Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 111805
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
205 PM EDT FRI APR 11 2014

.SYNOPSIS...
ISSUED AT 1058 AM EDT FRI APR 11 2014

A RIDGE OF HIGH PRESSURE WILL ALLOW FOR DRY CONDITIONS AND
SEASONABLE TEMPERATURES TODAY INTO THE FIRST PART OF SATURDAY. A
FRONTAL BOUNDARY WILL RETURN NORTHWARD AS A WARM FRONT FROM
SATURDAY NIGHT THROUGH SUNDAY MORNING PROVIDING MILD CONDITIONS
AND INCREASING CHANCES OF RAIN FOR THE SECOND HALF OF THE WEEKEND.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 357 AM EDT FRI APR 11 2014

EARLY MORNING SHOWERS SOUTH OF THE HWY 24 CORRIDOR TIED TO BRIEF
800-700 MB FGEN RESPONSE IN ADVANCE OF AN APPROACHING LOWER
AMPLITUDE WAVE SHOULD EXIT OUR FAR SOUTHEASTERN ZONES BETWEEN
12-13Z. CANNOT RULE OUT A RUMBLE OF THUNDER AND LOCALIZED RAINFALL
AMOUNTS UP TO TWO TENTHS IN THE FAR SOUTH (MARION-HARTFORD CITY).
GRADUAL HEIGHT RISES/WEAK WAA IN WAKE OF THIS UPPER WAVE/FRONT AND
SOUTH OF ANOTHER PV ANOMALY TRACKING EAST INTO THE NORTHERN GREAT
LAKES LATER TODAY WILL RESULT IN A MILD/DRY PERIOD OTHERWISE.
TEMPERATURES SHOULD RECOVER WELL INTO THE 60S BY THIS AFTERNOON
AS DRY AIRMASS AND THINNING HIGH LEVEL CLOUDS SUPPORT RELATIVELY
DEEP MIXING UP TO NEAR 6000 FT.

WEAK POST FRONTAL COOLING IN TANDEM WITH CLEARING SKIES/CALM
WINDS ALLOWED AREAS OF FOG TO DEVELOP OVERNIGHT ACROSS THE
NORTHERN HALF OF THE FORECAST AREA. WILL MONITOR TRENDS AS LOCALLY
DENSE FOG MAY IMPACT/SLOW DOWN THE MORNING COMMUTE BEFORE QUICKLY
BURNING OFF.

&&

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 357 AM EDT FRI APR 11 2014

HEMISPHERIC SCALE PATTERN REAMPLIFICATION WILL COMMENCE ON SATURDAY
AS A MERIDIONAL JET STREAK DIVES INTO THE WESTERN CONUS AND CARVES
OUT A DEEP LONGWAVE TROUGH...WITH THE ABSORPTION OF A CLOSED LOW
CURRENTLY OFF THE CALIFORNIA COAST. THIS WILL RESULT IN INCREASED
SOUTHWEST FLOW/WAA LOCALLY AS THE UPSTREAM TROUGH TAKES SHAPE.
EXPECT MOST AREAS WILL REMAIN PREDOMINATELY DRY ON SATURDAY AS THE
WARM FRONT LIFTS NORTH BUT MODELS ARE HINTING AT SOME WEAK 295-300K
ISENTROPIC ASCENT THAT CLIPS OUR AREA AROUND MIDDAY. WEAK ASCENT
COUPLED WITH THE POTENTIAL FOR AROUND 500 J/KG OF SBCAPE COULD
GENERATE AN ISOLATED SHOWER OR THUNDERSTORM. GFS FORECAST SOUNDINGS
STILL SHOW A GOOD DEAL OF LOW LEVEL DRY AIR AND A MODEST CAPPING
INVERSION THOUGH. GIVEN THAT BETTER LOW LEVEL CONVERGENCE/SYSTEM
RELATIVE ISENTROPIC OMEGAS ARE ALSO FOCUSED NORTH OF OUR
CWA...DECIDED TO HOLD OFF ON ANY SLIGHT CHANCE MENTION FOR NOW. MAIN
STORY WILL PROBABLY BE THE WARM TEMPS. FORECAST SOUNDINGS STILL
INDICATE PBL MIXING TO AROUND 850MB WITH TEMPS AT THAT LEVEL AROUND
10C BY THE AFTERNOON. AT LEAST PARTLY SUNNY SKIES AND INCREASING WAA
COULD ALLOW TEMPS TO EASILY APPROACH THE MID 70S...CERTAINLY NOT
UNHEARD OF FOR MID APRIL BUT STILL WELL ABOVE CLIMATOLOGICAL
AVERAGES.

ATTENTION THEN TURNS TO VERY ACTIVE AND STRONG BAROCLINIC ZONE THAT
WILL TAKE SHAPE FROM THE CENTRAL GREAT LAKES TO THE SOUTHERN PLAINS
DURING THE LATTER HALF OF THE WEEKEND. LARGE SUBTROPICAL RIDGE WILL
BUILD OFF THE EAST COAST DURING THIS TIME WITH A CORRESPONDING 150+
KT UPPER LEVEL JET STREAK DEVELOPING OVER EASTERN CANADA AS THE
INCREASINGLY HIGH AMPLITUDE/SHORT WAVELENGTH CENTRAL NOAM TROUGH
APPROACHES. VERY COLD AIR WILL BE DRAWN SOUTH BY THIS HIGHLY
AMPLIFIED PATTERN AND WILL RESULT IN A VERY SHARP TEMPERATURE
GRADIENT OVER THE REGION AS THE EAST COAST RIDGE HOLDS FIRM.
TIGHTENING THERMAL GRADIENT NOT ONLY SIGNALS INCREASING
FRONTOGENETIC FORCING AHEAD OF THE APPROACHING TROUGH BUT THIS FRONT
WILL TEND TO MOVE VERY SLOWLY AS IT BECOMES ALIGNED NEARLY PARALLEL
TO THE FLOW ALOFT. MEANWHILE...DEEP SOUTHWEST FLOW WILL ADVECT A
VERY HIGH THETA-E AIRMASS INTO THE REGION WITH AMPLE MOISTURE (PWATS
AROUND 1.25 INCHES) AND SUFFICIENT INSTABILITY TO SUPPORT A
CONVECTIVE ELEMENT IN ANY WAVES OF PRECIP THAT DEVELOP. QUESTION IS
AND ALWAYS HAS BEEN WHERE EXACTLY THIS FRONTAL BOUNDARY AND AXIS OF
HEAVY RAIN SETS UP. TO THIS POINT...THERE HAS BEEN A SLIGHT CHANGE
IN THE 00Z NCEP DETERMINISTIC GUIDANCE. LATEST NAM AND GFS NOW IN
MUCH BETTER AGREEMENT WITH THE ECMWF IN SUGGESTING THE BULK OF THE
RAIN WILL HOLD OFF IN OUR AREA UNTIL MONDAY AS THE BAROCLINIC ZONE
REMAINS FOCUSED TO OUR NORTHWEST. STILL HAVE A GOOD CHANCE OF
MODERATE RAIN WHEN THE FRONT ACTUALLY ARRIVES ON MONDAY BUT THE
POTENTIAL FOR MULTIPLE ROUNDS OF PRECIP THAT ADD UP TO HIGH QPF
TOTALS HAS BEEN REDUCED. NOT READY TO FULLY GIVE UP ON EARLIER
ROUNDS OF RAINFALL GIVEN THE POTENTIAL FOR CONVECTIVE WAVES TO
MUDDLE UP THE SYNOPTIC ENVIRONMENT BUT DID REDUCE POPS/QPF AMOUNTS
FOR ALL BUT OUR FAR NORTHWEST IN THE SATURDAY NIGHT THROUGH SUNDAY
NIGHT PERIODS. THIS SHOULD RESULT IN ONE MORE VERY WARM DAY SUNDAY
BEFORE THE BOTTOM FALLS OUT LATE MONDAY. POSTFRONTAL 850MB TEMPS
DROP TO ALMOST -12C BY TUESDAY MORNING...WHICH IS ABOUT 2SD BELOW
NORMAL. TUESDAY`S HIGHS MAY NOT GET OUT OF THE 30S IN SOME AREAS
GIVEN LATEST MEX AND CONSRAW GUIDANCE WITH OVERNIGHT LOWS IN THE MID
TO UPPER 20S. SURGE OF MUCH COLDER AIR COULD ALSO LEAD TO SOME BRIEF
SNOW ON THE BACK EDGE OF EXITING PRECIP LATE MONDAY BUT NO
ACCUMULATION EXPECTED. DRIER CONDITIONS AND SLOWLY MODERATING TEMPS
RETURN FOR THE LATTER HALF OF NEXT WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 204 PM EDT FRI APR 11 2014

SFC RIDGE OVERHEAD WILL SHIFT EWD THIS PD AND EXPAND ALG THE EAST
COAST AS LOW AMPLITUDE TROUGHING OVR SE CANADA WEAKENS AND FLATTENS
ALOFT ACRS THE ERN US. NET RESULT AT THE SFC IS DRY WX W/INCREASING
S/SWRLY FLW. XPC VFR CONDS TO CONT THROUGH THE PD W/VIGOROUS GRADIENT FLW
DVLPG SAT AFTN W/SFC GUSTS AOA 25KTS.

&&

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

$$

SYNOPSIS...STEINWEDEL/KG
SHORT TERM...STEINWEDEL
LONG TERM...AGD
AVIATION...T


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