🚀 go-pugleaf

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1227 PM CDT MON MAY 13 2013

.DISCUSSION...
258 AM CDT

AFTER A FRIGID START TO THE WORK WEEK THIS MORNING (BY MID MAY`S
STANDARDS) IT LOOKS LIKE THE REGION WILL BE IN FOR ONE OF THE
LARGEST SINGLE CALENDAR TEMPERATURE CLIMBS EVER IN THE MONTH OF
MAY BY TUESDAY (WILL SEND OUT PNS SHORTLY WITH SOME STATS ON
THAT)! WEAK COLD FRONT MOVES THROUGH TUESDAY NIGHT WITH TRANSITION
TOWARD COOLER...THOUGH STILL SOMEWHAT ABOVE AVG TEMPS THE
REMAINDER OF THE WEEK.

WHAT APPEARS TO BE OLD MAN WINTER`S DYING LAST BREATHE IS GREETING
THE AREA THIS MORNING WITH PRE-DAWN TEMPERATURES MOSTLY IN THE 30S
OUTSIDE OF THE CHICAGO URBAN HEAT ISLAND. SUNNY SKIES TO START THE
DAY WILL GIVE WAY TO BKN-OVC MID-HIGH LEVEL DECK AS THE DAY WEARS AS
WARM AIR ADVECTION/ISENTROPIC ASCENT ALOFT KICK INTO HIGH GEAR
HERALDING THE BEGINNINGS OF OUR EPIC WARM UP WHICH COMES TOMORROW.
REGION IS LARGELY VOID OF LOW LEVEL MOISTURE AND WITH RECENT COLD
FRONT MAKING IT NEARLY TO THE NW CARIBBEAN SEA THE GULF OF MEXICO IS
ESSENTIALLY SHUT DOWN FOR BUSINESS. THIS MEANS ANY PRECIPITATION
WITH THE STRONG WARM ADVECTION WILL HAVE TO RELY NEARLY EXCLUSIVELY
ON ASCENT FOR SATURATION AND WITH LARGE CONDENSATION PRESSURE
DEFICITS TO BEGINS WITH THINK THE PRECIP THREAT WILL BE LOW WITH THE
WARM FRONT TONIGHT. HAVE HELD ONTO SOME SLIGHT CHANCE POPS FOR SOME
LIGHT SHOWERS/SPRINKLES BUT SUSPECT THIS WILL LARGELY TURN INTO A
BIG VIRGA EVENT.

WARM FRONT CLEARS THE AREA EARLY TUESDAY MORNING AND THE FLOOD GATES
SWING OPEN ALLOWING UNSEASONABLY WARM AIR TO SURGE INTO THE AREA.
MODELS FORECAST 24 HOURS 850MB TEMPS RISES OF 16-20C FROM THIS
EVENING TO TUESDAY EVENING. MODELS SEEMS TO REALLY BE STRUGGLING TO
ACCURATELY DEPICT BOUNDARY LAYER MOISTURE...WHICH IS LIKELY ALSO
PLAYING A ROLE IN APPARENT COOL BIAS IN THE MODELS FOR TUESDAY.
STRONG APPARENT EVAPOTRANSPIRATION SIGNAL IN THE MODELS RESULTS IN
MASSIVE POOL OF 60 DEGREE DEWPOINTS MATERIALIZING OVER THE AREA
TUESDAY...BUT AS ALLUDED TO ALREADY THE GULF IS SHUT DOWN AND CORN
CROP IS WELL BEHIND SCHEDULE FOR THIS TIME OF YEAR SO IT WOULD SEEM
HIGHLY LIKELY THAT THE SFC TD FORECASTS ARE FAR TOO HIGH. HAVE GONE
5-10F LOWER WITH DEWPOINTS THAN GUIDANCE BUT EVEN THESE VALUES MAY
BE TOO HIGH WITH EVEN 50F DEWPOINTS POTENTIALLY A STRETCH. THE VERY
DRY AIR AND SUNNY SKIES SHOULD ALLOW TEMPERATURES TO SOAR TUESDAY
WITH MODEL FORECAST 925MB/850MB CLIMO STRONGLY SUPPORTING MID TO
UPPER 80S. THE HAND FULL OF MAY 90 DEGREE TEMPS THAT HAVE OCCURRED
IN MAY HAVE FEATURED 925MB TEMPS OF 19-23C AND 850MB TEMPS OF 15-20C
WHICH IS THE BALL PARK FOR MODEL FORECASTS FOR OUR TEMPS TOMORROW.
GOING TO REFRAIN FROM PUTTING ANY 90S IN THE GRIDS...BUT REALLY
WOULDNT BE AT ALL SURPRISED TO SEE A FEW LOCATIONS CRACK THE 90
DEGREE MARK...PARTICULARLY WESTERN CWA.

WEAK COLD FRONT SLIPS SOUTH THROUGH THE AREA WED AM BUT WITH
MOISTURE LACKING AND OVERDONE IN THE MODELS SUSPECT IT WILL BE A DRY
FRONTAL PASSAGE. GUSTY SOUTHWEST WINDS WITH THE LOW LEVEL THERMAL
AXIS OVERHEAD TUESDAY NIGHT SHOULD RESULT IN RECORD/NEAR RECORD WARM
LOWS IN THE MID-UPPER 60S...WITH CHICAGO HEAT ISLAND PROBABLY
HOLDING IN THE LOW TO MID 70S MUCH OF THE NIGHT. THE WARM START TO
THE DAY WEDNESDAY COMBINED WITH ONLY VERY WEAK COLD AIR ADVECTION
SHOULD SET THE STAGE FOR ANOTHER DAY INTO THE 80S ON WEDNESDAY.
CAN`T RULE OUT AN AFTERNOON THUNDERSTORM ALONG THE FRONT FAR
SOUTHERN CWA BUT GENERALLY LOOKS LIKE IT WILL MAKE IT THROUGH MOST
IF NOT ALL THE CWA WITH LITTLE FANFARE. AS WINDS TURN LIGHT
NORTHWESTERLY BEHIND THE FRONT LATE WEDNESDAY AFTERNOON SET-UP LOOKS
FAVORABLE FOR A STRONG LAKE BREEZE PUSH TO DEVELOP LATE WED
AFTERNOON INTO WEDNESDAY EVENING...WHICH COULD SEND TEMPS PLUMMETING
INTO THE 50S (MAYBE 40S RIGHT ALONG THE SHORE).

DOES LOOKS LIKE FRONT STALLS OUT SOUTH OF THE AREA LATE IN THE WEEK
SETTING THE STAGE FOR SEASONABLY WARM WEATHER AND LITTLE THREAT OF
RAIN UNTIL FRIDAY OR MORE LIKELY THE WEEKEND AS THE FRONT BEGINS TO
LIFT BACK NORTH. TEMPERATURES SHOULD REMAIN ABOVE AVERAGE...THOUGH
LAKE BREEZES WILL LIKELY KEEP NATURE`S AIR CONDITIONER CRANKED ON
HIGH WITH LAKE SIDE AREAS LIKELY IN THE 50S TO MAYBE LOW 60S. DOES
LOOK LIKE A MORE UNSETTLED PATTERN NEXT WEEKEND WITH AT LEAST THE
THREAT OF SOME SHOWERS AND THUNDERSTORMS...THOUGH MEDIUM RANGE
MODELS HAVE BEEN WAFFLING AROUND WITH THE DETAILS SO CONFIDENCE IS
NOT TERRIBLY HIGH IN THE FORECAST FOR NEXT WEEKEND AND I WOULDNT GO
CANCELING ANY PLANS BECAUSE EVEN IF WE GET SOME SHOWERS/STORMS
SUSPECT THERE WILL BE MANY DRY HOURS AS WELL.

IZZI

&&

.AVIATION...

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

* WESTERLY WINDS SHIFTING TO EAST TO SOUTHEAST WITH THE LAKE
  BREEZE AROUND 20Z.

PAW

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

SURFACE HIGH PRESSURE DOMINATING NORTHERN ILLINOIS AND NORTHWEST
INDIANA WEATHER THIS AFTERNOON WITH JUST A FEW VFR-LEVEL CLOUDS.
LAKE BREEZE CAN BE SEEN ON RADAR ALREADY PAST GYY...SHOULD PASS BOTH
ORD AND MDW AROUND 20Z...AND MAY GET AS FAR INLAND AS DPA AROUND
00Z. WINDS AT RFD SHOULD GRADUALLY SHIFT MORE TO THE SOUTH AS THE
HIGH PRESSURE MOVES AWAY THROUGH THE AFTERNOON. AN UPPER LEVEL
DISTURBANCE WILL BRING VFR CLOUDS OR CEILINGS TO THE TERMINALS
OVERNIGHT...BUT APPEARS THAT ANY PRECIPITATION WILL STAY TO THE
NORTH OF THE TERMINALS. VFR CONDITIONS AGAIN ON TUESDAY WITH GUSTY
SOUTH TO SOUTHWEST WINDS AHEAD OF THE NEXT FRONTAL SYSTEM.

PAW

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

* MEDIUM CONFIDENCE IN LAKE BREEZE TIMING.

PAW

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

TUESDAY NIGHT...VFR.

WEDNESDAY...VFR.

THURSDAY...VFR.

FRIDAY...CHANCE OF TSRA...OTHERWISE VFR.

SATURDAY...CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...CHANCE OF TSRA...OTHERWISE VFR.

RODRIGUEZ

&&

.MARINE...
310 AM CDT

AS LOW PRESSURE OVER QUEBEC LIFTS NORTH TODAY...HIGH PRESSURE
SITUATED FROM ONTARIO SOUTH TO THE SOUTHERN GULF STATES WILL
CONTINUE SHIFTING EAST TOWARDS THE CENTRAL GREAT LAKES. THIS IS
CURRENTLY RESULTING IN A NORTHWEST WIND ACROSS THE NORTHERN HALF
OF THE LAKE...WHILE LIGHTER AND MORE VARIABLE WINDS ARE OCCURRING
ACROSS THE SOUTHERN HALF. ANY STRONGER WINDS OCCURRING RIGHT NOW
WILL FURTHER DIMINISH OVER THE NEXT SEVERAL HOURS AS THIS HIGH
MOVES OVER HEAD. ALTHOUGH AS THIS OCCURS...THE PRESSURE FIELD WILL
BEGIN TO BECOME MORE ORGANIZED LATER THIS AFTERNOON AS A SYSTEM
BEGINS TO TAKE SHAPE TO THE WEST. THIS WILL RESULT IN WINDS
BECOMING MORE SOUTHERLY LATE THIS AFTERNOON INTO THE EVENING...AND
BEGIN INCREASING. SOUTHERLY WINDS WILL INCREASE TO 15 TO 25 KT
TONIGHT AND CONTINUE INTO TUESDAY AS THIS SYSTEM SLOWLY MOVES
EAST. THEN AS THIS SYSTEM PROGRESSES ACROSS THE GREAT LAKES REGION
TUESDAY NIGHT INTO WEDNESDAY...EXPECT WINDS TO BECOME MORE
SOUTHWEST AND THEN WEST ON WEDNESDAY WHILE SLOWLY DIMINISHING.

RODRIGUEZ

&&

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

$$


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