Area Forecast Discussion
Issued by NWS Chicago, IL

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 KLOT 231145
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
545 AM CST SUN NOV 23 2014

.SHORT TERM...
312 AM CST

THROUGH TONIGHT

WHAT A DIFFERENCE 48 HOURS MAKES! BRISK SOUTHERLY WINDS ARE
TRANSPORTING AN UNSEASONABLY MILD AND MOIST AIR MASS INTO THE REGION
WITH OVERNIGHT TEMPS IN THE UPPER 40S/LOWER 50S. COMPLEX PATTERN
ALOFT WITH STRONG CLOSED MID LEVEL LOW TRACKING EASTWARD JUST NORTH
OF THE CANADIAN BORDER WHILE A POWERFUL PACIFIC JET NOSES INTO THE
SOUTHERN ROCKIES AT THE BASE OF A STRONG SOUTHERN STREAM SHORTWAVE.

IN THE NEAR TERM...MORE SUBTLE SHORTWAVE EVIDENT ON WATER VAPOR
IMAGERY OVER NE OK/SE KS TRACKING NORTHEASTWARD HAS RESULTED IN A
RECENT BLOSSOMING OF RAIN OVER NORTHERN MISSOURI. SHORT RANGE
GUIDANCE AGREES THAT AS THE SHORTWAVE CONTINUES NE THIS MORNING THAT
THIS AREA OF RAIN WILL DEVELOP EASTWARD WHILE MOVE NORTHEAST AND
SPREAD INTO MAINLY WESTERN AND NORTHERN PORTIONS OF OUR CWA. THIS
RAIN SHOULD LIFT NORTH THROUGH THE MORNING AND AS IT LOOKS NOW THERE
WILL BE A SEVERAL HOUR LONG BREAK IN THE RAIN OVER MUCH OF THE AREA
THIS AFTERNOON IN THE WAKE OF THIS SHORTWAVE AND PRIOR TO THE
HEAVIER AND MORE WIDESPREAD RAIN ASSOCIATED WITH THE STRENGTHENING
SOUTHERN STREAM SHORTWAVE SPREADS ACROSS THE CWA LATE THIS AFTERNOON
AND ESPECIALLY THIS EVENING. HIGH PWATS AND STRONG FORCING SHOULD
RESULT IN HEALTHY RAINFALL TOTALS AND PERIODIC MODERATE TO NEARLY
HEAVY RAIN WITHIN THE WARM CONVEYOR BELT THIS EVENING. STILL LOOKS
LIKELY THAT MOST OF THE AREA WILL PICK UP IN THE NEIGHBORHOOD OF AN
INCH OF RAIN THIS AFTERNOON INTO TONIGHT.

STEADY STREAM OF MID-UPPER 40 DEWPOINTS ADVECTING NORTH INTO THE
AREA SHOULD ALLOW TEMPS TO FALL VERY LITTLE EARLY THIS MORNING.
WHILE CLOUD COVER WILL BE EXTENSIVE TODAY...THE ANTICIPATE BREAK IN
THE PRECIP SHOULD BE ENOUGH TO ALLOW TEMPS TO INCH UP INTO THE
MID-UPPER 50S ACROSS THE MAJORITY OF THE CWA...ONE EXCEPTION
POTENTIALLY BEING FAR NORTHWEST WHERE RAIN COULD LINGER LONGER INTO
MIDDAY. TONGUE OF 50 DEGREE DEWPOINTS SHOULD POKE UP INTO THE AREA
TONIGHT AHEAD OF THE STRONG COLD FRONT AND ANTICIPATE TEMPS TONIGHT
TO HOLD IN THE 50S WITH THE RAIN THE MAJORITY OF THE NIGHT WITH LOWS
OCCURRING JUST PAST SUNRISE.

IZZI

&&

.LONG TERM...
312 AM CST

MONDAY ONWARD...

STILL SEEING SOME NON-TRIVIAL DIFFERENCES IN THE MODELS WITH RESPECT
TO THE DETAILS MONDAY...LIKELY DUE TO THEIR TENDENCY TO STRUGGLE
WITH PHASING SYSTEMS. ALL GUIDANCE SWEEPS A STRONG COLD FRONT ACROSS
THE AREA MONDAY MORNING WITH FALLING TEMPERATURES AND STRONG
WESTERLY WINDS LIKELY MONDAY INTO MONDAY EVENING. THE BIGGEST
DIFFERENCE IN THE SOLUTIONS FOR OUR AREA IS AN INCREASING LARGE CAMP
OF MODEL GUIDANCE IS SHOWING A FAIRLY STRONG NORTHERN STREAM
SHORTWAVE LAGGING BEHIND AND ENHANCING ASCENT IN THE DEFORMATION
ZONE ACROSS OUR CWA MONDAY AFTERNOON AND EVENING. BY THIS POINT
THERMAL PROFILES WOULD SUPPORT ALL SNOW. LATEST GFS/ECMWF/PARALLEL
13KM GFS ALL SHOWING AN ACCUMULATING SNOWFALL ACROSS OUR CWA MONDAY
AFTERNOON AND EVENING...ESPECIALLY NORTHERN 1/2 TO 2/3 OF THE AREA.
THE LACK OF RUN-TO-RUN CONSISTENCY AND KNOWN ISSUES GUIDANCE HAS
WITH PHASING SYSTEMS LEADS TO LOWER THAN AVERAGE CONFIDENCE BUT HAVE
BUMPED UP POPS TO LIKELY IN THIS TIME FRAME AND CARRIED A COUPLE
INCHES OF ACCUMULATION IN THE GRIDS FOR THIS TIME FRAME.

IF THE LATEST GFS/ECMWF QPF ENDS UP BEING IN THE BALL PARK OF WHAT
HAPPENS THEN WE COULD BE LOOKING AT A FAIRLY HIGH IMPACT EVENT WITH
SEVERAL INCHES OF ACCUMULATION POSSIBLE. IN ADDITION...VERY STRONG
WINDS WILL FURTHER RESULT IN A FURTHER DETERIORATION IN CONDITIONS.
FORECAST SOUNDINGS DON`T FAVOR HIGH SNOW:LIQUID RATIO SNOWFALL WITH
DEEP ISOTHERMAL LAYER WARMER THAN -10C...RATHER LARGER AGGREGATE
FLAKES WOULD BE FAVORED WITH A WETTER SNOW AND LOWER VSBYS. WILL
BEGIN TO ADVERTISE THIS THREAT IN THE HWO BUT FAR TOO EARLY TO
CONSIDER ANY HEADLINES AT THIS POINT.

YET ANOTHER SURGE OF ARCTIC AIR SPILLS INTO THE REGION TUESDAY IN
THE WAKE OF THIS SYSTEM. FAST ON ITS HEELS OF THIS SYSTEM LOOKS TO
BE A FAIRLY ENERGETIC CLIPPER DIVING INTO THE REGION WEDNESDAY. THE
00Z GFS HAS BACKED OFF ON THE INTENSITY OF THIS WAVE...WHILE THE
ECMWF HAS TRENDED STRONGER AND LOOKS MORE IN LINE WITH THE 84 HOUR
WRF-NAM. IN ADDITION...THE 13KM PARALLEL GFS IS MORE IN THE STRONGER
NAM/ECMWF CAMP SO FELT COMFORTABLE RAISING POPS ABOVE THE SUPERBLEND
INITIALIZATION AS POTENTIAL LOOKS TO BE GROWING FOR A HIGHER
PROBABILITY/LOWER QPF SNOW EVENT IN THE REGION WEDNESDAY. IT SHOULD
COME AS NO SURPRISE THAT MORE ARCTIC LOOKS TO SPILL INTO THE REGION
BEHIND THIS SYSTEM IN TIME FOR THE THANKSGIVING HOLIDAY WEEKEND.

IZZI

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* CIGS RETURNING TO MVFR THIS MORNING WITH AT LEAST VICINTY
  SHOWERS.

* ANOTHER ROUND OF STEADY RAIN BEGINNING MID TO LATE AFTERNOON AND
  CONTINUING THROUGH THE EVENING. IFR CIGS AND VSBYS EXPECTED.
  LIGHTER RAIN OR DRIZZLE OVERNIGHT WITH IFR CONDITIONS
  CONTINUING.

* SOUTHEAST WINDS GREATER THAN 10 KT THIS AFTERNOON.

* GUSTY SOUTHWEST TO WEST WINDS AT THE END OF THE CURRENT TAF PERIOD.

* TRANSITION FROM RAIN TO SNOW AT THE END OF THE ORD 30 HR TAF.

KMD

//DISCUSSION...UPDATED 12Z...

CIGS ARE LIFTING TO VFR BRIEFLY EXCEPT IN THE FAR NORTHWEST NEAR
KRFD. NEXT BATCH OF SHOWERS WILL WORK NORTHWARD IN THE COMING
HOURS WITH A RETURN TO MVFR IN MOST LOCATIONS THROUGH THE MORNING.
AFTER A LULL IN ACTIVITY MIDDAY...MORE WIDESPREAD RAIN WITH
IFR/LIFR CIGS AND VSBYS WILL SPREAD OVER THE REGION BY MID
AFTERNOON AND CONTINUING THROUGH THE EARLY EVENING HOURS. WINDS
WILL SHIFT FROM SOUTHERLY TO SOUTHEASTERLY DURING THIS TIME FRAME
WHILE HOLDING AROUND 10 KT OR SO. EXPECT A SHIFT BACK TO
SOUTHERLY TONIGHT AND EVENTUALLY WESTERLY BY LATE TONIGHT/EARLY
MONDAY.


EXPECT A QUICK TRANSITION TO GUSTY COLD WESTERLY WINDS EARLY
MONDDAY WIH RAIN TRANSITIONING A MIX SOMETIME DURING THE MID-LATE
MORNING TIMEFRAME.

KMD


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH ON CONDITIONS RETURNING TO MVFR...MEDIUM ON TIMING AND IF
  ANY SHOWERS WILL OCCUR AT THE TERMINALS THIS MORNING.

* HIGH ON A PERIOD OF AT LEAST MODERATE RAIN THIS AFTERNOON AND
  EVENING WITH IFR/LIFR CONDITIONS. MEDIUM-HIGH ON TIMING AND MEDIUM
  FOR THE IFR ONSET.

* HIGH FOR WIND TRENDS BUT MEDIUM ON SPEEDS.

* HIGH THAT RAIN WILL TRANSITION TO AT LEAST A RAIN SNOW MIX
  SOMETIME MONDAY MORNING...MEDIUM ON TIMING.


KMD

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...
252 AM CST

LOW PRESSURE MOVING EAST FROM THE CANADIAN PRAIRIES EARLY THIS
MORNING WILL CONTINUE TO FILL AS IT TRACKS ALONG THE CANADIAN BORDER
TODAY AND REACHES LAKE SUPERIOR LATE THIS AFTERNOON. THIS LOW WILL
MERGE WITH LOW PRESSURE CURRENTLY EMERGING OUT OF THE SOUTHERN HIGH
PLAINS REGION. THE HIGH PLAINS LOW WILL ABSORB THE NORTHERN LOW OVER
LAKE MICHIGAN TONIGHT THEN CONTINUE TO DEEPEN AS IT TRACKS OVER/EAST
OF LAKE MICHIGAN MONDAY MORNING...THEN DEEPENS MORE MONDAY NIGHT AS
IT CONTINUES EAST OF JAMES BAY.  HAVE NOT MADE CHANGES TO THE
HEADLINES AT THIS MOMENT. CONFIDENCE ON GALES FOR THE SOUTHERN HALF
OF THE LAKE IS HIGH THOUGH STILL SOME ISSUES WITH TIMING. IT LOOKS
LIKE GALES BEGIN TO SPREAD OVER THE SOUTHERN TIP OF THE LAKE NEAR OR
SHORTLY AFTER DAYBREAK MONDAY.  CONFIDENCE FOR GALES ON THE NORTH
HALF OF THE LAKE IS A BIT LESS BUT STILL MEDIUM-HIGH GIVEN
DIFFERENCES IN HOW QUICKLY MODELS MOVE THE LOW OVER THE LAKE MONDAY
INTO MONDAY NIGHT. DEPENDING ON HOW QUICKLY THE LOW KICKS
NORTHEAST...THE GALE WATCH END TIME FOR THE FAR NORTHERN PORTION OF
THE LAKE MAY BE A BIT TOO SHORT. WEAK HIGH PRESSSURE PASSES OVER THE
LAKE TUESDAY. THIS WILL BE FOLLOWED ON WEDNESDAY ON A CLIPPER-TYPE
LOW COMING OUT OF THE DAKOTAS TUESDAY. THIS LOW PUSHES EAST OF THE
LAKE WEDNESDAY NIGHT AS STRONGER HIGH PRESSURE BUILDS IN TO THE
CENTER OF THE COUNTRY THURSDAY AND LINGERS FOR A FEW DAYS. KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM SUNDAY.

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




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