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FXUS63 KIWX 211132
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
632 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 THROUGH SATURDAY MORNING) 
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 AFTERNOON 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 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 630 AM EST FRI NOV 21 2014

VFR LAKE EFFECT LOW CLOUDS WILL DISSIPATE THIS MORNING AS LOW LEVEL 
FLOW BACKS MORE SOUTHWESTERLY. VFR CONDITIONS TO THEN PERSIST 
THROUGH THE REMAINDER OF THE DAY AS SOUTHERLY FLOW BECOMES 
ESTABLISHED DUE TO LOW LEVEL ANTICYCLONE SHIFTING SOUTHEAST ACROSS 
THE OHIO VALLEY. VERY STRONG LOW LEVEL MOISTURE TRANSPORT TO LIFT 
INTO THE REGION TONIGHT IN ADVANCE OF A WAVE KICKING OUT OF THE 
ROCKIES. A BRIEF WINDOW APPEARS TO BE SETTING UP FOR FREEZING RAIN 
POTENTIAL AS WARM AIR ALOFT OVERRIDES SHALLOW COLD AIR. THE TIME 
PERIOD OF GREATEST THREAT OF FREEZING RAIN APPEARS TO BE IN THE 
08Z-13Z TIMEFRAME EARLY SATURDAY MORNING. HAVE TRENDED TAFS TO MVFR 
TERMINALS WITH CIGS IN THE 2000-3000 FT RANGE...ALTHOUGH CIGS BELOW 
2K FT ARE POSSIBLE TOWARD THE END OF THE FORECAST VALID PERIOD AND 
EXTENDING THROUGH SATURDAY MORNING.

&&

.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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