Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 180800
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
400 AM EDT FRI APR 18 2014

.SYNOPSIS...
ISSUED AT 400 AM EDT FRI APR 18 2014

A WEAK COLD FRONT WILL PASS THROUGH THE AREA THIS MORNING WITH A
SLIGHT CHANCE OF SHOWERS. HIGH PRESSURE AND DRY CONDITIONS WILL
THEN RETURN BY THE AFTERNOON. THIS HIGH PRESSURE SYSTEM WILL BRING
MOSTLY CLEAR SKIES FOR MUCH OF THE WEEKEND.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM EDT FRI APR 18 2014

WEAK COLD FRONT CURRENTLY CROSSING THE AREA WITH VERY LITTLE
FANFARE. IN FACT...NOT MUCH EVIDENCE OF A SURFACE FRONT AT ALL IN
LATEST TEMP/PRESSURE/WIND REPORTS. BETTER EVIDENCE OF FRONTAL
FEATURE RESIDES AROUND 850MB WITH INCREASED BAROCLINICITY AND
CONVERGENCE SEEN THERE. IT IS WITHIN THIS ELEVATED REGION OF WEAK
BUT SUBTLY INCREASING FRONTOGENESIS THAT OUR CHANCES OF PRECIP
REMAIN. REGIONAL REFLECTIVITIES HAVE GRADUALLY INCREASED IN THE PAST
FEW HOURS AS EXPECTED. THIS IS IN RESPONSE TO SHORTWAVE TROUGH OVER
THE UPPER MIDWEST FINALLY APPROACHING THE REGION. UPPER LEVEL FLOW
CONFIGURATION ASSOCIATED WITH THIS WAVE AND THE TROUGH MOVING
THROUGH THE GULF COAST STATES HAS ALSO LEFT THE SOUTHERN GREAT LAKES
IN A FAVORABLE POSITION WITH RESPECT TO CORRESPONDING JET STREAKS.
ASSOCIATED UPTICK IN LOW LEVEL FGEN AND DIVERGENCE ALOFT HAS ALLOWED
SHOWERS TO INCREASE BUT DRY AIR BELOW 6 KFT...AS SEEN ON 00Z KILX
SOUNDING...IS STILL TAKING ITS TOLL AMID ONLY MODEST FORCING. ONLY
TRACE REPORTS SEEN SO FAR. MORE IMPORTANT ASPECT TO NOTE FOR TODAY`S
FORECAST IS THE TRANSIENT NATURE OF AFOREMENTIONED JET STREAKS.
POSITIONING FAVORABLE TO OUR CWA WILL ONLY LAST A SHORT TIME THIS
MORNING WITH LEFT ENTRANCE FRONTOLYSIS NOTED BY MIDDAY. THIS
SUGGESTS A GRADUAL DECREASE IN ALREADY HANDICAPPED PRECIPITATION
EFFICIENCY THROUGH THE REST OF THE MORNING. LATEST HI-RES/RAPID
UPDATE MODELS REFLECT THIS EXPECTATION WELL WITH LITTLE TO NO QPF
AFTER ROUGHLY 13Z. WILL THEREFORE PARE BACK LATE MORNING POPS AND
REMOVE ANY MENTION POST 18Z. THIS SHOULD ALLOW FOR FAIRLY PLEASANT
AFTERNOON. WEAK CAA WILL SEND 925MB TEMPS TO AROUND 5C IN THE
NORTHWEST BUT STILL HOLDING ABOVE 10C IN THE SOUTHEAST. MIXING
DEPTHS APPEAR MUCH GREATER IN THE SOUTHEAST AS WELL BASED ON LATEST
NAM AND GFS BUFR SOUNDINGS. THEREFORE EXPECT ANOTHER DAY OF MID TO
UPPER 60S IN OUR SOUTHEAST BUT ONLY UPPER 50S AROUND KSBN. CLOUDS
WILL ALSO DECREASE THROUGH THE DAY AND CLEAR SKIES WITH LIGHT
NORTHEAST WINDS COULD ALLOW TEMPS TO DROP INTO THE LOW TO MID 30S
FOR MANY AREAS TONIGHT. LOWERED INHERITED MINS JUST A TOUCH TO BE
MORE IN LINE WITH CONSENSUS OF LATEST MOS AND RAW GUIDANCE BUT
OVERALL CHANGES MINIMAL.

&&

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 400 AM EDT FRI APR 18 2014

ANOTHER MILD WEEKEND IN STORE FOR THE AREA WITH PCPN LIKELY
HOLDING OFF UNTIL MONDAY. HIGH PRESSURE WILL DRIFT ACROSS THE
LAKES THIS WEEKEND. SATURDAY WILL SEE SURFACE WINDS FROM THE EAST
TO SOUTHEAST. LOW LEVEL FLOW OFF THE EASTERN LAKES WILL LIKELY
KEEP FAR NORTHEAST CWA IN A COOL MARINE LAYER WITH TEMPS REMAINING
IN THE 50S. FULL SUN EXPECTED DURING THE DAY AND NAM12 SOUNDINGS
INDICATE MIXING TO ABOUT 900MB WHICH YIELDS TEMPS IN THE LOWER 60S
CENTRAL AND MID 60S SOUTHWEST. DRY ATMOSPHERE YESTERDAY ALLOWED
FOR A LARGE DIURNAL SWING WITH SUPERADIABATIC LAPSE RATES NEAR THE
SURFACE AND THINK THIS WILL BE POSSIBLE SATURDAY OUTSIDE OF
AFOREMENTIONED LAKE INFLUENCE.

HIGH PRESSURE WILL SLIDE EAST TO NEW ENGLAND ON SUNDAY ALLOWING FOR
WARMER RETURN FLOW AND DEEPER MIXING HEIGHTS TO 850MB. MIXING TOOLS
SUGGEST TEMPS COULD EASILY APPROACH MID 70S IF THESE PROFILES
VERIFY. HAVE CONTINUED TREND OF BUMPING TEMPS UP AS CONFIDENCE
INCREASES. MAY SEE SOME AFTERNOON CIRRUS DRIFT OVER AHEAD OF NEXT
SYSTEM WHICH MAY IMPACT TEMPS A FEW DEGREES.

NEXT SHORT WAVE MOVES THROUGH MONDAY AND MONDAY EVENING. DEEP
MOISTURE IS LACKING BUT A LITTLE BETTER THAN CURRENT SYSTEM WHICH IS
STRUGGLING TO PRODUCE MEASURABLE PCPN. GULF REMAINS CUT OFF BUT
MODELS ARE A BIT STRONGER WITH DYNAMICS. GFS PLACES RIGHT ENTRANCE
REGION OF MID LEVEL JET OVER THE GREAT LAKES WHICH WOULD AID LIFT.
ECMWF NOT AS STRONG WITH THIS JET. KEPT THE ALLBLEND POPS IN THE MID
CHANCE RANGE GIVEN THESE FACTORS.

MID WEEK LOOKING COOLER IN WAKE OF THIS SHORT WAVE AND ASSOCIATED
COLD FRONT. 00Z ECMWF CONTINUES TO TREND COOLER WITH 850MB TEMPS
DROPPING TO -5C WEDNESDAY MORNING. MEX MOS HAS ALSO TRENDED COOLER
WITH LOWS WEDNESDAY MORNING IN THE UPPER 30S...ABOUT 6 TO 8 DEGREES
COOLER THAN 17/00Z RUN. HAVE LOWERED TEMPS WEDNESDAY SEVERAL DEGREES
FROM ALLBLEND GIVEN THESE LATEST MODEL SOLUTIONS.

ANOTHER HIGH WILL SLIDE THROUGH THE GREAT LAKES WEDNESDAY INTO
THURSDAY. RETURN FLOW ONCE AGAIN DEVELOPS THURSDAY AS STRONG LOW
PRESSURE STILL EXPECTED TO ORGANIZE IN PLAINS. THIS WILL HELP
INCREASE LOW LEVEL JET AND ALLOW WARMER AIR TO SURGE NORTH. SHOULD
SEE TEMPS REBOUND BACK INTO 60S AND LOWER 70S ON THURSDAY WITH A
CHANCE FOR SHOWERS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 128 AM EDT FRI APR 18 2014

WEAK ELEVATED COLD FRONT IS CURRENTLY CROSSING THE AREA WITH A FEW
LIGHT RAIN SHOWERS BEING PRODUCED ACROSS NORTHWEST INDIANA. VERY
DRY LOW LEVELS AS SEEN ON 00Z KILX SOUNDING...AND A LACK OF ANY
SUBSTANTIAL SYNOPTIC FORCING ALOFT...ARE EXPECTED TO KEEP CONDITIONS
VFR THOUGH. BRIEF PERIOD OF MVFR MAY BE POSSIBLE AT KSBN BUT THIS
STILL APPEARS UNLIKELY. HIGH PRESSURE WILL GRADUALLY BUILD INTO
THE REGION LATER TODAY WITH JUST SOME LOW END VFR CU TO CONTEND
WITH.

&&

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

$$

SYNOPSIS...AGD
SHORT TERM...AGD
LONG TERM...LASHLEY
AVIATION...AGD


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