Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 161750
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1250 PM CDT THU APR 16 2015

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND FRIDAY
ISSUED AT 257 AM CDT THU APR 16 2015

THE LATEST RAP ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW HIGH
PRESSURE CENTERED OVER THE EAST COAST...BUT WITH A RIDGE AXIS
EXTENDING WEST TO THE WESTERN GREAT LAKES.  VERY DRY AIR CONTINUES TO
HOLD ON ACROSS THE REGION...AND DEWPOINTS HAVE STRUGGLED TO RECOVER
OVER CENTRAL AND NORTH-CENTRAL WISCONSIN OVERNIGHT.  SOUTHEAST LOW
LEVEL FLOW OVER THE SOUTHERN GREAT LAKES IS SLOWLY VEERING TO MORE
OF A SOUTHERLY DIRECTION...BUT IS STILL TRYING TO PUSH LIGHT SHOWER
ACTIVITY ACROSS SOUTH-CENTRAL LAKE MICHIGAN. THIS IS AHEAD OF A
SHORTWAVE OVER THE IL/IN BORDER.  THE BONE DRY AIRMASS AND VEERING
FLOW IS NOT HELPING THESE SHOWERS TO MAKE A WESTWARD JAUNT...AND THE
LATEST MESOMODELS KEEP THESE SHOWERS EAST OF THE MANITOWOC SHORELINE
EARLY THIS MORNING.  THIS SHOWER ACTIVITY ALONG WITH FIRE WEATHER
CONDITIONS ARE THE MAIN FORECAST CONCERNS IN THE SHORT TERM.

TODAY...THE SHORTWAVE OVER THE IL/IN BORDER WILL LIFT NE THIS
MORNING AND THEN EAST THIS AFTERNOON AS RIDGING OVER THE GREAT LAKES
FLATTENS.  850MB FLOW WILL CONTINUE TO VERY GRADUALLY VEER THIS
MORNING WHICH COMBINED WITH THE VERY DRY AIR ACROSS THE REGION WILL
GIVE THE LIGHT SHOWER ACTIVITY OVER SOUTHERN LAKE MICHIGAN A SUBTLE
PUSH TO THE EAST. SO WILL KEEP THE DRY FORECAST IN TACT...BUT WILL
INCREASE CLOUD COVER OVER EAST-CENTRAL WISCONSIN TODAY AS 5K-6KFT
CLOUDS OVER NORTHERN ILLINOIS WILL LIKELY ARRIVE THIS MORNING.
ELSEWHERE...A MID-LEVEL DECK OVER MINNESOTA AND IOWA WILL SHIFT TO
THE EAST AND MOVE INTO NORTH-CENTRAL WISCONSIN DURING THE
AFTERNOON.  UNTIL THESE CLOUDS ARRIVE...A POCKET OF VERY DRY AIR
WILL REMAIN IN PLACE ACROSS CENTRAL AND NORTH-CENTRAL WISCONSIN.
MIXING WILL NOT BE AS GOOD TODAY DUE TO LIGHTER WINDS ALOFT...BUT
STILL LOWERED DEWPOINTS SINCE THINK WILL STILL BE ABLE TO TAP INTO
SOME OF THE BONE DRY AIR JUST ABOVE THE INVERSION.  AS A
RESULT...HAVE DROPPED DEWPOINTS AND HUMIDITIES OVER CENTRAL AND
NORTH-CENTRAL WISCONSIN THIS AFTERNOON.  HUMIDITIES COULD FALL
BETWEEN 20-25 PCT.  FORTUNATELY...WINDS WILL BE MUCH LIGHTER
TODAY...SO SHOULD NOT SEE A REPEAT OF THE CRITICAL FIRE WEATHER
CONDITIONS.  HIGHS MAINLY IN THE MID TO UPPER 60S AWAY FROM LAKE
MICHIGAN.

TONIGHT...A COLD FRONT WILL DECAY AS IT MOVES INTO NORTH-CENTRAL
WISCONSIN LATE.  MID-LEVEL CLOUDS WILL CONTINUE TO SPREAD EAST AHEAD
OF THE FRONT...BUT GRADUALLY DISSIPATE IN THE PROCESS.  SHOULD
THEREFORE SEE A PARTLY CLOUDY TO MOSTLY CLEAR NIGHT. WITH THE
THINNING CLOUDS...DO NOT THINK THERE WILL BE A DEEP ENOUGH CLOUD
LAYER FOR SPRINKLES OR LIGHT SHOWERS.  LOWS MAINLY IN THE LOW TO MID
40S.

FRIDAY...THE FRONT WILL WASH OUT ACROSS NORTHERN WISCONSIN.  MAY SEE
SOME CU DEVELOP OVER CENTRAL AND EAST-CENTRAL WISCONSIN DURING THE
AFTERNOON...BUT THE NORTH SHOULD SEE AN INFLUX OF DRY AIR...THAT
WILL DROP HUMIDITIES NEAR 25 PCT IN THE AFTERNOON.  HIGHS WILL BE
WARMER THAN TODAYS READINGS...AND RAISED THEM INTO THE UPPER 60S
NORTH TO MID 70S SOUTH.

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY
ISSUED AT 257 AM CDT THU APR 16 2015

DRY CONDITIONS WILL CONTINUE FRIDAY NIGHT AND SATURDAY AS CANADIAN
HIGH PRESSURE BUILDS INTO THE STATE. NORTHWEST WINDS WILL TURN
TO THE EAST AND NORTHEAST LATE FRIDAY NIGHT AND SATURDAY. SATURDAY
AFTERNOON WILL AGAIN FEATURE VERY LOW AFTERNOON RELATIVE HUMIDITY
READINGS AWAY FROM THE LAKE...WITH READINGS DROPPING INTO THE 20
TO 40 PERCENT RANGE WITH THE LOWEST READINGS NORTH AND WEST OF THE
FOX VALLEY.

MEANWHILE...CLOSED UPPER LOW ACROSS THE CENTRAL PLAINS IS EXPECTED
TO OPEN UP AS 500MB TROUGH ACROSS SOUTHERN CANADA WILL BEGIN TO
LIFT THE SOUTHERN SYSTEM NORTHEAST TOWARDS THE REGION. QUIET A
SPREAD IN THE MODELS ON HOW QUICK THE RAIN WILL ARRIVE OVER THE
WEEKEND. THE WRF MODELS WAS QUICKEST...ALREADY BRINGING RAIN ON
SATURDAY TO PORTIONS OF THE AREA. THE GFS MODEL WAS IN THE MIDDLE
OF THE ROAD SOLUTION...WHILE THE CANADIAN/ECMWF MODEL WERE THE SLOWEST
SOLUTION WITH RAIN ARRIVING ON SUNDAY. TRENDED TOWARD THE SLOWER
SOLUTION FOR THE MEANTIME DUE TO BETTER CONSISTENCY FROM RUN TO
RUN. DID ADD A SMALL CHANCE OF RAIN ACROSS THE WEST LATE SATURDAY
NIGHT...AND THEN BOOSTED RAIN CHANCES INTO THE LIKELY CATEGORY ON
SUNDAY. DID RAISE RAIN CHANCES SUNDAY NIGHT AS WELL. THE 500MB
SYSTEMS WILL MERGE INTO A CLOSED UPPER LOW ACROSS THE UPPER
MIDWEST AND WESTERN GREAT LAKES REGION EARLY NEXT WEEK. THIS
WOULD SUPPORT A COOLER AND UNSETTLED PATTERN ACROSS THE REGION
ON MONDAY THROUGH WEDNESDAY. HAVE CHANCES OF SHOWERS EACH PERIOD...
ALONG WITH A LITTLE SNOW LATE AT NIGHT INTO THE EARLY MORNING
HOURS ON TUESDAY AND WEDNESDAY. IT IS WISCONSIN! TEMPERATURES
BY EARLY NEXT WEEK WILL RUN WELL BELOW NORMAL.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1250 PM CDT THU APR 16 2015

VFR CONDITIONS SHOULD PREVAIL THROUGH AT LEAST FRIDAY MORNING.
A CLOUD DECK BELOW 1KFT MOVED INTO THE SOUTHEAST PART OF THE AREA
THIS MORNING BUT MOVED OVER LAKE MICHIGAN BY 17Z. RADAR SHOWED SOME
ECHOES ACROSS PARTS OF CENTRAL/NORTH CENTRAL WISCONSIN DRIFTING TO
THE EAST BUT THEY WERE SCATTERED...SURFACE DEW POINT DEPRESSIONS
WERE IN EXCESS OF 30F...AND MOST OF THE SURFACE OBSERVATIONS IN
THAT PART OF THE STATE DID NOT EVEN INDICATE ANY CLOUDS. MODEL
TIME SECTIONS SHOWED A MOIST LAYER OVERNIGHT IN THE 5KFT-10KFT
RANGE...WITH DECREASING RH IN THAT LAYER AROUND 12Z. THE SURFACE
PRESSURE GRADIENT IS NOT EXPECTED TO BE TIGHT...SO WINDS SHOULD
REMAIN LIGHT.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....MPC
LONG TERM......ECKBERG
AVIATION.......MG





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