Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 210908
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
408 AM EST FRI NOV 21 2014

.SYNOPSIS...
ISSUED AT 358 AM EST FRI NOV 21 2014

A RIDGE OF HIGH PRESSURE ACROSS THE MID MISSISSIPPI VALLEY WILL
TRACK INTO THE OHIO VALLEY TODAY. AS THIS OCCURS WINDS WILL BECOME
SOUTHERLY...AND ANY LINGERING LIGHT LAKE EFFECT SNOW SHOWERS AND
FLURRIES WILL COME TO AN END. WARMER AIR MOVING INTO THE REGION
TONIGHT WILL COMBINE WITH AN UPPER LEVEL DISTURBANCE FROM THE
ROCKIES TO PRODUCE A GOOD CHANCE OF LIGHT FREEZING RAIN LATE
TONIGHT INTO EARLY SATURDAY MORNING...BEFORE CHANGING TO ALL RAIN.
HIGH TEMPERATURES TODAY WILL RANGE FROM THE LOWER 30S ACROSS
NORTHEAST ILLINOIS...TO THE MID 20S ACROSS SOUTHEAST LOWER
MICHIGAN INTO NORTHERN OHIO. LOW TEMPERATURES TONIGHT WILL RANGE
FROM THE MID 20S ACROSS NORTHEAST ILLINOIS...TO THE UPPER TEENS
ACROSS NORTHWEST OHIO AND SOUTHEAST LOWER MICHIGAN.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 358 AM EST FRI NOV 21 2014

QUIET CONDITIONS TO BEGIN THE SHORT TERM FOR TODAY WILL BE FOLLOWED
BY POTENTIAL OF FREEZING RAIN LATE TONIGHT INTO THE EARLY MORNING
HOURS OF SATURDAY.

LAKE EFFECT CLOUDINESS PERSISTS ACROSS EXTREME NORTHERN INDIANA AND
SOUTHERN LOWER MICHIGAN WITH SCATTERED SNOW SHOWERS ONLY LIMITING
VSBYS IN THE 3-6 MILE RANGE. NOT EXPECTING ANY ACCUMULATION THIS
MORNING ALTHOUGH A STRAY TENTH OF AN INCH OR SO WILL BE POSSIBLE
ACROSS SOUTHERN LOWER MICHIGAN THROUGH 12Z. SFC ANTICYCLONE
DROPPING SOUTHEASTWARD OUT OF CENTRAL ILLINOIS WILL ALLOW FOR
BACKING LOW WINDS AND REDUCED FETCH. LAKE INDUCED INSTABILITY ALSO
TO STEADILY DECREASE OVER THE NEXT SEVERAL HOURS AS INVERSION
HEIGHTS CONTINUE TO CRASH UNDER THE INFLUENCE OF RISING MID LEVEL
HEIGHTS AND LARGER SCALE SYNOPTIC SUBSIDENCE. MOSTLY SUNNY
CONDITIONS SHOULD SHAPE UP ACROSS THE AREA FOR THE REMAINDER OF
THE DAY WITH SOUTHERLY LOW LEVEL WINDS DEVELOPING. ARCTIC DOME
WILL BE SOMEWHAT STUBBORN TO SCOUR OUT...AND HAVE NOT MADE MUCH
CHANGE TO PREVIOUS MAX TEMPS FROM AROUND 30 WEST...TO THE MID 20S
EAST.

ATTENTION FOR TONIGHT WILL SHIFT TO UPPER LEVEL TROUGH CURRENTLY
PROGRESSING THROUGH THE ROCKIES EARLY THIS MORNING. VERY STRONG LOW
LEVEL MOISTURE ADVECTION WILL DEVELOP AS VERY DRY AIR MASS SUBJECT
TO HISTORY OF SUBSIDENCE ACROSS THE GREAT LAKES SHIFTS ACROSS THE
MID ATLANTIC STATES. LOW LEVEL MOISTURE TONGUE WILL RAPIDLY LIFT
INTO THE MID MS RVR VALLEY THIS EVENING IN ADVANCE OF APPROACHING
WAVE...AND THEN WEST TO EAST ACROSS THE LOCAL AREA IN THE 06Z-18Z
TIMEFRAME. MID/UPPER FORCING DOES NOT APPEAR TO BE OVERLY IMPRESSIVE
GIVEN BROAD...LOW AMPLITUDE NATURE TO THE ROCKIES UPPER TROUGH BUT
STRONG LOW LEVEL MOISTURE CONVERGENCE/ISENTROPIC LIFT SHOULD SUPPORT
AT LEAST LIGHT PRECIP SPREADING INTO WESTERN PORTIONS OF THE CWA
TOWARD THE 06Z TIMEFRAME. MAIN CONCERN AT THIS TIME IS POTENTIAL
OF SHALLOW SUB FREEZING LAYER TO REMAIN IN PLACE WITH WARM LAYER
ALOFT BECOMING MORE PRONOUNCED AFTER 06Z. A BRIEF PERIOD OF LIGHT
FREEZING RAIN APPEARS TO BE A GOOD POSSIBILITY ALTHOUGH INITIALLY
THE VERY DRY NATURE TO THE LOW LEVEL AIR MASS OFFERS SOME LOWER
CONFIDENCE REGARDING ONSET TIME AND PRECIP AMOUNTS. GIVEN STRONG
MOISTURE TRANSPORT...ISENTROPIC UPGLIDE...AND AT LEAST WEAK
MID/UPPER FORCING HAVE FOLLOWED GUIDANCE TRENDS TO HIGHER POPS FOR
THE LATE TONIGHT/SATURDAY MORNING PERIOD. PERIOD OF GREATEST
FREEZING RAIN POTENTIAL APPEARS TO BE IN THE 09Z-15Z TIMEFRAME
FROM WEST TO EAST ACROSS THE AREA. SOME LIGHT ICE ACCUMULATION IS
POSSIBLE BUT WITH AFOREMENTIONED LOWER CONFIDENCE IN
TIMING/AMOUNTS AND BEING A LATE 2ND PERIOD POTENTIAL EVENT...WILL
LET DAY SHIFT ASSESS NEED FOR HEADLINES FURTHER. PLUME OF
RELATIVELY STEEP 700-500 HPA LAPSE SHOULD ADVECT ACROSS ESPECIALLY
NORTHERN HALF OF THE AREA OVERNIGHT. SO WHILE PRECIP AMOUNTS
SHOULD BE QUITE LIGHT IN WEAKLY FORCED ENVIRONMENT (GENERALLY
LESS THAN TENTH OF AN INCH)...MAY NEED TO KEEP AN EYE ON ANY
WEAKER CONVECTIVE RESPONSE LATE TONIGHT/EARLY SATURDAY FOR ANY
LOCALIZED HIGHER PRECIP AMOUNTS.

PRECIP TO CHANGE OVER TO RAIN SATURDAY MORNING AS WARM/MOISTURE
ADVECTION OVERWHELMS PROFILES FROM WEST TO EAST...WITH EVEN FAR
EASTERN LOCATIONS TO LIQUID PRECIP TYPE BY 14 OR 15Z.

&&

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 358 AM EST FRI NOV 21 2014

WET/WARMER THIS WEEKEND/MONDAY WITH A RETURN TO UNSEASONABLY COLD WX
THEREAFTER....

ONGOING ISENTROPIC ASCENT/MOIST ADVECTION ASSOCIATED WITH WEAK
SHORTWAVE ENERGY AND STRENGTHENING MID/UPPER JET WORKING EAST
THROUGH THE GREAT LAKES IN ZONAL FLOW MAY KEEP AREAS OF LIGHT
RAIN/DRIZZLE AROUND INTO SATURDAY AFTN/NIGHT AS SFC WARMS WARM ABOVE
FREEZING. MUCH BETTER CHANCES FOR MORE WIDESPREAD/HEAVIER RAINFALL
ARRIVES SUNDAY AFTN/NIGHT AS SRN STREAM PV ANOMALY (NOW OVER SRN CA)
LIFTS NNE THROUGH THE REGION. EXPECTED NEGATIVE TILT TO WAVE,
PHASING/STRENGTHENING OF UPPER JET ROUNDING BASE OF AN AMPLIFYING
PLAINS LONGWAVE TROUGH, AND GOOD FEED OF MOISTURE/CONVERGENCE WILL
SUPPORT CYCLOGENESIS WITH MODELS AGREEING ON SFC REFLECTION TRACK
NNE THROUGH THE MID MS VALLEY/WESTERN LAKES. AT LEAST THE WESTERLY
TRACK OF SYSTEM WILL ALLOW MUCH WARMER AIR TO OVERSPREAD THE REGION
DURING THIS TIME.

THIS WARMUP WILL BE SHORTLIVED HOWEVER AS THE NEXT DEEP LAYERED
TROUGH CONSOLIDATES INTO THE EASTERN US BRINGING ANOTHER SHOT OF
UNSEASONABLY COLD AIR TO THE LOCAL AREA MONDAY NIGHT AND BEYOND.
TRAILING COLD FRONT THAT WILL USHER IN THIS NEXT COLD BLAST
(ALTHOUGH NOT AS EXTREME AS THIS PAST WEEK) WILL TRANSLATE THROUGH
ON MONDAY WITH FALLING TEMPS EXPECTED LATE MORNING-AFTN. FRONTAL
WAVE/MID LVL FGEN RESPONSE CONTINUES TO SHOW UP IN BULK OF GUIDANCE
HINTING AT THE POTENTIAL FOR ADDITIONAL PCPN (MAINLY RAIN) TO
BLOSSOM/EXPAND NE INTO THE AREA MONDAY. OTHERWISE...CAA/CYCLONIC
FLOW SCT FLURRIES/SNOW SHOWERS CAN EXPECTED WITHIN TROUGH AXIS LATER
MONDAY NIGHT INTO TUESDAY WITH SOME LAKE ENHANCEMENT/ACCUMS POSSIBLE
ACROSS LOWER MI/FAR NRN IN.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1241 AM EST FRI NOV 21 2014

STRONG SYNOPTIC SCALE SUBSIDENCE AND LOWERING INVERSION HEIGHTS
OVERNIGHT WILL GRADUALLY ALLOW LINGERING SCATTERED LIGHT LAKE
EFFECT SNOW SHOWERS AND FLURRIES TO COME TO AN END. MUCH OF THESE
LINGERING SNOW SHOWERS SHOULD REMAIN NORTH OF KSBN WITH JUST LAKE
EFFECT LOW CLOUD CIGS OF 4-5K FT EXPECTED FOR THE NEXT SEVERAL
HOURS. SFC ANTICYCLONE FROM THE MID/UPPER MS RIVER VALLEY WILL
DROP SOUTHEAST INTO THE OHIO VALLEY LATER THIS MORNING ALLOWING
SOUTHERLY WINDS TO RETURN. VFR CONDITIONS ARE EXPECTED TO PERSIST
THROUGH THE PERIOD. JUST AFTER THIS FORECAST VALID PERIOD...WILL
NEED TO ADDRESS -FZRA POTENTIAL IN THE 09Z-15Z TIMEFRAME DUE TO
STRONG LOW LEVEL WAA AND SHALLOW COLD AIR.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 10 AM EST THIS MORNING FOR LMZ043-046.

&&

$$

SYNOPSIS...MARSILI
SHORT TERM...MARSILI
LONG TERM...STEINWEDEL
AVIATION...MARSILI


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