
Updated:
3/17/10 6:44pm
Foresthill Weather.com
Welcome
DondelingerPhotography
NATIONAL WEATHER SERVICE FORECAST DISCUSSION
000 FXUS66 KSTO 172218 AFDSTO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SACRAMENTO CA 330 PM PDT WED MAR 17 2010 .DISCUSSION... AREA OF HIGH CLOUDINESS (BASES ~20 KFT ACCORDING TO KDAX VWP) NOW GENERALLY ALONG AND SOUTH OF I-80. THE CLOUDS ARE GENERALLY SOUTH OF THE DEFORMATION OR STRETCHING AXIS LOCATED ACROSS NORCAL...NEWD INTO THE LOW CENTER OVER THE SRN CANADIAN PROVINCES. ALONG THIS DEFORMATION AXIS...WATER VAPOR IMAGERY SHOWS A LITTLE ENHANCEMENT OF MOISTURE ALONG I-80 WHERE IT IS CONCEIVABLE A SPRINKLE/MTN FLURRY MAY OCCUR THROUGH THE EARLY EVENING. OTHERWISE... SKIES WILL BE CLEARING TONIGHT AS THE CLOUDINESS WILL BE SHUNTED SWD BY THE INCOMING SHORT WAVE THAT WILL BE MOVING ACROSS ORE. THIS NRN SHORT WAVE WILL ALSO BE SHUNTING THE INCOMING SHORT WAVE TROF OFF THE SOCAL COAST TO THE S OF NORCAL OVERNITE. THUS...SKIES ARE EXPECTED TO CLEAR OVER THE SRN HALF OF NORCAL OVERNIGHT. IT WAS A SEASONABLY WARM DAY TODAY WITH TEMPS IN THE 70S IN THE VLY...60S TO LOW 70S MOUNTAINS AND LOWER FOOTHILLS...AND 50S HIGHER ELEVATIONS. THESE TEMPS ARE ABOUT 10-15 DEG ABOVE NORMAL...WITH THE POSSIBILITY THAT RDD/RBL MAY TOUCH 80. IT APPEARS IT WILL BE TURNING BREEZIER/WINDIER OVER NORCAL ON THU AND THU NITE INTO FRI AS THE MODELS CONTINUE TO FORECAST THE INTENSIFICATION OF THE TROF/VORT MAX MOVING ACROSS ORE TONIGHT AND SLIDING SSEWD OVER NORCAL ON THU. THIS FEATURE IS SLIDING SEWD ON THE E SIDE OF THE AMPLIFYING RIDGE OFF THE W COAST...AND SW OF THE MAIN LOW SPILLING OVER THE RIDGE FROM B.C. AND FORECAST TO TRACK TOWARDS THE 4-CORNERS. TODAY`S GFS/NAM SHOW THE ORE VORT MAX TRACKING MAINLY OVER THE SIERNEV ON THU...FOLLOWED BY AN AMPLIFYING RIDGE ALONG THE W COAST REACHING NWD TOWARDS THE ARCTIC CIRCLE FOR FRI. SO AFTER SOME INITIAL COOLING ON THU DUE TO THE STRONG MID LEVEL CAA...TEMPS ARE EXPECTED TO REBOUND WELL ABOVE NORMAL ON FRI AND INTO THE WEEKEND. GIVEN THE TRACK OF THE VORT MAX...VERY STRONG MID LEVEL CAA... STRONGER CYCLONIC FLOW AND ALBEIT WEAK UPPER LEVEL DIVERGENCE...WE DO BELIEVE SOME CONVECTION/SHOWERS IS/ARE POSSIBLE OVER THE SIERNEV ON THU. MOISTURE WITH THIS SYSTEM IS EXPECTED TO BE VERY SPARSE WITH ONLY .30 TO .50 INCH PWS AHEAD OF THE VORT MAX/FRONT AND VERY LOW PW AIR /LESS THAN .20 INCH/ ADVECTED SWD ON THU BEHIND THE VORT MAX/ FRONT AND CONTINUING INTO THE WEEKEND. THE VORT MAX MAY BE STRONG ENOUGH TO SQUEEZE OUT SOME LIGHT PCPN OR RESULT IN SOME SMALL... SCATTERED AND RELATIVELY HIGH-BASED STRATOCUMULUS OR ALTOCUMULUS IN THE VALLEY UNTIL FROPA. THE GFS CROSS SECTIONS INDICATE THAT SYNOPTIC SCALE DOWNSLOPE FLOW WILL PREVAIL ON THE W SIDE OF THE SIERNEV ESPECIALLY AFTER TROF/FRONTAL PASSAGE WHICH WILL ALSO PRECLUDE SHOWER DEVELOPMENT IN OUR FORECAST AREA. BELIEVE THE SHOWER ACTIVITY WILL BE CONFINED MORE TO THE CREST AND UNLIKELY TO REACH THE FOOTHILLS. N TO NE PRESSURE GRADIENTS WILL INCREASE BEHIND THE LOW CENTER THU AND INTO FRI MORNING FOR BREEZY/WINDY N TO E WINDS AT TIMES OVER PORTIONS OF OUR FORECAST AREA. THESE WILL BE DRYING/ SUBSIDING WINDS. ALREADY...THE MFR-RDD GRADIENT HAS INCREASED TO OVER 8 MBS AND NLY WINDS SHOULD INCREASE AND BECOME GUSTY AFTER TROF PASSAGE OVER THE NRN MTN ZONES AND NRN SAC VLY BY EARLY THU MORNING. THE NAM 925 MBS WINDS SHOW THE NLY WINDS INCREASING TO OVER 30 KTS IN THE NRN SAC VLY BY THU MORNING...WITH THE CORE OF THE WINDS SPREADING SWD BY MID MORNING. A POSSIBLE NLY BARRIER JET EVENT IS SHAPING UP THU NITE AND FRI MORNING AS PRESSURES RISE OVER THE GREAT BASIN IN THE WAKE OF THE VORT MAX. AT THIS TIME...IT LOOKS LIKE A 50/50 CHANCE THAT WIND ADVSRY CRITERIA WILL BE REACHED IN THE CENTRAL AND SRN SAC VLY...MAINLY ALONG AND W OF I-5 ON THU AS THE NLY WINDS DEVELOP AND WORK SWD. THE 35 KT SPEED MAX AT 925 MBS IS RIGHT AT THE CUSP OF THE 40 MPH MINIMUM GUST CRITERIA. WE WILL BE MONITORING THIS FOR A POSSIBLE WIND ADVSRY IN UPCOMING FORECAST PACKAGES. AS THIS SYSTEM PHASES WITH THE MAIN LOW HEADING TOWARDS THE 4 CORNERS...A HIGHLY AMPLIFIED RIDGE WILL DEVELOP ALONG THE COAST AND EXTENDING WELL NWD TOWARDS THE ARCTIC CIRCLE ON FRI. LOOKS AS IF THIS RIDGE WILL DOMINATE OUR WX THROUGH THE WEEKEND...THEN BREAKING DOWN EARLY NEXT WEEK. MAX TEMPS ARE FORECAST TO BE 10-15 DEG ABOVE NORMAL FOR FRI AND INTO THE WEEKEND...BEFORE COOLING TO NORMAL EARLY IN THE WEEK. JHM .EXTENDED DISCUSSION (SUNDAY THROUGH WEDNESDAY)... UPPER RIDGE SHIFTS EAST SUNDAY ALLOWING A WEAK PACIFIC FRONT AND ASSOCIATED UPPER TROUGH TO MOVE THROUGH INTERIOR NORTHERN CALIFORNIA EARLY NEXT WEEK. MODELS DIFFER ON TRACK/TIMING AND AMOUNT OF ASSOCIATED PRECIP BUT MAIN THEME APPEARS TO BE A SLIGHT CHANCE OF SHOWERS OVER THE COASTAL AND NORTHERN INTERIOR MOUNTAINS AND WEST SLOPES OF THE SIERRA NEVADA MONDAY INTO TUESDAY MORNING. MORE SIGNIFICANT EFFECTS LIKELY TO BE COOLING MON/TUE WITH BREEZY NORTHERLY WIND. UPPER RIDGE MOVES OVER INTERIOR NORCAL WEDNESDAY WITH MINOR WARMING AND LESS WIND. && .AVIATION... VFR CONDS CONTINUE. PRIMARY AVN CONCERN WILL BE STRONG SURFACE WINDS FOR MUCH OF THURSDAY INTO FRIDAY. NORTHERLY WINDS WILL START TO STRENGTHEN AFT 12Z FOR THE NRN SAC VLY AND ADJACENT FOOTHILLS WITH DOWNSLOPE FLOW...PEAKING BTWN 16-22Z WITH SUSTAINED WINDS 13-18 KTS...GUSTS 20-30 KTS. LLWS POSSIBLE FOR KRDD/KRBL APPROX 12-18Z. ENHANCED WINDS WILL SPREAD INTO THE REST OF THE SAC VLY AFT 18Z THOUGH NOT AS STRONG...SUSTAINED WINDS UP TO 15 KTS AND LCL GUSTS POSSIBLE UP TO 20 KTS. WINDS WILL LESSEN VALLEY WIDE NEAR 02Z. STRONG EAST TO NORTHEASTERLY RIDGETOP WINDS WILL BEGIN 22Z WITH WINDS UP TO 40 KTS...WINDS GETTING STRONGER AND PEAK EXPECTED BTWN 02-10Z FRIDAY. WINDS ALF BACKING TO NRLY AROUND 06Z. JBB && .STO WATCHES/WARNINGS/ADVISORIES...NONE. && $$
Top
Contact
Website Map
Copyright © 2009 Foresthillweather.com
Never base important decisions on this or any weather information obtained from the Internet



