Area Forecast Discussion
Issued by NWS Northern Indiana

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085
FXUS63 KIWX 141653
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1153 AM EST SUN FEB 14 2016

.SYNOPSIS...
ISSUED AT 1147 AM EST SUN FEB 14 2016

A PERIOD OF LIGHT ACCUMULATING SNOW IS EXPECTED THIS AFTERNOON INTO
EARLY MONDAY AS AN UPPER LEVEL SYSTEM MOVES THROUGH. SNOWFALL
TOTALS WILL GENERALLY RANGE BETWEEN 1 AND 3 INCHES. HIGHS TODAY
WILL BE AROUND 20 DEGREES. MILDER TEMPERATURES AND SEVERAL
CHANCES FOR LIGHT SNOW CAN BE EXPECTED FOR THE EARLY TO MIDDLE
PORTION OF THE UPCOMING WEEK. HIGHS WILL GENERALLY BE IN THE
30S...WITH LOWS IN THE 20S.

&&

.UPDATE...
ISSUED AT 1147 AM EST SUN FEB 14 2016

VORT MAX OVER SERN IA EXPECTED TO SHEAR OUT AS IT MOVES EAST
ACROSS IL/IN THIS AFTN/EVE. COMBINATION OF THIS WEAKENING TREND
AND DRY AIR IN PLACE ACROSS OUR AREA EXPECTED TO RESULT IN A
DIMINISHING TREND IN SNOWFALL RATES AS AREA OF SNOW CURRENTLY OVER
IL/IA MOVES ACROSS OUR CWA THIS AFTN/EVE. GOING FCST OF 1-3"
SNOWFALL IN OUR AREA FROM THIS SYSTEM STILL SEEMS TO BE TRACK AND
NO SGFNT CHANGES MADE ON LATE MORNING ZFP UPDATE.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 339 AM EST SUN FEB 14 2016

LIGHT SNOW EVENT ON TARGET TO OVERSPREAD FROM SW TO NE LATER THIS
AFTN/EVE AS VIGOROUS SHORTWAVE OVER EASTERN SD DAMPENS
EASTWARD THROUGH THE LOWER LAKES OVER RETREATING ARCTIC DOME.
CORRIDOR OF MID LEVEL WAA/~25 KNOTS OF CROSS ISOBARIC FLOW ON
285/290K SFCS WILL PROVIDE THE BROAD FORCING/MOISTURE TRANSPORT (2
G/KG) DOWNSTREAM OF THIS FEATURE. MODEL GUIDANCE OVERALL IN GOOD
AGREEMENT WITH QPF (0.05-0.15)...HEAVIEST ACROSS SOUTHWEST ZONES
(MONTICELLO /LOGANSPORT/WINAMAC/ETC INDIANA) WHERE A MORE FOCUSED
FGEN RESPONSE MAY ENHANCE SNOWFALL INTENSITY TO START THIS AFTN.
SNOW RATIOS COULD BE ABOVE CLIMO GIVEN RELATIVELY DEEP
ISOTHERMAL LAYER IN LOWER PORTION OF DGZ. HOWEVER...OMEGA WITHIN
THIS LAYER DOESN`T LOOK ALL THAT IMPRESSIVE (BROAD) GIVEN DAMPENING
NATURE TO UPPER WAVE AS IT ENCOUNTERS LEFTOVER CONFLUENCE ON
BACKSIDE OF EXITING UPPER TROUGH. AS A RESULT OPTED FOR SNOW TO
LIQUID RATIOS AROUND 15:1. THIS BRINGS SNOW TOTALS INTO THE 1-3 INCH
RANGE WEST TO 0.5-2 INCHES ACROSS NE IN/LOWER MI/NW OH.
ACCUMS/IMPACTS REMAIN COVERED IN THE HWO.

LOW LEVEL WAA WILL PERSIST INTO THE OVERNIGHT WITH SFC AMBIENT TEMPS
SLOWLY WARMING THROUGH THE LOW-MID 20S. LOSS OF DEEPER
MOISTURE/LARGE SCALE SUPPORT WILL RESULT IN DECREASING
COVERAGE/INTENSITY OF SNOW DURING THIS TIME...WITH FREEZING DRIZZLE
NOT OUT OF THE QUESTION TOWARD DAYBREAK INTO OUR INDIANA COUNTIES
GIVEN LOSS OF ICE CONCERNS. HOWEVER...PROBABILITY OF FZDZ REMAINS
TOO LOW FOR A MENTION IN THE GRIDS/HWO ATTM.

&&

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 339 AM EST SUN FEB 14 2016

STRONG NORTH PACIFIC JET TO SEND SEVERAL SMALL SCALE SHORT WAVES
ACROSS THE CONUS THIS PERIOD. MODELS HAVING USUAL PROBLEMS IN THE
LONG TERM TRYING TO RESOLVE FAST JET DYNAMICS AND NUMEROUS SHORT
WAVE INTERACTIONS WITH STRONG FLOW ALOFT.

WATER VAPOR AND UPPER AIR ANALYSIS SHOWS 150+ KT JET OFF THE PACIFIC
NORTHWEST COAST AND BEGINNING TO MOVE INLAND THIS MORNING. 00Z UPPER
AIR PLOT AND GOES SATELLITE DERIVED WINDS INDICATE MODELS MAY BE A
BIT OVERDONE WITH UPPER LEVEL WINDS. SHOULD SEE A BETTER SAMPLING OF
WINDS TODAY AS JET MOVES FURTHER INLAND. THIS MAY HELP RESOLVE A LOT
OF DIFFERENCES AMONGST THE MODELS IN THE ESPECIALLY FOR
THE SHORT WAVE TUESDAY.

A FEW CONCERNS WITH PCPN TYPE TO BEGIN THE PERIOD MONDAY MORNING.
DEEPER MOISTURE IS EXITING THE AREA WITH DGZ DRYING OUT AND SFC
TEMPS STILL BELOW FREEZING THROUGH MID MORNING. SOUNDINGS SHOW SOME
WEAK LIFT AND LACK OF ICE NUCLEI SO IF ANY LIGHT PCPN FALLS THERE IS
A SMALL CHANCE FOR SOME FREEZING DRIZZLE. SKILL AND CONFIDENCE LOW
IN THIS TIME PERIOD SO HAVE STAYED WITH LIGHT SNOW SHOWERS AS PCPN
TYPE BUT THIS WILL NEED TO BE WATCHED. FOCUS THEN SHIFTS TO SYSTEM
FOR TUESDAY. MODELS SHOWING A COUPLE WEAK SHORT WAVES DROPPING INTO
THE MIDWEST ON NOSE OF STRONG BUT WEAKENING NORTH PACIFIC JET. MODEL
SOLUTIONS VARY DRASTICALLY WITH THE 00Z NAM BEING STRONGEST AND
FURTHEST NORTH WITH SFC LOW TRACKING OVER NORTH CENTRAL INDIANA. GEM
IS FURTHEST MODEL SOUTH WITH LOW TRACKING THROUGH MISSOURI. GFS AND
ECMWF FALL IN BETWEEN AND GENERALLY PREFERRED AT THIS TIME WITH BEST
FIT TO CONTINUITY GIVEN MODEL SPREAD AND UNCERTAINTY. FEW CHANGES
MADE TO GOING FORECAST WITH HIGHEST POPS STILL IN HIGH CHANCE RANGE
ACROSS THE SOUTH. MODELS ALSO WARMER IN THE LOWER LEVELS AND STILL
TRENDING TOWARD POSSIBILITY OF A RAIN SNOW MIX TUESDAY AFTERNOON AS
SFC TEMPS WARM INTO THE MID 30S.

BRIEF COOL DOWN FOR WEDNESDAY FOLLOWING COLD FRONT BUT REBOUND FOR
END OF WEEK STILL ON TRACK WITH HIGHS INTO THE 40S AND 50S. GRADIENT
TIGHTENS FRIDAY WITH WARM AIR ADVECTION AND SFC LOW MOVING THROUGH
THE UPPER MIDWEST. THIS SHOULD BRING BREEZY CONDITIONS ALONG WITH A
CHANCE FOR LIGHT RAIN.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1147 AM EST SUN FEB 14 2016

AREA OF SNOW OVER IA/IL ASSOCIATED WITH  MID LEVEL VORT MAX AND
LOW LEVEL WAA WILL MOVE EAST AND IMPACT THE TERMINALS THIS
AFTN/EVE. SOME SHEARING OUT OF THE SYSTEM EXPECTED AS IT MOVES
EAST OVER THE NEXT 24HRS AND INTO VERY DRY AIRMASS, SO STUCK WITH
CONDITIONS LOWERING TO IFR PER PREVIOUS TAFS AS OPPOSED TO LIFR
WHICH CURRENTLY IS OCCURRING UPSTREAM IN IL/IA. WINDS WILL VEER
FROM SE TO SOUTH AS A WK SFC TROF REFLECTION LIFTS NORTH ACROSS
INDIANA TONIGHT. THIS WEAK SOUTHERLY FLOW WILL LIKELY CAUSE LOW
CIGS MOVG INTO THE AREA WITH THE SNOW THIS AFTN TO PERSIST
THROUGH THE END OF THE TAF PERIOD.

&&

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

$$

UPDATE...JT
SYNOPSIS...STEINWEDEL/JT
SHORT TERM...STEINWEDEL
LONG TERM...LASHLEY
AVIATION...JT


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