🚀 go-pugleaf

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1210 PM CST SUN MAR 3 2013

DISCUSSION...
243 AM CST

ANOTHER SHIFT...ANOTHER POTENTIAL SNOW STORM...SURE SEEMS LIKE OLD
MAN WINTER IS DOING ALL HE CAN TO GET THE SNOW FALL IN THAT HE
SPARED US THE FIRST 2/3 OF WINTER! PRIMARY FORECAST CONCERN THIS
MORNING IS CERTAINLY THE SNOW SYSTEM SLATED TO AFFECT THE
REGION...PRIMARILY ON TUESDAY.

BEFORE THE SNOW...LOOKS LIKE THE REGION WILL GET A GENERALLY SUNNY
BUT SOMEWHAT CHILLY DAY TODAY...ESPECIALLY THIS MORNING OVER THE
DEEPER SNOWPACK. DESPITE THE BITTERLY COLD START TO THE MORNING
ANTICIPATE THE STRONG MARCH SUN TO ALLOW TEMPS TO RAPIDLY RISE FROM
MORNING LOW...WITH HIGHS POTENTIALLY PUSHING THE 40F MARK SE
COUNTIES RANGING DOWN TO NEAR FREEZING NORTHERN CWA OVER THE DEEP
SNOW COVER.

BY TONIGHT CLOUDINESS WILL BE ON THE INCREASE ACROSS MAINLY WESTERN
PORTIONS OF THE CWA...WHICH SHOULD HELP KEEP TEMPS FROM DROPPING AS
PRECIPITOUSLY AS THEY DID SATURDAY EVENING. FARTHER WEST...VIGOROUS
CLOSED LOW WILL RIDE THE NW FLOW INTO THE NORTHERN HIGH PLAINS WITH
STRENGTHENING WARM AIR ADVECTION AND TIGHTENING BAROCLINIC ZONE
RESULTING IN NW TO SE BAND OF SNOW DEVELOPING TO THE WEST AND
NORTHWEST OF OUR CWA. EASTWARD PROGRESSION OF THIS BAND IS PROGGED
TO BE LIMITED AS NARROW UPPER RIDGE THAT IS SANDWICHED BETWEEN
NEARLY STATIONARY DEEP LOW OFF THE NORTHEAST CONUS AND UPPER LOW
DIGGING SOUTHEASTWARD ACROSS THE HIGH PLAINS.

MODELS GENERALLY SUGGEST THAT LEAD SHORTWAVE WILL DAMPEN AS IT
ENCOUNTERS THE UPPER RIDGE WITH WEAKENING FORCING ALLOWING FOR A
DECREASE IN THE INTENSITY OF THE BAND OF SNOW AS IT TRIES TO SPREAD
EAST INTO OUR CWA MONDAY. HAVE MAINTAINED FAIRLY TIGHT WEST TO EAST
POP GRADIENT ACROSS THE CWA WITH BEST CHANCES FOR MEASURABLE SNOW
ACROSS FAR WEST AND SOUTHWEST CWA.

BY MONDAY NIGHT INTO TUESDAY THE SPREAD IN THE MODEL SOLUTIONS GROWS
QUITE LARGE WITH UKMET/GEM FARTHEST SOUTHWEST AND WRF-NAM...SREF...
AND OTHER HIGH-RES WRF`S FARTHEST NORTHEAST WITH TRACK OF THE
SYSTEM. ECMWF IS CLOSER TO THE UKMET/GEM SOLUTION WITH GFS IN THE
MIDDLE BUT CLOSER TO THE NORTHERN CLUSTER OF MODEL GUIDANCE.
UNFORTUNATELY THE SPREAD IN MODEL GUIDANCE IS LARGE ENOUGH THAT THE
NORTHERN CLUSTER WOULD MEAN HEAVIEST SNOW MISSES OUR CWA TO THE
NORTHEAST...WHILE THE SOUTHERN CLUSTER WOULD MEAN HEAVIEST SNOW
MISSES US TO THE SOUTHWEST. GIVEN THE PROGGED INTENSITY OF THE
SYSTEM AND FORECASTED AVAILABLE MOISTURE WOULD SEEM LIKELY THAT THIS
SYSTEM WILL LAY DOWN A SWATH OF HEAVY SNOW (6"+) SOMEWHERE IN THE
NEIGHBORHOOD WITH OUR CWA CERTAINLY WELL WITHIN THE LINE OF FIRE.
SINCE THE HEAVIEST SNOW WOULD LIKELY FALL 5TH PERIOD BEYOND THE
TYPICAL 48 HOURS WATCH WINDOW HAVE OPTED TO HOLD OFF ON A WATCH
AND HIGHLIGHT THE THREAT WITH AN SPS. HOPEFULLY 12Z GUIDANCE WILL
COME INTO BETTER AGREEMENT AND ALLOW THE DAY SHIFT TO BETTER
DEFINE THE AREAL SCOPE OF THE THREAT AND CONSIDER A WINTER STORM
WATCH LATER THIS AFTERNOON.

NO REAL SIGNIFICANT PUSH OF COLD AIR BEHIND THE SYSTEM WITH JUST A
CONTINUED MODERATE COLD EXPECTED WEDNESDAY BEFORE BIG WARMING TREND
COMMENCES FOR LATER IN THE WEEK. MEDIUM RANGE GUIDANCE CONTINUES TO
POP A HEALTHY UPPER RIDGE OVER THE REGION AS UPPER TROUGH DIGS INTO
THE WEST. SNOW COVER COULD REALLY MUCK UP OUR POTENTIAL WARM
UP...ESPECIALLY IF THE MORE SOUTHERLY SOLUTIONS PAN OUT AND
BLANKETS AREAS TO OUR SOUTH AND SOUTHWEST WITH A HEALTHY SNOW
PACK. IN THE ABSENCE OF SNOW COVER...POTENTIAL WOULD BE THERE FOR
HIGHS TO GET WELL INTO THE 50S BY FRIDAY...BUT GIVEN THE
UNCERTAINTY WITH RESPECT TO SNOW COVER HAVE OPTED TO CONTINUE
CONSERVATIVE WITH HIGH TEMPS THUR-SAT.

IZZI

&&

AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* NO CONCERNS IN THE NEAR TERM.

* VFR CEILINGS RETURN LATE TONIGHT...WITH POSSIBLE MVFR CONDITIONS
  IN LIGHT SNOW LATE IN THE FORECAST PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

WITH A RIDGE OF HIGH PRESSURE STRETCHED ACROSS THE REGION
TODAY...QUIET/VFR CONDITIONS WITH LIGHT WINDS IN PLACE OVER THE
TERMINALS. THIS HIGH WILL SLOWLY DRIFT TO THE EAST THIS
EVENING...BUT WITH ONLY PASSING HIGH LEVEL CLOUD COVER AND A
CONTINUED LIGHT NORTHERLY WIND EXPECTED. WINDS WILL DROP OFF LATER
TONIGHT...WITH THE POSSIBILITY OF SOME REMAINING LAKE EFFECT CLOUD
COVER OVER THE LAKE TO PUSH BACK WESTWARD OVERNIGHT. ALTHOUGH IF
THIS WERE TO OCCUR...DONT EXPECT MUCH IN TERMS OF ANY CEILINGS.
WITH THE APPROACH OF THE NEXT SYSTEM...MID/HIGH LEVEL CLOUD COVER
WILL STREAM OVERHEAD TONIGHT INTO MONDAY MORNING. AS WINDS
INCREASE OUT OF THE EAST/SOUTHEAST...A DOWNWARD TREND IN CEILINGS
IS THEN EXPECTED DURING THE DAY BUT REMAINING VFR. ITS NOT UNTIL
THE EARLY AFTERNOON THAT A BRIEF PERIOD OF LIGHT SNOW COULD REACH
THE TERMINALS. AS THIS OCCURS...MVFR CONDITIONS WILL BE POSSIBLE
THROUGH THE END OF THE FORECAST PERIOD. RFD WILL LIKELY OBSERVE
THIS LIGHT SNOW AND CONDITIONS BY MID MORNING.

RODRIGUEZ


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH TONIGHT.

* LOW MEDIUM CONFIDENCE WITH POSSIBLE MVFR CONDITIONS/LIGHT SNOW
  MONDAY AFTERNOON.

RODRIGUEZ

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

MONDAY NIGHT...CHC OF SNOW. CIGS DROPPING TO MVFR/IFR.
TUESDAY...HEAVY SNOW POSSIBLE. IFR LIKELY.
WEDNESDAY THROUGH THURSDAY...MVFR.
FRIDAY...VFR.
SATURDAY...SLT CHC RAIN.

BMD

&&

MARINE...
258 AM CST

HIGH PRESSURE WILL BEGIN TO BUILD ACROSS LAKE MICHIGAN TODAY WITH
WINDS AND WAVES TRENDING DOWN THROUGH TONIGHT. ONCE THE RIDGE AXIS
PASSES OVER THE LAKE LATE TONIGHT...WINDS WILL BEGIN TO TURN
EAST/SOUTHEASTERLY AS OUR NEXT AREA OF LOW PRESSURE TAKES SHAPE
ACROSS THE SOUTHERN PLAINS. THIS LOW WILL LIFT NORTHEAST ACROSS THE
MID MISSISSIPPI VALLEY MONDAY NIGHT...THEN TRAVEL EAST ALONG THE
OHIO RIVER VALLEY TUESDAY. A MODERATE GRADIENT WILL DEVELOP OVER THE
LAKE...STRONGEST AT THE SOUTHERN END WHERE WINDS ARE EXPECTED TO
INCREASE TO AROUND 30 KT TUESDAY AND TUESDAY NIGHT. HIGH PRESSURE
WILL THEN BEGIN TO BUILD IN AGAIN FROM THE NORTHWEST...WITH RIDGING
PASSING OVER THE LAKE ON THURSDAY. NO GALES ARE IN THE FORECAST FOR
THE NEXT WEEK...THOUGH WILL HAVE TO MONITOR CONDITIONS FOR TUESDAY.

BMD

&&

LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 10 PM SUNDA
Y.

     SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 2 PM
     SUNDAY.

&&

$$