Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 271959
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
159 PM CST FRI FEB 27 2015

.SHORT TERM...
157 PM CST

THROUGH TONIGHT...

QUIET CONDITIONS TO PREVAIL THIS AFTERNOON INTO TONIGHT AS HIGH
PRESSURE DOMINATES THE REGION. SHEARED OUT SHORTWAVE WILL SHIFT
EAST THROUGH THE REGION TONIGHT...WHILE UPSTREAM ENERGY OVER THE
CENTRAL PLAINS LIFTS EAST/NORTHEAST THROUGH THE MID MISSISSIPPI
VALLEY. THIS WILL HELP PROVIDE AN INCREASE IN MID/HIGH LEVEL CLOUD
COVER TONIGHT...MAINLY ACROSS THE SOUTHEASTERN HALF OF THE CWA.
THIS MOISTURE WILL REMAIN FAIRLY PROGRESSIVE WITH THE THICKER
MOISTURE LIKELY EXITING BY EARLY SATURDAY MORNING...BUT WITH
PARTLY CLOUDY TO POSSIBLY CLOUDIER SKIES FOR A TIME TONIGHT. MADE
MINOR CHANGES TO FORECAST LOWS TONIGHT WITH SUBZERO TEMPS LIKELY
ONCE AGAIN. HOWEVER...DONT FEEL THEY WILL BE AS COLD AS THIS
MORNING BUT DO THINK SOME PLACES COULD APPROACH 10 BELOW. WINDS
SHOULD RAPIDLY DROP OFF THIS EVENING AND ALTHOUGH WIND CHILLS WILL
FALL TO AROUND 15 BELOW ZERO ONCE AGAIN TONIGHT...WONT BE LOW
ENOUGH FOR ANY HEADLINES AT THIS TIME.

RODRIGUEZ

&&

.LONG TERM...
312 AM CST

SATURDAY NIGHT THROUGH THURSDAY...

SHORTWAVE TROUGH IS PROGGED TO DIG DOWN THE WEST COAST SATURDAY...
CLOSING OFF OVER CALIFORNIA SATURDAY NIGHT INTO SUNDAY.
MEANWHILE...AN ALBERTA CLIPPER IS PROGGED TO DIG FROM ALBERTA
SATURDAY EVENING INTO THE UPPER MIDWEST BY SUNDAY EVENING. WITH
SURFACE HIGH PRESSURE SETTLING OFF THE SOUTHEASTERN COAST AND
TROUGHING IN THE WEST...OPEN GULF MOISTURE AND BROAD ASCENT IS
EXPECTED TO SET UP ACROSS THE MID MISSISSIPPI AND OHIO VALLEY
PERSISTING THROUGH THE DAY SUNDAY. WITH LITTLE ORGANIZATION AT THE
SURFACE...MOISTURE IS SOMEWHAT SLOW TO PUSH NORTH ACROSS THE OHIO
VALLEY...BUT PWATS ARE EXPECTED TO RISE TO AROUND 0.70 INCHES IN
CENTRAL ILLINOIS MIDDAY SUNDAY...AROUND +2 SIGMA PER ILX RAOB
CLIMO...THOUGH THE PWATS QUICKLY TAPER TO LESS THAN 0.5 INCHES
ACROSS THE NORTHERN COUNTIES. PRECIPITATION SHOULD BEGIN AS WAA
RAMPS UP OVER THE AREA LATE SATURDAY EVENING THROUGH MIDDAY
SUNDAY. WAA THEN SHIFTS TO THE EAST WHILE DPVA AND BROAD MID LEVEL
HEIGHT FALLS OVERSPREAD THE REGION FROM THE NORTHWEST ALLOWING
SNOW TO CONTINUE SUNDAY AFTERNOON INTO THE EVENING. MID LEVEL
MIXING RATIOS SOUTH OF I-80 AVERAGE OUT TO AROUND 3.0 G/KG
SUGGESTING THE POTENTIAL FOR A HIGH END ADVISORY EVENT IN OUR
SOUTH. THERE ARE SOME LIMITING FACTORS TOO...INCLUDING A
RELATIVELY SHALLOW DGZ THOUGH FORCING DOES SEEM TO BE MAXIMIZED
WITHIN THIS LAYER. AND WHILE THERE DOES APPEAR TO BE DECENT F-GEN
OVER THE AREA...MODELS ARENT TOO CRAZY ABOUT ANY POTENTIAL
INSTABILITY SO THE BANDING POTENTIAL RIGHT NOW DOESNT APPEAR
GREAT. NOT SURE WE WOULD REACH 6 INCH/12 HR OR 8 INCH/24 HR
CRITERIA FOR A WATCH/WARNING BUT WITH AN EXTENDED PERIOD OF
SNOW...FAR SOUTHERN COUNTIES COULD CERTAINLY PUSH 6 INCHES OF SNOW
STORM TOTAL. WITH SNOW STARTING FOURTH PERIOD...WILL NOT BE
ISSUING ANY HEADLINES YET. BUMPED UP SNOW TOTALS SOUTH OF I-80
SLIGHTLY BUT MADE LESS CHANGES NORTH WHERE TOTALS MAY END UP BEING
HIGH...ESPECIALLY IF WE SEE A SHARP CUTOFF ON THE NORTH SIDE AS WE
HAVE IN OTHER EVENTS THIS SEASON.

TRANSIENT AREA OF HIGH PRESSURE WILL BRING A BRIEF RESPITE FROM THE
PRECIPITATION MONDAY...THOUGH ATTENTION TURNS BACK TO THE WEST AS
SHARP TROUGHING OVER THE WEST COAST INCHES EAST ACROSS THE
INTERMOUNTAIN WEST WITH DOWNSTREAM AMPLIFICATION OF THE MID LEVEL
RIDGE. WARM/MOIST ADVECTION RAMPS UP INTO THE MID MISSISSIPPI
VALLEY...ESPECIALLY MONDAY NIGHT INTO EARLY TUESDAY. WHILE SOME
DISCREPANCIES IN THE DETAILS...THERMAL RIDGE IS PROGGED TO PUSH
ACROSS NORTHERN ILLINOIS ON TUESDAY WITH H85 TEMPS WARMING TO
AROUND +5-7C. STRENGTHENING JET STREAM AND A MID LEVEL WAVE
EJECTING AHEAD OF THE MAIN UPPER TROUGH WILL RESULT IN A DEEPENING
SURFACE LOW OVER THE PLAINS INTO THE MIDWEST. A 50-60KT LOW LEVEL
JET AHEAD OF THE LOW WILL TRANSPORT 1.0+ INCH PWATS //99TH
PERCENTILE// INTO CENTRAL AND NORTHERN ILLINOIS. PRECIPITATION
WILL BEGIN VERY EARLY TUESDAY...AND WHILE THERE MAY BE P-TYPE
ISSUES AT THE ONSET...EXPECT MUCH OF IT WILL FALL AS RAIN WHICH
COULD RESULT IN HYDRO ISSUES WITH MELTING SNOW PACK. THIS IS A
VERY DYNAMIC SYSTEM AND COULD EVEN SUPPORT SOME UPRIGHT
INSTABILITY ROOTED AROUND 850MB. SHOULD THE CURRENT TRACK VERIFY
MAY HAVE TO ADD THUNDER MENTION IN THE SOUTH. DESPITE THE BRIEF
WARM-UP INTO THE UPPER 30S TO LOWER 40S TUESDAY...COLDER AIR WILL
START TO FILTER BACK IN BEHIND THE SYSTEM MIDWEEK WITH SINGLE
DIGIT LOWS ONCE AGAIN THURSDAY AND FRIDAY MORNINGS.

DEUBELBEISS

&&

.CLIMATE...

TEMPERATURES ARE FORECAST ONCE AGAIN TO BE CLOSE OR BREAK THE
FOLLOWING DAILY RECORDS THROUGH THE END OF THE MONTH...INCLUDING
ONE ON FRIDAY IN ROCKFORD THAT WAS SET JUST LAST WINTER:

ROCKFORD...

FRIDAY FEB 27TH LOW MAXIMUM: 15 IN 2014
SATURDAY FEB 28TH LOW: -7 IN 1962
SATURDAY FEB 28TH LOW MAXIMUM: 17 IN 1962

CHICAGO...

FRIDAY FEB 27TH LOW: -6 IN 1897
SATURDAY FEB 28TH LOW: 0 IN 1884

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* NONE.

RODRIGUEZ

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

HIGH PRESSURE SPANNING THE REGION WILL DRIFT EAST TODAY THROUGH
TONIGHT...THEN DEPART TO THE EAST ON SATURDAY. WITH THIS IN
PLACE QUIET CONDITIONS AND MAINLY CLEAR SKIES WILL
PREVAIL...OUTSIDE OF A FEW PASSING HIGH CLOUDS. CLOUD COVERAGE
WILL INCREASE LATE IN THE FORECAST PERIOD OUT AHEAD OF AN
APPROACHING SYSTEM...BUT REMAIN VFR.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH FOR ALL ELEMENTS.

RODRIGUEZ

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

SATURDAY NIGHT...SNOW DEVELOPING OVERNIGHT. IFR LIKELY BY MORNING.

SUNDAY...PERIODS OF SNOW ACCUMULATING SNOW ENDING BY EVENING. IFR
LIKELY.

MONDAY...VFR THEN CHANCE OF WINTRY MIX AND IFR MONDAY NIGHT.

TUESDAY...WINTRY MIX CHANGING TO RAIN BY AFTERNOON...THEN POSSIBLY
ENDING AS LIGHT SNOW TUESDAY NIGHT. IFR.

WEDNESDAY...MVFR POSSIBLE.

THURSDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
157 PM CST

LARGE HIGH PRESSURE SITUATED JUST SOUTH OF THE LAKE THIS AFTERNOON
WHILE LOW PRESSURE IS OVER HUDSON BAY. THIS IS ALLOWING FOR
GENERALLY WESTERLY WINDS OVER THE LAKE IN THE 10 TO 20 KT RANGE.
THIS HIGH WILL SLIDE TO THE EAST TONIGHT INTO SATURDAY...WITH
WINDS BECOMING MORE SOUTHWEST OVERNIGHT AND WHILE WINDS SLIGHTLY
INCREASE TO THE 15 TO 25 KT RANGE FOR A BRIEF PERIOD. A PERIOD OF
SOUTHERLY WINDS WILL OCCUR ON SATURDAY AND SATURDAY NIGHT WITH 10
TO 20 KT RANGE INCREASING BACK UP TO THE 15 TO 25 KT RANGE.
GENERALLY LIGHTER FLOW EXPECTED OVER THE LAKE TO END THE
WEEKEND...BEFORE WINDS INCREASE ONCE AGAIN OUT OF THE
WEST/NORTHWEST SUNDAY NIGHT INTO MONDAY.

RODRIGUEZ

&&

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

$$

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