Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 181917
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
217 PM EST THU DEC 18 2014

.UPDATE...
THE SYNOPSIS...NEAR TERM AND SHORT TERM SECTIONS HAVE BEEN UPDATED BELOW.

&&

.SYNOPSIS...
ISSUED AT 217 PM EST THU DEC 18 2014

HIGH PRESSURE IN PLACE OVER THE UPPER MIDWEST AND THE OHIO VALLEY
WILL RESULT IN MAINLY DRY WEATHER THE NEXT COUPLE OF DAYS AS IT
SLOWLY PUSHES EAST THROUGH THE REGION.

A SERIES OF UPPER LEVEL WEATHER DISTURBANCES ARE EXPECTED TO PUSH
THROUGH THE OHIO VALLEY ON FRIDAY NIGHT AND SATURDAY NIGHT. THIS
WILL KEEP PLENTY OF CLOUDS IN PLACE ACROSS CENTRAL INDIANA INTO
THE WEEKEND ALONG WITH TEMPERATURES AT OR BELOW NORMALS.

THE NEXT BEST CHANCE FOR SIGNIFICANT PRECIPITATION WILL BE ON
TUESDAY INTO WEDNESDAY AS A DEEP UPPER TROUGH IS EXPECTED TO PUSH
INTO THE OHIO VALLEY FROM THE GREAT PLAINS.

&&

.NEAR TERM /TONIGHT/...

ISSUED AT 217 PM EST THU DEC 18 2014

SURFACE ANALYSIS EARLY THIS AFTERNOON SHOWS LARGE HIGH PRESSURE
STRETCHING FROM THE UPPER MIDWEST ACROSS INDIANA INTO THE
TENNESSEE VALLEY. RADAR SHOWS AREA OF LIGHT SNOW SHOWERS OVER
CENTRAL INDIANA...QUICKLY MOVING TO THE EAST. SURFACE OBS FAIL TO
SHOW MUCH IN THE WAY OF PRECIP REACHING THE GROUND.

MINIMAL ISENTROPIC LIFT AS SEEN ON THE 290K SURFACE WANES THIS
EVENING...AS A WEAK SHORT WAVE ALOFT QUICKLY DEPARTS TO THE EAST.
SATELLITE IMAGES CONTINUE TO SHOW PLENTIFUL CLOUDS UPSTREAM AND THE
SURFACE HIGH REMAINS RATHER DIRTY AS MINIMAL COLD AIR ADVECTION IS
ONGOING. THUS WILL TREND TOWARD A CLOUDY SKY OVERNIGHT WITH LOWS AT
OR BELOW MAVMOS.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...

ISSUED AT 217 PM EST THU DEC 18 2014

MAIN FORECAST CHALLENGE DURING THIS PERIOD WILL BE TEMPS. MODELS
CONTINUE TO SUGGEST QUICK WESTERLY FLOW ALOFT IN THE WAKE OF A
WEAK TROUGH OVER THE WESTERN UNITED STATES. MODELS SUGGEST THE
TROUGH ALOFT FLATTENS OUT AS THE FLOW BECOMES MORE ZONAL BY
SUNDAY. MEANWHILE...SEVERAL WEAK AND UNORGANIZED SHORT WAVE ALOFT
PASS ACROSS THE FORECAST AREA. HIGH PRESSURE AT THE SURFACE WILL
KEEP ANY GULF MOISTURE FROM REACHING THE AREA AND AS THE HIGH
DEPARTS SLOWLY TO THE EAST SURFACE CONVERGENCE AND DYNAMICS APPEAR
RATHER LIMITED. FORECAST SOUNDINGS CONTINUE TO SHOW A DRY COLUMN
ACROSS THE AREA. THUS WILL CONTINUE A DRY FORECAST THROUGH THE
PERIOD.

WITH EXTENSIVE CLOUDINESS UPSTREAM AMID THE DIRTY HIGH PRESSURE
SYSTEM AND TIME HEIGHT SECTIONS CONTINUING TO SHOW TRAPPED LOWER
LEVEL MOISTURE...WILL CONTINUE A MOSTLY CLOUDY FORECAST INTO
FRIDAY AND FRIDAY NIGHT. WITH STEADY STATE TEMPERATURE
ADVECTION...WILL TREND HIGH TEMPERATURES TOWARD THE 3 HOURLY TEMPS
AS HEATING WILL BE LIMITED.

LITTLE CHANGE IS EXPECTED ON FRIDAY NIGHT INTO SATURDAY IN THE
LOWER LEVELS AS TIME HEIGHTS CONTINUE TO KEEP PLENTIFUL TRAPPED
LOWER LEVEL MOISTURE. ADDING TO THE CHANCE FOR CLOUD COVER WILL BE
A QUICK MOVING SYSTEM THROUGH THE DEEP SOUTH AS SOME HIGH MOISTURE
SHOULD PUSH THROUGH THE OHIO VALLEY. AGAIN...WILL CONTINUE WITH A
MOSTLY CLOUDY SKY. GIVEN SOME CLOUDS AND STEADY TEMP ADVECTION
WILL TREND LOWS FRIDAY NIGHT AT OR ABOVE GUIDANCE AND TREND HIGHS
ON SATURDAY NEAR THE 3 HOURLY VALUES.

GFS AND NAM SUGGEST WEAK RIDGING TO BUILD ACROSS THE AREA ON
SUNDAY AMID THE MAINLY ZONAL FLOW. AT THE SURFACE HIGH PRESSURE
WILL BE FOUND WELL TO THE EAST...ALLOWING A WARMER SOUTHERLY FLOW
OF AIR TO CENTRAL INDIANA. FORECAST SOUNDINGS CONTINUE TO SUGGEST
HIGH SATURATION THROUGH SUNDAY. THUS WILL CONTINUE THE MOSTLY
CLOUDY TREND ALONG WARMER LOWS THAN MAV COOLER HIGHS THAN MEX.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
ISSUED AT 340 AM EST THU DEC 18 2014

EXTENDED MODELS AND ENSEMBLES AGREE THAT STRONG PACIFIC JET...ARCING
OVER A HIGH AMPLITUDE WEST COAST UPPER RIDGE...WILL DIVE SOUTHEAST
OVER THE CENTRAL UNITED STATES DURING THE EARLY AND MIDDLE PART OF
NEXT WEEK RESULTING IN AN UPPER TROUGH CLOSING INTO AN UPPER LOW AND
INTENSIFYING INTO A VERY STRONG SYSTEM BEFORE IT MOVES INTO
SOUTHEASTERN CANADA ON CHRISTMAS. MODELS WERE NOT TOO FAR OFF
REGARDING STRENGTH AND TIMING OF THIS SYSTEM...SO A BLEND OF THE
FURTHER NORTH 00Z GFS AND FURTHER SOUTH 12Z ECMWF LOOKS GOOD.

00Z MODELS ARE SHOWING AN UPPER TROUGH OVER SOUTHEASTERN SOUTH
DAKOTA OR NORTHWESTERN IOWA AT 00Z TUESDAY WITH BROAD AREA OF UPPER
DIFFLUENT FLOW ALOFT OVER THE OHIO VALLEY AND GREAT LAKES.
MEANWHILE...LOW LEVEL FLOW WILL BE SOUTHERLY BY MONDAY AND OPEN THE
OHIO VALLEY AND GREAT LAKES TO THE GULF RESULTING IN DEEPENING
MOISTURE TO GO ALONG WITH THE UPPER FORCING. THIS WILL BRING RAIN TO
THE AREA BY MONDAY AS WELL AS ABOVE NORMAL TEMPERATURES. THE WARMER
TEMPERATURES AND RAIN WILL BE SHORT-LIVED...HOWEVER AS COLDER AIR
RUSHES IN FROM THE NORTHWEST ON THE BACK END OF THE SYSTEM LATE
TUESDAY OR TUESDAY NIGHT. ALONG WITH THE COLDER AIR...UPPER IMPULSES
WILL MOVE ACROSS THE AREA IN THE CYCLONIC FLOW IN THE WAKE OF THE
DEPARTING STACKED LOW THAT SHOULD MOVE INTO QUEBEC EARLY CHRISTMAS.
THIS SHOULD GENERATE SOME SNOW WITH LIGHT ACCUMULATION POSSIBLE BY
CHRISTMAS EVE.

00Z GFS ENSEMBLE MOS TEMPERATURES LOOK TOO WARM THIS WEEKEND.
STRONGLY PREFER THE COOLER 00Z DECEMBER 17 EUROPEAN ENSEMBLE MEAN
TEMPERATURES.

&&

.AVIATION /DISCUSSION FOR THE 18/1800Z TAF ISSUANCE/...

ISSUED AT 1208 PM EST THU DEC 18 2014

FLIGHT CONDITIONS WILL HOVER RIGHT AROUND THE MVFR/VFR MARK INTO
THE NIGHT. HOWEVER...TIME CROSS SECTIONS ARE LEANING TOWARD DRIER
CONDITIONS AT ALL LEVELS EARLY TOMORROW MORNING. SO...ANTICIPATE
SCATTERING SOME TIME BETWEEN FRI 09-15Z...WHICH IS REFLECTED IN
TAFS. AT THAT POINT...VFR SHOULD BE THE PREVAILING FLIGHT CATEGORY
THROUGH THE REMAINDER OF TAF PERIOD. NORTHWEST WINDS WILL VEER
SLIGHTLY TO THE NORTHEAST LATE TONIGHT...BUT WILL REMAIN LIGHT.


&&

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

$$

SYNOPSIS...PUMA
NEAR TERM...PUMA
SHORT TERM...PUMA
LONG TERM...MK
AVIATION...TDUD

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