309 AM CST
AN ACTIVE FEW DAYS LAY AHEAD WITH THE MAIN FORECAST CONCERNS
CENTERED AROUND WINDS AND PRECIP CHANCES. EARLY MORNING WATER VAPOR
IMAGERY SHOWS A CORRIDOR OF FAIRLY FLAT UPPER FLOW OVER THE EASTERN
HALF OF THE COUNTRY WITH SLIGHT UPPER RIDGING TRANSLATING EASTWARD
ACROSS THE NORTHERN PLAINS AND UPPER MISSISSIPPI RIVER VALLEY. TO
THE WEST...A SERIES OF SHORTWAVES ARE LINED UP WITH ONE DIGGING INTO
WESTERN MONTANA AND ANOTHER MOVING ALONG THE SOUTHEASTERN ALASKAN
COAST TOWARD FAR NORTHERN BRITISH COLUMBIA. ANOTHER UPPER TROUGH IS
CUT OFF FROM THIS NORTHERN STREAM OF FLOW JUST OFF THE CALIFORNIA
COAST AND WILL PLAY A ROLE IN PRECIP CHANCES FOR OUR AREA EARLY NEXT
WEEK. AT THE SURFACE...LOW PRESSURE WAS OBSERVED JUST NORTHEAST OF
LAKE SUPERIOR. ANOTHER SURFACE LOW IS DEVELOPING OVER SOUTHERN
SASKATCHEWAN/CENTRAL MONTANA AS A RESULT OF THE AFOREMENTIONED UPPER
SHORTWAVE WITH A SUBTLE WARM FRONT/TROUGH ANALYZED FROM THE LOW
ARCHING SOUTHEASTWARD ACROSS NORTHERN ILLINOIS AND INDIANA. THIS LOW
WILL BE KEY IN BRINGING INCREASING WINDS TO THE REGION TONIGHT AND
SUNDAY.
TODAY...AM EXPECTING A MILDER DAY TODAY WITH WARM ADVECTION ONGOING
EARLY THIS MORNING. SOUTH WINDS WILL INCREASE EARLY THIS AFTERNOON
AND BECOME SOMEWHAT GUSTY AS THE PRESSURE GRADIENT TIGHTENS WITH THE
SURFACE LOW DEEPENING OVER THE NORTHERN PLAINS. MIXING TO BETWEEN
950 AND 925 MB IS EXPECTED TODAY RESULTING IN GUSTS AROUND 20 KT AT
TIMES AND HIGHS IN THE MID 50S NORTH TO UPPER 50S SOUTH OF
INTERSTATE 88...WITH A FEW AREAS POSSIBLY REACHING 60 DEGREES MAINLY
SOUTH OF INTERSTATE 80 THANKS TO THE BREEZY SOUTH-SOUTHWEST WINDS.
TONIGHT THROUGH SUNDAY NIGHT...THE SURFACE LOW WILL MOVE FROM
EASTERN NORTH DAKOTA INTO WESTERN ONTARIO TONIGHT WHILE DEEPENING
INTO THE 980-985 MB RANGE. WINDS AND TEMPS WILL BE TRICKY AS THEY
WILL BE DICTATED BY THE DECOUPLING OF THE BOUNDARY LAYER THIS
EVENING. AM THINKING THAT DECOUPLING MAY OCCUR WITH SUNSET LATE THIS
AFTERNOON ALLOWING GUSTS TO DIMINISH BUT THE TIGHTENING PRESSURE
GRADIENT WILL KEEP SUSTAINED WIND SPEEDS UP. THIS WOULD LEAD TO
LITTLE DROP OFF IN TEMPS THIS EVENING. A WEAK UPPER WAVE LOOKS TO
LIFT NORTHEASTWARD ACROSS THE AREA THIS EVENING BRINGING MODEST MID
LEVEL COOL ADVECTION FOR A SHORT TIME AND MAY SERVE AS A CATALYST
FOR MIXING TO RE-DEVELOP LEADING TO A RETURN OF WIND GUSTS. THE
CONCERN IS THAT THE LOW LEVEL JET RAMPS UP SIGNIFICANTLY THIS
EVENING WITH FORECAST SOUNDINGS INDICATING 30+ KT WINDS STARTING
AROUND 600 FT AGL AND 40+ KT WINDS AT 1000 FT WITH A PEAK AT AROUND
60 KT UP AROUND 2500 FT. ITS NOT OUT OF THE QUESTION THAT 30 KT
GUSTS COULD OCCUR OVERNIGHT. ANOTHER WARM FRONT LOOKS TO QUICKLY
CROSS THE AREA EARLY SUNDAY MORNING WITH A LOW LEVEL THERMAL AXIS
CRESTING THE AREA. WINDS BECOME A BIGGER ISSUE SUNDAY AS MIXING
COMMENCES. THE LOW WILL BE LIFTING NORTHEASTWARD TOWARDS SOUTHERN
HUDSON BAY AND LIKELY BE SOMEWHERE AROUND 980 MB. PEAK LOW LEVEL
WINDS DO SUBSIDE BUT A DEEP LAYER OF 40-50 KT WINDS CONTINUES INTO
EARLY SUNDAY AFTERNOON. MIXING SUPPORTS GUSTS TO NEAR 40 KT DURING
THE DAY WITH POTENTIAL FOR A BRIEF PERIOD OF HIGHER GUSTS OF 45 KT
OR POSSIBLY HIGHER AS THE COLD FRONT PASSES AROUND MIDDAY. PRECIP
CHANCES ARE NOT IMPRESSIVE WITH DEEP LAYER MOISTURE LACKING SO WILL
CONTINUE WITH SLIGHT AND LOW CHANCE POPS BUT THESE MAY EVEN BE TOO
HIGH. WINDS WILL DIMINISH OVER LAND AREAS SUNDAY EVENING.
MONDAY THROUGH WEDNESDAY...THE COOL FRONTAL BOUNDARY WILL WEAKEN AND
WASH OUT TO THE SOUTH AND EAST OF THE AREA SUNDAY NIGHT INTO MONDAY
BUT STILL BE INTACT ENOUGH TO KEEP A BELT OF POOLED MOISTURE FROM
THE LOWER LAKES INTO CENTRAL ILLINOIS. THE ALASKAN UPPER WAVE WILL
DAMPEN BUT THE NORTHERN STREAM WILL BEGIN TO PHASE WITH THE
CALIFORNIA CUTOFF UPPER LOW. A LEAD SHORTWAVE WILL EJECT
NORTHEASTWARD FROM THE CENTRAL PLAINS AHEAD OF THE DEVELOPING
LONGWAVE TROUGH AXIS AND PUSH A WEAK SURFACE TROUGH ALONG THE OLD
FRONT/AREA OF POOLED MOISTURE MONDAY. THIS SHOULD PUSH THE MOISTURE
NORTHWARD AND BACK INTO MOST OF THE FORECAST AREA MONDAY MORNING.
THIS WILL SUPPORT INCREASED RAIN CHANCES...PRIMARILY ACROSS THE
SOUTHEAST TWO-THIRDS TO THREE-QUARTERS OF THE AREA MONDAY. THE
LARGER SCALE UPPER TROUGH WILL SWING ACROSS THE AREA AS IT AMPLIFIES
TUESDAY WITH ANOTHER SURFACE LOW MOVING FROM THE UPPER MISSISSIPPI
RIVER VALLEY INTO WESTERN ONTARIO. ANOTHER SHARP COLD FRONT WILL
CROSS THE AREA LATER TUESDAY AFTERNOON OR EARLY TUESDAY EVENING.
ANOTHER PERIOD OF GUSTY WINDS IS EXPECTED WITH THE STRONG COLD
ADVECTION AS H85 TEMPS FALL BACK TO THE -6 OR -8 C RANGE INTO
WEDNESDAY FROM THEIR ABOVE ZERO C READINGS PRIOR TO THAT.
THURSDAY AND FRIDAY...DRIER WEATHER WILL RETURN INTO THURSDAY AS
HIGH PRESSURE MOVES SOUTH OF THE AREA BUT THE UPPER FLOW PATTERN
WILL REMAIN ACTIVE JUST TO THE NORTH OF THE AREA. THEREFORE CANNOT
RULE OUT A WAVE MOVING CLOSE ENOUGH TO THE AREA TO KICK OFF SOME
SHOWERS ESPECIALLY AS WARM ADVECTION RETURNS THURSDAY NIGHT. THE
UPPER FLOW WILL TURN SOUTHWESTERLY SUGGESTING A RETURN TO MORE
ACTIVE WEATHER NEXT WEEKEND THOUGH WE SHOULD SEE AN UPSWING IN TEMPS
BY THAT TIME.
MDB
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 09Z...
* SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 20KT TODAY.
* POTENTIAL FOR WIND GUSTS IN EXCESS OF 25 KT TONIGHT.
KREIN
//DISCUSSION...UPDATED 06Z...
GUSTY SOUTH-SOUTHWEST WINDS ARE THE MAIN CONCERN THROUGH THE
CURRENT TAF PERIOD.
WARM FRONTAL TROUGH HAS BECOME LESS WELL-DEFINED AS IT LIFTS
NORTHEAST ACROSS THE AREA THIS EVENING. THIS...COMBINED WITH
DIURNAL LOSS OF LOW LEVEL MIXING HAS ALLOWED WINDS TO DIMINISH TO
LESS THAN 10 KTS...AND BACK TO THE SOUTH-SOUTHWEST. LIGHT
SOUTHWEST WINDS WILL PREVAIL OVERNIGHT...ALONG WITH VFR
CONDITIONS WITH MAINLY CLEAR SKIES.
WINDS WILL INCREASE ON SATURDAY...ESPECIALLY DURING THE AFTERNOON
HOURS AS DEEP LOW PRESSURE DEVELOPS OVER THE NORTHERN PLAINS.
SURFACE PRESSURE FALLS AND TIGHTENING OF THE PRESSURE GRADIENT
ACROSS THE MIDWEST WILL LIKELY RESULT SOUTHWEST WINDS GUSTING
ABOVE 20 KTS BY MID/LATE AFTERNOON. VRF HIGH CLOUD COVER WILL
INCREASE AND THICKEN DURING THE AFTERNOON...WHICH MAY TEND TO
LIMIT LOW LEVEL MIXING SOMEWHAT.
CONFIDENCE DECREASES IN THE WIND FORECAST SATURDAY EVENING.
THE GRADIENT CONTINUES TO TIGHTEN AS LOW DEEPENS ACROSS THE UPPER
MIDWEST AND SOUTHERN MANITOBA...WHICH IS EXPECTED TO INCREASE
SUSTAINED SPEEDS DURING THE EVENING AND OVERNIGHT HOURS. THE BIG
QUESTION IS HOW GUSTY WINDS WILL BE...AS NOCTURNAL INVERSION
ATTEMPTS TO DEVELOP WITH SUNSET. FORECAST SOUNDINGS INDICATE
CONSIDERABLE MOMENTUM ABOVE THE BOUNDARY LAYER...WITH WINDS
INCREASING TO AROUND 50 KTS AT THE 1500-2000 FT LEVEL. WOULD
SUSPECT THAT GUSTS WILL REMAIN A FACTOR AS BOUNDARY LAYER ATTEMPTS
TO STABILIZE...THUS HAVE INCREASED GUSTS AFTER DARK TO THE 25-30
KT RANGE. GIVEN THE MOMENTUM NOT TOO FAR ABOVE THE SURFACE...
COULD SEE SPORADIC HIGHER GUSTS. MID AND HIGH CLOUD COVER EXPECTED
TO REMAIN VFR...THOUGH POTENTIAL FOR LOWER CIGS AND SPOTTY SHRA
DOES INCREASE TOWARD SUNDAY MORNING ESPECIALLY JUST BEYOND ORD 30
HOUR FORECAST AT THIS TIME.
RATZER
//ORD AND MDW CONFIDENCE...UPDATED 09Z...
* MEDIUM-HIGH CONFIDENCE IN WIND TRENDS THROUGH THIS AFTERNOON.
* MEDIUM CONFIDENCE IN WIND GUST MAGNITUDE TONIGHT.
KREIN
//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...
SUNDAY...CHANCE SHRA AND MVFR CIGS EARLY. WINDY. SWLY GUSTS TO 35
KT IN THE AFTERNOON.
MONDAY...CHANCE SHRA. MVFR CIGS POSSIBLE.
TUESDAY THROUGH THURSDAY...VFR.
RATZER
&&
.MARINE...
300 AM CST
THROUGH THE NIGHT...WINDS HAVE BEEN DROPPING OFF AS LOW PRESSURE
OVER THE UPPER GREAT LAKES LIFTS TO THE NORTHEAST AND WEAKENS.
HOWEVER...WINDS WILL STRENGTHEN AGAIN LATER THIS AFTERNOON AND
EVENING AS LOW PRESSURE DROPS INTO THE NORTHERN PLAINS LATER
TODAY. SOUTH WINDS WILL QUICKLY INCREASE EARLY THIS EVENING TO
SOUTH GALES AS THE LOW RAPIDLY DEEPENS WHILE LIFTING NORTHEAST TO
HUDSON BAY. WINDS WILL BRIEFLY SUBSIDE BELOW GALE FORCE MONDAY
AND TUESDAY...BUT ANOTHER DEEP LOW IS EXPECTED TO DRAG A STRONG
COLD FRONT ACROSS THE LAKE TUESDAY EVENING. THE STRONG COLD
ADVECTION BEHIND THIS FRONT WILL USHER IN ANOTHER ROUND OF GALES
FOR TUESDAY NIGHT AND WEDNESDAY.
KREIN
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-
LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-
LMZ874-LMZ876-LMZ878...9 PM SATURDAY TO 9 PM SUNDAY.
&&
$$
