Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 031954
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
254 PM CDT MON AUG 3 2015

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND TUESDAY
ISSUED AT 253 PM CDT MON AUG 3 2015

A LARGE UPPER LEVEL LOW SITUATED NEAR JAMES BAY WILL KEEP A
LINGERING INFLUENCE ON OUR WEATHER EARLY THIS WEEK AS IT SLOWLY
TRACKS EAST. PER WATER VAPOR IMAGERY...A SERIES OF WEAK MID LEVEL
SHORTWAVES ARE MOVING...AND WILL CONTINUE TO MOVE AROUND THE
PERIPHERY OF THE LOW IN CYCLONIC FLOW ACROSS THE NORTHERN FRINGE
OF THE WESTERN GREAT LAKES AREA. COOL MID LEVEL TEMPERATURES AND
STEEP LOW LEVEL LAPSE RATES ARE ALLOWING SHOWERS TO POP UP ACROSS
THE NORTHERN CWA TODAY. THOUGH THE UPPER LOW WILL BE FARTHER AWAY
TOMORROW...AND THE HIGHEST AMOUNT OF MOISTURE LOOKS TO LARGELY
MOVE INTO UPPER MICHIGAN...STILL HAVE SOME LINGERING CHANCES FOR
SHOWERS IN THE NORTHEAST AGAIN TOMORROW. THOUGH A MODIFIED 12Z
SOUNDING FROM GREEN BAY INDICATED SOME VERY MODEST CAPE...HAVE
CONFINED THE POPS TO THE NORTHERN CWA. THERE IS A FAIRLY
SUBSTANTIAL INVERSION AROUND 650 MB WHICH THE MODIFIED SOUNDING
MAY OR MAY NOT BREAK...GIVEN YOUR PREFERENCE FOR SBCAPE OR MLCAPE.
ACTIVITY BOTH TODAY AND TOMORROW IS EXPECTED TO DIMINISH RAPIDLY
AS THE SUN SETS...WITH ACTIVITY TIED STRONGLY TO DAYTIME HEATING.

AS I`M PRESENTED WITH A SCENARIO NOT MUCH DIFFERENT FROM THE
PREVIOUS SHIFT...OPTED TO MAKE ONLY THE SLIGHTEST CHANGES IN
TEMPERATURES FOR TONIGHT AND TOMORROW. LOWER DEWPOINTS AND
SIGNIFICANTLY COOLER 850 MB TEMPERATURES STRONGLY IMPLY
TEMPERATURES WELL BELOW THE LEVELS EXPERIENCED THE LAST FEW
DAYS. INDEED...TONIGHT`S LOWS UNDERCUT ALL GUIDANCE...AND MY
CONCERN IS STILL IF I`VE GONE LOW ENOUGH. DID CHOOSE TO BUMP UP
HIGHS A BIT IN THE SOUTH TOMORROW WHERE CLOUD COVER IS EXPECTED TO
BE LESS...AS SUNNY AREAS TODAY BURST THROUGH THEIR FORECAST HIGHS
RATHER EASILY. STILL...THE CHANGES ARE LARGELY COSMETIC.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY
ISSUED AT 253 PM CDT MON AUG 3 2015

THE 500MB FORECAST OF THE MEDIUM RANGE MODELS LOOK
PRETTY SIMILAR OVERALL BUT THERE ARE SUBTLE DIFFERENCES IN THE
FLOW ALOFT THAT HAS LARGER IMPLICATIONS IN THE WEATHER AT THE
SURFACE. THERE IS GOOD AGREEMENT THAT NORTHWEST UPPER FLOW AND
A SURFACE HIGH TO OUR NORTHEAST WILL KEEP DRY WEATHER ACROSS
WISCONSIN THROUGH WEDNESDAY.

JET ENERGY ROUNDING THE UPPER RIDGE OVER THE ROCKIES IS HANDLED
DIFFERENTLY BY THE MODELS WEDNESDAY NIGHT AND THURSDAY. THE
BIGGEST OUTLIER IS THE GFS WHICH KEEPS A SHARPER TROUGH MOVING
ACROSS THE NORTHERN GREAT LAKES THAN THE OTHER MODELS WHICH TAKE
MORE OF IT TO THE SOUTH. AS A RESULT THE GFS HAS A SIGNIFICANT
SURFACE LOW THAT MOVES ACROSS NORTHERN ILLINOIS AND BRINGS
SUBSTANTIAL RAIN TO THE FORECAST AREA WEDNESDAY NIGHT AND
THURSDAY. NOT SURE WHICH IS CORRECT BUT WE HAVE BEEN IN A VERY DRY
PATTERN FOR THE PAST FEW MONTHS SO WILL KEEP THINGS MAINLY DRY.

DIFFERENCES IN THE UPPER PATTERN ARE AGAIN IN PLAY THURSDAY NIGHT
AND FRIDAY WHEN THE ECMWF HAS A SHARPER UPPER TROUGH MOVING ACROSS
OUR AREA THAN THE GFS AND ALSO GENERATES MORE PRECIPITATION THAN THE
GFS. BECAUSE OF THE SUBSTANTIAL MODEL DIFFERENCES WE MADE NO
CHANGES TO EARLIER FORECASTS FOR THOSE DAYS. ADDITIONAL MODEL
DIFFERENCES CONTINUE FRIDAY THROUGH EARLY NEXT WEEK...SO HAVE
LITTLE CONFIDENCE IN THAT PERIOD. THE NEAR ABSENCE OF ANY GULF
MOISTURE SUGGESTS THAT THIS WEEK WILL BE GENERALLY DRY AND EVEN IF
IT RAINS IT SHOULD BE LIGHT.

TEMPERATURES SHOULD BE ABOUT FIVE DEGREES BELOW NORMAL THROUGH
THURSDAY AND NEAR NORMAL AFTER THAT.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 100 PM CDT MON AUG 3 2015

AN UPPER LEVEL DISTURBANCE LOOKS TO PRODUCE SCATTERED SHOWERS
OVER NORTHERN WISCONSIN DURING THE AFTERNOON AND EARLY
EVENING...ACCOMPANIED BY BKN STRATOCUMULUS. COVERAGE OF PRECIP IS
EXPECTED TO BE RELATIVELY LOW...SO WILL CONTINUE TO REFRAIN FROM
BRINGING IN RAIN TO THE RHI TAF FOR NOW. IF AFTERNOON COVERAGE IS
GREATER THAN EXPECTED...THIS MAY REQUIRE A CHANGE. WEST-
NORTHWEST WINDS WILL GUST TO 15 TO 20 KTS DURING THE LATE MORNING
AND AFTERNOON HOURS...THEN BECOME LIGHT OVERNIGHT. EXPECT SOME
REBOUND AGAIN TOMORROW MORNING INTO THE EARLY AFTERNOON...BUT NOT
NEARLY AS GUSTY AS TODAY.
&&

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

$$

SHORT TERM.....LUCHS
LONG TERM......RDM
AVIATION.......LUCHS


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