Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 201923
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
323 PM EDT MON APR 20 2015

.SYNOPSIS...
ISSUED AT 348 AM EDT MON APR 20 2015

SCATTERED SHOWERS ARE EXPECTED TODAY AS AN UPPER LEVEL DISTURBANCE
ROTATES THROUGH THE REGION IN THE WAKE OF STRONG SURFACE LOW
PRESSURE LIFTING NORTH. DAYTIME TEMPERATURES WILL REMAIN IN THE MID
TO UPPER 50S. SHOWERS WILL EXIT OVERNIGHT WITH LOWS AROUND 40
DEGREES. COOL WEATHER WILL PERSIST THROUGH MUCH OF THE UPCOMING WEEK.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 320 PM EDT MON APR 20 2015

PERIOD WILL FEATURE A STEADY FEED OF COOLER/DRIER AIR UNDER A
CLOSED LOW THAT WILL MEANDER INTO THE NORTHERN GREAT LAKES. SHOULD
BE JUST ENOUGH RESIDUAL BOUNDARY LAYER MOISTURE AND WEAK ASCENT
WITH A SECONDARY FEATURE TO GENERATE A FEW LIGHT SHOWERS/SPRINKLES
LATE THIS AFTERNOON/EVENING. DRY WITH DIMINISHING WINDS OTHERWISE
TONIGHT.

MIXED LAYER WILL BECOME VERY DEEP DURING THE DAY TUESDAY ON SOUTHERN
FRINGE OF NEGATIVE HEIGHT ANOMALY GIVEN LATE APRIL INSOLATION AND
-30C TEMPS AT 500MB. THIS IN COMBINATION WITH A LINGERING/TIGHT LOW
LEVEL HEIGHT GRADIENT WILL ENSURE A WINDY LATE MORNING/AFTERNOON
(GUSTS POSSIBLY APPROACHING ADVISORY CRITERIA)...AND ALSO ALLOW
HIGHS TO RECOVER WELL INTO THE 50S (MAYBE 60F SOUTH) DESPITE NEAR
ZERO 850 MB TEMPS. RESULTING STEEP LOW LEVEL LAPSE RATES UNDER
SHEAR/PV AXIS MAY BE ENOUGH TO TOUCH OFF A FEW DIURNALLY DRIVEN
SHOWERS/SPRINKLES ACROSS THE NORTH AS MODELS ALSO SHOW A DECENT
AMOUNT OF MOISTURE IN THE 800-650MB LAYER.

&&

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 320 PM EDT MON APR 20 2015

DEEP CUTOFF LOW OVER LAKE SUPERIOR WILL VERY SLOWLY ADVANCE EASTWARD
THROUGH THE WEEK...KEEPING OUR AREA UNDER THE INFLUENCE OF NORTHWEST
FLOW THROUGH THE LONG TERM PERIOD. THIS WILL RESULT IN TEMPERATURES
10 TO 15 DEGREES BELOW NORMAL THROUGH AT LEAST SATURDAY. COLDEST
PORTION OF THE AIRMASS WILL ARRIVE ON WEDNESDAY WITH H850 TEMPS
FORECAST BETWEEN -6C AND -8C. AS A RESULT...MODELS HAVE CONTINUED
THEIR DOWNWARD TREND FOR HIGHS DURING MID WEEK. TEMPERATURES MAY NOT
GET OUT OF THE LOW 40S IN PORTIONS OF SOUTHERN MICHIGAN ON WEDNESDAY
WHERE CLOUDS WILL PERSIST. CONSISTENT WESTNORTHWEST WINDS OF 5 TO 10
MPH MAY BE THE SAVIOR FROM A HARD FREEZE IN OUR AREA. WILL NEED TO
MONITOR CLOSELY FOR ANY NIGHT WHICH MAY RADIATE OUT...CONSIDERING
HARD FREEZE THRESHOLDS WOULD LIKELY BE MET ACROSS AT LEAST THE
NORTHERN HALF OF THE FORECAST AREA. WILL CONTINUE TO MENTION IN THE
HWO FOR NOW AND MONITOR LATER FORECASTS FOR ANY POTENTIAL HEADLINES.

OTHERWISE...DRY CANADIAN AIR WILL KEEP OUR AREA DRY THROUGH MOST OF
THE PERIOD. DID ADD SLIGHT CHANCE POPS WEDNESDAY NIGHT AS A WEAK
WAVE ROTATES AROUND THE BASE OF THE LARGE SCALE TROUGH. REMOVED
SUPERBLEND POPS OVER THE WEEKEND UNTIL MODELS COME INTO BETTER
AGREEMENT WITH THE EXACT LOCATION/TIMING OF THIS EJECTING WAVE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1232 PM EDT MON APR 20 2015

GRADUAL IMPROVEMENT IN CIGS TO HIGH MVFR/LOW VFR CAN BE EXPECTED
THIS AFTERNOON/EVENING AS POST FRONTAL DRYING/DEEPER MIXING
OVERSPREADS. WESTERLY WINDS WILL BE ON THE STRONG SIDE BOTH THIS
AFTERNOON AND AGAIN TOMORROW UNDER CLOSED LOW IN VICINITY OF THE
NORTHERN GREAT LAKES. THERE MAY BE JUST ENOUGH RESIDUAL BOUNDARY
LAYER MOISTURE AND STEEPENING LOW LEVEL LAPSE RATES TO TOUCH OFF A
FEW SHOWERS THIS AFTERNOON/EVENING...ALTHOUGH COVERAGE/PROBABILITY
REMAIN TOO LOW FOR SHRA INCLUSION ATTM.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 6 PM EDT TUESDAY FOR LMZ043-046.

&&

$$

SYNOPSIS...AGD
SHORT TERM...STEINWEDEL
LONG TERM...BENTLEY
AVIATION...STEINWEDEL


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