Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 201632
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1232 PM EDT MON APR 20 2015

.SYNOPSIS...
ISSUED AT 348 AM EDT MON APR 20 2015

SCATTERED SHOWERS ARE EXPECTED TODAY AS AN UPPER LEVEL DISTURBANCE
ROTATES THROUGH THE REGION IN THE WAKE OF STRONG SURFACE LOW
PRESSURE LIFTING NORTH. DAYTIME TEMPERATURES WILL REMAIN IN THE MID
TO UPPER 50S. SHOWERS WILL EXIT OVERNIGHT WITH LOWS AROUND 40
DEGREES. COOL WEATHER WILL PERSIST THROUGH MUCH OF THE UPCOMING WEEK.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 348 AM EDT MON APR 20 2015

988MB SURFACE LOW NOW LIFTING INTO SOUTHERN LOWER MICHIGAN ALONG
WITH BEST ISENTROPIC ASCENT AND CVA FORCING. PSEUDO "DRY SLOT"
AHEAD OF SECONDARY VORT MAX STILL UPSTREAM IS NOW IN PLACE ACROSS
MOST OF OUR CWA. THIS NEXT WAVE...ONE OF A SERIES OF VORTICITY
SPOKES ROTATING AROUND LARGE CLOSED LOW TO OUR NORTHWEST...WILL
BRING THE POTENTIAL FOR ANOTHER ROUND OF LIGHT RAIN THIS MORNING.
HOWEVER...PRECIP CHANCES HAVE BEEN COMPLICATED BY PROGRESSIVE MCS
ACROSS THE TENNESSEE VALLEY THAT HAS EFFECTIVELY "ROBBED"
NORTHWARD MOISTURE TRANSPORT. REGIONAL RADAR MOSAIC SHOWS LITTLE
MORE THAN SCT SHOWERS UPSTREAM OF OUR AREA AND LATEST 00Z
MODELS...BOTH HI-RES AND SPECTRAL...HAVE BACKED OFF LOCAL QPF
AMOUNTS. STILL EXPECT SOME LIGHT SHOWERS AS THIS SHORTWAVE AND
ASSOCIATED FRONTAL BOUNDARY PASS BUT NOWHERE NEAR THE COVERAGE AND
INTENSITY OF THE FIRST ROUND. HAVE CUT BACK BOTH POPS AND QPF FOR
THIS MORNING. CHANCES OF RAIN WILL THEN CONTINUE INTO THE
AFTERNOON BEHIND SURFACE FRONT. CAA WILL LEAD TO VERY STEEP LOW
LEVEL LAPSE RATES DURING THE AFTERNOON. THIS COUPLED WITH
SUFFICIENT RESIDUAL BOUNDARY LAYER MOISTURE AND PASSAGE OF A THIRD
WEAK VORT MAX SHOULD ALLOW SCT-NUM SHOWERS AND EVEN A FEW
THUNDERSTORMS THROUGH THE EARLY EVENING HOURS. NO SEVERE WEATHER
EXPECTED BUT SOME SMALL HAIL MAY BE POSSIBLE IN OUR EASTERN
COUNTIES WHERE SLIGHTLY BETTER INSTABILITY EXISTS AND FREEZING
LEVELS ARE VERY LOW. ANY LINGERING SHOWERS SHOULD END AROUND
MIDNIGHT AS BOUNDARY LAYER COOLS/STABILIZES AND DRIER AIR
GRADUALLY ADVECTS INTO THE AREA.

MAIN STORY TODAY MAY ACTUALLY BE THE GUSTY WINDS. TIGHT GRADIENT
EXPECTED BEHIND DEEPENING SURFACE CYCLONE ALONG WITH A DECENT
ISALLOBARIC COMPONENT THIS MORNING. WHAT IS PERHAPS MORE
DISCONCERTING IS MODEL FORECAST SOUNDINGS THAT SHOW MIXING HEIGHTS
CLIMBING TO ROUGHLY 800MB WITH WINDS AT THAT LEVEL AROUND 40 KTS.
STRONG PUSH OF ISENTROPIC DESCENT IN CAA REGIME SHOULD HAVE LITTLE
DIFFICULTY IN EFFICIENTLY MIXING DOWN THIS HIGHER MOMENTUM AIR. WIND
FIELDS NOT SUPPORTIVE OF ADVISORY CRITERIA (45 MPH) BUT SOME GUSTS
IN THE 30-40 MPH RANGE ARE POSSIBLE. THIS IS ESPECIALLY TRUE IF ANY
CONVECTION MANAGES TO DEVELOP. DAYTIME TEMPS WILL NOT BE MUCH
DIFFERENT THAN CURRENT VALUES AS CAA OFFSETS ANY DIURNAL HEATING.
LOWS TONIGHT WILL DROP TO AROUND 40F AS THERMAL TROUGH MOVES OVER
THE REGION.

&&

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 348 AM EDT MON APR 20 2015

THIS PD WILL BE DOMINATED BY DEEP CUTOFF LOW OVR THE NRN LAKES TO
START WHICH THEN SLOWLY SHIFTS EWD INTO NEW ENGLAND BY FRI AND INTO
THE NW ATL BY NXT WEEKEND. HWVR UPSTREAM ELONGATED MID LVL TROUGH
PERSISTS WWD INTO THE NRN PLAINS AND WILL KEEP COOL NWRLY FLW ALOFT
IN PLACE THROUGH THE PD W/MUCH BLO NORMAL TEMPS AS A RESULT.

OUTSIDE A PSBL SPRINKLE NORTH HALF TUE AFTN...REMAINDER OF THE PD
XPCD TO BE DRY UNDER THE INFLUENCE OF ANTICYCLONIC SINK ZONE ALG
SWRN PERIPHERY OF MID LVL TROUGH AXIS. CLD CVR EXTENT DYS4-6 THOUGH
STILL UNCERTAIN BUT W/LL THERMAL TROUGH MAXIMIZING IN THE THU-FRI
TIME FRAME AND IN REFLECTION OF SFC RIDGE POSITION XPC FROSTY TO
FREEZING TEMPS LIKELY ACRS AT LEAST THE NORTH HALF AND WILL CONT
PRIOR HWO MENTION.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1232 PM EDT MON APR 20 2015

GRADUAL IMPROVEMENT IN CIGS TO HIGH MVFR/LOW VFR CAN BE EXPECTED
THIS AFTERNOON/EVENING AS POST FRONTAL DRYING/DEEPER MIXING
OVERSPREADS. WESTERLY WINDS WILL BE ON THE STRONG SIDE BOTH THIS
AFTERNOON AND AGAIN TOMORROW UNDER CLOSED LOW IN VICINITY OF THE
NORTHERN GREAT LAKES. THERE MAY BE JUST ENOUGH RESIDUAL BOUNDARY
LAYER MOISTURE AND STEEPENING LOW LEVEL LAPSE RATES TO TOUCH OFF A
FEW SHOWERS THIS AFTERNOON/EVENING...ALTHOUGH COVERAGE/PROBABILITY
REMAIN TOO LOW FOR SHRA INCLUSION ATTM.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 6 PM EDT TUESDAY FOR LMZ043-046.

&&

$$

SYNOPSIS...AGD
SHORT TERM...AGD
LONG TERM...T
AVIATION...STEINWEDEL


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