618
FXUS63 KLOT 161736
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1236 PM CDT WED OCT 16 2013
.DISCUSSION...
306 AM CDT
COOL AND PERIODICALLY DAMP WEATHER WILL DESCRIBE THE FORECAST PERIOD
AS AN AMPLIFIED AND ACTIVE PATTERN SETS UP. WATER VAPOR SATELLITE
IMAGERY SHOWS A LONGWAVE TROUGH THAT EXTENDS FROM JAMES BAY BACK
ACROSS THE CENTRAL PLAINS TO THE FOUR CORNERS. A LARGE NORTH-SOUTH
RIDGE IS IN PLACE OFF THE WEST COAST WHILE A MORE PROGRESSIVE FLOW
IS FOUND OVER CENTRAL CANADA WHERE ANOTHER TROUGH AXIS IS
TRANSLATING SOUTHEASTWARD. AT THE SURFACE...A LOW IS MOVING
NORTHEAST ACROSS FAR NORTHERN LAKE MICHIGAN WHICH WAS RESPONSIBLE
FOR PUSHING A COLD FRONT ACROSS THE AREA LAST EVENING. A RIBBON OF
HIGH PRESSURE STRETCHES FROM THE PACIFIC NORTHWEST TO THE CENTRAL
HIGH PLAINS.
TODAY...MANY CONCERNS THIS PERIOD RANGING FROM CLOUDS AND STRATUS TO
DRIZZLE. THE UPPER TROUGH EXTENDING FROM JAMES BAY SOUTHWEST HAS A
CLOSED CIRCULATION EMBEDDED WITHIN IT OVER CENTRAL WISCONSIN. THIS
CLOSED CIRCULATION IS EXPECTED TO OPEN UP/WEAKEN WITH THE MAIN
LONGWAVE TROUGH PIVOTING ACROSS THE AREA TODAY. IR SATELLITE SHOWS A
VERY LARGE AREA OF STRATUS SPREADING EASTWARD ACROSS THE LOCAL AREA.
WITH THE UPPER LOW WEAKENING AS IT ARRIVES...UPWARD MOTION WILL BE
DIMINISHING THROUGH THE MORNING AND HAVE SEEN THIS ALREADY OCCURRING
TO THE NORTH WHERE SHOWER COVERAGE/INTENSITY HAS BEEN WANING. WITH
THE EXTENSIVE STRATUS IN PLACE SURFACE WARMING WILL BE LIMITED
LEAVING LOW AND MID LEVEL LAPSE RATES MEAGER. WITH THIS IN MIND
EXPECT THAT THE FOCUS FOR SHOWERS WILL REMAIN NORTH OF THE AREA
LEADING TO LOWER/MINIMAL POPS ACROSS NORTHERN SECTIONS OF THE LOCAL
AREA. WILL GO AHEAD AND ADD DRIZZLE ACROSS NORTHERN AREAS THROUGH
THE MORNING HOWEVER WITH A DECENT DEPTH OF MOISTURE AND SOME WEAK
ASCENT. UPSTREAM OBS OVER THE PAST SEVERAL HOURS HAVE ALSO SHOWN A
FAIR AMOUNT OF DRIZZLE. AS ALLUDED TO...THE STRATUS WILL MAKE TEMPS
A CHALLENGE. STRATUS DOES LOOK TO HOLD ON THROUGH THE AFTERNOON AND
WILL COMBINE WITH LOW LEVEL COLD ADVECTION TO REALLY LIMIT WARMING.
UNLESS SOME BREAKS CAN DEVELOP LATE IN THE DAY ALLOWING SOME MINIMAL
SUNSHINE...DO NOT EXPECT MORE THAN ABOUT A 3-5 DEGREE DIURNAL
INCREASE IN TEMPS FROM MORNING LOW...QUITE A BIT COOLER THAN MOST
GUIDANCE. WILL THEREFORE KEEP HIGHS IN THE LOWER 50S IN NORTHERN
AREAS TO THE MID EVEN UPPER 50S FAR SOUTH...WITH A BETTER CHANCE FOR
SOME SUNSHINE OVER THE EXTREME SOUTHERN PORTIONS OF THE AREA.
TONIGHT THROUGH THURSDAY...ATTENTION TURNS TO THE BASE OF THE
LONGWAVE UPPER TROUGH OVER THE FOUR CORNERS WHERE ANOTHER CLOSED
CIRCULATION IS TAKING SHAPE. THIS LOW WILL EJECT NORTHEASTWARD AND
ACROSS THE AREA THURSDAY MORNING. THIS WILL BRING ANOTHER ROUND OF
SHOWERS TO MUCH OF THE AREA...ESPECIALLY THE SOUTHEAST TWO-THIRDS...
STARTING LATE TONIGHT AND CONTINUING THURSDAY MORNING. TEMPS TONIGHT
WILL BE DEPENDENT ON CLOUD COVER. THE LOW CLOUDS LOOK TO HANG ON
THROUGH THE EVENING IF NOT THROUGH THE NIGHT. MID CLOUDS WILL BE
INCREASING AHEAD OF THE APPROACHING TROUGH OVERNIGHT. WITH SOME
QUESTION ABOUT HOW LONG THE LOW CLOUDS WILL HANG ON AND IF THERE
WILL BE A BREAK IN CLOUD COVER BEFORE THE HIGHER CLOUDS ARRIVE WILL
ONLY RAISE OVERNIGHT LOWS A FEW DEGREES IN MOST AREAS FOR NOW...WITH
POTENTIAL FOR ONLY A RELATIVELY SMALL FALL OVER DAYTIME HIGHS. THE
PASSAGE OF THE UPPER LOW WILL ALLOW CLOUDS TO DECREASE THURSDAY
AFTERNOON WHICH SHOULD ALLOW HIGHS TO WARM SEVERAL DEGREES OVER
TODAY DESPITE SIMILAR MID LEVEL TEMPS.
FRIDAY THROUGH TUESDAY...THE NEXT FEATURE OF INTEREST IS THE TROUGH
MOVING SOUTHEAST ACROSS THE CANADIAN ROCKIES THIS MORNING. PART OF
THIS WAVE LOOKS TO SPLIT OFF AND MOVE DUE SOUTH INTO THE CENTRAL
ROCKIES WHILE THE REST TRACKS SOUTHEAST ACROSS THE NORTHERN PLAINS
AND UPPER MISSISSIPPI RIVER VALLEY. ALL OF THIS ENERGY WILL RESULT
IN A NEW LONGWAVE TROUGH RIGHT ACROSS THE MID SECTION OF THE
COUNTRY. A WAVE WILL THEN ZIP NORTHEAST ACROSS THE AREA FRIDAY
EVENING/NIGHT BRINGING A LOW CHANCE FOR POPS ACROSS THE
AREA...ESPECIALLY SOUTHEAST. THE LONGWAVE WILL SHIFT EASTWARD
SATURDAY INTO SUNDAY WHICH WILL ALLOW EVEN COLDER MID LEVEL AIR TO
SPREAD INTO THE AREA...WITH H85 TEMPS FALLING BELOW 0C. PRECIP
CHANCES LOOK LESS COHERENT BUT OVERALL MINIMAL SATURDAY AND
SUNDAY...THOUGH LAKE EFFECT SHOWERS LOOK TO BE IN FULL SWING EAST OF
LAKE MICHIGAN. HIGHS WILL BE IN THE 50S SATURDAY AND SUNDAY.
ADDITIONAL ENERGY WILL TRACK SOUTHEAST ACROSS CENTRAL CANADA INTO
THE UPPER MIDWEST AND WESTERN GREAT LAKES LATER SUNDAY THROUGH
TUESDAY. THIS WILL LEAD TO ADDITIONAL PRECIP CHANCES AND CONTINUED
COOL TEMPERATURES BUT THE DETAILS ARE UNCLEAR AT THIS RANGE.
MDB
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* LOWER END MVFR STRATUS DECK.
* POTENTIAL FOR PATCHY DRIZZLE THROUGH THIS AFTERNOON.
* CHANCE OF SHOWERS TOMORROW MORNING.
KREIN
//DISCUSSION...UPDATED 18Z...
MAIN ISSUE FOR THE REMAINDER OF THE AFTERNOON AND THROUGH MUCH OF
THE NIGHT WILL CONTINUE TO BE CIGS. LATEST SATELLITE IMAGERY
INDICATES A WIDESPREAD AREA OF STRATUS UNDER AN UPPER TROUGH...IN
THE WAKE OF AN EXITING UPPER LOW MOVING OFF TO THE NORTHEAST.
WHILE THERE ARE A FEW ISOLD AREAS OF IFR CIGS...THE GREATER
PORTION OF THE ST DECK IS AT THE LOWER END OF MVFR. WHILE THERE IS
A CHANCE FOR SOME IFR CIGS TO SNEAK INTO THE TERMINALS...RFD WOULD
BE THE MOST LIKELY LOCATION AND ONLY FOR A BRIEF TIME AS THE UPPER
TROUGH AXIS IS OVERHEAD. OTHERWISE...EXPECT A SLOW RECOVERY OF
CIGS...AND DO NOT ANTICIPATE IMPROVEMENT TO VFR UNTIL TOMORROW
MORNING. SINCE THE SATURATED LAYER IS RELATIVELY SHALLOW...THERE
WILL STILL BE A CHANCE FOR SOME SCT SPRINKLES OR DRIZZLE THROUGH
THE AFTERNOON AND INTO THE EVENING...BUT DO NOT ANTICIPATE A
PREVAILING PCPN CONDITION OR SGFNT REDUCTION IN VIS DUE TO
PCPN...OR BR AS DEWPOINTS WILL TREND LOWER THROUGH THE PERIOD AS
WELL. THERE WILL BE ANOTHER CHANCE FOR SOME SHOWERS TOMORROW AS
ANOTHER UPPER LEVEL WAVES TRACKS ACROSS THE MIDWEST...BUT THE
LATEST GUIDANCE SUGGESTS THAT THE TRACK OF THIS FEATURE WILL BE
CLOSER TO CNTRL IL/NRN INDIANA. THIS WOULD SUGGEST THAT THE
GREATEST CHANCES FOR PCPN WILL BE SOUTH AND EAST OF THE
TERMINALS...SO WILL ONLY INCLUDE A VCSH MENTION FOR PCPN AT THIS
TIME.
KREIN
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* HIGH CONFIDENCE IN MVFR CIGS THROUGH THE REST OF THIS AFTERNOON
AND THROUGH TONIGHT. CHANCES THAT CIGS WILL DROP TO IFR ARE
LOW...BUT NOT TOTALLY OUT OF THE QUESTION...ESPECIALLY THIS
AFTERNOON.
* MODERATE CONFIDENCE IN TIMING OF CIGS IMPROVING TO VFR TOMORROW
MORNING.
* MODERATE CONFIDENCE THAT THERE WILL BE LITTLE OR NO IMPACT FROM
PCPN ON THE TERMINALS.
KREIN
//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...
THURSDAY NIGHT...VFR.
FRIDAY...VFR.
SATURDAY...SLT CHC SHRA.
SUNDAY...VFR.
MONDAY...CHC SHRA.
TUESDAY...SLT CHC SHRA.
BMD
&&
.MARINE...
258 AM CDT
LOW PRESSURE LIES OVER NORTHERN LAKE MICHIGAN THIS MORNING WITH A
TRAILING COLD FRONT STRETCHING WEST ACROSS WISCONSIN INTO IOWA.
WINDS ARE STRONGEST ACROSS THE SOUTHERN HALF OF THE LAKE WHERE 30
KTS ARE EXPECTED TO CONTINUE...THEN SHOULD BEGIN TO TAPER THIS
AFTERNOON. A SMALL CRAFT ADVISORY WILL BE HOISTED FOR THE INDIANA
NEARSHORE WATERS EAST OF BURNS HARBOR THROUGH LATE THIS EVENING.
STRONGER WINDS ARE EXPECTED LATE THIS MORNING AND EARLY AFTERNOON
ACROSS THE NORTHERN HALF OF THE LAKE AS THE COLD FRONT PUSHES ACROSS
ALLOWING WINDS TO INCREASE WITH 30 KT GUSTS EXPECTED. WINDS WILL
TAPER ACROSS THE ENTIRE LATE TONIGHT AS ANOTHER TROUGH DROPS INTO
THE WESTERN LAKES REGION ALLOWING THE GRADIENT TO WEAKEN. WINDS
BEGIN TO INCREASE AGAIN ON SATURDAY AS ANOTHER LOW DROPS SOUTHEAST
ACROSS THE CANADIAN PRAIRIES THEN PIVOTS EAST ACROSS THE NORTHERN
LAKES REGION.
BMD
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE BURNS HARBOR TO MICHIGAN CITY IN UNTIL 10 PM WEDNESDAY.
&&
$$
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