Storm Forecast
Valid: Fri 16 Jun 2006 06:00 to Sat 17 Jun 2006 06:00 UTC
Issued: Thu 15 Jun 2006 16:25
Forecaster: (LAST NAME)

SYNOPSIS

Very warm and humid conditions will prevail over Europe during the forecast period and set the stage for favorable conditions for widespread TSTM development.
Upper-levels display a pretty disturbed pattern with two weakening troughs ( one over Spain and Portugal and another one over eastern Europe )... Parts of central Europe will be influenced by a small-scale upper-level disturbance which should slowy shift towards the east.
Hot and dry conditions will continue over the Mediterranean ( mainly the central and eastern part) and no significant TSTM development is ecpected.

DISCUSSION

....Portugal and Spain....

Main difference, compared to yesterday, will be the orientation of the trough axis.... Strong subtropical jet streak will help to slowly shift this axis more towards the east ( in a more neutral position ) .... Cooler mid-level airmass will spread eastward over the area of interest and should help for widespread instability release.
Prolonged period of upward vertical velocity fields and a pretty uncapped environment will be conducive for scattered TSTM development as early as the morning hours which should diminish insolation,influx of somewhat drier air from the west and slightly weakening mid-level lapse rates should cause a decline in instability release compared to yesterday....
Main area of interest will be eastern Spain, where enhanced DLS and modest instability release could pose a risk for a few organized storms with an attendant large hail and severe wind gust threat.
I did not include areas further towards the east in the level 1 area, because of a continuous offshore-flow of dry continental air... If storms indeed tend to develop ( models indicate this chance during the evening hours) an upgrade may become necessary due to enhanced DLS ( /severe wind gust risk / ).

Another area of interest will be NNE Spain and extreme SW France.... Upper-level flow becomes increasingly diffluent as wind field diminishes and this combined with high divergence values, due to the left exit of the approaching jet, will be fine for a period of enhanced TSTM development during the evening hours... Main threat would be an increasing flash flood threat due to slow storm motion/storm clustering.

....S-France, parts of Switzerland and Austria, and Croatia....

Moderately steepened lapse rates, a warm and humid boundary layer and strong insolation should yield a favorable environment for moderate to locally high instability release ( up to 1000 J/kg SBCAPE).
Focus for storm development will be a slowly southward shifting wind shift zone/ frontal boundary.
Due to a quite weak wind field (DLS ~ 10m/s), expected pulsating storm mode should prohibit a more pronounced severe weather theat, but included this area in a level 1 due to an enhanced larger hail risk with each storm, which can take advantage of those high instability values.
By degrees, storms should cluster and an enhanced flash flood threat can be expected.

Beside NW Switzerland, instability values should decrease further towards the east ( S/CNTRL/E - Switzerland and W-Austria ) but lapse rates will be still steep enough for at least low-end instability release.... Expect diurnal driven TSTM activity with an isolated large hail risk, when storms mature.

Another area of an enhanced hail risk looks like to be over S-Austria and further towards the south...Despite a weak wind field, pulsating storms should pose a large hail risk due to 700-1000 J/kg instability release.

...Germany,NW Switzerland, the Czech Republic and extreme western Poland....

A small-scale upper-level disturbance should reach NW Germany during the morning hours and is forecast to shift slowly towards the east...Development of a broad 10-12g/kg mixing ration belt from NW Switzerland towards NE Germany in front of a slowly eastward shifting confluence zone looks reasonable ATM and this, combined with strong insolation should help to disequilibrate the level 1 area.
DLS in the order of 10-15m/s over NW Switzerland, S-Germany the Czech Republic and extreme western Poland will be present and again.....each pulsating storm could pose a hail risk, matching the severe criteria .

Wind field tends to increase over E and NE-Germany with 15-20m/s DLS and a few organized storms should develop... If indeed that much instability can be realized,what models indicate, an upgrade of his area to a level-2 could become necessary due to the possibility of isolated extremely large hail ( >5cm).

....Eastern Europe...

Cool mid-levels under the base of a weakening upper-level trough and strong insolation will produce a broad sector of instability release, but drier air and weak wind shear should preclude an organized severe TSTM threat... Main risk looks like to be a marginal hail risk.