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 060849
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
249 AM CST FRI MAR 6 2015

.SHORT TERM...
306 PM CST

THROUGH SATURDAY...

THERE ARE NO WEATHER CONCERNS THROUGH THE FORECAST PERIOD...UNLESS
YOU ARE CONCERNED WITH THE ARRIVAL OF MILDER WEATHER. HIGH PRESSURE
OVER THE AREA WILL DRIFT SOUTHEAST TONIGHT BUT NOT BEFORE CLEAR
SKIES AND LIGHT WINDS CONSPIRE TO BRING ONE LAST NIGHT OF NEAR TO
BELOW ZERO TEMPERATURES AWAY FROM CHICAGO. TEMPERATURES SHOULD
STEADY OR SLOWLY RISE OVERNIGHT EXCEPT CLOSER TO THE SFC RIDGE IN
THE SOUTHERN CWA...WHERE TEMPERATURES MAY STILL BE BELOW ZERO
AROUND DAYBREAK.

NORTHWEST FLOW ALOFT WILL REMAIN ON FRIDAY...BUT DOWNSLOPING OF
MILDER AIR FROM HIGH PLAINS WILL SHUNT COLD AIR MASS OFF TO THE
EAST. TIGHT PRESSURE GRADIENT BETWEEN HIGH PRESSURE DEPARTING TO
SOUTHEAST AND LOW PRESSURE TO THE NORTH WILL RESULT IN GUSTY
SOUTHWEST WINDS. SO AFTER CHILLY START TO THE DAY...EXPECTING
HIGHS IN THE UPPER 20S TO LOWER 30S. DID TREND CLOSER TO WARMER
SIDE OF GUIDANCE BASED ON CLIMO OF EXPECTED 850/925 MB TEMPS BY
THE AFTERNOON. WOULD NOT BE TOO SURPRISED IF CHICAGO HEAT ISLAND
TAGS THE MID 30S. MID/UPPER DISTURBANCE WILL BRING PLENTY OF MID
AND HIGH CLOUDS ACROSS THE AREA AND GUSTY WINDS WILL KEEP A RAW
FEEL HOWEVER. STEADY SOUTHWEST WINDS AHEAD OF A WEAK COLD FRONT
WILL KEEP LOWS IN THE 20S FRIDAY NIGHT...THEN THE FRONT WILL CROSS
THE AREA ON SATURDAY. HAVE MAINTAINED A DRY FROPA. 850 MB TEMPS
AND 925 MB TEMPS WITHIN A DEGREE OR SO OF 0 CELSIUS SUPPORT UPPER
30S TO MID 40S FOR HIGHS. THE GLACIAL SNOWPACK SHOULD BEGIN
MELTING IN EARNEST ON SATURDAY AFTER LIKELY SOME MINOR MELTING ON
FRIDAY.

RC

&&

.LONG TERM...
329 PM CST

SATURDAY NIGHT THROUGH THURSDAY...

THE BIG STORY NEXT WEEK WILL BE THE LIKELY SPRING LIKE
TEMPERATURES ON TUESDAY THROUGH THURSDAY. SOME MODEL DIFFERENCES
ON SUNDAY...WITH 12Z ECMWF AND CANADIAN GLOBAL MODEL BRINGING A
CLIPPER TYPE SYSTEM JUST NORTH OF THE CWA AND LIGHT PRECIP TO THE
NORTHERN CWA IN MORNING AND AFTERNOON...WHILE GFS IS SLOWER WITH
WEAK SHORTWAVE ALONG WEAK COLD FRONT DURING THE EVENING. HAVE GONE
AHEAD WITH MAINLY SLIGHT POPS ON SUNDAY. IF PRECIP DOES OCCUR...WET
SNOWFLAKES MAY MIX IN WITH SPOTTY LIGHT RAIN.

COLD AIR WILL BE NON EXISTENT BEHIND THE COLD FRONT AND
PROGRESSIVELY WARMER AIR WILL BE ADVECTED INTO THE AREA THROUGH
MID WEEK NEXT WEEK AROUND PERIPHERY OF EXPANSIVE HIGH PRESSURE TO
OUR SOUTHEAST THAT WILL ALSO KEEP THINGS DRY. 500 MB HEIGHTS WILL
LIKELY APPROACH LATE SPRING LIKE ~570 DM LEVELS BY THURSDAY.
LOOKING AT HIGHS POSSIBLY WELL INTO THE 50S ON TUESDAY AND ON
WEDNESDAY...GLOBAL GUIDANCE PROGGING HIGH SINGLE DIGITS CELSIUS AT
850 MB AND POSSIBLY AROUND OR A BIT OVER 10 CELSIUS AT 925 MB.
SINCE SNOWPACK IS LIKELY TO HAVE BEEN REDUCED TO REMNANT PILES AT
THAT POINT...IT IS CONCEIVABLE THAT HIGHS COULD BE IN THE 60S FOR
MUCH OF THE AREA AS SHOWN ON 12Z ECMWF. FOR NOW...HAVE
CONSERVATIVELY GONE ABOVE GUIDANCE BLEND WITH MID-UPPER 50S HIGHS
ON WEDNESDAY. POTENTIAL EXISTS FOR A BACKDOOR COLD FRONT LATE NEXT
WEEK...BUT IF TIMING IS SLOWER...THURSDAY COULD BE AS WARM AS IF
NOT WARMER THAN WEDNESDAY. DUE TO OVERALL LACK OF PRECIPITATION
EXPECTED WITH COMING WARMUP...SNOW MELT SHOULD BE GRADUAL AND NOT
EXPECTING SIGNIFICANT HYDRO ISSUES...BUT RISES ARE POSSIBLE ON
MORE ICE JAM PRONE RIVERS.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* GUSTY SW WINDS WITH MAX GUSTS UP TO 25 KT IN THE AFTN.

* MVFR CIGS ARE PSBL THIS EVENING.

JEE

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

HIGH PRESSURE IS SLOWLY SHIFTING SOUTHEAST AND WINDS WILL BECOME
SE TO SSE OVERNIGHT. THE GRADIENT TIGHTENS TOMORROW WITH SSE WINDS
GUSTING TO ARND 21 KT BY 14Z. GUSTS INCREASE TO ARND 24 KT BY MID
DAY AS WINDS VEER SLIGHTLY TO SE. A WEAKENING SFC TROUGH AND
BOUNDARY MOVE THROUGH THE REGION FRIDAY EVENING AND A FAIR NUMBER
OF GUIDANCE MEMBERS FEATURE MVFR OR IFR CIGS WITH THE TROUGH. HAVE
LIMITED CONFIDENCE IN THE CIGS AS GUIDANCE CAN BE OVER ZEALOUS
WITH LOW LEVEL MOISTURE...BUT PUT A SCT MVFR CIG IN THE TAF. SE
WINDS DIMINISH TO ARND 10 KT IN THE EVENING.

JEE

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* LOW CONFIDENCE IN MVFR OR LOWER CIGS DEVELOPING FRIDAY EVENING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

* SATURDAY...DRY/VFR. WEST WINDS.
* SUNDAY...SLIGHT CHANCE OF RAIN OR SNOW. SOUTHWEST WINDS.
* MONDAY THRU WEDNESDAY...DRY/VFR. WEST/SOUTHWEST WINDS.

&&

.MARINE...
247 AM CST

EXPECTING WINDS TO PICK UP ON THE BACK SIDE OF THE HIGH THIS
AFTERNOON AS THE HIGH SHIFTS SOUTHEAST.  WILL KEEP THE SMALL CRAFT
ADVISORY AS IS. STILL EXPECTING A FEW HOURS OF GALE FORCE GUSTS OVER
THE NORTH HALF OF THE LAKE THIS AFTERNOON...BUT THE WINDOW SHOULD BE
NARROW ENOUGH WHERE A GALE HEADLINE WILL NOT BE NEEDED. SOUTHWEST
WINDS DIMINISH AS THE GRADIENT WEAKENS AND A WEAK LOW PASSES OVER
THE NORTHERN GREAT LAKES.  WINDS BECOME WEST BEHIND THE LOW SATURDAY
AFTERNOON AND REMAIN WEST THROUGH THE WEEKEND.  SOUTHWEST WINDS
15-25 KT SET UP AHEAD OF THE NEXT LOW MONDAY NIGHT AND TUESDAY...AND
THEN BECOME NORTH BEHIND THE LOW WEDNESDAY NIGHT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM FRIDAY TO 4 AM SATURDAY.

&&

$$

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.