Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 040034
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
834 PM EDT SUN MAY 3 2015

.SYNOPSIS...
ISSUED AT 312 PM EDT SUN MAY 3 2015

AN UPPER DISTURBANCE TRACKING ALONG THE CANADIAN BORDER WILL DRAG
A COOL FRONT SOUTHWARD ACROSS THE GREAT LAKES REGION. THIS FRONT
COMBINED WITH INCREASING MOISTURE WILL LIKELY PRODUCE SHOWERS AND
THUNDERSTORMS FROM LATE TONIGHT INTO MONDAY NIGHT. LOWS TONIGHT
WILL FALL BACK ONLY TO THE MIDDLE TO UPPER 50S. HIGHS ON MONDAY
WILL BE IN THE 70S.

&&

.UPDATE...
ISSUED AT 804 PM EDT SUN MAY 3 2015

CONVECTIVELY ENHANCED SHORT WAVE ACROSS NORTHERN ILLINOIS WILL
CONTINUE TO SLOWLY SPREAD ACROSS SOUTHWEST LOWER MICHIGAN OVER THE
NEXT FEW HOURS. MAIN SYNOPTIC AXIS OF LOW MOISTURE TRANSPORT
SHOULD REMAIN POSITIONED WEST OF THE AREA THROUGH THE REMAINDER OF
THE EVENING HOURS...WITH BETTER MOISTURE ADVECTION/TRANSPORT
WORKING INTO NORTHWEST THIRD OF THE AREA DURING THE OVERNIGHT
HOURS AS LOW LEVEL WINDS VEER IN RESPONSE TO SHORT WAVE TRACKING
ACROSS US/CANADIAN BORDER. SHORT TERM GUIDANCE MAY BE UNDERDOING
LOCALIZED STRONGER LOW LEVEL MOISTURE ADVECTION IMMEDIATELY IN
ADVANCE OF THIS MCV HOWEVER PER 30 KNOT 4-6K FT WINDS SAMPLED BY
KLOT WSR88D. DID SLIGHTLY NUDGE UP POPS ACROSS THE FAR NORTHWEST
INTO THE MID CHANCE RANGE THIS EVENING...BUT LESSENING
INSTABILITY/SHEAR EASTWARD SHOULD TEND TO SUPPORT OVERALL
DIMINISHING TREND TO THIS AREA OF RAIN/EMBEDDED THUNDER AS IT
MOVES IN THIS EVENING. WILL MONITOR TRENDS OVER THE NEXT HOUR AS
THIS AREA OF RAIN ENTERS LESS FAVORABLE ENVIRONMENT...BUT MAY NEED
ANOTHER EVENING UPDATE TO FURTHER INCREASE POPS FOR PORTIONS OF
NORTHWEST PORTIONS OF THE FORECAST AREA. SIGNIFICANT CHANGE MADE
TO POPS FOR THE OVERNIGHT GIVEN APPROACH OF NEXT UPSTREAM WAVE AND
BETTER MOISTURE ADVECTION.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 312 PM EDT SUN MAY 3 2015

FOCUS OF THE SHORT TERM PERIOD IS PRECIPITATION/THUNDERSTORM CHANCES
ASSOCIATED WITH AN INCOMING COLD FRONT.

AN UPPER LEVEL LOW DIGGING INTO NORTHERN ONTARIO THIS EVENING WILL
CONTINUE INTO QUEBEC THROUGH MONDAY. OUR CWA LIES ON THE NORTHERN
MOST FRINGES OF A RIDGE ALOFT...WHICH IS FIRMLY ANCHORED OVER THE
SOUTHEASTERN UNITED STATES. AS ALWAYS...WE WILL BE SUSCEPTIBLE TO
WEAK SHORTWAVE DISTURBANCES THAT MEANDER THROUGH THE NEARLY ZONAL
FLOW. SFC LOW PRESSURE TROUGH AND ASSOCIATED COLD FRONT DRAPED FROM
JAMES BAY TO THE DAKOTAS WILL DRIFT EASTWARD OVERNIGHT...FINALLY
REACHING OUR NW CWA BY LATE MONDAY MORNING...THEN STALLS IN THE
CENTRAL CWA IN THE AFTERNOON.

FOR TONIGHT THEN...MOISTURE TRANSPORT INCREASES OUT AHEAD OF THE
FRONT...ESPECIALLY AS SOUTH-SOUTHWEST WINDS BRING IN MOISTURE FROM
THE GULF REGION. LL REMAINS FAIRLY DRY UNTIL LATE TONIGHT
HOWEVER...SO EXPECT PRECIPITATION TO HOLD OFF FOR MOST AREAS UNTIL
MORNING HOURS.

OTHERWISE...PESKY MESOVORTEX SPINNING ACROSS ERN IOWA AND NORTHERN
IL WITH SHOWERS/T-STORMS THIS AFTERNOON IS SET TO LIFT NORTHEASTWARD
THROUGH THE EARLY EVENING HOURS. SOME MODELS BRING LIGHT PRECIP INTO
THE FAR WESTERN CWA ASSOCIATED WITH THIS FEATURE THIS EVENING...BUT
OTHERS TAKE IT TO OUR NORTH. KEPT A SLIGHT CHANCE OF RAIN SHOWERS TO
ACCOUNT FOR THIS...BUT NOT REALLY CONFIDENT. DRY AIR OVER OUR CWA IS
FAIRLY ENTRENCHED FOR NOW.

BEYOND THAT...MONDAY MORNING/MONDAY AFTERNOON STRONGER FORCING PER
850-500MB QVECTOR CONVERGENCE ARRIVES ALONG WITH PWAT VALUES
RANGING FROM 1 TO 1.5 INCHES. HAVE PRECIPITATION CHANCES GRADUALLY
INCREASING FROM THE NORTHWEST AFTER 06Z TONIGHT...THEN EXPANDING
INTO THE REST OF THE CWA MONDAY. KEPT HIGHEST POPS BETWEEN
15-00Z.

THUNDER APPEARS PROBABLE AS WELL...WITH AT LEAST 500 J/KG MUCAPE IN
THE AM...INCREASING TO UPWARDS OF 1000 J/KG IN THE AFTERNOON. AS FAR
AS THE SEVERE WEATHER THREAT...NOT EXPECTING ANYTHING SUBSTANTIAL AS
0-6KM BULK SHEAR IS LESS THAN 30 KNOTS FOR THE DAY. SPC STILL KEEPS
US IN THE MARGINAL CATEGORY...WHICH SEEMS REASONABLE GIVEN
INSTABILITY.

TEMPERATURE-WISE WE LOOK TO BE ON TRACK...WITH HIGHS A LITTLE BIT
COOLER FOR MONDAY COMPARED TO TODAY IN THE NORTHWEST...MAINLY DUE TO
CLOUD COVER/PRECIP AND WIND SWITCH TO THE WEST.

&&

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 312 PM EDT SUN MAY 3 2015

STG NRN STREAM SW CONTS TO CHURN EWD THROUGH THE NEPAC AND BY ALL
MODEL ACCOUNTS WILL DIG SWD INTO THE FOUR CORNERS AREA BY FRI BFR
EJECTING NEWD SOMETIME LT NEXT WEEKEND.

UNTIL THEN PRIMARY WX FTR OF INTEREST THIS PD IS TRAILING FNTL BNDRY
IN ASSOCN/W LEAD NRN STREAM DISTURBANCE SWINGING EWD THROUGH SRN
CANADA EARLY BFR IT WASHES OUT LT TUE. HIGHRES GUIDANCE WINDOW HAS
NOTHING TO BLD A CONSENSUS SOLUTION ON WHAT ARISES OUT OF GENERALLY
WEAK BACKGROUND FNTL SCALE ASCENT MON NIGHT OR TUE. MORE VIGOROUS
BUT WIDELY DISSPARATE HIGHRES OUTPUT TIED TO UNCERTAIN UPSTREAM
CONVECTIVE DVLPMNT ESP MON AFTN AND OVERNIGHT HERE. THUS WILL HOLD
W/PRIOR POP MON NIGHT-TUE.

AFT THAT...STG MID LVL RIDGE XPCD DOWNSTREAM OF DVLPG WRN TROUGHING
AND UPSTREAM OF SYS DVLPG OFF SE COAST. WARMING TREND SEEN IN PRIOR
MOS GUIDANCE LOOKS TO HAVE RUN ITS COURSE HWVR MID TEEN H85 TEMPS
FRI-SAT MAY YIELD MID 80S PENDING CLD CVR/PCPN EXTENT IF ANY.
CURRENT NUMBERS ALIGN WELL W/LATEST MOS GUIDANCE AND GENERALLY LEFT
ALONE.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 804 PM EDT SUN MAY 3 2015

A CONVECTIVELY ENHANCED VORT MAX TRACKING ACROSS NORTHERN ILLINOIS
WILL TRACK ACROSS EXTREME NORTHERN INDIANA LATER THIS EVENING.
RAIN AND EMBEDDED THUNDER WITH THIS VORT MAX WILL ENCOUNTER SOME
DRIER AIR ACROSS THE LOCAL AREA. MAY NEED TO ADD BRIEF MENTION OF
-SHRA AT KSBN LATE THIS EVENING...BUT BETTER CHANCE OF SHOWERS AND
ISOLATED THUNDER SHOULD HOLD OFF UNTIL OVERNIGHT AND INTO MONDAY
AS LOW LEVEL MOISTURE RAMPS UP AND NEXT SHORT WAVE APPROACHES.
NORTHERN STREAM WAVE TRACKING ACROSS THE GREAT LAKES WILL ALSO
ALLOW COLD FRONT TO SAG ACROSS THE LOWER GREAT LAKES. AT THIS
TIME...HAVE INCLUDED VCTS MENTION AT TERMINALS MONDAY AFTERNOON
WITH CONFIDENCE IN TIMING/OCCURRENCE STILL NOT HIGH ENOUGH FOR TS
INCLUSION FOR POINT FORECASTS. MVFR CONDITIONS ARE POSSIBLE ON
MONDAY...ESPECIALLY IN ASSOCIATION WITH HEAVIER
SHOWERS/STORMS...BUT WITH LOW CONFIDENCE IN TIMING AT THIS
FORECAST DISTANCE WILL MAINTAIN VFR CONDITIONS FOR ANOTHER CYCLE.

&&

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

$$

UPDATE...MARSILI
SYNOPSIS...MCD
SHORT TERM...MCD
LONG TERM...T
AVIATION...MARSILI


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