Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 302337
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
737 PM EDT THU JUL 30 2015

.SYNOPSIS...
ISSUED AT 122 PM EDT THU JUL 30 2015

HIGH PRESSURE OVER THE CENTRAL PLAINS WILL DRIFT EAST TONIGHT
CONTINUING TO PROVIDE FAIR WEATHER ACROSS OUR AREA. A WEAK COLD
FRONT WILL MOVE SOUTHEAST ACROSS THE GREAT LAKES FRIDAY AFTERNOON
AND EVENING... POSSIBLY CAUSING ISOLATED THUNDERSTORMS.
TEMPERATURES WILL BE NEAR NORMAL FOR LATE JULY WITH LOWS TONIGHT
MAINLY IN THE LOWER 60S AND HIGHS FRIDAY GENERALLY IN THE MID 80S.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 248 PM EDT THU JUL 30 2015

ALOFT THE CWA IS UNDER RELATIVELY ZONAL FLOW/WEAK TROUGHING...AS THE
AREA RESTS BETWEEN A BUILDING RIDGE IN THE WEST AND A CLOSED LOW
OVER HUDSON BAY. AT THE SFC...SPRAWLING HIGH PRESSURE EXTENDING FROM
THE CANADIAN PRAIRIES SOUTHEASTWARD INTO KENTUCKY/TENNESSEE WILL
CONTINUE TO EXPAND NORTH AND EAST OVERNIGHT. AS A RESULT...WEATHER
WILL REMAIN SETTLED THROUGH FRIDAY MORNING. WINDS WILL DIE DOWN
EARLY THIS EVENING AS THE PRESSURE GRADIENT SLACKENS AND WE LOSE
DAYTIME MIXING. OVERNIGHT LOWS WILL BE IN THE 60S.

LATE FRIDAY AFTERNOON...A WEAK SHORTWAVE SWINGS THROUGH THE FLOW
ALOFT...THOUGH A MAJORITY OF THE FORCING WITH THIS WAVE IS TO THE
NORTHEAST PER 850-500MB QVECTOR DIV. AT THE SFC...VERTICALLY STACKED
LOW PRESSURE OVER HUDSON BAY WILL BRING A COLD FRONT AND PRE-FRONTAL
TROUGH TO THE AREA. BY FRIDAY EVENING/AFTERNOON...PRE-FRONTAL TROUGH
IS SITUATED ACROSS THE EASTERN CWA WITH THE COLD FRONT IN ITS
WAKE...EXTENDING FROM NE LOWER MI...ACROSS LAKE MICHIGAN...AND
NORTHERN IL/IA. ON THE FENCE AS FAR AS PRECIPITATION GOES FOR THE
EASTERN HALF LATE FRIDAY AFTERNOON. ON THE POSITIVE SIDE...THE
TROUGH ARRIVES DURING PEAK HEATING...SO INSTABILITY IS ABUNDANT/PER
ML CAPE OF 1500-2000 J/KG. 0-6KM SHEAR IS IN THE 30-35 KNOT RANGE.
AS FAR AS THE NEGATIVES...STRENGTH OF TROUGH/FRONT IS FAIRLY WEAK.
MOISTURE IS SOMEWHAT LACKING AS WELL...WITH PWATS AROUND 1.2 INCHES.
MODELS ARE SOMEWHAT CONFLICTED IN TERMS OF HOW EVERYTHING PLAYS
OUT...WITH SOME GENERATING PRECIPITATION ALONG THE FRONT DURING THE
AFTERNOON ACROSS THE SOUTHERN AND EASTERN CWA. NAM/GFS KEEP
PRECIPITATION IN THE EAST-NORTHEAST AS WOULD BE EXPECTED GIVEN BEST
FORCING/INSTABILITY. IF ANYTHING DOES HAPPEN...THINK IT WILL BE
CLOSE TO THE EASTERN-MOST SOLUTION IN THE 18-00Z TIME FRAME...BUT
GIVEN MODEL CONFLICTS...RELATIVELY DRY AIR...AND WEAK FORCING
CONFIDENCE IS LOW. ADDED SLIGHT CHANCE POPS INTO THIS TIME PERIOD
ACCORDINGLY.

&&

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 248 PM EDT THU JUL 30 2015

CLOSED UPPER LOW TO REMAIN NEAR HUDSON BAY INTO EARLY NEXT WEEK
WHILE UPPER RIDGE OVER THE CENTRAL CONUS BUILDS WEST AND NORTH.
THIS LEAVES OUR AREA STUCK IN NORTHWEST FLOW FOR MUCH OF THE
PERIOD WITH NUMEROUS SMALL SCALE SHORT WAVES THROUGH THE PERIOD.
THIS WILL PROVE DIFFICULT IN TERMS OF PCPN CHANCES WITH TIMING AND
STRENGTH ISSUES. MODELS STRUGGLING WITH THESE DIFFERENCES AND AS A
RESULT THERE ARE VARYING SOLUTIONS. PERSISTENCE REMAINS THE KEY IN
THE LONG TERM AND HAVE RELUCTANTLY ACCEPTED SUPERBLEND AND
INHERITED POPS MOST PERIODS FOR NOW WITH STALLED FRONTAL BOUNDARY
NEARBY AND THESE SHORT WAVES. BEST CHANCES WILL COME WITH ANY
CONVECTIVELY ENHANCED WAVES THAT DEVELOP UPSTREAM AND MOVE IN MEAN
FLOW ACROSS THE AREA. TEMPERATURES WILL TREND TOWARD BELOW NORMAL
AS HEAT WILL BE CONFINED WELL TO OUR SOUTHWEST AND PREVAILING
NORTHWEST FLOW CONTINUES HERE.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 723 PM EDT THU JUL 30 2015

DRY AIRMASS OVER THE AREA WITH W-NW FLOW ALOFT IS EXPECTED TO RESULT
IN VFR CONDITIONS CONTG THROUGH THE PERIOD. A SHRTWV/CDFNT WILL DROP
SE FROM MANITOBA THIS EVE TO THE GRTLKS FRI EVE. LIMITED MOISTURE
EXPECTED TO ACCOMPANY THIS SYSTEM SO EXPECT ISOLATED TSTMS AT
MOST AS THE SYSTEM MOVES THROUGH THE AREA FRI AFTN/EVE. WITH
CHANCES OF TS IMPACTING TERMINALS VERY LOW... DID NOT INCLUDE ANY
MENTION IN TAFS.

&&

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

$$

SYNOPSIS...JT
SHORT TERM...MCD
LONG TERM...LASHLEY
AVIATION...JT


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