Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 250902
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
402 AM EST TUE NOV 25 2014

.SYNOPSIS...
ISSUED AT 355 AM EST TUE NOV 25 2014

AN UPPER LEVEL DISTURBANCE WILL BRING SNOW SHOWERS TO THE AREA
TODAY...PARTICULARLY ACROSS FAR NORTHERN INDIANA AND SOUTHERN
LOWER MICHIGAN. SNOWFALL ACCUMULATIONS ARE EXPECTED TO REMAIN
LIGHT. A RIDGE OF HIGH PRESSURE WILL SETTLE INTO THE REGION
TONIGHT ALLOWING FOR CONTINUED DIMINISHING WINDS AND DECREASING
CLOUDS. HIGH TEMPERATURES THIS AFTERNOON WILL RANGE FROM THE UPPER
20S TO MID 30S...WITH LOW TEMPERATURES TONIGHT DROPPING INTO THE
LOWER TO MID 20S.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 355 AM EST TUE NOV 25 2014

POTENTIAL OF SOME MINOR SNOW ACCUMULATIONS TODAY WILL CONTINUE TO BE
THE SHORT TERM FORECAST FOCUS.

NEXT UPPER LEVEL SHORT WAVE ACROSS NORTHWEST ILLINOIS/SOUTHWEST
WISCONSIN EARLY THIS MORNING WILL SWING THROUGH THE SOUTHERN GREAT
LAKES THROUGH EARLY AFTERNOON. DESPITE PRESENCE OF SHEARED UPPER
LEVEL WAVES ACROSS REGION DURING THE OVERNIGHT HOURS...DRY AIR ABOVE
THE INVERSION HAS LIMITED ANY ACCUMULATION JUST TO A TENTH OR TWO
TWO IN SPOTS. NAM BUFFER SOUNDINGS DO SUGGEST A BRIEF PERIOD OF
SLIGHTLY BETTER SATURATION IN DGZ THIS MORNING WITH APPROACH OF THIS
TROUGH HOWEVER. A SECONDARY TIGHT LOW LEVEL THERMAL RIBBON ALSO
APPEARS TO BE ASSOCIATED WITH THIS UPSTREAM SHORT WAVE WHICH MAY
HELP TO INDUCE SOME LOW LEVEL FGEN RESPONSE...PARTICULARLY ACROSS
THE NORTHERN THIRD OF THE FORECAST AREA THIS MORNING. LAKE INDUCED
INSTABILITY STILL APPEARS TO MAXIMIZE IN THE 12Z-15Z TIMEFRAME WITH
REINFORCING LOW LEVEL CAA PUSH...BUT STILL QUITE SHALLOW IN NATURE
WITH LAKE INDUCED EQUILIBRIUM HEIGHTS ONLY TO AROUND 6K FT. WESTERLY
TRAJECTORIES WILL ALSO LIMIT FETCH...SO ANY LAKE ENHANCEMENT APPEARS
TO BE MINIMAL AND MORE PRONOUNCED TO THE NORTH OF THE FORECAST AREA.
WILL CONTINUE WITH LESS THAN AN INCH ACCUMULATIONS ACROSS SOUTHWEST
LOWER MICHIGAN/FAR NORTH CENTRAL INDIANA...WITH MOST OF NORTHERN
HALF OF THE AREA JUST EXPERIENCING SOME OCCASIONAL FLURRIES. A VERY
LOW END CONCERN EXISTS FOR SOME PATCHY LIGHT DRIZZLE FROM MID
MORNING THROUGH EARLY AFTERNOON AS DGZ BEGINS TO DRY OUT WITH
PASSAGE OF THIS SHORT WAVE AND BEFORE STRONGER SYNOPTIC SUBSIDENCE
MOVES IN...BUT WOULD ANTICIPATE THAT ANY PATCHY DRIZZLE OR FREEZING
DRIZZLE WOULD NOT BE HEAVY ENOUGH FOR ANY IMPACTS AND WILL OMIT FROM
ZFP WITH LOW CONFIDENCE IN OCCURRENCE.

LOWERING INVERSION HEIGHTS LATE THIS AFTERNOON/EARLY EVENING WILL
DIMINISH ANY LINGERING LAKE EFFECT SNOW SHOWERS WITH NO ADDITIONAL
ACCUMULATION EXPECTED. MAIN QUESTION FOR TONIGHT WILL CENTER ON
DURATION OF LOW CLOUDS ACROSS THE AREA. STRENGTH OF SUBSIDENCE AND
EASTWARD ADVECTION OF AN AXIS OF DRIER LOW LEVEL AIR FROM THE MID MS
VALLEY MAY BE ENOUGH TO CLEAR THINGS OUT THIS EVENING. STILL SOME
HESITATION TO FULLY BUY INTO THIS GIVEN POSSIBILITY OF TRAPPED LOW
LEVEL MOISTURE BENEATH LOWERING INVERSION...SO HAVE HEDGED SKY GRIDS
TO A BECOMING PARTLY CLOUDY TREND FOR TONIGHT. IF MORE SUBSTANTIAL
CLEARING OCCURS...MINS MAY DROP INTO THE TEENS...BUT FOR THIS CYCLE
WILL STAY WITH INHERITED LOWER TO MID 20S MINS GIVEN ABOVE
UNCERTAINTIES.

&&

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 355 AM EST TUE NOV 25 2014

COLD WITH SEVERAL CHANCES FOR LIGHT SNOW MID-LATE WEEK...WITH MILDER
PACIFIC AIR ADVECTING IN FOR THE WEEKEND...

GOOD AGREEMENT WITHIN LAST SEVERAL MODEL CYCLES IN TRACKING A
COMPACT/DIGGING ALBERTA CLIPPER SOUTHEAST THROUGH THE MID MS/WESTERN
OH VALLEY LATER WED-WED EVE. STRIPE OF ACCUMULATING SNOW
ACCOMPANYING THE LOW-MID LVL FGEN RESPONSE WILL LIKELY PASS SW OF THE
LOCAL AREA RESULTING IN A MAINLY DRY FCST LOCALLY DURING THIS TIME.
SEPARATE ROUND OF WEAK PRESSURE ADVECTION ON THE TROPOPAUSE...AND
LAKE EFFECT ACTIVATION ASSOCIATED WITH RENEWED/VEERED CAA SURGE WILL
BRING INCREASING CHANCES FOR SCT-NUM SNOW SHOWERS ON THANKSGIVING
(MAINLY NORTH OF HWY 30). COULD SEE SOME ACCUMULATIONS/IMPACTS
(1-3"?) IN FAVORED WNW FLOW ZONES AS 700 MB DELTA T`S TANK INTO THE
MID 20S AND INVERSION HEIGHTS INCREASE TO NEAR 10 KFT PER LATEST
FCST SOUNDINGS.

UPPER LEVEL PATTERN WILL SHIFT TO ZONAL FRIDAY INTO THE WEEKEND
SUPPORTING A DECENT MODERATING TREND. THE RESULTING GRADIENT PATTERN
WITH FRONTAL ZONE IN THE VICINITY UNDER PERTURBED WESTERLIES MAKES
THIS A LOWER CONFIDENCE FCST FRIDAY AND BEYOND. MODEL CONSENSUS
CONTINUES TO FAVOR WI INTO MI FOR BETTER WARM ADVECTION SNOW CHANCES
FRIDAY...BUT STILL CONSIDERABLE DIFFERENCES IN GUIDANCE ON WHERE
BETTER FGEN/FORCING WILL ALIGN. HIGHER CONFIDENCE IN A WARMER/MAINLY
DRY SATURDAY AS BAROCLINIC ZONE LIFTS NORTH ALLOWING MILD AIR TO
OVERSPREAD. LOW CHANCES FOR PCPN (MAINLY RAIN) AND LOW CONFIDENCE IN
TEMPS THEREAFTER AS SUBTLE BUCKLE IN GREAT LAKES FLOW FORCES FRONTAL
BOUNDARY BACK SOUTH INTO THE REGION.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1259 AM EST TUE NOV 25 2014

SFC LOW PRESSURE ACROSS SOUTHEAST ONTARIO WILL CONTINUE TO PULL
OFF TO THE EAST TONIGHT AND WEAKEN WHICH WILL ALLOW FOR WINDS TO
CONTINUE TO SLOWLY SUBSIDE. ANOTHER VORT MAX DIGGING ACROSS THE
MID MS RIVER VALLEY WILL TRACK ACROSS THE SOUTHERN GREAT LAKES
THROUGH TUESDAY MORNING ALLOWING FOR A CONTINUATION OF SCATTERED
LIGHT SNOW SHOWERS/FLURRIES. MVFR CIGS IN THE 1-2K FT RANGE ARE
EXPECTED TO PERSIST OVERNIGHT...GRADUALLY IMPROVING TO AOA 2K FT
AT KFWA AFTER 10Z...AND AT KSBN TOWARD MIDDAY. WEST WINDS SHOULD
SETTLE INTO THE 10 TO 15 KNOT RANGE BY MID MORNING TUESDAY.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR LMZ043-046.

&&

$$

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


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