CONVECTIVE FORECAST
VALID 06Z WED 28/05 - 06Z THU 29/05 2003
ISSUED: 27/05 17:49Z
FORECASTER: DAHL

GENERAL THUNDERSTORMS ARE FORECAST ACROSS EASTERN ... CENTRAL AND SOUTHERN EUROPE.

SYNOPSIS

UPPER FLOW PATTERN WILL UNDERGO ONLY MINOR CHANGES COMPARED TO TODAY DURING THE PERIOD ... PRIMARY DIFFERENCE WILL BE EASTWARD PROGRESSION/STRENGTHENING OF THE UPPER LOW ATTM OVER THE SW MEDITERRANEAN SEA. WEAKLY CAPPED LOW-LEVEL AIRMASS WITH MLCAPES ON THE ORDER OF 1000 TO 1500 J/KG IS PRESENT ACROSS EASTERN AND SOUTHERN PARTS OF EUROPE ... AND IS ADVECTED EAST INTO FRANCE AT THE S FLANK OF BUILDING CENTRAL EUROPEAN HIGH PRESSURE AREA.

DISCUSSION

...EASTERN AND CENTRAL EUROPE...
CONVECTIVE SCENARIO SHOULD NOT DIFFER MUCH FRON TODAY'S ... EXCEPT THAT ACTIVITY WILL LIKELY SPREAD FARTHER WEST INTO FRANCE. GIVEN WEAK CAPPING ... STORMS SHOULD INITIATE AT OROGRAPHIC FEATURES AND ALONG GUST FRONTS LAID OUT BY TODAY'S CONVECTION DURING EARLY AFTERNOON. 12Z LRBS SOUNDING INDICATES 600 HPA FLOW OF 45 KTS WHICH APPEARS TO BE ASSOCIATED WITH THE WEAK SW EUROPEAN UPPER LOW/EMBEDDED VORT MAX. POSITION OF THIS FEATURE IS VERY POORLY PREDICTABLE WITH THE DATA AT HAND ... BUT IF WEDNESDAY MORNING SOUNDINGS STILL SUGGEST EXISTENCE OF THIS FEATURE ... LOCALIZED THREAT FOR ROTATING UPDRAFTS WOULD EXIST. HOWEVER ... MAJORITY OF THE STORMS WILL LIKELY BE SUB-SEVERE GIVEN WEAK SHEAR AND WEAK FORCING. TSTMS SHOULD MERGE LATE IN THE DAY INTO SEVERAL LARGER CLUSTERS WHICH SHOULD PRIMARILY PRODUCE LARGE AMOUNTS OF RAIN ... THOUGH ISOLATED MARGINALLY SEVERE HAIL EVENTS MAY OCCUR. ALSO ... STORMS SHOULD BE ABLE TO PRODUCE STRONG DOWNDRAFTS GIVEN RATHER DRY AND DEEP SUB-CLOUD LAYERS. SINCE ORGANIZED SEVERE STORMS ARE NOT EXPECTED ATTM ... A SLIGHT RISK IS NOT NECESSARY.

...SOUTH CENTRAL MEDITERRANEAN...
STRONG DCVA-RELATED ASCENT WILL OVERSPREAD THE S-CENTRAL MEDITERRANEAN AHEAD OF THE UPPER LOW. PLUME OF ELEVATED MIXED SAHARA AIRMASS IS EXPECTED TO ADVECT NORTHWARD E OF THIS FEATURE ... AND WILL CONTRIBUTE TO FAVORABLE THERMODYNAMIC PROFILES OVER THIS REGION. LOW-LEVEL MOISTURE IS STILL IN QUESTION SINCE MOISTURE APPEARS TO BE QUITE SHALLOW DESPITE THE PRESENCE OF RELATIVELY WARM SEA WATERS. IF SUFFICIENT CAPE DOES EVOLVE DURING THE DAY ... PRESENCE OF STRONG UPWARD FORCING AND STRONG SHEAR WILL PROMOTE ORGANIZED SEVERE THUNDERSTORM THREAT WITH LARGE HAIL, SEVERE WIND GUSTS AND POSSIBLY A TORNADO OR TWO. EXPECT AN UPGRADE TO SLIGHT RISK IN CASE ADEQUATE THERMODYNAMIC PROFILES EVOLVE DURING THE DAY.

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