Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 220750
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
350 AM EDT WED APR 22 2015

.SYNOPSIS...
ISSUED AT 350 AM EDT WED APR 22 2015

ANOTHER BREEZY DAY EXPECTED TODAY BUT WIND SPEEDS WILL NOT BE AS
HIGH AS YESTERDAY. EXPECT GUSTS OF 25 TO 35 MPH WITH PERHAPS A FEW
GUSTS APPROACHING 40 MPH. TEMPERATURES TODAY WILL REMAIN IN THE 40S.
OVERNIGHT LOWS WILL DIP INTO THE LOW 30S WITH FROST AND FREEZE
CONDITIONS POSSIBLE. COLD AND DRY CONDITIONS WILL THEN PERSIST
THROUGH FRIDAY.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 350 AM EDT WED APR 22 2015

ANOTHER WINDY DAY IN STORE FOR THE AREA...THOUGH NOT AS EXTREME AS
YESTERDAY. STRONG CAA HAS BROUGHT 850MB TEMPS DOWN TO AROUND -8C AND
MOST MODEL FORECAST SOUNDINGS SHOW MIXING DEPTHS ONLY CLIMBING TO
AROUND 5-6 KFT. THIS IS IN CONTRAST TO YESTERDAY WHEN SEVERAL MODELS
SUGGESTED MIXING HEIGHTS TO 8-9 KFT...WHICH SEEM TO HAVE VERIFIED
BASED ON INCREDIBLE 11 KFT MIXED LAYER SEEN ON 00Z KILX SOUNDING.
WIND FIELD ALOFT IS ALSO NOT AS IMPRESSIVE WITH THE CORE OF THE
700MB JET SHIFTING SOUTHEAST OF OUR AREA. THAT BEING SAID...WIND
SPEEDS AT THE TOP OF THE BOUNDARY LAYER ARE STILL IN THE 30-40 KT
RANGE FOR TODAY AND SUSPECT THERE WILL BE A FEW GUSTS OF 35-40 MPH
AT THE SURFACE. THIS IS JUST SHY OF ADVISORY CRITERIA (45 MPH) AND
PLAN TO JUST HIGHLIGHT STRONG WINDS IN THE HWO AND HANDLE WITH SPS`S
AS CONDITIONS WARRANT LATER TODAY.

ALSO SOME CONCERN FOR ANOTHER ROUND OF SHOWERS IN OUR NORTHERN
COUNTIES GIVEN STEEP LAPSE RATES AND AT LEAST SOMEWHAT DECENT
SATURATION IN CYCLONIC FLOW ALOFT. HIGHER RESOLUTION MODELS ALSO
HINTING AT A COUPLE OF WEAK VORTICITY SHREDS ROTATING THROUGH
SOUTHERN LOWER MICHIGAN...ONE EARLY THIS MORNING AND ANOTHER DURING
THE EVENING...WITH SOME SLIGHTLY ENHANCED CONVERGENCE IN WEAK
SURFACE PRESSURE TROUGH(S). DIURNAL TIMING IS NOT IDEAL THOUGH.
SHOWERS UPSTREAM ARE STRUGGLING IMMENSELY IN STABLE ENVIRONMENT.
THIS WEAK TROUGH MAY GET SOME DIURNAL BOOST AFTER SUNRISE AS IT
CROSSES OUR NORTHERN COUNTIES (MODELS EVEN HINT AT SOME LAKE INDUCED
INSTABILITY GIVEN HOW COLD THIS AIRMASS IS) BUT ANY PRECIP WILL BE
VERY LIGHT AND ISOLATED. SAME WITH ANYTHING THAT OCCURS THIS
AFTERNOON AND EVENING GIVEN WEAK FORCING AND SEVERELY LIMITED
MOISTURE. STILL...DONT FEEL COMFORTABLE WITH AN ENTIRELY DRY
FORECAST AND HAVE ADDED SPRINKLES AND SLIGHT CHANCE POPS TO OUR
NORTHERN COUNTIES. UNFORTUNATELY IF ANY MEASURABLE PRECIP DOES OCCUR
IT COULD ACTUALLY BE A MIX OF RAIN AND SNOW...ESPECIALLY FOR OUR
MICHIGAN COUNTIES...AS SURFACE WET BULB TEMPS WILL BE HOVERING
AROUND THE FREEZING MARK. NO ACCUMULATION EXPECTED BUT WOULDN`T BE
SURPRISED TO SEE A FEW ISOLATED SNOW REPORTS IN OUR FAR NORTH.

TEMPS TODAY WILL LIKELY REMAIN STUCK IN THE 40S FOR MOST LOCATIONS
GIVEN THERMAL PROFILES ALOFT. SOME CONCERN FOR FROST/FREEZE
CONDITIONS TONIGHT AS SURFACE TEMPS DIP INTO THE LOWER 30S.
HOWEVER...MAJORITY OF LATEST GUIDANCE KEEPS SURFACE WINDS IN THE
5-10 KT RANGE OVERNIGHT WITH HIGH PRESSURE STILL WELL TO OUR WEST.
COULD ALSO BE SOME LINGERING CLOUD COVER IN OUR NORTHERN COUNTIES.
THIS LEADS TO LOW CONFIDENCE ON BOTH TEMPS BELOW FREEZING AND FROST
FORMATION. HEADLINES MAY EVENTUALLY BE NECESSARY BUT PREFER TO LET
DAY SHIFT SORT THROUGH 12Z DATA AND MAKE A FINAL CALL ON WHAT (IF
ANY) HEADLINES ARE NECESSARY AND WHERE. WILL CONTINUE TO HIGHLIGHT
THE THREAT IN THE HWO.

&&

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 350 AM EDT WED APR 22 2015

DEEP VERTICALLY STACKED LOW EXPECTED TO WEAKEN AND MOVE SLOWLY EAST
THU-FRI ALLOWING RIDGE OVER THE PLAINS TO MOVE EAST ACROSS OUR AREA
RESULTING IN FAIR WX WITH A SLOW WARMING TREND... HWVR GOOD
RADIATIONAL COOLING THU NIGHT SHOULD ALLOW TEMPS TO FALL BLO
FREEZING AGAIN OVER ALL BUT PERHAPS THE SWRN PORTION OF THE CWA.

CUT-OFF LOW OVER SRN CA EXPECTED TO GET KICKED E-NE INTO THE PLAINS
FRI... AND THEN SHEAR OUT AS IT MOVES THROUGH THE MIDWEST AND
ENCOUNTERS NWLY FLOW ASSOCIATED WITH STILL LINGERING DEEP LOW OVER
SERN CANADA ON SATURDAY. APCHG SYSTEM SHOULD TAP DEEP MOISTURE IN
PLACE OVER THE SOUTH-CENTRAL U.S. AS IT MOVES INTO THE PLAINS AND
REMAIN SUFFICIENTLY STRONG TO CAUSE DECENT LIFT TO AT LEAST MOVE
INTO SWRN PORTIONS OF OUR CWA SATURDAY... SUGGESTING GOOD POTENTIAL
FOR RAIN IN THIS AREA... WITH LESSER CHANCES NE WHERE A COMBINATION
OF DRY LOW LEVEL EASTERLY FLOW AND A SHEARING OUT SYSTEM SHOULD
LIMIT IF NOT TOTALLY PREVENT RAINFALL. CLOUDINESS AND POTENTIAL
RAINFALL SHOULD RESULT IN COOLER TEMPS SATURDAY WITH HIGHS ONLY NEAR
50.

THE UPR TROF THAT KICKS OUT THE SRN CA CUT-OFF IS EXPECTED TO DIG
INTO THE FOUR CORNERS REGION SUNDAY AND THEN EJECT E-NE INTO THE
SRN/CENTRAL PLAINS MONDAY. 00Z GFS SUGGESTS THIS SYSTEM WILL MERGE
WITH A LOW DIGGING SOUTH FROM CENTRAL CANADA RESULTING IN A VERY WET
TUE IN OUR AREA... BUT THIS SOLUTION IS A MAJOR DEPARTURE FROM
EARLIER RUNS AND HAS LITTLE SUPPORT FROM THE GFS ENSEMBLES. THE
ECMWF HAS REMAINED CONSISTENT SUGGESTING PRECIP FROM THIS SYSTEM
WILL STAY SOUTH OF OUR CWA TUE WITH CONSIDERABLY SLOWER AND LESS
DYNAMIC INTERACTION WITH THE NRN STREAM. THIS SEEMS MORE PLAUSIBLE
AND GIVEN BETTER RUN-RUN CONTINUITY IS THE PREFERRED SOLUTION...
THOUGH DID MAINTAIN A LOW POP IN THE FCST IN DEFERENCE TO THE 00Z
GFS.  SLOW WARMING TREND SHOULD RESUME SUNDAY-TUESDAY WITH HIGHS
BACK INTO THE U50S/L60S AND LOWS CLIMBING TO THE U30S/L40S BY TUE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 120 AM EDT WED APR 22 2015

POSTFRONTAL THERMAL TROUGH WITH 850MB TEMPS BELOW -8C IS CURRENTLY
PUSHING SOUTHWARD AND MAY BRING SOME BRIEF MVFR CIGS TO KSBN
DURING THE EARLY MORNING HOURS. SUPPORT FOR THIS SEEN IN BOTH 00Z
FORECAST SOUNDINGS AND UPSTREAM OBS. DEEP MIXING WILL THEN COMMENCE
LATER THIS MORNING...BRINGING ANOTHER ROUND OF HIGH BASED
CU/ALTOCU AND STRONG WESTERLY WINDS. MIXING DEPTHS AND WIND
PROFILES ARE NOT AS HIGH AS YESTERDAY AND WIND GUSTS AT THE
SURFACE WILL BE LESS AS A RESULT. STILL EXPECT SOME GUSTS AROUND
30 KTS THOUGH.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 4 PM EDT THIS AFTERNOON FOR LMZ043-
     046.

&&

$$

SYNOPSIS...AGD
SHORT TERM...AGD
LONG TERM...JT
AVIATION...AGD


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