Area Forecast Discussion
Issued by NWS Northern Indiana

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KIWX 070231
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1031 PM EDT SUN JUL 6 2014

.SYNOPSIS...
ISSUED AT 356 PM EDT SUN JUL 6 2014

NUMEROUS SHOWERS AND THUNDERSTORMS ARE EXPECTED LATER TONIGHT AS
A FAST MOVING UPPER LEVEL DISTURBANCE TRACKS INTO THE GREAT LAKES
REGION...DRAWING A FRONTAL BOUNDARY EASTWARD. WIDESPREAD SEVERE
WEATHER IS NOT EXPECTED BUT AN ISOLATED STRONG TO SEVERE STORM MAY
BE POSSIBLE ACROSS NORTHWEST INDIANA AND SOUTHWEST MICHIGAN
THROUGH MIDNIGHT. CHANCE OF SHOWERS AND STORMS WILL LINGER INTO
TOMORROW BEFORE COLD FRONT FULLY CLEARS THE AREA. LOW TEMPERATURES
TONIGHT WILL RANGE FROM THE UPPER 60S TO LOWER 70S WITH HIGHS
TOMORROW IN THE LOW 80S.

&&

.UPDATE...
ISSUED AT 1026 PM EDT SUN JUL 6 2014

TSTMS WHICH DEVELOPED OVER NWRN PORTION OF CWA THIS EVE STRUGGLED
TO PERSIST IN WK DEEP LAYER SHEAR AND APPEAR ON A DOWNWARD TREND
AS THEY MOVE EAST INTO LESS UNSTABLE AIR OVER NERN PORTION OF THE
AREA. SCT TSTMS FROM SE WI TO CENTRAL IA SHOULD MOVE E-SE WITH
850-300MB MEAN WIND AND TOWARD INSTABILITY AXIS FROM NW IL-NW
INDIANA. HWVR EVE SOUNDINGS FROM CENTRAL/NRN IL INDICATING A
FAIRLY STOUT CAP SO QUESTIONABLE IF THESE STORMS WILL SURVIVE TO
REACH OUR AREA OVERNIGHT. LOWERED POPS A BIT OVERNIGHT BUT LEFT
IN LIKELY CATEGORY ACROSS THE NW AND ALSO MOVED TIMING OF HIGHEST
POPS BACK A COUPLE HOURS TO 08Z-10Z TIMEFRAME ON UPDATE.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 356 PM EDT SUN JUL 6 2014

AFTERNOON WATER VAPOR IMAGERY SHOWS WELL-DEFINED MIDLEVEL SHORTWAVE
CURRENTLY ENTERING THE NORTHERN GREAT LAKES ON THE NOSE OF
APPROACHING MID/UPPER LEVEL JET STREAK. THERE IS ALSO A MORE SUBTLE
VORT MAX CROSSING MINNESOTA. THESE TWO FEATURES WILL DRIVE A SURFACE
COLD FRONT...CURRENTLY JUST EXITING MINNESOTA...SOUTHEAST OVERNIGHT.
LOW LEVEL THETA-E FIELDS SHOW A VERY MOIST AND UNSTABLE AIRMASS HAS
BEEN ADVECTED INTO THE REGION AHEAD OF THIS FRONT. INSTABILITY BEING
DRIVEN NOT ONLY BY LOW LEVEL MOISTURE POOLING BUT ALSO BY MIDLEVEL
LAPSE RATES AT OR ABOVE 7 C/KM OVER EASTERN IA...SOUTHERN WI...AND
NORTHERN IL. WIDESPREAD CLOUD DEBRIS FROM OVERNIGHT MCS HAS TEMPERED
THE DIURNAL DESTABILIZATION IMMEDIATELY AHEAD OF THE FRONT ACROSS
NORTHERN IA AND SOUTHERN WI THOUGH. FURTHER SOUTH...SPC/RAP
MESOANALYSIS SHOWS MLCAPES OVER 2000 J/KG WITH LITTLE TO NO CIN.
THIS MOISTURE/INSTABILITY PLUME IS ALSO CREEPING INTO OUR WESTERN
COUNTIES WITH SURFACE DEWPOINTS AROUND 70F IN OUR WEST BUT STILL
ONLY LOW 60S IN OUR EASTERN ZONES. LACK OF ANY TRIGGER MECHANISM
WILL KEEP CONVECTION IN AND IMMEDIATELY UPSTREAM OF OUR CWA ISOLATED
THROUGH THE EARLY EVENING BUT EXPECT CONVECTION TO EXPAND ONCE
PREFRONTAL TROUGH REACHES BETTER INSTABILITY OVER NORTHERN IL.
SHOWERS AND THUNDERSTORMS WILL THEN PUSH SOUTHEAST INTO OUR CWA
OVERNIGHT. CONSENSUS OF HI-RES CONVECTION ALLOWING MODELS SUGGEST
THIS ACTIVITY WILL ARRIVE IN OUR NORTHWEST SHORTLY BEFORE 06Z AND
EXIT THE SOUTHEAST AROUND 12Z. ADEQUATE SYNOPTIC FORCING AND LOW
LEVEL CONVERGENCE IN A REGION OF DECENT MOISTURE AND ELEVATED
INSTABILITY SHOULD ALLOW FOR NUMEROUS SHOWERS AND THUNDERSTORMS
DURING THIS PERIOD AND HAVE THEREFORE BUMPED POPS INTO LIKELY
CATEGORY. AN IDEA ALSO SUPPORTED BY MOST OF LATEST HI-RES GUIDANCE.
MAY ALSO BE A FEW STORMS AHEAD OF THE MAIN LINE IN THE 00-06Z PERIOD
AS WELL. THERE IS A SLIGHT RISK OF SEVERE WEATHER IN OUR NORTHWEST
COUNTIES. 0-6KM BULK SHEAR VALUES ARE AROUND 30 KTS IMMEDIATELY
UPSTREAM AND THERE IS AMPLE INSTABILITY OVER NORTHERN IL BUT
CONVECTION WILL BE OUTRUNNING THE BETTER SHEAR/INSTABILITY BY THE
TIME IT REACHES OUR CWA. A FEW REMNANT STRONG/SEVERE MULTICELL
CLUSTERS MAY REACH OUR NORTHWEST COUNTIES EARLY ENOUGH BUT EXPECT
CONVECTION WILL GRADUALLY LOSE STEAM AFTER 06Z AS IT PUSHES
SOUTHEAST INTO OUR AREA. ANY STORMS THAT MANAGE TO DEVELOP AHEAD OF
THE MAIN LINE THIS EVENING MAY ALSO HAVE TO BE WATCHED GIVEN
MODERATE SHEAR/INSTABILITY ACROSS OUR WESTERN COUNTIES BUT
AGAIN...THIS ACTIVITY SHOULD REMAIN FAIRLY ISOLATED. DAMAGING
STRAIGHT-LINE WINDS WILL BE THE MAIN THREAT.

LIMITED TIME WINDOW FOR DESTABILIZATION LATE TOMORROW MORNING BEFORE
ACTUAL SURFACE FRONT PASSES. HAVE THEREFORE HELD WITH JUST CHANCE
POPS IN OUR SOUTHEAST THIRD. SEVERE RISK STILL LOOKS TO HOLD JUST
SOUTH OF OUR CWA THOUGH AN ISOLATED STRONG STORM MAY BE POSSIBLE IN
OUR FAR SOUTHEAST COUNTIES AROUND MIDDAY. THERMAL PROFILES NOT
PARTICULARLY COLD BEHIND THIS INITIAL FRONT AND SHOULD STILL REACH
THE LOW 80S...ESPECIALLY IF CLOUDS DISSIPATE MORE THAN EXPECTED.

&&

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 356 PM EDT SUN JUL 6 2014

EASTERN CONUS TROF TO DEEPEN AS NORTHERLY DISPLACED INTERMOUNTAIN
SUBTROPICAL ANTICYCLONE ASSERTS RIDGE NORTHWARD ALONG THE GREAT
DIVIDE INTO MID WEEK. SEVERAL EMBEDDED SHORTWAVES WITHIN PRIMARY
HUDSON/JAMES BAY CENTERED VORTEX TO DRIVE ASSOCIATED/PRIMARILY WEAK
FRONTAL ZONES SEWD THROUGH WESTERN/SOUTHERN GREAT LAKES. MOST
SIGNIFICANT FRONTAL BOUNDARY AND SOUTHERN PERIPHERY OF 40-70M/12
HOUR HEIGHT FALLS CONSENSUS TIMED TO LATE MONDAY NIGHT INTO
TUESDAY...COMMENSURATE WITH ONGOING FCST. FRONTAL BOUNDARY PASSAGE
ALONG WITH POTENTIAL COMPOSITE COLD POOL OUTFLOW SHOULD PROVIDE
THOROUGH BOUNDARY LAYER SCOUR BY TUESDAY NIGHT. AMID LARGE SCALE
DRY/SUBSIDENT CP AIRMASS AND WITH 925MB THERMAL TROF LOCKED FROM
SWRN ONTARIO/LWR MI/NERN IL F84-96 PER WELL CLUSTERED
GUIDANCE...HAVE DROPPED LOWS WED NIGHT OVER BLENDED APPROACH A FEW
DEGREES...MORE IN LINE WITH EC/GFS ENSEMBLE AVERAGES AND TREND.
QUESTIONABLE RETURN MOISTURE INTO NEXT WEEKEND SANS MIDDLE/EASTERN
GOMEX FEED. GEM OUTLIER WITH RESPECT TO LATE TIMING OF SHORTWAVE
EXUDED FROM NORTHERN PAC INTO DOWNSTREAM WESTERLIES. PREFERENCE
LEANS TOWARD MORE CONSISTENT RUN TO RUN ECMWF WITH BEST TIMING
SAT/SAT NIGHT... THOUGH WITH BETTER CONCEDE LOW PROBABILITY OF
UPSTREAM MCS DEVOLVING INTO CWA FRIDAY NIGHT.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 724 PM EDT SUN JUL 6 2014

RECENT AMDAR SOUNDINGS OVER NRN IN/SRN MI INDICATE AIRMASS OVER
OUR AREA IS AT LEAST MODERATELY UNSTABLE WITH A WK CAP AROUND 5K
FT AND A VEERING WIND PROFILE SUGGESTING SOME UVM. CANT RULE OUT
SCT TSTMS DEVELOPING IN THE AREA THIS EVE... BUT BETTER CHC
REMAINS LATER TONIGHT AS SCT TSTMS ALONG PRE-FRONTAL
TROF/INSTABILITY AXIS FM NW WI TO CENTRAL IA MOVE SE. BASED ON
EXTRAPOLATION AND LATEST HRRR... MOVED BACK TIMING OF THIS
CONVECTION IMPACTING THE TERMINALS A COUPLE OF HOURS. CDFNT SHOULD
SAG INTO UNSTABLE AIRMASS OVER NRN INDIANA ON MONDAY. HWVR...
FRONT WILL BE BECOMING INCREASINGLY DIFFUSE WITH WK HEIGHT RISES
AND BACKING WINDS ALOFT OVER THE AREA IN RESPONSE TO ANOTHER
SHRTWV DIGGING SE INTO MN. SO WHILE CANT RULE OUT TSTMS AT THE
TERMINALS MONDAY AFTN... CHANCES TOO LOW TO ADD TO TAFS ATTM.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...BEACH HAZARDS STATEMENT UNTIL 3 AM CDT MONDAY FOR INZ003.

MI...BEACH HAZARDS STATEMENT UNTIL 4 AM EDT MONDAY FOR MIZ077.

OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 4 AM EDT MONDAY FOR LMZ043-046.

&&

$$

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


VISIT US AT WWW.WEATHER.GOV/IWX (ALL LOWER CASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.NORTHERNIN.GOV
WWW.TWITTER.COM/NWSIWX
WWW.YOUTUBE.COM/NWSNORTHERNINDIANA





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.