🚀 go-pugleaf

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1133 AM CST FRI FEB 15 2013

DISCUSSION...
1026 AM CST

FOR MORNING UPDATE...

AREA OF FLURRIES/LIGHT SNOW SHOWERS WAS EXITING THE SOUTHEAST PART
OF THE CWA THIS MID-MORNING...IN ASSOCIATION WITH WEAK FORCING
PROVIDED BY A MID-LEVEL SHORT WAVE OVER THE WESTERN LAKES. SKIES
HAVE BECOME MOSTLY SUNNY ACROSS MUCH OF THE CWA IN THE WAKE OF THIS
WAVE WITH ASSOCIATED DRY LOW-LEVEL ADVECTION. ANOTHER WEAK MID-LEVEL
TROUGH WAS EVIDENT IN WATER VAPOR/IR IMAGERY OVER WI/NORTHEAST
IA...THOUGH THIS WAS ONLY PRODUCING SOME PATCHY MID CLOUDS IN THE
DRY AIR MASS. THIS SHOULD SPREAD SOUTHEAST ACROSS OUR AREA THIS
AFTERNOON...WITH DEEPENING OF STEEP LOW LEVEL BOUNDARY LAYER LAPSE
RATES PER 12Z WRF-NAM FORECAST SOUNDINGS SUGGESTING THE POTENTIAL
FOR THE DEVELOPMENT OF LOWER STRATOCU DECK BY LATE AFTERNOON.
THEREFORE...WHILE A PERIOD OF PARTLY CLOUDY SKIES SHOULD PREVAIL
THROUGH EARLY AFTERNOON...IT APPEARS REASONABLE TO EXPECT SOME
INCREASE IN CLOUDS FROM THE NORTHWEST THIS AFTERNOON. WHILE THERE IS
NOT MUCH IN THE WAY OF FORCING...COOLING OF THE LOW LEVELS DOES
RESULT IN POTENTIAL STRATOCU DEVELOPMENT OCCURRING IN A FAVORABLE
THERMAL RANGE FOR CRYSTAL DEVELOPMENT AND WILL MAINTAIN A MENTION OF
A CHANCE OF FLURRIES...BUT NOT UNTIL LATER THIS AFTERNOON/EVENING.

WITH MORE SUNSHINE THAN PREVIOUSLY ANTICIPATED...HAVE BUMPED TEMPS A
DEGREE OR SO IN SOME AREAS...ESPECIALLY ACROSS THE SOUTH WHERE
MORNING TEMPS HAVE STARTED OUT IN THE MID 30S. OTHERWISE...
PERSISTENT COLD ADVECTION SHOULD KEEP TEMPS FROM WARMING TOO MUCH
DESPITE THE MID-FEBRUARY SUNSHINE.

RATZER

//PREV DISCUSSION...
303 AM CST

WATER VAPOR IMAGERY EARLY THIS MORNING SHOWS A DECENT SHORT WAVE
DISTURBANCES DROPPING EAST-SOUTHEAST ACROSS MISSOURI AND ILLINOIS.
THIS FEATURE CONTINUES TO PRODUCE SOME LIGHT SNOW SHOWERS AND
FLURRIES ACROSS PORTIONS OF THE AREA. HOWEVER...FARTHER TO THE
NORTHWEST...ACROSS SOUTHWESTERN WISCONSIN AND FAR NORTHWESTERN
ILLINOIS...SKIES ARE BEGINNING TO CLEAR THIS CLEARING TREND SHOULD
CONTINUE TO PUSH ACROSS NORTHERN ILLINOIS AROUND DAYBREAK.
HOWEVER...IT APPEARS MORE CLOUDS AND FLURRIES WILL BE ON THE WAY
LATER THIS AFTERNOON...TONIGHT AND ON SATURDAY AS WE REMAIN IN A
DISTURBED NORTHWEST FLOW PATTERN ALOFT ALONG THE WESTERN PERIPHERY OF
AN UPPER LEVEL TROUGH ACROSS THE EASTERN HALF OF THE COUNTRY.

THERMODYNAMICS OVER THE LAKE WILL BE VERY FAVORABLE FOR THE
DEVELOPMENT OF LAKE EFFECT SNOW SHOWERS...ESPECIALLY LATER
TONIGHT THROUGH SATURDAY NIGHT ACROSS INDIANA AND MICHIGAN. IT
APPEARS THE NORTHWESTERLY FLOW PATTERN WILL TEND TO FAVOR THE
BETTER LOW LEVEL SHORE CONVERGENCE TO THE EAST OF PORTER COUNTY
INDIANA. HOWEVER...PORTIONS OF NORTHEASTERN PORTER COUNTY COULD
SEE SOME SNOW ACCUMULATIONS FROM THIS ACTIVITY.

TEMPERATURES WILL BE MUCH COOLER THAN THE PAST COUPLE OF DAYS AS
COLDER AIR CONTINUES TO FILTER IN ACROSS THE AREA. SATURDAY WILL BE
THE COLDEST DAY...WITH TEMPERATURES NEAR 20 NORTH TO THE MID 20S
SOUTH. A SURFACE RIDGE OF HIGH PRESSURE LOOKS TO BECOME CENTERED
OVER THE AREA SATURDAY NIGHT INTO EARLY SUNDAY MORNING. THIS WILL
LIKELY LEAD TO A FAIRLY COLD MORNING...WITH TEMPERATURES POSSIBLY
FALLING INTO THE SINGLE DIGITS IN SOME AREAS.

A WARMING TREND BEGINS ON SUNDAY AS THE FLOW TURNS SOUTHEAST OUT
AHEAD OF LOW PRESSURE TAKING SHAPE ACROSS THE PLAINS STATES.
HOWEVER...IN SPITE OF THIS...TEMPERATURES MAY BE SOMEWHAT SLOWER TO
RISE ON SUNDAY DUE TO A COLD START AND THE SOUTHEASTERLY WIND
COMPONENT.

LONG TERM...MONDAY THROUGH THURSDAY NIGHT...

CONDITIONS SHOULD WARM NICELY ON MONDAY AS TEMPERATURES CLIMB WELL
INTO THE 40S. RAIN ALSO LOOKS TO BE A GOOD BET...ESPECIALLY MONDAY
AFTERNOON AS ISENTROPIC UPGLIDE INCREASES OUT AHEAD OF THE LOW. THE
SURFACE LOW LOOKS TO TRACK ACROSS THE REGION BY THE EVENING...COLD
AIR SPILLING IN BEHIND THIS SYSTEM MAY LEAD TO A CHANGE OVER TO SOME
SNOW. HOWEVER...IT WILL BE A RACE AS THE PRECIPITATION SHOULD SHUT
OFF QUICKLY DURING THE EVENING. THEREFORE NO SIGNIFICANT SNOWFALL IS
EXPECTED ACROSS THE AREA AT THIS TIME.

THE LARGE SCALE WEATHER PATTERN ACROSS NORTH AMERICA WILL BECOME
FAVORABLE FOR A VERY ACTIVE SOUTHERN STREAM JET LATER NEXT WEEK AS A
NEGATIVE PNA AND NAO PATTERN STRENGTHEN. THE MAIN FEATURES WILL BE
ENHANCED POSITIVE HEIGHT ANOMALIES ACROSS THE PACIFIC JUST SOUTH OF
THE ALEUTIANS AND ALSO ACROSS THE NORTH ATLANTIC. TELECONNECTIONS
RELATED TO THESE FEATURES FAVOR THE DEEPENING OF A TROUGH ACROSS THE
WESTERN CONUS AND BELOW AVERAGE HEIGHTS ACROSS MOST OF THE CONUS.
THIS PATTERN LOOKS TO SUPPORT A POTENT STORM SYSTEM BY THE END OF
NEXT WEEK. THE FINNER SCALE DETAILS OF THIS SYSTEM THIS FAR OUT ARE
LARGELY UNCERTAIN. EVEN THE ACTUAL TIMING OF THE SYSTEM IS SOMEWHAT
UNCERTAIN...AS THE STRENGTH OF THE SYSTEM COULD FAVOR A SLOWER
SOLUTION THAN THE CURRENT FORECAST SUGGESTS. HOWEVER...CONFIDENCE IS
ABOVE AVERAGE THAT A SIGNIFICANT STORM SYSTEM WILL TRACK ACROSS THE
CENTRAL CONUS BY THE END OF NEXT WEEK. THIS COULD PRODUCE
SIGNIFICANT SNOWFALL...THUS THIS SYSTEM WILL BE OF INCREASING
INTEREST OVER THE NEXT SEVERAL DAYS. THIS ACTIVE SOUTHERN JET
PATTERN COULD EVEN CONTINUE PAST THE 7 DAY FORECAST PERIOD LEADING
TO ADDITIONAL STORM SYSTEMS.

KJB

&&

AVIATION...

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

* NORTHWEST WINDS OCCASIONALLY GUSTING BETWEEN 15 AND 20 KT TODAY
  AND AGAIN TOMORROW.

PAW

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

VFR CONDITIONS PREVAILING EARLY THIS AFTERNOON IN THE WAKE OF A
DEPARTING UPPER LEVEL WAVE. YET ANOTHER WEAK WAVE WILL MOVE ACROSS
NORTHERN IL AND NORTHWEST IN OVERNIGHT. THIS WILL INCREASE THE
CLOUDS AT VFR LEVELS...BECOMING CEILINGS BY LATE AFTERNOON OR
EARLY EVENING. THERE IS POTENTIAL FOR SOME FLURRIES WITH THESE
CEILINGS BUT CONFIDENCE IS TOO LOW TO INCLUDE IN THE TAFS AT
THIS TIME. THEN CEILINGS SCATTERING OUT AGAIN SATURDAY BEHIND THE
WAVE.

PAW


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

PAW

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

SATURDAY NIGHT AND SUNDAY...VFR.

MONDAY...CHANCE OF RAIN BECOMING SNOW OVERNIGHT...MVFR PSBL.

TUESDAY...GUSTY W/NW WINDS. VFR.

WEDNESDAY...VFR.

THURSDAY...CHANCE OF SNOW AND GUSTY WINDS. MVFR PSBL.

JEE

&&

MARINE...
323 AM CST

LOW PRESSURE CURRENTLY OVER SE ONTARIO WILL CONTINUE TO WEAKEN AS
IT MOVES NORTHEAST WHILE HIGH PRESSURE OVER THE CENTRAL PLAINS
WILL ALSO DRIFT EAST. WHILE IN BTWN THE SYSTEMS...NW WINDS 15 TO
25 KT ARE EXPECTED THROUGH SATURDAY. THE HIGH PASSES OVERHEAD
SATURDAY NIGHT WITH WINDS WEAKENING AND BECOMING SOUTH BY SUNDAY
AFTERNOON. LOW PRESSURE FORMS OVER SASKATCHEWAN SUNDAY MORNING
WITH WINDS INCREASING ACROSS THE LAKE THROUGH MONDAY WITH 30 KT
GUSTS POSSIBLE ON MONDAY. GUIDANCE DIFFERS ON IF THE LOW WILL PASS
NORTH OF LAKE MICHIGAN OR THROUGH CENTRAL LAKE MICHIGAN...BUT
GUIDANCE DOES AGREE THAT GALES ARE LIKELY BEHIND THE LOW LATE
MONDAY NIGHT THROUGH TUESDAY. THE LOW DEEPENS SLIGHTLY AS IT
PASSES...STRONG HEIGHT RISES...AND COLD AIR ADVECTION BEHIND THE
LOW ALSO SUPPORT THE IDEA OF GALES. WINDS ALOFT ARE TERRIBLY
STRONG SO KEPT GALES AT 35 KT FOR NOW. HIGH PRESSURE MOVES ACROSS
THE LAKE WEDNESDAY NIGHT WITH WINDS DIMINISHING AND BECOMING EAST.
GUIDANCE ALSO SUGGESTS A STRONG LOW WILL APPROACH FROM THE
SOUTHWEST THURSDAY NIGHT AND FRIDAY...WITH ANOTHER ROUND OF GALES
POSSIBLE.

FOR THE NEARSHORE ZONES...THE PERSISTENT NORTHWEST FLOW WILL ALLOW
HAZARDOUS WAVES TO BUILD ACROSS THE IL WATERS. THEREFORE ISSUED A
SMALL CRAFT ADVISORY FOR MIDNIGHT TONIGHT THROUGH MIDNIGHT ON
SUNDAY. THE SMALL CRAFT ADVISORY FOR THE INDIANA SHORES STILL LOOKS
VALID WITH AN END TIME OF 8AM SUNDAY MORNING.

JEE

&&

LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 AM SUNDAY