Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 080440
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1142 PM EST SUN FEB 7 2016

.UPDATE...
AVIATION SECTION HAS BEEN UPDATED BELOW

&&

.SYNOPSIS...
ISSUED AT 319 PM EST SUN FEB 7 2016

THE ARRIVAL OF A STRONG UPPER LOW ON MONDAY WILL BRING AN ABRUPT
RETURN TO WINTER FOR THE REGION AS SCATTERED SNOW SHOWERS AND MUCH
COLDER TEMPERATURES IMPACT CENTRAL INDIANA THROUGH MIDWEEK. LARGE
HIGH PRESSURE WILL BRING MAINLY DRY WEATHER FOR THE SECOND HALF OF
THE WEEK AND INTO NEXT WEEKEND...BUT TEMPERATURES WILL REMAIN
COLDER THAN NORMAL.

&&

.NEAR TERM /REST OF TONIGHT/...
ISSUED AT 954 PM EST SUN FEB 7 2016

THE AIRMASS CONTINUES TO BE SOMEWHAT DRY SO EVEN WITH THE PASSAGE OF
A SURFACE TROUGH POOR MOISTURE RETURN WITHIN THE BOUNDARY LAYER IS
LIMITING RAIN CHANCES ACROSS THE AREA. WILL BRING IN SLIGHT CHANCES
FOR SHOWERS OVER PARTS OF THE AREA OVER THE NEXT SEVERAL HOURS AND
WOULDN/T BE SURPRISED IF MOST SPOTS SEE NOTHING OR ONLY SPRINKLES.

WEAK COLD ADVECTION WILL COMMENCE WITH THE PASSAGE OF THE TROUGH AS
TEMPS FALL INTO THE 30S. A FEW SNOW SHOWERS NORTHWEST OR A RAIN/SNOW
MIX SOUTH MAY DEVELOP TOWARDS 12Z AS THE INITIAL SURGE OF FORCING
ALOFT ASSOCIATED WITH THE APPROACHING UPPER LOW ARRIVES. HOWEVER ANY
SUBSTANTIAL SNOW SHOWER COVERAGE WILL HOLD OFF UNTIL AFTER DAYBREAK.

BUMPED LOWS UP A COUPLE DEGREES INTO THE LOWER 30S WITH LOCAL
TEMPERATURES FALLING SLOWER THAN FORECAST UNDER THE CIRRUS AND
UPSTREAM TEMPERATURES NOT MUCH COLDER.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
ISSUED AT 322 PM EST SUN FEB 7 2016

A PROLONGED PERIOD OF HIGH IMPACT SNOW SHOWERS AND SQUALLS WILL
PERSIST THROUGHOUT MUCH OF THE SHORT TERM...CAUSING TRAVEL
DIFFICULTIES WITH SNOW...WIND AND PROGRESSIVELY COLDER TEMPERATURES.
THE FORECAST CHALLENGES WILL FOCUS ON THE DIFFERENT PARAMETERS
SLATED TO CONTRIBUTE TO THIS EXTENDED PERIOD OF SNOW SHOWERS...AND
THE IMPACTS THEY WILL CREATE NOT ONLY WITH CONDITIONS BUT AMOUNTS.

THE DEEPENING UPPER LOW WITH AN ATTENDANT SURFACE WAVE WILL SPIN
SLOWLY OVER THE LOWER GREAT LAKES THROUGH THE PERIOD AS A DEEP UPPER
TROUGH IS CARVED OUT ACROSS THE EASTERN PART OF THE COUNTRY BY THE
POLAR JET. THE AMPLIFIED BLOCKY NATURE OF THE UPPER FLOW PATTERN
WILL CAUSE THE UPPER LOW TO MOVE ONLY SLOWLY EAST...EVENTUALLY
PULLING OUT INTO THE EASTERN GREAT LAKES BY WEDNESDAY. THIS WILL
MAINTAIN A BROAD CYCLONIC FLOW OVER THE REGION AND ENABLE SNOW
SHOWERS TO PERSIST INTO WEDNESDAY BEFORE BEGINNING TO DIMINISH.

MODEL CONSENSUS HAS COME IN A TOUCH SLOWER WITH THE ARRIVAL OF THE
COLDER AIR ON MONDAY...WITH TEMPS LIKELY TO RECOVER 4 TO 5 DEGREES
BY MIDDAY MONDAY BEFORE BEGINNING TO FALL AS THE MORE INTENSE COLD
ADVECTION ARRIVES. THIS MAY ALSO BRIEFLY ENABLE SOME RAIN TO MIX IN
WITH ANY SNOW SHOWERS THROUGH EARLY MONDAY AFTERNOON OVER SOUTHEAST
COUNTIES. SNOW SHOWERS WILL BECOME WIDESPREAD BY MONDAY AFTERNOON
WITH THE POTENTIAL FOR HEAVIER SQUALLS DEVELOPING FROM LATE
AFTERNOON INTO MONDAY NIGHT AS PROGRESSIVELY COLDER AIR ARRIVES.
MODEL SOUNDINGS CONTINUE TO SHOW FAVORABLE THERMODYNAMIC PROFILES
WITH WEAK CONDITIONAL INSTABILITY AND STEEPER LAPSE RATES PRESENT.
WHILE ANY HEAVIER SQUALLS WILL PRODUCE RAPID DROPS IN
VISIBILITIES...MARGINAL NEAR SURFACE TEMPS MAY MITIGATE IMPACTS
SOMEWHAT AT LEAST INITIALLY DURING THE AFTERNOON. NOT SAYING THERE
WILL NOT BE TRAVEL ISSUES MONDAY AFTERNOON BUT THE SEVERITY OF THE
IMPACTS MAY BE DIMINISHED SOMEWHAT.

ALL BETS ARE OFF THOUGH ONCE THE SUN GOES DOWN AS TEMPS WILL TUMBLE
THROUGH THE 20S AND SNOW SHOWERS AND SQUALLS CONTINUE WITH TRAVEL
DIFFICULTIES STEADILY WORSENING. THE 850MB TROWAL DISCUSSED THE LAST
FEW DAYS IS STILL PROJECTED TO ROTATE THROUGH THE FORECAST AREA LATE
MONDAY NIGHT INTO TUESDAY MORNING AND WILL ENHANCE SNOWFALL COVERAGE
AND LOCALLY ENHANCE RATES. A PERIOD WITH SNOW GROWTH ZONES EXCEEDING
100MB DEPTH EARLY TUESDAY WILL FURTHER LEND ITS WEIGHT TO SNOW
SHOWER INTENSITY. AS THE DAY PROGRESSES TUESDAY...MORE FAVORABLE
THERMODYNAMIC PROFILES WILL ONCE AGAIN CONTRIBUTE TO SNOW SHOWERS
AND SQUALLS UNDER THE COLD POOL...AND THE VEERING OF LOW LEVEL FLOW
TO A 290 TO 310 DEGREE DIRECTION WILL INTRODUCE A POTENTIAL LAKE
MICHIGAN ENHANCEMENT FACTOR TO SNOW SHOWERS OVER THE NORTHEAST HALF
OF THE FORECAST AREA.

THE FAVORABLE LAKE MICHIGAN FETCH WILL PERSIST TUESDAY NIGHT BEFORE
WINDS BEGIN TO BACK ON WEDNESDAY. A BIT CONCERNED THAT OVERALL MODEL
GUIDANCE IS SHUTTING OFF THE SNOW SHOWER POTENTIAL TOO QUICKLY
WEDNESDAY AS ENERGY ALOFT TRANSITIONS THROUGH THE AREA ON THE BACK
SIDE OF THE DEPARTING UPPER LOW. IN ADDITION...THE AIRMASS WILL BE
MUCH COLDER ON WEDNESDAY WITH THE STRONG LIKELIHOOD THAT ANY
LINGERING MOISTURE WILL BE SQUEEZED OUT OF THE AIRMASS EVEN IN THE
ABSENCE OF MORE SUBSTANTIAL FORCING ALOFT. HAVE HELD ONTO A LOW
CHANCE FOR SNOW SHOWERS FOR MUCH OF THE FORECAST AREA AS A
RESULT...WITH THE EXPECTATION THAT SCATTERED SNOW SHOWERS LINGER
ACROSS THE NORTHEAST HALF OF THE FORECAST AREA ALL DAY.

TOYED WITH THE IDEA OF INTRODUCING AN IMPACT-BASED WINTER WEATHER
ADVISORY AS THE COMBINATION OF SCATTERED INTENSE SNOW SHOWERS AND
SQUALLS WITH WIND GUSTS PEAKING AT 25 TO 30MPH AND PROGRESSIVELY
COLDER TEMPS IMPACT THE FORECAST AREA AT TIMES FOR MUCH OF THE SHORT
TERM. HOWEVER WITH THE POSSIBILITY THAT MORE SIGNIFICANT IMPACTS DO
NOT COME UNTIL MONDAY NIGHT AND BEYOND...THINK ANOTHER SET OF MODEL
RUNS TONIGHT TO FINE TUNE TIMING OF IMPACTS WOULD BE BENEFICIAL.
WILL ISSUE A SHARPLY WORDED SPS AT THIS TIME.

FOR SNOWFALL TOTALS...A GENERAL 1 TO 3 INCHES REMAINS A SOLID CALL
THROUGH LATE WEDNESDAY...WITH HIGHER AMOUNTS FOCUSED OVER THE
NORTHEAST HALF OF THE FORECAST AREA. DO ANTICIPATE THERE WILL BE
LOCALLY HIGHER AMOUNTS WHERE HEAVIER SQUALLS OCCUR...AGAIN MOST
LIKELY FOCUSED OVER THE NORTHEAST HALF OF THE FORECAST AREA.

TEMPS...CONSIDERING THE INTENSIFYING COLD ADVECTION THROUGHOUT THE
PERIOD...GENERALLY TRENDED TOWARDS THE COLDER END OF GUIDANCE IF NOT
UNDERCUT ENTIRELY THROUGHOUT. AS STATED ABOVE...TEMPS WILL RISE A
BIT THE FIRST HALF OF MONDAY BEFORE STEADILY FALLING THEREAFTER.
HIGHS REMAIN IN THE 20S TUESDAY...AND LIKELY STAY IN THE TEENS
WEDNESDAY. SUBZERO WIND CHILLS ARE EXPECTED BY TUESDAY NIGHT AND
WEDNESDAY AS WELL...PROVIDING A REMINDER TO HOOSIERS THAT IT IS
STILL WINTER.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
ISSUED AT 322 PM EST SUN FEB 7 2016

THE MAIN FOCUS OF THE EXTENDED PERIOD WILL BE THE COLD TEMPERATURES.
FIRST...A FEW SNOW SHOWERS WILL LINGER OVER RANDOLPH COUNTY ON
WEDNESDAY NIGHT AS AN UPPER TROUGH PUSHES FARTHER EAST.  A LARGE
RIDGE OF HIGH PRESSURE WILL THEN DOMINATE THE WESTERN TWO-THIRDS OF
THE U.S. RESULTING IN DRY COLD WEATHER FOR THE DURATION OF THE LONG
TERM PERIOD.  HIGH TEMPERATURES WILL ONLY TOP OFF IN THE MID 20S TO
LOW 30S WITH OVERNIGHT LOWS IN THE TEENS.  BREEZY NORTHWEST WINDS ON
WEDNESDAY NIGHT/THURSDAY MORNING COMBINED WITH THE COLD TEMPERATURES
WILL PRODUCE WIND CHILLS BELOW ZERO.

&&

.AVIATION /DISCUSSION FOR THE 08/0600Z TAF ISSUANCE/...
ISSUED AT 1142 PM EST SUN FEB 7 2016

VFR THROUGH THE OVERNIGHT HOURS...THEN MVFR OR LOWER WITH OCCASIONAL
LIGHT SNOW SHOWERS MID MORNING ON.

LOW PRESSURE OVER THE UPPER MICHIGAN PENINSULA WILL MOVE SOUTHEAST
ACROSS THE GREAT LAKES AS AN UPPER TROUGH DEEPENS ACROSS OUR REGION.
WEATHER DEPICTION INDICATES CURRENTLY VFR ACROSS THE REGION BUT WITH
MVFR CONDITIONS OR LOWER ACROSS IOWA/SOUTHERN MINNESOTA WHICH WILL
SPREAD OUR WAY BY MID OR LATE MORNING.  SOME MODELS INDICATE A SLIGHT
IMPROVEMENT MONDAY AFTERNOON OR EVENING.  BUT STILL EXPECT MAINLY MVFR
CONDITIONS.

WEST WINDS OF 8 KNOTS OR LESS WILL BE THE RULE OVERNIGHT AND EARLY
MONDAY WITH WEST OR NORTHWEST WINDS 12 KNOTS AND GUSTS TO 20 TO 25 KNOTS
LATE MONDAY MORNING ON AS PRESSURE GRADIENT BECOMES A LITTLE TIGHTER.

&&

.IND WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SYNOPSIS...RYAN
NEAR TERM...RYAN/CP
SHORT TERM...RYAN
LONG TERM....TDUD
AVIATION...JH



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