918  
FXUS66 KMTR 050550  
AFDMTR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN FRANCISCO CA  
950 PM PST TUE FEB 4 2025  
   
..NEW AVIATION, MARINE  
 
   
SYNOPSIS  
 
ISSUED AT 1202 AM PST TUE FEB 4 2025  
 
AN ATMOSPHERIC RIVER WILL CONTINUE TO BRING HEAVY RAIN, URBAN AND  
RIVER FLOODING, AND STRONG WINDS TO THE BAY AREA AND CENTRAL  
COAST THROUGH TUESDAY. THERE IS ALSO AN INCREASING CHANCE FOR  
THUNDERSTORMS IN THE AFTERNOON. WHILE LESS IMPACTFUL IN THE  
SECOND HALF OF THE WEEK, RAIN CHANCES CONTINUE THROUGH FRIDAY.  
 
 
   
SHORT TERM  
 
ISSUED AT 215 PM PST TUE FEB 4 2025  
(THIS EVENING THROUGH WEDNESDAY)  
 
KEY POINTS:  
* FLOOD ADVISORIES AND FLOOD WARNINGS CONTINUES FOR PORTIONS OF  
THE BAY AREA  
* FLOOD WATCH REMAINS EFFECT THROUGH 4 AM WEDNESDAY ACROSS THE  
BAY AREA AND CENTRAL COAST  
* DYNAMIC AFTERNOON/EVENING AS A COLD FRONT BRINGS HEAVY RAIN,  
VERY GUSTY WINDS, AND POSSIBLE THUNDERSTORMS  
* POST FRONTAL COLD TEMPERATURES TONIGHT- N BAY VALLEY FROST  
ADVISORY  
* THUR-FRI AR WILL BRING ANOTHER ROUND OF RAIN WITH RE-NEWED  
FLOODING CONCERNS  
* COLD MORNING TEMPERATURES RETURN MID-WEEK BUT TEMPERATURES  
WILL DROP MORE SIGNIFICANTLY OVER THE WEEKEND  
 
AFTERNOON/EVENING - THE MUCH ANTICIPATED SURFACE LOW, ASSOCIATED  
COLD FRONT, AND ACCOMPANYING UPPER LEVEL JET MAX ARE MAKING THEIR  
PRESENCE KNOWN. SINCE THIS MORNING, RADAR HAS BECOME MUCH MORE  
ACTIVE WITH A LINE INTERMIXED WITH CELLS SHOWING UP ALONG THE  
APPROACHING COLD FRONT. THE WIND FIELD AHEAD OF THE FRONT HAS ALSO  
RAMPED UP WITH A FEW COASTAL SITES SHOWING GUSTS 65-85 MPH. A  
SPECIAL BALLOON SOUNDING WAS LAUNCHED FROM OAK AT 20Z TO FURTHER  
ANALYZE THE ATMOSPHERIC PROFILE, ESPECIALLY THE WIND PROFILE. THE  
BIGGEST CONCERNS THIS AFTERNOON - LOW CAPE HIGH SHEAR ENVIRONMENT  
WILL LEAD TO CONVECTIVELY DRIVEN WIND AND POSSIBLE SPIN UPS WITH  
ANY STRONGER CELL. GIVEN THE JUICY ATMOSPHERE, ANY STRONGER CELL  
HAS SOME DECENT RAINFALL ASSOCIATED WITH IT - 0.5-0.75" PER HOUR.  
THOSE RATES ON ALREADY WET SOIL/FULL CREEKS/STREAMS WILL ADD  
ADDITIONAL FLOODING CONCERNS. SIMPLY PUT, MAKE SURE YOU HAVE WAYS  
TO RECEIVE WEATHER ALERTS WHETHER IT'S FOR SEVERE OR FLOODING.  
ALSO, ALLOW FOR EXTRA TIME DURING THE EVENING AS HEAVY RAIN WILL  
IMPACT THE COMMUTE. DO NOT DRIVE THROUGH FLOODED ROADWAYS.  
 
TONIGHT INTO WEDNESDAY: CONDITIONS WILL GRADUALLY IMPROVE AS THE  
COLD FRONT PUSHES THROUGH THE FORECAST AREA. CONVECTIVE RAIN FROM  
THE EVENING WILL TRANSITION TO SCATTERED SHOWERS N TO S. WHILE  
PRECIP GRADUALLY DIMINISHES IN COVERAGE AND INTENSITY FLOODING  
CONCERNS WILL REMAIN DUE TO FULL CREEKS/STREAMS. WINDS WILL ALSO  
DECREASE BEHIND THE FRONT. SOME CHILLY AIR IS EXPECTED TO FILL IN  
BEHIND THE FRONT WITH DECREASING WINDS AND CLEARING SKIES. AS  
SUCH, A FROST ADVISORY HAS BEEN ISSUED TO CAPTURE TEMPERATURES  
REACHING THE LOW TO MID 30S FOR THE SONOMA VALLEY SPECIFICALLY.  
EVEN IF THE CLOUDS LINGER LONGER AND TEMPERATURES REMAIN IN THE  
MID TO UPPER 30S IT WILL FEEL COLD GIVEN THE DAMP CONDITIONS.  
WEDNESDAY WILL BE A REPRIEVE AS ONE SYSTEM EXITS AND ANOTHER  
APPROACHES FROM THE WEST. GIVEN THE COLDER AIR ALOFT AND UPSTREAM  
UPPER LEVEL TROUGH WIDELY SCATTERED SHOWERS WILL BE POSSIBLE.  
 
 
   
LONG TERM  
 
ISSUED AT 245 PM PST TUE FEB 4 2025  
(WEDNESDAY NIGHT THROUGH NEXT MONDAY)  
 
WEDNESDAY NIGHT WILL BE A LOW CONFIDENCE HIGHER IMPACT POTENTIAL  
FORECAST. A LOT WILL DEPEND UP CLOUD COVER AND IMPACTS FOR  
OVERNIGHT LOWS. FOR NOW, CURRENT FORECAST IS TRENDING COLDER WITH  
WIDESPREAD 30S TO NEAR 40 AND INTERIOR CENTRAL COAST NEAR  
FREEZING. A FROST ADVISORY MAY BEE NEEDED.  
 
THURSDAY AND FRIDAY...ANOTHER AR IS STILL ON TRACK WITH MORE  
MOISTURE TAKING AIM AT THE REGION. THANKFULLY THIS AR LOOKS MUCH  
WEAKER WITH LESS OF A DEEP MOISTURE TAP. EXPECT SHOWER COVERAGE TO  
INCREASE THROUGH THE DAY ON THURSDAY AND LINGER INTO FRIDAY.  
DESPITE A WEAKER SYSTEM FLOODING CONCERNS WILL REMAIN GIVEN HOW  
MUCH RAIN HAS FALLEN OVER THE LAST 24 HOURS. RAINFALL AMOUNTS ARE  
GENERALLY EXPECTED TO BE 0.25-1.00" AND 1.5" COASTAL MTS. AS  
PRECIP BEGINS TO TAPER OFF ON FRIDAY COLDER AIR BEGINS TO MOVE IN  
FROM THE NORTH LOWERING SNOW LEVELS. SOME WET SNOW WILL BE  
POSSIBLE OVER THE HIGHER TERRAIN.  
 
DRIER WEATHER FINALLY RETURNS OVER THE WEEKEND. THE WEATHER  
IMPACTS QUICKLY TURNS TOWARD COLD OVERNIGHT LOWS. WE'RE TALKING  
WIDESPREAD 30S WITH INTERIOR IN THE MID TO UPPER 20S. FROST AND  
FREEZE PRODUCTS WILL LIKELY BE NEEDED.  
 
 
   
AVIATION  
 
(06Z TAFS)  
ISSUED AT 949 PM PST TUE FEB 4 2025  
 
CIGS CONTINUE TO LIFT IN THE POST FRONTAL ENVIRONMENT LEADING TO  
WIDESPREAD VFR IN THE LATE NIGHT FOR ALL BUT THE NORTH BAY WHICH WILL  
SEE SOME POCKETS OF FOG AND MIST. ADDITIONAL SHOWERS MOVE THROUGH THE  
REGION IN THE LATE NIGHT THROUGH THE MORNING FOR THE SF BAY AND  
NORTH BAY TERMINALS. MODERATE WINDS TURN LIGHT OVERNIGHT AND BECOME  
MODERATE AGAIN INTO WEDNESDAY AFTERNOON THEN LIGHT AGAIN THAT NIGHT.  
 
VICINITY OF SFO...VFR THROUGH THE TAF PERIOD. EXPECT GUSTY WINDS TO  
EAST OVERNIGHT AND BECOME LIGHT INTO EARLY WEDNESDAY. SHOWERS PASS  
THROUGH THE AREA IN THE EARLY MORNING BUT EXIT BY THE LATE MORNING.  
MODERATE WEST WINDS ARRIVE FOR WEDNESDAY AFTERNOON BUT BECOME LIGHT  
AND VARIABLE THAT NIGHT.  
 
SFO BRIDGE APPROACH...SIMILAR TO SFO.  
 
MONTEREY BAY TERMINALS...CIGS LIFT INTO THE LATE NIGHT WITH MODERATE  
WINDS WEAKENING INTO WEDNESDAY MORNING. MODERATE WEST WINDS ARRIVE  
WEDNESDAY AFTERNOON BEFORE WEAKENING THAT EVENING.  
 
 
   
MARINE  
 
(TONIGHT THROUGH NEXT MONDAY)  
ISSUED AT 949 PM PST TUE FEB 4 2025  
 
SHOWERS AND STORMS ARE EXITING AS WINDS BEGIN TO EASE. LINGERING  
GUSTY WINDS WILL CAUSE HAZARDOUS CONDITIONS FOR SMALL CRAFT INTO  
EARLY WEDNESDAY FOR MUCH OF THE WATERS, BUT WILL SUBSIDE THROUGH  
THE REST OF THE MORNING. ANOTHER STORM SYSTEM WILL IMPACT THE  
COASTAL WATERS THURSDAY INTO FRIDAY WITH INCREASING WINDS AND  
RAIN.  
 
 
   
HYDROLOGY  
ISSUED AT 1200 PM PST TUE FEB 4 2025  
 
A MOISTURE RICH ATMOSPHERIC RIVER AND ACCOMPANYING SURFACE LOW IS  
BRINGING WIDESPREAD RAINFALL ACROSS THE BAY AREA AND CENTRAL  
COAST. ALREADY PRIMED SOILS AND HIGHER RAIN RATES WILL MAINTAIN  
AN INCREASED POTENTIAL FOR FLOODING ACROSS THE NORTH BAY AND  
COASTAL RANGES TODAY INTO WEDNESDAY. CNRFC HAS INCREASED  
FORECASTED RIVER STAGES ACROSS SEVERAL RIVERS AND STREAMS IN  
RESPONSE TO HIGHER FORECASTED PRECIPITATION. THE LATEST MAIN STEM  
RIVER FORECAST HAS THE RUSSIAN RIVER AT JOHNSONS BEACH AT  
GUERNVILLE (GUEC1) RISING TO ACTION STAGE (29 FT) THIS EVENING AND  
INTO MINOR FLOOD STAGE (32 FT) OVERNIGHT. A FLOOD WARNING IS IN  
EFFECT FOR THIS LOCATION BEGINNING AT 1 AM TONIGHT. IN NAPA COUNTY  
THE NAPA RIVER AT ST HELENA IS FORECAST TO RISE INTO ACTION STAGE  
(16 FT) THIS AFTERNOON AND THE NAPA RIVER NEAR NAPA IS FORECAST  
TO RISE INTO ACTION STAGE (22 FT) TONIGHT.  
 
OTHER NON-MAIN STEM FORECAST POINTS THAT ARE CURRENTLY UNDER A  
FLOOD WARNING INCLUDE...  
 
GEYC1 - RUSSIAN RIVER AT GEYSERVILLE IS CURRENTLY IN MINOR FLOOD  
(>39.7 FT) AND FORECAST TO REMAIN IN MINOR FLOOD THROUGH TONIGHT.  
 
MWEC1 - MARK WEST CREEK AT MIRABEL HEIGHTS IS CURRENTLY IN MINOR  
FLOOD (>55 FT) AND CONTINUING TO RISE. IT IS EXPECTED TO REACH  
MODERATE FLOOD (>59 FT) LATER THIS AFTERNOON.  
 
GRQC1 - GREEN VALLEY CREEK AT MARTINELLI ROAD IS CURRENTLY IN  
MODERATE FLOOD (>63 FT) AND RISING.  
 
CTIC1- LAGUNA DE SANTA ROSA AT STONY POINT ROAD NEAR COTATI IS  
CURRENTLY IN MINOR FLOOD (>84 FT) AND CONTINUING TO RISE. IT IS  
EXPECTED TO REACH MODERATE FLOOD (>85 FT) IN THE NEXT FEW HOURS.  
 
THESE LOCATIONS WILL BE HANDLED THROUGH ONGOING FLOOD  
ADVISORIES.  
 
A FLOOD WATCH WILL REMAIN IN EFFECT THROUGH LATE TONIGHT.  
SEVERAL FLOOD ADVISORIES ARE IN EFFECT THIS AFTERNOON WITH  
NUMEROUS REPORTS OF URBAN AND SMALL STREAM FLOODING ACROSS THE  
NORTHERN HALF OF THE BAY AREA.  
 
 
   
MTR WATCHES/WARNINGS/ADVISORIES  
 
CA...FROST ADVISORY UNTIL 9 AM PST WEDNESDAY FOR CAZ506.  
 
PZ...SMALL CRAFT ADVISORY UNTIL 3 AM PST WEDNESDAY FOR MRY BAY-PIGEON  
PT TO PT PINOS 0-10 NM-PIGEON PT TO PT PINOS 10-60 NM-PT  
ARENA TO PT REYES 0-10 NM-PT ARENA TO PT REYES 10-60 NM-PT  
REYES TO PIGEON PT 0-10 NM-SF BAY N OF BAY BRIDGE.  
 
SMALL CRAFT ADVISORY UNTIL 9 PM PST WEDNESDAY FOR PT PINOS TO PT  
PIEDRAS BLANCAS 0-10 NM.  
 
 
 
 
 
SHORT TERM...MM  
LONG TERM....MM  
AVIATION...MURDOCK  
MARINE...MURDOCK  
 
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