223 FXUS63 KLBF 221802 AFDLBF AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTH PLATTE NE 102 PM CDT TUE MAY 22 2012 .AVIATION... /FOR 22.18Z TAF ISSUANCE/ WINDS...TIMING OF FRONTAL PASSAGE...AND CHANCES FOR THUNDERSTORMS ARE HIGHLIGHTS OF AVIATION FORECAST TODAY. WINDY SOUTHERLY CONDITIONS WILL CONTINUE INTO TONIGHT AS A COLD FRONT PUSHES TOWARDS THE AREA. THE STRONGEST SUSTAINED WINDS OF 25 TO 35 KTS ARE EXPECTED EAST OF A LINE FROM KVTN TO KLXN...HOWEVER LOCATIONS TO THE WEST WILL ALSO EXPERIENCE STRONG WINDS. THERE IS POTENTIAL FOR LOW LEVEL WIND SHEAR TONIGHT AS THE LOW LEVEL JET PICS UP. SOUNDINGS FROM THE RAPID REFRESH SHOWING 60 TO 65 KT WINDS FROM THE SOUTH AROUND 2K FEET ABOVE THE GROUND. DIDN/T ADD ANY LLWS IN THE TAF AT THIS POINT DUE TO QUESTIONS ON HOW STRONG SURFACE WINDS WILL STAY BUT IF THEY DROP OFF...BEST WINDOW FOR LLWS LOOKS TO BE 01Z TO 07Z. AS FOR THUNDERSTORMS...BETTER DYNAMICS FOR CONVECTION ARE UP INTO THE DAKOTAS TONIGHT BUT COULD SEE SOME ISOLATED STORMS OVER SOUTHERN NEBRASKA AND ISOLATED TO SCATTERED STORMS OVER NORTHERN NEBRASKA. NOT HIGH CONFIDENCE ON THE COVERAGE THOUGH SO JUST PUT VCTS AT KVTN AND LEFT KLBF DRY FOR NOW. WILL MONITOR FOR DEVELOPMENT AND WILL AMEND AS NECESSARY AS THINGS COME TOGETHER. RIGHT NOW TIMING LOOKS TO BE LATE AFTERNOON TO EARLY EVENING IF STORMS TO IMPACT THESE LOCATIONS. THE COLD FRONT WILL COME ACROSS THE AREA LATE TONIGHT WITH WINDS SWITCHING TO THE NORTH TO NORTHWEST AND STAYING BREEZY INTO THE AFTERNOON. && .PREV DISCUSSION... /ISSUED 1020 AM CDT TUE MAY 22 2012/ UPDATE... EARLY MORNING THUNDERSTORMS ACROSS PORTIONS OF NORTH CENTRAL NEBRASKA HAVE DISSIPATED AS LARGE SCALE SUBSIDENCE BEGINS TO DOMINATE THE AREA FOR THE NEXT FEW HOURS. FORECAST UPDATED TO REFLECT THIS...BUT ORIGINAL FORECAST HAD THIS DEPICTED QUITE WELL. OTHERWISE HIGHLIGHTS STILL REMAIN FOR WINDS ACROSS MAINLY CENTRAL AND NORTH CENTRAL NEBRASKA...AND RED FLAG WARNING FOR ZONE 204 IN THE PANHANDLE. THESE HIGHLIGHTS STILL LOOK GOOD FOR BOTH AREAS. ATTENTION WILL ALSO SHIFT TO DRYLINE ACROSS THE PANHANDLE WHICH IS EXPECTED TO BE LOCATED FROM ABOUT MERRIMAN TO BIG SPRINGS BY LATE AFTERNOON. DEW POINT GRADIENT IS EXPECTED TO TIGHTEN SIGNIFICANTLY DURING THE AFTERNOON AS LOW DEEPENS IN THE PANHANDLE AND CORRESPONDING WINDS AHEAD OF THE DRYLINE INCREASE. AS THIS TIGHTENING OCCURS...LOW LEVEL CIRCULATION ASSOCIATED WITH THE BOUNDARY SHOULD DEEPEN WHICH SHOULD ALLOW ISOLATED CONVECTION TO DEVELOP ALONG IT. FORECAST SOUNDINGS WEST OF THE DRYLINE HAVE A INVERTED V PROFILE WHICH SHOULD SUPPORT THE POTENTIAL FOR SEVERE WIND GUSTS AS WELL AS HAIL...AND DRY LIGHTNING IS A CONCERN AS WELL INITIALLY. FORECAST SOUNDING PROFILES JUST EAST OF THE DRYLINE...NEAR MERRIMAN FOR EXAMPLE...SHOW SIMILAR LOWER LAYERS BUT ALSO SHOW DECENT CAPE IN THE HAIL PRODUCTION LAYER SO WOULD EXPECT SLIGHTLY BETTER POTENTIAL FOR HAIL THERE. EAST OF THE DRYLINE...CAP LOOKS TO BE STRONG ENOUGH TO INHIBIT THUNDERSTORM DEVELOPMENT INITIALLY...BUT WILL HAVE TO WATCH FOR POTENTIAL FOR STORMS TO MOVE INTO THE AREA THIS EVENING. PREV DISCUSSION... /ISSUED 409 AM CDT TUE MAY 22 2012/ SYNOPSIS... STRONG SURFACE HIGH PRESSURE DOMINATES THE MID MISS RVR VALLEY...WHILE LOW PRESSURE TROUGH ALONG THE EASTERN ROCKIES. UPPER LEVEL DISTURBANCE CONTINUES TO MOVE ACROSS THE CENTER PART OF THE STATE...WITH NARROW BAND OF SHOWERS WITH AN OCCASIONAL LIGHTNING STRIKE. WINDS...DUE TO PRESSURE TIGHT GRADIENT...HAVE REMAINED UP SO FAR...WITH TEMPS STILL IN THE UPPER 50S TO LOWER 60S. DISCUSSION... DISTURBANCE SLOWLY PUSHES EAST WITH A FEW SHOWERS POSSIBLY LINGERING THE NEXT FEW HOURS...BEFORE DISSIPATING. TIGHT PRESSURE GRADIENT CONTINUES WITH MIXING MOST OF THE 850 MB WINDS...35 KTS OVER N CENTRAL NEB...FOR THE AFTERNOON. WIND ADVISORY CONTINUED...HOWEVER STILL WINDY CONDITIONS OVER THE WEST...BUT SHOULD REMAIN JUST BELOW CRITERIA. DRY LINE WILL DEVELOP/INTENSIFY OVER THE WEST FOR THE AFTERNOON. VERY DRY AIR WILL BE WEST OF THE LINE...WITH FIRE WEATHER CONCERNS OVER THE PANHANDLE. HIGHS TODAY SHOULD EASILY PUSH INTO THE 80S AND LOW 90S WITH THE STRONG S WINDS AHEAD OF AN APPROACHING COLD FRONT. DRY LINE WILL AGAIN BE THE FOCUS FOR THUNDERSTORM DEVELOPMENT LATE THIS AFTERNOON. QUESTION IS WHETHER CAP WILL HOLD. MODELS DEVELOP NARROW BAND OF CAPE VALUES IN EXCESS OF 3000 J/KG ALONG THE DRY LINE. STEEP MID LEVEL LAPSE RATES AND SHEAR SHOULD BE STRONG ENOUGH TO SUSTAIN ANY DEVELOPMENT...WITH SEVERE WEATHER POSSIBLE...MAINLY LARGE HAIL AND POSSIBLY SOME WINDS. ACTIVITY WILL MOVE EAST OVERNIGHT WITH A COLD FRONT PUSH ACROSS THE AREA OVERNIGHT. THIS WILL DROP TEMPS CONSIDERABLY FOR WEDNESDAY...WITH HIGHS GENERALLY IN THE 70S. UPPER LEVEL DISTURBANCE FOLLOWS THE COLD FRONT AND SHOULD SEE AN AREA OF SHOWERS DEVELOP. KEPT MENTION OF THUNDER WITH IT BEING LATE MAY AND IN THE AFTERNOON...HOWEVER INSTABILITY IS MARGINAL AT BEST...WITH LI/S POSITIVE. OVERALL UPPER LEVEL PATTERN WILL THEN TRANSITION FROM RIDGE IN THE WEST TO A BROAD TROUGH...WITH THE RIDGE ALONG THE EAST COAST. SEVERAL LOWS WILL HELP TO DIG TROUGH OVER THE WEST...WHILE A CLOSED HIGH DEVELOPS OVER THE SOUTHEAST CONUS. SOUTHWEST FLOW DEVELOPS WITH SEVERAL WAVES TO MOVE ACROSS THE AREA. SHOULD HELP TO KEEP CLOUDS AND COOLER TEMPS ACROSS THE REGION FOR THURSDAY. MODELS TRACK THE STRONGEST WAVE ACROSS THE AREA WED NIGHT...WITH LIKELY POPS CONTINUED. AS THE TROUGH DIGS IN THE WEST...WEAK RIDGING LATE IN THE WEEK AND INTO THE FIRST PART OF THE HOLIDAY WEEKEND WILL HELP TO PUSH TEMPS UP. MODELS HAVING GREAT DIFFICULTY WITH THE PLACEMENT OF THE RIDGE/TROUGH TRANSITION ACROSS THE AREA. THIS RESULTS IN A LARGE MARGIN BETWEEN MODELS. ACTIVE WEATHER AND POSSIBLE CLOUD COVER ALSO MAKES THE FORECAST DIFFICULT. ECMWF IS THE STRONGEST AND FURTHER WEST WITH THE HIGH OVER SOUTHEAST FOR THE WEEKEND. 850 MB TEMPS PUSH BACK INTO THE MID 20S...SUGGESTING HIGHS WELL INTO THE 80S. HOWEVER THE LATEST RUN OF THE GFS PUSHED THE HIGH FURTHER EAST...ESPECIALLY FOR SUNDAY...WITH 850 MB TEMPS ONLY IN THE MID TEENS FOR SATURDAY AND MUCH COOLER FOR SUNDAY. RESULTING TEMPS AT THE SURFACE ARE MORE THAN 20 DEGREES DIFFERENCE WITH THE LATEST MEX GUIDANCE IN THE 60S FOR HIGHS ON SUNDAY. DID TREND THE FORECAST SLIGHTLY COOLER...HOWEVER WILL WAIT FOR BETTER AGREEMENT BEFORE MAKING LARGE ADJUSTMENTS. FIRE WEATHER... WILL BE HOISTING A RED FLAG WARNING FOR ZONE NEZ204 FOR THIS AFTERNOON AND EARLY THIS EVENING...IN PARTICULAR...WESTERN PORTIONS OF THIS ZONE INCLUDING THE EASTERN NEBRASKA PANHANDLE. A WELL ESTABLISHED DRY LINE WILL BECOME ORIENTED ALONG THE EASTERN PANHANDLE LATER TODAY. WEST OF THIS FEATURE...SFC DEW POINTS WILL DROP INTO THE 30S WITH AIR TEMPERATURES IN THE MID 90S. THIS WILL RESULT IN SEVERAL HOURS OF SUB 15 PERCENT RELATIVE HUMIDITIES. IN ADDITION TO LOW RELATIVE HUMIDITIES...SWRLY WINDS WEST OF THE DRY LINE WILL BE GUSTY WITH THE POTENTIAL FOR GUSTS AS HIGH AS 30 MPH LATER THIS AFTERNOON. ALSO...DRY LIGHTNING CANNOT BE RULED OUT EITHER...AS CONVECTION IS EXPECTED TO FIRE ALONG THE EASTERN EDGE OF THE DRY LINE AROUND 21Z THIS AFTERNOON. THIS CONVECTION WILL BE ELEVATED INITIALLY...DUE TO LIMITED BOUNDARY LAYER MOISTURE. EAST OF THE PANHANDLE...BOUNDARY LAYER MOISTURE WILL INCREASE QUICKLY...LIMITING THE DRY LIGHTNING THREAT...BUT INCREASING THE THREAT FOR LARGE HAIL OR DAMAGING WINDS. && .LBF WATCHES/WARNINGS/ADVISORIES...RED FLAG WARNING UNTIL 8 PM MDT THIS EVENING FOR NEZ204. WIND ADVISORY UNTIL 9 PM CDT /8 PM MDT/ THIS EVENING FOR NEZ005>010-025>029-037-038-094. && $$ DISCUSSION...MASEK UPDATE...JWS AVIATION...BROOKS