000
FXUS63 KIWX 082029
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
329 PM EST SUN DEC 8 2013

.SYNOPSIS...
ISSUED AT 1045 AM EST SUN DEC 8 2013

A DISTURBANCE WILL CONTINUE TO PROGRESS THROUGH THE REGION THIS
AFTERNOON...BRINGING A WINTRY MIX OF LIGHT SNOW AND FREEZING
FREEZING RAIN AND DRIZZLE THIS AFTERNOON AND TONIGHT. HIGHS TODAY
WILL BE IN THE UPPER 20S. LOWS TONIGHT WILL DIP IN THE MID 20S.
TEMPERATURES WILL REMAIN BELOW NORMAL FOR THE NEXT SEVERAL DAYS.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 328 PM EST SUN DEC 8 2013

FORCED EJECTION OF LOW AMPLITUDE MIDLVL SHORTWAVE INTO KS THIS
AFTERNOON AS EXTREME ARCTIC SURGE DIVES SWD OVR NRN ROCKY PLATEAU
FAVORING LOW LEVEL 900-800MB FGEN RESPONSE SW-W OF CWA. WITH
NOTABLE SFC PRES FALLS ACRS NRN IL AND DVLPG 925MB CIRCULATION
ACRS NRN MO PER WRFARW/NAM/SREF BLEND. FEATURE QUICKLY
DEEPENS/LIFTS NEWD INTO SERN WI BY 06 UTC TONIGHT AND FAR NRN LWR
NRN LWR MI BY 12 UTC DEEPER CAA TO INFILTRATE SWRN/SRN GRTLKS AND
PERSIST THROUGH MONDAY WITH YET ANOTHER REINFORCING ARCTIC SURGE
UPSTREAM. IN ADVANCE OF SYSTEM A BRIEF PERIOD OF ASSERTIVE I285K
UPGLIDE WITH STRONG EASTERLY SYSTEM RELATIVE FLOW AFFORDING INCRSD
LIGHT SNOW COVERAGE. OVERALL SPEED OF SYSTEM WITH RAPID
TRANSLATION TO PARALLEL FLOW TO ISENTROPE SURFACES THROUGH 03-06
UTC TO BRING DCRSD LIFT MECHANISM THEREAFTER. ALTHOUGH STRONG
WINDS WITHIN MOIST 1-4KFT LYR SHOULD PROVIDE IMPETUS FOR LIGHT
HYDROMETEORS INTO OVERNIGHT WITH LIGHT FZDZ BECOMING INCREASINGLY
DOMINANT S-N AS CLOUD TOPS LOWER...COINCIDENT W/LOSS OF ICE
NUCLEATION/INTRODUCTION. EXPECT SUFFICIENT SUSTAINED ICE PRESENT
PER SRN IN OBS/RADAR HGHT RETURNS INTO EVENING HOURS FOR ENTIRE
CWA WITH PRE-FIRST MENTION. OTHERWISE ONLY FAR NWRN-NRN CWA WITH
COLDER AND SLIGHTLY MORE GENEROUS MSTR PROFILE AS WRLY FLOW ACRS
SRN LK MI DVLPS TO ESCAPE LIGHT FZG PRECIP POTNL. ANTICIPATED
THICK STRATUS DECK ACRS CWA FOLLOWED BY SUSTAINED/STRENGTHENING
LLVL CAA THROUGH MONDAY TRANSLATES INTO ONLY ABOUT 3-5F POSITIVE
DIURNAL RESPONSE.

&&

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 328 PM EST SUN DEC 8 2013

ANOMALOUSLY COLD PATTERN TO PERSIST THROUGH MOST OF THIS WEEK AS
SEVERAL FAST MOVING CLIPPER SYSTEMS BRING REINFORCING SHOTS OF
ARCTIC AIR WITH MINIMAL CHANCES FOR WIDESPREAD PRECIP. THE EXCEPTION
OF COURSE BEING LAKE EFFECT...BOTH OF THE PURE AND
SYNOPTICALLY-ENHANCED VARIETIES. FIRST LAKE EFFECT "EVENT" WILL
ACTUALLY BE WINDING DOWN TO START THE PERIOD. WHAT LITTLE ACTIVITY
IS LEFT BY LATE TOMORROW WILL DISSIPATE BY EARLY TUESDAY. POOR
FETCH...COPIOUS DRY AIR ENTRAINMENT...AND PALTRY CONVECTIVE DEPTHS
WILL LIMIT THE RESPONSE TO BEGIN WITH BUT BACKING LOW LEVEL WINDS
AFTER MIDNIGHT WILL BE THE FINAL NAIL IN THE COFFIN. PREFER A VERY
LOW CHANCE POP PRIOR TO 06Z AND DRY AFTERWARD. LITTLE TO NO
ADDITIONAL ACCUMULATION EXPECTED. WILL BE ANOTHER COLD NIGHT THOUGH.
THERMAL PROFILES APPEAR SIMILAR TO LAST NIGHT AND AT LEAST PARTIAL
CLEARING SHOULD ALLOW TEMPS TO FALL INTO THE LOW TO MID TEENS FOR
MOST LOCATIONS DESPITE STEADY GRADIENT WIND.

NEXT SHORTWAVE WILL ARRIVE ON TUESDAY. 850-500MB Q VECTOR
CONVERGENCE WILL PASS NORTH OF OUR AREA AND MOISTURE RETURN IS
VIRTUALLY NONEXISTENT. LAKE INDUCED INSTABILITY AND MOISTURE FLUX
WILL ALSO BE FOCUSED TO OUR NORTH GIVEN PREDOMINATELY WSW FLOW.
WINDS DO VEER A BIT BY THE EVENING BUT ONLY BRIEFLY AS THE NEXT WAVE
WILL BE RIGHT ON ITS HEELS. NOT SURPRISINGLY THEN...FORECAST
SOUNDINGS IN OUR AREA ARE NOT SUPPORTIVE OF ACCUMULATING SNOW AND
WILL MAINTAIN JUST A LOW CHANCE POP IN OUR EXTREME NORTHWEST. MAIN
IMPACT OF THIS SYSTEM WILL BE A TIGHTENING SURFACE PRESSURE
GRADIENT. COUPLED WITH SOME LATE DAY ISENTROPIC DESCENT/INCREASED
MIXING...THIS WILL LEAD TO BREEZY CONDITIONS WITH GUSTS AROUND 30
MPH POSSIBLE. GIVEN TEMPS STUCK IN THE LOW TO MID 20S...WIND CHILL
VALUES MAY STRUGGLE TO GET OUT OF THE SINGLE DIGITS FROM MONDAY
NIGHT THROUGH TUESDAY NIGHT.

SLIGHTLY MORE SUBSTANTIAL WAVE SLATED TO ARRIVED ON WEDNESDAY.
MOISTURE WILL AGAIN BE LIMITED BUT BETTER PUSH OF CVA/HEIGHT FALLS
EXPECTED IN OUR AREA WITH A MORE PRONOUNCED LOW LEVEL
CONVERGENCE/FGEN SIGNATURE. STILL NOT EXPECTING SIGNIFICANT SNOWFALL
BUT THERE WILL LIKELY BE A LARGER AREA OF LIGHT SNOW SHOWERS WITH
ACCUMULATIONS AROUND AN INCH POSSIBLE IN OUR NORTHWEST. THIS WAVE
MARKS THE LEADING EDGE OF AN EVEN COLDER AIRMASS AND WEDNESDAY
NIGHT/THURSDAY WILL LIKELY BE OUR COLDEST PERIOD THUS FAR. 925MB
TEMPS DROP TO ALMOST -15C WEDNESDAY NIGHT BEFORE RECOVERING SLIGHTLY
THURSDAY AFTERNOON. OVERNIGHT LOWS WILL DEPEND ON DEGREE OF
CLEARING/DECOUPLING BUT SINGLE DIGITS APPEAR LIKELY AND A FEW VALUES
NEAR 0F NOT OUT OF THE QUESTION. LATE DAY RECOVERY POSSIBLE ON
THURSDAY GIVEN BACKING LOW LEVEL WINDS BUT IT WILL STILL BE A
STRUGGLE FOR TEMPS TO MAKE IT OUT OF THE TEENS. WIND CHILLS ON
THURSDAY LOOK TO BE IN THE SINGLE DIGITS ONCE AGAIN. MODERATING
TEMPS POSSIBLE BY THE END OF THE WEEK AS WEST COAST RIDGE AT LEAST
PARTIALLY BREAKS DOWN. MODELS DISAGREE ON TIMING THOUGH AND WILL
THEREFORE STICK CLOSE TO CONSENSUS BLENDS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1256 PM EST SUN DEC 8 2013

EFFECTIVE ISENTROPIC LIFT PRODUCING SOME LIGHT SN ACRS NRN
IN...THOUGH MET CONDS TO HOLD UNTIL AT LEAST THIS EVENING.
THEREAFTER...TOP/DOWN SATURATION AND COLUMN COOLING AMID A WELL
PERTURBED 1-4KFT LYR TO LEAD TO LWRD CIGS IN WIDESPREAD STRATUS.
WITH TIME ICE NUCLEATION BECOMES AN INCREASED CONCERN AS CLOUD
TOPS WARM...ESPCLY INVOF KFWA AND LEADING TO LIGHT FZDZ QUITE
PSBL. COLDER PROFILE AT KSBN SHOULD AFFORD A BRIEF MIX OVERNIGHT.
BY DAYBREAK ANTICIPATE WIDESPREAD IFR-FUEL ALT CIGS ACRS
REGN...LOWEST AT KFWA IN CLOSER PROXIMITY TO MSTR TAP OVERNIGHT
AND LATER FROPA MON AM.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY FROM 4 AM MONDAY TO 4 AM EST TUESDAY FOR
     LMZ043-046.

&&

$$

SYNOPSIS...KG
SHORT TERM...MURPHY
LONG TERM...AGD
AVIATION...MURPHY


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