National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KIWX 172043
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
443 PM EDT FRI MAY 17 2013

.SYNOPSIS...
ISSUED AT 441 PM EDT FRI MAY 17 2013

A FRONTAL BOUNDARY WILL CONTINUE TO SLOWLY SHIFT NORTH
TONIGHT...BRINGING A CHANCE FOR SCATTERED SHOWERS AND THUNDERSTORMS
TO PORTIONS OF NORTHERN INDIANA. THIS FRONT WILL REMAIN IN THE
REGION THROUGH SATURDAY BEFORE SHIFTING NORTH OF THE AREA SUNDAY.
BETTER CHANCES FOR SHOWERS AND THUNDERSTORMS WILL ARRIVE BY
TUESDAY INTO WEDNESDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 318 PM EDT FRI MAY 17 2013

CONVECTION WAS BEGINNING TO FIRE THIS AFTERNOON ACROSS PORTIONS OF
CENTRAL INDIANA...FROM MARION TO LOGANSPORT AND POINTS SOUTHWARD.
THIS INITIAL LINE OF CONVECTION ACROSS OUR SOUTHERN FCST AREA IS
ASSOCIATED WITH AN AREA OF WEAK 925MB TO 850MB FRONTAL LIFT...WITH
THE BOUNDARY ORIENTED FROM NNW TO SE ACROSS THE AREA. COVERAGE
EXPECTED TO REMAIN ISOLATED INITIALLY...WITH MARGINAL LAPSE RATES
AND WEAK FLOW INHIBITING MORE ORGANIZED CONVECTION. DEWPOINTS
QUICKLY DROP FROM THE LOW 60S ACROSS SOUTHERN AREAS TO THE LOWER 40S
ACROSS THE NORTHEAST PORTION OF THE FORECAST AREA...WHICH WILL LIMIT
MUCH NORTHWARD EXTENT OF PRECIPITATION CHANCES THIS AFTERNOON.

MORE ORGANIZED CONVECTION HAS DEVELOPED NEAR INDIANAPOLIS AND POINTS
NORTHWESTWARD...IN AN AREA OF HIGHER DEWPOINTS AND SLIGHTLY MORE
INSTABILITY. PER HRRR/SPC 4KM WRF GUIDANCE...THIS ACTIVITY IS
EXPECTED TO LIFT NORTHWARD INTO THE SOUTHERN AND WESTERN PORTION OF
THE AREA THIS EVENING INTO THE OVERNIGHT. PRECIP ACTIVITY IS
EXPECTED TO QUICKLY WANE WITH THE LOSS OF DAYTIME HEATING...SO
DROPPED POPS SIGNIFICANTLY TOWARD MIDNIGHT AND AFTER. KEPT POPS
UNDER 40 PERCENT THROUGH THE EVENING WITH COVERAGE WORDING...AS
DRIER SURFACE AIRMASS...MARGINAL LAPSE RATES AND WANING INSTABILITY
SHOULD RESULT IN WEAKENING PRECIPITATION AS IT ADVECTS INTO THE
AREA.

NOT MUCH CHANGE TO TEMPERATURES OVERNIGHT. LATEST GUIDANCE SUGGESTS
LOWS NEAR 50 ACROSS A GOOD PORTION OF THE NORTHEAST FORECAST AREA.
NOT OUT OF THE QUESTION WITH EASTERLY FLOW OFF LAKE ERIE AND DRY
AIRMASS...HOWEVER EXPECTED MID/HIGH CLOUDS SHOULD PREVENT TEMPS FROM
SUCH A DROP OFF...SO COMPROMISED WITH LOWER TEMPS SLIGHTLY BUT
STAYING ABOVE GUIDANCE.

FRONTAL BOUNDARY EXPECTED TO LINGER FROM WEST TO EAST ACROSS THE
AREA AGAIN TOMORROW. SIMILAR SETUP EXPECTED...WITH AFTERNOON
INSTABILITY LEADING TO SMALL PRECIPITATION CHANCES. ALTHOUGH MODEL
SBCAPE VALUES OF 1500 J/KG ARE EXPECTED TOMORROW...LACK OF
FLOW...WEAK FORCING AND POOR LAPSE RATES SHOULD LIMIT WIDESPREAD
PRECIPITATION CHANCES. KEPT HIGHEST CHANCES ACROSS SOUTHEAST AREAS
IN THE AFTERNOON...IN CLOSEST VICINITY OF SUBTLE MID LVL IMPULSE AND
HIGHEST MOISTURE/INSTABILITY VALUES.

&&

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 318 PM EDT FRI MAY 17 2013

FCST PERIOD TO BEGIN MAINLY DRY AS 500MB RIDGE MOVES OVER THE AREA.
FLOW WILL BECOME MORE SOUTHERLY DURING THE DAY SUNDAY AND BRING
INCREASING HUMIDITY AS DEWPOINTS RISE TO THE L-M60S. THIS WILL
RESULT IN INCREASING INSTABILITY DURING THE AFTERNOON HOURS AND
STEEPENING LOW LEVEL LAPSE RATES...BUT IN A WEAK FLOW POORLY FORCED
ENVIRONMENT...SO WILL CONTINUE WITH JUST SLIGHT CHANCE WORDING ON
SUNDAY. DECENT MID-UPPER JET DYNAMICS WILL ROUND THE BASE OF THE
UPPER TROF IN THE PLAINS AND SHOULD PROVIDE NEEDED FORCING FOR
NOCTURNAL CONVECTION IN THE MID MS VALLEY SUNDAY NIGHT. PLENTY OF
ELEVATED INSTABILITY WILL BE PRESENT OVER THE CWA WITH CAPES AOA
2000J/KG. STAUNCH THICKNESS RIDGE AND NO INDICATION OF BREAKDOWN IN
THE MID LEVEL RIDGE SHOULD KEEP MOST OF THE CONVECTION WEST OF OUR
AREA BUT WILL STILL CONTINUE WITH SLIGHT CHANCE OVER WESTERN TWO
THIRDS. ANOTHER DAY OF DIURNALLY DRIVEN CONVECTION POSSIBLE ON
MONDAY AS AREA WILL SIT IN AN UNSTABLE AND RELATIVELY UNCAPPED WARM
SECTOR THAT WILL BE AIDED BY INCREASING LOW-MID LEVEL FLOW. FOCUS
THEN SHIFTS TO ARRIVAL...FINALLY...OF VERTICALLY STACKED SYSTEM
TUE-THU. THIS SYSTEM EXPECTED TO BE WEAKENING AS IT MOVES INTO THE
AREA WITH SFC REFLECTION BECOMING QUASI-STATIONARY WED-THU
TIMEFRAME. THIS WILL EXTEND PRECIP CHANCES THROUGH THE DAY THURSDAY
BEFORE FINALLY CLEARING OUT AND MAKING WAY FOR A COOLER DRIER
CANADIAN HIGH PRESSURE SYSTEM TO SETTLE INTO THE GREAT LAKES REGION
BEGINNING FRIDAY...AND HOPEFULLY LEAD TO A PLEASANT MEMORIAL DAY
WEEKEND. GENERALLY FAVORED WARMER TEMPS MAX AND MIN FOR SUN/MON AS
POTENT LOW LEVEL THERMAL RIDGE NUDGES INTO THE REGION AND INCREASING
HUMIDITY TO KEEP NIGHT TIME LOWS TRENDING WARMER. COOLER MORE
SEASONABLE TEMPS BY THE END OF THE PERIOD.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 109 PM EDT FRI MAY 17 2013

VFR CONDITIONS EXPECTED THROUGH THE TAF PD AT TERMINALS. LIGHT
EASTERLY FLOW WILL PERSIST WITH FRONTAL BOUNDARY SOUTH OF THE AREA
THROUGH THE PERIOD. AFTERNOON SHOWERS/ISOLATED STORMS ARE EXPECTED
TO DEVELOP SOUTH AND SOUTHWEST OF TERMINALS. LATEST MODEL GUIDANCE
SUGGESTS CONVECTION SHOULD REMAIN OUT OF TERMINALS...HOWEVER THERE
IS A SMALL CHANCE THAT DYING THUNDERSTORMS COULD ADVECT INTO THE
VICINITY OF TERMINALS...WITH A RISK OF -SHRA FROM 21Z THROUGH JUST
AFTER 00Z. CONFIDENCE TOO LOW TO INCLUDE -SHRA MENTION IN
TAFS...AND WILL MONITOR CONVECTIVE TRENDS THIS AFTERNOON AND
UPDATE TAFS AS NEEDED.


&&

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

$$

SYNOPSIS...FISHER/KG
SHORT TERM...NG
LONG TERM...JAL
AVIATION...NG


VISIT US AT WWW.WEATHER.GOV/IWX (ALL LOWER CASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.NORTHERNIN.GOV
WWW.TWITTER.COM/NWSIWX
WWW.YOUTUBE.COM/NWSNORTHERNINDIANA