Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 251656
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1256 PM EDT MON APR 25 2016

.SYNOPSIS...
ISSUED AT 1217 PM EDT MON APR 25 2016

INCREASING SOUTHWESTERLY WINDS WILL HELP DRAW IN WARMER AND
INCREASINGLY HUMID AIR TO HELP SET THE STAGE FOR SHOWERS AND
THUNDERSTORMS...MAINLY DURING THE EVENING HOURS. WARMER AIR WILL
SPREAD NORTHEAST INTO OUR AREA AHEAD OF A COLD FRONT. HIGHS SHOULD
REACH THE UPPER 70S TO AROUND 80. A COLD FRONT WILL MOVE INTO OUR
AREA TONIGHT WITH A GOOD CHANCE FOR SHOWERS AND THUNDERSTORMS.
SOME STORMS MAY BE STRONG TO POSSIBLY SEVERE. LOWS TONIGHT WILL
RANGE FROM 55 TO 60.

&&

.UPDATE...
ISSUED AT 1216 PM EDT MON APR 25 2016

DIFFICULT FORECAST FOR THE NEXT 6 TO 12 HOURS AS MODELS CONTINUE
TO STRUGGLE WITH POTENTIAL EVOLUTION OF CONVECTION BOTH UPSTREAM
AND OVER THE FORECAST AREA AHEAD OF A APPROACHING COLD FRONT.

HRRR HAS BECOME MORE AGRESSIVE WITH DEVELOPMENT OF SCATTERED CONVECTION
BACK ACROSS ILLINOIS IN THE 20 TO 22Z WINDOW MOVING RAPIDLY EAST
AND EXPANDING/ELONGATING INTO A LINE OF STRONG (SEVERE?) STORMS
THAT APPROACH FAR W/NW AREAS AS EARLY AS 00Z. IF THIS WERE TO COME
TO FRUITION...A MORE FAVORABLE SETUP FOR ISOLATED TO MAYBE SCT
SEVERE STORMS WOULD OCCUR AS SOMEWHAT BETTER INSTABILITY WILL BE
IN PLACE. NAM 4KM GIVES A SIMILAR SCENERIO IN TERMS OF STG/LOCALLY
SEVERE STORMS BUT STICKS CLOSER TO THE 3-4Z ARRIVAL WINDOW IN THE
FAR NW. RAP SORT OF IN BETWEEN BUT RATHER NON DESCRIPT IN
HANDLING. TO COMPLICATE THINGS FURTHER...15Z HRRR SHOWS WIDELY
SCATTERED SHOWERS/STORMS DEVELOPING IN THE 18 TO 20Z TIME FRAME
WELL AHEAD OF EVERYTHING. LOOKING OUTSIDE...CU ALREADY STARTING TO
FORM SUGGESTING MID LEVEL INSTABILITY MAY BE INCREASING AND COULD
BE SUFFICENT TO SPARK OFF SOME CONVECTION. SPC MESO ALSO SHOWING A
FEW HUNDRED J/KG OF MLCAPE ACROSS THE AREA. TO ADD TO THE
MIX...SPC HAS EXPANDED THE SLGT RISK EASTWARD FROM ROUGHLY
NORTHWEST OF A MONTICELLO TO WARSAW TO WAUSEON OHIO LINE. CHANGES
IN POPS/WX WILL BE NEEDED OVER THE NEXT COUPLE OF HOURS.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 408 AM EDT MON APR 25 2016

A SURFACE LOW WILL TRACK EAST INTO THE UPPER MIDWEST TODAY. DEEP
MIXING WITH A TIGHTENING SURFACE PRESSURE GRADIENT ASSOCIATED WITH
THIS SYSTEM WILL CAUSE WINDY CONDITIONS OVER THE FORECAST AREA.
RAISED WIND SPEEDS A LITTLE IN LINE WITH THE LATEST MODEL GUIDANCE.
FAVORED THE GFS TREND THE PAST SEVERAL RUNS TOWARD A SLOWER AND MORE
NORTHWEST LOW TRACK SOLUTION. NOT MUCH FORCING FOR STORMS TODAY...
BUT INCREASING MOISTURE WITH DAYTIME HEATING MAY BE SUFFICIENT TO
SUPPORT SOME SHOWERS OVER LOWER MICHIGAN INTO FAR NORTHERN INDIANA.

THERE IS A MUCH BETTER CHANCE FOR SHOWERS AND STORMS TONIGHT AS
LOW LEVEL MOISTURE SURGES NORTHEAST AHEAD OF A COLD FRONT. THE
STORM PREDICTION CENTER INDICATED SOME STORMS MAY BE MARGINALLY
SEVERE OVERNIGHT. AN ELEVATED MIXED LAYER WILL BE IN PLACE
OVERNIGHT AS A FRONT APPROACHES. SURFACE BASED NAM CAPES SHOULD
RISE ABOVE 500 J/KG AS FAVORABLE 0-3KM SHEAR RISES TO 40 M/S. SO
BEST CHANCE FOR STORMS APPEARS TO BE FROM LATE EVENING UNTIL ABOUT
4 AM EDT WITH SOME STORMS STRONG TO POSSIBLY SEVERE DURING THIS
PERIOD.

&&

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 408 AM EDT MON APR 25 2016

SEVERAL SHORT WAVES EXPECTED TO IMPACT THE REGION DURING THIS LONG
TERM PERIOD. CONFIDENCE IN DETAILS LOW GIVEN MODEL PERFORMANCE AND
WAVERING WITH THIS FIRST SHORT WAVE TO START THE WEEK. BEST CHANCES
FOR PCPN LOOKS TO BE WEDNESDAY WITH ANOTHER STRONG SHORT WAVE AND
SFC LOW MOVING SOUTH OF THE AREA. STILL MODEL DISCREPANCIES WITH
STRENGTH AND TRACK OF THIS FEATURE. DID ALLOW LIKELY POPS TO
CONTINUE BUT NOT CONFIDENT ENOUGH IN CATEGORICAL YET. BASICALLY
FOLLOWED SUPERBLEND IN DAYS 4-7 WITH SLIGHT LOWERING OF POPS FROM
LIKELY TO CHANCE GIVEN UNCERTAINTY WITH CONVECTION AND STACKED
SYSTEM IN PLAINS LATE WEEK LIKELY COMING OUT SLOWER THAN MODEL
FORECAST. TEMPS WILL TREND COOLER WED AND THU WITH EASTERLY FLOW AND
PCPN CHANCES. TEMPS WILL TREND BACK TO NEAR NORMAL LATE WEEK INTO
THE WEEKEND AHEAD OF NEXT WAVE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1216 PM EDT MON APR 25 2016

WINDS HAVE BEEN STRUGGLING TO PICK UP AS PATCHES OF CLOUDS MOVE
THROUGH. SHOULD SEE BETTER MIXING TAKE PLACE THIS AFTERNOON AS
SOME CLEARING TAKES PLACE.

ATTENTION WILL THEN SHIFT TO EXPECTED UPSTREAM DEVELOPMENT OF AT
LEAST SCATTERED SHOWER/STORM ACTIVITY WHICH WILL MOVE EAST AND
LIKELY EXPAND/INTENSIFY AS IT APPROACHES THE AREA. MODELS VARYING
ON TIMING WITH ONE MODELS BRINGING STORMS INTO KSBN AS EARLY AS 1Z
WHILE OTHERS HOLD CLOSER TO 3-4Z WINDOW. MAY ADJUST TIMING BY AN
HOUR OR SO...BUT UNTIL DEVELOPMENT OCCURS DON`T WANT TO MAKE TOO
MANY CHANGES WITH AMENDMENT ISSUED ONCE PICTURE IS CLEARER. ONCE
THE COLD FRONT MOVES THROUGH...RAPIDLY IMPROVING CONDITIONS SHOULD
DOMINATE.

&&

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

$$

UPDATE...FISHER
SYNOPSIS...JT/SKIPPER
SHORT TERM...SKIPPER
LONG TERM...LASHLEY
AVIATION...FISHER


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