000
FXUS63 KGRB 171718
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1218 PM CDT THU APR 17 2014

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND FRIDAY
ISSUED AT 351 AM CDT THU APR 17 2014

CHANGES TO PCPN TRENDS AND WINTER WEATHER HEADLINES THIS MORNING
ARE THE MAIN FCST CONCERNS.

IMPRESSIVE DEFORMATION ZONE WAS MOVG ACROSS THE NW HALF OF WI EARLY
THIS MORNING...WITH THE ENHANCED SOUTHERN EDGE ALIGNED FROM ABOUT
MERRILL TO IRON MOUNTAIN. POCKETS OF MODERATE TO HEAVY SNOW HAVE
DEVELOPED OVER NC WI DURING THE PAST HOUR. PCPN WAS FINALLY WORKING
ITS WAY INTO EASTERN WI...AS STRONG DYNAMICS ASSOCIATED WITH A
NEGATIVELY-TILTED S/W TROF...UPPER DIVG...FGEN FORCING AND WAA
ARRIVED. PCPN TYPE WAS SNOW NORTH OF A LINE FROM AUW-MNM...WITH
MAINLY RAIN OVER C/EC WI.

EXPECT MODERATE TO HEAVY SNOW TO CONTINUE NW OF A LINE FROM RRL-IMT
THROUGH ABOUT 13Z-14Z...AND THIS SUPPORTS A CONTINUATION OF THE
CURRENT ADVISORY/WARNING HEADLINES. HOWEVER...TEMP/RH/OMEGA
TIMESECTIONS SHOW THAT THE SNOW SHOULD QUICKLY TAPER OFF OVER
NORTHERN WI DURING THE 14Z-16Z PERIOD...AND SHOULD ACTUALLY CHANGE
OVER TO RAIN OR DRIZZLE AS MOISTURE SHALLOWS OUT...RESULTING IN
A LACK OF ICE CRYSTALS IN THE REMAINING SATURATED LAYER. SFC
TEMPS SHOULD BE AT OR A LITTLE ABOVE FREEZING BY THEN...SO DON`T
ANTICIPATE ANY SIGNIFICANT ICING ISSUES. WITH THESE TRENDS IN
MIND...WILL CHANGE THE EXPIRATION TIME OF THE HEADLINES TO 11 AM...
AND THE DAY SHIFT MAY EVEN BE ABLE TO CANCEL THEM A LITTLE
EARLIER.

LINGERING LIGHT RAIN OR DRIZZLE WILL PULL OUT OF FAR NE WI DURING
THE EARLY AFTERNOON...FOLLOWED BY GENERALLY DRY CONDITIONS FOR
THE REST OF THIS AFTERNOON...TONIGHT AND FRIDAY. WILL NEED TO KEEP
AN EYE ON FRIDAY THOUGH...AS THE LFQ OF A JET STREAK AND A S/W TROF
WILL MOVE THROUGH FAR NE WI DURING THE DAY.

USED A BLEND OF THE BETTER PERFORMING GUIDANCE SETS FOR MAX/MIN
TEMPS THE NEXT COUPLE DAYS. MADE SOME MINOR DOWNWARD ADJUSTMENTS
OVER THE SNOW COVERED NORTHWOODS...AND SLIGHT UPWARD ADJUSTMENTS
OVER C/EC WI. BELOW NORMAL TEMPS WILL CONTINUE.

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY
ISSUED AT 351 AM CDT THU APR 17 2014

MEDIUM RANGE MODELS ARE IN DECENT AGREEMENT THROUGH THE LONGER TERM
PERIOD WITH ONLY SLIGHT DIFFERENCES IN TIMING OF PRECIP THIS
WEEKEND.  A BLEND OF THE GFS AND ECMWF SHOULD SUFFICE.

FRIDAY NIGHT THROUGH SATURDAY NIGHT...A SURFACE RIDGE AXIS WILL BE
OVERHEAD AT THE START OF FRIDAY EVENING...BUT THEN WILL SHIFT
TOWARDS THE CENTRAL GREAT LAKES OVERNIGHT.  SHOULD SEE TEMPS FALL
QUICKLY OVER N-C WISCONSIN WHERE CLEAR SKIES AND FRESH SNOW COVER
WILL ALLOW FOR GOOD RADIATIONAL COOLING CONDITIONS.  BUT THE
GRADIENT WILL TIGHTEN LATE ALONG WITH MID AND HIGH CLOUDS ARRIVING
WHICH SHOULD CAUSE TEMPS TO REBOUND.  WILL TRY TO SHOW THIS TREND IN
THE GRIDS.  THEN RETURN FLOW RAMPS UP ON SATURDAY AHEAD OF SHORTWAVE
ENERGY MOVING ACROSS SOUTH-CENTRAL CANADA. INCOMING MID-LEVEL THETAE
AXIS AND MID-LEVEL FGEN WILL CREATE AN INCREASING CHANCE OF
SHOWERS...MAINLY DURING SATURDAY AFTERNOON.  LOWER CONDENSATION
PRESSURE DEFICITS POINT TOWARDS NORTHERN WISCONSIN HAVING A BETTER
CHANCE THAN ELSEWHERE...WHICH IS ALSO SUPPORTED BY DRY SOUTHEAST
SURFACE FLOW.  THIS THETAE AXIS ALONG A DECAYING COOL FRONT WILL
THEN SAG ACROSS THE REST OF THE AREA SATURDAY NIGHT.  SEEMS LIKE A
DECENT CHANCE FOR RAIN EVERYWHERE WITH PWATS INCREASING TO 1.25
INCHES.  PREVIOUS SHIFT ALREADY INCREASED POPS SUBSTANTIALLY...AND
THIS LOOKS GOOD.

REST OF THE FORECAST...THE FRONT WILL SLOWLY SAG SOUTH ON SUNDAY BUT
STILL IMPACT THE SOUTHEAST HALF OF THE FORECAST AREA WITH LIGHT
RAIN.  WILL INCREASE POPS OVER EAST-CENTRAL WISCONSIN.  LIGHT RAIN
COULD POTENTIALLY LINGER INTO MONDAY OVER EAST-CENTRAL WISCONSIN
BEFORE THE FRONT FINALLY IS PUSHED SOUTHEAST OF THE REGION.  THEN
DRY AND SEASONABLE CONDITIONS UNTIL THE NEXT CHANCE OF RAIN ARRIVES
NEXT WEDNESDAY.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1217 PM CDT THU APR 17 2014

WEAKENING SYSTEM CENTERED OVER E-CNTRL WI TO CONT MOVING E-NE
INTO NRN LWR MI BY THIS EVENING AND INTO SE CANADA OVRNGT. PCPN
HAS ENDED OVER NE WI...HOWEVER PLENTY OF IFR/MVFR CIGS REMAIN
ALONG WITH SOME PATCHY FOG OVER NRN WI. SUCKER HOLE IN THE CLOUDS
OVER ERN WI WL GRADUALLY FILL WITH MORE CLOUDS...SO M0STLY CLOUDY
SKIES EXPECTED INTO EARLY EVENING. HI PRES IS FCST TO BUILD INTO
WI TNGT...THUS WE SHOULD SEE CLOUDS DISSIPATE FOR A TIME WITH VFR
CONDITIONS RETURNING. EXCEPTION COULD BE AT THE RHI TAF SITE WHERE
PATCHY FOG MAY REFORM AND SEND VSBYS BACK TO MVFR CONDITIONS. THE
SFC HI TO THEN MOVE ACROSS WI ON FRI WITH MAINLY MID/HI CLOUDS
EXPECTED AS WARMER AIR ATTEMPTS TO RETURN TO THE REGION.
&&

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

$$

SHORT TERM.....KIECKBUSCH
LONG TERM......MPC
AVIATION.......KALLAS