Area Forecast Discussion
Issued by NWS Northern Indiana

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KIWX 211019 AAA
AFDIWX

AREA FORECAST DISCUSSION...CORRECTION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
611 AM EDT THU AUG 21 2014

.SYNOPSIS...
ISSUED AT 152 AM EDT THU AUG 21 2014

PERIODIC SHOWERS AND THUNDERSTORMS ARE POSSIBLE INTO FRIDAY AS A
WARM FRONT SLOWLY MOVES NORTH INTO THE AREA. HEAT AND HUMIDITY
WILL RETURN BY FRIDAY AS THIS FRONT MOVES NORTH. HIGHS TODAY WILL
BE IN THE LOWER TO MID 80S. LOWS THE NEXT SEVERAL NIGHTS WILL BE
AROUND 70. HIGHS THIS WEEKEND WILL BE AROUND 90 DEGREES.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 449 AM EDT THU AUG 21 2014

UPPER LEVEL JET DYNAMICS COMBINED WITH THE LEADING EDGE OF THETA E
CONVERGENCE WAS HELPING TO TRIGGER ISOLATED STORMS AND AN AREA OF
SHOWERS NORTH OF THE FRONT. THE STORMS WERE HIGH BASED EARLY THIS
MORNING...BUT SHOULD BECOME MORE SURFACE BASED AS THE FRONT MOVES
NORTH AND AS THE ATMOSPHERE DESTABILIZES WITH DAYTIME HEATING LATER
TODAY. THETA E FLUX WILL INCREASE TONIGHT...WITH A BETTER CHANCE FOR
SHOWERS AND STORMS AS AN UPPER LEVEL DISTURBANCE TOPS THE UPSTREAM
RIDGE AND MOVES INTO THE WESTERN GREAT LAKES REGION. THE 12KM NAM
APPEARED TO HAVE A REASONABLE HANDLE ON THE TIMING OF THIS UPSTREAM
SYSTEM AND THE TRACK OVER THE UPPER LEVEL RIDGE...SO HAVE LIKELY
THUNDERSTORM CHANCES LATER TONIGHT. SEVERE STORMS ARE POSSIBLE GIVEN
DEEP LAYER SHEAR TOPPING OUT AT 30 TO 40 KNOTS. HAVE RAISED HIGHS
TODAY. THE NAM/MET HAS RAISED HIGHS TODAY 5 DEGREES AT SBN AND
APPEARS ON TRACK...COMING MORE IN LINE WITH THE GFS/MAV. 850 MB
TEMPS WILL BE BETWEEN 18C AND 19C TODAY...AND SOME SUN TODAY SHOULD
ALLOW HIGHS TO RISE TO BETWEEN 82F AND 86F.

&&

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 449 AM EDT THU AUG 21 2014

MAIN CONCERN THIS PERIOD IS POTENTIAL FOR EXCESSIVE HEAT AS STRONG
UPR LEVEL RIDGE BUILDS INTO THE AREA RESULTING IN HEAT INDEX
READINGS IN THE 90S EACH AFTN. ALTHOUGH THESE READINGS ARE A BIT
BLO OUR ADVISORY CRITERIA... IMPACTS MAY BE GREATER THAN USUAL DUE
TO EXPECTED RATHER LONG DURATION OF THE HEAT WAVE... AND
DIFFICULTY FOR PEOPLE TO BECOME ACCLIMATED TO THE HEAT GIVEN
ABNORMALLY COOL TEMPS THUS FAR THIS SUMMER.

CONVECTION AT NOSE OF A WK WLY LLJ MAY BE ONGOING IN OUR AREA AT
THE START OF THE PERIOD FRIDAY MORNING. WK LOW LEVEL WAA PATTERN
AND STNRY SFC BOUNDARY DRAPED ACROSS NERN PORTION OF THE CWA
EXPECTED FRI WHICH MAY PROVIDE FOCUS FOR REDEVELOPMENT IN THE AFTN
AS AIRMASS DESTABILIZES. THIS BOUNDARY EXPECTED TO REMAIN OVER THE
AREA FRI NGT WITH NOSE OF WSWLY LLJ OVER THE MID MS VALLEY
PROVIDING FORCING FOR CONVECTION UPSTREAM OVERNIGHT WHICH COULD BE
SUSTAINED INTO OUR AREA GIVEN LINGERING WK/MODERATE ELEVATED
INSTABILITY. RATHER STRONG NWLY UPR LEVEL FLOW ON EAST SIDE OF MS
VALLEY RIDGE WILL PROVIDE DECENT DEEP LAYER SHEAR FRI/FRI
NGT...ESPECIALLY OVER ERN PORTIONS OF THE CWA WHICH ALSO COULD AID
IN CONVECTIVE PERSISTENCE AS WELL AS SUPPORT A FEW STRONG/SVR
STORMS AROUND PEAK HEATING FRI AFTN/EVE. DOUBT CONVECTION WILL BE
SUFFICIENTLY WIDESPREAD OR LAST LONG ENOUGH TO HOLD TEMPS DOWN
SIGNIFICANTLY FRIDAY. GIVEN H85 TEMPS PROGGED IN THE 19-20C RANGE
STAYED CLOSE TO PREVIOUS FCST WITH HIGHS RANGING FROM THE M80S NE
TO AROUND 90 SW. DWPTS SHOULD ALSO BE RISING TO THE L-M70S WHICH
WILL RESULT IN AFTN HEAT INDICES ABOUT 5-10F HIGHER THAN TEMPS.
LIGHT WINDS FRI NGT SHOULD ALLOW FOR SOME RADIATIONAL COOLING SO
EXPECT MINS TO BE IN THE U60S NE AND L70S SW.

SIMILAR CONDITIONS EXPECTED SATURDAY. UPR RIDGE AXIS SHOULD MOVE
SLIGHTLY EAST INTO OUR AREA AS STRONG TROF MOVES ACROSS THE NRN
ROCKIES. E-W ORIENTED SURFACE BOUNDARY WILL LIKELY REMAIN OVER THE
AREA PROVIDING SOME FOCUS FOR CONVECTION AS AIRMASS DESTABILIZES
DURING THE DAY. WK LOW LEVEL GRADIENT WINDS AND VERY MOIST AIRMASS
OVER THE AREA SHOULD AGAIN LIMIT HEATING BUT EXPECT SUFFICIENT
MIXING TO ALLOW FOR HIGHS CLOSE TO FRIDAYS READINGS AS SUGGESTED BY
MAV MOS TEMPS.

STNRY SFC BOUNDARY SHOULD LIFT NORTH OF OUR CWA SAT NGT-SUNDAY AS
SFC LOW DEEPENS OVER THE NRN PLAINS. THIS SHOULD RESULT IN MAINLY
DRY CONDITIONS BY SUNDAY WITH TEMPS CONTG TO SLOWLY WARM. NRN PLAINS
LOW EXPECTED TO LIFT NE-E INTO ONTARIO MONDAY AND TO QUEBEC TUE WITH
TRAILING WK CDFNT DROPPING SOUTH INTO OUR AREA BY THAT TIME. SOME
SUPPRESSION OF UPR RIDGE PER ECMWF SOLUTION SEEMS APPROPRIATE AS
SHRTWV BREAKS OVER THE TOP ACROSS THE UPR GRTLKS...  SO WKNG CAPPING
INVERSION/CHC TSTMS... AND SLIGHTLY LOWER TEMPS FCST BY TUE. MEDIUM
RANGE MODELS DIFFERING SOLUTIONS WRT PERSISTENCE OF UPR RIDGE TUE
LEADING TO EVEN GREATER DIFFERENCES BY WED WITH ECMWF SUGGESTING
RIDGING BUILDING BACK INTO OUR REGION AS CLOSED LOW DEVELOPS IN
THE WRN U.S., WHILE GFS FCSTG MORE PROGRESSIVE WRN TROF WITH A STRONG
SHRTWV APPROACHING THE MIDWEST BY WED EVE. GIVEN LARGE DIFFERENCES
STAYED CLOSE TO PREVIOUS FCST WHICH WAS FOR CONTD SLOW COOLING
TREND AND A LOW CHC OF TSTMS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 553 AM EDT THU AUG 21 2014

UPPER LEVEL JET DYNAMICS WERE HELPING TO TRIGGER STORMS IN AN AREA
FROM SOUTHERN WI INTO NW INDIANA. HAVE KEPT THE BULK OF THE
TIMING OF THE STORMS IN THE ONGOING TAFS...AND HAVE KEPT THUNDER
TONIGHT. THETA E FLUX WILL INCREASE TONIGHT...WITH MORE WIDESPREAD
ACTIVITY EXPECTED AS AN UPPER LEVEL SYSTEM DROPS SOUTHEAST INTO
THE AREA.

&&

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

$$

SYNOPSIS...SKIPPER
SHORT TERM...SKIPPER
LONG TERM...JT
AVIATION...SKIPPER


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

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











USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.