Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 170534
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
134 AM EDT FRI APR 17 2015

.SYNOPSIS...
ISSUED AT 745 PM EDT THU APR 16 2015

SKIES WILL CLEAR OVERNIGHT WITH LIGHT WINDS AND LOW TEMPERATURES
IN THE MID 40S. FRIDAY WILL BE A NICE DAY AROUND THE REGION WITH
SUNNY SKIES AND HIGH TEMPERATURES IN THE MID 70S.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 352 PM EDT THU APR 16 2015

A WEAK UPPER TROF WITH SOME LOW LEVEL MOISTURE HAS BEEN SUFFICIENT
TO PRODUCE SCATTERED SHOWERS OVER THE AREA INTO MID AFTERNOON.
SUBSIDENCE BEHIND THIS SYSTEM SHOULD HELP TO ELIMINATE SHOWERS EARLY
TONIGHT... AND TO ALLOW CLEARING. SOME RADIATION FOG IS POSSIBLE
OVERNIGHT GIVEN LIGHT WINDS...CLEARING SKIES AND RECENT RAINFALL.
HOWEVER... LEFT FOG OUT FOR NOW AS MUCH DRIER AIR JUST TO THE
NORTHWEST OF THE AREA SHOULD BEGIN TO SPREAD OVER THE FORECAST AREA.
TEMPERATURES SHOULD RISE ABOVE NORMAL FRIDAY AS 850 MB TEMPS RISE TO
NEAR 10C WITH PLENTY OF SUN. VERY CHILLY LAKE MICHIGAN WATER TEMPS
JUST ABOVE FREEZING MAY CAUSE AFTERNOON TEMPERATURES NEAR THE LAKE
TO SUBSTANTIALLY FALL AS WINDS BECOME NORTHWEST.

&&

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 352 PM EDT THU APR 16 2015

FOR THE LONG TERM FORECAST...UPPER LEVEL LOW SETS ITS SIGHTS ON THE
GREAT LAKES REGION

FRIDAY NIGHT WILL BE MOSTLY QUIET WITH WEAK SFC HIGH PRESSURE AND
RATHER ZONAL FLOW ALOFT. LOW TEMPERATURES WILL BE ABOVE
NORMAL...LARGELY IN THE UPPER 40S AND LOW 50S.

ON SATURDAY...A 500MB CUT OFF LOW SPINNING OVER THE SOUTHWESTERN
U.S. WILL DRIFT EASTWARD. IN THE NORTHERN STREAM...LOW PRESSURE
TROUGH/SHORTWAVE WILL DIG SOUTHWARD INTO ALBERTA/MANITOBA BY
SATURDAY AFTERNOON. ALL OF THIS WILL AMPLIFY THE INCOMING RIDGE OVER
OUR CWA. THE GFS TRIES TO GENERATE PRECIPITATION IN THE NORTHERN CWA
LATE SAT AFTERNOON...BUT WITH OUR CWA UNDER THE RIGHT EXIT REGION OF
300MB JET...A BUILDING RIDGE AT 500MB...AND PWATS GENERALLY UNDER AN
INCH THINKING THIS IS UNLIKELY AND WILL LEAVE OUT POPS FOR NOW.
ECMWF/GEM/NAM ARE ALL CONSISTENT WITH THIS THINKING. ALL IN
ALL...SAT LOOKS LIKE A PRETTY DECENT DAY...WITH TEMPERATURES RISING
INTO THE 70S AND INCREASING CLOUDS INTO THE AFTERNOON.

DESPITE THE SUBTLE DIFFERENCES WITH PRECIPITATION DURING THE DAY
SATURDAY...BOTH ECMWF/GFS COME INTO GENERAL AGREEMENT FOR LARGE
SCALE PATTERN/SFC LOWS SAT NIGHT AND SUNDAY.

JET STREAM IS SPLIT IN THE UPPER LEVELS...WITH A STRONGER MORE
DEFINED NORTHERN STREAM AND A SOMEWHAT WEAKER SOUTHERN STREAM/AT
LEAST OVER OUR AREA. SUNDAY...MODELS HAVE THE CWA IN AN AREA OF
INCREASED DIVERGENCE DUE TO COUPLED JETS. WE WILL BE CENTERED
BENEATH THE RIGHT ENTRANCE REGION OF THE NORTHERN STREAM 100KT JET
STREAK OVER MINNESOTA/UPPER MI AND THE LEFT EXIT REGION OF THE
SMALLER 90 KT JET OVER SE IN...KY...AND TN.

IN THE MID LEVELS...SPLIT BEGINS TO PHASE...WITH THE CUT OFF LOW
LIFTING FROM THE SOUTHWESTERN U.S. INTO THE CENTRAL PLAINS SUNDAY
AND CONSOLIDATING WITH THE NORTHERN STREAM LOW SINKING SOUTHWARD OUT
OF MANITOBA SUN NIGHT/MON AM. CWA IS UNDER REGION OF DPVA FROM THE
APPROACHING BROADER SCALE TROUGH...WITH A SHORTWAVE EJECTING INTO
THE AREA SUNDAY MORNING/AFTERNOON OUT AHEAD OF THE MAIN SOUTHERN
STREAM PV ANOMALY CENTERED OVER KANSAS.

1000-700MB MOISTURE TRANSPORT IS MAXIMIZED SUNDAY MORNING AND SUNDAY
AFTERNOON AS WELL...WITH PWATS RISING TO ABOUT 1.4 INCHES...WHICH IS
ABOUT TWO STANDARD DEVIATIONS ABOVE NORMAL FOR APRIL. MODEST
ISENTROPIC ASCENT IS OBSERVED ON THE 295K SFC...AND SFC WARM FRONT
LIFTS NORTHWARD THROUGH THE DAY.

WITH AMPLE UPPER LEVEL SUPPORT AND ABUNDANT MOISTURE WILL KEEP THE
GOING HIGHER POPS FOR SUNDAY MORNING AND SUNDAY AFTERNOON. THINKING
THAT THERE MAY BE A BRIEF BREAK SUNDAY EVENING INTO THE EARLIEST
HOURS OF MONDAY MORNING ASSOCIATED WITH SUBSIDENCE IN THE WAKE OF
THE EXITING SHORTWAVE. BY THE LATER MORNING HOURS MAIN SOUTHERN
STREAM PV ANOMALY SWINGS THROUGH THE NW CWA...BRINGING ADDITIONAL
CHANCES FOR PRECIPITATION.

AS FOR THE EXTENDED...THE OVERALL SYSTEM BECOMES VERTICALLY STACKED
THROUGH THE WEEK. THE 500MB CLOSED LOW IS CENTERED OVER MINNESOTA
MONDAY MORNING...AND THE BROAD SFC LOW EXTENDS FROM SOUTHERN MI TO
NORTHERN ONTARIO. SFC LOW OCCLUDES/FILLS THROUGH THE WEEK...AND THE
500MB LOW SITS AND SPINS OVER MAINLY THE NORTHERN GREAT LAKES REGION
THROUGH THURSDAY.

LOOKS LIKE WE GET STUCK IN THE DRY SLOT MONDAY AFTERNOON INTO
TUESDAY MORNING...BEFORE THE UPPER LOW DRIFTS SOUTHWARD AND BRINGS
THROUGH SEVERAL ROUNDS OF SHORTWAVES THAT MAY/MAY NOT DEVELOP
PRECIPITATION. AS A RESULT...WILL BE KEEPING CONSENSUS POPS THROUGH
NEXT WEEK. THE BAD NEWS IS THAT TEMPERATURES LOOK TO BE SLIGHTLY
BELOW NORMAL FOR MID-LATE APRIL. HIGHS WILL REACH INTO THE
50S...WITH LOWS FLIRTING WITH THE MID 30S AT TIMES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 134 AM EDT FRI APR 17 2015

DRY AIR ADVECTION BEHIND EXITING SHORTWAVE IS GRADUALLY SCOURING
OUT CLOUDS ACROSS NORTHERN INDIANA. QUICK DROP IN TEMPS AND SLOW
ARRIVAL OF DRY AIR AT THE SURFACE HAS ALLOWED SOME FOG TO DEVELOP
OVER CENTRAL INDIANA. LOWER DEWPOINTS AT KSBN SUGGEST VERY LOW
POTENTIAL FOR FOG BUT COULD BE SOME BRIEF MVFR BR JUST BEFORE
SUNRISE BASED ON LATEST FORECAST SOUNDINGS. KFWA REMAINS ON THE
EDGE OF DENSER FOG JUST TO THE SOUTHWEST. SUSPECT DRY AIR
ADVECTION WILL WIN OUT HERE TOO BUT SOME MVFR BR IS POSSIBLE
THROUGH THE EARLY MORNING. OTHERWISE VFR CONDITIONS EXPECTED FOR
THE REST OF THE PERIOD AS HIGH PRESSURE REMAINS OVER THE AREA.

&&

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

$$

SYNOPSIS...BENTLEY
SHORT TERM...SKIPPER
LONG TERM...MCD
AVIATION...AGD


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