Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 052204
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
404 PM CST THU MAR 5 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 CELISUS 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 22Z...

* STRONG/GUSTY SOUTHWEST WINDS FRIDAY. CMS

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

HIGH PRESSURE IS CENTERED OVER THE MIDDLE MISSISSIPPI VALLEY WILL
CONTINUE TO SAG SOUTHEAST TO THE OHIO VALLEY BY THIS EVENING. NWLY
WINDS OCNL GUSTING TO 18-20KT WILL SLOWLY BACK TO WLY THIS EVENING
WHILE DIMINISHING TO 5-7KT. AS THE HIGH CONTINUES TO SAG TO THE
UPPER OHIO VALLEY TO LOWER MISSISSIPPI VALLEY TOMORROW AS WEAK
TROUGHING DEVELOPS OVER THE NRN PLAINS. WINDS WILL THE BECOME SWLY
TOMORROW...BUT WITH A STRENGTHENING PRESSURE GRADIENT AND AMPLE
SUNSHINE FOR DEEP LAYER MIXING...GUSTING TO 20-25KT IS EXPECTED
FROM LATE MORNING THROUGH THE AFTERNOON. VFR CONDITIONS WILL
PREVAIL THROUGH THE PERIOD AS HIGH PRESSURE REMAINS THE DOMINANT
FEATURE OVER THE REGION.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

FRIDAY NIGHT THROUGH WEDNESDAY...PRIMARILY VFR.

BMD

&&

.MARINE...
147 PM CST

HIGH PRESSURE REMAINS CENTERED OVER THE OHIO VALLEY THIS
EVENING...BUT WILL DRIFT EAST OVERNIGHT AND SETTLE ACROSS THE
SOUTHEASTERN STATES THROUGH THE WEEKEND. FLOW ACROSS THE LAKE WILL
REMAIN GENERALLY FROM THE WEST TO SOUTHWEST...WITH A SLIGHTLY
BETTER GRADIENT ACROSS THE NORTHERN HALF OF THE LAKE. THE GRADIENT
IS POISED TO INCREASE FRIDAY MORNING WITH THE APPROACH OF A LOW
PRESSURE SYSTEM INTO THE WESTERN GREAT LAKES AND THE DEPARTURE OF
A SURFACE RIDGE TO THE SOUTHEAST. WINDS WILL BE NUDGING UP FRIDAY
WITH WINDS APPROACHING 30KT...AND POSSIBLY A FEW GALE FORCE GUSTS
FRI MIDDAY THROUGH EARLY EVENING. THE WINDS WILL DIMINISH
SATURDAY MORNING...THEN WITH A SERIES OF WEAK LOW PRESSURE SYSTEMS
POISED TO MOVE ACROSS OVER THE NEXT SEVERAL DAYS WITH FLOW MAINLY
FROM THE WEST TO SOUTHWEST.

BEACHLER

&&

.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.

&&

$$

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