Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 040548
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
148 AM EDT MON MAY 4 2015

.SYNOPSIS...
ISSUED AT 142 AM EDT MON 4 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 LATER TODAY INTO TUESDAY. LOWS THIS MORNING WILL
FALL BACK ONLY TO THE UPPER 50S. HIGHS LATER TODAY WILL PRIMARILY
BE IN THE MIDDLE TO UPPER 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 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 139 AM EDT MON MAY 4 2015

STRONGLY ANTICIPATE RAPID DECAY OF UPSTREAM CONVECTION BEFORE
REACHING NWRN IN AS LARGELY TIED WITHIN PREFERENTIAL RICHER
THETA-E RIBBON AND LOW LEVEL JET FOCUS THAT SHIFTS SWWD WITH TIME
OVERNIGHT. THEREAFTER CONCERN REGARDING RENEWED CONVECTION POTNL
LATER IN DAY UPSTREAM ACRS NERN IL AROUND MIDDAY AND SHIFTING EWD
THROUGH NRN IN IN AFTN/EVE. CONTD VCTS WITH AT KSBN AS
COVERAGE/LOCATION IN QUESTION...THOUGH INTRODUCE LATE AFTN/EVE
TEMPO PD AT KFWA GIVEN INCRSD SIGNALS PER LATEST NAM.

&&

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

$$

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


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