREA FOR THE
REST OF THE WEEK AS A COLD CORE UPPER LOW BECOMES QUASI STATIONARY
NEAR OR JUST NORTH OF LAKE SUPERIOR. TEMPERATURES WILL BE BELOW
NORMAL FROM TUESDAY THROUGH THE END OF THE WEEK AS MUCH COLDER AND
DRIER AIR SPREADS INTO THE AREA. CONTINUED TO CUT SUPERBLEND RAIN
CHANCES. ALTHOUGH VERY CHILLY AIR ALOFT WITH ALLOW IMPRESSIVE LAPSE
RATES OF 9 TO 10C/KM FROM THE SURFACE TO 750 MB...VERY DRY AIR IN
THE LOW LEVELS WITH DEW POINTS IN THE MID 20S TO LOWER 30S WILL
PROBABLY BE TOO DRY TO SUPPORT MUCH MORE THAN ISOLATED SHOWERS.
EXPECT HIGHS DURING THIS PERIOD IN THE LOW TO MID 50S WITH LOWS IN
THE LOW TO MID 30S. KEPT THE MENTION OF FROST OUT FOR NOW GIVEN
UNCERTAINTY OF THE TIMING AND LOCATION OF LINGERING CLOUDS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 435 PM EDT SAT APR 18 2015

HIGH PRESSURE AND EASTERLY FLOW WAS AFFECTING THE NORTHERN TWO
THIRDS OF THE FORECAST AREA. SURFACE TROF AND MOISTURE CONVERGENCE
HAS TRIGGERED SHOWERS AND EXPECT TO SEE THE GREATEST THREAT FOR
THE SHOWERS OVER THE FWA TAF THROUGH 21-22Z. CONVECTION ENDS
QUICKLY AFTER 22Z. CLOUDS AND SHOWERS SPREAD NORTH DURING THE DAY
SUNDAY AND THIS WILL SPREAD NORTH WITH MVFR AND IFR CONDITIONS TO
OVERSPREAD QUICKLY DURING THE LATTER PART OF THE TAF PERIOD.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

SYNOPSIS...MCD
SHORT TERM...LEWIS
LONG TERM...SKIPPER
AVIATION...LEWIS


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