Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 120055
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
855 PM EDT FRI JUL 11 2014

.SYNOPSIS...
ISSUED AT 504 PM EDT FRI JUL 11 2014

HIGH PRESSURE WILL BE OVER THE REGION INTO TOMORROW. SOME LIGHT
RAIN IS MOVING EASTWARD ACROSS LAKE MICHIGAN AND WILL NOT LAST
LONG. THEN THE REST OF TONIGHT WILL BE DRY WITH LOW TEMPERATURES
RANGING FROM THE LOWER 60S IN WESTERN OHIO TO THE MIDDLE 60S IN
WESTERN INDIANA. THE NEXT SHOWER AND THUNDERSTORM CHANCES WILL
MOVE BACK IN TOWARDS EARLY MORNING AND SPREAD ACROSS THE REGION
THROUGHOUT TOMORROW. HIGH TEMPERATURES TOMORROW WILL RANGE FROM
THE LOWER 80S IN THE NORTH TO THE MIDDLE 80S NEAR THE OHIO RIVER.

&&

.UPDATE...
ISSUED AT 829 PM EDT FRI JUL 11 2014

A WEAK UPPER LEVEL SHORT WAVE TRACKING ACROSS SOUTHERN
WISCONSIN/NORTHERN ILLINOIS AND ASSOCIATED LOW LEVEL THETAE
ADVECTION HAS BEEN ENOUGH TO ALLOW SOME SCATTERED LIGHT
RAIN SHOWERS OR SPRINKLES TO SURVIVE INTO FAR NORTHWEST PORTIONS
OF THE AREA. SHOULD SEE A CONTINUED DIMINISHMENT TO THE EXTENT OF
THESE SHOWERS/SPRINKLES OVER THE NEXT FEW HOURS...ALTHOUGH ANOTHER
SMALL SCALE WAVE TRACKING INTO SOUTHWEST PORTIONS OF THE AREA MAY
ALLOW SOME SCATTERED SHOWERS TO AFFECT THESE LOCATIONS LATE THIS
EVENING...BUT AGAIN WITH VERY LITTLE IN THE WAY OF MEASURABLE
RAIN. ATTENTION FOR THE OVERNIGHT THEN TURNS TO NEXT UPSTREAM LOW
AMPLITUDE WAVE TRACKING CROSS CENTRAL/EASTERN IOWA. STRONGER W-SW
LOW LEVEL FLOW SHOULD ACCOMPANY THIS WAVE...WITH STRONGER LOW
LEVEL THETAE SURGE EXPECTED INTO WESTERN PORTIONS OF THE AREA
TOWARD MORNING. HAVE INCLUDED SOME LOW CHANCE -SHRA POPS ACROSS
THE FAR WEST TO ACCOUNT FOR THIS...WITH BETTER CHANCE OF THUNDER
LIKELY REMAINING WEST OF THE FORECAST AREA. UPDATED ZONES SENT TO
ACCOUNT FOR EVENING SPRINKLES...AND LATE CHANCE POPS ACROSS THE
WEST...BUT OTHERWISE NO SIGNIFICANT CHANGES MADE.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 352 PM EDT FRI JUL 11 2014

THE MAIN CHALLENGES THIS PERIOD ARE LATE TONIGHT AND SATURDAY
CONCERNING THE DEVELOPMENT...TIMING AND COVERAGE OF SHOWERS AND
THUNDERSTORMS. AT THE START OF THIS PERIOD...AREAS OF DIURNAL
CUMULUS HAVE DEVELOPED THIS AFTERNOON OVER THE FORECAST AREA. THESE
CLOUDS SHOULD DISSIPATE THIS EVENING WITH THE LOSS OF DAYTIME
HEATING. A WEAK PRESSURE GRADIENT WILL REMAIN OVER THE AREA
TONIGHT...WITH LIGHT WINDS. VERY LOW CONFIDENCE IN TIMING OF SHOWERS
AND STORMS GIVEN GENERALLY POOR WPC MODEL INITIAL AND VERIFICATION
OF UPSTREAM CONVECTION. ALSO...MODELS NOT HANDLING UPSTREAM SHORT
WAVE ENERGY VERY WELL EITHER. HAVE ATTEMPTED TO USE A BLEND OF
SEVERAL MODELS...FAVORING THE SRF WITH 5 MODEL CORES TO HELP
MINIMIZE THE EFFECT OF OUTLIERS. CONCERN FOR THE ONGOING DRY
FORECAST LATE TONIGHT...ESPECIALLY WITH PRECIPITABLE WATER VALUES
APPROACHING 2 INCHES LATE. GIVEN LOW CONFIDENCE...HAVE LEFT THE
FORECAST DRY TONIGHT. HAVE TRENDED STORM CHANCES PROGRESSIVELY
HIGHER DURING THE DAY SATURDAY AT THE ATMOSPHERE DESTABILIZED WITH
DAYTIME HEATING. SEVERE WEATHER POTENTIAL LOOKS MORE MARGINAL.
HOWEVER...GIVEN THE HIGH PRECIPITABLE WATER VALUES AND A DEEP WARM
CLOUD LAYER...LOCALLY HEAVY RAINFALL WITH LOCAL FLOODING IS POSSIBLE
WITH THE STRONGER STORMS...ESPECIALLY OVER AREAS STORMS MAY TRAIN.

&&

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 352 PM EDT FRI JUL 11 2014

...THUNDERSTORM POTENTIAL AND DEPTH/DURATION OF COLD AIR REMAIN
FRONT AND CENTER FOR LONG TERM...

INITIAL FOCUS WILL BE ON HANDLING OF ONE OR MORE POTENTIAL CHANCES
FOR THUNDERSTORMS AS SERIES OF WAVES AND ASSOCIATED SFC BOUNDARIES
MOVE THROUGH THE REGION. MANY OF THE HIGH RES MODELS CONTINUE TO
STRUGGLE WITH DAY TO DAY HANDLING OF VARIOUS COMPLEXES AND THEIR
EVOLUTION EAST TOWARDS THE GREAT LAKES MAKING THE NEXT COUPLE OF
DAYS THAT MORE CHALLENGING. CONSENSUS TO SOME DEGREE IS BEGINNING TO
SHOW UP AS ALL SIGNS POINT TOWARDS A COLD FRONT SINKING SOUTH
TOWARDS THE AREA SAT NGT INTO SUNDAY IN ASSOCIATED WITH FIRST
WAVE/JET STREAK WHICH WILL CONTINUE TO CARVE OUT A RATHER STRONG
TROUGH AND USHER IN THE ADVERTISED COLDER AIR. AS THIS WAVE
APPROACHES...LOW LEVEL JET WILL INCREASE AND FEED PLENTY OF MOISTURE
AND AT LEAST MODEST INSTABILITY. BIG QUESTION STILL HINGES ON
EFFECTS OF ANY CONVECTION TONIGHT INTO SATURDAY AND POTENTIAL FOR
INCREASED INSTABILITY AND SUBSEQUENT THREAT FOR STORMS. AGREE WITH
PREV SHIFT THAT GREATER CONCERN LIKELY LIES WITH THE INCREASED MSTR
AND EFFICIENT RAIN PRODUCING CONVECTION THAT WILL MATERIALIZE.
SEVERE THREAT WILL HINGE ON OTHER NOTED ITEMS WITH DAY 2 SPC OUTLOOK
SUMMARIZING NICELY. WILL HOLD WITH LIKELY POPS IN PARTS OF THE AREA
SAT NGT INTO SUNDAY. HAVE TRIED TO ADD A BIT MORE TIMING SAT EVENING
TO ANY COMPLEX THAT APPROACHES. WITH MAIN FRONT AND WAVE NOT PUSHING
THROUGH TILL SUNDAY COULD BE A INCREASED POTENTIAL FOR HEAVY
RAINFALL IN NW AREAS. SOMETHING TO MONITOR AT THIS POINT.

ONCE THE FIRST WAVE AND FRONT PASS...THINGS MAY QUIET DOWN WITH BEST
THETA E AXIS BEING SHIFTED EAST. THIS LEAVE PRECIP CHANCES IN
QUESTION WITH MAIN COLD FRONT LATE SUNDAY NIGHT INTO MONDAY. WITH
THE UPPER LOW INTENSIFYING AND A DECENT SFC LOW EXPECTED STILL THINK
SCATTERED SHOWERS AND POSSIBLY SOME THUNDERSTORMS WILL OCCUR ALONG
AND AHEAD OF THE FRONT. SVR RISK MAY BE LESSENED WITH LESS
INSTABILITY...BUT DYNAMICS OF OVERALL SETUP COULD MAKE UP FOR
THINGS. HAVE MAINTAINED CHC POPS FOR NOW.

TRENDS CONTINUE TO LOOK FOR A BRIEF BUT COLD SNAP FOR MID JULY AS
BLAST OF UNSEASONABLY COLD AIR DROPS OUT OF CANADA INTO THE GREAT
LAKES AND EASTERN PLAINS. COLDEST NIGHTS WILL BE TUESDAY AND WEDS
NGT WITH TEMPS IN THE 50S AND LIKELY SOME AREAS DROPPING INTO THE
UPPER 40S. HIGHS TUESDAY WILL BE THE COLDEST WITH MODEL CONSENSUS
SHOWING A DOWNWARD TREND. WENT WITH CONSALL GUIDANCE WHICH GAVE
HIGHS IN NW AREAS IN THE UPR 60S (RAW ALONG THE LAKE SHORE) TO MAYBE
70 SE. SLOW MODERATION WILL TAKE PLACE TOWARDS THE END OF THE WEEK
AS THE UPPER LOW PULLS AWAY. WITH SUCH A DRY AIRMASS...WILL TAKE
SOME TIME TO GET MSTR BACK INTO THE REGION SO HAVE WENT WITH DRY
FORECAST.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 829 PM EDT FRI JUL 11 2014

SEVERAL SMALL SCALE WAVES EMBEDDED IN PROGRESSIVE WESTERLY FLOW
HAVE ALLOWED FOR SOME SCATTERED SPRINKLES/LIGHT RAIN SHOWERS FROM
NORTHEAST ILLINOIS INTO NORTHERN INDIANA THIS EVENING. CURRENTLY
NOT EXPECTING MEASURABLE PRECIP AT THE TERMINALS THIS EVENING DUE
TO INITIALLY DRY SUBCLOUD LAYER. ANOTHER VORT MAX KICKING OUT OF
EASTERN IOWA LATER TONIGHT WILL LIKELY BE ACCOMPANIED BY STRONGER
LOW LEVEL THETAE ADVECTION AND LIKELY GREATER SHOWER/STORM COVERAGE
ACROSS NORTHERN ILLINOIS. THESE SHOWERS WILL LIKELY TO SURVIVE
INTO NORTH CENTRAL INDIANA SATURDAY MORNING BUT WITH RELATIVELY
LOW CONFIDENCE IN TIMING AT THIS FORECAST DISTANCE WILL CONFINE
MENTION TO VCSH. GREATER PROBABILITY OF THUNDER WILL LIKELY HOLD
OFF UNTIL JUST AFTER THIS FORECAST VALID PERIOD AS LARGER SCALE
UPPER TROUGH APPROACHES MID/UPPER MS RIVER VALLEY. HAVE HELD OFF
ON INCLUSION OF ANY MVFR CIGS...BUT SOME PROBABILITY EXISTS FOR A
PERIOD OF MVFR CIGS IN THE 12Z-16Z TIMEFRAME AT KSBN IN
ASSOCIATION WITH STRONGER LOW LEVEL MOISTURE ADVECTION.

&&

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

$$

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


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