Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 122152
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
552 PM EDT SAT JUL 12 2014

.SYNOPSIS...
ISSUED AT 544 PM EDT SAT JUL 12 2014

LOW PRESSURE AND A COLD FRONT WILL BE MOVING THROUGH THE REGION
TONIGHT. THIS WILL BRING WITH IT A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS. LOW TEMPERATURES TONIGHT WILL BE IN THE LOWER 70S.
THE FRONT WILL STILL BE IN THE AREA TOMORROW CONTINUING THE SHOWER
AND THUNDERSTORM CHANCES. HIGHS TOMORROW WILL BE IN THE LOWER 80S.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 235 PM EDT SAT JUL 12 2014

AN AREA OF SHOWERS WITH ISOLATED THUNDER OVER INDIANA AND NORTHEAST
ILLINOIS HAS BEEN GRADUALLY WEAKENING EARLY THIS AFTERNOON IN THE
VICINITY OF A WEAK UPPER LEVEL TROF. THESE SHOWERS HAVE ALSO BEEN
SUPPORTED BY WEAK LOW LEVEL THETA E CONVERGENCE. EXPECT THIS AREA TO
CONTINUE TO WEAKEN AS LOW LEVEL FORCING BECOMES ESTABLISHED WEST OF
THE AREA EARLY TONIGHT. THETA E MOISTURE FLUX WILL THEN INCREASE
LATER TONIGHT ASSOCIATED WITH A WEAK UPPER LOW AND AHEAD OF A WEAK
FRONT. NOT EXCITED ABOUT SEVERE CHANCES GIVEN MARGINAL PARAMETERS
AND THE LARGE AREA OF RAIN COOLED AIR AT THE SURFACE. HOWEVER...
NAM/BUFKIT SUPPORTS A STRONG SIGNAL FOR HEAVY RAIN GIVEN
PRECIPITABLE WATER VALUES OVER 2.3 INCHES AT TIMES EXCEEDING THE
99TH PERCENTILE PER 64 YEAR UPPER AIR CLIMATOLOGY. THERE WILL ALSO
BE A SUFFICIENT WARM CLOUD DEPTH AND FAVORABLE NET STORM MOTION. AS
A RESULT...HAVE RAISED RAIN CHANCES AND HAVE ALSO MENTIONED HEAVY
RAIN IN THE FORECAST/GRIDS. HAVE ALSO UPDATED THE HAZARDOUS WEATHER
OUTLOOK IN THIS REGARD. THE BEST CHANCES FOR THUNDER WILL BE OVER
SOUTHEAST AREAS SUNDAY. THERE IS ALSO A CHANCE FOR SEVERE STORMS
SUNDAY AFTERNOON OVER THESE SOUTHEAST AREA AS THE ATMOSPHERE
DESTABILIZES AND AS UPPER LEVEL IMPULSES TRACK ACROSS THE AREA.

&&

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 235 PM EDT SAT JUL 12 2014

FOCUS WILL BE ON EFFECTS OF STRONG COLD FRONT WHICH WILL SWEEP
ACROSS THE REGION ON MONDAY.

PIECE OF DEEP CANADIAN UPPER LOW WILL BREAK OFF AND QUICKLY DIVE
SOUTH INTO THE UPPER MIDWEST AND GREAT LAKES REACHING WISCONSIN BY
MONDAY EVENING. THE UPPER LOW WILL QUICKLY DEEPEN IN RESPONSE TO
110+ KT JET STREAK ROUNDING THE BASE OF THE TROUGH. THIS WILL HELP
FORCE A STRONG AND GENERALLY FAST MOVING COLD FRONT ACROSS THE
REGION DURING THE DAY MONDAY. WHILE THE BETTER THETA E AIR WILL HAVE
BEEN SHUNTED SE WITH THE SUNDAY FRONT...DEWPOINTS ALONG AND AHEAD OF
THE FRONT WILL STILL BE IN THE LOWER 60S (PWATS TO 1.5 INCHES). THIS
COMBINED WITH THE STRONG FORCING AND SOMEWHAT STEEP LAPSE RATES
SHOULD ALLOW FOR AT LEAST SCT SHOWERS AROUND THE FRONT. AS THE FRONT
APPROACHES SE AREAS...SOMEWHAT BETTER INSTABILITY MAY EXIST AND
GIVEN AMOUNT OF SHEAR WITH THIS SYSTEM THREAT FOR ISOLATED STRONG TO
SEVERE STORMS STILL LOOMS. IN TERMS OF POPS...BIT CONCERNED ABOUT
DRY FORECAST MONDAY MORNING GIVEN AMOUNT OF MSTR STILL AROUND BUT
FOR NOW WILL KEEP CHC POPS CONFINED TO AFTERNOON/EVE HOURS DURING
BEST TIME FRAME.

A COLD MID WEEK BY JULY STANDARDS STILL LOOKS ON TRACK WITH COLDEST
TEMPERATURES IN THE TUESDAY TO WEDS NGT TIME FRAME AS UPPER LOW
LINGERS ACROSS THE GREAT LAKES. GFS HAS BEEN THROWN OUT WITH A MUST
FASTER TREND OF PUSHING OUT THE UPPER LOW...WHICH IS A TYPICAL BIAS
IN THESE SITUATIONS. HIGHS TUESDAY MAY NOT REACH 70 IN MANY
LOCATIONS WITH LAKE SHORE AREAS POSSIBLY ONLY IN THE LOWER 60S (OR
EVEN NEAR 60). OVERNIGHT LOWS ARE FORECAST FOR THE LOW 50S AT THIS
POINT...BUT HONESTLY WOULDN`T BE SURPRISED TO SEE SOME 40S
ESPECIALLY NORTH. WITH THE COLD AIR ALOFT...CAN`T RULE OUT A FEW
SHOWERS AROUND THE AREA BUT WITH MAJORITY OF THE MSTR WELL SOUTH AND
EAST NOT WORTHY OF PLACING IN FORECAST (WHICH BLEND OF MODELS
GUIDANCE TRIES TO DO).

FINALLY THE COLD AIR MASS WILL DEPART AND ALLOW SLOWLY MODERATING
TEMPS INTO THE UPCOMING WEEKEND AS SFC HIGH PRESSURE SETTLES IN THE
EAST AND KEEPS DEEPER MSTR AND MOST SYSTEMS SOUTH OF THE AREA.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 110 PM EDT SAT JUL 12 2014

AN AREA OF SHOWERS WITH ISOLATED THUNDER OVER INDIANA AND NORTHEAST
ILLINOIS HAS BEEN GRADUALLY WEAKENING EARLY THIS AFTERNOON IN THE
VICINITY OF A WEAK UPPER LEVEL TROF. THESE SHOWERS HAVE ALSO BEEN
SUPPORTED BY WEAK LOW LEVEL THETA E CONVERGENCE. HAVE ADDED A
BRIEF TEMPO GROUP AT THE START OF THE TAF PERIOD TO COVER THIS
LIGHT PRECIPITATION. THETA E MOISTURE FLUX WILL INCREASE TONIGHT
ASSOCIATED WITH A WEAK UPPER LOW AND AHEAD OF A WEAK FRONT. HAVE
INTRODUCED THUNDER TONIGHT IN THE TAFS GIVEN FAIRLY HIGH
CONFIDENCE IN THE TIMING OF THE STORMS.


&&

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

$$

SYNOPSIS...LOTHAMER
SHORT TERM...SKIPPER
LONG TERM...FISHER
AVIATION...SKIPPER


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