Area Forecast Discussion
Issued by NWS Chicago, IL

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KLOT 250855
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
355 AM CDT WED MAR 25 2015

.SHORT TERM...
309 AM CDT

THROUGH TONIGHT...
EARLY THIS MORNING RAIN HAD OVERSPREAD THE FORECAST AREA AND WILL
CONTINUE UNTIL PRIOR TO DAYBREAK. THE SFC LOW WAS LIFTING
NORTHEAST ACROSS THE SOUTHERN CWFA...AND GUIDANCE CONTINUES TO
SLIDE THE LOW ACROSS GARY AROUND 12Z AND FURTHER NORTHEAST BY MID-
MORNING. AS THE LOW LIFTS OVERHEAD...WINDS WILL BRIEFLY DIMINISH.
THEN WINDS ARE PROGGED TO VEER SOUTHWESTERLY AND THE GRADIENT WILL
STEADILY INCREASE. BY LATE MORNING WINDS WILL CONTINUE TO TURN
WEST...THEN SLOWLY DIMINISH AS THE GRADIENT SLACKENS LATE THIS
AFTERNOON.

SURFACE TEMPS WILL SLOWLY CLIMB THIS MORNING...AND TEMPS THIS
AFTERNOON MAY BE A CHALLENGE. GUIDANCE HAS CONTINUED TO POINT
TOWARDS A WARM THERMAL RIDGE ARRIVING MIDDAY AND PUSHING SFC TEMPS
INTO THE LOW/MID 50S TO ARND 60 IN THE FAR SOUTH. THIS WILL HINGE
UPON CLOUD COVER...WHICH COULD LINGER LONGER AS A RESULT OF THE LACK
OF MIXING IN THE LOW LEVELS. THIS WOULD RESULT IN COOLER TEMPS.

TEH MID-LVL FLOW REMAINS PROGRESSIVE THIS AFTERNOON/EVENING...AS YET
ANOTHER SFC WAVE ACROSS THE SOUTHERN PLAINS BEGINS TO DEVELOP. THIS
SECOND LOW WILL FUNNEL A CHANNEL OF MOISTURE NORTHEAST ALONG A
FRONTAL BOUNDARY...WITH SOME LIFT DEVELOPING WITHIN THE BOUNDARY.
THIS MAY BE ABLE TO DEVELOP SOME LIGHT PRECIP LATE THIS AFTN/EVE FOR
THE CENTRAL/SOUTHERN CWFA. AT THIS TIME FEEL THIS WILL LIKELY HOLD
OFF UNTIL CLOSER TO 00Z. THE 500MB TROUGH AXIS WILL BEGIN TO PIVOT
EAST THIS EVENING...ALLOWING THE SOUTHERN SFC LOW TO LIFT NORTHEAST
INTO THE TENN VALLEY LATE TONIGHT. GUIDANCE CONTINUES TO PAINT A
SLUG OF PRECIP ACROSS THE SOUTHERN CWFA WITH THE FRONTAL
BOUNDARY...AND HAVE MAINTAINED POPS IN THIS AREA TONIGHT.

BY DAYBREAK THUR THE PRECIP SHUD BE PUSHING EAST OF THE FORECAST
AREA...WITH ANTI-CYCLONIC FLOW BEGINNING TO DRY THE WESTERN FORECAST
AREA AS COLDER AIR RETURNS. OVERNIGHT LOWS WILL LIKELY REMAIN IN THE
LOW/MID 30S...HOWEVER IF THE FRONTAL BOUNDARY FORWARD SPEED
INCREASES TEMPS MAY BE ABLE TO QUICKLY COOL INTO THE UPR 20S.

BEACHLER

&&

.LONG TERM...
354 AM CDT

THURSDAY THROUGH TUESDAY...

UPPER LEVEL RIDGING IS EXPECTED TO BUILD SIGNIFICANTLY
ACROSS THE WESTERN CONUS TODAY THROUGH THURSDAY IN RESPONSE TO
SIGNIFICANT DISTURBANCE ACROSS THE THE NORTHERN PACIFIC.  ULTIMATELY
THIS WILL SET THE STAGE FOR WELL BELOW AVERAGE HEIGHTS AND A DEEPER
COLD AIRMASS TO TAKE CONTROL OF THE EASTERN HALF OF THE COUNTRY FOR
A FEW DAYS INTO THE WEEKEND. THEREFORE...THE MAIN WEATHER STORY
DURING THE PERIOD WILL BE THE TRANSITION BACK TO A MUCH BELOW
AVERAGE WEATHER PATTERN THROUGH AT LEAST THE FIRST HALF OF THE
WEEKEND.

THE HEART OF THIS COLD AIRMASS IS SET TO BEGIN TO SHIFT SOUTHWARD
OVER THE AREA THURSDAY NIGHT INTO FRIDAY AS ANOTHER COLD FRONT
SHIFTS DOWN THE WESTERN GREAT LAKES. IT STILL APPEARS THAT THERE
COULD BE SOME SNOW SHOWERS ACROSS PORTIONS OF THE REGION THURSDAY
NIGHT INTO EARLY FRIDAY MORNING AS THIS COLD AIR SPILLS OVER THE
AREA. LOW LEVEL LAPSE RATES LOOK TO STEEPEN CONSIDERABLY WITH THE
COLD AIRMASS...AND THIS COMBINED WITH THE APPROACH OF A ANOTHER
UPPER LEVEL DISTURBANCE DIGGING INTO THE BASE OF THE LARGER SCALE
TROUGH OVER THE EASTERN HALF OF THE COUNTRY...COULD RESULT IN SOME
MINOR ACCUMULATIONS OF SNOW OVER PORTIONS OF NORTHEASTERN
ILLINOIS/NORTHWESTERN INDIANA. OTHERWISE...WITH 925 MB TEMPERATURES
PROGGED TO ONLY BE -8 TO -10 DEGREES CELSIUS OVER THE
AREA...AFTERNOON HIGHS WILL LIKELY REMAIN IN THE LOW TO MID 30S AT
BEST...WITH SOME AREAS LIKELY NOT TO BREAK THE FREEZING POINT.

LATE FRIDAY NIGHT INTO SATURDAY MORNING THE CENTER OF A COLD 1030 MB
SURFACE HIGH IS SET TO MOVE OVERHEAD. LIGHT WINDS AND CLEAR SKIES
UNDER THIS HIGH WILL LIKELY ALLOW TEMPERATURES TO DROP INTO THE
TEENS...WITH LOWER TEENS POSSIBLE IN THE USUAL COLD SPOTS OF
NORTHERN ILLINOIS. SATURDAY LOOKS TO BE SUNNY ACROSS THE
REGION...BUT WITH THE COLD AIRMASS STILL IN PLACE SURFACE
TEMPERATURES ONLY LOOK TO GET INTO THE UPPER 30S...TO POSSIBLY NEAR
40 IN MY FAR WEST.

A SIGNIFICANT NORTHERN PACIFIC WAVE IS FORECAST TO SHIFT EASTWARD
ONSHORE ACROSS THE PACIFIC NORTHWEST BY SATURDAY MORNING...THEN
CONTINUE EASTWARD...WEAKENING THE AMPLITUDE OF THE WESTERN CONUS
RIDGE AS IS MOVES ACROSS THE NORTHERN ROCKIES LATE SATURDAY. THIS
WAVE IS FORECAST TO MOVE TOWARDS THE WESTERN GREATS LAKES REGION BY
SUNDAY EVENING. AN ASSOCIATED SURFACE LOW LOOKS TO TRACK EASTWARD
ACROSS FAR SOUTHERN CANADA THROUGH SUNDAY. THIS SYSTEM COULD RESULT
IN SOME STRONG GUSTY SOUTHWESTERLY WINDS SUNDAY AS THE SURFACE
GRADIENT STRENGTHENS BETWEEN THIS LOW AND THE EXITING SURFACE RIDGE
MOVING OVER THE SOUTHEASTERN CONUS. WARM AIR ADVECTION SHOULD SET
UP WITH THIS PATTERN...SO WARMING CONDITIONS ARE EXPECTED.
HOWEVER...THIS ALSO COULD RESULT IN SOME PRECIPITATION OVER THE AREA
SUNDAY...ESPECIALLY IF THE MAIN MID LEVEL PV ANOMALY TRACKS OVER
NORTHERN ILLINOIS AND WISCONSIN. THE MODEL GUIDANCE HAS COME IN A
BIT COOLER...SO IT STILL LOOKS AS THOUGH TEMPERATURES SUNDAY COULD
REMAIN AT LEAST A FEW DEGREES BELOW AVERAGE.

WARMER CONDITIONS LOOK TO RETURN NEXT WEEK AS THE STORM TRACK LOOKS
TO FAVOR SYSTEMS TRACKING EASTWARD ACROSS THE NORTHERN CONUS.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* RAIN WILL REDUCE VSBY/CIGS TO MVFR CONDS.

* CIGS EXPECTED TO LOWER TOWARDS IFR CONDS AFT 7Z THRU DAYBREAK.

* WINDS VEERING SOUTH TO WEST BY MID-MORNING. SPEEDS WILL DECREASE
  BRIEFLY...THEN QUICKLY INCREASE MID-MORNING WITH GUSTS BETWEEN
  20-25KT.

BEACHLER

//DISCUSSION...UPDATED 06Z...

REGIONAL RADAR SHOWS AN AREA OF PRECIP LIFTING NORTHEAST ACROSS
THE TAF SITES EARLY THIS MORNING...WITH A FEW BREAKS WITHIN THE
PRECIP SHIELD. LIGHTNING HAS BEEN INDICATED SOUTH OF THE TAF
SITES...AND EXPECT THIS TO REMAIN SOUTH THROUGH THE DURATION. CIGS
AT ORD/MDW HAVE REMAINED VFR...HOWEVER JUST SOUTHWEST OF THE
TERMINALS IFR CIGS HAVE ALREADY DEVELOPED AND EXPECT BY 8Z IFR
CIGS TO BE OVER ORD/MDW. SO A QUICK REDUCTION WILL OCCUR AS
STEADIER RAIN ARRIVES. WINDS WILL BRIEFLY DIMINISH AS THE LOW
LIFTS OVERHEAD EARLY THIS MORNING...THEN SOUTHEASTERLY WINDS WILL
QUICKLY VEER SOUTHWEST TO WEST BY MID-MORNING...AND BEGIN TO
INCREASE. GUSTS WILL REDEVELOP BY MID-MORNING BETWEEN 20-25KT.

PRECIP SHOULD LIFT NORTHEAST OF THE TAF SITES BY DAYBREAK...WITH
MOST OF THE DAY BECOMING DRY. GUIDANCE CONTINUES TO INDICATE MVFR
CIGS WILL LINGER THRU THIS MORNING AND AFTN HOURS. ALTHOUGH IT IS
POSSIBLE ENOUGH MIXING WILL HELP TO LIFT THE CIGS UP TO VFR CONDS
BY MIDDAY. THEN ANOTHER NARROW CHANNEL OF MOISTURE STREAMS EAST
ACORSS THE AREA LATE THIS EVENING...AND COULD BRING SOME LIGHT
PRECIP TO THE AREA WITH A FRONTAL BOUNDARY PASSAGE EARLY THUR
MORNING.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE IN RAIN THROUGH 10Z...MEDIUM/HIGH CONFIDENCE IN
  RAIN ENDING BY 11Z.

* HIGH CONFIDENCE IN CIGS LOWERING TO IFR CONDS BY 8Z...MEDIUM
  CONFIDENCE ON WHEN CIGS WILL LIFT BACK TO MVFR.

* HIGH CONFIDENCE IN WIND DIR/SPEED/GUSTS FORECAST.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...

THURSDAY...CHANCE OF SNOW SHOWERS OVERNIGHT. MVFR CIGS/VIS
POSSIBLE.

FRIDAY...VFR. WX NIL.

SATURDAY...VFR. WX NIL.

SUNDAY...CHANCE RAIN THROUGH THE DAY...POSSIBLY MIXING WITH SNOW
EARLY. MVFR CIGS/VIS POSSIBLE.

MONDAY...VFR. WX NIL.

KREIN

&&

.MARINE...
212 PM CDT

GENERALLY LIGHT EAST SOUTHEAST WINDS IN PLACE THIS AFTERNOON AS
HIGH PRESSURE IS SITUATED JUST TO THE EAST OF THE LAKE. TWO
SYSTEMS WILL MOVE EAST AND NORTHEAST TOWARDS LAKE MICHIGAN TONIGHT
WITH THE SOUTHERN SYSTEM HELPING TO INCREASE WINDS TO AROUND 30 KT
THIS EVENING. THE STRONGEST WINDS WILL LIKELY BE ACROSS THE
SOUTHERN HALF OF THE LAKE THIS EVENING INTO EARLY WEDNESDAY AS
THIS SYSTEM MOVES THROUGH THE SOUTHERN HALF OF THE LAKE. BOTH THE
NEARSHORE AND OPEN WATERS WILL BOTH OBSERVE THESE 30 KT
WINDS...WITH A PERIOD OF GALE FORCE GUSTS TO 35 KT STILL POSSIBLE
AS WELL. HAVE NOT ISSUED ANY GALE HEADLINES AT THIS TIME WITH THE
PREVAILING CONDITIONS APPEARING TO BE AROUND 30 KT AND WITH THE
DURATION OF THESE GALE FORCE GUSTS LIKELY REMAINING IN THE 4-6
HOUR TIME FRAME...BUT WILL CONTINUE TO MAKE MENTION OF THIS
POSSIBILITY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 PM WEDNESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.