Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 250903
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
303 AM CST TUE NOV 25 2014

.SHORT TERM...
303 AM CST

THROUGH WEDNESDAY...

PRIMARY FORECAST CHALLENGE TODAY IS CLOUD COVER. GUIDANCE IS ALL
FAIRLY AGGRESSIVE IS CLEARING THINGS OUT THIS AFTERNOON SAVE FOR THE
WRF-NAM. MODELS ARE OFTEN TOO QUICK TO CLEAR STRATUS OUT IN THE
WINTER...THOUGH IN THIS CASE IT IS A FAIRLY TRANSIENT PATTERN SO
STRATUS MAY BE A BIT QUICKER TO CLEAR THAN IS TYPICAL. MOS GUIDANCE
KEEPS SKIES FAIRLY CLOUDY AND HAVE MAINTAINED CLOUDINESS LONGER THAN
GUIDANCE SUGGESTS BUT DO PARTIALLY CLEAR SKIES OUT TONIGHT FOR A
TIME BEFORE CLOUDS ROLL BACK IN AHEAD OF THE NEXT SYSTEM.

SPEAKING OF THE NEXT SYSTEM...GUIDANCE CONTINUES TO TAKE THE CLIPPER
ON THE SOUTHERN ROUTE WITH ITS PRECIP LARGELY MISSING OUR CWA. HAVE
MAINTAINED SOME SLIGHT CHANCE POPS IN OUR SOUTHWESTERN MOST CWA
WEDNESDAY BUT OTHERWISE CONTINUED THE TREND FROM THE DAY SHIFT OF
LOWERING POPS...COMPLETELY REMOVING THEM FROM MUCH OF THE CWA.

IZZI

&&

.LONG TERM...
303 AM CST

WEDNESDAY NIGHT ONWARD...

IN THE LONGER TERM GUIDANCE IS STILL BRINGS IN A TRANSIENT BUT
MODERATELY POTENT SHOT OF COLD AIR THANKSGIVING DAY WHEN HIGHS
SHOULD ONCE AGAIN HOLD IN THE 20S. LARGE SCALE PATTERN WILL BEGIN TO
TRANSITION TO MORE OF A ZONAL FLOW BY FRIDAY WITH WARM AIR ADVECTION
BEGINNING AND POSSIBLY PRODUCING A BIT OF LIGHT PRECIP...BUT IF
ANYTHING DOES FALL AMOUNTS LOOK TO BE VERY LIGHT. BY SATURDAY STRONG
LOW PRESSURE IS PROGGED TO TRACK EAST INTO THE UPPER GREAT LAKES
ALLOWING FOR A BRISK BUT MILD SOUTHERLY FLOW TO DEVELOP OVER THE
AREA. FORECAST 850MB TEMPS WOULD SUPPORT HIGHS WELL INTO THE 50S AND
PERHAPS NEAR 60...THOUGH 925MB TEMPS ARE NOT QUITE AS MILD AND THAT
COULD PARTIALLY BE A RESULT OF A BIT MORE SNOW COVER. HAVE RAISED
HIGHS A BIT OVER THE BLENDED INITIALIZATION BUT THINKING CURRENT
FORECAST IS STILL TOO COOL...ESPECIALLY IN AREAS WITH LITTLE OR NO
SNOW COVER WHICH SHOULD BE A LARGE PORTION OF THE CWA BY SATURDAY.
COLD FRONT LOOKS TO MOVE THROUGH SAT NIGHT OR SUNDAY BRINGING COOLER
WEATHER FOR A COUPLE DAYS BUT IN THE TRANSIENT RATHER ZONAL FLOW GFS
AND ECMWF BOTH HINT AT ANOTHER HEALTHY WARM UP TOWARD MIDDLE OF NEXT
WEEK. PRECIP CHANCES THROUGH THE PERIOD LOOK LOW AND LARGELY
INCONSEQUENTIAL IF ANYTHING DOES FALL.

IZZI

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* PERSISTENT SCATTERED LIGHT SNOW SHOWERS...BUT REMAINING VFR.

* POTENTIAL FOR A STRONGER SNOW SHOWER EARLY THIS FORECAST
  PERIOD...WITH POSSIBLE IFR VIS.

* MVFR CEILINGS THROUGH LATE MORNING.

RODRIGUEZ

//DISCUSSION...UPDATED 06Z...

LATEST RADAR IMAGERY SHOWING SNOW SHOWERS PERSISTING AROUND THE
TERMINALS THIS HOUR...BUT WITH NO REAL VIS RESTRICTION. THESE SNOW
SHOWERS AND VIS TRENDS WILL CONTINUE EARLY THIS MORNING BUT WITH
THE POSSIBILITY FOR A BRIER HEAVIER SNOW SHOWER EARLY...POSSIBLY
PROVIDING IFR VIS. HAVE MAINTAINED TEMPO GROUP WITH 2SM VIS BUT
DID PUSH IT BACK AN HOUR BASED ON LATEST TRENDS. ANY SNOW WILL
LIKELY COME TO AN END LATER THIS MORNING WHILE MVFR CEILINGS
SLOWLY LIFT TO VFR BY LATE MORNING...WITH VFR CEILINGS THEN
LINGERING INTO THE AFTERNOON. AS HIGH PRESSURE BUILDS ACROSS THE
REGION THIS AFTERNOON SHOULD SEE THESE CLOUDS SCATTER...WITH ONLY
HIGH LEVEL CLOUD THEN ANTICIPATED THROUGH THE REST OF THE FORECAST
PERIOD. THE STRONGER WESTERLY WINDS ARE CURRENTLY
DIMINISHING...WITH THIS TREND CONTINUING THROUGH THE REST OF THE
MORNING BUT WHILE STAYING WESTERLY.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE WITH SCATTERED LIGHT SNOW SHOWERS.

* MEDIUM CONFIDENCE WITH ANY STRONGER SNOW SHOWERS EARLY.

* HIGH CONFIDENCE WITH MVFR CEILINGS...LOW MEDIUM CONFIDENCE WITH
  DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SOUTH WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

MDB

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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