230 PM CDT
THIS WEEKEND...FAIR WEATHER WILL PERSIST THROUGH THE REMAINDER OF
THE DAY AS RIDGE AXIS SLIDES EAST ACROSS THE REGION. POTENT MID
LEVEL SHORTWAVE OVER THE FOUR CORNERS REGION WILL BEGIN TO LIFT
NORTHEAST WITH LOW PRESSURE DEVELOPING LEE OF THE FRONT RANGE IN
COLORADO. THIS LOW WILL LIFT NORTH ACROSS THE NORTHERN PLAINS INTO
MANITOBA EARLY ON SUNDAY...WITH SOUTHERLY FLOW RAMPING UP ACROSS
NORTHERN ILLINOIS AND NORTHWEST INDIANA. THIS LOW WILL DRAG A WEAK
COLD FRONT ACROSS THE AREA...BUT AS THE LOW LIFTS AWAY INTO HUDSON
BAY...FORCING ALONG THE FRONT LOCALLY WILL BE WEAK...WITH MOISTURE
RETURN SLOW DUE TO ORIENTATION OF THE RIDGE AXIS INTO THE LOWER
MISSISSIPPI VALLEY. WHILE MODELS HAVE BEEN SHOWING SOME CHANCE OF
PRECIPITATION...PARTICULARLY LATER IN THE DAY SUNDAY...WILL PLAY
DOWN CHANCES FOR NOW AND MAINTAIN SLIGHT CHANCE WORDING.
MONDAY THROUGH WEDNESDAY MORNING...PWATS BEGIN TO RAMP UP FROM THE
SOUTHWEST AS MOISTURE FINALLY ARRIVES OVERNIGHT SUNDAY NIGHT.
ISENTROPIC ASCENT ALSO INCREASES BEGINNING EARLY MONDAY IN RESPONSE
TO CYCLOGENESIS OVER THE CENTRAL PLAINS AS ANOTHER POTENT UPPER LEVEL
WAVE ROUNDS THE BASE OF THE LONGWAVE TROUGH ACROSS THE INTERMOUNTAIN
WEST. INITIALLY EXPECT CHANCE OF RAIN TO INCREASE FROM THE SOUTH TO
NORTH ACROSS CWA...BUT BY TUESDAY AFTERNOON WE SHOULD BE GETTING
INTO THE WARM SECTOR AND MAY SEE SOME AREAS ACROSS SOUTH CAPPED
ALLOWING AT LEAST A PERIOD OF DRY WEATHER. OPTED TO ONCE AGAIN GO
ABOVE MOST GUIDANCE...LEANING TOWARDS ECMWF TEMPERATURES...WHICH
ECMWF SEEMS TO HANDLE ANOMALOUSLY WARM SCENARIOS WELL...AND SUSPECT
WE STILL MAY BE A BIT TOO LOW ON TEMPS TUESDAY. MODELS HAVE BEEN
TRENDING THIS SYSTEM SLOWER...ESPECIALLY THE ECMWF...WHICH MAY END
UP REQUIRING TEMPERATURES TO BE BUMPED UP QUITE A BIT ON WEDNESDAY
AS WELL... MAIN WAVE WILL MOVE APPROACH THE WESTERN PORTION OF CWA
SOMETIME OVERNIGHT TUESDAY INTO EARLY WEDNESDAY MORNING. WITH STRONG
THETA-E ADVECTION THANKS TO 50+ KT LOW LEVEL JET...AND VERY STRONG
SHEAR VALUES...0-6KM IN EXCESS OF 50 KT...STILL LOOKING AT POTENTIAL
FOR THUNDERSTORMS RETURNING TO THE AREA...WITH A NON-ZERO SEVERE
THREAT. WONT DIVE ANY FARTHER INTO THE CONVECTIVE DETAILS THIS FAR
OUT...BUT CERTAINLY MODELS CONTINUE TO INDICATE POTENTIAL.
WEDNESDAY AFTERNOON THROUGH FRIDAY...LATEST GUIDANCE TRACKS THE LOW
NORTH OF THE CWA BY WEDNESDAY EVENING WITH DRY SLOT POSSIBLY
ALLOWING WX TO QUIET SOME...ESPECIALLY ACROSS THE SOUTH. ANY
DEFORMATION ZONE PRECIP THAT MAY SWING THROUGH THE AREA ON WEDNESDAY
NIGHT MAY BE IN THE FORM OF SNOW AS 850 TEMPS PLUMMET TO AROUND
-6C...AND SURFACE TEMPS DROP TO AROUND FREEZING...ESPECIALLY FOR
AREAS WEST OF THE FOX RIVER VALLEY. RIDGING BUILDS JUST SOUTH THE
AREA ON THURSDAY WHICH SHOULD DRY US OUT...BUT TEMPS WILL REMAIN
COOL IN THE 40S AND 50S ON FRIDAY AS COOL NORTHWESTERLY WINDS
PREVAIL. LATEST GFS AND ECMWF BOTH HINTING AT A CLIPPER LIKE SYSTEM
ON FRIDAY...BUT FOR NOW TRACK LOOKS TO BE NORTH OF THE AREA AND WONT
INTRODUCE POPS. BMD
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 03Z...
* LOW LEVEL WIND SHEAR TOWARD EARLY MORNING...WITH STRONG GUSTS
MIXING DOWN SOON AFTER THAT.
* LOW VFR CEILINGS POSSIBLE THIS AFTERNOON.
LENNING
//DISCUSSION...UPDATED 00Z...
A TIGHTENING PRESSURE GRADIENT BEHIND A SLOWLY RETREATING EAST
COAST HIGH AND AN APPROACHING LOW OVER THE DAKOTAS WILL RESULT IN
GUSTY SOUTH WINDS TOMORROW AFTERNOON. THE ONSET OF A STRONG LOW
LEVEL INVERSION THIS EVENING WILL KEEP THESE STRONGER WINDS
TRAPPED ABOVE THE BOUNDARY LAYER UNTIL DAYTIME MIXING KICKS IN
TOMORROW MORNING...SO THERE LIKELY WILL BE A PERIOD OF LOW LEVEL
WIND SHEAR LATE TONIGHT THROUGH EARLY TO MID MORNING. FORECAST
MODELS ARE SHOWING 50KTS JUST ABOVE THE 2000 FT LEVEL. IN
ADDITION...INCREASING LOW LEVEL MOISTURE TOMORROW AFTERNOON WILL
LOWER CEILINGS...BUT AT THIS POINT THESE APPEAR TO STAY IN THE VFR
FLIGHT CATEGORY. THE INCREASING MOISTURE ALSO BRINGS A SLIGHT
CHANCE OF SHOWERS LATER IN THE DAY...BUT WILL LEAVE THIS ADDITION
FOR LATER FORECAST PACKAGES IF MODEL TRENDS BECOME MORE FAVORABLE.
THE OTHER EFFECT OF THIS INCREASING MOISTURE AND CLOUDINESS WOULD
BE TO BRING AN EARLIER END TO THE GUSTS AS LOW LEVEL VERTICAL
MIXING DIMINISHES WITH DECREASING INSOLATION.
LENNING
//ORD AND MDW CONFIDENCE...UPDATED 03Z...
* MEDIUM TO HIGH CONFIDENCE THAT STRONG WINDS JUST ABOVE THE LOW
LEVEL TEMPERATURE INVERSION COULD CAUSE WIND SHEAR ISSUES TOWARD
MORNING.
* MEDIUM CONFIDENCE IN STRENGTH AND DURATION OF GUSTS SUNDAY
AFTERNOON.
* MEDIUM CONFIDENCE IN CEILING TRENDS SUNDAY AFTERNOON.
LENNING
//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...
MONDAY...VFR. CHC SHRA MAINLY LATE. ISO TSRA WITH MVFR CIGS.
TUESDAY...MVFR. SHRA/ISO TSRA.
WEDNESDAY...MVFR TRENDING VFR. SHRA.
THURSDAY...PATCHY MVFR. SHRA PSBLY MIXED SN.
FRIDAY AND FRIDAY NIGHT...VFR.
LENNING
&&
.MARINE...
234 PM CDT
SOUTHERLY GALES ARE THE MAIN FORECAST CONCERN AS LOW PRESSURE NOW
STRETCHING FROM THE WESTERN DAKOTAS INTO NORTHEAST COLORADO DEEPENS
SLIGHTLY AND MOVES INTO SOUTHERN MANITOBA INTO SUNDAY AFTERNOON.
WITH HIGH PRESSURE FROM NORTHERN NEW ENGLAND INTO THE MID-ATLANTIC
STATES MOVING VERY LITTLE...THE PRESSURE GRADIENT ACROSS LAKE
MICHIGAN WILL TIGHTEN TONIGHT AND ESPECIALLY SUNDAY. WINDS WILL
GRADUALLY COME UP TONIGHT AND GUSTS SHOULD START TO INCREASE
OVERNIGHT AS STABILITY DECREASES AND MIXING INCREASES WITH COOLER
AIR SPREADING OVER FROM LAND. LOW LEVEL WINDS WILL BE INCREASING
AS WELL AND GUSTS MAY JUST REACH GALE FORCE PRIOR TO
DAYBREAK...ESPECIALLY NORTH. AS DAYTIME HEATING OCCURS THERE MAY
BE A LULL IN THE GUSTS WITH WARMER LAND AIR SPREADING ACROSS THE
LAKE BUT COOL ADVECTION LOOKS TO ARRIVE FOR THE AFTERNOON ALLOWING
MIXING TO DEEPEN FURTHER. POTENTIAL FOR STRONGEST WINDS LIES
ACROSS THE NORTH HALF OF THE LAKE WITH 40 KT POSSIBLE AT
TIMES...ESPECIALLY DURING THE AFTERNOON. GALES ARE A BIT MORE
MARGINAL SOUTH BUT WILL HOIST THE GALE WARNING WITH 30-35 KT GUSTS
EXPECTED THOUGH SOME IN THE 35-40 KT RANGE MAY OCCUR. WITH GOOD
MIXING OVER LAND THE NEARSHORE WATERS WILL HAVE SOME GALE POTENTIAL
BUT WILL KEEP THE SMALL CRAFT AND 30 KT FOR NOW. THE GRADIENT
WEAKENS LATER SUNDAY EVENING ALLOWING WINDS TO DIMINISH AS HIGH
PRESSURE ARRIVES INTO MONDAY.
ANOTHER LOW PRESSURE SYSTEM WILL DEVELOP...THIS TIME OVER THE
SOUTHERN PLAINS AND LIFT NORTHWARD TUESDAY. HOW QUICKLY THIS LOW
ARRIVES IS STILL NOT CERTAIN AND IT MAY ARRIVE SLOWER THAN
CURRENTLY EXPECTED. EITHER WAY...A WARM FRONT SHOULD BISECT THE
LAKE TUESDAY AND LIFT NORTHWARD WITH STRONG NORTHEASTERLY WINDS TO
THE NORTH AND SOUTH/SOUTHEASTERLY WINDS TO THE SOUTH. STRENGTH OF
THE WINDS WILL DEPEND ON WHERE THE LOW TRACKS RELATIVE TO THE LAKE
AND THERE ARE SIGNS IT MAY REMAIN WEST OF THE LAKE AS IT MOVES
NORTH WHICH WOULD SUPPORT STRONGER WINDS THAN CURRENTLY FORECAST.
HOWEVER...MUCH WARMER AIR MOVING INTO THE REGION WOULD PROBABLY
RESULT IN A STABLE MARINE LAYER KEEPING WINDS IN CHECK. WILL
CONTINUE TO MONITOR BUT FOR NOW EXPECT WINDS TO REMAIN SUB-GALE
BUT POSSIBLY BE STRONGER THAN THE CURRENT FORECAST.
MDB/MTF
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-LMZ868-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...3 AM SUNDAY TO 9 PM
SUNDAY.
SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO NORTHERLY IS UNTIL 9 PM SUNDAY.
SMALL CRAFT ADVISORY...LMZ742-LMZ743-LMZ744-LMZ745...3 AM SUNDAY
TO 9 PM SUNDAY.
&&
$$
