Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 281719
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1219 PM CDT SUN SEP 28 2014

.SYNOPSIS...
ISSUED AT 312 AM CDT SUN SEP 28 2014

LATEST SFC ANALYSIS WAS INDICATING RIDGE AXIS EXTENDING FROM THE
CENTRAL GRT LKS DOWN INTO THE SOUTHEASTERN PLAINS...WITH COOL
FRONTAL BOUNDARY DRAPED ON IT/S NORTHWESTERN FLANK FROM THE CENTRAL
ROCKIES...UP ACRS THE DAKOTAS AND REACHING TO THE NORTHEAST TO THE
JAMES BAY REGION. THIS FRONT CURRENTLY BEING HELD UP BY THE RIDGE TO
THE SOUTHEAST OF IT...BUT A L/W TROF SEEN PUSHING ACRS CENTRAL
CANADA WILL EVENTUALLY PROVIDE A BOOST LATE TONIGHT INTO MONDAY.
CLOSED OFF/BLOCKED UPPER LOW CENTERED ACRS NORTHWESTERN IA
ATTM...WILL LOOK TO OPEN UP AND GET SHUNTED TO THE EAST TODAY AND
TONIGHT ALSO BEING EFFECTED BY THE APPROACHING NORTHERN STREAM UPPER
TROF. OTHER LARGE CUT-OFF UPPER LOW WAS SEEN SPIRALING ON WATER VAPOR
IMAGERY ACRS EASTERN CA INTO NV...WAITING FOR UPSTREAM GULF OF AK
UPPER WAVE ENERGY FOR LARGE SCALE PHASING PROCESS TO COMMENCE EARLY
THIS UPCOMING WEEK.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 312 AM CDT SUN SEP 28 2014

TODAY...MORE OF THE SAME AND WILL PLAY PERSISTENCE CARD TODAY WITH
LLVL RIDGE BEING THE MAIN INFLUENCE OF THE REGION/S WX. MAINLY
SUNNY WITH JUST PATCHY AC...STREAMS OF CI OR HIGHER BASED CU MOVING
ACRS THE AREA. AIR MASS LARGELY UNCHANGED AND WILL GO SIMILAR HIGHS
AS YESTERDAY...ONGOING FCST PACKAGE ALREADY HANDLING PERSISTENCE
AND WILL KEEP THE ADVERTISED HIGH TEMPS/MOST OF THE CWA IN THE 80-
84 DEGREE RANGE/. BUT WITH THE RIDGE AXIS OVERHEAD AND INHERENT
WEAKER MIXING PROFILES WOULD NOT BE SURPRISED IF SOME AREAS HELD TO
THE UPPER 70S. SFC LAYER CONTINUES TO DRY AND LARGE DIURNAL RH DROPS
BY AFTERNOON. LIGHT AND VARIABLE SFC WIND REGIME CONTINUES.

TONIGHT...MAINLY CLEAR OR JUST PATCHY PASSING HIGH CLOUDS. LIGHT AND
VARIABLE OR CALM WINDS AGAIN TO ALLOW FOR TEMPS TO TUMBLE WELL DOWN
INTO THE 50S...LARGE DIURNAL SWINGS CONTINUE. THESE SAME CONDITIONS
TO FOSTER ANOTHER NIGHT OF VALLEY FOG OR PATCHY GROUND FOG IN LOW
LYING LOCATIONS. THE UPSTREAM SFC FRONT CURRENTLY ACRS THE NORTHERN
PLAINS AND ONTARIO TO MAKE SOME PUSH SOUTHEASTWARD ACRS SOUTHERN MN
INTO NORTH CENTRAL WI BY MON MORNING...BUT WILL NOT HAVE ANY IMPACT
ON THE LOCAL FCST AREA IN THE SHORT TERM.    ..12..

.LONG TERM...(MONDAY THROUGH NEXT SATURDAY)
ISSUED AT 312 AM CDT SUN SEP 28 2014

A LARGELY PERSISTENCE BASED FORECAST WILL BE JUSTIFIED AGAIN FOR
MONDAY...THEN A MORE CHANGEABLE WEATHER PATTERN WILL SET
IN...ESPECIALLY AROUND MID TO LATE WEEK. THE BIGGEST CHANGE IN THE
THE FORECAST FOR EARLY IN THE WEEK IS THE STRONGER UPPER LEVEL WAVE
SYSTEM THE LATEST MODEL RUNS HAVE DROPPING SOUTHEAST THROUGH THE
GREAT LAKES. THIS IS SHOWN PUSHING A WEAK BACKDOOR FRONT SOUTH INTO
THE AREA MONDAY NIGHT...WHICH THEN WASHES OUT TUESDAY. THE GFS AND
ECMWF FIRE OFF LIGHT PRECIPITATION BEHIND THE FRONT...POSSIBLY AS
FAR SOUTH AS THE HIGHWAY 20 CORRIDOR TUESDAY NIGHT. HOWEVER...WILL
MAINTAIN A DRY FORECAST UNTIL CONFIDENCE INCREASES AS BOTH MOISTURE
AND FORCING APPEAR QUESTIONABLE. THE MAIN IMPACT WILL BE COOLER
TEMPERATURES AND LOWER DEWPOINTS THAT MAY LIMIT TUESDAY HIGHS TO
AROUND 70 NORTH AND NORTHEAST...WHILE THE SOUTH REACHES AT LEAST
THE UPPER 70S AFTER ANOTHER NIGHT IN THE 50S.

TUE NIGHT INTO WEDNESDAY...THE FIRST SHORTWAVE EMBEDDED IN THE
DEVELOPING SW FLOW ALOFT WILL SEND A SURFACE SYSTEM NORTHEAST THROUGH
THE PLAINS. THE RESULTING WARM AIR ADVECTION AND MOISTURE RETURN
INTO THE LOCAL AREA WILL SUPPORT AT LEAST SCATTERED SHOWERS AND
THUNDERSTORMS FROM LATE WED INTO WED NIGHT. MODELS CONTINUE TO BACK
OFF SOME ON THE POTENTIAL FOR CONVECTION LATE TUE NIGHT...
AND HAVE FURTHER LOWERED POPS IN THE WEST.

THE MAIN UPPER TROUGH PASSES THROUGH THU INTO THU NIGHT...WITH
DIVERSE MODEL SOLUTIONS IN THE 00Z RUNS LENDING A LOW CONFIDENCE
FORECAST. THE GFS IS MOST BULLISH WITH A MORE CLOSED ALOFT AND
RESULTING DEEPER SURFACE LOW SHOWN SWEEPING OVER THE FORECAST AREA
LATE THU...WHILE THE ECMWF AND CANADIAN HAVE A MORE OPEN SYSTEM
ALOFT AND LACK AN ORGANIZED SURFACE LOW. MODEL CONSENSUS STILL
SUPPORTS HIGH CHANCE TO LIKELY POPS FOR RAIN AND AT LEAST ISOLATED
THUNDERSTORMS FOR WED NIGHT THROUGH THU NIGHT WHEN GULF MOISTURE
WILL BE IN PLACE AS THE FORCING MOVES THROUGH. THERE IS CONSENSUS
SHOWING THE SYSTEM SWEEPING TO THE EAST FRIDAY WITH STRONG COLD
ADVECTION SETTING UP...BUT POOR AGREEMENT WITH A POSSIBLE TRAILING
VORT THAT WILL REQUIRE AT LEAST CHANCE POPS FOR SHOWERS. THE LATEST 00Z
GFS AND CANADIAN MODELS HAVE THE 850 MB ZERO LINE REACHING INTO THE
NORTH BY EVENING...WHILE THE ECMWF IS SEVERAL DEGREES WARMER...OR
SLOWER WITH THE COLD ADVECTION. IF LATER RUNS TREND TOWARD THE
COLDER SOLUTIONS...OUR CURRENT FORECAST HIGHS IN THE 60S FOR FRIDAY
AND UPPER 50S TO LOWER 60S FOR SATURDAY WOULD BE TOO WARM. IN FACT
IF THE MORE AMPLIFIED GFS SOLUTION WERE TO VERIFY...TEMPERATURES
SATURDAY WOULD NOT LIKELY MAKE IT OUT OF THE 40S WITH LOWS MORE
LIKELY IN THE 30S VERSUS THE 40S MAINTAINED IN THE LATEST FORECAST.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1211 PM CDT SUN SEP 28 2014

HIGH PRESSURE WILL CONTINUE TO PROVIDE VFR CONDITIONS MOST OF THE
TAF CYCLE ALONG WITH LIGHT WINDS. SHALLOW STEEP LOW LEVEL INVERSION
WILL ONCE AGAIN PROMOTE PATCHY FOG WITH MVFR TO LOCAL IFR VSBYS 09Z-
12Z ESPECIALLY IN RIVER VALLEYS.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

SYNOPSIS...12
SHORT TERM...12
LONG TERM...SHEETS
AVIATION...05




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